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Sample records for reversible unitized pem

  1. Reversible (unitized) PEM fuel cell devices

    Energy Technology Data Exchange (ETDEWEB)

    Mitlitsky, F; Myers, B; Smith, W F; Weisberg, Molter, T M

    1999-06-01

    Regenerative fuel cells (RFCs) are enabling for many weight-critical portable applications, since the packaged specific energy (>400 Wh/kg) of properly designed lightweight RFC systems is several-fold higher than that of the lightest weight rechargeable batteries. RFC systems can be rapidly refueled (like primary fuel cells), or can be electrically recharged (like secondary batteries) if a refueling infrastructure is not conveniently available. Higher energy capacity systems with higher performance, reduced weight, and freedom from fueling infrastructure are the features that RFCs promise for portable applications. Reversible proton exchange membrane (PEM) fuel cells, also known as unitized regenerative fuel cells (URFCs), or reversible regenerative fuel cells, are RFC systems which use reversible PEM cells, where each cell is capable of operating both as a fuel cell and as an electrolyzer. URFCs further economize portable device weight, volume, and complexity by combining the functions of fuel cells and electrolyzers in the same hardware, generally without any system performance or efficiency reduction. URFCs are being made in many forms, some of which are already small enough to be portable. Lawrence Livermore National Laboratory (LLNL) has worked with industrial partners to design, develop, and demonstrate high performance and high cycle life URFC systems. LLNL is also working with industrial partners to develop breakthroughs in lightweight pressure vessels that are necessary for URFC systems to achieve the specific energy advantages over rechargeable batteries. Proton Energy Systems, Inc. (Proton) is concurrently developing and commercializing URFC systems (UNIGEN' product line), in addition to PEM electrolyzer systems (HOGEN' product line), and primary PEM fuel cell systems. LLNL is constructing demonstration URFC units in order to persuade potential sponsors, often in their own conference rooms, that advanced applications based on URFC s are

  2. Development of integrated DMFC and PEM fuel cell units. Final report; Udvikling af integrerede DMFC og PEM braendselscelle enheder. Slutrapport

    Energy Technology Data Exchange (ETDEWEB)

    Odgaard, M. (IRD Fuel Cell Technology, Svendborg (DK))

    2007-06-15

    The 36-month long project 'Development of integrated DMFC and PEM fuel cell units' has been completed. The project goal was to develop a completely new MEA concept for integrated PEM and DMFC unit cells with enhanced power density and in this way obtain a price reduction. The integrated unit cell consists of a MEA, a gas diffusion layer with flow fields completed with bipolar plates and seals. The main focus of the present project was to: 1) Develop new catalyst materials fabricated by the use of FSD (flame spray deposition method). 2) Optimisation of the state-of-the-art MEA materials and electrode structure. 3) Implementation of a model to account for the CO poisoning of PEM fuel cells. Results and progress obtained in the project established that the individual unit cell components were able to meet and follow the road map of LT-PEM FC regarding electrode catalyst loading and fulfilled the targets for Year 2006. The project has resulted in some important successes. The highlights are as follows: The project has resulted in some important successes. The highlights are as follows: 1) MEA structure knowledge acquired in the project provide a sound basis for further progress. 2) A novel method for the synthesis of electrode by using flame spray synthesis was explored. 3) Electrochemical and catalytic behaviours of catalysts activity for CH{sub 3}OH explored. 4) Implementation of a sub model to account for the CO poisoning of PEM FC has been developed. 5) Numerical study of the flow distribution in FC manifolds was developed and completed with experimental data. 6) The electrode catalyst loading targets for year 2006 achieved. 7) The DMFC MEA performance has been improved by 35%. 8) Optimisation of the MEAs fabrication process has been successfully developed. 9) A new simple flow field design has been designed. 10) A procedure for integrated seals has been developed (au)

  3. Development of an angled Si-PM-based detector unit for positron emission mammography (PEM) system

    Science.gov (United States)

    Nakanishi, Kouhei; Yamamoto, Seiichi

    2016-11-01

    Positron emission mammography (PEM) systems have higher sensitivity than clinical whole body PET systems because they have a smaller ring diameter. However, the spatial resolution of PEM systems is not high enough to detect early stage breast cancer. To solve this problem, we developed a silicon photomultiplier (Si-PM) based detector unit for the development of a PEM system. Since a Si-PM's channel is small, Si-PM can resolve small scintillator pixels to improve the spatial resolution. Also Si-PM based detectors have inherently high timing resolution and are able to reduce the random coincidence events by reducing the time window. We used 1.5×1.9×15 mm LGSO scintillation pixels and arranged them in an 8×24 matrix to form scintillator blocks. Four scintillator blocks were optically coupled to Si-PM arrays with an angled light guide to form a detector unit. Since the light guide has angles of 5.625°, we can arrange 64 scintillator blocks in a nearly circular shape (a regular 64-sided polygon) using 16 detector units. We clearly resolved the pixels of the scintillator blocks in a 2-dimensional position histogram where the averages of the peak-to-valley ratios (P/Vs) were 3.7±0.3 and 5.7±0.8 in the transverse and axial directions, respectively. The average energy resolution was 14.2±2.1% full-width at half-maximum (FWHM). By including the temperature dependent gain control electronics, the photo-peak channel shifts were controlled within ±1.5% with the temperature from 23 °C to 28 °C. With these results, in addition to the potential high timing performance of Si-PM based detectors, our developed detector unit is promising for the development of a high-resolution PEM system.

  4. Habitat Demonstration Unit (HDU) Pressurized Excursion Module (PEM) Systems Integration Strategy

    Science.gov (United States)

    Gill, Tracy; Merbitz, Jerad; Kennedy, Kriss; Tri, Terry; Toups, Larry; Howe, A. Scott

    2011-01-01

    The Habitat Demonstration Unit (HDU) project team constructed an analog prototype lunar surface laboratory called the Pressurized Excursion Module (PEM). The prototype unit subsystems were integrated in a short amount of time, utilizing a rapid prototyping approach that brought together over 20 habitation-related technologies from a variety of NASA centers. This paper describes the system integration strategies and lessons learned, that allowed the PEM to be brought from paper design to working field prototype using a multi-center team. The system integration process was based on a rapid prototyping approach. Tailored design review and test and integration processes facilitated that approach. The use of collaboration tools including electronic tools as well as documentation enabled a geographically distributed team take a paper concept to an operational prototype in approximately one year. One of the major tools used in the integration strategy was a coordinated effort to accurately model all the subsystems using computer aided design (CAD), so conflicts were identified before physical components came together. A deliberate effort was made following the deployment of the HDU PEM for field operations to collect lessons learned to facilitate process improvement and inform the design of future flight or analog versions of habitat systems. Significant items within those lessons learned were limitations with the CAD integration approach and the impact of shell design on flexibility of placing systems within the HDU shell.

  5. NASA's Habitat Demonstration Unit (HDU) Pressurized Excursion Module (PEM) In-Field Demonstration at Desert RATS 2010

    Science.gov (United States)

    Tri, Terry O.; Kennedy, Kriss J.; Toups, Larry; Gill, Tracy R.; Howe, A. Scott

    2011-01-01

    This paper describes the construction, assembly, subsystem integration, transportation, and field testing operations associated with the Habitat Demonstration Unit (HDU) Pressurized Excursion Module (PEM) and discusses lessons learned. In a one-year period beginning summer 2009, a tightly scheduled design-develop-build process was utilized by a small NASA "tiger team" to produce the functional HDU-PEM prototype in time to participate in the 2010 Desert Research and Technology Studies (Desert RATS) field campaign. The process required the coordination of multiple teams, subcontractors, facility management and safety staff. It also required a well-choreographed material handling and transportation process to deliver the finished product from the NASA-Johnson Space Center facilities to the remote Arizona desert locations of the field test. Significant findings of this paper include the team s greater understanding of the HDU-PEM s many integration issues and the in-field training the team acquired which will enable the implementation of the next-generation of improvements and development of high-fidelity field operations in a harsh environment. The Desert RATS analog environment is being promoted by NASA as an efficient means to design, build, and integrate multiple technologies in a mission architecture context, with the eventual goal of evolving the technologies into robust flight hardware systems. The HDU-PEM in-field demonstration at Desert RATS 2010 provided a validation process for the integration team, which has already begun to retool for the 2011 field tests that require an adapted architecture.

  6. Analysis of accelerated degradation of a HT-PEM fuel cell caused by cell reversal in fuel starvation condition

    DEFF Research Database (Denmark)

    Zhou, Fan; Andreasen, Søren Juhl; Kær, Søren Knudsen;

    2015-01-01

    This paper reports an accelerated degradation test of a high temperature PEM fuel cell under repeated H2 starvation condition. The H2 stoichiometry is cycled between 3.0 and 0.8 every 2 min during the test. The experimental results show that the polarity of the fuel cell is reversed under H2...... starvation condition, and the cell performance indicated by cell voltage at H2 stoichiometry of 3.0 declines from 0.59 V to 0.41 V in 19 cycles. Since CO2 is detected in anode exhaust under H2 starvation condition, carbon corrosion is believed to be the reason for the degradation in this test. After the test......, there is only a slight decrease in open circuit voltage of the fuel cell which implies the membrane is not affected by the test. The electrochemical impedance spectrum measurement shows that the H2 starvation can cause significant increase in the ohmic resistance and charge transfer resistance. By looking...

  7. Optimized 4-bit Quantum Reversible Arithmetic Logic Unit

    Science.gov (United States)

    Ayyoub, Slimani; Achour, Benslama

    2017-08-01

    Reversible logic has received a great attention in the recent years due to its ability to reduce the power dissipation. The main purposes of designing reversible logic are to decrease quantum cost, depth of the circuits and the number of garbage outputs. The arithmetic logic unit (ALU) is an important part of central processing unit (CPU) as the execution unit. This paper presents a complete design of a new reversible arithmetic logic unit (ALU) that can be part of a programmable reversible computing device such as a quantum computer. The proposed ALU based on a reversible low power control unit and small performance parameters full adder named double Peres gates. The presented ALU can produce the largest number (28) of arithmetic and logic functions and have the smallest number of quantum cost and delay compared with existing designs.

  8. Reversible arithmetic logic unit for quantum arithmetic

    DEFF Research Database (Denmark)

    Thomsen, Michael Kirkedal; Glück, Robert; Axelsen, Holger Bock

    2010-01-01

    -bit operands and does not use ancillae. This remarkable low resource consumption was achieved by generalizing the V-shape design first introduced for quantum ripple-carry adders and nesting multiple V-shapes in a novel integrated design. This communication shows that the realization of an efficient reversible...

  9. COURSE REVERSAL OF TRACTOR UNIT ON FLAT PLOUGHING

    Directory of Open Access Journals (Sweden)

    V. Jatskevich

    2012-01-01

    Full Text Available The paper proposes a supportive maneuvering device for course reversal of a wheeled tractor unit on a smooth flat ploughing, its novelty is proved by a patent for an invention. Application of the supportive maneuvering device does not require any changes in design of commercial tractors. Theoretical and experimental investigations have been carried out in order to determine moments of resistance to course reversal according to minimum radius and time for such manouevre.

  10. Optimization Approaches for Designing Quantum Reversible Arithmetic Logic Unit

    Science.gov (United States)

    Haghparast, Majid; Bolhassani, Ali

    2016-03-01

    Reversible logic is emerging as a promising alternative for applications in low-power design and quantum computation in recent years due to its ability to reduce power dissipation, which is an important research area in low power VLSI and ULSI designs. Many important contributions have been made in the literatures towards the reversible implementations of arithmetic and logical structures; however, there have not been many efforts directed towards efficient approaches for designing reversible Arithmetic Logic Unit (ALU). In this study, three efficient approaches are presented and their implementations in the design of reversible ALUs are demonstrated. Three new designs of reversible one-digit arithmetic logic unit for quantum arithmetic has been presented in this article. This paper provides explicit construction of reversible ALU effecting basic arithmetic operations with respect to the minimization of cost metrics. The architectures of the designs have been proposed in which each block is realized using elementary quantum logic gates. Then, reversible implementations of the proposed designs are analyzed and evaluated. The results demonstrate that the proposed designs are cost-effective compared with the existing counterparts. All the scales are in the NANO-metric area.

  11. Optimization of membrane elements' array in industrial reverse osmosis units

    Science.gov (United States)

    Bobinkin, V. V.; Larionov, S. Yu.; Panteleev, A. A.; Shapovalov, D. A.; Shilov, M. M.

    2015-10-01

    It is stated that membrane elements, due to axial concentration and flow exhaustion during filtration, work in different operation conditions that differ according to various characteristics. Designing of multistage units is based on technical characteristics' identity of all membrane elements. It is explored that the difference in individual characteristics of membrane elements can take place. This can essentially affect the operation characteristics of a whole industrial unit. Particularly, it could lead to degradation of the permeate quality and the unit performance. Research on packaging the membrane elements in reverse osmosis units has shown that a simple replacement of membrane elements without the consideration of the individual characteristics can degrade the performance characteristics and affect the constancy of the unit operation. An optimization system of membrane elements' array was suggested to solve these problems and to upgrade the performance of reverse osmosis plants. The first step of the system is determination of individual characteristics of membrane elements. For the calculations using the individualized data, it is suggested to use the method of approximate calculation and the balance equations for water flows (source water, permeate, and retentate), and for the concentrations of the dissolved solids. The suggested optimization system of a membrane elements' array allowed the configuration of the membrane elements in the housings of one stage in such a way that the symmetry of the flows and of the pressure difference was achieved. The optimum value of the performance and the selectivity was achieved considering the hydraulic characteristics in one stage.

  12. PEM Fuel Cells - Fundamentals, Modeling and Applications

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2013-01-01

    Full Text Available Part I: Fundamentals Chapter 1: Introduction. Chapter 2: PEM fuel cell thermodynamics, electrochemistry, and performance. Chapter 3: PEM fuel cell components. Chapter 4: PEM fuel cell failure modes. Part II: Modeling and Simulation Chapter 5: PEM fuel cell models based on semi-empirical simulation. Chapter 6: PEM fuel cell models based on computational fluid dynamics. Part III: Applications Chapter 7: PEM fuel cell system design and applications.

  13. PEM fuel cell degradation

    Energy Technology Data Exchange (ETDEWEB)

    Borup, Rodney L [Los Alamos National Laboratory; Mukundan, Rangachary [Los Alamos National Laboratory

    2010-01-01

    The durability of PEM fuel cells is a major barrier to the commercialization of these systems for stationary and transportation power applications. While significant progress has been made in understanding degradation mechanisms and improving materials, further improvements in durability are required to meet commercialization targets. Catalyst and electrode durability remains a primary degradation mode, with much work reported on understanding how the catalyst and electrode structure degrades. Accelerated Stress Tests (ASTs) are used to rapidly evaluate component degradation, however the results are sometimes easy, and other times difficult to correlate. Tests that were developed to accelerate degradation of single components are shown to also affect other component's degradation modes. Non-ideal examples of this include ASTs examining catalyst degradation performances losses due to catalyst degradation do not always well correlate with catalyst surface area and also lead to losses in mass transport.

  14. Design of Parity Preserving Logic Based Fault Tolerant Reversible Arithmetic Logic Unit

    Directory of Open Access Journals (Sweden)

    Rakshith Saligram1

    2013-06-01

    Full Text Available Reversible Logic is gaining significant consideration as the potential logic design style for implementation in modern nanotechnology and quantum computing with minimal impact on physical entropy .Fault Tolerant reversible logic is one class of reversible logic that maintain the parity of the input and the outputs. Significant contributions have been made in the literature towards the design of fault tolerant reversible logic gate structures and arithmetic units, however, there are not many efforts directed towards the design of fault tolerant reversible ALUs. Arithmetic Logic Unit (ALU is the prime performing unit in any computing device and it has to be made fault tolerant. In this paper we aim to design one such fault tolerant reversible ALU that is constructed using parity preserving reversible logic gates. The designed ALU can generate up to seven Arithmetic operations and four logical operations

  15. Current interruption measurement and analysis for PEM fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Sun, J.C.; Yuan, X.; Wang, H. [National Research Council of Canada, Vancouver, BC (Canada). Inst. for Fuel Cell Innovation

    2007-07-01

    The ohmic resistance, charge transfer resistance and the capacity discharge limit of proton exchange membrane (PEM) fuel cells can be evaluated and characterized by a newly developed, low cost, current interruption measuring method. This paper presented the results of a study in which the current interruption measurement for a PEM fuel cell was set up and proven through measurements with a dummy cell. The current interruption characteristics of a 500 W PEM fuel cell stack with an active area of 280 cm{sup 2} was measured using the National Instrument PCI data acquisition unit combined with a TDI electronics load-bank and a FuelCon test station, at different load currents. The ohmic loss of the stack determined by current interruption measurements was in good agreement with that determined by AC impedance spectroscopy. The same setup was shown to be effective for single cell measurements of a small PEM fuel cell and for a PEM fuel cell stack with a load bank. It was concluded that the current interruption measurement is much faster than the AC impedance method, but has lower accuracy, particularly for a signal with high noise. 1 ref., 10 figs.

  16. A regulatory role for Staphylococcus aureus toxin-antitoxin system PemIKSa.

    Science.gov (United States)

    Bukowski, Michal; Lyzen, Robert; Helbin, Weronika M; Bonar, Emilia; Szalewska-Palasz, Agnieszka; Wegrzyn, Grzegorz; Dubin, Grzegorz; Dubin, Adam; Wladyka, Benedykt

    2013-01-01

    Toxin-antitoxin systems were shown to be involved in plasmid maintenance when they were initially discovered, but other roles have been demonstrated since. Here we identify and characterize a novel toxin-antitoxin system (pemIKSa) located on Staphylococcus aureus plasmid pCH91. The toxin (PemKSa) is a sequence-specific endoribonuclease recognizing the tetrad sequence U↓AUU, and the antitoxin (PemISa) inhibits toxin activity by physical interaction. Although the toxin-antitoxin system is responsible for stable plasmid maintenance our data suggest the participation of pemIKSa in global regulation of staphylococcal virulence by alteration of the translation of large pools of genes. We propose a common mechanism of reversible activation of toxin-antitoxin systems based on antitoxin transcript resistance to toxin cleavage. Elucidation of this mechanism is particularly interesting because reversible activation is a prerequisite for the proposed general regulatory role of toxin-antitoxin systems.

  17. Design of Parity Preserving Logic Based Fault Tolerant Reversible Arithmetic Logic Unit

    Directory of Open Access Journals (Sweden)

    Rakshith Saligram

    2013-07-01

    Full Text Available Reversible Logic is gaining significant consideration as the potential logic design style for implementationin modern nanotechnology and quantum computing with minimal impact on physical entropy .FaultTolerant reversible logic is one class of reversible logic that maintain the parity of the input and theoutputs. Significant contributions have been made in the literature towards the design of fault tolerantreversible logic gate structures and arithmetic units, however, there are not many efforts directed towardsthe design of fault tolerant reversible ALUs. Arithmetic Logic Unit (ALU is the prime performing unit inany computing device and it has to be made fault tolerant. In this paper we aim to design one such faulttolerant reversible ALU that is constructed using parity preserving reversible logic gates. The designedALU can generate up to seven Arithmetic operations and four logical operations.

  18. Corrosion resistant PEM fuel cell

    Science.gov (United States)

    Fronk, Matthew Howard; Borup, Rodney Lynn; Hulett, Jay S.; Brady, Brian K.; Cunningham, Kevin M.

    2002-01-01

    A PEM fuel cell having electrical contact elements comprising a corrosion-susceptible substrate metal coated with an electrically conductive, corrosion-resistant polymer containing a plurality of electrically conductive, corrosion-resistant filler particles. The substrate may have an oxidizable metal first layer (e.g., stainless steel) underlying the polymer coating.

  19. Hydrogen-Oxygen PEM Regenerative Fuel Cell Energy Storage System

    Science.gov (United States)

    Bents, David J.; Scullin, Vincent J.; Chang, Bei-Jiann; Johnson, Donald W.; Garcia, Christopher P.

    2005-01-01

    An introduction to the closed cycle hydrogen-oxygen polymer electrolyte membrane (PEM) regenerative fuel cell (RFC), recently constructed at NASA Glenn Research Center, is presented. Illustrated with explanatory graphics and figures, this report outlines the engineering motivations for the RFC as a solar energy storage device, the system requirements, layout and hardware detail of the RFC unit at NASA Glenn, the construction history, and test experience accumulated to date with this unit.

  20. Advanced Passive Liquid Feed PEM Electrolyzer Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Proton Exchange Membrane (PEM) water electrolyzers have undergone continuous development for the generation of oxygen and hydrogen for commercial, military and space...

  1. Advanced Passive Liquid Feed PEM Electrolyzer Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Proton Exchange Membrane (PEM) water electrolyzers have undergone continuous development for the generation of oxygen and hydrogen for commercial, military and...

  2. 40 CFR 1065.915 - PEMS instruments.

    Science.gov (United States)

    2010-07-01

    ..., electromagnetic radiation, and ambient hydrocarbons. Follow the PEMS manufacturer's instructions for proper... the use of such signals in advance. (6) Permissible deviations. ECM signals may deviate from...

  3. Panel Unit Root Test with Nonlinear Mean Reversion and Smooth Breaks

    OpenAIRE

    Lau, Chi Keung Marco; Chau, Frankie; Deesomsak, Rataporn

    2011-01-01

    This paper extends the unit root test of Christopoulos and Leòn-Ledesma (2010) to accommodate not only structural breaks and non-linear mean reversion, but also the contemporaneous cross-sectional dependence commonly found in panel dataset. The proposed test presents good finite sample properties and its applications on four major ASEAN countries’ real exchange rates show that the unit root hypothesis could be rejected, supporting their long-run Purchasing Power Parity (PPP) again...

  4. Experimental characterization of the Clear-PEM scanner spectrometric performance

    Science.gov (United States)

    Bugalho, R.; Carriço, B.; Ferreira, C. S.; Frade, M.; Ferreira, M.; Moura, R.; Ortigão, C.; Pinheiro, J. F.; Rodrigues, P.; Rolo, I.; Silva, J. C.; Trindade, A.; Varela, J.

    2009-10-01

    In the framework of the Clear-PEM project for the construction of a high-resolution and high-specificity scanner for breast cancer imaging, a Positron Emission Mammography tomograph has been developed and installed at the Instituto Português de Oncologia do Porto hospital. The Clear-PEM scanner is mainly composed by two planar detector heads attached to a robotic arm, trigger/data acquisition electronics system and computing servers. The detector heads hold crystal matrices built from 2 × 2 × 20 mm3 LYSO:Ce crystals readout by Hamamatsu S8550 APD arrays. The APDs are optically coupled to both ends of the 6144 crystals in order to extract the DOI information for each detected event. Each one of 12288 APD's pixels is read and controlled by Application Specific Integrated Circuits water-cooled by an external cooling unit. The Clear-PEM frontend boards innovative design results in a unprecedented integration of the crystal matrices, APDs and ASICs, making Clear-PEM the PET scanner with the highest number of APD pixels ever integrated so far. In this paper, the scanner's main technical characteristics, calibration strategies and the first spectrometric performance evaluation in a clinical environment are presented. The first commissioning results show 99.7% active channels, which, after calibration, have inter-pixel and absolute gain distributions with dispersions of, respectively, 12.2% and 15.3%, demonstrating that despite the large number of channels, the system is uniform. The mean energy resolution at 511 keV is of 15.9%, with a 8.8% dispersion, and the mean CDOI-1 is 5.9%/mm, with a 7.8% dispersion. The coincidence time resolution, at 511 keV, for a energy window between 400 and 600 keV, is 5.2 ns FWHM.

  5. Experimental characterization of the Clear-PEM scanner spectrometric performance

    Energy Technology Data Exchange (ETDEWEB)

    Bugalho, R; Carrico, B; Ferreira, C S; Frade, M; Ferreira, M; Moura, R; Ortigao, C; Pinheiro, J F; Rodrigues, P; Rolo, I; Silva, J C; Trindade, A; Varela, J [Laboratorio de Instrumentacao e Fisica Experimental de Particulas (LIP), Av. Elias Garcia 14-1, 1000-149 Lisboa (Portugal)], E-mail: frade@lip.pt

    2009-10-15

    In the framework of the Clear-PEM project for the construction of a high-resolution and high-specificity scanner for breast cancer imaging, a Positron Emission Mammography tomograph has been developed and installed at the Instituto Portugues de Oncologia do Porto hospital. The Clear-PEM scanner is mainly composed by two planar detector heads attached to a robotic arm, trigger/data acquisition electronics system and computing servers. The detector heads hold crystal matrices built from 2 x 2 x 20 mm{sup 3} LYSO:Ce crystals readout by Hamamatsu S8550 APD arrays. The APDs are optically coupled to both ends of the 6144 crystals in order to extract the DOI information for each detected event. Each one of 12288 APD's pixels is read and controlled by Application Specific Integrated Circuits water-cooled by an external cooling unit. The Clear-PEM frontend boards innovative design results in a unprecedented integration of the crystal matrices, APDs and ASICs, making Clear-PEM the PET scanner with the highest number of APD pixels ever integrated so far. In this paper, the scanner's main technical characteristics, calibration strategies and the first spectrometric performance evaluation in a clinical environment are presented. The first commissioning results show 99.7% active channels, which, after calibration, have inter-pixel and absolute gain distributions with dispersions of, respectively, 12.2% and 15.3%, demonstrating that despite the large number of channels, the system is uniform. The mean energy resolution at 511 keV is of 15.9%, with a 8.8% dispersion, and the mean C{sub DOI}{sup -1} is 5.9%/mm, with a 7.8% dispersion. The coincidence time resolution, at 511 keV, for a energy window between 400 and 600 keV, is 5.2 ns FWHM.

  6. PEM Degradation Investigation Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Dan Stevenson; Lee H Spangler

    2010-10-18

    This project conducted fundamental studies of PEM MEA degradation. Insights gained from these studies were disseminated to assist MEA manufacturers in understanding degradation mechanisms and work towards DOE 2010 fuel cell durability targets.

  7. Micro PEM Fuel Cells and Stacks

    Institute of Scientific and Technical Information of China (English)

    Shou-shing; Hsieh

    2007-01-01

    1 Results The effects of different operating parameters on micro proton exchange membrane (PEM) fuel cell performance were experimentally studied for three different flow field configurations (interdigitated,mesh,and serpentine).Experiments with different cell operating temperatures and different backpressures on the H2 flow channels,as well as various combinations of these parameters,have been conducted for three different flow geometries.The micro PEM fuel cells were designed and fabricated in-house t...

  8. NASA's PEM Fuel Cell Power Plant Development Program for Space Applications

    Science.gov (United States)

    Hoberecht, Mark A.

    2008-01-01

    A three-center NASA team led by the Glenn Research Center in Cleveland, Ohio is completing a five-year PEM fuel cell power plant development program for future space applications. The focus of the program has been to adapt commercial PEM fuel cell technology for space applications by addressing the key mission requirements of using pure oxygen as an oxidant and operating in a multi-gravity environment. Competing vendors developed breadboard units in the 1 to 5 kW power range during the first phase of the program, and a single vendor developed a nominal 10-kW engineering model power pant during the second phase of the program. Successful performance and environmental tests conducted by NASA established confidence that PEM fuel cell technology will be ready to meet the electrical power needs of future space missions.

  9. Durability study of PEM fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Wu, J.F.; Yuan, X.Z.; Martin, J.J.; Wang, H.J. [National Research Council of Canada, Vancouver, BC (Canada). Inst. for Fuel Cell Innovation; Bi, X.T. [British Columbia Univ., Vancouver, BC (Canada). Dept. of Chemical and Biological Engineering; Pei, P.C.; Huang, H.Y. [Tsinghua Univ., Beijing (China). Dept. of Automotive Engineering

    2007-07-01

    Technical challenges limit the commercialization of polymer electrolyte membrane fuel cells (PEM) for use in stationary applications and transport. These include: on-board storage and infrastructure for hydrogen fuel as well as the fuel cell system itself; high costs; and, durability under a wide range of operational conditions. Durability is defined as the maximum service life of a fuel cell system with no more than 10 per cent loss in efficiency at the end of life. This paper presented a literature review and analysis in order to provide a unified definition of PEM fuel cell service life when operated at either steady state or dynamic load conditions. The paper presented an analysis of different operating conditions and the dependence of PEM fuel cell durability on the operating condition. The paper also reviewed durability studies of the different components of a PEM fuel cell, and also examined various degradation mechanisms. These included: load or thermal cycles; fuel or oxidant starvation; high or low humidification levels; and, reformate or simulated reformed gases as fuels. A relationship between the accelerated service life of a PEM fuel cell and the real service life was then developed. To obtain real service life under normal testing conditions, statistical models based on accelerated service life data were illustrated. It was concluded that the service life of a fuel cell and its components is a function of more than one or two variables. 46 refs., 4 tabs., 3 figs.

  10. PEMS. Advanced predictive emission monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Sandvig Nielsen, J.

    2010-07-15

    In the project PEMS have been developed for boilers, internal combustion engines and gas turbines. The PEMS models have been developed using two principles: The one called ''first principles'' is based on thermo-kinetic modeling of the NO{sub x}-formation by modeling conditions (like temperature, pressure and residence time) in the reaction zones. The other one is data driven using artificial neural network (ANN) and includes no physical properties and no thermo-kinetic formulation. Models of first principles have been developed for gas turbines and gas engines. Data driven models have been developed for gas turbines, gas engines and boilers. The models have been tested on data from sites located in Denmark and the Middle East. Weel and Sandvig has conducted the on-site emission measurements used for development and testing the PEMS models. For gas turbines, both the ''first principles'' and the data driven models have performed excellent considering the ability to reproduce the emission levels of NO{sub x} according to the input variables used for calibration. Data driven models for boilers and gas engines have performed excellent as well. The rather comprehensive first principle model, developed for gas engines, did not perform as well in the prediction of NO{sub x}. Possible a more complex model formulation is required for internal combustion engines. In general, both model types have been validated on data extracted from the data set used for calibration. The data for validation have been selected randomly as individual samplings, and is scattered over the entire measuring campaign. For one natural gas engine a secondary measuring campaign was conducted half a year later than the campaign used for training the data driven model. In the meantime, this engine had been through a refurbishment that included new pistons, piston rings and cylinder linings and cleaning of the cylinder heads. Despite the refurbishment, the

  11. PEMS. Advanced predictive emission monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Sandvig Nielsen, J.

    2010-07-15

    In the project PEMS have been developed for boilers, internal combustion engines and gas turbines. The PEMS models have been developed using two principles: The one called ''first principles'' is based on thermo-kinetic modeling of the NO{sub x}-formation by modeling conditions (like temperature, pressure and residence time) in the reaction zones. The other one is data driven using artificial neural network (ANN) and includes no physical properties and no thermo-kinetic formulation. Models of first principles have been developed for gas turbines and gas engines. Data driven models have been developed for gas turbines, gas engines and boilers. The models have been tested on data from sites located in Denmark and the Middle East. Weel and Sandvig has conducted the on-site emission measurements used for development and testing the PEMS models. For gas turbines, both the ''first principles'' and the data driven models have performed excellent considering the ability to reproduce the emission levels of NO{sub x} according to the input variables used for calibration. Data driven models for boilers and gas engines have performed excellent as well. The rather comprehensive first principle model, developed for gas engines, did not perform as well in the prediction of NO{sub x}. Possible a more complex model formulation is required for internal combustion engines. In general, both model types have been validated on data extracted from the data set used for calibration. The data for validation have been selected randomly as individual samplings, and is scattered over the entire measuring campaign. For one natural gas engine a secondary measuring campaign was conducted half a year later than the campaign used for training the data driven model. In the meantime, this engine had been through a refurbishment that included new pistons, piston rings and cylinder linings and cleaning of the cylinder heads. Despite the refurbishment, the

  12. PEM fuel cell testing and diagnosis

    CERN Document Server

    Wu, Jifeng; Zhang, Jiujun

    2013-01-01

    PEM Fuel Cell Testing and Diagnosis covers the recent advances in PEM (proton exchange membrane) fuel cell systems, focusing on instruments and techniques for testing and diagnosis, and the application of diagnostic techniques in practical tests and operation. This book is a unique source of electrochemical techniques for researchers, scientists and engineers working in the area of fuel cells. Proton exchange membrane fuel cells are currently considered the most promising clean energy-converting devices for stationary, transportation, and micro-power applications due to their

  13. A retrospective on the LBNL PEM project

    Energy Technology Data Exchange (ETDEWEB)

    Huber, J.S.; Moses, W.W.; Wang, G.C.; Derenzo, S.E.; Huesman,R.H.; Qi, J.; Virador, P.; Choong, W.S.; Mandelli, E.; Beuville, E.; Pedrali-Noy, M.; Krieger, B.; Meddeler, G.

    2004-11-15

    We present a retrospective on the LBNL Positron EmissionMammography (PEM) project, looking back on our design and experiences.The LBNL PEM camera utilizes detector modules that are capable ofmeasuring depth of interaction (DOI) and places them into 4 detectorbanks in a rectangular geometry. In order to build this camera, we had todevelop the DOI detector module, LSO etching, Lumirror-epoxy reflectorfor the LSO array (to achieve optimal DOI), photodiode array, custom IC,rigid-flex readout board, packaging, DOI calibration and reconstructionalgorithms for the rectangular camera geometry. We will discuss thehighlights (good and bad) of these developments.

  14. HDU Pressurized Excursion Module (PEM) Prototype Systems Integration

    Science.gov (United States)

    Gill, Tracy R.; Kennedy, Kriss; Tri, Terry; Toups, Larry; Howe, A. Scott

    2010-01-01

    The Habitat Demonstration Unit (HDU) project team constructed an analog prototype lunar surface laboratory called the Pressurized Excursion Module (PEM). The prototype unit subsystems were integrated in a short amount of time, utilizing a skunk-works approach that brought together over 20 habitation-related technologies from a variety of NASA centers. This paper describes the system integration strategies and lessons learned, that allowed the PEM to be brought from paper design to working field prototype using a multi-center team. The system integration process included establishment of design standards, negotiation of interfaces between subsystems, and scheduling fit checks and installation activities. A major tool used in integration was a coordinated effort to accurately model all the subsystems using CAD, so that conflicts were identified before physical components came together. Some of the major conclusions showed that up-front modularity that emerged as an artifact of construction, such as the eight 45 degree "pie slices" making up the module whose steel rib edges defined structural mounting and loading points, dictated much of the configurational interfaces between the major subsystems and workstations. Therefore, 'one of the lessons learned included the need to use modularity as a tool for organization in advance, and to work harder to prevent non-critical aspects of the platform from dictating the modularity that may eventually inform the fight system.

  15. Transients of Water Distribution and Transport in PEM Fuel Cells

    KAUST Repository

    Hussaini, Irfan S.

    2009-01-01

    The response of polymer electrolyte membrane (PEM) fuel cells to a step change in load is investigated experimentally in this work. Voltage undershoot, a characteristic feature of transient response following a step increase in current, is due to transients of water distribution in the membrane and ionomers occurring at subsecond time scales. The use of humidified reactants as a means to control the magnitude of voltage undershoot is demonstrated. Further, the response under a step decrease in current density is explored to determine the existence of hysteresis. Under sufficiently humidified conditions, the responses under forward and reverse step changes are symmetric, but under low relative humidity conditions, voltage undershoot is twice as large as the overshoot. © 2009 The Electrochemical Society.

  16. PEM Fuel Cells Redesign Using Biomimetic and TRIZ Design Methodologies

    Science.gov (United States)

    Fung, Keith Kin Kei

    Two formal design methodologies, biomimetic design and the Theory of Inventive Problem Solving, TRIZ, were applied to the redesign of a Proton Exchange Membrane (PEM) fuel cell. Proof of concept prototyping was performed on two of the concepts for water management. The liquid water collection with strategically placed wicks concept demonstrated the potential benefits for a fuel cell. Conversely, the periodic flow direction reversal concepts might cause a potential reduction water removal from a fuel cell. The causes of this water removal reduction remain unclear. In additional, three of the concepts generated with biomimetic design were further studied and demonstrated to stimulate more creative ideas in the thermal and water management of fuel cells. The biomimetic design and the TRIZ methodologies were successfully applied to fuel cells and provided different perspectives to the redesign of fuel cells. The methodologies should continue to be used to improve fuel cells.

  17. Modelling, experimentation and simulation of a reversible HP/ORC unit to get a Positive Energy Building

    DEFF Research Database (Denmark)

    Dumont, Olivier; Carmo, Carolina; Quoilin, Sylvain

    2015-01-01

    covering the building annual heating needs and, furthermore, electricity is produced thanks to the surplus of heat in a so-called HP/ORC reversible unit. This paper focus on these three main points: sizing, experimentation and simulation of the reversible unit. First, an optimal sizing of the components...... storage, the solar roof and the reversible HP/ORC unit is developed and allows to perform a sensivity analysis. Annual results show that this technology leads to a Positive Energy Building....... and fluid R134a shows promising performance with a net electrical energy produced over one year reaching 4030 kWh. Following that, a prototype has been built and has proven the feasibility of the technology. Finally, a simulation code including the building, the ground heat exchanger, the thermal energy...

  18. Capture and Reversible Storage of Volatile Iodine by Novel Conjugated Microporous Polymers Containing Thiophene Units.

    Science.gov (United States)

    Qian, Xin; Zhu, Zhao-Qi; Sun, Han-Xue; Ren, Feng; Mu, Peng; Liang, Weidong; Chen, Lihua; Li, An

    2016-08-17

    Conjugated microporous polymers having thiophene building blocks (SCMPs), which originated from ethynylbenzene monomers with 2,3,5-tribromothiophene, were designedly synthesized through Pd(0)/CuI catalyzed Sonogashira-Hagihara cross-coupling polymerization. The morphologies, structure and physicochemical properties of the as-synthesized products were characterized through scanning electron microscope (SEM), thermogravimeter analysis (TGA), (13)C CP/MAS solid state NMR and Fourier transform infrared spectroscope (FTIR) spectra. Nitrogen sorption-desorption analysis shows that the as-synthesized SCMPs possesses a high specific surface area of 855 m(2) g(-1). Because of their abundant porosity, π-conjugated network structure, as well as electron-rich thiophene building units, the SCMPs show better adsorption ability for iodine and a high uptake value of 222 wt % was obtained, which can compete with those nanoporous materials such as silver-containing zeolite, metal-organic frameworks (MOFs) and conjugated microporous polymers (CMPs), etc. Our study might provide a new possibility for the design and synthesis of functional CMPs containing electron-rich building units for effective capture and reversible storage of volatile iodine to address environmental issues.

  19. Simulation of a passive house coupled with a heat pump/organic Rankine cycle reversible unit

    DEFF Research Database (Denmark)

    Dumont, Olivier; Carmo, Carolina; Randaxhe, François

    2014-01-01

    modes that need to be chosen optimally depending on the weather conditions, the heat demand and the temperature level of the storage. The ORC mode is activated, as long as the heat demand of the house is covered by the storage to produce electricity based upon the heat generated by the solar roof...... regarding control strategies and enhancement of the global system are drawn. A control strategy with a low storage temperature set-point (50˚C) allows reducing electrical consumption from 11% up to 24% when compared to higher set-point (60˚C). The system performance to produce power could also be optimized......This paper presents a dynamic model of a passive house located in Denmark with a large solar absorber, a horizontal ground heat exchanger coupled with a HP/ORC unit. The HP/ORC reversible unit is a module able to work as an Organic Rankine Cycle (ORC) or as a heat pump (HP). There are 3 possible...

  20. Repacking practice for G-3 engineering driller power unit with drive shaft of dual channel reverse circulation

    Institute of Scientific and Technical Information of China (English)

    Lihong ZHU; Kun YIN; Qingyan WANG; Yong HUANG

    2008-01-01

    In order to satisfy operating requirements for constant core drilling technology in reverse circulation with hollow-through DTH,the power unit of G-3 engineering driller was ameliorated. The new one with dual channel drive shaft, achieved the perfect assemble with transmission structure of the original power unit. It could interconvert according to need by using two sets of drive shafts with direct and reverse circulation. The repacked G-3 engineering driller carried on experiment in the field test in Luanchuan molybdenum mine of Henan, whose effect was very good.

  1. PEM fuel cells thermal and water management fundamentals

    CERN Document Server

    Wang, Yun; Cho, Sung Chan

    2014-01-01

    Polymer Electrolyte Membrane (PEM) fuel cells convert chemical energy in hydrogen into electrical energy with water as the only by-product. Thus, PEM fuel cells hold great promise to reduce both pollutant emissions and dependency on fossil fuels, especially for transportation-passenger cars, utility vehicles, and buses-and small-scale stationary and portable power generators. But one of the greatest challenges to realizing the high efficiency and zero emissions potential of PEM fuel cells technology is heat and water management. This book provides an introduction to the essential concepts for effective thermal and water management in PEM fuel cells and an assessment on the current status of fundamental research in this field. The book offers you: An overview of current energy and environmental challenges and their imperatives for the development of renewable energy resources, including discussion of the role of PEM fuel cells in addressing these issues; Reviews of basic principles pertaining to PEM fuel cel...

  2. Modular PEM Fuel Cell SCADA & Simulator System

    Directory of Open Access Journals (Sweden)

    Francisca Segura

    2015-09-01

    Full Text Available The paper presents a Supervision, Control, Data Acquisition and Simulation (SCADA & Simulator system that allows for real-time training in the actual operation of a modular PEM fuel cell system. This SCADA & Simulator system consists of a free software tool that operates in real time and simulates real situations like failures and breakdowns in the system. This developed SCADA & Simulator system allows us to properly operate a fuel cell and helps us to understand how fuel cells operate and what devices are needed to configure and run the fuel cells, from the individual stack up to the whole fuel cell system. The SCADA & Simulator system governs a modular system integrated by three PEM fuel cells achieving power rates higher than tens of kilowatts.

  3. Palladium-based electrocatalysts for PEM applications

    Energy Technology Data Exchange (ETDEWEB)

    Grigoriev S; Lyutikova E; Fateev V [Hydrogen Energy and Plasma Technology Institute of Russian Research Center ' Kurchatov Institute' 1, Kurchatov sq., 123182 Moscow (Russian Federation); Martemianov S [Laboratoire d Etudes Thermiques, UMR CNRS no 6608, ESIP, Universite de Poitiers 40, avenue du Recteur Pineau, 86022 Poitiers Cedex (France); Lebouin C; Millet P [Institut de Chimie Moleculaire et des Materiaux d' Orsay, UMR CNRS no 8182, Universite Paris-sud XI 15, rue Georges Clemenceau, 91405 Orsay Cedex (France); Lebouin C [Laboratoire d Electrochimie et de Physicochimie des Materiaux et des Interfaces, CNRS-INPG-UJF 1130 rue de la Piscine, 38402 Saint Martin d Heres, (France)

    2006-07-01

    The goal of present study is development and investigation of nano-structured Pd-based electrocatalysts for hydrogen oxidation and proton reduction in proton exchange membrane (PEM) fuel cells and electrolyzers. Electro-active metallic structures were obtained by chemical reduction of precursor salts (including on Vulcan XC-72 carbon carrier) using ethylene glycol with addition of formaldehyde or using borohydride. Alternatively, Pd nano-clusters have been obtained from chemical reduction of precursor salts in per-fluorinated polymer Nafion membrane. Using the synthesized Pd-based catalyst membrane-electrode assemblies (MEAs) have been prepared and successfully tested in single fuel and electrolysis cells. Comparison of MEAs performances based on Pt, PtPd- and Pd-based electrocatalysts were provided. The present study demonstrates the principal possibility of partial or total replacement of the Pt by the Pd on the hydrogen electrode of PEM systems. (authors)

  4. PEM Degradation Investigation Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Dan Stevenson; Lee H Spangler

    2007-11-02

    The objectives of this paper are: (1) Develop a system capable of measuring current and voltage performance for each membrane in a Polymer Electrolyte Membranes (PEM) fuel cell stack and record the performance of each individual cell; (2) Develop a single cell PEM FC to allow in situ synchrotron x-ray measurements of the cell in operation and to perform spatially resolved x-ray measurements on fuel cell elements before and after degradation; and (3) Perform initial magnetic resonance microimaging experiments on membrane materials. The Montana State University PEM Membrane Degradation program is geared towards determining how and why membranes in fuel cells degrade and fail. By monitoring every individual membrane in a fuel cell 2000 times/sec while the cell is subjected to real-world type use, we hope to: (1) cause the types of degradation users see, but in a controlled environment; (2) determine an electrical signature that will identify what causes failure, or at least warns of impending failure; (3) allows us to perform advanced x-ray and MRI characterization of the degraded membranes to provide information that may result in improvements of the membrane material; and (4) perhaps allow design of electronic control systems that will prevent fuel cells from operating under conditions where damage is likely to occur.

  5. Teaching Mass Transfer and Filtration Using Crossflow Reverse Osmosis and Nanofiltration: An Experiment for the Undergraduate Unit Operations Lab

    Science.gov (United States)

    Anastasio, Daniel; McCutcheon, Jeffrey

    2012-01-01

    A crossflow reverse osmosis (RO) system was built for a senior-level chemical engineering unit operations laboratory course. Intended to teach students mass transfer fundamentals related to membrane separations, students tested several commercial desalination membranes, measuring water flux and salt rejections at various pressures, flow rates, and…

  6. Teaching Mass Transfer and Filtration Using Crossflow Reverse Osmosis and Nanofiltration: An Experiment for the Undergraduate Unit Operations Lab

    Science.gov (United States)

    Anastasio, Daniel; McCutcheon, Jeffrey

    2012-01-01

    A crossflow reverse osmosis (RO) system was built for a senior-level chemical engineering unit operations laboratory course. Intended to teach students mass transfer fundamentals related to membrane separations, students tested several commercial desalination membranes, measuring water flux and salt rejections at various pressures, flow rates, and…

  7. Parameterization of electrical equivalent circuits for pem fuel cells; Parametrierung elektrischer Aequivalentschaltbilder von PEM Brennstoffzellen

    Energy Technology Data Exchange (ETDEWEB)

    Haubrock, J.

    2007-12-13

    Fuel cells are a very promising technology for energy conversion. For optimization purpose, useful simulation tools are needs. Simulation tools should simulate the static and dynamic electrical behaviour and the models should parameterized by measurment results which should be done easily. In this dissertation, a useful model for simulating a pem fuel cell is developed. the model should parametrizes by V-I curve measurment and by current step respond. The model based on electrical equivalent circuits and it is shown, that it is possible to simulate the dynamic behaviour of a pem fuel cell stack. The simulation results are compared by measurment results. (orig.)

  8. PEM Fuel Cells with Bio-Ethanol Processor Systems A Multidisciplinary Study of Modelling, Simulation, Fault Diagnosis and Advanced Control

    CERN Document Server

    Feroldi, Diego; Outbib, Rachid

    2012-01-01

    An apparently appropriate control scheme for PEM fuel cells may actually lead to an inoperable plant when it is connected to other unit operations in a process with recycle streams and energy integration. PEM Fuel Cells with Bio-Ethanol Processor Systems presents a control system design that provides basic regulation of the hydrogen production process with PEM fuel cells. It then goes on to construct a fault diagnosis system to improve plant safety above this control structure. PEM Fuel Cells with Bio-Ethanol Processor Systems is divided into two parts: the first covers fuel cells and the second discusses plants for hydrogen production from bio-ethanol to feed PEM fuel cells. Both parts give detailed analyses of modeling, simulation, advanced control, and fault diagnosis. They give an extensive, in-depth discussion of the problems that can occur in fuel cell systems and propose a way to control these systems through advanced control algorithms. A significant part of the book is also given over to computer-aid...

  9. Reverse Mortgage Participation in the United States: Evidence from a National Study

    Directory of Open Access Journals (Sweden)

    Swarn Chatterjee

    2016-03-01

    Full Text Available This paper uses the most recent wave of a nationally representative dataset to examine the factors associated with elderly homeowners’ decision to obtain reverse mortgage loans. The findings of this study suggest that very few homeowners participated in the reverse mortgage market, and homeowners younger than 67 were less likely to have reverse mortgage loans. However, homeowners who were risk averse, and homeowners in the two highest quartiles of net worth were more likely to have reverse mortgage loans. Further analyses reveal that among the reverse mortgage participants, homeowners with long-term care insurance coverage were less likely to have reverse mortgage loans. Implications for financial economists, financial planners, policy-makers, and scholars of retirement economics are included.

  10. Innovation processes of knowledge-based technologies. Example of PEM fuel cell; Innovationsprozesse wissensbasierter Technologien. Beispiel der PEM-Brennstoffzelle

    Energy Technology Data Exchange (ETDEWEB)

    Bertram, Bjoern

    2011-07-01

    Knowledge as distinguished from increasingly crucial factor of production and forms the basis for development of knowledge-based technologies. This study analyzed the example of the PEM fuel cell technology, this innovation process, drawing upon the heuristic of the innovation system. At the same time a detailed picture of the PEM technology as part of the electric mobility is drawn. (orig.)

  11. Characteristics of women in the United States who use long-acting reversible contraceptive methods.

    Science.gov (United States)

    Kavanaugh, Megan L; Jerman, Jenna; Hubacher, David; Kost, Kathryn; Finer, Lawrence B

    2011-06-01

    To examine characteristics of U.S. women that are associated with use of long-acting reversible contraception and changes in these characteristics between 2002 and 2006-2008. We analyzed data from two nationally representative samples of women aged 15-44 in the National Survey of Family Growth, including 7,643 women in 2002 and 7,356 women in 2006-2008. We conducted simple and multinomial logistic regression analyses to identify demographic and reproductive health characteristics associated with use of long-acting reversible contraception. Long-acting reversible contraception (intrauterine devices and subdermal implants) use among U.S. women using contraception increased from 2.4% in 2002 to 5.6% in 2006-2008. The largest increases in long-acting reversible contraception use during this time occurred among the youngest and oldest age groups, non-Hispanic white and non-Hispanic African American women, foreign-born women, and those in the highest income group. High prevalence of long-acting reversible contraception use in 2006-2008 was seen among women who had given birth once or twice (10%), foreign-born women (8.8%), and Hispanic women (8.4%). After adjusting for key demographic and reproductive health characteristics, in comparison with users of other contraceptive methods and with those not using contraception who were at risk for unintended pregnancy, foreign-born women and women who experienced coitarche before age 18 were approximately twice as likely to be using long-acting reversible contraception as women without those characteristics. A more diverse population of women used long-acting reversible contraception in 2006-2008 compared with 2002. However, there is likely more potential for increased uptake, especially among populations historically not considered to be candidates for these methods.

  12. Clear-PEM, a dedicated PET camera for mammography

    CERN Document Server

    Lecoq, P

    2002-01-01

    Preliminary results suggest that Positron Emission Mammography (PEM) can offer a noninvasive method for the diagnosis of breast cancer. Metabolic images from PEM contain unique information not available from conventional morphologic imaging techniques and aid in expeditiously establishing the diagnosis of cancer. A dedicated machine seems to offer better perspectives in terms of position resolution and sensitivity. This paper describes the concept of Clear-PEM, the system presently developed by the Crystal Clear Collaboration at CERN for an evaluation of this approach. This device is based on new crystals introduced by the Crystal Clear as well as on modern data acquisition techniques developed for the large experiments in high energy physics experiments.

  13. Development of PEM fuel cell technology at international fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Wheeler, D.J.

    1996-04-01

    The PEM technology has not developed to the level of phosphoric acid fuel cells. Several factors have held the technology development back such as high membrane cost, sensitivity of PEM fuel cells to low level of carbon monoxide impurities, the requirement to maintain full humidification of the cell, and the need to pressurize the fuel cell in order to achieve the performance targets. International Fuel Cells has identified a hydrogen fueled PEM fuel cell concept that leverages recent research advances to overcome major economic and technical obstacles.

  14. Discordant results from reverse sequence syphilis screening--five laboratories, United States, 2006-2010.

    Science.gov (United States)

    2011-02-11

    CDC recommends syphilis serologic screening with a nontreponemal test, such as the rapid plasma reagin (RPR) or Venereal Disease Research Laboratory (VDRL) test, to identify persons with possible untreated infection; this screening is followed by confirmation using one of several treponemal tests. Recently, the availability of automatable treponemal enzyme and chemiluminescence immunoassays (EIA/CIA) has led some laboratories to adopt a reverse sequence of screening in which a treponemal EIA/CIA is performed first, followed by testing of reactive sera with a nontreponemal test. To better understand the performance of reverse sequence screening for syphilis, CDC analyzed data from five laboratories that used reverse sequence screening during 2006-2010. This report describes the results of that analysis, which indicated that among sera reactive on initial screening with a treponemal EIA/CIA, 56.7% had a nonreactive RPR test. Among these discordant sera, 31.6% also were nonreactive by treponemal testing using Treponema pallidum particle agglutination (TP-PA) or fluorescent treponemal antibody absorbed (FTA-ABS) tests. Among discordant sera, the rate of nonreactive confirmatory treponemal tests was 2.9 times higher in a population with low prevalence of syphilis, suggesting that the low-prevalence population had a higher percentage of false-positive test results. Although CDC continues to recommend the traditional algorithm with reactive nontreponemal tests confirmed by treponemal testing, in this report CDC offers additional recommendations if reverse sequence syphilis screening is used.

  15. Commercializing larger PEM-based hydrogen generators for energy and industrial applications

    Energy Technology Data Exchange (ETDEWEB)

    Moulthrop, L.; Anderson, E.; Chow, O.; Friedland, R.; Porter, S. [Distributed Energy Systems, Wallingford, CT (United States)

    2007-07-01

    As economic, security and environmental drivers converge, there is a demand for larger and better on-site hydrogen generators. This paper outlined the measures needed to scale-up a commercial 12 kg/day proton exchange membrane (PEM) hydrogen generator to a 100 to 500 kg hydrogen per day capacity range. The commercial hydrogen generators using PEM water electrolysis are well proven and currently serve industrial applications worldwide in more than 50 countries. However, North American liquid hydrogen shortages, increasing trucking costs, developing economies with no liquid infrastructure, utilities, and forklift fuel cell fueling applications are all working to increase market demand for commercial on-site hydrogen generation. Water electrolysis was recently identified as the hydrogen technology that will enable solar renewable energy to fill the 17 TW carbon free energy gap projected worldwide by 2050. The scale-up must consider fixed cost as well as operating costs of the electrolyzer and power conditioning, compression and storage ancillaries. It was noted that although commercial applications may be well-satisfied with a 100 kg hydrogen/day PEM hydrogen generator module for the next five years, after that, the 500 kg hydrogen/day module will be required for hydrogen vehicle fueling stations, utility load-leveling, and renewables to hydrogen generation. It was suggested that a paced development effort can be synchronized with evolving fuel cell markets and market price points. The projection of future market price points can be generated using market data and specific cases of the H2A model developed by the United States Department of Energy for electrolysis based fueling. H2A modeling and system analysis identify the components and subsystem development priorities, requirements, and challenges. Codes and standards are maturing to help manufacturers and certification authorities make safe and compliant equipment. It was noted that this development effort is

  16. PEM Water Electrolysis at Elevated Temperatures

    DEFF Research Database (Denmark)

    Hansen, Martin Kalmar

    Global warming and the accelerating depletion of fossil based fuels have catalysed a tremendous surge in the development of alternative and sustainable energy sources e.g. wind-, solar- and hydropower. Common for most of these alternative energy sources is that they at times provide more power than...... needed and hence it has become acute to be able to store the energy. Hydrogen has been identified as a suitable energy carrier and water electrolysis is one way to produce it in a sustainable and environmentally friendly way. In this thesis an introduction to the subject (chapter 1) is given followed...... by a literature review of the field of water electrolysis (chapter 2), with a focus on proton exchange membrane (PEM) electrolysis. In chapter 3 a short description of the experimental techniques used for synthesis of catalyst and characterisation of the components in the electrolysis cell is given...

  17. Reconstruction of Clear-PEM data with STIR

    CERN Document Server

    Martins, M V; Rodrigues, P; Trindade, A; Oliveira, N; Correia, M; Cordeiro, H; Ferreira, N C; Varela, J; Almeida, P

    2006-01-01

    The Clear-PEM scanner is a device based on planar detectors that is currently under development within the Crystal Clear Collaboration, at CERN. The basis for 3D image reconstruction in Clear-PEM is the software for tomographic image reconstruction (STIR). STIR is an open source object-oriented library that efficiently deals with the 3D positron emission tomography data sets. This library was originally designed for the traditional cylindrical scanners. In order to make its use compatible with planar scanner data, new functionalities were introduced into the library's framework. In this work, Monte Carlo simulations of the Clear-PEM scanner acquisitions were used as input for image reconstruction with the 3D OSEM algorithm available in STIR. The results presented indicate that dual plate PEM data can be accurately reconstructed using the enhanced STIR framework.

  18. Flow field design for high-pressure PEM electrolysis cells

    DEFF Research Database (Denmark)

    Olesen, Anders Christian; Kær, Søren Knudsen

    With the increasing interest in producing hydrogen through water electrolysis, the importance of understanding the transport phenomena governing its operation increases. To ensure optimal operating conditions for PEM electrolysis, it is particularly important to understand how the liquid feed...

  19. Novel High Temperature Membrane for PEM Fuel Cells Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The innovation proposed in this STTR program is a high temperature membrane to increase the efficiency and power density of PEM fuel cells. The NASA application is...

  20. Exergy analysis of the woody biomass Stirling engine and PEM-FC combined system with exhaust heat reforming

    Energy Technology Data Exchange (ETDEWEB)

    Obara, Shin' ya; Tanno, Itaru [Department of Mechanical Engineering, Tomakomai National College of Technology, 443 Nishikioka, Tomakomai, Hokkaido 0591275 (Japan); Kito, Shunsuke [Department of Mechanical Engineering, Toyota National College of Technology, Eisei-cho, 2-1 Toyota, Aichi 4718525 (Japan); Hoshi, Akira; Sasaki, Seizi [Department of Mechanical Engineering, Ichinoseki National College of Technology, Takanashi, Hagisho, Ichinoseki, Iwate 0218511 (Japan)

    2008-05-15

    The woody biomass Stirling engine (WB-SEG) is an external combustion engine that outputs high-temperature exhaust gases. It is necessary to improve the exergy efficiency of WB-SEG from the viewpoint of energy cascade utilization. So, a combined system that uses the exhaust heat of WB-SEG for the steam reforming of city gas and that supplies the produced reformed gas to a proton exchange membrane fuel cell (PEM-FC) is proposed. The energy flow and the exergy flow were analyzed for each WB-SEG, PEM-FC, and WB-SEG/PEM-FC combined system. Exhaust heat recovery to preheat fuel and combustion air was investigated in each system. As a result, (a) improvement of the heat exchange performance of the woody biomass combustion gas and engine is observed, (b) reduction in difference in the reaction temperature of each unit, and (c) removal of rapid temperature change of reformed gas are required in order to reduce exergy loss of the system. The exergy efficiency of the WB-SEG/PEM-FC combined system is superior to EM-FC. (author)

  1. Intergovernmental Advanced Stationary PEM Fuel Cell System Demonstration Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Rich Chartrand

    2011-08-31

    A program to complete the design, construction and demonstration of a PEMFC system fuelled by Ethanol, LPG or NG for telecom applications was initiated in October 2007. Early in the program the economics for Ethanol were shown to be unfeasible and permission was given by DOE to focus on LPG only. The design and construction of a prototype unit was completed in Jun 2009 using commercially available PEM FC stack from Ballard Power Systems. During the course of testing, the high pressure drop of the stack was shown to be problematic in terms of control and stability of the reformer. Also, due to the power requirements for air compression the overall efficiency of the system was shown to be lower than a similar system using internally developed low pressure drop FC stack. In Q3 2009, the decision was made to change to the Plug power stack and a second prototype was built and tested. Overall net efficiency was shown to be 31.5% at 3 kW output. Total output of the system is 6 kW. Using the new stack hardware, material cost reduction of 63% was achieved over the previous Alpha design. During a November 2009 review meeting Plug Power proposed and was granted permission, to demonstrate the new, commercial version of Plug Power's telecom system at CERL. As this product was also being tested as part of a DOE Topic 7A program, this part of the program was transferred to the Topic 7A program. In Q32008, the scope of work of this program was expanded to include a National Grid demonstration project of a micro-CHP system using hightemperature PEM technology. The Gensys Blue system was cleared for unattended operation, grid connection, and power generation in Aug 2009 at Union College in NY state. The system continues to operate providing power and heat to Beuth House. The system is being continually evaluated and improvements to hardware and controls will be implemented as more is learned about the system's operation. The program is instrumental in improving the

  2. Bootstrapping a Sustainable North American PEM Fuel Cell Industry: Could a Federal Acquisition Program Make a Difference?

    Energy Technology Data Exchange (ETDEWEB)

    Greene, David L [ORNL; Duleep, Dr. K. G. [Energy and Environmental Analysis, Inc., an ICF Company

    2008-10-01

    The North American Proton Exchange Membrane (PEM) fuel cell industry may be at a critical juncture. A large-scale market for automotive fuel cells appears to be several years away and in any case will require a long-term, coordinated commitment by government and industry to insure the co-evolution of hydrogen infrastructure and fuel cell vehicles (Greene et al., 2008). The market for non-automotive PEM fuel cells, on the other hand, may be much closer to commercial viability (Stone, 2006). Cost targets are less demanding and manufacturers appear to be close, perhaps within a factor of two, of meeting them. Hydrogen supply is a significant obstacle to market acceptance but may not be as great a barrier as it is for hydrogen-powered vehicles due to the smaller quantities of hydrogen required. PEM fuel cells appear to be potentially competitive in two markets: (1) Backup power (BuP) supply, and (2) electrically-powered MHE (Mahadevan et al., 2007a, 2007b). There are several Original Equipment Manufacturers (OEMs) of PEM fuel cell systems for these applications but production levels have been quite low (on the order of 100-200 per year) and cumulative production experience is also limited (on the order of 1,000 units to date). As a consequence, costs remain above target levels and PEM fuel cell OEMs are not yet competitive in these markets. If cost targets can be reached and acceptable solutions to hydrogen supply found, a sustainable North American PEM fuel cell industry could be established. If not, the industry and its North American supply chain could disappear within a year or two. The Hydrogen Fuel Cell and Infrastructure Technologies (HFCIT) program of the U.S. Department of Energy (DOE) requested a rapid assessment of the potential for a government acquisition program to bootstrap the market for non-automotive PEM fuel cells by driving down costs via economies of scale and learning-by-doing. The six week study included in-depth interviews of three manufacturers

  3. Performance of landfill leachate treatment system with disc-tube reverse osmosis units

    Institute of Scientific and Technical Information of China (English)

    Yanping LIU; Xiujin LI; Baozhen WANG; Shuo LIU

    2008-01-01

    Reverse osmosis system with the disc-tube module (DT-RO) was applied to treat landfill leachate on full scale at the Changshengqiao Sanitary Landfill, Chongqing City, China. In the first six-mouth operation phase, the treatment performance of DT-RO system had been excel-lent and stable. The removal rate of chemical oxygen demand (COD), total organic carbon (TOC), electrical con-ductivity (EC), and ammonia nitrogen (NH3-N) reached 99.2-99.7%, 99.2%, 99.6%, and over 98%, respectively. The rejection of Ca2+,Ba2+, and Mg2+ was over 99.9%, respectively. Suspended solid (SS) was not detected in prod-uct water. Effective methods had been adopted to control membrane fouling, of which chemical cleaning is of utmost importance to guarantee the long smooth operation of the DT-RO system. The DT-RO system is cleaned in turns with Cleaner A and Cleaner C. At present, the 1st stage cleaning cycle by Cleaner A and Cleaner C is conducted every 100 and 500 h, respectively, depending on raw the water quality.

  4. A New Control and Design of PEM Fuel Cell System Powered Diffused Air Aeration System

    Directory of Open Access Journals (Sweden)

    Ninet M. Ahmed

    2012-06-01

    Full Text Available The goal of aquaculture ponds is to maximize production and profits while holding labor and management efforts to the minimum. Poor water quality in most ponds causes risk of fish kills, disease outbreaks which lead to minimization of pond production. Dissolved Oxygen (DO is considered to be among the most important water quality parameters in fish culture. Fish ponds in aquaculture farms are usually located in remote areas where grid lines are at far distance. Aeration of ponds is required to prevent mortality and to intensify production, especially when feeding is practical, and in warm regions. To increase pond production it is necessary to control dissolved oxygen. Aeration offers the most immediate and practical solution to water quality problems encountered at higher stocking and feeding rates. Many units of aeration system are electrical units so using a continuous, high reliability, affordable, and environmentally friendly power sources is necessary. Fuel cells have become one of the major areas of research in the academia and the industry. Aeration of water by using PEM fuel cell power is not only a new application of the renewable energy, but also, it provides an affordable method to promote biodiversity in stagnant ponds and lakes. This paper presents a new design and control of PEM fuel cell powered a diffused air aeration system for a shrimp farm in Mersa Matruh in Egypt. Also Artificial intelligence (AI control techniques are used to control the fuel cell output power by controlling its input gases flow rate. Moreover the mathematical modeling and simulation of PEM fuel cell is introduced. A comparative study is applied between the performance of fuzzy logic controller (FLC and neural network controller (NNC. The results show the effectiveness of NNC over FLC.

  5. A New Control and Design of PEM Fuel Cell System Powered Diffused Air Aeration System

    Directory of Open Access Journals (Sweden)

    Hassen T. Dorrah

    2012-06-01

    Full Text Available The goal of aquaculture ponds is to maximize production and profits while holding labor and management efforts to the minimum. Poor water quality in most ponds causes risk of fish kills, disease outbreaks which lead to minimization of pond production. Dissolved Oxygen (DO is considered to be among the most important water quality parameters in fish culture. Fish ponds in aquaculture farms are usually located in remote areas where grid lines are at far distance. Aeration of ponds is required to prevent mortality and to intensify production, especially when feeding is practical, and in warm regions. To increase pond production it is necessary to control dissolved oxygen. Aeration offers the most immediate and practical solution to water quality problems encountered at higher stocking and feeding rates. Many units of aeration system are electrical units so using a continuous, high reliability, affordable, and environmentally friendly power sources is necessary. Fuel cells have become one of the major areas of research in the academia and the industry. Aeration of water by using PEM fuel cell power is not only a new application of the renewable energy, but also, it provides an affordable method to promote biodiversity in stagnant ponds and lakes. This paper presents a new design and control of PEM fuel cell powered a diffused air aeration system for a shrimp farm in Mersa Matruh in Egypt. Also Artificial intelligence (AI control techniques are used to control the fuel cell output power by controlling its input gases flow rate. Moreover the mathematical modeling and simulation of PEM fuel cell is introduced. A comparative study is applied between the performance of fuzzy logic controller (FLC and neural network controller (NNC. The results show the effectiveness of NNC over FLC.

  6. Performance optimization of a PEM hydrogen-oxygen fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Sadiq Al-Baghdadi, Maher A.R. [Fuel Cell Research Center, International Energy and Environment Foundation, Al-Najaf, P.O.Box 39 (Iraq)

    2013-07-01

    The objective was to develop a semi-empirical model that would simulate the performance of proton exchange membrane (PEM) fuel cells without extensive calculations. A fuel cell mathematical module has been designed and constructed to determine the performance of a PEM fuel cell. The influence of some operating parameters on the performance of PEM fuel cell has been investigated using pure hydrogen on the anode side and oxygen on the cathode side. The present model can be used to investigate the influence of process variables for design optimization of fuel cells, stacks, and complete fuel cell power system. The possible mechanisms of the parameter effects and their interrelationships are discussed. In order to assess the validity of the developed model a real PEM fuel cell system has been used to generate experimental data. The comparison shows good agreements between the modelling results and the experimental data. The model is shown a very useful for estimating the performance of PEM fuel cell stacks and optimization of fuel cell system integration and operation.

  7. Improvement of dose distribution in breast radiotherapy using a reversible transverse magnetic field Linac-MR unit

    Energy Technology Data Exchange (ETDEWEB)

    Esmaeeli, A. D., E-mail: ali-esmaeeli-d@yahoo.com [Department of Physics, Rasht Branch, Islamic Azad University, Rasht, 41476-54919 (Iran, Islamic Republic of); Mahdavi, S. R. [Department of Medical Physics, Tehran University of Medical Sciences, Tehran, 14174 (Iran, Islamic Republic of); Pouladian, M.; Bagheri, S. [Department of Medical Radiation Engineering, Science and Research Branch, Islamic Azad University, Tehran, 14778-93855 (Iran, Islamic Republic of); Monfared, A. S. [Department of Medical Physics, Babol University of Medical Sciences, Babol, 47148-71167 (Iran, Islamic Republic of)

    2014-01-15

    Purpose: To investigate the improvement in dose distribution in tangential breast radiotherapy using a reversible transverse magnetic field that maintains the same direction of Lorentz force between two fields. The investigation has a potential application in future Linac-MR units. Methods: Computed tomography images of four patients and magnetic fields of 0.25–1.5 Tesla (T) were used for Monte Carlo simulation. Two patients had intact breast while the other two had mastectomy. Simulations of planning and chest wall irradiation were similar to the actual clinical process. The direction of superior-inferior magnetic field for the medial treatment beam was reversed for the lateral beam. Results: For the ipsilateral lung and heart mean doses were reduced by a mean (range) of 45.8% (27.6%–58.6%) and 26.0% (20.2%–38.9%), respectively, depending on various treatment plan setups. The mean V{sub 20} for ipsilateral lung was reduced by 55.0% (43.6%–77.3%). In addition acceptable results were shown after simulation of 0.25 T magnetic field demonstrated in dose-volume reductions of the heart, ipsilateral lung, and noninvolved skin. Conclusions: Applying a reversible magnetic field during breast radiotherapy, not only reduces the dose to the lung and heart but also produces a sharp drop dose volume histogram for planning target volume, because of bending of the path of secondary charged particles toward the chest wall by the Lorentz force. The simulations have shown that use of the magnetic field at 1.5 T is not feasible for clinical applications due to the increase of ipsilateral chest wall skin dose in comparison to the conventional planning while 0.25 T is suitable for all patients due to dose reduction to the chest wall skin.

  8. Phase coexistence calculations via a unit-cell Gibbs ensemble formalism for melts of reversibly bonded block copolymers

    Science.gov (United States)

    Mester, Zoltan; Lynd, Nathaniel; Fredrickson, Glenn

    2013-03-01

    Melts of block copolymer blends can exhibit coexistence between compositionally and morphologically distinct phases. We derived a unit-cell approach for a field theoretic Gibbs ensemble formalism to rapidly map out such coexistence regions. We also developed a canonical ensemble model for the reversible reaction of supramolecular polymers and integrated it into the Gibbs ensemble scheme. This creates a faster method for generating phase diagrams in complex supramolecular systems than the usual grand canonical ensemble method and allows us to specify the system in experimentally accessible volume fractions rather than chemical potentials. The integrated approach is used to calculate phase diagrams for AB diblock copolymers reversibly reacting with B homopolymers to form a new diblocks we term ``ABB.'' For our case, we use a diblock that is sixty percent A monomer and a homopolymer that is the same length as the diblock. In the limits of infinite reaction favorability (large equilibrium constant), the system approaches cases of an ABB diblock-B homopolymer blend when the AB diblock is the limiting reactant and AB diblock-ABB diblock blend when the homopolymer is the limiting reactant. As reaction favorability is decreased, the phase boundaries shift towards higher homopolymer compositions so that sufficient reaction can take place to produce the ABB diblock that has a deciding role stabilizing the observed phases.

  9. Analysis of a Wave-Powered, Reverse-Osmosis System and Its Economic Availability in the United States: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Yi-Hsiang [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Jenne, Dale S [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2017-08-09

    A wave energy converter (WEC) system has the potential to convert the wave energy resource directly into the high-pressure flow that is needed by the desalination system to permeate saltwater through the reverse-osmosis membrane to generate clean water. In this study, a wave-to-water numerical model was developed to investigate the potential use of a wave-powered desalination system (WPDS) for water production in the United States. The model was developed by coupling a time-domain radiation-and-diffraction-method-based numerical tool (WEC-Sim) for predicting the hydrodynamic performance of WECs with a solution-diffusion model that was used to simulate the reverse-osmosis process. To evaluate the feasibility of the WPDS, the wave-to-water numerical model was applied to simulate a desalination system that used an oscillating surge WEC device to pump seawater through the system. The annual water production was estimated based on the wave resource at a reference site on the coast of northern California to investigate the potential cost of water in that area, where the cost of water and electricity is high compared to other regions. In the scenario evaluated, for a 100-unit utility-scale electricity-producing array, the estimated levelized cost of energy for these WECs is about 3-6 times the U.S.'s current, unsubsidized electricity rates. However, with clean water as an end product and by directly producing pressurized water with WECs, rather than electricity as an intermediary, it is presently only 12 percent greater than typical water cost in California. This study suggests that a WEC array that produces water may be a viable, near-term solution to the nation's water supply, and the niche application of the WPDS may also provide developers with new opportunities to further develop technologies that benefit both the electric and drinking water markets.

  10. PEM Low Cost Endplates. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Nielsen, Martin; Clyens, S.; Steenstrup, F.R.; Christiansen, Jens [Danish Technological Institute. Plastics Technology, Taastrup (Denmark); Yde-Andersen, S. [IRD Fuel Cell A/S, Svendborg (Denmark)

    2013-03-15

    In the project, an endplate for the PEM-type fuel cells has been developed. The initial idea was to use an injection mouldable fibre reinforced polymer to produce the endplate and thereby exploit the opportunities of greater geometrical freedom to reduce weight and material consumption. Different PPS/glass-fibre compounds were produced and tested in order to use the results to optimize the results on the computer through FEM simulations. As it turned out, it was impossible to achieve adequate stiffness for the endplates within the given geometrical limitations. At the relatively high temperatures at which the endplates operate the material simply goes to soft. Material focus shifted to fibre reinforced high strength concrete composite. Test specimens were produced and tested so the results again could be used for FEM-simulations which also accounted for the technical limitations the concrete composite has regarding casting ability. In the process, the way the endplate is mounted was also alternated to better accommodate the properties of the concrete composite. A number of endplates were cast in specially produced moulds in order to map the optimum process parameters, and a final endplate was tested at IRD Fuel Cells A/S. The field test was in many aspects successful. However, the gas sealing and the surface finish can be further improved. The weight may still be an issue for some applications, even though it is lower than the endplate currently used. This issue can be addressed in a future project. The work has resulted in a new endplate design, which makes the stack assembly simpler and with fewer components. The endplates fabrication involves low cost methods, which can be scaled up as demand of fuel cells begin to take off. (Author)

  11. Device and materials modeling in PEM fuel cells

    CERN Document Server

    Promislow, Keith

    2009-01-01

    Device and Materials Modeling in PEM Fuel Cells is a specialized text that compiles the mathematical details and results of both device and materials modeling in a single volume. Proton exchange membrane (PEM) fuel cells will likely have an impact on our way of life similar to the integrated circuit. The potential applications range from the micron scale to large scale industrial production. Successful integration of PEM fuel cells into the mass market will require new materials and a deeper understanding of the balance required to maintain various operational states. This book contains articles from scientists who contribute to fuel cell models from both the materials and device perspectives. Topics such as catalyst layer performance and operation, reactor dynamics, macroscopic transport, and analytical models are covered under device modeling. Materials modeling include subjects relating to the membrane and the catalyst such as proton conduction, atomistic structural modeling, quantum molecular dynamics, an...

  12. Data acquisition electronics for positron emission mammography (PEM) detectors

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, J.D. [Digital Systems Design Group, Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain)]. E-mail: jormarp1@doctor.upv.es; Sebastia, A. [Digital Systems Design Group, Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain); Cerda, J. [Digital Systems Design Group, Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain); Esteve, R. [Digital Systems Design Group, Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain); Mora, F.J. [Digital Systems Design Group, Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain); Toledo, J.F. [Digital Systems Design Group, Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain); Benlloch, J.M. [Nuclear Medical Physics Group, Instituto de Fisica Corpuscular (CSIC-UV), Poligono de la Coma s/n, 46980 Paterna, Valencia (Spain); Gimenez, N. [Nuclear Medical Physics Group, Instituto de Fisica Corpuscular (CSIC-UV), Poligono de la Coma s/n, 46980 Paterna, Valencia (Spain); Gimenez, M. [Nuclear Medical Physics Group, Instituto de Fisica Corpuscular (CSIC-UV), Poligono de la Coma s/n, 46980 Paterna, Valencia (Spain); Lerche, Ch. W. [Nuclear Medical Physics Group, Instituto de Fisica Corpuscular (CSIC-UV), Poligono de la Coma s/n, 46980 Paterna, Valencia (Spain); Pavon, N. [Nuclear Medical Physics Group, Instituto de Fisica Corpuscular (CSIC-UV), Poligono de la Coma s/n, 46980 Paterna, Valencia (Spain); Sanchez, F. [Nuclear Medical Physics Group, Instituto de Fisica Corpuscular (CSIC-UV), Poligono de la Coma s/n, 46980 Paterna, Valencia (Spain)

    2005-01-21

    Positron emission mammography (PEM) is an innovative technique to increase sensitivity and overcome the main drawbacks of conventional X-ray screening. However, dedicated PET imaging systems demand specific hardware solutions for data acquisition and processing that can take advantage of the reduction in the number of channels. Data acquisition issues can affect PEM scanners performance and they should be exhaustively addressed in order to exploit the increment in the event count rate. This is crucial in order to reduce both the scanning time and the total injected dose. This paper presents the electronics for our PEM camera prototype that enables us to achieve very high-count rates and perform comprehensive online processing. Results about acquisition in our detector for a typical clinical setup are studied using Monte Carlo simulation of hot lesion phantoms.

  13. Materials Challenges for Automotive PEM Fuel Cells

    Science.gov (United States)

    Gasteiger, Hubert

    2004-03-01

    Over the past few years, significant R efforts aimed at meeting the challenging cost and performance targets required for the use of Polymer Electrolyte Membrane (PEM) fuel cells in automotive applications. Besides engineering advances in bipolar plate materials and design, the optimization of membrane-electrode assemblies (MEAs) was an important enabler in reducing the cost and performance gaps towards commercial viability for the automotive market. On the one hand, platinum loadings were reduced from several mgPt/cm2MEA [1] to values of 0.5-0.6 mgPt/cm2MEA in current applications and loadings as low as 0.25 mgPt/cm2MEA have been demonstrated on the research level [2]. On the other hand, implementation of thin membranes (20-30 micrometer) [3, 4] as well as improvements in diffusion medium materials, essentially doubled the achievable power density of MEAs to ca. 0.9 W/cm2MEA (at 0.65 V) [5], thereby not only reducing the size of a PEMFC fuel cell system, but also reducing its overall materials cost (controlled to a large extent by membrane and Pt-catalyst cost). While this demonstrated a clear path towards automotive applications, a renewed focus of R efforts is now required to develop materials and fundamental materials understanding to assure long-term durability of PEM fuel cells. This presentation therefore will discuss the state-of-the-art knowledge of catalyst, catalyst-support, and membrane degradation mechanisms. In the area of Pt-catalysts, experience with phosphoric acid fuel cells (PAFCs) has shown that platinum sintering leads to long-term performance losses [6]. While this is less critical at the lower PEMFC operating temperatures (200C), very little is known about the dependence of Pt-sintering on temperature, cell voltage, and catalyst type (i.e., Pt versus Pt-alloys) and will be discussed here. Similarly, carbon-support corrosion can contribute significantly to voltage degradation in PAFCs [7], and even in the PEMFC environment more corrosion

  14. High Temperature PEM Fuel Cell Systems, Control and Diagnostics

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Kær, Søren Knudsen; Justesen, Kristian Kjær

    2015-01-01

    Various system topologies are available when it comes to designing high temperature PEM fuel cell systems. Very simple system designs are possible using pure hydrogen, and more complex system designs present themselves when alternative fuels are desired, using reformer systems. The use of reformed...... fuels utilizes one of the main advantages of the high temperature PEM fuel cell: robustness to fuel quality and impurities. In order for such systems to provide efficient, robust, and reliable energy, proper control strategies are needed. The complexity and nonlinearity of many of the components...

  15. PEM fuel cell modeling and simulation using Matlab

    CERN Document Server

    Spiegel, Colleen

    2011-01-01

    Although, the basic concept of a fuel cell is quite simple, creating new designs and optimizing their performance takes serious work and a mastery of several technical areas. PEM Fuel Cell Modeling and Simulation Using Matlab, provides design engineers and researchers with a valuable tool for understanding and overcoming barriers to designing and building the next generation of PEM Fuel Cells. With this book, engineers can test components and verify designs in the development phase, saving both time and money.Easy to read and understand, this book provides design and modelling tips for

  16. Detailed experimental characterization of a reformate fuelled PEM stack

    DEFF Research Database (Denmark)

    Korsgaard, Anders; Nielsen, Mads Pagh; Kær, Søren Knudsen

    2006-01-01

    Increasing attention is given to fuel cells for micro combined heat and power systems for local households. Currently, mainly three different types of fuel cells are commercially competitive: SOFC, low- and high-temperature PEM fuel cells. In the present paper the Low Temperature PEM technology...... performance and process input variations need to be carefully accounted for. Such data will additionally provide valuable input for system modeling and optimization. The paper presents an advanced experimental test facility capable of performing static as well as dynamic tests on fuel cell stacks...

  17. Advanced catalyst supports for PEM fuel cell cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Du, Lei; Shao, Yuyan; Sun, Junming; Yin, Geping; Liu, Jun; Wang, Yong

    2016-11-01

    Electrocatalyst support materials are key components for polymer exchange membrane (PEM) fuel cells, which play a critical role in determining electrocatalyst durability and activity, mass transfer and water management. The commonly-used supports, e.g. porous carbon black, cannot meet all the requirements under the harsh operation condition of PEM fuel cells. Great efforts have been made in the last few years in developing alternative support materials. In this paper, we selectively review recent progress on three types of important support materials: carbon, non-carbon and hybrid carbon-oxides nanocomposites. A perspective on future R&D of electrocatalyst support materials is also provided.

  18. System Design of a Natural Gas PEM Fuel Cell Power Plant for Buildings

    Energy Technology Data Exchange (ETDEWEB)

    Joe Ferrall, Tim Rehg, Vesna Stanic

    2000-09-30

    The following conclusions are made based on this analysis effort: (1) High-temperature PEM data are not available; (2) Stack development effort for Phase II is required; (3) System results are by definition preliminary, mostly due to the immaturity of the high-temperature stack; other components of the system are relatively well defined; (4) The Grotthuss conduction mechanism yields the preferred system characteristics; the Grotthuss conduction mechanism is also much less technically mature than the vehicle mechanism; (5) Fuel processor technology is available today and can be procured for Phase II (steam or ATR); (6) The immaturity of high-temperature membrane technology requires that a robust system design be developed in Phase II that is capable of operating over a wide temperature and pressure range - (a) Unpressurized or Pressurized PEM (Grotthuss mechanism) at 140 C, Highest temperature most favorable, Lowest water requirement most favorable, Pressurized recommended for base loaded operation, Unpressurized may be preferred for load following; (b) Pressurized PEM (vehicle mechanism) at about 100 C, Pressure required for saturation, Fuel cell technology currently available, stack development required. The system analysis and screening evaluation resulted in the identification of the following components for the most promising system: (1) Steam reforming fuel processor; (2) Grotthuss mechanism fuel cell stack operating at 140 C; (3) Means to deliver system waste heat to a cogeneration unit; (4) Pressurized system utilizing a turbocompressor for a base-load power application. If duty cycling is anticipated, the benefits of compression may be offset due to complexity of control. In this case (and even in the base loaded case), the turbocompressor can be replaced with a blower for low-pressure operation.

  19. Comparison of scintillators for positron emission mammography (PEM) systems

    Energy Technology Data Exchange (ETDEWEB)

    Raymond Raylman; Stanislaw Majewski; Mark Smith; Randolph Wojcik; Andrew Weisenberger; Brian Kross; Vladimir Popov; Jamal J. Derakhshan

    2003-02-01

    Positron emission mammography (PEM) has promise as an effective method for the detection of breast lesions. Perhaps the most significant design feature of a PEM system is the choice of scintillator material. In this investigation we compared three scintillators for use in PEM: NaI(Tl), gadolinium oxyorthosilicate (GSO), and lutetium-gadolinium oxyorthosilicate (LGSO). The PEM systems consisted of two 30/spl times/30 arrays of pixelated scintillators (3/spl times/3/spl times/10 mm/sup 3/ for GSO and LGSO and 3/spl times/3/spl times/19 mm/sup 3/ for NaI(Tl)) coupled to arrays of square position-sensitive photomultiplier tubes. The Compton scatter fraction, system energy resolution, spatial resolution, spatial resolution uniformity, and detection sensitivity were compared. Compton scatter fractions for the systems were comparable, between 8% and 9%. The NaI(Tl) system produced the best system energy resolution (18.2%), the GSO system had the worst system energy resolution (28.7%).

  20. A Two-Dimensional PEM Fuel Cell Model

    Science.gov (United States)

    Shi, Zhongying; Wang, Xia; Zhang, Zhuqian

    2006-11-01

    Proton Exchange Membrane (PEM) fuel cell is a typical low temperature cell, where hydrogen and air are fed into the porous anodic electrode and cathodic electrode though the gas distributors on the bipolar plates, respectively. Activated by the catalyst on anode side, hydrogen will spilt into protons and electrons. Since only protons will be allowed to pass through the membrane, electrons must go through an external circuit. Electrons and protons meet air on cathode side to produce water and heat catalyzed by the catalyst on the cathode side. Numerical simulations are useful tools to describe the basic transport and electrochemical phenomena of PEM fuel cells. The goal of the present work is to develop 2-D computational models of PEM fuel cells, which take into account fluid flow, multi- species transport, current distribution and electrical potential. The velocity field in free channel described by Navier-Stokes equation and the velocity field in porous media described by Darcy’s Law are coupled along the channel-MEA interface. The governing differential equations are solved over a single computational domain, which consists of two gas channel layers, two gas diffusion layers, two catalyst layers as well as a membrane. The model is solved with commercial software COMSOL Multiphysics 3.2b. Parametric study will be conducted to analyze the effects of various parameters on the performance of PEM fuel cells. The results, including the mass concentration, the polarization curve and the velocity distribution, will be presented.

  1. ClearPEM: prototype PET device dedicated to breast imaging

    CERN Multimedia

    Joao Varela

    2009-01-01

    Clinical trials have begun in Portugal on a new breast imaging system (ClearPEM) using positron emission tomography (PET). The system, developed by a Portuguese consortium in collaboration with CERN and laboratories participating in the Crystal Clear collaboration, will detect even the smallest tumours and thus help avoid unnecessary biopsies.

  2. Development of Novel PEM Membrane and Multiphase CD Modeling of PEM Fuel Cell

    Energy Technology Data Exchange (ETDEWEB)

    K. J. Berry; Susanta Das

    2009-12-30

    To understand heat and water management phenomena better within an operational proton exchange membrane fuel cell's (PEMFC) conditions, a three-dimensional, two-phase computational fluid dynamic (CFD) flow model has been developed and simulated for a complete PEMFC. Both liquid and gas phases are considered in the model by taking into account the gas flow, diffusion, charge transfer, change of phase, electro-osmosis, and electrochemical reactions to understand the overall dynamic behaviors of species within an operating PEMFC. The CFD model is solved numerically under different parametric conditions in terms of water management issues in order to improve cell performance. The results obtained from the CFD two-phase flow model simulations show improvement in cell performance as well as water management under PEMFCs operational conditions as compared to the results of a single phase flow model available in the literature. The quantitative information obtained from the two-phase model simulation results helped to develop a CFD control algorithm for low temperature PEM fuel cell stacks which opens up a route in designing improvement of PEMFC for better operational efficiency and performance. To understand heat and water management phenomena better within an operational proton exchange membrane fuel cell's (PEMFC) conditions, a three-dimensional, two-phase computational fluid dynamic (CFD) flow model has been developed and simulated for a complete PEMFC. Both liquid and gas phases are considered in the model by taking into account the gas flow, diffusion, charge transfer, change of phase, electro-osmosis, and electrochemical reactions to understand the overall dynamic behaviors of species within an operating PEMFC. The CFD model is solved numerically under different parametric conditions in terms of water management issues in order to improve cell performance. The results obtained from the CFD two-phase flow model simulations show improvement in cell

  3. Use of biogas in PEM fuel cells; Einsatz von Biogas in PEM-Brennstoffzellen

    Energy Technology Data Exchange (ETDEWEB)

    Scholz, Volkhard; Schmersahl, Ralf; Ellner, Janine (comps.)

    2009-06-15

    This research project was dedicated to two problems: 1. What demands must biogas meet in order to conform to the specifications of PEM fuel cell systems and permit safe operation? 2. How must a fuel cell system be designed and operated in order to be well-adapted to the special features of biogas as opposed to natural gas? For this purpose biogas samples were taken from laboratory-scale and commercial plants and analysed by gas chromatography using various substrates and methods. By combining this with the use of a mass spectroscopy detector (GC-MS system) it was possible to perform a qualitative and quantitative analysis of sulphurious trace gases in the biogas which might cause damage to the fuel cell system. Investigations were performed on an experimental reformer using either modelled or native biogas of different compositions, the intent being to obtain information for the design of the individual process stages. The two operating parameters steam-methane ratio (or S/C ratio) and reforming temperature were varied to optimise parameter settings in terms of energy efficiency. By linking the reformer to a 500 W fuel cell it was possible confirm the suitability of the reformed biogas for use in fuel cells. [German] In diesm Forschungsvorhaben werden zwei Fragestellungen bearbeitet: 1. Welche Anforderungen ergeben sich an das Biogas, um den Spezifikationen von PEM-Brennstoffzellensystemen zu genuegen und eine sicheren Betrieb zu ermoeglichen? 2. Wie muss das Brennstoffzellensystem ausgelegt und gefuehrt werden, um den Besonderheiten von Biogas im Vergleich zu Erdgas Rechnung zu tragen? Dazu wurden Biogasproben aus Labor- und Praxisanlagen unter Beruecksichtigung unterschiedlicher Substrate und Verfahren gaschromatisch analysiert. Die Kopplung mit einem massenspektroskopischen Detektor (GC-MS System) ermoeglicht dabei die Qualifizierung und Quantifizierung der vorhandenen schwefelhaltigen Spurengase, die eine Schaedigung von Brennstoffzellenanlagen verursachen. Die

  4. Quantify and improve PEM fuel cell durability. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Grahl-Madsen, L.; Odgaard, M.; Munksgaard Nielsen, R. (IRD Fuel Cell A/S, Svendborg (Denmark)); Li, Q.; Jensen, Jens Oluf (Technical Univ. of Denmark, Dept. of Chemistry, Kgs. Lyngby (Denmark)); Andersen, Shuang Ma; Speder, J.; Skou, E. (Syddansk Univ. (SDU), Odense (Denmark))

    2010-07-01

    The aim of the present project is to systematically quantify and improve the durability of the PEM FC including the following three PEM FC variants: LT PEM FC, DMFC, and HT PEM FC. Different factors influencing dissolution properties of noble metal catalyst platinum and platinum-ruthenium alloy has been studied. The dissolution was found to increase by increasing the CV cycle upper potential limit, number of potential cycles, solution acidity, oxygen partial pressure, involvement of chloride, and temperature. Ruthenium was found to deteriorate ten (10) times faster than platinum catalyst; and carbon supported catalyst (Pt: 20%, Ru: up to 100%) deteriorate ten (10) times faster than non-supported catalyst (Pt: 2%, Ru: 30%) at the same condition. Loss of sulphonic acid groups and fluoride from perfluorinated sulfonic acid membrane was confirmed by different techniques, which locally leads to loss of acidity, and consequently enhances dissolution of noble metal catalyst. Degradation of Nafion ionomer in the electrode was enhanced by noble metal catalyst and the thermal decomposition properties has synergetic effect with carbon degradation. Hydrophobicity of GDL and electrode on GDL were found to degrade e.g. radical attack, oxidation, and physical wear out. The very top micro surface structure turned out to be responsible for wetting property after chemical ageing. Optimal catalyst and ionomer ratio is also reflected in contact angle value, which can be understood in terms of catalyst/carbon - ionomer affinity and layered structure. Long-term tested and 'virgin' LT PEM MEAs have been characterised with respect to SEM, TEM, EDS, and XRD. Both failed and well-functioning MEAs have been characterised. The Post Mortem analysis has shown and quantified degradation mechanisms like catalyst growth and carbon corrosion. Furthermore, the effect of fuel starvation was shown by pronounced Ru-catalyst band within the membrane. The catalyst coarsening observed after

  5. Thermal signature and thermal conductivities of PEM fuel cells; PEM = Proton Exchange Membrane

    Energy Technology Data Exchange (ETDEWEB)

    Burheim, Odne Stokke

    2009-11-15

    The work gives estimates on thermal gradients within the PEM fuel cell, an experimental route to measure the through-plane thermal conductivity of the materials used in the PEM fuel cell and also suggestions of which material characteristics should be aimed for with respect to thermal management of fuel cells. The work reports for the first time how the thermal conductivity of Nafion changes with water content. An effect residual water has on the thermal conductivity of the PTL is also reported for the first time. In addition to this a calorimeter for the PEMFC was constructed to measure the thermal signature. This is also reported for the first time in the literature. To elucidate the heat gradients possible within a PEM fuel cell and to better understand the calorimetric measurements, a 2D thermal model was created and applied at different conditions. The model was made by the use of the finite element method software COMSOL 3.3. This model was used to evaluate temperature elevations in the single cell mainly imposed by water transport, component thermal conductivity modifications and gas flow channel design. The 2D model was compared to a 1 D model to demonstrate the importance of taking the gas flow channel design into account. Parallel gas flow channels tend to impose an increased current density under the gas channel while serpentine flow channel pattern does the opposite, according to several studies. Thus a simple 2D model can, as very good approximation, be used to study effects rising from 3D cell designs. It was demonstrated that parallel flow fields give a higher maximum temperature than serpentine gas flow channels. Changes in the porous transport layer, such as compression, residual water and increased through-plane thermal conductivity were also discussed. In general, the maximum temperatures predicted for the PEM fuel cell were between 4.5 and 15 K above the control temperature in the polarization plate, depending on the conditions in the model. One

  6. High Temperature PEM Fuel Cells and Organic Fuels

    DEFF Research Database (Denmark)

    Vassiliev, Anton

    such an opportunity. Some knowledge about the electrooxidation of DME is available, together with its limited use in low temperature PEM fuel cells, where the low temperature poses an obstacle in the form of phase separation in the fuel supply, making the cells less effective and reducing the amount of power...... harvested from the cells. This is completely avoided at the elevated temperatures with the additional benefit of increased kinetics. In the presented work an experimental setup for testing direct dimethyl ether high temperature fuel cells is described, proposing a novel design of an evaporator for a burst...... evaporated liquid stream supply to either of the electrodes. A large number of MEAs with different component compositions have been prepared and tested in different conditions using the constructed setups to obtain a basic understanding of the nature of direct DME HT-PEM FC, to map the processes occurring...

  7. Experimental Characterization and Modeling of PEM Fuel Cells

    DEFF Research Database (Denmark)

    Jespersen, Jesper Lebæk

    fundamental knowledge of the transport and electrochemical processes of PEM fuel cells and to provide methods for obtaining high quality data for PEM fuel cell simulation model validation. In this thesis three different areas of experimental characterization techniques was investigated, they include: Stack....... In the area of stack flow and pressure distribution, the techniques of CFD, PIV and differential pressure measurements have been adopted to study flow phenomenons in the cathode manifold, with special emphasis on the manifold inlet conguration. It has been shown that these tools are excellent means...... for obtaining very detailed data of the manifold flow. Moreover, the tools complement each other well, as high quality validation data can be obtained from PIV measurements to verify CFD models. AC Impedance Spectroscopy was used to thoroughly characterize a HTPEM single cell. The measurement method...

  8. Proton Exchange Membrane (PEM) Material Synthetic Design for Fuel Cells

    Institute of Scientific and Technical Information of China (English)

    Michael; D.Guiver; Dae-Sik; Kim; Gilles; P.Robertson; Yu; Seung; Kim; Bryan; S.Pivovar

    2007-01-01

    1 Results Hydrocarbon PEM materials are being widely studied as replacements for Nafion-type perfluorinated polymeric materials to reduce cost and improve performance such as operating temperature and methanol crossover in the DMFC application. Among some of the important property considerations required are thermal and chemical stability, low dimensional swelling, low methanol permeability in the case of DMFC and high proton conductivity. Careful structural design can reduce the effect of swelling as...

  9. Cooling System Design for PEM Fuel Cell Powered Air Vehicles

    Science.gov (United States)

    2010-06-18

    radiator #7. The fan blades and shroud were formed using stereo lithography; the fan motor was a brushless DC motor with motor controller. These...Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6110--10-9253 Cooling System Design for PEM Fuel Cell Powered Air Vehicles June 18, 2010...Stroman, Michael W. Schuette,* and Gregory S. Page† Naval Research Laboratory 4555 Overlook Avenue, SW Washington, DC 20375-5342 NRL/MR/6110--10-9253

  10. An ultrathin self-humidifying membrane for PEM fuel cell application: fabrication, characterization, and experimental analysis.

    Science.gov (United States)

    Zhu, Xiaobing; Zhang, Huamin; Zhang, Yu; Liang, Yongmin; Wang, Xiaoli; Yi, Baolian

    2006-07-27

    An ultrathin poly(tetrafluoroethylene) (PTFE)-reinforced multilayer self-humidifying composite membrane (20 microm, thick) is developed. The membrane is composed of Nafion-impregnated porous PTFE composite as the central layer, and SiO2 supported nanosized Pt particles (Pt-SiO2) imbedded into the Nafion as the two side layers. The proton exchange membrane (PEM) fuel cell employing the self-humidifying membrane (Pt-SiO2/NP) turns out a peak power density of 1.40 W cm(-2) and an open circuit voltage (OCV) of 1.032 V under dry H2/O2 condition. The excellent performance is attributed to the combined result of both the accelerated water back-diffusion in the thin membrane and the adsorbing/releasing water properties of the Pt-SiO2 catalyst in the side layers. Moreover, the inclusion of the hygroscopic Pt-SiO2 catalyst inside the membrane results in an enhanced anode self-humidification capability and also the decreased cathode polarization (accordingly an improved cell OCV). Several techniques, such as transmission electronic microscopy, scanning electronic microscopy, energy dispersive spectroscopy, thermal analysis and electrochemical impedance spectroscopy etc., are employed to characterize the Pt-SiO2/NP membrane. The results are discussed in comparison with the plain Nafion/PTFE membrane (NP). It is established that the reverse net water drag (from the cathode to the anode) across the Pt-SiO2/NP membrane reaches 0.16 H2O/H+. This implies a good hydration of the Pt-SiO2/NP membrane and thus ensures an excellent PEM fuel cell performance under self-humidification operation.

  11. Fuel starvation. Irreversible degradation mechanisms in PEM fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Rangel, Carmen M.; Silva, R.A.; Travassos, M.A.; Paiva, T.I.; Fernandes, V.R. [LNEG, National Laboratory for Energy and Geology, Lisboa (Portugal). UPCH Fuel Cells and Hydrogen Unit

    2010-07-01

    PEM fuel cell operates under very aggressive conditions in both anode and cathode. Failure modes and mechanism in PEM fuel cells include those related to thermal, chemical or mechanical issues that may constrain stability, power and lifetime. In this work, the case of fuel starvation is examined. The anode potential may rise to levels compatible with the oxidization of water. If water is not available, oxidation of the carbon support will accelerate catalyst sintering. Diagnostics methods used for in-situ and ex-situ analysis of PEM fuel cells are selected in order to better categorize irreversible changes of the cell. Electrochemical Impedance Spectroscopy (EIS) is found instrumental in the identification of fuel cell flooding conditions and membrane dehydration associated to mass transport limitations / reactant starvation and protonic conductivity decrease, respectively. Furthermore, it indicates that water electrolysis might happen at the anode. Cross sections of the membrane catalyst and gas diffusion layers examined by scanning electron microscopy indicate electrode thickness reduction as a result of reactions taking place during hydrogen starvation. Catalyst particles are found to migrate outwards and located on carbon backings. Membrane degradation in fuel cell environment is analyzed in terms of the mechanism for fluoride release which is considered an early predictor of membrane degradation. (orig.)

  12. Production of hydrogen using composite membrane in PEM water electrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Santhi priya, E.L.; Mahender, C.; Mahesh, Naga; Himabindu, V. [Centre for Environment, Institute of Science and Technology, Jawaharlal Nehru Technological University Hyderabad, Kukatpally, Hyderabad-500 085, A.P (India); Anjaneyulu, Y. [Director, TLGVRC, JSU Box 18739, JSU, Jackson, MS 32917-0939 (United States)

    2012-07-01

    Electrolysis of water is the best known technology till today to produce hydrogen. The only practical way to produce hydrogen using renewable energy sources is by proton exchange membrane (PEM) water electrolysis. The most commonly used PEM membrane is Nafion. Composite membrane of TiO2 is synthesized by casting method using Nafion 5wt% solution. RuO2 is used as anode and 10 wt% Pd on activated carbon is used as cathode in the water electrolyser system. The performance of this Composite membrane is studied by varying voltage range 1.8 to 2.6V with respect to hydrogen yield and at current density 0.1, 0.2, 0.3, 0.4, and 0.5(A cm-2). This Composite membrane has been tested using in-house fabricated single cell PEM water electrolysis cell with 10cm2 active area at temperatures ranging from 30,45,65 850c and at 1 atmosphere pressure.

  13. Production of hydrogen using composite membrane in PEM water electrolysis

    Directory of Open Access Journals (Sweden)

    E.L.Santhi priya, C.Mahender, Naga Mahesh, V.Himabindu, Y.Anjaneyulu

    2012-01-01

    Full Text Available Electrolysis of water is the best known technology till today to produce hydrogen. The only practical way to produce hydrogen using renewable energy sources is by proton exchange membrane (PEM water electrolysis. The most commonly used PEM membrane is Nafion. Composite membrane of TiO2 is synthesized by casting method using Nafion 5wt% solution. RuO2 is used as anode and 10 wt% Pd on activated carbon is used as cathode in the water electrolyser system. The performance of this Composite membrane is studied by varying voltage range 1.8 to 2.6V with respect to hydrogen yield and at current density 0.1, 0.2, 0.3, 0.4, and 0.5(A cm-2. This Composite membrane has been tested using in-house fabricated single cell PEM water electrolysis cell with 10cm2 active area at temperatures ranging from 30,45,65 850c and at 1 atmosphere pressure.

  14. Structured modelling and nonlinear analysis of PEM fuel cells; Strukturierte Modellierung und nichtlineare Analyse von PEM-Brennstoffzellen

    Energy Technology Data Exchange (ETDEWEB)

    Hanke-Rauschenbach, R.

    2007-10-26

    In the first part of this work a model structuring concept for electrochemical systems is presented. The application of such a concept for the structuring of a process model allows it to combine different fuel cell models to form a whole model family, regardless of their level of detail. Beyond this the concept offers the opportunity to flexibly exchange model entities on different model levels. The second part of the work deals with the nonlinear behaviour of PEM fuel cells. With the help of a simple, spatially lumped and isothermal model, bistable current-voltage characteristics of PEM fuel cells operated with low humidified feed gases are predicted and discussed in detail. The cell is found to exhibit current-voltage curves with pronounced local extrema in a parameter range that is of practical interest when operated at constant feed gas flow rates. (orig.)

  15. Investigating the effect of water vapor and residual methanol on the anode of high temperature pem fuel cell

    DEFF Research Database (Denmark)

    Thomas, Sobi; Araya, Samuel Simon; Kær, Søren Knudsen

    2015-01-01

    The objective is to understand the effect of methanol and water vapor separately on a high temperature PEM fuel cell. An investigation was performed with different anode fuel compositions and results in terms of performance and impedance analyzed. During the initial 1000 h, cell was tested...... with pure hydrogen under varying current densities of 0.2 A cm-2 and 0.6 A cm-2, followed by hydrogen mixed with 15 % water vapor and then with 1 % methanol. The degradation rates at two current densities 0.2 A cm-2 and 0.6 A cm-2 were analyzed and discussed. The degradation at higher current density...... is more severe than at lower current density. However, on switching from higher to lower current density, the effect is reversible and the performance is improved. This suggests that some degradation is reversible. The addition of water vapor in the feed improves the performance at high current densities...

  16. Investigating the Effect of Water Vapor and Residual Methanol on the Anode of High Temperature PEM Fuel Cell

    DEFF Research Database (Denmark)

    Thomas, Sobi; Araya, Samuel Simon; Kær, Søren Knudsen

    The objective is to understand the effect of methanol and water vapor separately on a high temperature PEM fuel cell. An investigation was performed with different anode fuel compositions and results in terms of performance and impedance analyzed. During the initial 1000 h, cell was tested...... with pure hydrogen under varying current densities of 0.2 A cm-2 and 0.6 A cm-2, followed by hydrogen mixed with 15 % water vapor and then with 1 % methanol. The degradation rates at two current densities 0.2 A cm-2 and 0.6 A cm-2 were analyzed and discussed. The degradation at higher current density...... is more severe than at lower current density. However, on switching from higher to lower current density, the effect is reversible and the performance is improved. This suggests that some degradation is reversible. The addition of water vapor in the feed improves the performance at high current densities...

  17. New approaches to improve the performance of the PEM based fuel cell power systems

    Science.gov (United States)

    Choi, Woojin

    Fuel cells are expected to play an important role in future power generation. However, significant technical challenges remain and the commercial breakthrough of fuel cells is hindered by the high price of fuel cell components. As is well known, the fuel cells do not provide the robust source characteristics required to effectively follow the load during significant load steps and they have limited overload-handling capability. Further, the performance of the fuel cell is significantly degraded when the CO (Carbon Monoxide) is contained in the hydrogen fuel. In this thesis several new approaches to improve the performance of PEM based fuel cell power systems are discussed. In the first section an impedance model of the Proton Exchange Membrane Fuel Cell Stack (PEMFCS) is first proposed. This equivalent circuit model of the fuel cell stack is derived by a frequency response analysis (FRA) technique to evaluate the effects of the ripple current generated by the power-conditioning unit. Experimental results are presented to show the effects of the ripple currents. In the second section, a fuel cell powered UPS (Uninterruptible Power Supply) system is proposed. In this approach, two PEM Fuel Cell modules along with suitable DC/DC and DC/AC power electronic converter modules are employed. A Supercapacitor module is also employed to compensate for instantaneous power fluctuations including overload and to overcome the slow dynamics of the fuel processor such as reformers. A complete design example for a 1-kVA system is presented. In the third section, an advanced power converter topology is proposed to significantly improve the CO tolerance on PEM based fuel cell power systems. An additional two-stage dc-dc converter with a supercapacitor module is connected to the fuel cell to draw a low frequency (0.5Hz) pulsating current of the specific amplitude (20-30[A]) from the fuel cell stack. CO on the catalyst surface can be electro-oxidized by using this technique, and

  18. Develop Hydrophilic Conductive Coating Technology with High Oxidation Resistance for Non-Flow-Through PEM Fuel Cells and Electrolyzers Project

    Data.gov (United States)

    National Aeronautics and Space Administration — ElectroChem proposes to develop oxidation resistant, electrically conductive, hydrophilic coatings in PEM fuel cells and in PEM electrolyzers. The use of hydrophilic...

  19. 400 W High Temperature PEM Fuel Cell Stack Test

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Kær, Søren Knudsen

    2006-01-01

    This work demonstrates the operation of a 30 cell high temperature PEM (HTPEM) fuel cell stack. This prototype stack has been developed at the Institute of Energy Technology, Aalborg University, as a proof-of-concept for a low pressure cathode air cooled HTPEM stack. The membranes used are Celtec P...... of the species as in a LTPEM fuel cell system. The use of the HTPEM fuel cell makes it possible to use reformed gas at high CO concentrations, still with a stable efficient performance....

  20. Novel Hydrogen Purification Device Integrated with PEM Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Joseph Schwartz; Hankwon Lim; Raymond Drnevich

    2010-12-31

    A prototype device containing twelve membrane tubes was designed, built, and demonstrated. The device produced almost 300 scfh of purified hydrogen at 200 psig feed pressure. The extent of purification met the program target of selectively removing enough impurities to enable industrial-grade hydrogen to meet purity specifications for PEM fuel cells. An extrusion process was developed to produce substrate tubes. Membranes met several test objectives, including completing 20 thermal cycles, exceeding 250 hours of operating life, and demonstrating a flux of 965 scfh/ft2 at 200 psid and 400 C.

  1. Laser Ablation Increases PEM/Catalyst Interfacial Area

    Science.gov (United States)

    Whitacre, Jay; Yalisove, Steve

    2009-01-01

    An investigational method of improving the performance of a fuel cell that contains a polymer-electrolyte membrane (PEM) is based on the concept of roughening the surface of the PEM, prior to deposition of a thin layer of catalyst, in order to increase the PEM/catalyst interfacial area and thereby increase the degree of utilization of the catalyst. The roughening is done by means of laser ablation under carefully controlled conditions. Next, the roughened membrane surface is coated with the thin layer of catalyst (which is typically platinum), then sandwiched between two electrode/catalyst structures to form a membrane/ele c t - rode assembly. The feasibility of the roughening technique was demonstrated in experiments in which proton-conducting membranes made of a perfluorosulfonic acid-based hydrophilic, protonconducting polymer were ablated by use of femtosecond laser pulses. It was found that when proper combinations of the pulse intensity, pulse-repetition rate, and number of repetitions was chosen, the initially flat, smooth membrane surfaces became roughened to such an extent as to be converted to networks of nodules interconnected by filaments (see Figure 1). In further experiments, electrochemical impedance spectroscopy (EIS) was performed on a pristine (smooth) membrane and on two laser-roughened membranes after the membranes were coated with platinum on both sides. Some preliminary EIS data were interpreted as showing that notwithstanding the potential for laser-induced damage, the bulk conductivities of the membranes were not diminished in the roughening process. Other preliminary EIS data (see Figure 2) were interpreted as signifying that the surface areas of the laser-roughened membranes were significantly greater than those of the smooth membrane. Moreover, elemental analyses showed that the sulfur-containing molecular groups necessary for proton conduction remained intact, even near the laser-roughened surfaces. These preliminary results can be taken

  2. Modeling and identification of a PEM fuel cell humidification system

    Institute of Scientific and Technical Information of China (English)

    Xianrui DENG; Guoping LIU; George WANG; Min TAN

    2009-01-01

    A theoretical model of a humidifier of proton exchange membrane (PEM) fuel cell systems is developed and analyzed first in this paper. The model shows that there exists a strong nonlinearity in the system. Then, the system is identified using a wavelet networks method. To avoid the curse-of-dimensionality problem, a class of wavelet networks proposed by Billings is employed. The experimental data acquired from the test bench are used for identification. The one-step-ahead predictions and the five-step-ahead predictions are compared with the real measurements, respectively. It shows that the identified model can effectively describe the real system.

  3. PEM fuel cell bipolar plate material requirements for transportation applications

    Energy Technology Data Exchange (ETDEWEB)

    Borup, R.L.; Stroh, K.R.; Vanderborgh, N.E. [Los Alamos National Lab., NM (United States)] [and others

    1996-04-01

    Cost effective bipolar plates are currently under development to help make proton exchange membrane (PEM) fuel cells commercially viable. Bipolar plates separate individual cells of the fuel cell stack, and thus must supply strength, be electrically conductive, provide for thermal control of the fuel stack, be a non-porous materials separating hydrogen and oxygen feed streams, be corrosion resistant, provide gas distribution for the feed streams and meet fuel stack cost targets. Candidate materials include conductive polymers and metal plates with corrosion resistant coatings. Possible metals include aluminium, titanium, iron/stainless steel and nickel.

  4. Dynamic Response during PEM Fuel Cell Loading-up

    OpenAIRE

    Jun Gou; Pengcheng Li; Xing Yuan; Pucheng Pei

    2009-01-01

    A study on the effects of controlling and operating parameters for a Proton Exchange Membrane (PEM) fuel cell on the dynamic phenomena during the loading-up process is presented. The effect of the four parameters of load-up amplitudes and rates, operating pressures and current levels on gas supply or even starvation in the flow field is analyzed based accordingly on the transient characteristics of current output and voltage. Experiments are carried out in a single fuel cell with an active ar...

  5. Reversible Thermoset Adhesives

    Science.gov (United States)

    Mac Murray, Benjamin C. (Inventor); Tong, Tat H. (Inventor); Hreha, Richard D. (Inventor)

    2016-01-01

    Embodiments of a reversible thermoset adhesive formed by incorporating thermally-reversible cross-linking units and a method for making the reversible thermoset adhesive are provided. One approach to formulating reversible thermoset adhesives includes incorporating dienes, such as furans, and dienophiles, such as maleimides, into a polymer network as reversible covalent cross-links using Diels Alder cross-link formation between the diene and dienophile. The chemical components may be selected based on their compatibility with adhesive chemistry as well as their ability to undergo controlled, reversible cross-linking chemistry.

  6. Experimental analysis of a PEM fuel cell 15 W; Analise experimental de uma celula a combustivel PEM 15W

    Energy Technology Data Exchange (ETDEWEB)

    Miyake, Raphael Guardini; Bazzo, Edson [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil). Dept. de Engenharia Mecanica. Lab. de Combustao e Engenharia de Sistemas Termicos], e-mail: miyake@labcet.ufsc.br, e-mail: ebazzo@emc.ufsc.br

    2006-07-01

    Fuel cells have been considered a promising alternative for electric energy generation. In order to contribute with the development of this technology, a PEM fuel cell was installed and new experiments were carried out at LabCET (Laboratory of Combustion and Thermal System Engineering). Previous results have shown polarization curves identifying the need of rigorous controlling of humidification temperature of the fuel cell. In this paper, new results were carried out considering the use of a fan connected to the fuel cell and possible degradation in the electrolyte, after a relative long time operation. New polarization curves were plotted for comparison with previous results. (author)

  7. Synchrotron radiography and tomography of a PEM fuel cell; Synchrotron-Radiographie und -Tomographie einer PEM-Brennstoffzelle

    Energy Technology Data Exchange (ETDEWEB)

    Markoetter, Henning; Manke, Ingo [Helmholtzzentrum Berlin fuer Materialien und Energie, Berlin (Germany). Fachgruppe Bildgebende Verfahren; Arlt, Tobias [TU Berlin, Berlin (Germany); Banhart, John [TU Berlin, Institut fuer angewandte Materialforschung, Berlin (Germany); TU Berlin, Institut fuer Werkstoffwissenschaften und -technologien, Berlin (Germany); Riesemeier, Heinrich [Bundesanstalt fuer Materialforschung und -pruefung (BAM), Arbeitsgruppe Synchrotronstrahlanalytik (Germany); Krueger, Philipp [CONSULECTRA Unternehmensberatung GmbH, Hamburg (Germany); Haussmann, Jan; Klages, Merle [Zentrum fuer Sonnenenergie- und Wasserstoff-Forschung, Stuttgart (Germany); Scholta, Joachim [Zentrum fuer Sonnenenergie- und Wasserstoff-Forschung, Stuttgart (Germany). Fachgruppe Brennstoffzellen-Stacks

    2013-06-01

    The three dimensional water distribution and transport pathways in gas diffusion layers (GDL) of a polymer electrolyte membrane fuell cell (PEM FC) are analysed at various operating conditions. The method of quasi in-situ X-ray tomography is used for a three dimensional visualization of the water distribution and the GDL structure. Based on the results of dynamic radiographic measurements water transport pathways are located and subsequently investigated in detail by means of tomography. The combination of 2D and 3D techniques allows for an identification of 3D transport pathways through the GDl.

  8. Polymer Electrolyte Membrane (PEM) Fuel Cells Modeling and Optimization

    Science.gov (United States)

    Zhang, Zhuqian; Wang, Xia; Shi, Zhongying; Zhang, Xinxin; Yu, Fan

    2006-11-01

    Performance of polymer electrolyte membrane (PEM) fuel cells is dependent on operating parameters and designing parameters. Operating parameters mainly include temperature, pressure, humidity and the flow rate of the inlet reactants. Designing parameters include reactants distributor patterns and dimensions, electrodes dimensions, and electrodes properties such as porosity, permeability and so on. This work aims to investigate the effects of various designing parameters on the performance of PEM fuel cells, and the optimum values will be determined under a given operating condition.A three-dimensional steady-state electrochemical mathematical model was established where the mass, fluid and thermal transport processes are considered as well as the electrochemical reaction. A Powell multivariable optimization algorithm will be applied to investigate the optimum values of designing parameters. The objective function is defined as the maximum potential of the electrolyte fluid phase at the membrane/cathode interface at a typical value of the cell voltage. The robustness of the optimum design of the fuel cell under different cell potentials will be investigated using a statistical sensitivity analysis. By comparing with the reference case, the results obtained here provide useful tools for a better design of fuel cells.

  9. Reconstruction of microstructure in catalyst layer of PEM fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Rong, F.; Huang, C.; Liu, Z.S.; Song, D.T.; Wang, Q.P. [National Research Council of Canada, Vancouver, BC (Canada). Inst. for Fuel Cell Innovation

    2007-07-01

    Different microstructures of catalyst layer (CL) have been experimentally studied to improve the performance of the proton membrane exchange (PEM) fuel cell. These experiments have revealed the microstructure in catalyst layers can be considered as one kind of random media and its changes will have significant influence on the performance of PEM fuel cell. This paper presented the results of a study that applied the filtering method and stochastic optimization to reconstruct the microstructure based on the statistical information of catalyst layers. The filtering method changes the Gauss distributed signals to three-phase microstructure reconstruction while the stochastic optimization method, refines the microstructure reconstruction to fit the statistical features of experimental images. Based on the physical properties as well as the mass ratio, the statistical feature extraction based on image process of catalyst layer and the reconstruction procedure was proposed. The paper discussed evaluation of phase statistical information, initial reconstruction based on filtering method, stochastic optimization for reconstruction, as well as a summary of the study. It was concluded that the results of the filtering method as the initial pattern of stochastic optimization could make the error (between the final result and the experimental target) less than that of the random initial value and saved the computational time simultaneously. 13 refs., 6 figs.

  10. Gold Nanoparticles-Enhanced Proton Exchange Membrane (PEM) Fuel Cell

    Science.gov (United States)

    Li, Hongfei; Pan, Cheng; Liu, Ping; Zhu, Yimei; Adzic, Radoslav; Rafailovich, Miriam

    Proton exchange membrane fuel cells have drawn great attention and been taken as a promising alternated energy source. One of the reasons hamper the wider application of PEM fuel cell is the catalytic poison effect from the impurity of the gas flow. Haruta has predicted that gold nanoparticles that are platelet shaped and have direct contact with the metal oxide substrate to be the perfect catalysts of the CO oxidization, yet the synthesis method is difficult to apply in the Fuel Cell. In our approach, thiol-functionalized gold nanoparticles were synthesized through two-phase method developed by Brust et al. We deposit these Au particles with stepped surface directly onto the Nafion membrane in the PEM fuel cell by Langmuir-Blodgett method, resulting in over 50% enhancement of the efficiency of the fuel cell. DFT calculations were conducted to understand the theory of this kind of enhancement. The results indicated that only when the particles were in direct surface contact with the membrane, where AuNPs attached at the end of the Nafion side chains, it could reduce the energy barrier for the CO oxidation that could happen at T<300K.

  11. INVESTIGATION OF PEM FUEL CELL FOR AUTOMOTIVE USE

    Directory of Open Access Journals (Sweden)

    A. K. M. Mohiuddin

    2015-11-01

    Full Text Available This paper provides a brief investigation on suitability of Proton-exchange  membrane fuel cells (PEMFCs as the source of power for transportation purposes. Hydrogen is an attractive alternative transportation fuel. It is the least polluting fuel that can be used in an internal combustion engine (ICE and it is widely available. If hydrogen is used in a fuel cell which converts the chemical energy of hydrogen into electricity, (NOx emissions are eliminated. The investigation was carried out on a  fuel cell car model by implementing polymer electrolyte membrane (PEM types of fuel cell as the source of power to propel the prototype car. This PEMFC has capability to propel the electric motor by converting chemical energy stored in hydrogen gas into useful electrical energy. PEM fuel cell alone is used as the power source for the electric motor without the aid of any other power source such as battery associated with it. Experimental investigations were carried out to investigate the characteristics of fuel cell used and the performance of the fuel cell car. Investigated papameters are the power it develops, voltage, current and speed it produces under different load conditions. KEYWORDS: fuel cell; automotive; proton exchange membrane; polymer electrolyte membrane; internal combustion engine

  12. Synthesis of Cationic PEM Emulsion and Application in Waste Water Treatment

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhi-bin; LI Min; FANG Yi; SONG Hong; LUO Juan; XU Cheng-yin; WAN Chang-xiu

    2004-01-01

    Cationic polymer as a kind of flocculant is widely applied in purification treatment of waste water. Because it has positive charge group, it is able to connect strongly the suspended matters, short cellulose and other microparticles. The research on synthesis of cationic polymer and application in treatment of waste water is very universal abroad. But domestic research on those is not general. The technology of synthesis of PEM is simple, and the production cost is low. It is easy to apply in treatment of waste water.Synthesis of PEM Emulsion FlocculantSome distilled water, PVA(poly(vinyl alcohol)), EA(ethyl acrylate), and K2S2O8(potassium persulfate) were put into reaction vessel. Kept stirring up under nitrogen. When heated the solution to 40℃, dropped the water solution of MTA[(2-methacryloxylethyl)trimethyl ammonium].Maintained the temperature at 70℃, reacted about 7-8 hours. Then got the PEM emulsion. Changed the ratio of EA and MTA. Obtained a series of PEM emulsions.Stability and Convertibility of PEM EmulsionThe test results showed that when the EA/MTA was 85/15, the PEM emulsion was most stable.When the total monomer quantity was 35%, the convertibility of PEM emulsion was the highest,i.e.98.6%.The MTA Copolymerization Ratio and Morphology of PEM EmulsionWhen the monomers EA/MTA=85/15 and total monomer quantity was 35%, the MTA copolymerization ratio of PEM emulsion was 95.15%(the highest), and the PEM emulsion was some microspheres with 100-180nm of diameter.The Test Results of PEM Emulsion in Treatment of Waste Water The PEM emulsion flocculant was applied in treatment of waste water of paper mill, and measured the precipitation time(t) and transmittancy(T). The test results were showed in table 1. The optimum value of PEM which was able to make the waste water of paper mill into clear water was 0.008%.

  13. Performance of a reversible heat pump/organic Rankine cycle unit coupled with a passive house to get a positive energy building

    DEFF Research Database (Denmark)

    Dumont, Olivier; Carmo, Carolina; Fontaine, Valentin;

    2016-01-01

    and generate electricity, coupled to a solar thermal collector roof. This reversible HP/organic Rankine cycle unit presents three operating modes: direct heating, HP and organic Rankine cycle. This work focuses on describing the dynamic model of the multi-component system followed by a techno-economic analysis...... of the system under different operational conditions. Sensitivity studies include: building envelope, climate, appliances, lighting and heat demand profiles. It is concluded that the HP/ORC unit can turn a single-family house into a PEB under certain weather conditions (electrical production of 3012 k......Wh/year and total electrical consumption of 2318 kWh/year) with a 138.8 m2 solar roof in Denmark....

  14. Modeling optimizes PEM fuel cell durability using three-dimensional multi-phase computational fluid dynamics model

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2010-05-01

    Full Text Available Damage mechanisms in a proton exchange membrane (PEM fuel cell are accelerated by mechanical stresses arising during fuel cell assembly (bolt assembling, and the stresses arise during fuel cell running, because it consists of the materials with different thermal expansion and swelling coefficients. Therefore, in order to acquire a complete understanding of the damage mechanisms in the membrane and gas diffusion layers, mechanical response under steady-state hygro-thermal stresses should be studied under real cell operating conditions and in real cell geometry (three-dimensional. In this work, full three-dimensional, non-isothermal computational fluid dynamics model of a PEM fuel cell has been developed to simulate the hygro and thermal stresses in PEM fuel cell, which are occurring during the cell operation due to the changes of temperature and relative humidity. A unique feature of the present model is to incorporate the effect of hygro and thermal stresses into actual three-dimensional fuel cell model. The mechanical behaviour of the membrane, catalyst layers, and gas diffusion layers during the operation of a unit cell has been studied and investigated. The model is shown to be able to understand the many interacting, complex electrochemical, transport phenomena, and stresses distribution that have limited experimental data. The results show that the non-uniform distribution of stresses, caused by the temperature gradient in the cell, induces localized bending stresses, which can contribute to delaminating between the membrane and the gas diffusion layers. These results may explain the occurrence of cracks and pinholes in the membrane during regular cell operation. This model is used to study the effect of operating, design, and material parameters on fuel cell hygro-thermal stresses in polymer membrane, catalyst layers, and gas diffusion layers. Detailed analyses of the fuel cell durability under various operating conditions have been

  15. Modelling, experimentation and simulation of a reversible HP/ORC unit to get a Positive Energy Building

    DEFF Research Database (Denmark)

    Dumont, Olivier; Carmo, Carolina; Quoilin, Sylvain

    2015-01-01

    This paper presents an innovative building comprising a heat pump connected to a solar roof and a geothermal heat exchanger. This unit is able to invert its cycle and operate as an Organic Rankine Cycle (ORC). The solar roof is producing large amount of heat throughout the year. This allows...

  16. A portable power system using PEM fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Long, E. [Ball Aerospace and Technologies Corp., Boulder, CO (United States)

    1997-12-31

    Ball has developed a proof-of-concept, small, lightweight, portable power system. The power system uses a proton exchange membrane (PEM) fuel cell stack, stored hydrogen, and atmospheric oxygen as the oxidant to generate electrical power. Electronics monitor the system performance to control cooling air and oxidant flow, and automatically do corrective measures to maintain performance. With the controller monitoring the system health, the system can operate in an ambient environment from 0 C to +50 C. The paper describes system testing, including load testing, thermal and humidity testing, vibration and shock testing, field testing, destructive testing of high-pressure gas tanks, and test results on the fuel cell power system, metal hydride hydrogen storage, high-pressure hydrogen gas storage, and chemical hydride hydrogen storage.

  17. Model-based fault diagnosis in PEM fuel cell systems

    Energy Technology Data Exchange (ETDEWEB)

    Escobet, T.; de Lira, S.; Puig, V.; Quevedo, J. [Automatic Control Department (ESAII), Universitat Politecnica de Catalunya (UPC), Rambla Sant Nebridi 10, 08222 Terrassa (Spain); Feroldi, D.; Riera, J.; Serra, M. [Institut de Robotica i Informatica Industrial (IRI), Consejo Superior de Investigaciones Cientificas (CSIC), Universitat Politecnica de Catalunya (UPC) Parc Tecnologic de Barcelona, Edifici U, Carrer Llorens i Artigas, 4-6, Planta 2, 08028 Barcelona (Spain)

    2009-07-01

    In this work, a model-based fault diagnosis methodology for PEM fuel cell systems is presented. The methodology is based on computing residuals, indicators that are obtained comparing measured inputs and outputs with analytical relationships, which are obtained by system modelling. The innovation of this methodology is based on the characterization of the relative residual fault sensitivity. To illustrate the results, a non-linear fuel cell simulator proposed in the literature is used, with modifications, to include a set of fault scenarios proposed in this work. Finally, it is presented the diagnosis results corresponding to these fault scenarios. It is remarkable that with this methodology it is possible to diagnose and isolate all the faults in the proposed set in contrast with other well known methodologies which use the binary signature matrix of analytical residuals and faults. (author)

  18. Studies on PEM fuel cell noble metal catalyst dissolution

    DEFF Research Database (Denmark)

    Andersen, S. M.; Grahl-Madsen, L.; Skou, E. M.

    2011-01-01

    A combination of electrochemical, spectroscopic and gravimetric methods was carried out on Proton Exchange Membrane (PEM) fuel cell electrodes with the focus on platinum and ruthenium catalysts dissolution, and the membrane degradation. In cyclic voltammetry (CV) experiments, the noble metals were...... found to dissolve in 1 M sulfuric acid solution and the dissolution increased exponentially with the upper potential limit (UPL) between 0.6 and 1.6 vs. RHE. 2-20% of the Pt (depending on the catalyst type) was found to be dissolved during the experiments. Under the same conditions, 30-100% of the Ru...... (depending on the catalyst type) was found to be dissolved. The faster dissolution of ruthenium compared to platinum in the alloy type catalysts was also confirmed by X-ray diffraction measurements. The dissolution of the carbon supported catalyst was found one order of magnitude higher than the unsupported...

  19. Fatigue and Mechanical Damage Propagation in Automotive PEM Fuel Cells

    Science.gov (United States)

    Banan, Roshanak

    Polymer electrolyte membrane (PEM) fuel cells are generally exposed to high magnitude road-induced vibrations and impact loads, frequent humidity-temperature loading cycles, and freeze/thaw stresses when employed in automotive applications. The resultant mechanical stresses can play a significant role in the evolution of mechanical defects in the membrane electrode assembly (MEA). The focus of this research is to investigate fatigue challenges due to humidity-temperature (hygrothermal) cycles and vibrations and their effects on damage evolution in PEM fuel cells. To achieve this goal, this thesis is divided into three parts that provide insight into damage propagation in the MEA under i) hygrothermal cycles, ii) external applied vibrations, and iii) a combination of both to simulate realistic automotive conditions. A finite element damage model based on cohesive zone theory was developed to simulate the propagation of micro-scale defects (cracks and delaminations) in the MEA under fuel cell operating conditions. It was found that the micro-defects can propagate to critical states under start-up and shut-down cycles, prior to reaching the desired lifespan of the fuel cell. The simultaneous presence of hygrothermal cycles and vibrations severely intensified damage propagation and resulted in considerably large defects within 75% of the fuel cell life expectancy. However, the order of generated damage was found to be larger under hygrothermal cycles than vibrations. Under hygrothermal cycles, membrane crack propagation was more severe compared to delamination propagation. Conversely, the degrading influence of vibrations was more significant on delaminations. The presence of an anode/cathode channel offset under the combined loadings lead to a 2.5-fold increase in the delamination length compared to the aligned-channel case. The developed model can be used to investigate the damage behaviour of current materials employed in fuel cells as well as to evaluate the

  20. PEM Electrolyzer Incorporating an Advanced Low-Cost Membrane

    Energy Technology Data Exchange (ETDEWEB)

    Hamdan, Monjid [Giner, Inc.

    2013-08-29

    The Department of Energy (DOE) has identified hydrogen production by electrolysis of water at forecourt stations as a critical technology for transition to the hydrogen economy; however, the cost of hydrogen produced by present commercially available electrolysis systems is considerably higher than the DOE 2015 and 2020 cost targets. Analyses of proton-exchange membrane (PEM) electrolyzer systems indicate that reductions in electricity consumption and electrolyzer stack and system capital cost are required to meet the DOE cost targets. The primary objective is to develop and demonstrate a cost-effective energy-based system for electrolytic generation of hydrogen. The goal is to increase PEM electrolyzer efficiency and to reduce electrolyzer stack and system capital cost to meet the DOE cost targets for distributed electrolysis. To accomplish this objective, work was conducted by a team consisting of Giner, Inc. (Giner), Virginia Polytechnic Institute & University (VT), and domnick hunter group, a subsidiary of Parker Hannifin (Parker). The project focused on four (4) key areas: (1) development of a high-efficiency, high-strength membrane; (2) development of a long-life cell-separator; (3) scale-up of cell active area to 290 cm2 (from 160 cm²); and (4) development of a prototype commercial electrolyzer system. In each of the key stack development areas Giner and our team members conducted focused development in laboratory-scale hardware, with analytical support as necessary, followed by life-testing of the most promising candidate materials. Selected components were then scaled up and incorporated into low-cost scaled-up stack hardware. The project culminated in the fabrication and testing of a highly efficient electrolyzer system for production of 0.5 kg/hr hydrogen and validation of the stack and system in testing at the National Renewable Energy Laboratory (NREL).

  1. Novel proton exchange membrane fuel cell electrodes to improve performance of reversible fuel cell systems

    Science.gov (United States)

    Brown, Tim Matthew

    Proton exchange membrane (PEM) fuel cells react fuel and oxidant to directly and efficiently produce electrical power, without the need for combustion, heat engines, or motor-generators. Additionally, PEM fuel cell systems emit zero to virtually zero criteria pollutants and have the ability to reduce CO2 emissions due to their efficient operation, including the production or processing of fuel. A reversible fuel cell (RFC) is one particular application for a PEM fuel cell. In this application the fuel cell is coupled with an electrolyzer and a hydrogen storage tank to complete a system that can store and release electrical energy. These devices can be highly tailored to specific energy storage applications, potentially surpassing the performance of current and future secondary battery technology. Like all PEM applications, RFCs currently suffer from performance and cost limitations. One approach to address these limitations is to improve the cathode performance by engineering more optimal catalyst layer geometry as compared to the microscopically random structure traditionally used. Ideal configurations are examined and computer modeling shows promising performance improvements are possible. Several novel manufacturing methods are used to build and test small PEM fuel cells with novel electrodes. Additionally, a complete, dynamic model of an RFC system is constructed and the performance is simulated using both traditional and novel cathode structures. This work concludes that PEM fuel cell microstructures can be tailored to optimize performance based on design operating conditions. Computer modeling results indicate that novel electrode microstructures can improve fuel cell performance, while experimental results show similar performance gains that bolster the theoretical predictions. A dynamic system model predicts that novel PEM fuel cell electrode structures may enable RFC systems to be more competitive with traditional energy storage technology options.

  2. Analysing Gas-Liquid Flow in PEM Electrolyser Micro-Channels (Poster)

    DEFF Research Database (Denmark)

    Lafmejani, Saeed Sadeghi; Olesen, Anders Christian; Kær, Søren Knudsen

    to hot spots. Management of heat and fluid flow through the micro-channels play a great role in the capability of PEM water electrolysis when working at high current densities. Despite, many studies have been done on gas-liquid flows; still there is a lack of research on gas-liquid flows in micro......One means of increasing the hydrogen yield to cost ratio of a PEM water electrolyser, is to increase the operating current density. However, at high current densities (higher than 1 A/cm2), management of heat and mass transfer in the anode current collector and channel becomes crucial and can lead......-sized channels (hydraulic diameter of 1 mm) of PEM water electrolysis. Precisely controlling all the parameters that affect the gas-liquid flow in a PEM water electrolysis cell is quite challenging, hence a simplified setup is constructed consisting of only a transparent channel with a sheet of titanium felt...

  3. Interaction of Mouse Pem Protein and Cell Division Cycle 37 Homolog

    Institute of Scientific and Technical Information of China (English)

    Fen GUO; Yue-Qin LI; Shi-Qian LI; Zhi-Wen LUO; Xin ZHANG; Dong-Sheng TANG; Tian-Hong ZHOU

    2005-01-01

    Mouse Pem, a homeobox gene, encodes a protein consisting of 210 amino acid residues. To study the function of mouse Pem protein, we used the yeast two-hybrid system to screen the library of 7-day mouse embryo with full-length mouse Pem eDNA. Fifty-two colonies were obtained after 1.57×108 colonies were screened by nutrition limitation and β-galactosidase assay. Seven individual insert fragments were obtained from the library, and three of them were identified, one of which was confirmed to be the cell division cycle 37 (Cdc37) homolog gene by sequencing. The interaction between mouse Pem and Cdc37homolog was then confirmed by glutathione S-transferase pull-down assay, and the possible interaction model was suggested.

  4. Development of some exergetic parameters for PEM fuel cells for measuring environmental impact and sustainability

    Energy Technology Data Exchange (ETDEWEB)

    Midilli, Adnan [Energy Division, Mechanical Engineering Dept., Nigde University, 51100 Nigde (Turkey); Dincer, Ibrahim [Faculty of Engineering and Applied Science, University of Ontario Institute of Technology, 2000 Simcoe Street North, Oshawa, Ontario (Canada)

    2009-05-15

    This paper presents some new exergy-based parameters for PEM fuel cells to study how some of their operating aspects and system characteristics affect the environment and sustainability, based on some actual and literature data. The exergetic parameters of a PEM fuel cell developed here, in conjunction with environmental impact and sustainable development, are exergy efficiency, exergetic stability factor, environmental benign index and exergetic sustainability index. Any increase in efficiency improves exergetic sustainability. However, any increase in waste exergy ratio, exergy destruction factor, environmental destruction coefficient and environmental destruction index results in an increasing environmental impact of the PEM fuel cell and hence, a decreasing sustainability. Such parameters are expected to quantify how PEM fuel cells become more environmentally benign and sustainable. (author)

  5. Design and construction of an electrolyte PEM test; Diseno y construccion de un electrolizador PEM de prueba

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Huerta, R. G.; Santillan-Aragon, G. [Instituto Politecnico Nacional, Mexico, D.F. (Mexico)]. E-mail: rosgonzalez_h@yahoo.com.mx; Solorza-Feria, O. [CINVESTAV-IPN, Mexico D.F. (Mexico)

    2009-09-15

    The use of hydrogen as a fuel is directly linked to its efficient and clean production. One of the most promising methods is water electrolysis, which coupled with a renewable energy source prevents the emission of pollutants into the atmosphere. If a proton exchange membrane (PEM) electrolysis is used, a highly pure hydrogen is produced, ready to be used in a fuel battery. Many studies and investigations in this area concentrate on finding different stable and selective electrocatalysts for the cathode reaction (production of hydrogen) and anode reaction (production of oxygen). To conduct these studies, equipment is needed to perform electrochemical studies and determine the stability and performance of different electrocatalysts. This work presents the design and construction of an a PEM electrolysis test to determine the performance of different anode electrocatalysts. Its active area is 4 cm{sup 2}, its structure is graphite and the current distribution mesh is made of stainless steel. Its performance was determined using as electrocatalysts 10% Pt/C E-tek® anodes and a 50%-50%, 25%-75% and 75%-25% combination of RuO{sub 2}-IrO{sub 2}. The authors wish to thank the ICYTDF (PICS08-37) for financial support and IPN (SIP-20090433) and architect Nestor Romero for the electrolysis machining. [Spanish] La utilizacion del hidrogeno como combustible esta ligado directamente a su produccion eficiente y limpia, uno de los metodos mas prometedores es la electrolisis del agua, ya que acoplado con una fuente de energia renovable se evita la emision de contaminantes a la atmosfera. Si se utiliza un electrolizador de membrana de intercambio protonico (Tipo PEM), el hidrogeno que se produce es de alta pureza, listo para ser utilizado en una pila de combustible. Muchos estudios e investigaciones en esta area se concentran en encontrar distintos electrocatalizadores estables y selectivos para la reaccion catodica (produccion de hidrogeno) y anodica (produccion de oxigeno). Para

  6. PEM-Scoot - Control system and analysis of operation; PEM-Scoot. Steuerung und Betriebsanalyse. Diplomarbeit 2006/07

    Energy Technology Data Exchange (ETDEWEB)

    Naegeli, M.; Kaiser, R.

    2007-07-01

    This diploma thesis presented at the Bernese University of Applied Sciences, Switzerland, describes a project concerning a new drive technology. The PEM-Scoot is a scooter with an electric drive which is powered by a fuel cell, using hydrogen and oxygen stored in two pressure cylinders. That only water is exhausted during operation is considered to be an important advantage. The work done in the project consisted on the one hand of the writing of software for the control and putting it into service and, on the other hand, of various driving tests carried out in order to optimise the control software for stand-alone handling. The planning of the project is described, as are the various components used. The software for the operation of the vehicle is described in detail. The results of driving tests are presented. The report is complemented with a comprehensive appendix.

  7. Thermal modeling and temperature control of a PEM fuel cell system for forklift applications

    DEFF Research Database (Denmark)

    Liso, Vincenzo; Nielsen, Mads Pagh; Kær, Søren Knudsen

    2014-01-01

    . A combination of high temperature and reduced humidity increases the degradation rate. Stack thermal management and control are, thus, crucial issues in PEM fuel cell systems especially in automotive applications such as forklifts. In this paper we present a control–oriented dynamic model of a liquid–cooled PEM...... designers in choosing the required coolant mass flow rate and radiator size to minimize the stack temperature gradients....

  8. MODELLING AND FUZZY LOGIC CONTROL OF PEM FUEL CELL SYSTEM POWER GENERATION FOR RESIDENTIAL APPLICATION

    OpenAIRE

    Khaled MAMMAR; CHAKER, Abdelkader

    2010-01-01

    This paper presents a dynamic model of Fuel cell system for residential power generation. The models proposedinclude a fuel cell stack model, reformer model and DC/AC inverter model. More then an analytical details ofhow active and reactive power output of a proton-exchange-membrane (PEM) fuel cell system is controlled.Furthermore a fuzzy logic (FLC) controller is used to control active power of PEM fuel cell system. Thecontroller modifies the hydrogen flow feedback from the terminal load. Si...

  9. HOGEN{trademark} proton exchange membrane hydrogen generators: Commercialization of PEM electrolyzers

    Energy Technology Data Exchange (ETDEWEB)

    Smith, W.F.; Molter, T.M. [Proton Energy Systems, Inc., Rocky Hill, CT (United States)

    1997-12-31

    PROTON Energy Systems` new HOGEN series hydrogen generators are Proton Exchange Membrane (PEM) based water electrolyzers designed to generate 300 to 1000 Standard Cubic Feet Per Hour (SCFH) of high purity hydrogen at pressures up to 400 psi without the use of mechanical compressors. This paper will describe technology evolution leading to the HOGEN, identify system design performance parameters and describe the physical packaging and interfaces of HOGEN systems. PEM electrolyzers have served US and UK Navy and NASA needs for many years in a variety of diverse programs including oxygen generators for life support applications. In the late 1970`s these systems were advocated for bulk hydrogen generation through a series of DOE sponsored program activities. During the military buildup of the 1980`s commercial deployment of PEM hydrogen generators was de-emphasized as priority was given to new Navy and NASA PEM electrolysis systems. PROTON Energy Systems was founded in 1996 with the primary corporate mission of commercializing PEM hydrogen generators. These systems are specifically designed and priced to meet the needs of commercial markets and produced through manufacturing processes tailored to these applications. The HOGEN series generators are the first step along the path to full commercial deployment of PEM electrolyzer products for both industrial and consumer uses. The 300/1000 series are sized to meet the needs of the industrial gases market today and provide a design base that can transition to serve the needs of a decentralized hydrogen infrastructure tomorrow.

  10. Lattice Boltzmann Simulation of Multiphase Transport in Nanostructured PEM Fuel Cells

    Science.gov (United States)

    Stiles, Christopher D.

    As the fossil fuel crisis becomes more critical, it is imperative to develop renewable sources of power generation. Polymer electrolyte membrane (PEM) fuel cells are considered a viable option. However, the cost of the platinum catalyst has hindered their commercialization. PEM fuel cells with platinum loading of >0.4 mg cm2 are common. Efforts towards further reducing this loading are currently underway utilizing nanostructured electrodes. A consequence of increased platinum utilization per unit area and thinner nanostructured electrodes is flooding, which is detrimental to fuel cell performance. Flooding causes a two-fold impact on cell performance: a drop in cell voltage and a rise in parasitic pumping power to overcome the increased pressure drop, which together result in a significant reduction in system efficiency. Proper water management is therefore crucial for optimum performance of the fuel cell and also for enhancing membrane durability. The goal of this thesis is to simulate the multiphase fluid transport in the nanostructured PEMFC of H2O in air with realistic density ratios. In order to pursue this goal, the ability of the pseudopotential based multiphase lattice Boltzmann method to realistically model the coexistence of the gas and liquid phases of H2O at low temperatures is explored. This method is expanded to include a gas mixture of O2 and N 2 into the multiphase H2O systems. Beginning with the examination of the phase transition region described by the current implementation of the multiphase pseudopotential lattice Boltzmann model. Following this, a modified form of the pressure term with the use of a scalar multiplier kappa for the Peng-Robinson equation of state is thoroughly investigated. This method proves to be very effective at enabling numerically stable simulations at low temperatures with large density ratios. It is found that for decreasing values of kappa, this model leads to an increase in multiphase interface thickness and a

  11. Strategies of Accelerating Reverse Time Migration Using Graphic Processing Unit%应用图形处理器快速计算逆时偏移

    Institute of Scientific and Technical Information of China (English)

    刘雅宁; 刘国峰; 张致付

    2012-01-01

    逆时偏移是目前精度最高的地震数据叠前深度偏移方法,但高强度的计算需求限制了其在工业生产领域的大规模应用.可编程图形处理器的发展为逆时偏移的快速计算提供了一种新的计算选择.围绕如何在图形处理器上开展逆时偏移计算展开,总结了图形处理器计算的优化关键,并根据逆时偏移的特点着重介绍了两个优化环节:一个是应用随机边界条件,以计算换存储,减少数据在主机和图形处理器间的传输;二是应用共享存储器来存储正演计算的波场,相比全局存储器,提高了数据读取的带宽.应用Marmousi模型数据对经过上述优化后的程序进行了测试,结果表明,图形处理器逆时偏移程序得到了很好的优化,提高了计算效率.%Reverse-time migration is the most accurate seismic data prestack depth migration method, but the computing needs of its high-intensity limit its large-scale computing applications. The development of programmable Graphics Processing Unit (GPU) provides an alternative method for rapid calculation of the reverse-time migration. In this paper, we focus on the main steps using GPU to calculate the reverse time migration. We summarize the key points in GPU code optimization, and highlight two optimized components; one is the application of random boundary conditions. The data transmission between the host and GPU is reduced. The second is the application of shared memory to store the forward wave field. Compared to the global memory, data reading band widths increase greatly. Finally, we use the Marmousi data to test our code, and the results show that the reverse-time migration program running on GPU has been well optimized to improve the computational efficiency.

  12. Simulation and evaluation of a high resolution VIP PEM system with a dedicated LM-OSEM algorithm

    OpenAIRE

    Uzun, D.; De Lorenzo, G.; Kolstein, M.; Chmeissani, M.

    2014-01-01

    Over the last two decades there have been a growing number of designs for positron emission tomography (PET) cameras optimized to image the breast. These devices, commonly known as positron emission mammography (PEM) cameras allow much more spatial resolution by putting the photon detectors directly on the breast. PEM cameras have a compact geometry with a restricted field of view (FOV) thus exhibiting higher performance and lower cost than large whole body PET scanners. Typical PEM designs a...

  13. The reversal of fortunes: trends in county mortality and cross-county mortality disparities in the United States.

    Directory of Open Access Journals (Sweden)

    Majid Ezzati

    2008-04-01

    Full Text Available Counties are the smallest unit for which mortality data are routinely available, allowing consistent and comparable long-term analysis of trends in health disparities. Average life expectancy has steadily increased in the United States but there is limited information on long-term mortality trends in the US counties This study aimed to investigate trends in county mortality and cross-county mortality disparities, including the contributions of specific diseases to county level mortality trends.We used mortality statistics (from the National Center for Health Statistics [NCHS] and population (from the US Census to estimate sex-specific life expectancy for US counties for every year between 1961 and 1999. Data for analyses in subsequent years were not provided to us by the NCHS. We calculated different metrics of cross-county mortality disparity, and also grouped counties on the basis of whether their mortality changed favorably or unfavorably relative to the national average. We estimated the probability of death from specific diseases for counties with above- or below-average mortality performance. We simulated the effect of cross-county migration on each county's life expectancy using a time-based simulation model. Between 1961 and 1999, the standard deviation (SD of life expectancy across US counties was at its lowest in 1983, at 1.9 and 1.4 y for men and women, respectively. Cross-county life expectancy SD increased to 2.3 and 1.7 y in 1999. Between 1961 and 1983 no counties had a statistically significant increase in mortality; the major cause of mortality decline for both sexes was reduction in cardiovascular mortality. From 1983 to 1999, life expectancy declined significantly in 11 counties for men (by 1.3 y and in 180 counties for women (by 1.3 y; another 48 (men and 783 (women counties had nonsignificant life expectancy decline. Life expectancy decline in both sexes was caused by increased mortality from lung cancer, chronic obstructive

  14. A Frequency-Domain Adaptive Filter (FDAF) Prediction Error Method (PEM) Framework for Double-Talk-Robust Acoustic Echo Cancellation

    DEFF Research Database (Denmark)

    Gil-Cacho, Jose M.; van Waterschoot, Toon; Moonen, Marc

    2014-01-01

    In this paper, we propose a new framework to tackle the double-talk (DT) problem in acoustic echo cancellation (AEC). It is based on a frequency-domain adaptive filter (FDAF) implementation of the so-called prediction error method adaptive filtering using row operations (PEM-AFROW) leading...... to the FDAF-PEM-AFROW algorithm. We show that FDAF-PEM-AFROW is by construction related to the best linear unbiased estimate (BLUE) of the echo path. We depart from this framework to show an improvement in performance with respect to other adaptive filters minimizing the BLUE criterion, namely the PEM...

  15. A methodology for investigating new nonprecious metal catalysts for PEM fuel cells.

    Science.gov (United States)

    Susac, D; Sode, A; Zhu, L; Wong, P C; Teo, M; Bizzotto, D; Mitchell, K A R; Parsons, R R; Campbell, S A

    2006-06-08

    This paper reports an approach to investigate metal-chalcogen materials as catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells. The methodology is illustrated with reference to Co-Se thin films prepared by magnetron sputtering onto a glassy-carbon substrate. Scanning Auger microscopy (SAM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) have been used, in parallel with electrochemical activity and stability measurements, to assess how the electrochemical performance relates to chemical composition. It is shown that Co-Se thin films with varying Se are active for oxygen reduction, although the open circuit potential (OCP) is lower than for Pt. A kinetically controlled process is observed in the potential range 0.5-0.7 V (vs reversible hydrogen electrode) for the thin-film catalysts studied. An initial exposure of the thin-film samples to an acid environment served as a pretreatment, which modified surface composition prior to activity measurements with the rotating disk electrode (RDE) method. Based on the SAM characterization before and after electrochemical tests, all surfaces demonstrating activity are dominated by chalcogen. XRD shows that the thin films have nanocrystalline character that is based on a Co(1-x)Se phase. Parallel studies on Co-Se powder supported on XC72R carbon show comparable OCP, Tafel region, and structural phase as for the thin-film model catalysts. A comparison for ORR activity has also been made between this Co-Se powder and a commercial Pt catalyst.

  16. Light sharing in multi-flat-panel-PMT PEM detectors.

    Science.gov (United States)

    Raylman, Raymond R; Majewski, Stan; Mayhugh, Michael R

    2006-01-01

    Large are a detectors, such as those used in positron emission mammography (PEM) and scintimammography, utilize arrays of discrete semtillator elements mounted on arrays of position sensitive photomultiplier tubes (PSPMT). Scintillator elements can be packed very densely (minimizing area between elements), allowing good detection sensitivity and spatial resolution. And, while new flat panel PSPMTS have minimal inactive edges, when they are placed in arrays significant dead spaces where scintillation light is undetectable are created. To address this problem, a light guide is often placed between the detector and PSPMT array to spread scintillation light so that these gaps can be bridged. In this investigation we studied the effect of light guides of various thickness on system performance. A 10x10 element array of LYSO detector elements was coupled to the center of a 2x2 array of PSPMTs through varying thicknesses (1 to 4 mm) of UV glass. The spot size of the imaged elements and distortions in the regular square pattern of the imaged scintillator arrays were evaluated. Energy resolution was measured by placing single elements of LYSO at several locations of the PSPMT array. Spatial distortions in the images of the array were reduced by using thicker light guides (3-4 mm). Use of thicker light guides, however, resulted in reduced pixel resolution and slight degradation of energy resolution. Therefore, some loss of pixel and energy resolution will accompany the use of thick light guides (minimum of 3 mm) required for optimum identification of detector elements.

  17. Sliding-Mode Control of PEM Fuel Cells

    CERN Document Server

    Kunusch, Cristian; Mayosky, Miguel

    2012-01-01

    Recent advances in catalysis technologies and new materials make fuel cells an economically appealing and clean energy source with massive market potential in portable devices, home power generation and the automotive industry. Among the more promising fuel-cell technologies are proton exchange membrane fuel cells (PEMFCs). Sliding-Mode Control of PEM Fuel Cells demonstrates the application of higher-order sliding-mode control to PEMFC dynamics. Fuel-cell dynamics are often highly nonlinear and the text shows the advantages of sliding modes in terms of robustness to external disturbance, modelling error and system-parametric disturbance using higher-order control to reduce chattering. Divided into two parts, the book first introduces the theory of fuel cells and sliding-mode control. It begins by contextualising PEMFCs both in terms of their development and within the hydrogen economy and today’s energy production situation as a whole. The reader is then guided through a discussion of fuel-cell operation pr...

  18. Electrochemical extraction of oxygen using PEM electrolysis technology

    Directory of Open Access Journals (Sweden)

    BOULBABA ELADEB

    2012-11-01

    Full Text Available Electrochemical extraction of oxygen from air can be carried out by chemical reduction of oxygen at the cathode and simultaneous oxygen evolution by water anode oxidation. The present investigation deals with the use of an electrolysis cell of PEM technology for this purpose. A dedicated 25 cm2 cell provided with a commercial water electrolysis MEA and titanium grooved plates has been designed for continuous operation at pressures close to the ambient level. The MEA consisted of a Nafion 117 membrane sandwiched between a Pt/C cathode and a non-supported Pt-Ir anode. Oxygen partial consumption in long-term runs was evaluated by analysis of the outlet air by gas chromatography, depending on the cell voltage - or the current density - and the excess in air oxygen fed to the cathode. Runs over more 50 hours indicated the relative stability of the components used for current densities ranging from 0.1 to 0.2 A cm-2 with high efficiency of oxygen reduction. Higher current density could be envisaged with more efficient MEA’s, exhibiting lower overpotentials for oxygen evolution to avoid too significant degradation of the anode material and the membrane. Interpretation of the data has been carried out by calculation of the cathode current efficiency.

  19. X-ray computed tomography of PEM fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Pfrang, Andreas; Veyret, Damien; Tsotridis, Georgios [Commission of the European Communities, Petten (Netherlands). Joint Reseach Centre, Inst. for Energy; Janssen, Gaby [Energy Research Centre of the Netherlands ECN, Petten (Netherlands). Dept. of Hydrogen and Clean Fossil Fuels

    2010-07-01

    Proton exchange membrane (PEM) fuel cells were investigated by 3D x-ray computed tomography at a voxel size of 0.7 {mu}m. It is shown that this lab-based technique is not only suitable for the investigation of gas diffusion layers (GDL) as well as the investigation of membrane electrode assemblies (MEA), but also allows the calculation of macroscopic physical properties. The resolution of computed tomography is clearly sufficient to image the carbon fiber structure of gas diffusion layers in the as received GDLs as well as GDLs integrated into membrane electrode assemblies. It is also possible to visualize the catalyst layer within the MEA, which allows the investigation of layer thickness and structural defects on a larger scale than with conventional techniques. The macroscopic effective thermal conductivities of the gas diffusion layers were computed based on the 3D GDL structure reconstructed from tomography data to produce more reliable input data for fuel cell modeling. The computation was carried out by solving the energy equation considering a pure thermal conduction problem. The computations show - in agreement with the expectation and experimental data - that the through-plane thermal conductivities are lower than the in-plane thermal conductivities. (orig.)

  20. Modeling of PEM fuel cell Pt/C catalyst degradation

    Science.gov (United States)

    Bi, Wu; Fuller, Thomas F.

    Pt/C catalyst degradation remains as one of the primary limitations for practical applications of proton exchange membrane (PEM) fuel cells. Pt catalyst degradation mechanisms with the typically observed Pt nanoparticle growth behaviors have not been completely understood and predicted. In this work, a physics-based Pt/C catalyst degradation model is proposed with a simplified bi-modal particle size distribution. The following catalyst degradation processes were considered: (1) dissolution of Pt and subsequent electrochemical deposition on Pt nanoparticles in cathode; (2) diffusion of Pt ions in the membrane electrode assembly (MEA); and (3) Pt ion chemical reduction in membrane by hydrogen permeating through the membrane from the negative electrode. Catalyst coarsening with Pt nanoparticle growth was clearly demonstrated by Pt mass exchange between small and large particles through Pt dissolution and Pt ion deposition. However, the model is not adequate to predict well the catalyst degradation rates including Pt nanoparticle growth, catalyst surface area loss and cathode Pt mass loss. Additional catalyst degradation processes such as new Pt cluster formation on carbon support and neighboring Pt clusters coarsening was proposed for further simulative investigation.

  1. High temperature PEM fuel cell. Final report. Public part

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, Jens Oluf (DTU (DK)); Yde Andersen, S.; Rycke, T. de (IRD Fuel Cells A/S (DK)); Nilsson, M. (Danish Power Systems ApS (DK)); Christensen, Torkild, (DONG Energy (DK))

    2006-07-01

    The main outcome of the project is the development of stacking technology for high temperature PEMFC stacks based on phosphoric acid doped polybenzimidazole membranes (PBI-membranes) and a study of the potential of a possible accommodation of HT-PEMFC in the national energy system. Stacks of different lengths (up to 40 cells) have been built using two different approaches in terms of plate materials and sealing. The stacks still need maturing and further testing to prove satisfactory reliability, and a steady reduction of production cost is also desired (as in general for fuel cells). However, during the project the process has come a long way. The survey of HT-PEM fuel cells and their regulatory power in the utility system concludes that fuel cells will most likely not be the dominating technique for regulation, but as no other technique has that potential alone, fuel cells are well suited to play a role in the system provided that the establishment of a communication system is not too complicated. In order to maintain an efficient power system with high reliability in a distributed generation scenario, it is important that communication between TSO (Transmission System Operator) and fuel cells is included in the fuel cell system design at an early stage. (au)

  2. Study of PEM fuel cell performance by electrochemical impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Asghari, Saeed; Mokmeli, Ali; Samavati, Mahrokh [Isfahan Engineering Research Center, 7th kilometer of Imam Khomeini ave., P.O. Box 81395-619, Isfahan (Iran)

    2010-09-15

    Electrochemical impedance spectroscopy is a suitable and powerful diagnostic testing method for fuel cells because it is non-destructive and provides useful information about fuel cell performance and its components. This paper presents the diagnostic testing results of a 120 W single cell and a 480 W PEM fuel cell short stack by electrochemical impedance spectroscopy. The effects of clamping torque, non-uniform assembly pressure and operating temperature on the single cell impedance spectrum were studied. Optimal clamping torque of the single cell was determined by inspection of variations of high frequency and mass transport resistances with the clamping torque. The results of the electrochemical impedance analysis show that the non-uniform assembly pressure can deteriorate the fuel cell performance by increasing the ohmic resistance and the mass transport limitation. Break-in procedure of the short stack was monitored and it is indicated that the ohmic resistance as well as the charge transfer resistance decrease to specified values as the break-in process proceeds. The effect of output current on the impedance plots of the short stack was also investigated. (author)

  3. Reverse Logistics

    OpenAIRE

    Kulikova, Olga

    2016-01-01

    This thesis was focused on the analysis of the concept of reverse logistics and actual reverse processes which are implemented in mining industry and finding solutions for the optimization of reverse logistics in this sphere. The objective of this paper was the assessment of the development of reverse logistics in mining industry on the example of potash production. The theoretical part was based on reverse logistics and mining waste related literature and provided foundations for further...

  4. Antibacterial and anti-adherence effects of a plant extract mixture (PEM) and its individual constituent extracts (Psidium sp., Mangifera sp., and Mentha sp.) on single- and dual-species biofilms

    Science.gov (United States)

    Shafiei, Zaleha; Haji Abdul Rahim, Zubaidah; Thurairajah, Nalina

    2016-01-01

    Background Plant extracts mixture (PEM) and its individual constituent plant extracts(Psidium sp., Mangifera sp., Mentha sp.) are known to have an anti-adhering effect towards oral bacteria in the single-species biofilm. To date, the adhering ability of the early and late plaque colonisers (Streptococcus sanguinis and Streptococcus mutans) to PEM-treated experimental pellicle have not been investigated in dual-species biofilms. Methods Fresh leaves of these plants were used in the preparation of the respective aqueous extract decoctions. The minimum inhibitory concentration (MIC) of the extracts towards S. sanguinis ATCC BAA-1455 and S. mutans ATCC 25175 was determined using a two-fold serial microdilution method. The sum of fractional inhibitory concentration (ΣFIC) index of PEM and its constituent plant extracts was calculated using the MIC values of the plants. The minimum bactericidal concentration (MBC) of the plant extracts was also determined. The anti-adherence effect of the plant extracts (individually and mixed) was carried out by developing simulated S. sanguinis and S. mutans respectively in single- and dual-species of biofilms in the Nordini’s Artificial Mouth (NAM) model system in which the experimental pellicle was pretreated with the plant extract before bacterial inoculation. The bacterial population in the respective biofilms was quantified using ten-fold serial dilutions method and expressed as colony forming unit per ml (CFU/ml). The bacterial population was also viewed using Scanning Electron Microscope (SEM). All experiments were done in triplicate. Results The PEM compared with its respective constituent plants showed the lowest MIC towards S. sanguinis (3.81 mg/ml) and S. mutans (1.91 mg/ml) and exhibited a synergistic effect. The Psidium sp. (15.24 mg/ml) and, PEM and Psidium sp. (30.48 mg/ml) showed the lowest MBC towards S. sanguinis and S. mutans respectively. The anti-adherence effect of the PEM and its respective constituent plants

  5. Optimized High Temperature PEM Fuel Cell & High Pressure PEM Electrolyser for Regenerative Fuel Cell Systems in GEO Telecommunication Satellites

    Directory of Open Access Journals (Sweden)

    Farnes Jarle

    2017-01-01

    Full Text Available Next generation telecommunication satellites will demand increasingly more power. Power levels up to 50 kW are foreseen for the next decades. Battery technology that can sustain up to 50 kW for eclipse lengths of up to 72 minutes will represent a major impact on the total mass of the satellite, even with new Li-ion battery technologies. Regenerative fuel cell systems (RFCS were identified years ago as a possible alternative to rechargeable batteries. CMR Prototech has investigated this technology in a series of projects initiated by ESA focusing on both the essential fuel cell technology, demonstration of cycle performance of a RFCS, corresponding to 15 years in orbit, as well as the very important reactants storage systems. In the last two years the development has been focused towards optimising the key elements of the RFCS; the HTPEM fuel cell and the High Pressure PEM electrolyser. In these ESA activities the main target has been to optimise the design by reducing the mass and at the same time improve the performance, thus increasing the specific energy. This paper will present the latest development, including the main results, showing that significant steps have been taken to increase TRL on these key components.

  6. A Pilot-scale Demonstration of Reverse Osmosis Unit for Treatment of Coal-bed Methane Co-produced Water and Its Modeling

    Institute of Scientific and Technical Information of China (English)

    钱智; 刘新春; 余志晟; 张洪勋; 琚宜文

    2012-01-01

    This study presents the first demonstration project in China for treatment of coal-bed methane(CBM) co-produced water and recycling.The work aims to provide a research and innovation base for solving the pollution problem of CBM extraction water.The reverse osmosis(RO) unit is applied to the treatment of CBM co-produced water.The results indicate that system operation is stable,the removal efficiency of the total dissolved solids(TDS) is as high as 97.98%,and Fe,Mn,and F-are almost completely removed.There is no suspended solids(SS) detected in the treated water.Furthermore,a model for the RO membrane separation process is developed to describe the quantitative relationship between key physical quantities-membrane length,flow velocity,salt concentration,driving pressure and water recovery rate,and the water recovery restriction equation based on mass balance is developed.This model provides a theoretical support for the RO system design and optimization.The TDS in the CBM co-produced water are removed to meet the "drinking water standards" and "groundwater quality standards" of China and can be used as drinking water,irrigation water,and livestock watering.In addition,the cost for treatment of CBM co-produced water is assessed,and the RO technology is an efficient and cost-effective treatment method to remove pollutants.

  7. Design, Fabrication and Prototype testing of a Chip Integrated Micro PEM Fuel Cell Accumulator combined On-Board Range Extender

    Science.gov (United States)

    Balakrishnan, A.; Mueller, C.; Reinecke, H.

    2014-11-01

    In this work we present the design, fabrication and prototype testing of Chip Integrated Micro PEM Fuel Cell Accumulator (CIμ-PFCA) combined On-Board Range Extender (O-BRE). CIμ-PFCA is silicon based micro-PEM fuel cell system with an integrated hydrogen storage feature (palladium metal hydride), the run time of CIμ-PFCA is dependent on the stored hydrogen, and in order to extend its run time an O-BRE is realized (catalytic hydrolysis of chemical hydride, NaBH4. Combining the CIμ-PFCA and O-BRE on a system level have few important design requirements to be considered; hydrogen regulation, gas -liquid separator between the CIμ-PFCA and the O-RE. The usage of traditional techniques to regulate hydrogen (tubes), gas-liquid phase membranes (porous membrane separators) are less desirable in the micro domain, due to its space constraint. Our approach is to use a passive hydrogen regulation and gas-liquid phase separation concept; to use palladium membrane. Palladium regulates hydrogen by concentration diffusion, and its property to selectively adsorb only hydrogen is used as a passive gas-liquid phase separator. Proof of concept is shown by realizing a prototype system. The system is an assembly of CIμ-PFCA, palladium membrane and the O-BRE. The CIμ-PFCA consist of 2 individually processed silicon chips, copper supported palladium membrane realized by electroplating followed by high temperature annealing process under inter atmosphere and the O-BRE is realized out of a polymer substrate by micromilling process with platinum coated structures, which functions as a catalyst for the hydrolysis of NaBH4. The functionality of the assembled prototype system is demonstrated by the measuring a unit cell (area 1 mm2) when driven by the catalytic hydrolysis of chemical hydride (NaBH4 and the prototype system shows run time more than 15 hours.

  8. Validation of a Waste Heat Recovery Model for a 1kW PEM Fuel Cell using Thermoelectric Generator

    Science.gov (United States)

    Saufi Sulaiman, M.; Mohamed, W. A. N. W.; Singh, B.; Fitrie Ghazali, M.

    2017-08-01

    Fuel cell is a device that generates electricity through electrochemical reaction between hydrogen and oxygen. A major by-product of the exothermic reaction is waste heat. The recovery of this waste heat has been subject to research on order to improve the overall energy utilization. However, nearly all of the studies concentrate on high temperature fuel cells using advanced thermodynamic cycles due to the high quality of waste heat. The method, characteristics and challenges in harvesting waste heat from a low temperature fuel cell using a direct energy conversion device is explored in this publication. A heat recovery system for an open cathode 1kW Proton Exchange Membrane fuel cell (PEM FC) was developed using a single unit of thermoelectric generator (TEG) attached to a heat pipe. Power output of the fuel cell was varied to obtain the performance of TEG at different stack temperatures. Natural and forced convections modes of cooling were applied to the TEG cold side. This is to simulate the conditions of a mini fuel cell vehicle at rest and in motion. The experimental results were analysed and a mathematical model based on the thermal circuit analogy was developed and compared. Forced convection mode resulted in higher temperature difference, output voltage and maximum power which are 3.3°C, 33.5 mV, and 113.96mW respectively. The heat recovery system for 1 kW Proton Exchange Membrane fuel cell (PEM FC) using single TEG was successfully established and improved the electrical production of fuel cell. Moreover, the experimental results obtained was in a good agreement with theoretical results.

  9. Simulation of the PEM fuel cell hybrid power train of an automated guided vehicle and comparison with experimental results

    NARCIS (Netherlands)

    Bram Veenhuizen; J.C.N. Bosma

    2009-01-01

    At HAN University research has been started into the development of a PEM fuel cell hybrid power train to be used in an automated guided vehicle. For this purpose a test facility is used with the possibility to test all important functional aspects of a PEM fuel cell hybrid power train. In this

  10. Simulation of the PEM fuel cell hybrid power train of an automated guided vehicle and comparison with experimental results

    NARCIS (Netherlands)

    Veenhuizen, Bram; Bosma, J.C.N.

    2009-01-01

    At HAN University research has been started into the development of a PEM fuel cell hybrid power train to be used in an automated guided vehicle. For this purpose a test facility is used with the possibility to test all important functional aspects of a PEM fuel cell hybrid power train. In this pape

  11. Advanced Materials for PEM-Based Fuel Cell Systems

    Energy Technology Data Exchange (ETDEWEB)

    James E. McGrath

    2005-10-26

    Proton exchange membrane fuel cells (PEMFCs) are quickly becoming attractive alternative energy sources for transportation, stationary power, and small electronics due to the increasing cost and environmental hazards of traditional fossil fuels. Two main classes of PEMFCs include hydrogen/air or hydrogen/oxygen fuel cells and direct methanol fuel cells (DMFCs). The current benchmark membrane for both types of PEMFCs is Nafion, a perfluorinated sulfonated copolymer made by DuPont. Nafion copolymers exhibit good thermal and chemical stability, as well as very high proton conductivity under hydrated conditions at temperatures below 80 °C. However, application of these membranes is limited due to their high methanol permeability and loss of conductivity at high temperatures and low relative humidities. These deficiencies have led to the search for improved materials for proton exchange membranes. Potential PEMs should have good thermal, hydrolytic, and oxidative stability, high proton conductivity, selective permeability, and mechanical durability over long periods of time. Poly(arylene ether)s, polyimides, polybenzimidazoles, and polyphenylenes are among the most widely investigated candidates for PEMs. Poly(arylene ether)s are a promising class of proton exchange membranes due to their excellent thermal and chemical stability and high glass transition temperatures. High proton conductivity can be achieved through post-sulfonation of poly(arylene ether) materials, but this most often results in very high water sorption or even water solubility. Our research has shown that directly polymerized poly(arylene ether) copolymers show important advantages over traditional post-sulfonated systems and also address the concerns with Nafion membranes. These properties were evaluated and correlated with morphology, structure-property relationships, and

  12. Advanced Materials for PEM-Based Fuel Cell Systems

    Energy Technology Data Exchange (ETDEWEB)

    James E. McGrath; Donald G. Baird; Michael von Spakovsky

    2005-10-26

    Proton exchange membrane fuel cells (PEMFCs) are quickly becoming attractive alternative energy sources for transportation, stationary power, and small electronics due to the increasing cost and environmental hazards of traditional fossil fuels. Two main classes of PEMFCs include hydrogen/air or hydrogen/oxygen fuel cells and direct methanol fuel cells (DMFCs). The current benchmark membrane for both types of PEMFCs is Nafion, a perfluorinated sulfonated copolymer made by DuPont. Nafion copolymers exhibit good thermal and chemical stability, as well as very high proton conductivity under hydrated conditions at temperatures below 80 degrees C. However, application of these membranes is limited due to their high methanol permeability and loss of conductivity at high temperatures and low relative humidities. These deficiencies have led to the search for improved materials for proton exchange membranes. Potential PEMs should have good thermal, hydrolytic, and oxidative stability, high proton conductivity, selective permeability, and mechanical durability over long periods of time. Poly(arylene ether)s, polyimides, polybenzimidazoles, and polyphenylenes are among the most widely investigated candidates for PEMs. Poly(arylene ether)s are a promising class of proton exchange membranes due to their excellent thermal and chemical stability and high glass transition temperatures. High proton conductivity can be achieved through post-sulfonation of poly(arylene ether) materials, but this most often results in very high water sorption or even water solubility. Our research has shown that directly polymerized poly(arylene ether) copolymers show important advantages over traditional post-sulfonated systems and also address the concerns with Nafion membranes. These properties were evaluated and correlated with morphology, structure-property relationships, and states of water in the membranes. Further improvements in properties were achieved through incorporation of inorganic

  13. PEM fuel cell catalyst degradation mechanism and mathematical modeling

    Science.gov (United States)

    Bi, Wu

    The durability of carbon-supported platinum oxygen reduction electrocatalysts is one of the limiting factors for their commercial applications in PEM fuel cell cathodes. In this work, we applied both experimental and numerical tools to study Pt/C catalyst degradation mechanisms. An accelerated catalyst degradation protocol through cycling the cathode potential in a square-wave profile was applied to study cell performances, Pt/C catalyst ORR activity, and active surface area losses. Post-mortem analyses of cathode Pt particle size were conducted by X-ray diffraction. Changes of platinum distributions in CCMs were studied by SEM/EDS analyses with surface coated Au as the reference element. The mechanisms of platinum deposition in membrane were investigated. It was confirmed by the SEM/EDS Pt distribution analyses that the deposited Pt atoms originated from the cathode. It was hypothesized that dissolved Pt ions from the cathode diffused into the membrane and were reduced by the permeated hydrogen from the anode. These deposited Pt atoms catalyzed the combustion of permeated oxygen and hydrogen. Pt band was predicted and experimentally confirmed at the location where the permeated hydrogen and oxygen completely reacted with each other. An active research thrust for PEM fuel cells is the development of membranes for high temperature (above 80°C) and low humidity operations. However a large tradeoff the benefits running fuel cell at relatively high temperatures was observed due to the accelerated cathode degradation processes. And at low humidity conditions, the cathode degradation rate decreased due to the slow transport of soluble platinum ions in possible narrowed/limited water (or ionic) channel networks in polymer electrolytes. From the Pt dissolution experiments in 0.5 M HClO4 solution, large positive effects of holding potentials on dissolution rates and soluble Pt concentrations were observed. Without an external holding potential, Pt dissolution rate was

  14. Heat sources in proton exchange membrane (PEM) fuel cells

    Science.gov (United States)

    Ramousse, Julien; Lottin, Olivier; Didierjean, Sophie; Maillet, Denis

    In order to model accurately heat transfer in PEM fuel cell, a particular attention had to be paid to the assessment of heat sources in the cell. Although the total amount of heat released is easily computed from its voltage, local heat sources quantification and localization are not simple. This paper is thus a discussion about heat sources/sinks distribution in a single cell, for which many bold assumptions are encountered in the literature. The heat sources or sinks under consideration are: (1) half-reactions entropy, (2) electrochemical activation, (3) water sorption/desorption at the GDL/membrane interfaces, (4) Joule effect in the membrane and (5) water phase change in the GDL. A detailed thermodynamic study leads to the conclusion that the anodic half-reaction is exothermic (Δ Sr ev a = - 226 J mo l-1 K-1) , instead of being athermic as supposed in most of the thermal studies. As a consequence, the cathodic half-reaction is endothermic (Δ Sr ev c = + 62.8 J mo l-1 K-1) , which results in a heat sink at the cathode side, proportional to the current. In the same way, depending on the water flux through the membrane, sorption can create a large heat sink at one electrode and an equivalent heat source at the other. Water phase change in the GDL - condensation/evaporation - results in heat sources/sinks that should also be taken into account. All these issues are addressed in order to properly set the basis of heat transfer modeling in the cell.

  15. Coupling RTD and EIS modelling to characterize operating non-uniformities on PEM cathodes

    Science.gov (United States)

    Deseure, Jonathan

    Large PEM cells will be used in future proton exchange membrane fuel cell (PEMFC) power plants and appropriate tools are therefore be needed to study their behaviour. One approach to understanding single cell behaviour involves using mathematical models. The numerous techniques used in this work to describe PEM electrode behaviour require different scientific disciplines: chemical engineering and electrochemistry. This study proposes combining residence time distribution (RTD) and electrochemical impedance spectroscopy (EIS). The investigation focuses on cathodic DC and AC responses where over-voltage is critical. Results demonstrate that although gas distribution does not cause additional loops on impedance diagrams, it is strongly related to both the shape and amplitude of these diagrams. The simulations have drawn attention to operating conditions that can threaten the life of the PEM cell: under these setting points EIS method is not sufficient to detect this risk.

  16. Comparison of temperature distributions inside a PEM fuel cell with parallel and interdigitated gas distributors

    Science.gov (United States)

    Hwang, J. J.; Liu, S. J.

    A comparison of the temperature distributions in a proton exchange membrane (PEM) fuel cell between the parallel-flow gas distributors and the interdigitated gas distributor has been discussed in detail. An electrochemical-thermal coupled numerical model in a five-layer membrane-electrode assembly (MEA) is developed. The temperatures for the reactant fuels as well as the carbon fibers in the porous electrode are predicted by using a CFD technique. The overpotential across the MEA is varied to examine its effect on the temperature distributions of the PEM fuel cell. It is found that both the fuel temperature and the carbon fiber temperature are increased with increasing the total overpotential. In addition, the fuel and carbon-fiber temperature distributions are significantly affected by the flow pattern that cast on the gas distributor. Replacing the parallel-flow gas distributor by the interdigitated gas distributor will increase the local maximum temperature inside the PEM fuel cell.

  17. Separation of hydrogen from a hydrogen/methane mixture using PEM fuel cell technology

    Energy Technology Data Exchange (ETDEWEB)

    Ibeh, B.; Gardner, C.; Ternan, M. [Ottawa Univ., ON (Canada). Dept. of Chemical Engineering

    2007-07-01

    This paper presented a newly developed method for transporting hydrogen in natural gas pipelines which involves the use of an electrochemical separation process using proton exchange membrane (PEM) fuel cells. It described an experimental procedure in which a single cell 25 cm{sup 2} PEM fuel cell was used and anode polarization curves were determined. Hydrogen partial pressure was reduced as current density was increased to strengthen the anode potential. Hydrogen separation equations were presented in addition to a comparison of calculated and experimental polarization curves. Separation efficiencies were also described. Results of the experiment showed that hydrogen could be separated from the hydrogen-natural gas mixture through the use of PEM technology. It was also observed that methane behaved as an inert gas at low temperatures. Details of costs and capitalized costs for the separation process were also presented. Last, the presentation discussed issues related to electrode fouling by oxidation products and the efficiency of separation processes. tabs., figs.

  18. Analysing Gas-Liquid Flow in PEM Electrolyser Micro-Channels (Poster)

    OpenAIRE

    Lafmejani, Saeed Sadeghi; Olesen, Anders Christian; Kær, Søren Knudsen

    2016-01-01

    One means of increasing the hydrogen yield to cost ratio of a PEM water electrolyser, is to increase the operating current density. However, at high current densities (higher than 1 A/cm2), management of heat and mass transfer in the anode current collector and channel becomes crucial and can lead to hot spots. Management of heat and fluid flow through the micro-channels play a great role in the capability of PEM water electrolysis when working at high current densities. Despite, many studies...

  19. Adaptive Process Controls and Ultrasonics for High Temperature PEM MEA Manufacture

    Energy Technology Data Exchange (ETDEWEB)

    Walczyk, Daniel F. [Rensselaer Polytechnic Inst., Troy, NY (United States)

    2015-08-26

    The purpose of this 5-year DOE-sponsored project was to address major process bottlenecks associated with fuel cell manufacturing. New technologies were developed to significantly reduce pressing cycle time for high temperature PEM membrane electrode assembly (MEA) through the use of novel, robust ultrasonic (U/S) bonding processes along with low temperature (<100°C) PEM MEAs. In addition, greater manufacturing uniformity and performance was achieved through (a) an investigation into the causes of excessive variation in ultrasonically and thermally bonded MEAs using more diagnostics applied during the entire fabrication and cell build process, and (b) development of rapid, yet simple quality control measurement techniques for use by industry.

  20. THE DEVELOPMENT OF CONTROL SYSTEM OF REVERSE OSMOSIS WATER TREATMENT UNIT%反渗透水处理设备电导率控制系统的研制

    Institute of Scientific and Technical Information of China (English)

    李修仁; 秦旭达; 哈鼎文

    2001-01-01

    本文介绍了一种模糊控制器,应用于反渗透水处理设备中,可实现电导率实时自动控制,提高了反渗透水处理过程中设备工作效率和水的利用率。%This paper introduces a fuzzy controller that authors designed. It was applied to reverse osmosis water treatment unit, realizing the conductivity auto-controlled and raising the working efficiency of the equipment and the utilization ratio of water remarkably in the reverse osmosis process.

  1. PEM fuel cells with injection moulded bipolar plates of highly filled graphite compounds; PEM-Brennstoffzellen mit spritzgegossenen Bipolarplatten aus hochgefuelltem Graphit-Compound

    Energy Technology Data Exchange (ETDEWEB)

    Kreuz, Can

    2008-04-11

    This work concerns with the injection moulding of highly filled graphite compounds to bipolar plates for PEM fuel cells in a power output range between 100 - 500 Watts. A particular focus is laid on the combination of the three multidisciplinary scopes like material development, production technology and component development / design. The results of the work are specified by the process-oriented characterisation of the developed and manufactured bipolar plates as well as their application in a functioning fuel cell. (orig.)

  2. Next Generation Bipolar Plates for Automotive PEM Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Adrianowycz, Orest; Norley, Julian; Stuart, David J; Flaherty, David; Wayne, Ryan; ; Williams, Warren; Tietze, Roger; Nguyen, Yen-Loan H; Zawodzinski, Tom; Pietrasz, Patrick

    2010-04-15

    The results of a successful U.S. Department of Energy (DoE) funded two-year $2.9 MM program lead by GrafTech International Inc. (GrafTech) are reported and summarized. The program goal was to develop the next generation of high temperature proton exchange membrane (PEM) fuel cell bipolar plates for use in transportation fuel cell applications operating at temperatures up to 120 °C. The bipolar plate composite developed during the program is based on GrafTech’s GRAFCELL resin impregnated flexible graphite technology and makes use of a high temperature Huntsman Advanced Materials resin system which extends the upper use temperature of the composite to the DoE target. High temperature performance of the new composite is achieved with the added benefit of improvements in strength, modulus, and dimensional stability over the incumbent resin systems. Other physical properties, including thermal and electrical conductivity of the new composite are identical to or not adversely affected by the new resin system. Using the new bipolar plate composite system, machined plates were fabricated and tested in high temperature single-cell fuel cells operating at 120 °C for over 1100 hours by Case Western Reserve University. Final verification of performance was done on embossed full-size plates which were fabricated and glued into bipolar plates by GrafTech. Stack testing was done on a 10-cell full-sized stack under a simulated drive cycle protocol by Ballard Power Systems. Freeze-thaw performance was conducted by Ballard on a separate 5-cell stack and shown to be within specification. A third stack was assembled and shipped to Argonne National Laboratory for independent performance verification. Manufacturing cost estimate for the production of the new bipolar plate composite at current and high volume production scenarios was performed by Directed Technologies Inc. (DTI). The production cost estimates were consistent with previous DoE cost estimates performed by DTI for the

  3. Understanding of ammonia transport in PEM fuel cells

    Science.gov (United States)

    Jung, Myunghee

    This dissertation investigates ammonia (NH3) as a fuel contaminant to the anode in Proton Exchange Membrane Fuel Cells (PEMFCs). Since NH 3 is fed to the anode in a gas phase and transferred to the cathode, the effect of a contaminant is distributed through MEA and quite complicated. This study is focused on the investigation of mechanism of NH3 transport and the isolation of multiple effects to degrade the performance of fuel cell. An External Reference Electrode (ERE) was employed to decouple the effect of individual electrode and explain the mechanism of NH3 contamination. A mechanism of NH3 transport is proposed and supported by data for various inlet conditions in a N2/N2 laboratory-scale fuel cell at Open Circuit Conditions (OCC). With a commercialized GORE(TM) PRIMEA RTM 5631 MEAs at 70°C, data were obtained utilizing a material balance technique, which uses an ion selective electrode (ISE) to determine the concentration of ammonium ion in the process streams. The results indicate that ammonia is not transported across the membrane when the feeds to both electrodes are dry. However, with humidified feeds ammonia was transported from the anode to the cathode. The data also indicate the water content of in the MEA is the critical factor that causes NH3 crossover in the MEA. Diffusion coefficients of NH3 in MEA are also calculated at different relative humilities. An ERE was developed for PEM fuel cell by using a NafionRTM strip which was used to understand contamination mechanism. The voltage of anode electrode relative to ERE was measured during a polarization curve. The data showed the measurement of individual electrode potential was extremely affected by the misalignment between two electrodes. We compare the overpotential measured from the reference electrode and the calculated overpotential from subtracting the cell voltages between neat hydrogen and a 25 ppm CO in H 2 stream at same current. The studies indicated that the overpotentials obtained from

  4. Real life testing of a Hybrid PEM Fuel Cell Bus

    Science.gov (United States)

    Folkesson, Anders; Andersson, Christian; Alvfors, Per; Alaküla, Mats; Overgaard, Lars

    Fuel cells produce low quantities of local emissions, if any, and are therefore one of the most promising alternatives to internal combustion engines as the main power source in future vehicles. It is likely that urban buses will be among the first commercial applications for fuel cells in vehicles. This is due to the fact that urban buses are highly visible for the public, they contribute significantly to air pollution in urban areas, they have small limitations in weight and volume and fuelling is handled via a centralised infrastructure. Results and experiences from real life measurements of energy flows in a Scania Hybrid PEM Fuel Cell Concept Bus are presented in this paper. The tests consist of measurements during several standard duty cycles. The efficiency of the fuel cell system and of the complete vehicle are presented and discussed. The net efficiency of the fuel cell system was approximately 40% and the fuel consumption of the concept bus is between 42 and 48% lower compared to a standard Scania bus. Energy recovery by regenerative braking saves up 28% energy. Bus subsystems such as the pneumatic system for door opening, suspension and brakes, the hydraulic power steering, the 24 V grid, the water pump and the cooling fans consume approximately 7% of the energy in the fuel input or 17% of the net power output from the fuel cell system. The bus was built by a number of companies in a project partly financed by the European Commission's Joule programme. The comprehensive testing is partly financed by the Swedish programme "Den Gröna Bilen" (The Green Car). A 50 kW el fuel cell system is the power source and a high voltage battery pack works as an energy buffer and power booster. The fuel, compressed hydrogen, is stored in two high-pressure stainless steel vessels mounted on the roof of the bus. The bus has a series hybrid electric driveline with wheel hub motors with a maximum power of 100 kW. Hybrid Fuel Cell Buses have a big potential, but there are

  5. Identification and monitoring of a PEM electrolyser based on dynamical modelling

    Energy Technology Data Exchange (ETDEWEB)

    Lebbal, M.E.; Lecoeuche, S. [Ecole des Mines de Douai, Departement Informatique et Automatique, 941 rue Charles Bourseul, 59508 Douai Cedex (France)

    2009-07-15

    To improve the efficiency and the safety of hydrogen electrolysis stations, some technological studies are still under investigation both on methods and materials. As methods, control, monitoring and diagnosis algorithms are relevant tools. This work focuses on the dynamical modelling and the monitoring of Proton Exchange Membrane (PEM) electrolyser. Our contribution consists of three parts: to propose a model of an analytical-dynamical PEM electrolyser, dedicated to control and monitoring; to identify the model parameters and to propose adequate monitoring tools. The proposed model is deduced from physical laws and electrochemical equations and consists of a steady-state electric model coupled with a dynamic thermal model. The estimation of the model parameters is achieved using identification and data fitting techniques based on experimental measurements. Taking into account the information given by the proposed analytical model and the experimentation data (temperature T, voltage U and current I) given by a PEM electrolyser, the model parameters are identified. After estimating the dynamical model, model-based diagnosis is used to monitor the PEM electrolyser and to ensure its safety. We illustrate how our algorithm can detect and isolate faults on actuators, on sensors or on electrolyser system. (author)

  6. PEM fuel cell cost minimization using ``Design For Manufacture and Assembly`` techniques

    Energy Technology Data Exchange (ETDEWEB)

    Lomax, F.D. Jr.; James, B.D. [Directed Technologies, Inc., Arlington, VA (United States); Mooradian, R.P. [Ford Motor Co., Dearborn, MI (United States)

    1997-12-31

    Polymer Electrolyte Membrane (PEM) fuel cells fueled with direct hydrogen have demonstrated substantial technical potential to replace Internal Combustion Engines (ICE`s) in light duty vehicles. Such a transition to a hydrogen economy offers the potential of substantial benefits from reduced criteria and greenhouse emissions as well as reduced foreign fuel dependence. Research conducted for the Ford Motor Co. under a US Department of Energy contract suggests that hydrogen fuel, when used in a fuel cell vehicle (FCV), can achieve a cost per vehicle mile less than or equal to the gasoline cost per mile when used in an ICE vehicle. However, fuel cost parity is not sufficient to ensure overall economic success: the PEM fuel cell power system itself must be of comparable cost to the ICE. To ascertain if low cost production of PEM fuel cells is feasible, a powerful set of mechanical engineering tools collectively referred to as Design for Manufacture and Assembly (DFMA) has been applied to several representative PEM fuel cell designs. The preliminary results of this work are encouraging, as presented.

  7. Comparison of the Relative Effectiveness of Different Kinds of Reinforcers: A PEM Approach

    Science.gov (United States)

    Ma, Hsen-Hsing

    2009-01-01

    The purpose of the present study was to apply the percentage of data points exceeding the median of baseline phase (PEM) approach for a meta-analysis of single-case experiments to compare the relative effectiveness of different kinds of reinforcers used in behavior modification. Altogether 153 studies were located, which produced 1091 effect…

  8. Tuning surface hydrophilicity/hydrophobicity of hydrocarbon proton exchange membranes (PEMs).

    Science.gov (United States)

    He, Chenfeng; Mighri, Frej; Guiver, Michael D; Kaliaguine, Serge

    2016-03-15

    The effect of annealing on the surface hydrophilicity of various representative classes of hydrocarbon-based proton exchange membranes (PEMs) is investigated. In all cases, a more hydrophilic membrane surface develops after annealing at elevated temperatures. The annealing time also had some influence, but in different ways depending on the class of PEM. Longer annealing times resulted in more hydrophilic membrane surfaces for copolymerized sulfonated poly(ether ether ketone) (SPEEK-HQ), while the opposite behavior occurred in sulfonated poly(aryl ether ether ketone) (Ph-SPEEK), sulfonated poly(aryl ether ether ketone ketone) (Ph-m-SPEEKK) and sulfonated poly (aryl ether ether nitrile) (SPAEEN-B). Increased surface hydrophilicity upon annealing results from ionic cluster decomposition, according to the "Eisenberg-Hird-Moore model" (EHM). The increased surface hydrophilicity is supported by contact angle (CA) measurements, and the cluster decomposition is auxiliarily supported by probing the level of atomic sulfur (sulfonic acid) within different surface depths using angle-dependent XPS as well as ATR-FTIR. Membrane acidification leads to more hydrophilic surfaces by elimination of the hydrogen bonding that occurs between strongly-bound residual solvent (dimethylacetamide, DMAc) and PEM sulfonic acid groups. The study of physicochemical tuning of surface hydrophilicity/hydrophobicity of PEMs by annealing and acidification provides insights for improving membrane electrode assembly (MEA) fabrication in fuel cell (FC).

  9. VOF modelling of gas–liquid flow in PEM water electrolysis cell micro-channels

    DEFF Research Database (Denmark)

    Lafmejani, Saeed Sadeghi; Olesen, Anders Christian; Kær, Søren Knudsen

    2017-01-01

    In this study, the gaseliquid flow through an interdigitated anode flow field of a PEM water electrolysis cell (PEMEC) is analysed using a three-dimensional, transient, computational fluid dynamics (CFD) model. To account for two-phase flow, the volume of fluid (VOF) method in ANSYS Fluent 17...

  10. Thermal Modelling and Validation of PEM Fuel Cell System for Automotive Applications

    DEFF Research Database (Denmark)

    Liso, Vincenzo; Nielsen, Mads Pagh; Al Shakhshir, Saher

    2017-01-01

    In this study we analyze main parameters affecting PEM fuel cell performance at different humidity. The main mechanisms affecting the membrane hydration are identified. Cell performance under a range of humidity conditions was tested. The understanding of the physical phenomena is important to de...

  11. On-road particle number measurements using a portable emission measurement system (PEMS)

    Science.gov (United States)

    Gallus, Jens; Kirchner, Ulf; Vogt, Rainer; Börensen, Christoph; Benter, Thorsten

    2016-01-01

    In this study the on-road particle number (PN) performance of a Euro-5 direct-injection (DI) gasoline passenger car was investigated. PN emissions were measured using the prototype of a portable emission measurement system (PEMS). PN PEMS correlations with chassis dynamometer tests show a good agreement with a chassis dynamometer set-up down to emissions in the range of 1·1010 #/km. Parallel on-line soot measurements by a photo acoustic soot sensor (PASS) were applied as independent measurement technique and indicate a good on-road performance for the PN-PEMS. PN-to-soot ratios were 1.3·1012 #/mg, which was comparable for both test cell and on-road measurements. During on-road trips different driving styles as well as different road types were investigated. Comparisons to the world harmonized light-duty test cycle (WLTC) 5.3 and to European field operational test (euroFOT) data indicate the PEMS trips to be representative for normal driving. Driving situations in varying traffic seem to be a major contributor to a high test-to-test variability of PN emissions. However, there is a trend to increasing PN emissions with more severe driving styles. A cold start effect is clearly visible for PN, especially at low ambient temperatures down to 8 °C.

  12. Phased-Array Monolithic PEM for FT Spectrometry With Applications in Explosive Detection and CB Defense

    Science.gov (United States)

    2008-12-01

    1 PHASED-ARRAY MONOLITHIC PEM FOR FT SPECTROMETRY WITH APPLICATIONS IN EXPLOSIVE DETECTION AND CB DEFENSE Tudor N. Buican* Semiotic ...PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Semiotic Engineering Associates LLC Albuquerque, NM 87108 8. PERFORMING ORGANIZATION REPORT NUMBER 9

  13. Optimization of a thermoelectric generator subsystem for high temperature PEM fuel cell exhaust heat recovery

    DEFF Research Database (Denmark)

    Gao, Xin; Andreasen, Søren Juhl; Kær, Søren Knudsen

    2014-01-01

    In previous work, a thermoelectric (TE) exhaust heat recovery subsystem for a high temperature polymer electrolyte membrane (HT-PEM) fuel cell stack was developed and modeled. Numerical simulations were conducted and have identified an optimized subsystem configuration and 4 types of compact heat...

  14. Performance of a PEM water electrolyser using a TaC-supported iridium oxide electrocatalyst

    DEFF Research Database (Denmark)

    Polonský, J.; Mazúr, P.; Paidar, M.

    2014-01-01

    Polymer electrolyte membrane (PEM) water electrolysis is an attractive way of producing carbon-free hydrogen. One of the drawbacks of this method is the need for precious metal-based electrocatalysts. This calls for a highly efficient utilization of the precious metal, which can be obtained by di...

  15. Characterisation and Modelling of a High Temperature PEM Fuel Cell Stack using Electrochemical Impedance Spectroscopy

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Jespersen, Jesper Lebæk; Schaltz, Erik

    2009-01-01

    temperature PEM (HTPEM) fuel cell stack. A Labview virtual instrument has been developed to perform the signal generation and data acquisition which is needed to perform EIS. The typical output of an EIS measurement on a fuel cell, is a Nyquist plot, which shows the imaginary and real part of the impedance...

  16. Improved dynamic performance of hybrid PEM fuel cells and ultracapacitors for portable applications

    Energy Technology Data Exchange (ETDEWEB)

    Yalcinoz, T. [Department of Electrical and Computer Engineering, University of South Alabama, Mobile, AL 36688 (United States); Department of Electrical and Electronic Engineering, Nigde University, Nigde 51200 (Turkey); Alam, M.S. [Department of Electrical and Computer Engineering, University of South Alabama, Mobile, AL 36688 (United States)

    2008-04-15

    Transient power demand fluctuations and maintaining high energy density are important for many portable devices. Small fuel cells are potentially good candidates as alternative energy sources for portable applications. Hybrid power sources have some inherent properties which may be effectively utilized to improve the efficiency and dynamic response of the system. In this paper, an improved dynamic model considering the characteristics of the temperature and equivalent internal resistance is presented for proton exchange membrane (PEM) fuel cells. The dynamic behavior of a system with hybrid PEM fuel cells and an ultracapacitor bank is simulated. The hybrid PEM fuel cell/ultracapacitor bank system is used for powering a portable device (such as a laptop computer). The power requirement of a laptop computer varies significantly under different operation conditions. The analytical models of the hybrid system with PEM fuel cells and an ultracapacitor bank are designed and simulated by developing a detailed simulation software using Matlab, Simulink and SimPowerSystems Blockset for portable applications. (author)

  17. Patriot Script 1.0.13 User Guide for PEM 1.3.2

    Energy Technology Data Exchange (ETDEWEB)

    Cleland, Timothy James [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kubicek, Deborah Ann [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Stroud, Phillip David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Cuellar-Hengartner, Leticia [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mathis, Mark [Descartes Labs, Inc., Los Alamos, NM (United States)

    2015-11-02

    This document provides an updated user guide for Patriot Script Version 1.0.13, for release with PEM 1.3.1 (LAUR-1422817) that adds description and instructions for the new excursion capability (see section 4.5.1).

  18. Modelling of a High Temperature PEM Fuel Cell Stack using Electrochemical Impedance Spectroscopy

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Jespersen, Jesper Lebæk; Kær, Søren Knudsen

    2008-01-01

    This work presents the development of an equivalent circuit model of a 65 cell high temperature PEM (HTPEM) fuel cell stack using Electrochemical Impedance Spectroscopy (EIS). The HTPEM fuel cell membranes used are PBI-based and uses phosphoric acid as proton conductor. The operating temperature...

  19. Effects of Straight and Serpentine Flow Field Designs on Temperature Distribution in Proton Exchange Membrane (PEM Fuel Cell

    Directory of Open Access Journals (Sweden)

    Zaman Izzuddin

    2016-01-01

    Full Text Available Proton exchange membrane fuel cells or sometimes called as polymer electrolyte membrane (PEM fuel cells is a device for energy transformation in a changing process from one form of energy to another form of energy. It became as an alternative especially for future use in stationary and vehicular applications. PEM fuel cells provide high efficiency and power density with null emission, low operating temperature, quickly start and long life. One of the aspects that are crucial in optimizing the PEM fuel cells performance is a flow field geometry. In this paper, a simulation case of PEM fuel cells was simulated to determine effects of a straight and serpentine flow field on temperature distribution in PEM fuel cells. ANSYS Fluent software was used to simulate 3-dimensional models of single PEM fuel cells in order to determine the effects of changes in the geometry flow field on temperature distributions. Results showed that the serpentine flow field design produces a better temperature distribution along the membrane. The simulation result shows a good agreement with the experiment, thus boost a higher confidence in the results to determine the effectiveness of the flow field design in PEM fuel cells.

  20. Carbon nanotubes as electrode substrate material for PEM fuel cells; Kohlenstoff-Nanoroehrchen als Elektrodenmaterial fuer PEM-Brennstoffzellen

    Energy Technology Data Exchange (ETDEWEB)

    Soehn, Matthias

    2010-06-21

    This thesis reports an enhanced method to deposit nanoscaled noble metal catalysts (Pt/Ru) uniformly on carbon nanotubes based on wet chemical reduction of anorganic precursors via ethylene glycol. This well-known method is widely used to deposit noble metal catalyst particles on carbon black. Unfortunately, carbon nanotubes tend to agglomerate and therefore form bundles which cannot be penetrated by the precursor. Thus, effectiveness of the substrate is reduced. The new method prevents this by suspending the CNTs in butyl acetate by means of ultrasonic dispersion leading to a homogenous distribution. Because the butyl acetate is almost unpolar, it is nearly immiscible with the water-based ethylene glycol mixture. This problem has been solved by adding liquid Nafion {sup registered} which acts as an emulsifying agent. Thus an emulsion is created by ultrasonic treatment. This results in 30 {mu}m-sized droplets of butyl acetate with a layer of CNTs and Nafion {sup registered}. The large interface to the ethylene glycol phase yields a large surface for homogenous catalyst deposition. The prepared samples showed a narrow size distribution ({+-}0.5 nm) of small noble metal particles with loading up to 50% by weight and an average particle size of 3 nm. They are investigated using XRD, SEM, TEM, TGA-MS and CV. The added Nafion {sup registered} improves catalyst utilisation by establishing a proton conductive path to the catalyst particles. Furthermore, different manufacturing techniques for the CNT electrodes are evaluated. Thin layer Membrane-Electrode-Assemblies (MEAs) are prepared by the airbrush technique. Electrode thickness, composition and structure as well as membrane thickness is varied and the MEAs are tested in a single-cell hydrogen-oxygen-fed PEM fuel cell. The cells are characterised by cyclic IV curves which are recorded over an extended period of time, showing power densities up to 770mWcm-2 at a platinum loading of 0.3mgcm-2. Additionally, the MEAs are

  1. A flow channel design procedure for PEM fuel cells with effective water removal

    Science.gov (United States)

    Li, Xianguo; Sabir, Imran; Park, Jaewan

    Proper water management in polymer electrolyte membrane (PEM) fuel cells is critical to achieve the potential of PEM fuel cells. Membrane electrolyte requires full hydration in order to function as proton conductor, often achieved by fully humidifying the anode and cathode reactant gas streams. On the other hand, water is also produced in the cell due to electrochemical reaction. The combined effect is that liquid water forms in the cell structure and water flooding deteriorates the cell performance significantly. In the present study, a design procedure has been developed for flow channels on bipolar plates that can effectively remove water from the PEM fuel cells. The main design philosophy is based on the determination of an appropriate pressure drop along the flow channel so that all the liquid water in the cell is evaporated and removed from, or carried out of, the cell by the gas stream in the flow channel. At the same time, the gas stream in the flow channel is maintained fully saturated in order to prevent membrane electrolyte dehydration. Sample flow channels have been designed, manufactured and tested for five different cell sizes of 50, 100, 200, 300 and 441 cm 2. Similar cell performance has been measured for these five significantly different cell sizes, indicating that scaling of the PEM fuel cells is possible if liquid water flooding or membrane dehydration can be avoided during the cell operation. It is observed that no liquid water flows out of the cell at the anode and cathode channel exits for the present designed cells during the performance tests, and virtually no liquid water content in the cell structure has been measured by the neutron imaging technique. These measurements indicate that the present design procedure can provide flow channels that can effectively remove water in the PEM fuel cell structure.

  2. A flow channel design procedure for PEM fuel cells with effective water removal

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xianguo; Sabir, Imran; Park, Jaewan [Department of Mechanical Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)

    2007-01-01

    Proper water management in polymer electrolyte membrane (PEM) fuel cells is critical to achieve the potential of PEM fuel cells. Membrane electrolyte requires full hydration in order to function as proton conductor, often achieved by fully humidifying the anode and cathode reactant gas streams. On the other hand, water is also produced in the cell due to electrochemical reaction. The combined effect is that liquid water forms in the cell structure and water flooding deteriorates the cell performance significantly. In the present study, a design procedure has been developed for flow channels on bipolar plates that can effectively remove water from the PEM fuel cells. The main design philosophy is based on the determination of an appropriate pressure drop along the flow channel so that all the liquid water in the cell is evaporated and removed from, or carried out of, the cell by the gas stream in the flow channel. At the same time, the gas stream in the flow channel is maintained fully saturated in order to prevent membrane electrolyte dehydration. Sample flow channels have been designed, manufactured and tested for five different cell sizes of 50, 100, 200, 300 and 441cm{sup 2}. Similar cell performance has been measured for these five significantly different cell sizes, indicating that scaling of the PEM fuel cells is possible if liquid water flooding or membrane dehydration can be avoided during the cell operation. It is observed that no liquid water flows out of the cell at the anode and cathode channel exits for the present designed cells during the performance tests, and virtually no liquid water content in the cell structure has been measured by the neutron imaging technique. These measurements indicate that the present design procedure can provide flow channels that can effectively remove water in the PEM fuel cell structure. (author)

  3. Reverse logistics

    NARCIS (Netherlands)

    M.P. de Brito (Marisa); S.D.P. Flapper; R. Dekker (Rommert)

    2002-01-01

    textabstractThis paper gives an overview of scientific literature that describes and discusses cases of reverse logistics activities in practice. Over sixty case studies are considered. Based on these studies we are able to indicate critical factors for the practice of reverse logistics. In addi

  4. Final Report - MEA and Stack Durability for PEM Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Yandrasits, Michael A.

    2008-02-15

    Proton exchange membrane fuel cells are expected to change the landscape of power generation over the next ten years. For this to be realized one of the most significant challenges to be met for stationary systems is lifetime, where 40,000 hours of operation with less than 10% decay is desired. This project conducted fundamental studies on the durability of membrane electrode assemblies (MEAs) and fuel cell stack systems with the expectation that knowledge gained from this project will be applied toward the design and manufacture of MEAs and stack systems to meet DOE’s 2010 stationary fuel cell stack systems targets. The focus of this project was PEM fuel cell durability – understanding the issues that limit MEA and fuel cell system lifetime, developing mitigation strategies to address the lifetime issues and demonstration of the effectiveness of the mitigation strategies by system testing. To that end, several discoveries were made that contributed to the fundamental understanding of MEA degradation mechanisms. (1) The classically held belief that membrane degradation is solely due to end-group “unzipping” is incorrect; there are other functional groups present in the ionomer that are susceptible to chemical attack. (2) The rate of membrane degradation can be greatly slowed or possibly eliminated through the use of additives that scavenge peroxide or peroxyl radicals. (3) Characterization of GDL using dry gases is incorrect due to the fact that fuel cells operate utilizing humidified gases. The proper characterization method involves using wet gas streams and measuring capillary pressure as demonstrated in this project. (4) Not all Platinum on carbon catalysts are created equally – the major factor impacting catalyst durability is the type of carbon used as the support. (5) System operating conditions have a significant impact of lifetime – the lifetime was increased by an order of magnitude by changing the load profile while all other variables remain

  5. Experimental validation of modelling tools for a PEM fuel cell; Validation experimentale d'outils de modelisation d'une pile a combustible de type PEM

    Energy Technology Data Exchange (ETDEWEB)

    Boillot, M.

    2005-10-15

    In this work, a global view of the phenomena occurring in a PEM fuel cell is given. An original methodology was developed in order to determine the main parameters: thermodynamics, kinetics and transport phenomena. The gas flow in bipolar plates was characterised using experimental determination of residence time distributions and numerical simulations. Kinetics of both electrochemical reactions were analysed feeding the cell by diluted gases. In this part, the diffusion of reactants in the membrane electrodes assembly was taken into account. Finally, the relationship between humidity and electrical performance was investigated and the ohmic resistance of the cell was estimated. (author)

  6. Development and test of 2 kW natural gas reformers for high and low temperature PEM fuel cells. Project report 2; Udvikling/afproevning af 2 kW naturgasreformere for hoej- og lavtemperatur PEM-braendselsceller. Projektrapport 2

    Energy Technology Data Exchange (ETDEWEB)

    Wit, J. de [Dansk Gasteknisk Center (Denmark); Bech-Madsen, J. [IRD (Denmark); Bandur, V. [DTU (Denmark); Bartholin, N. [DPS (Denmark)

    2005-11-15

    The use of fuel cells for combined heat and power generation has advantages as regards technology and usability compared to existing CHP technology. Special characteristics for a fuel cell plant are: 1) It can be constructed in modules over a wide power range, 2) The efficiency is significantly independent of size, 3) It is noiseless, 4) A flexible coupling between power and heat production, 5) As there is no movable parts, long service check intervals can be expected, 6) Low emissions. The fuel for fuel cells is hydrogen and optimal utilization and CO{sub 2} reduction will require a 'hydrogen society'. While waiting for a 'hydrogen society' to arise, it is possible to use central or on-site reformers that convert natural gas to hydrogen. There will be some CO{sub 2} emission connected to energy use. The objective of the present project has been development and test of on-site reformers (fuel processors) for hydrogen supply to respectively high and low temperature PEM fuel cells aiming at use in single family houses. Sulphur cleaning, reformers, and lab-scale coupling with fuel cell KV units have been developed and tested during the project, as well as development and test of periphery equipment. (BA)

  7. Development of a portable PEM fuel cell system with bipolar plates consisting an electronically conductive thermoplastic Compound material; Entwicklung eines portablen PEM-Brennstoffzellensystems mit Bipolarplatten aus einem elektronisch leitfaehigen thermoplastischen Compound-Material

    Energy Technology Data Exchange (ETDEWEB)

    Niemzig, O.C.

    2005-07-18

    In order to meet the cost targets of PEM fuel cells for commercialization significant cost reductions of cell stack components like membrane/electrode assemblies and bipolar plates have become key aspects of research and development. Central topics of his work are the bipolar plates and humidification for portable applications. Best results concerning conductivity of an extensive screening of a variety of carbon polymer compounds with polypropylene as matrix could be achieved with the carbon black/graphite/polypropylene-base system. Successful tests of this material in a fuel cell stack could be performed as well as the proof of suitability concerning material- and manufacturing costs. Dependent on application a decrease of material cost to 2 Euro/kg to 1,8 Euro/kW seems to be possible. Finally bipolar plates consisting of a selected carbon polymer compound were successfully integrated and tested in a 20-cell stack which was implemented in a portable PEFC-demonstrator unit with a power output between 50 and 150 W. (orig.)

  8. Growth of Three Lettuce Cultivars in NASA's HDU PEM During the 2010 DRATS Test

    Science.gov (United States)

    Stutte, Gary W.; Newsham, Gerard; Wheeler, Raymond

    2011-01-01

    NASA's 2010 Desert Research and Technology Studies (DRATS) of the VEGGIE Food Production System in the Habitat Demonstration Unit (HDU) Pressurized Excursion Module (PEM) was the first operational evaluation of salad crop production technology in a NASA analog test. Rooting media and slow release fertilizers were evaluated for three lettuce cultivars that had shown promise as candidates for a surface based food production system. These tests involved comparing growth, color and quality of the lettuce cultivars grown under VEGGIE LED array (Orbitec, Madison, WI) or Biomass Production System for Education ((BSEe), Orbitec, Madison, WI) compact fluorescent lamps using a gravity feed water delivery system. Mission relevant conditions of CO2, temperature and RH were maintained using controlled environment chambers (EGC, Chagrin Falls, OH). Growth data was obtained for the two red leaf lettuce cultivars, Outredgeous and Firecracker, and the green Bibb lettuce cultivar, Flandria. Growth and quality was evaluated using different concentrations (7.5 g/L and 15 g/L) of commercial slow release fertilizer (Osmocote Plus 15-9-12, Scotts, Maryville, OH) and Nutricote 18-6-8 (Florikan, Sarasota, FL) in either a peat/vermiculite media (sunshine LP5 MiX, Sungro, Bellview, WA) or calcined montmorillonite clay [(arcillite,)Turface Proleague, Profile LLC, Buffalo Grove, IL]. The commercial peat/vermiculite mix generally resulted in larger plants than those grown in arcillite. Increasing the concentration of Osmocote from 7.5 to 15 g/L increased the height, dry mass, and leaf area of lettuce cultivars. In contrast, there was a decrease in growth parameters when concentration of Nutricote was increased from 7.5 to 15 g/L. The best growth was obtained with the 7.5 g/L Nutricote using a commercial peat/vermiculite mixture. This media was used for field testing VEGGIE plant system in the 2010 DRAT test. The VEGGIE nutrient delivery system worked well, was able to be maintained by multiple

  9. Simulation and evaluation of a high resolution VIP PEM system with a dedicated LM-OSEM algorithm

    Science.gov (United States)

    Uzun, D.; De Lorenzo, G.; Kolstein, M.; Chmeissani, M.

    2014-05-01

    Over the last two decades there have been a growing number of designs for positron emission tomography (PET) cameras optimized to image the breast. These devices, commonly known as positron emission mammography (PEM) cameras allow much more spatial resolution by putting the photon detectors directly on the breast. PEM cameras have a compact geometry with a restricted field of view (FOV) thus exhibiting higher performance and lower cost than large whole body PET scanners. Typical PEM designs are based on scintillators such as bismuth germanate (BGO), lutetium oxorthosilicate (LSO) or lutetium yttrium orthosicilate (LYSO), and characterized by large parallax error due to deficiency of the depth of interaction (DOI) information from crystals. In the case of parallel geometry PEM, large parallax error results in poor image resolution along the vertical axis. In the framework of the Voxel Imaging PET (VIP) pathfinder project, we propose a high resolution PEM scanner based on pixelated solid-state CdTe detectors. The pixel PEM device with a millimeter-size pixel pitch provides an excellent spatial resolution in all directions 8 times better than standard commercial devices with a point spread function (PSF) of 1 mm full width at half maximum (FWHM) and excellent energy resolution of down to 1.6% FWHM at 511 keV photons at room temperature. The system is capable to detect down to 1 mm diameter hot spheres in warm background.

  10. Mechanical behaviour of membrane electrode assembly (MEA during cold start of PEM fuel cell from subzero environment temperature

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2015-01-01

    Full Text Available Durability is one of the most critical remaining issues impeding successful commercialization of broad PEM fuel cell transportation energy applications. Automotive fuel cells are likely to operate with neat hydrogen under load-following or load-levelled modes and be expected to withstand variations in environmental conditions, particularly in the context of temperature and atmospheric composition. In addition, they are also required to survive over the course of their expected operational lifetimes i.e., around 5,500 hrs, while undergoing as many as 30,000 startup/shutdown cycles. Cold start capability and survivability of proton exchange membrane fuel cells (PEM in a subzero environment temperature remain a challenge for automotive applications. A key component of increasing the durability of PEM fuel cells is studying the behaviour of the membrane electrode assembly (MEA at the heart of the fuel cell. The present work investigates how the mechanical behaviour of MEA are influenced during cold start of the PEM fuel cell from subzero environment temperatures. Full three-dimensional, non-isothermal computational fluid dynamics model of a PEM fuel cell has been developed to simulate the stresses inside the PEM fuel cell, which are occurring during fuel cell assembly (bolt assembling, and the stresses arise during fuel cell running due to the changes of temperature and relative humidity. The model is shown to be able to understand the many interacting, complex electrochemical, transport phenomena, and stresses distribution that have limited experimental data.

  11. Analysis of the Coupling Behavior of PEM Fuel Cells and DC-DC Converters

    Directory of Open Access Journals (Sweden)

    Achim Kienle

    2009-03-01

    Full Text Available The connection between PEM fuel cells and common DC-DC converters is examined. The analysis is model-based and done for boost, buck and buck-boost converters. In a first step, the effect of the converter ripples upon the PEM fuel cell is shown. They introduce oscillations in the fuel cell. Their appearance is explained, discussed and possibilities for their suppression are given. After that, the overall behaviors of the coupled fuel cell-converter systems are analyzed. It is shown, that neither stationary multiplicities nor oscillations can be introduced by the couplings and therefore separate control approaches for both the PEMFC and the DC-DC converters are applicable.

  12. Analysis of the coupling behavior of PEM fuel cells and DC-DC converters

    Energy Technology Data Exchange (ETDEWEB)

    Groetsch, M.; Mangold, M.; Kienle, A. [Max Planck Institute for Dynamics of Complex Technical Systems, Process Synthesis and Process Dynamics Group, Sandtorstrasse 1, 39106 Magdeburg (Germany); Kienle, A. [Otto-von-Guericke-Universitaet Magdeburg, Lehrstuhl fuer Automatisierungstechnik / Modellbildung, Universitaetsplatz 2, 39106 Magdeburg (Germany)

    2009-07-01

    The connection between PEM fuel cells and common DC-DC converters is examined. The analysis is model-based and done for boost, buck and buck-boost converters. In a first step, the effect of the converter ripples upon the PEM fuel cell is shown. They introduce oscillations in the fuel cell. Their appearance is explained, discussed and possibilities for their suppression are given. After that, the overall behaviors of the coupled fuel cell-converter systems are analyzed. It is shown, that neither stationary multiplicities nor oscillations can be introduced by the couplings and therefore separate control approaches for both the PEMFC and the DC-DC converters are applicable. (author)

  13. Influence from sea water constituents on the efficiency of water electrolysis by PEM-cells

    DEFF Research Database (Denmark)

    Agersted, Karsten; Bentzen, Janet Jonna; Yde-Andersen, S.

    Among the sea-water specific impurities tested, magnesium has the most profound effect on PEM-cell degradation. Significant amounts of the cation was retrieved in the NAFION®-membrane structure after testing. Degradation was seen from a magnesium concentration as low as 3 10-7 mol/l, and increasing...... with concentration it led to a 86% increase of the area specific resistance at a concentration of 3 10-5 mol/l; equivalent to a conductivity of ~5 μS/cm. Other species (Cl-, Na+, SO4 2- ) seems to affect, though slowly, the performance negatively. If PEM will be used for electrolysis it seems therefore necessary...... to purify the feed water to ~1 μS/cm or even further while particularly focusing on the concentrations of polyvalent cations. e.g. magnesium....

  14. A Mathematical Model for Predicting the Life of PEM Fuel Cell Membranes Subjected to Hydration Cycling

    CERN Document Server

    Burlatsky, S F; O'Neill, J; Atrazhev, V V; Varyukhin, A N; Dmitriev, D V; Erikhman, N S

    2013-01-01

    Under typical PEM fuel cell operating conditions, part of membrane electrode assembly is subjected to humidity cycling due to variation of inlet gas RH and/or flow rate. Cyclic membrane hydration/dehydration would cause cyclic swelling/shrinking of the unconstrained membrane. In a constrained membrane, it causes cyclic stress resulting in mechanical failure in the area adjacent to the gas inlet. A mathematical modeling framework for prediction of the lifetime of a PEM FC membrane subjected to hydration cycling is developed in this paper. The model predicts membrane lifetime as a function of RH cycling amplitude and membrane mechanical properties. The modeling framework consists of three model components: a fuel cell RH distribution model, a hydration/dehydration induced stress model that predicts stress distribution in the membrane, and a damage accrual model that predicts membrane life-time. Short descriptions of the model components along with overall framework are presented in the paper. The model was used...

  15. The Hardware Implementation of Demonstrator Air Independent Electric Supply System Based on Pem Fuel Cell

    Directory of Open Access Journals (Sweden)

    Grzeczka G.

    2016-12-01

    Full Text Available The paper presents results of the research project whose the main goal was to build a technology demonstrator of an electric supply system based on the PEM fuel cell. The electric supply system is dedicated to operation on a board of a submarine during emergency situations. The underwater conditions influence on a specific architecture of supply subsystems of the PEM fuel cell system. In this case the fuel cell stack is supplied by both clean hydrogen and clean oxygen stored in pressurized tanks. The hydrogen has to be delivered in a closed loop, while the oxygen can be delivered in a closed or an open loop. In the technology demonstrator, the supply of the fuel cell stack by the hydrogen in the closed loop and the oxygen in the open loop with a precise control of its flow were used.

  16. Separation of hydrogen from hydrogen/ethylene mixtures using PEM fuel cell technology

    Energy Technology Data Exchange (ETDEWEB)

    Doucet, R.; Gardner, C.L. [Department of Chemical Engineering, Centre for Catalysis Research and Innovation, University of Ottawa, 161 Louis Pasteur, Ottawa, Ontario K1N 6N5 (Canada); Ternan, M. [EnPross Inc., 147 Banning Road, Ottawa, Ontario K2L 1C5 (Canada)

    2009-01-15

    This article is a study of the feasibility of electrochemically separating hydrogen from hydrogen/ethylene mixtures. Experimental results are presented for the performance of the anode of a proton exchange membrane (PEM) fuel cell that is used to separate hydrogen/ethylene mixtures. Experiments were performed using a single cell PEM fuel cell. The experimental results show that, to a large extent, the ethylene reacts with the hydrogen in the anode chamber to form ethane. In spite of this reaction, it is still possible to separate a significant portion of the hydrogen and options for improving the separation efficiency are discussed. A zero-dimensional mathematical model of the hydrogen separation and hydrogenation process has been developed and it has been shown that this model gives generally good agreement with the experimental results. (author)

  17. Design, Modeling and Energy Management of a PEM Fuel Cell / Supercapacitor Hybrid Vehicle

    Directory of Open Access Journals (Sweden)

    Wahib Andari

    2017-01-01

    Full Text Available This work concerns the study and the modeling of hybrid Proton Exchange Membrane (PEM Fuel Cell electric vehicle. In fact, the paper deals with the model description of the powertrain which includes two energy sources: a PEM Fuel Cell as a primary source and a supercapacitor as a secondary source. The architecture is two degrees of freedom permitting a stability of the DC bus voltage. The hybridation of primary source with an energy storage system can improve vehicle dynamic response during transients and hydrogen consumption. The proposed energy management algorithm allows us to have a minimum hydrogen consumption. This algorithm is based on supercapacitor state of charge (SOC control and acceleration/deceleration phases making possible braking energy recovery. The proposed model is simulated and tested using Matlab/Simulink software allowing rapid transitions between sources. The obtained results with the New European Driving Cycle (NEDC cycle demonstrate a 22% gain in hydrogen consumption.

  18. Simulation results of a veto counter for the ClearPEM

    CERN Document Server

    Trummer, J; Lecoq, P

    2009-01-01

    The Crystal Clear Collaboration (CCC) has built a prototype of a novel positron emission tomograph dedicated to functional breast imaging, the ClearPEM. The ClearPEM uses the common radio pharmaceutical FDG for imaging cancer. As FDG is a rather non-specific radio tracer, it accumulates not only in cancer cells but in all cells with a high energy consumption, such as the heart and liver. This fact poses a problem especially in breast imaging, where the vicinity of the heart and other organs to the breast leads to a high background noise level in the scanner. In this work, a veto counter to reduce the background is described. Different configurations and their effectiveness were studied using the GATE simulation package.

  19. Simulation of the Internal Transport Phenomena for PEM Fuel Cells with Different Modes of Flow

    Institute of Scientific and Technical Information of China (English)

    胡鸣若; 朱新坚; 顾安忠

    2004-01-01

    A numerical model for proton exchange membrane (PEM) fuel cell is developed, which can simulate such basic transport phenomena as gas-liquid two-phase flow in a working fuel cell. Boundary conditions for both the conventional and the interdigitated modes of flow are presented on a three-dimensional basis. Numerical techniques for this model are discussed in detail. Validation shows good agreement between simulating results and experimental data. Furthermore, internal transport phenomena are discussed and compared for PEM fuel cells with conventional and interdigitated flows. It is found that the dead-ended structure of an interdigitated flow does increase the oxygen mass fraction and decrease the liquid water saturation in the gas diffusion layer as compared to the conventional mode of flow. However, the cathode humidification is important for an interdigitated flow to acquire better performance than a conventional flow fuel cell.

  20. DanDan. Final report. [PEM fuel cells for back-up power and UPS]; DanDan. Slutrapport

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2012-08-15

    The project has provided valuable results for the partners involved, and has resulted in the construction and demonstration of a modular UPS system that can be used with fuel cells. Dantherm Power has provided a 5 kW fuel cell module, based on LT-pem technology, for use in the demonstration and testing facility. The function of the unit is verified by both internal testing and demonstrations from at third parties were it currently is set up to perform tests regarding lifetime. The development of a DC / DC converter, was made. The module has been tested under various conditions, and the development process has resulted in detailed specs of both technique and test process. The module has been tested both in laboratory environment and demonstrated at third parties. The module is part of the systems described in connection with initial test runs - performed at strategic partners - and in connection with the demonstration of the systems both in Japan and in South Africa. The modules are presently in a stage of demonstration, while subjected to substantial service life tests. The purchased reformers are part of the systems used for demonstration in the project and as such they will supply valuable data trough the comprehensive test and verification program initiated. (LN)

  1. Process for recycling components of a PEM fuel cell membrane electrode assembly

    Science.gov (United States)

    Shore, Lawrence [Edison, NJ

    2012-02-28

    The membrane electrode assembly (MEA) of a PEM fuel cell can be recycled by contacting the MEA with a lower alkyl alcohol solvent which separates the membrane from the anode and cathode layers of the assembly. The resulting solution containing both the polymer membrane and supported noble metal catalysts can be heated under mild conditions to disperse the polymer membrane as particles and the supported noble metal catalysts and polymer membrane particles separated by known filtration means.

  2. Optimal Control of a PEM Fuel Cell for the Inputs Minimization

    Directory of Open Access Journals (Sweden)

    José de Jesús Rubio

    2014-01-01

    Full Text Available The trajectory tracking problem of a proton exchange membrane (PEM fuel cell is considered. To solve this problem, an optimal controller is proposed. The optimal technique has the objective that the system states should reach the desired trajectories while the inputs are minimized. The proposed controller uses the Hamilton-Jacobi-Bellman method where its Riccati equation is considered as an adaptive function. The effectiveness of the proposed technique is verified by two simulations.

  3. Detection of Liquid Water in PEM Fuel Cells' Channels: Design and Validation of a Microsensor.

    OpenAIRE

    Conteau, Delphine; Bonnet, Caroline; Funfschilling, Denis; Weber, Mathieu; Didierjean, Sophie; Lapicque, François

    2010-01-01

    Abstract Suitable water management is a critical issue to reach the full potential of PEM fuel cells: whereas the membrane must be hydrated enough, liquid droplets formed by water in excess can block the flow in the gas distribution channels and hinder the fuel cell performance. In order to detect the presence of droplets in cathode flow channel, an electrochemical sensor has been developed and tested in a dedicated emulation cell. It is based on the widely used principle of two-el...

  4. Dynamic Characteristics of PEM-FC/Woody Biomass Engine Hybrid Micro Grid

    Science.gov (United States)

    Obara, Shin'ya; Kito, Shunsuke; Hoshi, Akira; Sasaki, Seizi

    The combustion exhaust heat of woody biomass engine using Stirling cycle is high temperature. This exhaust heat is used for the city gas reforming reaction of a proton exchange membrane fuel cell (PEM-FC) system. The woody biomass engine generator has the characteristic that the greenhouse gas amount of emission with power generation is greatly reducible. In this paper, the micro grid system that introduces PEM-FC/woody biomass engine hybrid cogeneration (PWHC) is proposed. It depends on the dynamic characteristics of the grid for the power quality at the time of load fluctuation being added to the micro grid. Especially, the dynamic characteristics of the independent micro grid are important on security of power quality. So, in this paper, the response characteristic of PEM-FC and woody biomass engine was investigated by the experiment and the numerical analysis. Furthermore, the response characteristic of the PWHC independent micro grid including auxiliary machinery was investigated by the numerical simulation. Moreover, an improvement of dynamic characteristics is proposed using the method of adding proportional-plus-integral control to PWHC. If woody biomass engine is introduced into a house, 10.2s will be required to stabilize power quality at the maximum. On the other hand, when woody biomass engine corresponds to a base load and PEM-FC corresponds to the load exceeding the base load, settling time is less than 1.6 s. In this study, relation between the system configuration of the PWHC micro grid and the dynamic characteristics of the power was clarified.

  5. A Comparison of Two Air Compressors for PEM Fuel Cell Systems

    OpenAIRE

    Kulp, Galen W.

    2001-01-01

    Proton exchange membrane (PEM) fuel cells are considered one of the best potential alternative power sources for automobiles. For this application, high efficiency and high power density are required. Pressurizing the fuel cell system can give higher efficiency, higher power density and better water balance characteristics for the fuel cell, but pressurization uses a percentage of the fuel cell output power. The compressor used to elevate the pressure has a direct effect on the system effi...

  6. Fuzzy Logic Based Control of Power of PEM Fuel Cell System for Residential Application

    Directory of Open Access Journals (Sweden)

    Khaled MAMMAR

    2009-07-01

    Full Text Available This paper presents a dynamic model of Fuel cell system for residential power generation. The models proposed include a fuel cell stack model, reformer model and DC/AC inverter model. Furthermore a fuzzy logic (FLC controller is used to control active power of PEM fuel cell system. The controller modifies the hydrogen flow feedback from the terminal load. Simulation results confirmed the high performance capability of the fuzzy logic controller to control power generation.

  7. Fuzzy Logic Based Control of Power of PEM Fuel Cell System for Residential Application

    OpenAIRE

    Khaled MAMMAR; CHAKER, Abdelkader

    2009-01-01

    This paper presents a dynamic model of Fuel cell system for residential power generation. The models proposed include a fuel cell stack model, reformer model and DC/AC inverter model. Furthermore a fuzzy logic (FLC) controller is used to control active power of PEM fuel cell system. The controller modifies the hydrogen flow feedback from the terminal load. Simulation results confirmed the high performance capability of the fuzzy logic controller to control power generation.

  8. Modelling of a High Temperature PEM Fuel Cell Stack using Electrochemical Impedance Spectroscopy

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Jespersen, Jesper Lebæk; Kær, Søren Knudsen

    In designing and controlling fuel cell sys-tems it is advantageous having models predicting the behavior of the fuel cells in steady-state as well as in dynamic ope-ration. This work examines the use of electro-chemical impedance spectroscopy (EIS) for characterizing and developing a model for a ...... for a high temperature PEM (HTPEM) fuel cell stack. A Labview virtual interface has been developed to perform the signal generation and acquisition which is needed to perform EIS....

  9. WC as a non-platinum hydrogen evolution electrocatalyst for high temperature PEM water electrolysers

    DEFF Research Database (Denmark)

    Nikiforov, Aleksey; Petrushina, Irina; Christensen, Erik

    2012-01-01

    Tungsten carbide (WC) nanopowder was tested as a non-platinum cathode electrocatalyst for polymer electrolyte membrane (PEM) water electrolysers, operating at elevated temperatures. It was prepared in thermal plasma reactor with confined plasma jet from WO3 precursor in combination with CH4...... carburizing agent. The results of the investigation showed that the activity of tungsten carbide as cathode electrocatalyst increases significantly with temperature and this effect is more pronounced than for platinum, especially, at 150 °C....

  10. Modeling of a PEM Fuel Cell Stack using Partial Least Squares and Artificial Neural Networks

    Energy Technology Data Exchange (ETDEWEB)

    Han, In-Su; Shin, Hyun Khil [GS Caltex Corp, Daejeon (Korea, Republic of)

    2015-04-15

    We present two data-driven modeling methods, partial least square (PLS) and artificial neural network (ANN), to predict the major operating and performance variables of a polymer electrolyte membrane (PEM) fuel cell stack. PLS and ANN models were constructed using the experimental data obtained from the testing of a 30 kW-class PEM fuel cell stack, and then were compared with each other in terms of their prediction and computational performances. To reduce the complexity of the models, we combined a variables importance on PLS projection (VIP) as a variable selection method into the modeling procedure in which the predictor variables are selected from a set of input operation variables. The modeling results showed that the ANN models outperformed the PLS models in predicting the average cell voltage and cathode outlet temperature of the fuel cell stack. However, the PLS models also offered satisfactory prediction performances although they can only capture linear correlations between the predictor and output variables. Depending on the degree of modeling accuracy and speed, both ANN and PLS models can be employed for performance predictions, offline and online optimizations, controls, and fault diagnoses in the field of PEM fuel cell designs and operations.

  11. Mathematical modeling of channel-porous layer interfaces in PEM fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Ehrhardt, M.; Fuhrmann, J.; Holzbecher, E.; Linke, A.

    2008-07-01

    In proton exchange membrane (PEM) fuel cells, the transport of the fuel to the active zones, and the removal of the reaction products are realized using a combination of channels and porous diffusion layers. In order to improve existing mathematical and numerical models of PEM fuel cells, a deeper understanding of the coupling of the flow processes in the channels and diffusion layers is necessary. After discussing different mathematical models for PEM fuel cells, the work focuses on the description of the coupling of the free flow in the channel region with the filtration velocity in the porous diffusion layer as well as interface conditions between them. The difficulty in finding effective coupling conditions at the interface between the channel flow and the membrane lies in the fact that often the orders of the corresponding differential operators are different, e.g., when using stationary (Navier-)Stokes and Darcy's equation. Alternatively, using the Brinkman model for the porous media this difficulty does not occur. We review different interface conditions, including the well-known Beavers-Joseph-Saffman boundary condition and its recent improvement by Le Bars and Worster. (orig.)

  12. The effect of material properties on the performance of a new geometry PEM fuel cell

    Science.gov (United States)

    Khazaee, Iman; Ghazikhani, Mohsen

    2012-05-01

    In this paper a computational dynamics model for duct-shaped geometry proton exchange membrane (PEM) fuel cell was used to investigate the effect of changing gas diffusion layer and membrane properties on the performances, current density and gas concentration. The proposed model is a full cell model, which includes all the parts of the PEM fuel cell, flow channels, gas diffusion electrodes, catalyst layers and the membrane. Coupled transport and electrochemical kinetics equations are solved in a single domain; therefore no interfacial boundary condition is required at the internal boundaries between cell components. This computational fluid dynamics code is used as the direct problem solver, which is used to simulate the 2-dimensional mass, momentum and species transport phenomena as well as the electron- and proton-transfer process taking place in a PEMFC that cannot be investigated experimentally. The results show that by increasing the thickness and decreasing the porosity of GDL the performance of the cell enhances that it is different with planner PEM fuel cell. Also the results show that by increasing the thermal conductivity of the GDL and membrane, the overall cell performance increases.

  13. A three-dimensional PEM fuel cell model with consistent treatment of water transport in MEA

    Science.gov (United States)

    Meng, Hua

    In this paper, a three-dimensional PEM fuel cell model with a consistent water transport treatment in the membrane electrode assembly (MEA) has been developed. In this new PEM fuel cell model, the conservation equation of the water concentration is solved in the gas channels, gas diffusion layers, and catalyst layers while a conservation equation of the water content is established in the membrane. These two equations are connected using a set of internal boundary conditions based on the thermodynamic phase equilibrium and flux equality at the interface of the membrane and the catalyst layer. The existing fictitious water concentration treatment, which assumes thermodynamic phase equilibrium between the water content in the membrane phase and the water concentration, is applied in the two catalyst layers to consider water transport in the membrane phase. Since all the other conservation equations are still developed and solved in the single-domain framework without resort to interfacial boundary conditions, the present new PEM fuel cell model is termed as a mixed-domain method. Results from this mixed-domain approach have been compared extensively with those from the single-domain method, showing good accuracy in terms of not only cell performances and current distributions but also water content variations in the membrane.

  14. Analysis of transport phenomena and electrochemical reactions in a micro PEM fuel cell

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2014-01-01

    Full Text Available Micro-fuel cells are considered as promising electrochemical power sources in portable electronic devices. The presence of microelectromechanical system (MEMS technology makes it possible to manufacture the miniaturized fuel cell systems. The majority of research on micro-scale fuel cells is aimed at micro-power applications. Performance of micro-fuel cells are closely related to many factors, such as designs and operating conditions. CFD modeling and simulation for heat and mass transport in micro PEM fuel cells are being used extensively in researches and industrial applications to gain better understanding of the fundamental processes and to optimize the micro fuel cell designs before building a prototype for engineering application. In this research, full three-dimensional, non-isothermal computational fluid dynamics model of a micro proton exchange membrane (PEM fuel cell has been developed. This comprehensive model accounts for the major transport phenomena such as convective and diffusive heat and mass transfer, electrode kinetics, transport and phase-change mechanism of water, and potential fields in a micro PEM fuel cell. The model explains many interacting, complex electrochemical, and transport phenomena that cannot be studied experimentally. Three-dimensional results of the species profiles, temperature distribution, potential distribution, and local current density distribution are presented and analysed, with the focus on the physical insight and fundamental understanding.

  15. A 3D model for PEM fuel cells operated on reformate

    Science.gov (United States)

    Zhou, Tianhong; Liu, Hongtan

    A three-dimensional mathematical model for PEM fuel cells operated on reformate is developed based on our previous established fuel cell model [Int. J. Transport Phenomena 3 (2001) 177], by incorporating the adsorption and oxidation kinetics of CO on platinum surface proposed by Springer et al. [Proceedings of the Electrochemical Society, Montreal, Canada, 1997; J. Electrochem. Soc. 148 (2001) A11]. This model is capable of studying the effect of CO poisoning as well as the hydrogen dilution effect by inert gases. The adsorption and oxidation kinetics of CO on a platinum surface are incorporated in the source terms of the species equations; thus, the basic form of the mathematical equations are the same as those used for PEM fuel cells operated on pure hydrogen. With this model, we can obtain detailed information on the CO poisoning and variation of CO and hydrogen concentrations inside the anode. The results from this 3D model reveal many new phenomena that cannot be obtained from previous 1D or 2D models. Results of the effects of various operating and design parameters, such as anode flow rate, gas diffuser porosity, gas diffuser thickness, and the width of the collector plate shoulder, are also presented. The modeling results demonstrate the value of this model as a design and optimization tool for the anode of PEM fuel cells operating on reformate.

  16. Highly Sulfonated Diamine Synthesized Polyimides and Protic Ionic Liquid Composite Membranes Improve PEM Conductivity

    Directory of Open Access Journals (Sweden)

    Bor-Kuan Chen

    2015-06-01

    Full Text Available A novel sulfonated diamine was synthesized from 1,4-bis(4-aminophenoxy benzene [pBAB]. Sulfonated polyimides (SPIs were synthesized from sulfonated pBAB, 1,4-bis(4-aminophenoxy-2-sulfonic acid benzenesulfonic acid [pBABTS], various diamines and aromatic dianhydrides. Composite proton exchange membranes (PEMs made of novel SPIs and a protic ionic liquid (PIL 1-vinyl-3-H-imidazolium trifluoromethanesulfonate [VIm][OTf] showed substantially increased conductivity. We prepared an SPI/PIL composite PEM using pBABTS, 4,4′-(9-fluorenylidene dianiline (9FDA as diamine, 3,3′,4,4′-diphenylsulfone tetracarboxylic dianhydride (DSDA as dianhydride and 40 wt % [VIm][OTf] with a high conductivity of 16 mS/cm at 120 °C and anhydrous condition. pBABTS offered better conductivity, since the chemical structure had more sulfonated groups that provide increased conductivity. The new composite membrane could be a promising anhydrous or low-humidity PEM for intermediate or high-temperature fuel cells.

  17. Analysis of transport phenomena and electrochemical reactions in a micro PEM fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Sadiq Al-Baghdadi, Maher A.R. [Fuel Cell Research Center, International Energy and Environment Foundation, Najaf, P.O.Box 39 (Iraq)

    2013-07-01

    Micro-fuel cells are considered as promising electrochemical power sources in portable electronic devices. The presence of microelectromechanical system (MEMS) technology makes it possible to manufacture the miniaturized fuel cell systems. The majority of research on micro-scale fuel cells is aimed at micro-power applications. Performance of micro-fuel cells are closely related to many factors, such as designs and operating conditions. CFD modeling and simulation for heat and mass transport in micro PEM fuel cells are being used extensively in researches and industrial applications to gain better understanding of the fundamental processes and to optimize the micro fuel cell designs before building a prototype for engineering application. In this research, full three-dimensional, non-isothermal computational fluid dynamics model of a micro proton exchange membrane (PEM) fuel cell has been developed. This comprehensive model accounts for the major transport phenomena such as convective and diffusive heat and mass transfer, electrode kinetics, transport and phase-change mechanism of water, and potential fields in a micro PEM fuel cell. The model explains many interacting, complex electrochemical, and transport phenomena that cannot be studied experimentally. Three-dimensional results of the species profiles, temperature distribution, potential distribution, and local current density distribution are presented and analysed, with the focus on the physical insight and fundamental understanding.

  18. Innovative gas diffusion layers and their water removal characteristics in PEM fuel cell cathode

    Energy Technology Data Exchange (ETDEWEB)

    Jiao, Kui; Zhou, Biao [Department of Mechanical, Automotive and Materials Engineering, University of Windsor, Ont. (Canada)

    2007-06-20

    Liquid water transport is one of the key challenges regarding the water management in a proton exchange membrane (PEM) fuel cell. Conventional gas diffusion layers (GDLs) do not allow a well-organized liquid water flow from catalyst layer to gas flow channels. In this paper, three innovative GDLs with different micro-flow channels were proposed to solve liquid water flooding problems that conventional GDLs have. This paper also presents numerical investigations of air-water flow across the proposed innovative GDLs together with a serpentine gas flow channel on PEM fuel cell cathode by use of a commercial computational fluid dynamics (CFD) software package FLUENT. The results showed that different designs of GDLs will affect the liquid water flow patterns significantly, thus influencing the performance of PEM fuel cells. The detailed flow patterns of liquid water were shown. Several gas flow problems for the proposed different kinds of innovative GDLs were observed, and some useful suggestions were given through investigating the flow patterns inside the proposed GDLs. (author)

  19. Steam and partial oxidation reforming options for hydrogen production from fossil fuels for PEM fuel cells

    Directory of Open Access Journals (Sweden)

    Yousri M.A. Welaya

    2012-06-01

    Full Text Available Proton exchange membrane fuel cell (PEM generates electrical power from air and from hydrogen or hydrogen rich gas mixtures. Therefore, there is an increasing interest in converting current hydrocarbon based marine fuels such as natural gas, gasoline, and diesel into hydrogen rich gases acceptable to the PEM fuel cells on board ships. Using chemical flow sheeting software, the total system efficiency has been calculated. Natural gas appears to be the best fuel for hydrogen rich gas production due to its favorable composition of lower molecular weight compounds. This paper presents a study for a 250 kW net electrical power PEM fuel cell system utilizing a partial oxidation in one case study and steam reformers in the second. This study has shown that steam-reforming process is the most competitive fuel processing option in terms of fuel processing efficiency. Partial oxidation process has proved to posses the lowest fuel processing efficiency. Among the options studied, the highest fuel processing efficiency is achieved with natural gas steam reforming system.

  20. Design and experimental characterization of a 350 W High Temperature PEM fuel cell stack

    Directory of Open Access Journals (Sweden)

    Nicola Zuliani

    2011-01-01

    Full Text Available High Temperature Proton Exchange Membrane (HT PEM fuel cell based on polybenzimidazole (PBI polymer and phosphoric acid, can be operated at temperature between 120 °C and 180 °C. Reactants humidification is not required and CO content up to 2% in the fuel can be tolerated, affecting only marginally performance. This is what makes HT PEM very attractive, as low quality reformed hydrogen can be used and water management problems are avoided. Till nowadays, from experimental point of view, only few studies relate to the development and characterization of high temperature stacks. The aim of this work is to present the main design features and the performance curves of a 25 cells HT PEM stack based on PBI and phosphoric acid membranes. Performance curves refer to the stack operating with two type of fuels: pure hydrogen and a gas mixture simulating a typical steam reformer output. The stack voltage distribution analysis and the stack temperature distribution analysis suggest that cathode air could be used as coolant leading to a better thermal management. This could simplify stack design and system BOP, thus increasing system performance.

  1. On-board removal of CO and other impurities in hydrogen for PEM fuel cell applications

    Science.gov (United States)

    Huang, Cunping; Jiang, Ruichun; Elbaccouch, Mohamed; Muradov, Nazim; Fenton, James M.

    Carbon monoxide (CO) in the hydrogen (H 2) stream can cause severe performance degradation for an H 2 polymer electrolyte membrane (PEM) fuel cell. The on-board removal of CO from an H 2 stream requires a process temperature less than 80 °C, and a fast reaction rate in order to minimize the reactor volume. At the present time, few technologies have been developed that meet these two requirements. This paper describes a concept of electrochemical water gas shift (EWGS) process to remove low concentration CO under ambient conditions for on-board applications. No on-board oxygen or air supply is needed for CO oxidation. Experimental work has been carried out to prove the concept of EWGS and the results indicate that the process can completely remove low level CO and improve the performance of a PEM fuel cell to the level of a pure H 2 stream. Because the EWGS electrolyzer can be modified from a humidifier for a PEM fuel cell system, no additional device is needed for the CO removal. More experimental data are needed to determine the rate of CO electrochemical removal and to explore the mechanism of the proposed process.

  2. Final Scientific Report, New Proton Conductive Composite Materials for PEM Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Lvov, Serguei

    2010-11-08

    This project covered one of the main challenges in present-day PEM fuel cell technology: to design a membrane capable of maintaining high conductivity and mechanical integrity when temperature is elevated and water vapor pressure is severely reduced. The DOE conductivity milestone of 0.1 S cm-1 at 120 degrees C and 50 % relative humidity (RH) for designed membranes addressed the target for the project. Our approach presumed to develop a composite membrane with hydrophilic proton-conductive inorganic material and the proton conductive polymeric matrix that is able to “bridge” the conduction paths in the membrane. The unique aspect of our approach was the use of highly functionalized inorganic additives to benefit from their water retention properties and high conductivity as well. A promising result turns out that highly hydrophilic phosphorsilicate gels added in Nafion matrix improved PEM fuel cell performance by over 50% compared with bare Nafion membrane at 120 degrees C and 50 % RH. This achievement realizes that the fuel cell operating pressure can be kept low, which would make the PEM fuel cell much more cost efficient and adaptable to practical operating conditions and facilitate its faster commercialization particularly in automotive and stationary applications.

  3. A parametric study of assembly pressure, thermal expansion, and membrane swelling in PEM fuel cells

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2016-01-01

    Full Text Available Proton Exchange membrane (PEM fuel cells are still undergoing intense development, and the combination of new and optimized materials, improved product development, novel architectures, more efficient transport processes, and design optimization and integration are expected to lead to major gains in performance, efficiency, durability, reliability, manufacturability and cost-effectiveness. PEM fuel cell assembly pressure is known to cause large strains in the cell components. All components compression occurs during the assembly process of the cell, but also during fuel cell operation due to membrane swelling when absorbs water and cell materials expansion due to heat generating in catalyst layers. Additionally, the repetitive channel-rib pattern of the bipolar plates results in a highly inhomogeneous compressive load, so that while large strains are produced under the rib, the region under the channels remains approximately at its initial uncompressed state. This leads to significant spatial variations in GDL thickness and porosity distributions, as well as in electrical and thermal bulk conductivities and contact resistances (both at the ribe-GDL and membrane-GDL interfaces. These changes affect the rates of mass, charge, and heat transport through the GDL, thus impacting fuel cell performance and lifetime. In this paper, computational fluid dynamics (CFD model of a PEM fuel cell has been developed to simulate the pressure distribution inside the cell, which are occurring during fuel cell assembly (bolt assembling, and membrane swelling and cell materials expansion during fuel cell running due to the changes of temperature and relative humidity. The PEM fuel cell model simulated includes the following components; two bi-polar plates, two GDLs, and, an MEA (membrane plus two CLs. This model is used to study and analyses the effect of assembling and operating parameters on the mechanical behaviour of PEM. The analysis helped identifying critical

  4. Reversible Computing

    Science.gov (United States)

    1980-02-01

    will have been introduced. 9. Reversible celular autemata We shall assume the reader to have some familiarity with the concept of cel- lular...10003 Mr. Kin B. Thcmpson 1 copy Technical Director Information Systems Divisia.i Naval Research Laboratory (OP-91T) Technical Information Division

  5. Reversible energy storage on a fuel cell-supercapacitor hybrid device

    Energy Technology Data Exchange (ETDEWEB)

    Zerpa Unda, Jesus Enrique

    2011-02-18

    A new concept of energy storage based on hydrogen which operates reversibly near ambient conditions and without important energy losses is investigated. This concept involves the hybridization between a proton exchange membrane fuel cell and a supercapacitor. The main idea consists in the electrochemical splitting of hydrogen at a PEM fuel cell-type electrode into protons and electrons and then in the storage of these two species separately in the electrical double layer of a supercapacitor-type electrode which is made of electrically conductive large-surface area carbon materials. The investigation of this concept was performed first using a two-electrode fuel cell-supercapacitor hybrid device. A three-electrode hybrid cell was used to explore the application of this concept as a hydrogen buffer integrated inside a PEM fuel cell to be used in case of peak power demand. (orig.)

  6. Effect of growth mechanisms on the deformation of a unit cell and polarization reversal in barium-strontium titanate heterostructures on magnesium oxide

    Science.gov (United States)

    Mukhortov, V. M.; Golovko, Yu. I.; Biryukov, S. V.; Anokhin, A.; Yuzyuk, Yu. I.

    2016-01-01

    The effect of a growth mechanism on the unit cell strain and the related change in the properties of single-crystal Ba0.8Sr0.2TiO3 films grown on MgO substrates according to the Frank-van der Merwe and Volmer-Weber growth mechanisms is studied. The unit cell strain is shown to depend substantially on the film thickness and the growth mechanism. It is found that the same film-substrate pair can be used to vary stresses in the film from two-dimensional tensile to compressive stresses due to a change in the growth mechanism and the film thickness.

  7. Experimental comparison of standard fuel cells PEM in radial configuration, coil and spiral; Comparacion experimental de celdas de combustible tipo PEM en configuracion radial, serpentin y espiral

    Energy Technology Data Exchange (ETDEWEB)

    Cano Andrade, Sergio

    2008-12-15

    After analyzing each one of the possible energy sources to replace oil the following question arises: which of all the possible sources is the suitable one? With no doubt another important factor in the election of this source is due to take into account, which has to do with the great problem that the humanity deals on a daily basis: the greenhouse effect. Taking into account the greenhouse effect, the fuel cells on the basis of hydrogen are the more viable energy source to substitute oil, since in their operation they are friendly with the environment since they do not produce polluting agents, reducing enormously the problem of global heating in which the planet is bottled. It is very certain that many disadvantages in these fuel cells on the basis of hydrogen still exist, but the arduous investigations realized until the present time foresee an excellent future where the planet will be able to satisfy its daily energy demand on the basis of the hydrogen technology. In future works one must have special care of the humidity control of gases before entering the fuel cell, since it is an important parameter in the correct operation of the standard fuel cells PEM. In the present investigation the advance in the state-of-the-art of the hydrogen technology is illustrated, specifically with the generation of electricity on the basis of the novel configurations of standard fuel cells PEM. Until the moment similar work it has not been found in the bibliography similar work where it is experienced with this type of radial configuration for the hydrogen technologies. The geometry and the results presented/displayed in this analysis correspond to a work of the highest category in the state-of-the-art of the fuel cells; in addition, an ample expectation due to the highly satisfactory results found, either numerically as well as experimentally, in comparison with other geometries is obtained. [Spanish] Despues de analizar cada una de las posibles fuentes de energia para

  8. Development and Study of Tantalum and Niobium Carbides as Electrocatalyst Supports for the Oxygen Electrode for PEM Water Electrolysis at Elevated Temperatures

    DEFF Research Database (Denmark)

    Nikiforov, Aleksey; Petrushina, Irina; Prag, Carsten Brorson;

    2013-01-01

    Polymer electrolyte membrane (PEM) water electrolysis is a prospective method of producing hydrogen. We focused on one of its issues – the lack of a suitable support material for the anode electrocatalyst. TaC and NbC were studied as possible electrocatalyst supports for the PEM water electrolysi...

  9. Teledyne Energy Systems, Inc., Proton Exchange Member (PEM) Fuel Cell Engineering Model Powerplant. Test Report: Initial Benchmark Tests in the Original Orientation

    Science.gov (United States)

    Loyselle, Patricia; Prokopius, Kevin

    2011-01-01

    Proton Exchange Membrane (PEM) fuel cell technology is the leading candidate to replace the alkaline fuel cell technology, currently used on the Shuttle, for future space missions. During a 5-yr development program, a PEM fuel cell powerplant was developed. This report details the initial performance evaluation test results of the powerplant.

  10. Polymers and composites synthesis and characterization for application on PEM type fuel cells; Sintese e caracterizacao de polimeros e compositos para aplicacao em celulas a combustivel do tipo PEM

    Energy Technology Data Exchange (ETDEWEB)

    Fiuza, Raigenis da Paz; Souza, Daniele Ribeiro; Barreto, Ednardo Gomes; Boaventura Filho, Jaime Soares; Jose, Nadia Mamede [Universidade Federal da Bahia (UFBA), Salvador, BA (Brazil)]. E-mail: raigenis@gmail.com

    2006-07-01

    The PEM (proton exchanging membrane) type fuel cell presents good potential for the energy production without the residue generation. However, its manufacture presents high costs for commercial application, mainly due to the electrolyte. Sulfonated Peek (polish-ether-ether-ketone) supported or auto immobilized the in a silicone matrix is an interesting alternative as electrolyte for PEM fuel cells. The commercial PEEK in powder form was functionalized with sulfuric acid, giving the SPEEK (Sulfonated PEEK). The membranes were produced by hot pressing the SPEEK immobilized in a silicone matrix produced by the sol-gel process. The membranes obtained were characterized by DRX, FTIR, TGA, MEV, DSC and protonic conductivity measurements. (author)

  11. Modelling of a High Temperature PEM Fuel Cell Stack using Electrochemical Impedance Spectroscopy

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Jespersen, Jesper Lebæk; Kær, Søren Knudsen

    2008-01-01

    This work presents the development of an equivalent circuit model of a 65 cell high temperature PEM (HTPEM) fuel cell stack using Electrochemical Impedance Spectroscopy (EIS). The HTPEM fuel cell membranes used are PBI-based and uses phosphoric acid as proton conductor. The operating temperature...... of the MEA's is 160-180oC, depending on the purity of the hydrogen used, the load pattern and the desired lifetime. The advantages of the HTPEM fuel cell technology include fast response to load changes and high tolerance to CO (1-3%)...

  12. Clear-PEM: A PET imaging system dedicated to breast cancer diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Abreu, M.C. [LIP, Lab. de Instrumentacao e Fisica Exp. Particulas (Portugal); Aguiar, D. [INESC-ID and INOV, Lisbon (Portugal); Albuquerque, E. [INEGI Inst. Eng. Mecanica Gestao Industrial, Porto (Portugal)] (and others)

    2007-02-01

    The Clear-PEM scanner for positron emission mammography under development is described. The detector is based on pixelized LYSO crystals optically coupled to avalanche photodiodes and readout by a fast low-noise electronic system. A dedicated digital trigger (TGR) and data acquisition (DAQ) system is used for on-line selection of coincidence events with high efficiency, large bandwidth and small dead-time. A specialized gantry allows to perform exams of the breast and of the axilla. In this paper we present results of the measurement of detector modules that integrate the system under construction as well as the imaging performance estimated from Monte Carlo simulated data.

  13. Fisicoquímica de materiales para celdas de combustible PEM alimentadas con metanol

    OpenAIRE

    Franceschini, Esteban Andrés

    2012-01-01

    Las celdas de combustible de membrana de intercambio protónico (PEM) alimentadas con metanol directo (DMPEM) utilizan en la actualidad como catalizadores catódico y anódico, platino y aleaciones platino/rutenio, respectivamente. Los catalizadores comerciales utilizados, están compuestos por nanopartículas de estos metales soportadas sobre partículas de carbón Vulcan XC72®. Estos catalizadores soportados presentan un bajo aprovechamiento del platino debido a que, para obtener una alta área ele...

  14. Polarization Curve of a Non-Uniformly Aged PEM Fuel Cell

    Directory of Open Access Journals (Sweden)

    Andrei Kulikovsky

    2014-01-01

    Full Text Available We develop a semi-analytical model for polarization curve of a polymer electrolyte membrane (PEM fuel cell with distributed (aged along the oxygen channel MEA transport and kinetic parameters of the membrane–electrode assembly (MEA. We show that the curve corresponding to varying along the channel parameter, in general, does not reduce to the curve for a certain constant value of this parameter. A possibility to determine the shape of the deteriorated MEA parameter along the oxygen channel by fitting the model equation to the cell polarization data is demonstrated.

  15. Structural and Morphological Features of Acid-Bearing Polymers for PEM Fuel Cells

    DEFF Research Database (Denmark)

    Yang, Yunsong; Siu, Ana; Peckham, Timothy J.

    2008-01-01

    conductivity and water transport are described. The formation, dimensions, and connectivity of ionic pathways are consistently found to play an important role in determining the physicochemical properties of PEMs. For polymers that possess low water content, phase separation and ionic channel formation...... significantly enhance the transport of water and protons. For membranes that contain a high content of water, phase separation is less influential. Continuity of ionic aggregates is influential on the diffusion of water and electroosmotic drag within a membrane. A balance of these properties must be considered...

  16. Modeling and Design of Hybrid PEM Fuel Cell Systems for Lift Trucks

    DEFF Research Database (Denmark)

    Hosseinzadeh, Elham

    . The most common type of fuel cell used for automotive applications is the PEM fuel cell. They are known for their high efficiency, low emissions and high reliability. However, the biggest obstacles to introducing fuel cell vehicles are the lack of a hydrogen infrastructure, cost and durability of the stack....... This model can be used as a guideline for optimal PEMFC operation with respect to electrical efficiency and net power production. In addition to the optimal operation, investigation of different coolants and operating conditions provides some recommendations for water and thermal management of the system...

  17. Silicon carbide-silicon as a support material for oxygen evolution reaction in PEM steam electrolysers

    DEFF Research Database (Denmark)

    Nikiforov, Aleksey; Petrushina, Irina; Christensen, Erik;

    , cyclic voltammetry, SEM, EDX and steady state electrochemical polarisation in a working PEM steam electrolyser. Several SiC-Si-IrO2 electrodes have been prepared and tested. The iridium oxide content at the electrode active layer varied from x=0.2 to x=1, corresponding to the general formula (1-x...... technique and the average particle diameter of silicon carbide-silicon was found to be in the range of 5-10 µm, while its specific surface area was about 5 sq.m/g. The oxygen evolution reaction was studied by the cyclic voltammetry technique in 85% phosphoric acid solution at temperatures between 22 and 150...

  18. New electrocatalyst support for high temperature PEM fuel cells (HT-PEMFC)

    Energy Technology Data Exchange (ETDEWEB)

    Boaventura, M.; Brandao, L.; Mendes, A. [Porto Univ. (PT). Lab. de Engenharia de Processos, Ambiente e Energia (LEPAE)

    2010-07-01

    This work compares the performance of electrocatalysts based on platinum supported in single-wall carbon nanohorns (Pt-SWNH) and supported in carbon black (Pt-carbon black) during high temperature PEM fuel operation. MEAs made of phosphoric acid doped polybenzimidazole (PBI/H{sub 3}PO{sub 4}) were characterized by polarization curves, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), at 160 C. The Pt-SWNH electrocatalyst presented a higher electrochemical surface area (ESA) when compared to Pt-carbon black. However, electrochemical experiments showed a higher ohmic resistance of the Pt-SWNH electrode related to a higher hydrophobic character of the SWNH carbon. (orig.)

  19. Technology data for high temperature solid oxide electrolyser cells, alkali and PEM electrolysers

    DEFF Research Database (Denmark)

    Mathiesen, Brian vad; Ridjan, Iva; Connolly, David;

    The transition to 100% renewable energy systems will require a more integrated energy system. Connecting the electricity sector to transport is one of the major challenges in this transition, especially for long-distance and heavy-duty transport. Hydrogen is one potential solution to this challen...... electrolyte membrane (PEM), and solid oxide (SOEC) electrolysers between 2012 and 2050. These inputs can be usedfor analysing energy systems that include electrolysers....... and forecasted development of electrolysers. The aim in this report is to reduce this uncertainty by gathering and aligning current knowledge in relation to the technical and economic potential of electrolysers. The results highlight existing and forecasted costs and efficiencies for alkaline, polymer...

  20. Clear-PEM: A PET imaging system dedicated to breast cancer diagnostics

    CERN Document Server

    Abreu, M C; Albuquerque, E; Almeida, F G; Almeida, P; Amaral, P; Auffray, Etiennette; Bento, P; Bruyndonckx, P; Bugalho, R; Carriço, B; Cordeiro, H; Ferreira, M; Ferreira, N C; Gonçalves, F; Lecoq, Paul; Leong, C; Lopes, F; Lousã, P; Luyten, J; Martins, M V; Matela, N; Rato-Mendes, P; Moura, R; Nobre, J; Oliveira, N; Ortigão, C; Peralta, L; Rego, J; Ribeiro, R; Rodrigues, P; Santos, A I; Silva, J C; Silva, M M; Tavernier, Stefaan; Teixeira, I C; Texeira, J P; Trindade, A; Trummer, Julia; Varela, J

    2007-01-01

    The Clear-PEM scanner for positron emission mammography under development is described. The detector is based on pixelized LYSO crystals optically coupled to avalanche photodiodes and readout by a fast low-noise electronic system. A dedicated digital trigger (TGR) and data acquisition (DAQ) system is used for on-line selection of coincidence events with high efficiency, large bandwidth and small dead-time. A specialized gantry allows to perform exams of the breast and of the axilla. In this paper we present results of the measurement of detector modules that integrate the system under construction as well as the imaging performance estimated from Monte Carlo simulated data.

  1. The effect of inhomogeneous compression on water transport in the cathode of a PEM fuel cell

    DEFF Research Database (Denmark)

    Olesen, Anders Christian; Berning, Torsten; Kær, Søren Knudsen

    2011-01-01

    A three-dimensional, multi-component, two-fluid model developed in the commercial CFD package CFX 13 (ANSYS inc.), is used to investigate the effect of porous media compression on transport phenomenon of a PEM Fuel cell (PEMFC). The PEMFC model only consist of the cathode channel, gas diffusion...... layer, micro-porous layer and catalyst layer, excluding the membrane and anode. In the porous media liquid water transport is described by the capillary pressure gradient, momentum loss via the Darcy-Forchheimer equation and mass transfer between phases by a non-equilibrium phase change model...

  2. Advances in the development of a hydrogen/oxygen PEM fuel cell stack

    Energy Technology Data Exchange (ETDEWEB)

    Tori, C.; Garaventta, G.; Visintin, A.; Triaca, W.E. [Instituto de Investigaciones Fisicoquimicas Teoricas y Aplicadas (INIFTA), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CC 16, Suc. 4 (1900) La Plata (Argentina); Baleztena, M.; Peralta, C.; Calzada, R.; Jorge, E. [Grupo de Investigacion en Energias Sustentables y Eficiencia Energetica (GIESEE), Departamento de Electrotecnia, Universidad Tecnologica Nacional, Facultad Regional La Plata, Av. 60 esq. 124 (1900) La Plata (Argentina); Barsellini, D. [Instituto de Investigaciones Fisicoquimicas Teoricas y Aplicadas (INIFTA), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CC 16, Suc. 4 (1900) La Plata (Argentina); Grupo de Investigacion en Energias Sustentables y Eficiencia Energetica (GIESEE), Departamento de Electrotecnia, Universidad Tecnologica Nacional, Facultad Regional La Plata, Av. 60 esq. 124 (1900) La Plata (Argentina)

    2008-07-15

    Recent advances in the design and construction of a hydrogen/oxygen PEM fuel cell stack are presented. A test bench including measurement and control devices to monitor the fuel cell operating parameters was mounted. The influence of the characteristics of the membrane electrode assembly, bipolar plates, etc., on the performance of the fuel cell stack was studied. The behavior of the fuel cell stack with a different number of cells in series was evaluated. In order to identify and minimize the energy losses a critical analysis of the results was done. (author)

  3. Low cost, high temperature membranes for PEM fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2007-08-15

    This report details the results of a project to develop novel, low-cost high temperature membranes specifically for automotive fuel cell use. The specific aim of the project was to determine whether a polyaromatic hydrocarbon membrane could be developed that would give a performance (0.68V at 500 mAcm{sub -2}) competitive with an established perfluoronated sulfonic acid (PSA) membrane in a fuel cell at 120{sup o}C and relative humidity of less than 50%. The novel approach used in this project was to increase the concentration of sulphonic groups to a useful level without dissolution by controlling the molecular structure of the membrane through the design of the monomer repeat unit. The physicochemical properties of 70 polymers synthesised in order to determine the effects of controlled sequence distribution were identified using an array of analytical techniques. Appropriate membranes were selected for fuel cell testing and fabricated into membrane electrode assemblies. Most of the homopolymers tested were able to withstand low humidity environments without immediate catastrophic failure and some showed promise from accelerated durability results. The properties of a simple starting polymer structure were found to be enhanced by doping with sulphonated copper phthalocyanine, resulting in high temperature capacity from a potential cheap, simple and scaleable process. The accelerated and long-term durability of such a doped polymer membrane showed that polyaromatics could easily outperform fluoropolymers under high temperature (120{sup o}C) operating conditions.

  4. Correlation of PUV and SUV in the extremities while using PEM as a high-resolution positron emission scanner

    Energy Technology Data Exchange (ETDEWEB)

    Rahim, Sania [The University of Texas MD Anderson Cancer Center, Division of Diagnostic Imaging, Houston, TX (United States); MD Anderson Cancer Center, Houston, TX (United States); Mawlawi, Osama; Taylor, Shree; Millican, Richelle; Swanston, Nancy M.; Rohren, Eric M. [The University of Texas MD Anderson Cancer Center, Division of Diagnostic Imaging, Houston, TX (United States); Fox, Patricia [The University of Texas MD Anderson Cancer Center, Division of Biostatistics, Houston, TX (United States); Brown, J.E. [Yale University Hospital, Department of Radiology, New Haven, CT (United States)

    2014-04-15

    Owing to its unique configuration of two adjustable plate detectors positron emission mammography, or PEM, could theoretically also function as a high-resolution positron emission scanner for the extremities or neck. PEM quantitates its activity via a ''PEM uptake value,'' or PUV, and although its relationship to the standardized uptake value, or SUV, has been demonstrated in the breasts, to our knowledge there are no studies validating PUV in other sites such as the extremities. This was a retrospective chart review of two separate protocols of a total of 15 patients. The patients all had hypermetabolic lesions in the extremities or neck on imaging with PET/CT and were sent after their PET/CT to PEM for further imaging. Owing to the sequential nature of these examinations no additional radiotracer was administered. Spearman's rank order correlation was calculated between the PUVmax obtained from PEM images, and the SUVmax for all. Spearman's rank order correlation for all sites was 0.42, which is not significantly different from 0 (p = 0.13). When neck lesions were excluded from the group, there was a strong and statistically significant correlation between PUVmax and SUVmax, with Spearman's rank correlation of 0.73, and significantly different from 0 (p = 0.0068). The correlation of PUV and SUV in the extremities indicates the potential use of PEM as a semiquantitative, high-resolution positron emission scanner and warrants further investigation, especially in the realms of disease processes that often present in the extremities, such as melanoma, osteomyelitis, and arthritis, as well as playing a role in the imaging of patients with metallic hardware post-limb salvage surgery. (orig.)

  5. Highly fluorinated comb-shaped copolymers as proton exchange membranes (PEMs): improving PEM properties through rational design

    Energy Technology Data Exchange (ETDEWEB)

    Norsten, T.B.; Guiver, M.D.; Murphy, J.; Ding, J. [Institute for Chemical Process and Environmental Technology, National Research Council of Canada, 1200 Montreal Road, Ottawa, ON K1A 0R6 (Canada); Astill, T.; Holdcroft, S. [Institute for Fuel Cell Innovation, National Research Council, 3250 East Mall, Vancouver, BC V6T 1W5 (Canada); Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6 (Canada); Navessin, T. [Institute for Fuel Cell Innovation, National Research Council, 3250 East Mall, Vancouver, BC V6T 1W5 (Canada); Frankamp, B.L.; Rotello, V.M. [Department of Chemistry, University of Massachusetts, Amherst, MA 01003 (United States)

    2006-09-18

    A new class of comb-shaped polymers for use as a proton conducting membrane is presented. The polymer is designed to combine the beneficial physical, chemical, and structural attributes of fluorinated Nafion-like materials with higher-temperature, polyaromatic-based polymer backbones. The comb-shaped polymer unites a rigid, polyaromatic, hydrophobic backbone with lengthy hydrophilic polymer side chains; this combination affords direct control over the polymer nanostructure within the membrane and results in distinct microphase separation between the opposing domains. The microphase separation serves to compartmentalize water into the hydrophilic polymer side chain domains, resulting in effective membrane water management and excellent proton conductivities. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  6. Experimental Study and Comparison of Various Designs of Gas Flow Fields to PEM Fuel Cells and Cell Stack Performance

    OpenAIRE

    Liu, Hong; Li, Peiwen; Juarez-Robles, Daniel; Wang, Kai; Hernandez-Guerrero, Abel

    2014-01-01

    In this study, a significant number of experimental tests to proton exchange membrane (PEM) fuel cells were conducted to investigate the effect of gas flow fields on fuel cell performance. Graphite plates with various flow field or flow channel designs, from literature survey and also novel designs by the authors, were used for the PEM fuel cell assembly. The fabricated fuel cells have an effective membrane area of 23.5 cm2. The results showed that the serpentine flow channel design is still ...

  7. Experimental study and comparison of various designs of gas flow fields to PEM fuel cells and cell stack performance

    OpenAIRE

    Hong eLiu; Peiwen eLi; Daniel eJuarez-Robles; Kai eWang; Abel eHernandez-Guerrero

    2014-01-01

    In this study, a significant number of experimental tests to PEM fuel cells were conducted to investigate the effect of gas flow fields on fuel cell performance. Graphite plates with various flow field or flow channel designs, from literature survey and also novel designs by the authors, were used for the PEM fuel cell assembly. The fabricated fuel cells all have an effective membrane area of 23.5 cm2. The results showed that the serpentine flow channel design is still favorable, giving the b...

  8. Vital signs: trends in use of long-acting reversible contraception among teens aged 15-19 years seeking contraceptive services—United States, 2005-2013.

    Science.gov (United States)

    Romero, Lisa; Pazol, Karen; Warner, Lee; Gavin, Lorrie; Moskosky, Susan; Besera, Ghenet; Loyola Briceno, Ana Carolina; Jatlaoui, Tara; Barfield, Wanda

    2015-04-10

    Nationally, the use of long-acting reversible contraception (LARC), specifically intrauterine devices (IUDs) and implants, by teens remains low, despite their effectiveness, safety, and ease of use. To examine patterns in use of LARC among females aged 15-19 years seeking contraceptive services, CDC and the U.S. Department of Health and Human Services' Office of Population Affairs analyzed 2005-2013 data from the Title X National Family Planning Program. Title X serves approximately 1 million teens each year and provides family planning and related preventive health services for low-income persons. Use of LARC among teens seeking contraceptive services at Title X service sites increased from 0.4% in 2005 to 7.1% in 2013 (p-value for trend contraceptive services in 2013, 17,349 (2.8%) used IUDs, and 26,347 (4.3%) used implants. Use of LARC was higher among teens aged 18-19 years (7.6%) versus 15-17 years (6.5%) (pcontraception at Title X service sites have increased use of these methods. Health centers that provide quality contraceptive services can facilitate use of LARC among teens seeking contraception. Strategies to address provider barriers to offering LARC include: 1) educating providers that LARC is safe for teens; 2) training providers on LARC insertion and a client-centered counseling approach that includes discussing the most effective contraceptive methods first; and 3) providing contraception at reduced or no cost to the client.

  9. Performance of the PdNi and PdNiSe as cathodes in PEM fuel cells; Desempeno de PdNi y PdNiSe como catodos en celdas de combustible tipo PEM

    Energy Technology Data Exchange (ETDEWEB)

    Santana, A.; Ramos-Sanchez, G.; Vazquez, G.; Solorza-Feria, O. [Centro de Investigaciones y de Estudios Avanzados del IPN, Mexico D.F. (Mexico)]. E-mail: gramos@cinvestav.mx

    2009-09-15

    The search for new materials capable of catalyzing oxygen reactions in low temperature fuel cells continues to be one of the key issues in the development of a hydrogen economy. Electrochemical and physical characterization studies have demonstrated that the PdNi and PdNiSe catalysts have adequate properties for use as cathodes in fuel cells. Nevertheless, the performance of the materials in proton exchange membrane (PEM) fuel cells depends not only on the catalytic properties but also on the adequate preparation of the electrocatalyst membrane interface (EMI). This work presents the results of the search for optimal conditions to prepare the EMIs with PdNi and PdNiSe cathodes. There are many variables for handling the preparation of the interfaces, nevertheless our search focuses on two: catalyst ratio/Vulcan Carbon® and the catalyst amount. Interfaces were prepared with an active area of 5 cm{sup 2} with PdNi and PdNiSe cathodes and carbon fabric anode with Pt E-tek®. These interfaces were tested with an ElectroChem model under different gas pressure and temperature conditions. The optimization method was carried out using a simplex method with the variables mentioned above and power density per unit mass and catalyst area as response variables. [Spanish] La busqueda de nuevos materiales capaces de catalizar la Reaccion de Oxigeno (RRO) en celdas de combustible de baja temperatura, sigue siendo uno de los temas clave para el desarrollo de una Economia del Hidrogeno. Estudios electroquimicos y de caracterizacion fisica han demostrado que los catalizadores PdNi y PdNiSe, tienen las propiedades adecuadas para poder ser utilizados como catodos en celdas de combustible; sin embargo el desempeno de los materiales en celdas de combustible de membrana de intercambio protonico (PEM), no solo depende de las propiedades del catalizador, sino tambien de la preparacion adecuada del Ensamble Membrana Electrocatalizador (EME). En este trabajo se presentan los resultados de la

  10. Reversible Statistics

    DEFF Research Database (Denmark)

    Tryggestad, Kjell

    2004-01-01

    The study aims is to describe how the inclusion and exclusion of materials and calculative devices construct the boundaries and distinctions between statistical facts and artifacts in economics. My methodological approach is inspired by John Graunt's (1667) Political arithmetic and more recent work...... within constructivism and the field of Science and Technology Studies (STS). The result of this approach is here termed reversible statistics, reconstructing the findings of a statistical study within economics in three different ways. It is argued that all three accounts are quite normal, albeit...... in different ways. The presence and absence of diverse materials, both natural and political, is what distinguishes them from each other. Arguments are presented for a more symmetric relation between the scientific statistical text and the reader. I will argue that a more symmetric relation can be achieved...

  11. Safety of 50,000-100,000 units of vitamin D3/week in vitamin D-deficient, hypercholesterolemic patients with reversible statin intolerance

    Directory of Open Access Journals (Sweden)

    Vybhav Jetty

    2016-01-01

    Full Text Available Background: Vitamin D deficiency (100 ng/mL but not toxic (>150 ng/mL in 4 patients (1.4%. Median serum calcium was unchanged from entry (9.60 mg/dL to 9.60 at 6 months (P = .36, with no trend of change (P = .16. Median eGFR was unchanged from entry (84 mL/min/1.73 to 83 at 6 months (P = .57, with no trend of change (P = .59. On vitamin D3 71,700 (mean and 50,000 IU/week (median at 12 months in 112 patients, serum vitamin D rose from pretreatment (21-median to 51 ng/mL (P 100 but 0.3. eGFR did not change from 79 mL/min/1.73 at entry to 74 mL/min/1.73 and 77 mL/min/1.73 at 6 months and 12 months, P > 0.3. There was no trend in the change in serum calcium (P > 0.5 for 6 months and 12 months, and no change of eGFR for 6 months and 12 months, P > 0.15. Conclusions: Vitamin D3 therapy (50,000-100,000 IU/week was safe and effective when given for 12 months to reverse statin intolerance in patients with vitamin D deficiency. Serum vitamin D rarely exceeded 100 ng/mL, never reached toxic levels, and there were no significant change in serum calcium or eGFR.

  12. A new state-observer of the inner PEM fuel cell pressures for enhanced system monitoring

    Science.gov (United States)

    Bethoux, Olivier; Godoy, Emmanuel; Roche, Ivan; Naccari, Bruno; Amira Taleb, Miassa; Koteiche, Mohamad; Nassif, Younane

    2014-06-01

    In embedded systems such as electric vehicles, Proton exchange membrane fuel cell (PEMFC) has been an attractive technology for many years especially in automotive applications. This paper deals with PEMFC operation monitoring which is a current target for improvement for attaining extended durability. In this paper, supervision of the PEMFC is done using knowledge-based models. Without extra sensors, it enables a clear insight of state variables of the gases in the membrane electrode assembly (MEA) which gives the PEMFC controller the ability to prevent abnormal operating conditions and associated irreversible degradations. First, a new state-observer oriented model of the PEM fuel cell is detailed. Based on this model, theoretical and practical observability issues are discussed. This analysis shows that convection phenomena can be considered negligible from the dynamic point of view; this leads to a reduced model. Finally a state-observer enables the estimation of the inner partial pressure of the cathode by using only the current and voltage measurements. This proposed model-based approach has been successfully tested on a PEM fuel cell simulator using a set of possible fault scenarios.

  13. Numerical Investigation of Channel Geometry on the Performance of a Pem Fuel Cell

    Science.gov (United States)

    Khazaee, I.; Mohammadiun, M.

    2013-03-01

    A complete three-dimensional and single phase model for proton exchange membrane (PEM) fuel cells was used to investigate the effect of using different channels geometry on the performances, current density and gas concentration. The proposed model was a full cell model, which includes all the parts of the PEM fuel cell, flow channels, gas diffusion electrodes, catalyst layers and the membrane. Coupled transport and electrochemical kinetics equations were solved in a single domain; therefore no interfacial boundary condition was required at the internal boundaries between cell components. This computational fluid dynamics code was employed as the direct problem solver, which was used to simulate the three-dimensional mass, momentum, energy and species transport phenomena as well as the electron- and proton-transfer process taking place in a PEMFC. The results showed that the predicted polarization curves by using this model were in good agreement with the experimental results and a high performance was observed by using circle geometry for the channels of anode and cathode sides. Also, the results showed that the performance of the fuel cell improved when a rectangular channel was used.

  14. Numerical study of changing the geometry of the flow field of a PEM fuel cell

    Science.gov (United States)

    Khazaee, I.; Sabadbafan, H.

    2016-05-01

    The geometry of channels of a PEM fuel cell is an important parameter that affects the performance of it that the lower voltage loss in polarization curve can indicate the better performance. In this study a complete three-dimensional and single phase model is used to investigate the effect of increasing the number of serpentine channels in the bipolar plates and also increasing the area (depth) of channels of a PEM fuel cell with rectangular, triangular and elliptical cross-section geometry. A single set of conservation equations which are valid for the flow channels, gas-diffusion electrodes, catalyst layers, and the membrane region is developed and numerically solved using a finite volume based computational fluid dynamics technique. The results show that there are good agreement with the numerical results and experimental results of the previous work of authors. Also the results show that by increasing the number of channels from one to four and eight, the performance improved about 18 % and by decreasing the area of channels from 2 to 1 mm2 the performance improved about 13 %.

  15. Application of Butler-Volmer equations in the modelling of activation polarization for PEM fuel cells

    Science.gov (United States)

    Mann, R. F.; Amphlett, J. C.; Peppley, B. A.; Thurgood, C. P.

    Proton exchange membrane (PEM) fuel cells have been under development for many years and appear to be the potential solution for many electricity supply applications. Modelling and computer simulation of PEM fuel cells have been equally active areas of work as a means of developing better understanding of cell and stack operation, facilitating design improvements and supporting system simulation studies. In general, fuel cell models must be capable of predicting values of the activation polarization at both the anode and the cathode. Since the magnitude of an activation polarization for a particular electrode depends on the inverse of the chemical (or electrochemical) reaction rate at that electrode, reaction rate expressions are normally required for each electrode. The reaction rate is commonly expressed as an 'exchange current density', typical symbol i 0, and mechanistic expressions to predict i 0 are, therefore, components of an ideal model. Most expressions for i 0 are based on the Butler-Volmer (B-V) equation or on more approximate equations derived from the B-V equation. Many publications use one of these B-V equations without a critical determination of the applicability or accuracy of the particular equation being used. The present paper examines these questions and makes some recommendations regarding the applicability of each equation in the 'B-V family of equations'. In addition, terminology and symbols have been modified, where possible, to make modelling based on B-V equations more easily understood and applied by those without an extensive background in electrochemistry.

  16. Current density distribution mapping in PEM fuel cells as an instrument for operational measurements

    Energy Technology Data Exchange (ETDEWEB)

    Geske, M.; Heuer, M.; Heideck, G.; Styczynski, Z. A. [Otto-von-Guericke University Magdeburg, Chair Electric Power Networks and Renewable Energy Sources, Magdeburg (Germany)

    2010-07-01

    A newly developed measurement system for current density distribution mapping has enabled a new approach for operational measurements in proton exchange membrane fuel cells (PEMFC). Taking into account previously constructed measurement systems, a method based on a multi layer printed circuit board was chosen for the development of the new system. This type of system consists of a sensor, a special electronic device and the control and visualization PC. For the acquisition of the current density distribution values, a sensor device was designed and installed within a multilayer printed circuit board with integrated shunt resistors. Varying shunt values can be taken into consideration with a newly developed and evaluated calibration method. The sensor device was integrated in a PEM fuel cell stack to prove the functionality of the whole measurement system. A software application was implemented to visualize and save the measurement values. Its functionality was verified by operational measurements within a PEMFC system. Measurement accuracy and possible negative reactions of the sensor device during PEMFC operation are discussed in detail in this paper. The developed system enables operational measurements for different operating phases of PEM fuel cells. Additionally, this can be seen as a basis for new opportunities of optimization for fuel cell design and operation modes. (author)

  17. Electrochemical separation of hydrogen from reformate using PEM fuel cell technology

    Energy Technology Data Exchange (ETDEWEB)

    Gardner, C.L. [Department of Chemical Engineering and Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, Ontario K1N 6N5 (Canada); Ternan, M. [EnPross Inc., 147 Banning Road, Ottawa, Ontario K2L 1C5 (Canada)

    2007-09-27

    This article is an examination of the feasibility of electrochemically separating hydrogen obtained by steam reforming a hydrocarbon or alcohol source. A potential advantage of this process is that the carbon dioxide rich exhaust stream should be able to be captured and stored thereby reducing greenhouse gas emissions. Results are presented for the performance of the anode of proton exchange membrane (PEM) electrochemical cell for the separation of hydrogen from a H{sub 2}-CO{sub 2} gas mixture and from a H{sub 2}-CO{sub 2}-CO gas mixture. Experiments were carried out using a single cell state-of-the-art PEM fuel cell. The anode was fed with either a H{sub 2}-CO{sub 2} gas mixture or a H{sub 2}-CO{sub 2}-CO gas mixture and hydrogen was evolved at the cathode. All experiments were performed at room temperature and atmospheric pressure. With the H{sub 2}-CO{sub 2} gas mixture the hydrogen extraction efficiency is quite high. When the gas mixture included CO, however, the hydrogen extraction efficiency is relatively poor. To improve the efficiency for the separation of the gas mixture containing CO, the effect of periodic pulsing on the anode potential was examined. Results show that pulsing can substantially reduce the anode potential thereby improving the overall efficiency of the separation process although the anode potential of the CO poisoned and pulsed cell still lies above that of an unpoisoned cell. (author)

  18. Electrochemical separation of hydrogen from reformate using PEM fuel cell technology

    Science.gov (United States)

    Gardner, C. L.; Ternan, M.

    This article is an examination of the feasibility of electrochemically separating hydrogen obtained by steam reforming a hydrocarbon or alcohol source. A potential advantage of this process is that the carbon dioxide rich exhaust stream should be able to be captured and stored thereby reducing greenhouse gas emissions. Results are presented for the performance of the anode of proton exchange membrane (PEM) electrochemical cell for the separation of hydrogen from a H 2-CO 2 gas mixture and from a H 2-CO 2-CO gas mixture. Experiments were carried out using a single cell state-of-the-art PEM fuel cell. The anode was fed with either a H 2-CO 2 gas mixture or a H 2-CO 2-CO gas mixture and hydrogen was evolved at the cathode. All experiments were performed at room temperature and atmospheric pressure. With the H 2-CO 2 gas mixture the hydrogen extraction efficiency is quite high. When the gas mixture included CO, however, the hydrogen extraction efficiency is relatively poor. To improve the efficiency for the separation of the gas mixture containing CO, the effect of periodic pulsing on the anode potential was examined. Results show that pulsing can substantially reduce the anode potential thereby improving the overall efficiency of the separation process although the anode potential of the CO poisoned and pulsed cell still lies above that of an unpoisoned cell.

  19. Development of Polymer Electrolyte Mambrane (PEM) from Bisphonol S for Direct Methanol Fuel Cell (DMFC)

    Science.gov (United States)

    Changkhamchom, Sairung

    2009-03-01

    The currently used Proton Exchange Membrane (PEM) in a Direct Methanol Fuel Cell (DMFC) is Nafion^, an excellent proton conductor in a fully hydrated membrane. However, it has major drawbacks, such as very high cost, and loss of conductivity at elevated temperature and low humidity. In this work, a novel PEM based on sulfonated poly(ether ether ketone) (S-PEEK). Poly(ether ether ketone) (PEEK) was synthesized by the nucleophilic aromatic substitution polycondensation of Bisphonol-S and 4,4'-difluorobenzophenone for system A, and Bisphenol S and 4,4'-dichlorobenzophenone for system B. Bisphenol-S helps to increase the thermal stability due to its high melting point (245^oC). The post-sulfonation reaction was performed by using concentrated sulfuric acid. Sulfonated poly(ether ether ketone) (S-PEEK) samples were characterized by FTIR and ^1H-NMR to confirm the chemical structure of the S-PEEK, and by TGA to investigate the thermal property.

  20. Dynamics of water droplets detached from porous surfaces of relevance to PEM fuel cells.

    Science.gov (United States)

    Theodorakakos, A; Ous, T; Gavaises, M; Nouri, J M; Nikolopoulos, N; Yanagihara, H

    2006-08-15

    The detachment of liquid droplets from porous material surfaces used with proton exchange membrane (PEM) fuel cells under the influence of a cross-flowing air is investigated computationally and experimentally. CCD images taken on a purpose-built transparent fuel cell have revealed that the water produced within the PEM is forming droplets on the surface of the gas-diffusion layer. These droplets are swept away if the velocity of the flowing air is above a critical value for a given droplet size. Static and dynamic contact angle measurements for three different carbon gas-diffusion layer materials obtained inside a transparent air-channel test model have been used as input to the numerical model; the latter is based on a Navier-Stokes equations flow solver incorporating the volume of fluid (VOF) two-phase flow methodology. Variable contact angle values around the gas-liquid-solid contact-line as well as their dynamic change during the droplet shape deformation process, have allowed estimation of the adhesion force between the liquid droplet and the solid surface and successful prediction of the separation line at which droplets loose their contact from the solid surface under the influence of the air stream flowing around them. Parametric studies highlight the relevant importance of various factors affecting the detachment of the liquid droplets from the solid surface.

  1. Analysis of Heat Transport in a Proton Exchange Membrane (PEM Fuel Cell

    Directory of Open Access Journals (Sweden)

    E. Afshari

    2009-01-01

    Full Text Available In this study a two-phases, single-domain and non-isothermal model of a Proton Exchange Membrane (PEM fuel cell has been studied to investigate thermal management effects on fuel cell performance. A set of governing equations, conservation of mass, momentum, species, energy and charge for gas diffusion layers, catalyst layers and the membrane regions are considered. These equations are solved numerically in a single domain, using finite-volume-based computational fluid dynamics technique. Also the effects of four critical parameters that are thermal conductivity of gas diffusion layer, relative humidity, operating temperature and current density on the PEM fuel cell performance is investigated. In low operating temperatures the resistance within the membrane increases and this could cause rapid decrease in potential. High operating temperature would also reduce transport losses and it would lead to increase in electrochemical reaction rate. This could virtually result in decreasing the cell potential due to an increasing water vapor partial pressure and the membrane water dehydration. Another significant result is that the temperature distribution in GDL is almost linear but within membrane is highly non-linear. However at low current density the temperature across all regions of the cell dose not change significantly. The cell potential increases with relative humidity and improved hydration which reduces ohmic losses. Also the temperature within the cell is much higher with reduced GDL thermal conductivities. The numerical model which is developed is validated with published experimental data and the results are in good agreement.

  2. Nanostructured F doped IrO2 electro-catalyst powders for PEM based water electrolysis

    Science.gov (United States)

    Kadakia, Karan Sandeep; Jampani, Prashanth H.; Velikokhatnyi, Oleg I.; Datta, Moni Kanchan; Park, Sung Kyoo; Hong, Dae Ho; Chung, Sung Jae; Kumta, Prashant N.

    2014-12-01

    Fluorine doped iridium oxide (IrO2:F) powders with varying F content ranging from 0 to 20 wt.% has been synthesized by using a modification of the Adams fusion method. The precursors (IrCl4 and NH4F) are mixed with NaNO3 and heated to elevated temperatures to form high surface area nanomaterials as electro-catalysts for PEM based water electrolysis. The catalysts were then coated on a porous Ti substrate and have been studied for the oxygen evolution reaction in PEM based water electrolysis. The IrO2:F with an optimum composition of IrO2:10 wt.% F shows remarkably superior electrochemical activity and chemical stability compared to pure IrO2. The results have also been supported via kinetic studies by conducting rotating disk electrode (RDE) experiments. The RDE studies confirm that the electro-catalysts follow the two electron transfer reaction for electrolysis with calculated activation energy of ∼25 kJ mol-1. Single full cell tests conducted also validate the superior electrochemical activity of the 10 wt.% F doped IrO2.

  3. STEAM AND SOFC BASED REFORMING OPTIONS OF PEM FUEL CELLS FOR MARINE APPLICATIONS

    Directory of Open Access Journals (Sweden)

    Mohamed M. El Gohary

    2015-06-01

    Full Text Available The need for green energy sources without or with low emissions in addition to improve the using efficiency of current fossil fuels in the marine field makes it important to replace or improve current fossil-fuelled engines. The replacement process should work on narrowing the gap between the most scientific innovative clean energy technologies and the concepts of feasibility and cost-effective solutions. Early expectations of very low emissions and relatively high efficiencies have been met in marine power plants using fuel cell. In this study, steam and SOFC based reforming options of natural gas for PEM fuel cells are proposed as an attractive option to limit the environmental impact of the marine sector. The benefits of these two different reforming options can be assessed using computer predictions incorporating chemical flow sheeting software. It is found that a high overall efficiency approaching 60% may be achieved using SOFC based reforming systems which are significantly better than a reformed PEM system or an SOFC only system.

  4. PEM fuel cell fault detection and identification using differential method: simulation and experimental validation

    Science.gov (United States)

    Frappé, E.; de Bernardinis, A.; Bethoux, O.; Candusso, D.; Harel, F.; Marchand, C.; Coquery, G.

    2011-05-01

    PEM fuel cell performance and lifetime strongly depend on the polymer membrane and MEA hydration. As the internal moisture is very sensitive to the operating conditions (temperature, stoichiometry, load current, water management…), keeping the optimal working point is complex and requires real-time monitoring. This article focuses on PEM fuel cell stack health diagnosis and more precisely on stack fault detection monitoring. This paper intends to define new, simple and effective methods to get relevant information on usual faults or malfunctions occurring in the fuel cell stack. For this purpose, the authors present a fault detection method using simple and non-intrusive on-line technique based on the space signature of the cell voltages. The authors have the objective to minimize the number of embedded sensors and instrumentation in order to get a precise, reliable and economic solution in a mass market application. A very low number of sensors are indeed needed for this monitoring and the associated algorithm can be implemented on-line. This technique is validated on a 20-cell PEMFC stack. It demonstrates that the developed method is particularly efficient in flooding case. As a matter of fact, it uses directly the stack as a sensor which enables to get a quick feedback on its state of health.

  5. Current Density Distribution Mapping in PEM Fuel Cells as An Instrument for Operational Measurements

    Directory of Open Access Journals (Sweden)

    Martin Geske

    2010-04-01

    Full Text Available A newly developed measurement system for current density distribution mapping has enabled a new approach for operational measurements in proton exchange membrane fuel cells (PEMFC. Taking into account previously constructed measurement systems, a method based on a multi layer printed circuit board was chosen for the development of the new system. This type of system consists of a sensor, a special electronic device and the control and visualization PC. For the acquisition of the current density distribution values, a sensor device was designed and installed within a multilayer printed circuit board with integrated shunt resistors. Varying shunt values can be taken into consideration with a newly developed and evaluated calibration method. The sensor device was integrated in a PEM fuel cell stack to prove the functionality of the whole measurement system. A software application was implemented to visualize and save the measurement values. Its functionality was verified by operational measurements within a PEMFC system. Measurement accuracy and possible negative reactions of the sensor device during PEMFC operation are discussed in detail in this paper. The developed system enables operational measurements for different operating phases of PEM fuel cells. Additionally, this can be seen as a basis for new opportunities of optimization for fuel cell design and operation modes.

  6. Synthesis/design optimization of SOFC-PEM hybrid system under uncertainty

    Institute of Scientific and Technical Information of China (English)

    Lingjun Tan; Chen Yang; Nana Zhou

    2015-01-01

    Solid oxide fuel cell–proton exchange membrane (SOFC–PEM) hybrid system is being foreseen as a valuable alternative for power generation. As this hybrid system is a conceptual design, many uncertainties involving input values should be considered at the early stage of process optimization. We present in this paper a general-ized framework of multi-objective optimization under uncertainty for the synthesis/design optimization of the SOFC–PEM hybrid system. The framework is based on geometric, economic and electrochemical models and focuses on evaluating the effect of uncertainty in operating parameters on three conflicting objectives:electricity efficiency, SOFC current density and capital cost of system. The multi-objective optimization provides solutions in the form of a Pareto surface, with a range of possible synthesis/design solutions and a logical procedure for searching the global optimum solution for decision maker. Comparing the stochastic and deterministic Pareto surfaces of different objectives, we conclude that the objectives are considerably influenced by uncertainties because the two trade-off surfaces are different.

  7. Characterisation and modelling of a high temperature PEM fuel cell stack using electrochemical impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Jespersen, J.L. [Danish Technological Institute, Kongsvang Alle 29, DK-8000 Arhus C (Denmark); Schaltz, E.; Kaer, S.K. [Department of Energy Technology, Aalborg University, Pontoppidanstraede 101, DK-9220 Aalborg East (Denmark); Andreasen, S.J.

    2009-08-15

    In designing and controlling fuel cell systems, it is advantageous to have models which predict fuel cell behaviour in steady-state as well as in dynamic operation. This work examines the use of electro-chemical impedance spectroscopy (EIS) for characterising and developing an impedance model for a high temperature PEM (HT-PEM) fuel cell stack. A Labview virtual instrument has been developed to perform the signal generation and data acquisition which is needed to perform EIS. The typical output of an EIS measurement on a fuel cell is a Nyquist plot, which shows the imaginary and real parts of the impedance of the measured system. The full stack impedance depends on the impedance of each of the single cells of the stack. Equivalent circuit models for each single cell can be used to predict the stack impedance at different temperature profiles of the stack. The information available in such models can be used to predict the fuel cell stack performance, e.g. in systems where different electronic components introduce current harmonics. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  8. 小型风光互补反渗透海水淡化装置研制%THE RESEARCH ON THE DEVELOPMENT OF SMALL WIND AND SOLAR COMPLEMENTARY REVERSE OSMOSIS DESALINATION UNIT

    Institute of Scientific and Technical Information of China (English)

    何小龙; 杨树涛; 王侃; 张小平; 许建刚; 张希建

    2012-01-01

    The wind and solar complementary and reverse osmosis desalination technology and industry developed rapidly, this article introduced the wind and solar-powered desalination device principles and the development of wind and solar complementary reverse osmosis desalination unit, the results showed that the desalination plant energy consumed about 4.8 k Wh/m3, which was suitable for remote islands, ships, lack of electricity supply place for small groups of 3~5 people to provide fresh water of life, which had a strong application prospect, good economic, environmental and social benefits.%介绍了风光互补供电海水淡化装置原理和研制的离网风光互补反渗透海水淡化装置,运行结果表明,该淡化装置吨水能耗约4.8 kWh/m3,适于偏远海岛、船舶、电力供应缺乏的场所,为3~5人的小集体提供生活淡水,具有较强应用推广前景,经济、环境和社会效益明显.

  9. Study on two-phase countercurrent flow and transport phenomenon in PEM of a direct methanol fuel cell

    Institute of Scientific and Technical Information of China (English)

    WANG; Jiang; SHI; Mingheng

    2006-01-01

    Based on the requirement of water management for a direct methanol fuel cell, this paper analyzes qualitatively the mechanism of occurrence and development of a two-phase countercurrent flow with corresponding transport phenomenon in the PEM. A one-dimensional, steady state quantitative model of heat and mass transfer in internal volumetric ohmic heating porous media saturated by liquid and vapor phases is developed. The effects of capillarity, electro-osmotic drag and phase change are included. Two important formulas to calculate the theoretical length of two-phase zone δt and determine the critical criterion |-ω/γ|cr for dryout in PEM are deduced. By use of these two dimensionless parameters, dryout of PEM can be easily predicted. Theoretical temperature, pressure and saturation profiles within the two-phase region are obtained numerically, which can help to explore the performance of a DMFC operating in its ohmic polarization region. The simulation results can be used to determine the catalyst content of cathode catalyst layer and the corresponding optimal thickness of PEM.

  10. PEM fuel cell stack performance using dilute hydrogen mixture. Implications on electrochemical engine system performance and design

    Energy Technology Data Exchange (ETDEWEB)

    Inbody, M.A.; Vanderborgh, N.E.; Hedstrom, J.C.; Tafoya, J.I. [Los Alamos National Lab., NM (United States)

    1996-12-31

    Onboard fuel processing to generate a hydrogen-rich fuel for PEM fuel cells is being considered as an alternative to stored hydrogen fuel for transportation applications. If successful, this approach, contrasted to operating with onboard hydrogen, utilizes the existing fuels infrastructure and provides required vehicle range. One attractive, commercial liquid fuels option is steam reforming of methanol. However, expanding the liquid methanol infrastructure will take both time and capital. Consequently technology is also being developed to utilize existing transportation fuels, such as gasoline or diesel, to power PEM fuel cell systems. Steam reforming of methanol generates a mixture with a dry gas composition of 75% hydrogen and 25% carbon dioxide. Steam reforming, autothermal reforming, and partial oxidation reforming of C{sub 2} and larger hydrocarbons produces a mixture with a more dilute hydrogen concentration (65%-40%) along with carbon dioxide ({approx}20%) and nitrogen ({approx}10%-40%). Performance of PEM fuel cell stacks on these dilute hydrogen mixtures will affect the overall electrochemical engine system design as well as the overall efficiency. The Los Alamos Fuel Cell Stack Test facility was used to access the performance of a PEM Fuel cell stack over the range of gas compositions chosen to replicate anode feeds from various fuel processing options for hydrocarbon and alcohol fuels. The focus of the experiments was on the anode performance with dilute hydrogen mixtures with carbon dioxide and nitrogen diluents. Performance with other anode feed contaminants, such as carbon monoxide, are not reported here.

  11. Multi-phase micro-scale flow simulation in the electrodes of a PEM fuel cell by lattice Boltzmann method

    Science.gov (United States)

    Park, J.; Li, X.

    The gas diffusion layer of a polymer electrolyte membrane (PEM) fuel cell is a porous medium generally made of carbon cloth or paper. The gas diffusion layer has been modeled conventionally as a homogeneous porous medium with a constant permeability in the literature of PEM fuel cell. However, in fact, the permeability of such fibrous porous medium is strongly affected by the fiber orientation having non-isotropic permeability. In this work, the lattice Boltzmann (LB) method is applied to the multi-phase flow phenomenon in the inhomogeneous gas diffusion layer of a PEM fuel cell. The inhomogeneous porous structure of the carbon cloth and carbon paper has been modeled as void space and porous area using Stokes/Brinkman formulation and void space and impermeable fiber distributions obtained from various microscopic images. The permeability of the porous medium is calculated and compared to the experimental measurements in literature showing a good agreement. Simulation results for various fiber distributions indicate that the permeability of the medium is strongly influenced by the effect of fiber orientation. Present lattice Boltzmann flow models are applied to the multi-phase flow simulations by incorporating multi-component LB model with inter-particle interaction forces. The model successfully simulates the complicated unsteady behaviors of liquid droplet motion in the porous medium providing a useful tool to investigate the mechanism of liquid water accumulation/removal in a gas diffusion layer of a PEM fuel cell.

  12. Modeling of PEM Fuel Cell Stack System using Feed-forward and Recurrent Neural Networks for Automotive Applications

    Directory of Open Access Journals (Sweden)

    Mr. M. Karthik

    2014-05-01

    Full Text Available Artificial Neural Network (ANN has become a significant modeling tool for predicting the performance of complex systems that provide appropriate mapping between input-output variables without acquiring any empirical relationship due to the intrinsic properties. This paper is focussed towards the modeling of Proton Exchange Membrane (PEM Fuel Cell system using Artificial Neural Networks especially for automotive applications. Three different neural networks such as Static Feed Forward Network (SFFN, Cascaded Feed Forward Network (CFFN & Fully Connected Dynamic Recurrent Network (FCRN are discussed in this paper for modeling the PEM Fuel Cell System. The numerical analysis is carried out between the three Neural Network architectures for predicting the output performance of the PEM Fuel Cell. The performance of the proposed Networks is evaluated using various error criteria such as Mean Square Error, Mean Absolute Percentage Error, Mean Absolute Error, Coefficient of correlation and Iteration Values. The optimum network with high performance indices (low prediction error values and iteration values can be used as an ancillary model in developing the PEM Fuel Cell powered vehicle system. The development of the fuel cell driven vehicle model also incorporates the modeling of DC-DC Power Converter and Vehicle Dynamics. Finally the Performance of the Electric vehicle model is analyzed for two different drive cycle such as M-NEDC & M-UDDS.

  13. Validity of the Participation and Environment Measure for Children and Youth (PEM-CY) for Health Impact Assessment (HIA) in sustainable development projects.

    Science.gov (United States)

    Khetani, Mary; Marley, Jenifer; Baker, Megan; Albrecht, Erin; Bedell, Gary; Coster, Wendy; Anaby, Dana; Law, Mary

    2014-04-01

    Participation in home, school, and community activities is an important indicator of child health and well-being. Evaluating environmental influences on children's participation can inform efforts to develop sustainable built environments, but few validated measures exist. To examine the concurrent validity and utility of the Participation and Environment Measure for Children and Youth (PEM-CY) for Health Impact Assessment in non-urban sustainable development projects affecting children with disabilities. Eighty-nine parents of children and youth with disabilities who identified as residing in a small town or rural community were sampled. Sixty-six caregivers completed the PEM-CY online, and 23 caregivers completed the PEM-CY and CHIEF-CP paper forms. Spearman correlational analyses were conducted to establish the concurrent validity of the PEM-CY environment sections against the CHIEF-CP. Group comparisons by child's age, number of functional limitations, and annual household income were used to examine differences in summary and item-level responses on the PEM-CY community section. Moderate to strong associations were found between CHIEF-CP Total Product and Magnitude Scores and all PEM-CY Environment Summary Scores. CHIEF-CP Physical/Structural and Policies Subscale Scores were most consistently associated with PEM-CY Environment Summary Scores. Group differences by household income were found for participation frequency and number of supports, including perceived availability and adequacy of money and information about programs and services, even when controlling child's age and number of functional limitations. Study results lend support to the use of the PEM-CY in HIA to reliably assess for environmental impact on children's participation. Implications for using the PEM-CY to inform decision-making in non-urban sustainable development projects affecting families of children and youth with disabilities are discussed. Published by Elsevier Inc.

  14. X-ray absorption spectroscopy for characterisation of catalysts for PEM fuel cells; Roentgenabsorptionsspektroskopie zur Charakterisierung von Katalysatoren fuer die PEM-Brennstoffzelle

    Energy Technology Data Exchange (ETDEWEB)

    Koehl, G.

    2001-10-01

    The investigation of bimetallic nanoparticles is of great interest for the development of powerful anode catalysts in PEM fuel cells. The determination of their electronic and geometric structure is crucial for the optimization of the activity and selectivity in the fuel cell. Especially carbon supported PtRu particles have shown superior activity as anode catalysts due to their high CO tolerance. To state the reason on an atomic level, X-ray absorption spectroscopy (XAS) with synchrotron radiation has been used to examine several Pt and PtRu nanoparticle systems. They were either prepared on the basis of preformed PtRu alloy colloids stabilized by different surfactants or by chemical reduction of precursors, Na{sub 6}Pt(SO{sub 3}){sub 4} and Na{sub 6}Ru(SO{sub 3}){sub 4}. Although a PtRu interaction was observed in all systems, a nonstatistical distribution of Pt and Ru atoms in the nanoparticles could be verified. In additional investigations the reaction mechanism during the synthesis of an organometallic stabilized Pt colloid was examined. In-situ measurements revealed the formation of an hitherto unknown Pt complex as intermediate state prior to the nucleation of the particles. (orig)

  15. Gas/Water and Heat Management of PEM-Based Fuel Cell and Electrolyzer Systems for Space Applications

    Science.gov (United States)

    Guo, Qing; Ye, Fang; Guo, Hang; Ma, Chong Fang

    2016-11-01

    Hydrogen/oxygen fuel cells were successfully utilized in the field of space applications to provide electric energy and potable water in human-rated space mission since the 1960s. Proton exchange membrane (PEM) based fuel cells, which provide high power/energy densities, were reconsidered as a promising space power equipment for future space exploration. PEM-based water electrolyzers were employed to provide life support for crews or as major components of regenerative fuel cells for energy storage. Gas/water and heat are some of the key challenges in PEM-based fuel cells and electrolytic cells, especially when applied to space scenarios. In the past decades, efforts related to gas/water and thermal control have been reported to effectively improve cell performance, stability lifespan, and reduce mass, volume and costs of those space cell systems. This study aimed to present a primary review of research on gas/water and waste thermal management for PEM-based electrochemical cell systems applied to future space explorations. In the fuel cell system, technologies related to reactant supplement, gas humidification, water removal and active/passive water separation were summarized in detail. Experimental studies were discussed to provide a direct understanding of the effect of the gas-liquid two-phase flow on product removal and mass transfer for PEM-based fuel cell operating in a short-term microgravity environment. In the electrolyzer system, several active and static passive phaseseparation methods based on diverse water supplement approaches were discussed. A summary of two advanced passive thermal management approaches, which are available for various sizes of space cell stacks, was specifically provided

  16. Gas/Water and Heat Management of PEM-Based Fuel Cell and Electrolyzer Systems for Space Applications

    Science.gov (United States)

    Guo, Qing; Ye, Fang; Guo, Hang; Ma, Chong Fang

    2017-02-01

    Hydrogen/oxygen fuel cells were successfully utilized in the field of space applications to provide electric energy and potable water in human-rated space mission since the 1960s. Proton exchange membrane (PEM) based fuel cells, which provide high power/energy densities, were reconsidered as a promising space power equipment for future space exploration. PEM-based water electrolyzers were employed to provide life support for crews or as major components of regenerative fuel cells for energy storage. Gas/water and heat are some of the key challenges in PEM-based fuel cells and electrolytic cells, especially when applied to space scenarios. In the past decades, efforts related to gas/water and thermal control have been reported to effectively improve cell performance, stability lifespan, and reduce mass, volume and costs of those space cell systems. This study aimed to present a primary review of research on gas/water and waste thermal management for PEM-based electrochemical cell systems applied to future space explorations. In the fuel cell system, technologies related to reactant supplement, gas humidification, water removal and active/passive water separation were summarized in detail. Experimental studies were discussed to provide a direct understanding of the effect of the gas-liquid two-phase flow on product removal and mass transfer for PEM-based fuel cell operating in a short-term microgravity environment. In the electrolyzer system, several active and static passive phaseseparation methods based on diverse water supplement approaches were discussed. A summary of two advanced passive thermal management approaches, which are available for various sizes of space cell stacks, was specifically provided

  17. Development of a computational model applied to a unitary 144 CM{sup 2} proton exchange membrane fuel cell; Desenvolvimento de um modelo numerico computacional aplicado a uma celula a combustivel unitaria de 144 CM{sup 2} tipo PEM

    Energy Technology Data Exchange (ETDEWEB)

    Robalinho, Eric

    2009-07-01

    This work presents the development of a numerical computer model and methodology to study and design polymeric exchange membrane fuel cell - PEM. For the validation of experimental results, a sequence of routines, appropriate to fit the data obtained in the laboratory, was described. At the computational implementation it was created a new strategy of coupling two 3-dimensional models to satisfy the requirements of the comprehensive model of the fuel cell, including its various geometries and materials, as well as the various physical and chemical processes simulated. To effective assessment of the real cell analogy with numerical model, numerical studies were carried out. Comparisons with values obtained in the literature, characterization of variables through laboratory experiments and estimates from models already tested in the literature were also performed. Regarding the experimental part, a prototype of a fuel cell unit of 144 cm{sup 2} of geometric area was designed, produced and operated at laboratory with the purpose of validating the numerical computer model proposed, with positive results. The results of simulations for the 2D and 3D geometries proposed are presented in the form of polarization curves, highlighting the catalytic layer model based on the geometry of agglomerates. Parametric and sensitivity studies are presented to illustrate the change in performance of the fuel cell studied. The final model is robust and useful as a tool for design and optimization of PEM type fuel cells in a wide range of operating conditions. (author)

  18. Development of a computational model applied to a unitary 144 cm{sup 2} proton exchange membrane fuel cell; Desenvolvimento de um modelo numerico computacional aplicado a uma celula a combustivel unitaria de 144 CM{sup 2} tipo PEM

    Energy Technology Data Exchange (ETDEWEB)

    Robalinho, Eric

    2009-07-01

    This work presents the development of a numerical computer model and methodology to study and design polymeric exchange membrane fuel cell - PEM. For the validation of experimental results, a sequence of routines, appropriate to fit the data obtained in the laboratory, was described. At the computational implementation it was created a new strategy of coupling two 3-dimensional models to satisfy the requirements of the comprehensive model of the fuel cell, including its various geometries and materials, as well as the various physical and chemical processes simulated. To effective assessment of the real cell analogy with numerical model, numerical studies were carried out. Comparisons with values obtained in the literature, characterization of variables through laboratory experiments and estimates from models already tested in the literature were also performed. Regarding the experimental part, a prototype of a fuel cell unit of 144 cm of geometric area was designed, produced and operated at laboratory with the purpose of validating the numerical computer model proposed, with positive results. The results of simulations for the 2D and 3D geometries proposed are presented in the form of polarization curves, highlighting the catalytic layer model based on the geometry of agglomerates. Parametric and sensitivity studies are presented to illustrate the change in performance of the fuel cell studied. The final model is robust and useful as a tool for design and optimization of PEM type fuel cells in a wide range of operating conditions. (author)

  19. Experimental determination of optimal clamping torque for AB-PEM Fuel cell

    Directory of Open Access Journals (Sweden)

    Noor Ul Hassan

    2016-04-01

    Full Text Available Polymer electrolyte Membrane (PEM fuel cell is an electrochemical device producing electricity by the reaction of hydrogen and oxygen without combustion. PEM fuel cell stack is provided with an appropriate clamping torque to prevent leakage of reactant gases and to minimize the contact resistance between gas diffusion media (GDL and bipolar plates. GDL porous structure and gas permeability is directly affected by the compaction pressure which, consequently, drastically change the fuel cell performance. Various efforts were made to determine the optimal compaction pressure and pressure distributions through simulations and experimentation. Lower compaction pressure results in increase of contact resistance and also chances of leakage. On the other hand, higher compaction pressure decreases the contact resistance but also narrows down the diffusion path for mass transfer from gas channels to the catalyst layers, consequently, lowering cell performance. The optimal cell performance is related to the gasket thickness and compression pressure on GDL. Every stack has a unique assembly pressure due to differences in fuel cell components material and stack design. Therefore, there is still need to determine the optimal torque value for getting the optimal cell performance. This study has been carried out in continuation of deve­lopment of Air breathing PEM fuel cell for small Unmanned Aerial Vehicle (UAV application. Compaction pressure at minimum contact resistance was determined and clamping torque value was calcu­la­ted accordingly. Single cell performance tests were performed at five different clamping torque values i.e 0.5, 1.0, 1.5, 2.0 and 2.5 N m, for achieving optimal cell per­formance. Clamping pressure distribution tests were also performed at these torque values to verify uniform pressure distribution at optimal torque value. Experimental and theoretical results were compared for making inferences about optimal cell perfor­man­ce. A

  20. A semipermeable enzymatic nanoreactor as an efficient modulator for reversible pH regulation

    Science.gov (United States)

    Huang, Yanyan; Lin, Youhui; Ran, Xiang; Ren, Jinsong; Qu, Xiaogang

    2014-09-01

    Here we propose a new concept for the fabrication of a semipermeable enzymatic nanoreactor as an efficient modulator to reversibly switch the pH of an aqueous environment. We used amino-functionalized, expanded mesoporous silica nanoparticles (EMSN) as a model nanocarrier to load enzymes. In order to protect enzymes from the interference of a complicated environment, polyelectrolyte multilayers (PEMs) were coated on the surface of the EMSN through layer by layer (LbL) assembly. These PEMs can serve as semipermeable membranes, allowing small molecules to diffuse in and out freely while trapping the enzymes in the nanoreactors. Compared with traditional electrochemical stimulation or optical control methods, our enzymatic regulation platform is easy to operate without complicated instruments. In addition, this system can cover a wide range of pH values and conveniently regulate pH values by simply controlling the concentrations of catalysts or reactants. Meanwhile, this strategy could be generalized to other enzymes or nanocarriers to achieve reversible pH regulation for different purposes. The switched pH values can be implemented for the modulation of the conformational changes of nucleic acids and activation of the charge conversion in drug delivery applications.Here we propose a new concept for the fabrication of a semipermeable enzymatic nanoreactor as an efficient modulator to reversibly switch the pH of an aqueous environment. We used amino-functionalized, expanded mesoporous silica nanoparticles (EMSN) as a model nanocarrier to load enzymes. In order to protect enzymes from the interference of a complicated environment, polyelectrolyte multilayers (PEMs) were coated on the surface of the EMSN through layer by layer (LbL) assembly. These PEMs can serve as semipermeable membranes, allowing small molecules to diffuse in and out freely while trapping the enzymes in the nanoreactors. Compared with traditional electrochemical stimulation or optical control methods

  1. Performance Degradation Tests of Phosphoric Acid Doped PBI Membrane Based High Temperature PEM Fuel Cells

    DEFF Research Database (Denmark)

    Zhou, Fan; Araya, Samuel Simon; Grigoras, Ionela

    2014-01-01

    Degradation tests of two phosphoric acid (PA) doped PBI membrane based HT-PEM fuel cells were reported in this paper to investigate the effects of start/stop and the presence of methanol in the fuel to the performance degradation. Continuous tests with H2 and simulated reformate which was composed...... of H2, water steam and methanol as the fuel were performed on both single cells. 12-h-startup/12-h-shutdown dynamic tests were performed on the first single cell with pure dry H2 as the fuel and on the second single cell with simulated reformate as the fuel. Along with the tests electrochemical...... techniques such as polarization curves and electrochemical impedance spectroscopy (EIS) were employed to study the degradation mechanisms of the fuel cells. Both single cells showed an increase in the performance in the H2 continuous tests, because of a decrease in the ORR kinetic resistance probably due...

  2. Modelling and Optimization of Reforming Systems for use in PEM Fuel Cell

    DEFF Research Database (Denmark)

    Berry, Melissa; Korsgaard, Anders Risum; Nielsen, Mads Pagh

    2004-01-01

    Three different reforming methods for the conversion of natural gas to hydrogen are studied and compared: Steam Reforming (SR), Auto-thermal Reforming (ATR), and Catalytic Partial Oxidation (CPOX). Thermodynamic and kinetic models are developed for the reforming reactors as well as the subsequent...... reactors needed for CO removal to make the synthesis gas suitable for use in a PEM fuel cell. The systems are optimized to minimize the total volume, and must supply adequate hydrogen to a fuel cell with a 100kW load. The resultant system efficiencies are calculated. The CPOX system is the smallest...... and exhibits a comparable efficiency to the SR system. The SR system had the best relation between efficiency and volume increase. Optimal temperature profiles within each reactor were found. It was shown that temperature control can significantly reduce reactor volume and increase conversion capabilities....

  3. HT-PEM Fuel Cell System with Integrated Thermoelectric Exhaust Heat Recovery

    DEFF Research Database (Denmark)

    Gao, Xin

    for electricity. For this aim, a heat exchanger based TEG heat recovery subsystem is designed. Instead of optimizing an ordinary rectangular heat exchanger, high efficient and commercialized compact plate-fin exchangers are applied. A library of types of them is also included to pinpoint the ideal heat exchanger...... power output on the subsystem design and performance were also systematically analyzed. The TEG subsystem configuration is optimized. The usefulness and convenience of the model are proved. TE coolers (TECs) are integrated into the methanol evaporator of the HT-PEM system for improving the whole system...... in literature are reviewed for their experiences. Afterwards, the project road map is identified by a list of project objectives. The detailed considerations and steps during carrying out the project are addressed in the second chapter. Major innovations out of this project are also highlighted. The third...

  4. Synthesis and characterization of novel sulfonated polyimide containing phthalazinone moieties as PEM for PEMFC

    Institute of Scientific and Technical Information of China (English)

    Hai Yan Pan; Yong Fang Liang; Xiu Ling Zhu; Xi Gao Jian

    2007-01-01

    A novel sulfonated diamine monomer, 1,2-dihydro-2-(3-sulfonic-4-aminophenyl)-4-[4-(4-aminophenoxy)-phenyl]phthalazin1-one (S-DHPZDA), was successfully synthesized by direct sulfonation of diamine 1,2-dihydro-2-(4-aminophenyl)-4-[4-(4-aminophenoxy)-phenyl]-phthalazin- 1-one (DHPZDA). A series of sulfonated polyimides (SPIs), which can be used as the material of the proton exchange membrane (PEM) for the proton exchange membrane fuel cell (PEMFC), were prepared from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), S-DHPZDA, and nonsulfonated diamines DHPZDA. The structure of the monomer and polymers were characterized by FT-IR and 1H NMR. The solubility of the S-DHPZDA-based SPIs has been improved due to the induction of the phthalazione moiety. The SPIs membranes have high thermo-stability, predominant swelling resistance with high ion exchange capacity.

  5. Numerical investigation of flow field configuration and contact resistance for PEM fuel cell performance

    Energy Technology Data Exchange (ETDEWEB)

    Akbari, Mohammad Hadi; Rismanchi, Behzad [Department of Mechanical Engineering, Shiraz University, Shiraz 71348-51154 (Iran)

    2008-08-15

    A steady-state three-dimensional non-isothermal computational fluid dynamics (CFD) model of a proton exchange membrane fuel cell is presented. Conservation of mass, momentum, species, energy, and charge, as well as electrochemical kinetics are considered. In this model, the effect of interfacial contact resistance is also included. The numerical solution is based on a finite-volume method. In this study the effects of flow channel dimensions on the cell performance are investigated. Simulation results indicate that increasing the channel width will improve the limiting current density. However, it is observed that an optimum shoulder size of the flow channels exists for which the cell performance is the highest. Polarization curves are obtained for different operating conditions which, in general, compare favorably with the corresponding experimental data. Such a CFD model can be used as a tool in the development and optimization of PEM fuel cells. (author)

  6. Iron-based alloy and nitridation treatment for PEM fuel cell bipolar plates

    Science.gov (United States)

    Brady, Michael P [Oak Ridge, TN; Yang, Bing [Oak Ridge, TN; Maziasz, Philip J [Oak Ridge, TN

    2010-11-09

    A corrosion resistant electrically conductive component that can be used as a bipolar plate in a PEM fuel cell application is composed of an alloy substrate which has 10-30 wt. % Cr, 0.5 to 7 wt. % V, and base metal being Fe, and a continuous surface layer of chromium nitride and vanadium nitride essentially free of base metal. A oxide layer of chromium vanadium oxide can be disposed between the alloy substrate and the continuous surface nitride layer. A method to prepare the corrosion resistant electrically conductive component involves a two-step nitridization sequence by exposing the alloy to a oxygen containing gas at an elevated temperature, and subsequently exposing the alloy to an oxygen free nitrogen containing gas at an elevated temperature to yield a component where a continuous chromium nitride layer free of iron has formed at the surface.

  7. Coupling a PEM fuel cell and the hydrogen generation from aluminum waste cans

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, Susana Silva; Albanil Sanchez, Loyda; Alvarez Gallegos, Alberto A. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas, Av. Universidad 1001, Col. Chamilpa, Cuernavaca, Mor. CP 62210 (Mexico); Sebastian, P.J. [Centro de Investigacion en Energia-UNAM, 62580 Temixco, Morelos (Mexico); Cuerpo Academico de Energia y Sustentabilidad, UPCH, Tuxtla Gutierrez, Chiapas (Mexico)

    2007-10-15

    High purity hydrogen was generated from the chemical reaction of aluminum and sodium hydroxide. The aluminum used in this study was obtained from empty soft drink cans and treated with concentrated sulfuric acid to remove the paint and plastic film. One gram of aluminum was reacted with a solution of 2moldm{sup -3} of sodium hydroxide to produce hydrogen. The hydrogen produced from aluminum cans and oxygen obtained from a proton exchange membrane electrolyzer or air, was fed to a proton exchange membrane (PEM) fuel cell to produce electricity. Yields of 44 mmol of hydrogen contained in a volume of 1.760dm{sup 3} were produced from one gram of aluminum in a time period of 20 min. (author)

  8. Nanostructured Electrocatalysts for PEM Fuel Cells and Redox Flow Batteries: A Selected Review

    Energy Technology Data Exchange (ETDEWEB)

    Shao, Yuyan; Cheng, Yingwen; Duan, Wentao; Wang, Wei; Lin, Yuehe; Wang, Yong; Liu, Jun

    2015-12-04

    PEM fuel cells and redox flow batteries are two very similar technologies which share common component materials and device design. Electrocatalysts are the key components in these two devices. In this Review, we discuss recent progress of electrocatalytic materials for these two technologies with a focus on our research activities at Pacific Northwest National Laboratory (PNNL) in the past years. This includes (1) nondestructive functionalization of graphitic carbon as Pt support to improve its electrocatalytic performance, (2) triple-junction of metal–carbon–metal oxides to promote Pt performance, (3) nitrogen-doped carbon and metal-doped carbon (i.e., metal oxides) to improve redox reactions in flow batteries. A perspective on future research and the synergy between the two technologies are also discussed.

  9. FITTING A THREE DIMENSIONAL PEM FUEL CELL MODEL TO MEASUREMENTS BY TUNING THE POROSITY AND

    DEFF Research Database (Denmark)

    Bang, Mads; Odgaard, Madeleine; Condra, Thomas Joseph

    2004-01-01

    PEM fuel cell are dealt with in detail.The model solves the convective and diffusive transport of thegaseous phase in the fuel cell and allows prediction of theconcentration of the species present. A special feature of themodel is a method that allows detailed modelling and predictionof electrode kinetics...... dependency on the gas concentration andactivation overpotential can thereby be addressed. The proposedmodel makes it possible to predict the effect of geometrical andmaterial properties on the fuel cell?s performance. It is shownhow the ionic conductivity and porosity of the catalyst layeraffects...... the distribution of current density and further how thisaffects the polarization curve.The porosity and conductivity of the catalyst layer are some ofthe most difficult parameters to measure, estimate and especiallycontrol. Yet the proposed model shows how these two parameterscan have significant influence...

  10. Modeling and Experimental Study of PEM Fuel Cell Transient Response for Automotive Applications

    Institute of Scientific and Technical Information of China (English)

    HUA Jianfeng; XU Liangfei; LIN Xinfan; LU Languang; OUYANG Minggao

    2009-01-01

    This paper presents an analysis of the dynamic response of a low pressure proton exchange membrane (PEM) fuel cell stack to step changes in load, which are characteristic of automotive fuel cell system applications. The goal is a better understanding of the electrical and electrochemical processes when accounting for the characteristic cell voltage response during transients. The analysis and experiment are based on a low pressure 5 kW proton exchange membrane fuel cell (PEMFC) stack, which is similar to those used in several of Tsinghua's fuel cell buses. The experimental results provide an effective improvement reference for the power train control scheme of the fuel cell buses in Olympic demonstration in Beijing 2008.

  11. Distribution of the Current Density in Electrolyte of the Pem Fuel Cell

    Directory of Open Access Journals (Sweden)

    Eugeniusz Kurgan

    2004-01-01

    Full Text Available In this paper water management in proton exchange membrane (PEM fuel cell is considered. Firt mass convervation law for water is applied. Next proton transport is described by the Nernst-Planck equation and liqid water convection velocity is eliminated by the Schlogl equation. Electro-osmotic drag coefficient is related to hydrogen index and experimentally determined swelling coefficient. Three partial differential equations for molar water concentration Cw, electric potential ϕ and water pressure Pw are formulated. Current density vector i is derived from proton flux expression. These equations together with adequate boundary conditions were solved using finite element method. The distribution of electric potential and current density in function of geometrical parametres is investigated. At the end some illustrative example is given.

  12. Distributed generation system with PEM fuel cell for electrical power quality improvement

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez, D.; Beites, L.F.; Blazquez, F. [Department of Electrical Engineering, ETSII, Escuela de Ingenieros Industriales, Universidad Politecnica de Madrid, C/ Jose Gutierrez Abascal 2, 28006 Madrid (Spain); Ballesteros, J.C. [Endesa Generacion, S.A. c/ Ribera de Loira 60, 28042 Madrid (Spain)

    2008-08-15

    In this paper, a physical model for a distributed generation (DG) system with power quality improvement capability is presented. The generating system consists of a 5 kW PEM fuel cell, a natural gas reformer, hydrogen storage bottles and a bank of ultra-capacitors. Additional power quality functions are implemented with a vector-controlled electronic converter for regulating the injected power. The capabilities of the system were experimentally tested on a scaled electrical network. It is composed of different lines, built with linear inductances and resistances, and taking into account both linear and non-linear loads. The ability to improve power quality was tested by means of different voltage and frequency perturbations produced on the physical model electrical network. (author)

  13. Durability of Membrane Electrode Assemblies (MEAs) in PEM Fuel Cells Operated on Pure Hydrogen and Oxygen

    Science.gov (United States)

    Stanic, Vesna; Braun, James; Hoberecht, Mark

    2003-01-01

    Proton exchange membrane (PEM) fuel cells are energy sources that have the potential to replace alkaline fuel cells for space programs. Broad power ranges, high peak-to-nominal power capabilities, low maintenance costs, and the promise of increased life are the major advantages of PEM technology in comparison to alkaline technology. The probability of PEM fuel cells replacing alkaline fuel cells for space applications will increase if the promise of increased life is verified by achieving a minimum of 10,000 hours of operating life. Durability plays an important role in the process of evaluation and selection of MEAs for Teledyne s Phase I contract with the NASA Glenn Research Center entitled Proton Exchange Membrane Fuel cell (PEMFC) Power Plant Technology Development for 2nd Generation Reusable Launch Vehicles (RLVs). For this contract, MEAs that are typically used for H2/air operation were selected as potential candidates for H2/O2 PEM fuel cells because their catalysts have properties suitable for O2 operation. They were purchased from several well-established MEA manufacturers who are world leaders in the manufacturing of diverse products and have committed extensive resources in an attempt to develop and fully commercialize MEA technology. A total of twelve MEAs used in H2/air operation were initially identified from these manufacturers. Based on the manufacturers specifications, nine of these were selected for evaluation. Since 10,000 hours is almost equivalent to 14 months, it was not possible to perform continuous testing with each MEA selected during Phase I of the contract. Because of the lack of time, a screening test on each MEA was performed for 400 hours under accelerated test conditions. The major criterion for an MEA pass or fail of the screening test was the gas crossover rate. If the gas crossover rate was higher than the membrane intrinsic permeability after 400 hours of testing, it was considered that the MEA had failed the test. Three types of

  14. Hydrogen-Oxygen PEM Regenerative Fuel Cell Development at the NASA Glenn Research Center

    Science.gov (United States)

    Bents, David J.; Scullin, Vincent J.; Chang, Bei-Jiann; Johnson, Donald W.; Garcia, Christoher P.; Jakupca, Ian J.

    2005-01-01

    The closed-cycle hydrogen-oxygen PEM regenerative fuel cell (RFC) at the NASA Glenn Research Center has successfully demonstrated closed cycle operation at rated power for multiple charge-discharge cycles. During charge cycle the RFC has absorbed input electrical power simulating a solar day cycle ranging from zero to 15 kWe peak, and delivered steady 5 kWe output power for periods exceeding 8 hr. Orderly transitions from charge to discharge mode, and return to charging after full discharge, have been accomplished without incident. Continuing test operations focus on: (1) Increasing the number of contiguous uninterrupted charge discharge cycles; (2) Increasing the performance envelope boundaries; (3) Operating the RFC as an energy storage device on a regular basis; (4) Gaining operational experience leading to development of fully automated operation; and (5) Developing instrumentation and in situ fluid sampling strategies to monitor health and anticipate breakdowns.

  15. Heat management in a portable high temperature PEM fuel cell module with open cathode

    Energy Technology Data Exchange (ETDEWEB)

    Kurz, T.; Keller, J. [Fraunhofer Institute for Solar Energy Systems, Freiburg (Germany)

    2011-08-15

    The development and characterisation of a portable high temperature PEM fuel cell module is presented. The module consists of a 5-cell stack with open cathodes and coil compression. This design enables the operation and control with only one fan and compact and lightweight packaging. The stack is characterised with polarisation curves and single cell impedance spectroscopy. Temperature distribution in the stack and temperature control is analysed during startup and operation. The results show very similar cell characteristics and stable operation with high power density. Temperature control shows a good reaction on load changes as well as on setpoint changes. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. The electronics system for the LBNL positron emission mammography (PEM) camera

    CERN Document Server

    Moses, W W; Baker, K; Jones, W; Lenox, M; Ho, M H; Weng, M

    2001-01-01

    Describes the electronics for a high-performance positron emission mammography (PEM) camera. It is based on the electronics for a human brain positron emission tomography (PET) camera (the Siemens/CTI HRRT), modified to use a detector module that incorporates a photodiode (PD) array. An application-specified integrated circuit (ASIC) services the photodetector (PD) array, amplifying its signal and identifying the crystal of interaction. Another ASIC services the photomultiplier tube (PMT), measuring its output and providing a timing signal. Field-programmable gate arrays (FPGAs) and lookup RAMs are used to apply crystal-by-crystal correction factors and measure the energy deposit and the interaction depth (based on the PD/PMT ratio). Additional FPGAs provide event multiplexing, derandomization, coincidence detection, and real-time rebinning. Embedded PC/104 microprocessors provide communication, real-time control, and configure the system. Extensive use of FPGAs make the overall design extremely flexible, all...

  17. Development of an empirical dynamic model for a Nexa PEM fuel cell power module

    Energy Technology Data Exchange (ETDEWEB)

    Soltani, Mehdi; Mohammad Taghi Bathaee, S. [Power Systems Laboratory, Department of Electrical Engineering, K.N. Toosi University of Technology, 16317-14191 Tehran (Iran)

    2010-12-15

    The goal of this study is to develop a fuel cell model which is capable of characterizing fuel cell steady-state performance as well as dynamic behavior. In this paper a new dynamic model of a 1.2 kW Polymer Electrolyte Membrane Fuel Cell (PEMFC) is developed and validated through a series of experiments. The experimental results have been obtained from a Nexa trademark PEM fuel cell power module under different load conditions. Based on this model, a simulator software package has been developed using the MATLAB {sup registered} and Simulink {sup registered} software and simulation results have been carried out. The proposed model exhibits good agreement with experiment results in steady-state and dynamic performance. (author)

  18. A Central Composite Face-Centered Design for Parameters Estimation of PEM Fuel Cell Electrochemical Model

    Directory of Open Access Journals (Sweden)

    Khaled MAMMAR

    2013-11-01

    Full Text Available In this paper, a new approach based on Experimental of design methodology (DoE is used to estimate the optimal of unknown model parameters proton exchange membrane fuel cell (PEMFC. This proposed approach combines the central composite face-centered (CCF and numerical PEMFC electrochemical. Simulation results obtained using electrochemical model help to predict the cell voltage in terms of inlet partial pressures of hydrogen and oxygen, stack temperature, and operating current. The value of the previous model and (CCF design methodology is used for parametric analysis of electrochemical model. Thus it is possible to evaluate the relative importance of each parameter to the simulation accuracy. However this methodology is able to define the exact values of the parameters from the manufacture data. It was tested for the BCS 500-W stack PEM Generator, a stack rated at 500 W, manufactured by American Company BCS Technologies FC.

  19. Vessel Cold-Ironing Using a Barge Mounted PEM Fuel Cell: Project Scoping and Feasibility.

    Energy Technology Data Exchange (ETDEWEB)

    Pratt, Joseph William; Harris, Aaron P

    2013-01-01

    A barge-mounted hydrogen-fueled proton exchange membrane (PEM) fuel cell system has the potential to reduce emissions and fossil fuel use of maritime vessels in and around ports. This study determines the technical feasibility of this concept and examines specific options on the U.S. West Coast for deployment practicality and potential for commercialization.The conceptual design of the system is found to be straightforward and technically feasible in several configurations corresponding to various power levels and run times.The most technically viable and commercially attractive deployment options were found to be powering container ships at berth at the Port of Tacoma and/or Seattle, powering tugs at anchorage near the Port of Oakland, and powering refrigerated containers on-board Hawaiian inter-island transport barges. Other attractive demonstration options were found at the Port of Seattle, the Suisun Bay Reserve Fleet, the California Maritime Academy, and an excursion vessel on the Ohio River.

  20. Final Report - Advanced Cathode Catalysts and Supports for PEM Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Debe, Mark

    2012-09-28

    The principal objectives of the program were development of a durable, low cost, high performance cathode electrode (catalyst and support), that is fully integrated into a fuel cell membrane electrode assembly with gas diffusion media, fabricated by high volume capable processes, and is able to meet or exceed the 2015 DOE targets. Work completed in this contract was an extension of the developments under three preceding cooperative agreements/grants Nos. DE-FC-02-97EE50473, DE-FC-99EE50582 and DE-FC36- 02AL67621 which investigated catalyzed membrane electrode assemblies for PEM fuel cells based on a fundamentally new, nanostructured thin film catalyst and support system, and demonstrated the feasibility for high volume manufacturability.

  1. High Temperature PEM Fuel Cell Performance Characterisation with CO and CO2 using Electrochemical Impedance Spectroscopy

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Vang, Jakob Rabjerg; Kær, Søren Knudsen

    2011-01-01

    In this work, extensive electrochemical impedance measurements have been conducted on a 45 cm2 BASF Celtec P2100 high temperature PEM MEA. The fuel cell performance has been examined subject to some of the poisoning effects experienced when running on a reformate gas. The impedance is measured...... at different temperatures, currents, and different content of CO, CO2 and H2 in the anode gas. The impedance spectrum at each operating point is fitted to an equivalent circuit and an analysis to identify the different mechanisms governing the impedance is performed. The trends observed, when varying...... the operating conditions under pure H2, generally show good agreement with results from the literature. When adding CO and CO2 to the anode gas the entire frequency spectrum is affected, and especially the measurements conducted at low temperatures and high CO concentrations reveal undesirable transient effects....

  2. Novel Catalytic Materials and Strategies for Hydrogen Production and Hydrogenation Reactions based on PEM Electrolysis

    OpenAIRE

    Ampurdanés Vilanova, Jordi

    2014-01-01

    La producción de hidrógeno, a gran escala, a partir de agua se ha convertido en un reto desde ya hace unos cuantos años. Así, una vía ecológica y eficiente para la generación de hidrógeno tiene que establecerse. Entre todas las posibilidades, electrólisis mediante la tecnología de membranas de intercambio de protones (PEM) es la técnica más prometedora para conseguir dicho propósito. Además, dicha aproximación también puede ser considerada para llevar a cabo otras reacciones electroquímicas c...

  3. Research and Development of a PEM Fuel Cell, Hydrogen Reformer, and Vehicle Refueling Facility

    Energy Technology Data Exchange (ETDEWEB)

    Edward F. Kiczek

    2007-08-31

    Air Products and Chemicals, Inc. has teamed with Plug Power, Inc. of Latham, NY, and the City of Las Vegas, NV, to develop, design, procure, install and operate an on-site hydrogen generation system, an alternative vehicle refueling system, and a stationary hydrogen fuel cell power plant, located in Las Vegas. The facility will become the benchmark for validating new natural gas-based hydrogen systems, PEM fuel cell power generation systems, and numerous new technologies for the safe and reliable delivery of hydrogen as a fuel to vehicles. Most important, this facility will serve as a demonstration of hydrogen as a safe and clean energy alternative. Las Vegas provides an excellent real-world performance and durability testing environment.

  4. A PEM fuel cell based on electrocatalyst and membrane materials modified by PANAM dendrimers

    Energy Technology Data Exchange (ETDEWEB)

    Ledesma-Garcia, J.; Chapman, T.W.; Godinez, L.A. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, Queretaro (Mexico)

    2008-10-15

    Due to its high energy conversion efficiency and low emission of pollutants, fuel-cell technology has been generally recognized as a key twenty-first century energy source. For polymer electrolyte membrane fuel cells (PEMFC), it has been found that platinum and its alloys exhibit the best electrocatalytic activity for oxygen reduction. The highest electrocatalytic activity of platinum and its alloys can be achieved when the particles are produced in the nanometer range. In this context, organic molecules have been adopted as templates to control the size of metal nanoparticles. Dendrimers, in particular, have shown promising properties for this application, and strategies that include direct adsorption, electrostatic attachment and covalent bonding have been developed for connecting metal-bearing dendrimers to conducting substrates. This paper reported on the preliminary results of a study that involved the construction and testing of a hydrogen-oxygen PEM fuel cell based on carbon-fiber-paper electrodes coated with hydroxyl-terminated dendrimers that encapsulated nanoparticles of platinum. This prototype cell also employed an ion exchange membrane comprising a cellulose acetate filter functionalized with proton-exchanging dendrimers. A proton-exchange membrane was prepared by binding duplex amine-carboxylate dendrimers to a cellulose-acetate support. With these dendrimer-based materials, a hydrogen-oxygen fuel cell was assembled and the performance compared with cells prepared with Nafion-based membranes. The voltage-current profiles and the power-density curves from the new cell provide encouragement to continue work with these dendrimer-modified materials. The paper discussed the experimental methods, with particular reference to materials; electrode preparation and characterization; proton-exchange membrane preparation; and PEM fuel-cell assembly and testing. It was concluded that the use of the dendritic macromolecules as supports for the nanoparticulate

  5. Validation of Perceptions of Empowerment in Midwifery Scale (PEMS in the Portuguese population

    Directory of Open Access Journals (Sweden)

    João José de Sousa Franco

    2012-10-01

    Full Text Available Introduction: Since when midwives are prominent in different socio-cultural contexts of individuals and populations associated with the control of women during pregnancy, childbirth and postpartum? In Portugal, the level of training of nurses in breastfeeding and obstetric has evolved, is considered the most advanced in the European context, and this would have posed new challenges for these professionals. Methodology: focusing on what the perception of empowerment that have specialized nurses in midwifery and maternal health in Portugal, it was decided to conduct this study, entitled "Validation of the Portuguese population scale - Perceptions of Empowerment in Midwifery Scale (PEMS" . We responded to the research question, what are the levels of empowerment of nurses in nursing and midwifery maternal health in Portugal? Objective: To determine the level of empowerment of nurses in nursing and midwifery maternal health in Portugal. In this study we used the quantitative method and descriptive. To accomplish this we proceeded to the implementation of a data collection instrument organized into two distinct parts. The first part allowed us to collect sociodemographic data and professional reviewers. In the second use "Perceptions of Empowerment in Midwifery Scale" (Matthews, Scott, and Gallagher, 2009, measuring tool we had to validate cross-culturally. The study presented here took samples of 309 Portuguese health nurses maternal obstetrical nurse specialists. Results: 'Perceptions of Empowerment in Midwifery Scale (PEMS' (Matthews, Scott, and Gallagher, 2009, presents a framework pentafatorial (effective management and interdisciplinary relationships, sustained and autonomous practice, professional communication and consent, recognition health team, training and education, which together account for 72.9% of the variance of the results. On average, nurses in maternal health nursing and midwifery have a low level of empowerment, the lowest level

  6. Design and fabrication of miniaturized PEM fuel cell combined microreactor with self-regulated hydrogen mechanism

    Science.gov (United States)

    Balakrishnan, A.; Frei, M.; Kerzenmacher, S.; Reinecke, H.; Mueller, C.

    2015-12-01

    In this work we present the design and fabrication of the miniaturized PEM fuel cell combined microreactor system with hydrogen regulation mechanism and testing of prototype microreactor. The system consists of two components (i) fuel cell component and (ii) microreactor component. The fuel cell component represents the miniaturized PEM fuel cell system (combination of screen printed fuel cell assembly and an on-board hydrogen storage medium). Hydrogen production based on catalytic hydrolysis of chemical hydride takes place in the microreactor component. The self-regulated hydrogen mechanism based on the gaseous hydrogen produced from the catalytic hydrolysis of sodium borohydride (NaBH4) gets accumulated as bubbles at the vicinity of the hydrophobic coated hydrogen exhaust holes. When the built up hydrogen bubbles pressure exceeds the burst pressure at the hydrogen exhaust holes the bubble collapses. This collapse causes a surge of fresh NaBH4 solution onto the catalyst surface leading to the removal of the reaction by-products formed at the active sites of the catalyst. The catalyst used in the system is platinum deposited on a base substrate. Nickel foam, carbon porous medium (CPM) and ceramic plate were selected as candidates for base substrate for developing a robust catalyst surface. For the first time the platinum layer fabricated by pulsed electrodeposition and dealloying (EPDD) technique is used for hydrolysis of NaBH4. The major advantages of such platinum catalyst layers are its high surface area and their mechanical stability. Prototype microreactor system with self-regulated hydrogen mechanism is demonstrated.

  7. Advanced Approaches to Greatly Reduce Hydrogen Gas Crossover Losses in PEM Electrolyzers Operating at High Pressures and Low Current Densities Project

    Data.gov (United States)

    National Aeronautics and Space Administration — ElectroChem proposes technology advances in its unique PEM IFF water electrolyzer design to meet the NASA requirement for an electrolyzer that will operate very...

  8. Modelling and characterisation of a PEM fuel cell; Modelisation et caracterisation d'une pile a combustible du type PEM

    Energy Technology Data Exchange (ETDEWEB)

    Friede, W.

    2003-08-01

    In this work, the behaviour of a fuel cell is described in regard of its integration into a power production system. Its use is difficult as a great number of operating parameters has to be controlled and internal behaviour has to be known. Therefore, the relations between the operating conditions and the electrical parameters are presented. The model describes the internal phenomena in the fuel cell while staying restricted enough to allow a fast resolution in stationary and transient operation. The fuel cell is divided into layers. Each layer consists of a different material. A mono-dimensional approach has been chosen. Following an axis that is perpendicular to the membrane surface, every layer is discretized into several elements. This work is dealing with a mathematical model of a single fuel cell, based on gas and water flow equations. The electrochemical reactions are described while taking into account the mutual influence with other values. The description of the cell impedance is of special interest. The model shows the evolution of electrical values as a function of operating conditions. The resolution of the equations using Matlab-Simulink software allows to localize the internal phenomena and to visualize the transient behaviour. Special attention is given to water management, which is one of the biggest challenges in operating low temperature fuel cells. The presentation of a test bench with a 500 W PEM fuel cell and stationary and transient measurements show the cell's performance and its sensibility to parameter changes. In particular, membrane resistance and impedance values are interpreted to get more information about the internal physical phenomena of the fuel cell. (author)

  9. Tropospheric Diagnostic Modeling Studies of PEM-Tropics B Field Data: Investigation of the HOx/NOx/O3 Photochemical System and its Coupling to Sulfur Chemistry

    Science.gov (United States)

    Davis, Douglas D.

    2001-01-01

    Over the time period of this NASA grant the PI has helped plan and execute the PEM-Tropics B field program. He has also helped organize and co-chair two data workshops which have focused on the detailed analysis of PEM-Tropics B data. His direct participation in these analyses has led to his involvement in 13 manuscripts, nine of which are in print, two in press, and two submitted. A complete list of papers is given.

  10. Parameter changes during gradual flooding of a PEM fuel cell through EIS studies; Cambio en parametros de una celda de combustible PEM durante inundacion gradual mediante estudios de EIS

    Energy Technology Data Exchange (ETDEWEB)

    Cano Castillo, Ulises; Cruz Manzo, Samuel; Arriaga Hurtado, Gerardo [Instituto de Investigaciones Electricas, Cuernavaca, Morelos (Mexico); Ortiz, Alondra; Orozco, German [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica S.C. (CIDETEQ) (Mexico)

    2008-07-01

    The gradual flooding of a single PEM fuel cell was produced and Electrochemical Impedance Spectroscopy (EIS) measurements were realized in order to follow changes of the fuel cell impedance parameters. These changes were followed by using two equivalent circuit models: one simple model of the Randles type accounting for cathode and anode interfaces and a more complex model based on distributed elements, more suitable for porous electrodes in order to include protonic resistance of the catalyst layers. [Spanish] La inundacion gradual de una monocelda de combustible tipo PEM fue estudiada empleando espectroscopia de impedancia electroquimica (EIS), con el proposito de seguir cambios en los parametros de impedancia de la celda. Estos cambios fueron estudiados utilizando dos circuitos equivalentes: un modelo simple de tipo Randles, el cual considerara las interfaces del catodo y del anodo, y un modelo mas complejo basado en elementos distribuidos, el cual fuera adecuado para electrodos porosos, a fin de incluir la resistencia protonica de las capas catalizadoras.

  11. A CFD study of hygro-thermal stresses distribution in tubular-shaped ambient air-breathing PEM micro fuel cell during regular cell operation

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2010-03-01

    Full Text Available The need for improved lifetime of air-breathing proton exchange membrane (PEM fuel cells for portable applications necessitates that the failure mechanisms be clearly understood and life prediction models be developed, so that new designs can be introduced to improve long-term performance. An operating air-breathing PEM fuel cell has varying local conditions of temperature, humidity. As a result of in the changes in temperature and moisture, the membrane, GDL and bipolar plates will all experience expansion and contraction. Because of the different thermal expansion and swelling coefficients between these materials, hygro-thermal stresses are introduced into the unit cell during operation. In addition, the non-uniform current and reactant flow distributions in the cell result in non-uniform temperature and moisture content of the cell which could in turn, potentially causing localized increases in the stress magnitudes, and this leads to mechanical damage, which can appear as through-the-thickness flaws or pinholes in the membrane, or delaminating between the polymer membrane and gas diffusion layers. Therefore, in order to acquire a complete understanding of these damage mechanisms in the membranes and gas diffusion layers, mechanical response under steady-state hygro-thermal stresses should be studied under real cell operation conditions. A three-dimensional, multi–phase, non-isothermal computational fluid dynamics model of a novel, tubular, ambient air-breathing, proton exchange membrane micro fuel cell has been developed and used to investigate the displacement, deformation, and stresses inside the whole cell, which developed during the cell operation due to the changes of temperature and relative humidity. The behaviour of the fuel cell during operation has been studied and investigated under real cell operating conditions. In addition to the new and complex geometry, a unique feature of the present model is to incorporate the effect of

  12. A CFD analysis on the effect of ambient conditions on the hygro-thermal stresses distribution in a planar ambient air-breathing PEM fuel cell

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2011-07-01

    Full Text Available The need for improved lifetime of air-breathing proton exchange membrane (PEM fuel cells for portable applications necessitates that the failure mechanisms be clearly understood and life prediction models be developed, so that new designs can be introduced to improve long-term performance. An operating air-breathing PEM fuel cell has varying local conditions of temperature and humidity. As a result of in the changes in temperature and moisture, the membrane, GDL and bipolar plates will all experience expansion and contraction. Because of the different thermal expansion and swelling coefficients between these materials, hygro-thermal stresses are introduced into the unit cell during operation. In addition, the non-uniform current and reactant flow distributions in the cell result in non-uniform temperature and moisture content of the cell which could in turn, potentially causing localized increases in the stress magnitudes, and this leads to mechanical damage, which can appear as through-the-thickness flaws or pinholes in the membrane, or delaminating between the polymer membrane and gas diffusion layers. Therefore, in order to acquire a complete understanding of these damage mechanisms in the membranes and gas diffusion layers, mechanical response under steady-state hygro-thermal stresses should be studied under real cell operation conditions. A three-dimensional, multi–phase, non-isothermal computational fluid dynamics model of a planar ambient air-breathing, proton exchange membrane fuel cell has been developed and used to study the effects of ambient conditions on the temperature distribution, displacement, deformation, and stresses inside the cell. The behaviour of the fuel cell during operation has been studied and investigated under real cell operating conditions. A unique feature of the present model is to incorporate the effect of mechanical, hygro and thermal stresses into actual three-dimensional fuel cell model. The results show

  13. Systems Analysis of Technologies for Energy Recovery from Waste. Part I. Gasification followed by Catalytic Combustion, PEM Fuel Cells and Solid Oxide Fuel Cells for Stationary Applications in Comparison with Incineration. Part - II. Catalytic combustion - Experimental part

    Energy Technology Data Exchange (ETDEWEB)

    Assefa, Getachew; Frostell, Bjoern [Royal Inst. of Technology, Stockholm (Sweden). Div. of Industrial Ecology; Jaeraas, Sven; Kusar, Henrik [Royal Inst. of Technology, Stockholm (Sweden). Div. of Chemical Technology

    2005-02-01

    This project is entitled 'Systems Analysis: Energy Recovery from waste, catalytic combustion in comparison with fuel cells and incineration'. Some of the technologies that are currently developed by researchers at the Royal Institute of Technology include catalytic combustion and fuel cells as downstream units in a gasification system. The aim of this project is to assess the energy turnover as well as the potential environmental impacts of biomass/waste-to-energy technologies. In second part of this project economic analyses of the technologies in general and catalytic combustion and fuel cell technologies in particular will be carried out. Four technology scenarios are studied: (1) Gasification followed by Low temperature fuel cells (Proton Exchange Membrane (PEM) fuel cells) (2) Gasification followed by high temperature fuel cells (Solid Oxide Fuel Cells (SOFC) (3) Gasification followed by catalytic combustion and (4) Incineration with energy recovery. The waste used as feedstock is an industrial waste containing parts of household waste, paper waste, wood residues and poly ethene. In the study compensatory district heating is produced by combustion of biofuel. The power used for running the processes in the scenarios will be supplied by the waste-to-energy technologies themselves while compensatory power is assumed to be produced from natural gas. The emissions from the system studied are classified and characterised using methodology from Life Cycle Assessment in to the following environmental impact categories: Global Warming Potential, Acidification Potential, Eutrophication Potential and finally Formation of Photochemical Oxidants. Looking at the result of the four technology chains in terms of the four impact categories with impact per GWh electricity produced as a unit of comparison and from the perspective of the rank each scenario has in all the four impact categories, SOFC appears to be the winner technology followed by PEM and CC as second

  14. Design and Control of High Temperature PEM Fuel Cell Systems using Methanol Reformers with Air or Liquid Heat Integration

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Kær, Søren Knudsen; Sahlin, Simon Lennart

    2013-01-01

    The present work describes the ongoing development of high temperature PEM fuel cell systems fuelled by steam reformed methanol. Various fuel cell system solutions exist, they mainly differ depending on the desired fuel used. High temperature PEM (HTPEM) fuel cells offer the possibility of using...... methanol is converted to a hydrogen rich gas with CO2 trace amounts of CO, the increased operating temperatures allow the fuel cell to tolerate much higher CO concentrations than Nafion-based membranes. The increased tolerance to CO also enables the use of reformer systems with less hydrogen cleaning steps...... liquid fuels such as methanol, due to the increased robustness of operating at higher temperatures (160-180oC). Using liquid fuels such as methanol removes the high volume demands of compressed hydrogen storages, simplifies refueling, and enables the use of existing fuel distribution systems. The liquid...

  15. Design and Control of High Temperature PEM Fuel Cell Systems using Methanol Reformers with Air or Liquid Heat Integration

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Sahlin, Simon Lennart; Justesen, Kristian Kjær

    The present work describes the ongoing development of high temperature PEM fuel cell systems fuelled by steam reformed methanol. Various fuel cell system solutions exist, they mainly differ depending on the desired fuel used. High temperature PEM (HTPEM) fuel cells offer the possibility of using...... methanol is converted to a hydrogen rich gas with CO2 trace amounts of CO, the increased operating temperatures allow the fuel cell to tolerate much higher CO concentrations than Nafion-based membranes. The increased tolerance to CO also enables the use of reformer systems with less hydrogen cleaning steps...... liquid fuels such as methanol, due to the increased robustness of operating at higher temperatures (160-180oC). Using liquid fuels such as methanol removes the high volume demands of compressed hydrogen storages, simplifies refueling, and enables the use of existing fuel distribution systems. The liquid...

  16. Commercial Optimization of a 100 kg/day PEM based Hydrogen Generator For Energy and Industrial Applications

    Energy Technology Data Exchange (ETDEWEB)

    Moulthrop, L.; Anderson, E.; Chow, O.; Friedland, R.; Maloney, T.; Schiller, M. [Hydrogen Technology Group of Proton Energy, a Distributed Energy Systems Company Wallingford, CT USA 06492 (United States)

    2006-07-01

    Commercial hydrogen generators using PEM water electrolysis are well proven, serving industrial applications worldwide in over 50 countries. Now, market and environmental requirements are converging to demand larger on-site hydrogen generators. North American liquid H{sub 2} shortages, increasing trucking costs, developing economies with no liquid infrastructure, utilities, and forklift fuel cell fueling applications are all working to increase market demand for commercial on-site H{sub 2} generation. These commercial applications may be satisfied by a 100 kg H{sub 2}/day module; this platform can be the pathway towards a 500 kg H{sub 2}/day generator desired for small fore-court hydrogen vehicle fueling stations. This paper discusses the steps necessary and activities already underway to develop a 100 to 500 kg H{sub 2}/day PEM hydrogen generator platform to meet commercial market cost targets and approach US DoE transportation fueling cost targets. (authors)

  17. The Effect of PFSA Membrane Compression on the Predicted Performance of a High Pressure PEM Electrolysis Cell

    DEFF Research Database (Denmark)

    Olesen, Anders Christian; Kær, Søren Knudsen

    the electrochemical behavior of an asymmetric pressurized PEM electrolysis cell In this work, a non-equilibrium formulation of the water uptake model by Kusoglu et al. [4] has been implemented in a two-dimensional, two-phase, multi-component and non-isothermal PEM electrolysis model. The non-equilibrium formulation......-called asymmetric setup, where only the cathode is operated at elevated pressures [2]. Under these conditions a large pressure difference forms across the polymer electrolyte membrane which mechanically compresses the polymer backbone and the anode electrode. While titanium felt has to be used as a gas diffusion...... of the water uptake model was chosen in order to account for interfacial transport kinetics between each fluid phase and the PFSA membrane. Besides modeling water uptake, the devised membrane model accounts for water transport through diffusion and electro-osmotic drag in the polymer phase, and hydraulic...

  18. Incidental detection of ascariasis worms on USG in a protein energy malnourished (PEM) child with abdominal pain.

    Science.gov (United States)

    Suthar, Pokhraj Prakashchandra; Doshi, Rajkumar Prakashbhai; Mehta, Chetan; Vadera, Khyati P

    2015-03-12

    A 10-year-old child presented with dull aching periumbilical abdominal pain for 15 days. The child was not gaining weight despite a good appetite. Physical examination of the child revealed grade-I protein energy malnourishment (PEM) according to IAP (Indian Academic of Paediatrics) classification. The rest of the systemic examination was normal. Routine blood investigation revealed anaemia with eosinophilia. Abdominal ultrasonography did not show any abnormality with curvilinear transducer (3.5-5 MHz), however, linear ultrasound transducer (7.5-12 MHz) with harmonic tissue imaging showed worms in the lumen of the small intestine with curling movement on real time scanning. Stool examination for the eggs of ascariasis was positive. The patient was treated with antihelminthic drugs. Dietary modification for the PEM was advised. After 3 months of treatment, the patient improved and stool examination for Ascaris was negative on follow-up.

  19. Experimental study on the two phase flow behavior in PEM fuel cell parallel channels with porous media inserts

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jixin [Mechanical and Aerospace Engineering, University of California, Irvine, Irvine, CA 92697-3975 (United States)

    2010-02-15

    In this study, the air-water two phase flow behavior in PEM fuel cell parallel channels with porous media inserts was experimentally investigated using a self-designed and manufactured transparent assembly. The visualization images of the two phase flow in channels with porous media inserts were presented and three patterns were summarized. Compared with the traditional hollow channel design, the novel configuration featured less severe two phase flow mal-distribution and self-adjustment to water amount in channels, although a higher pressure drop was introduced due to the porous media inserts. The dominant frequency of pressure drop signal was found to be a diagnostic tool for water behavior in channels. The novel flow channel design with porous media inserts may become a solution to the water management problem in PEM fuel cells. (author)

  20. Experimental study on the two phase flow behavior in PEM fuel cell parallel channels with porous media inserts

    Science.gov (United States)

    Chen, Jixin

    In this study, the air-water two phase flow behavior in PEM fuel cell parallel channels with porous media inserts was experimentally investigated using a self-designed and manufactured transparent assembly. The visualization images of the two phase flow in channels with porous media inserts were presented and three patterns were summarized. Compared with the traditional hollow channel design, the novel configuration featured less severe two phase flow mal-distribution and self-adjustment to water amount in channels, although a higher pressure drop was introduced due to the porous media inserts. The dominant frequency of pressure drop signal was found to be a diagnostic tool for water behavior in channels. The novel flow channel design with porous media inserts may become a solution to the water management problem in PEM fuel cells.

  1. Experimental study and comparison of various designs of gas flow fields to PEM fuel cells and cell stack performance

    Directory of Open Access Journals (Sweden)

    Hong eLiu

    2014-01-01

    Full Text Available In this study, a significant number of experimental tests to PEM fuel cells were conducted to investigate the effect of gas flow fields on fuel cell performance. Graphite plates with various flow field or flow channel designs, from literature survey and also novel designs by the authors, were used for the PEM fuel cell assembly. The fabricated fuel cells all have an effective membrane area of 23.5 cm2. The results showed that the serpentine flow channel design is still favorable, giving the best single fuel cell performance amongst all the studied flow channel designs. A novel symmetric serpentine flow field was proposed for relatively large size fuel cell application. Four fuel cell stacks each including four cells were assembled using different designs of serpentine flow channels. The output power performances of fuel cell stacks were compared and the novel symmetric serpentine flow field design is recommended for its very good performance.

  2. Draft, development and optimization of a fuel cell system for residential power generation with steam reformer; Entwurf, Aufbau und Optimierung eines PEM-Brennstoffzellensystems zur Hausenergieversorgung mit Dampfreformer

    Energy Technology Data Exchange (ETDEWEB)

    Brandt, H.

    2006-05-17

    The first development cycle of a residential power generation system is described. A steam reformer was chosen to produce hydrogen out of natural gas. After carbon monoxide purification with a preferential oxidation (PrOx) unit the hydrogen rich reformat gas is feed to the anode of the PEM-fuel cell, where due to the internal reaction with air oxygen form the cathode side water, heat and electricity is produced. Due to an incomplete conversion the anode off gas contains hydrogen and residual methane, which is feed to the burner of the steam reformer to reduce the needed amount of external fuel to heat the steam reformer. To develop the system the components are separately investigated and optimized in their construction or operation to meet the system requirements. After steady state and dynamic characterization of the components they were coupled one after another to build the system. To operate the system a system control was developed to operate and characterize this complex system. After characterization the system was analyzed for further optimization. During the development of the system inventions like a water cooled PrOx, an independent fuel cell controller or a burner for anodic off gas recirculation were made. The work gives a look into the interactions between the components and allows to understand the problems by coupling such components. (orig.)

  3. DOD Residential Proton Exchange Membrane (PEM) Fuel Cell Demonstration Program. Volume 1. Summary of the Fiscal Year 2001 Program

    Science.gov (United States)

    2004-02-01

    electricity, heat, and water There are several kinds of fuel cells, categorized by the type of electrolyte the re- action uses. This project used...Residential PEM Fuel Cell Demonstration Program.” Subse- quent funding in FY02 and FY03 has extended the Program, and has placed additional fuel...for large-scale Phos- phoric Acid Fuel Cells ( PAFC ), set the groundwork for program management. The release of a Broad Agency Announcement (BAA) for

  4. Analysis of transport phenomena and electrochemical reactions in a micro PEM fuel cell with nature inspired flow field design

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2015-01-01

    Full Text Available Micro-fuel cells are considered as promising electrochemical power sources in portable electronic devices. The presence of microelectromechanical system (MEMS technology makes it possible to manufacture the miniaturized fuel cell systems. The majority of research on micro-scale fuel cells is aimed at micro-power applications. Performance of micro-fuel cells are closely related to many factors, such as designs and operating conditions. CFD modeling and simulation for heat and mass transport in micro PEM fuel cells are being used extensively in researches and industrial applications to gain better understanding of the fundamental processes and to optimize the micro fuel cell designs before building a prototype for engineering application. In this research, full three-dimensional, non-isothermal computational fluid dynamics model of a micro proton exchange membrane (PEM fuel cell with nature inspired flow field designs has been developed. The design inspired from the existed biological fluid flow patterns in the leaf. This comprehensive model accounts for the major transport phenomena such as convective and diffusive heat and mass transfer, electrode kinetics, transport and phase-change mechanism of water, and potential fields in a micro PEM fuel cell. The model explains many interacting, complex electrochemical, and transport phenomena that cannot be studied experimentally.

  5. Analysis of transport phenomena and electrochemical reactions in a micro PEM fuel cell with serpentine gas flow channels

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2014-01-01

    Full Text Available Micro-fuel cells are considered as promising electrochemical power sources in portable electronic devices. The presence of microelectromechanical system (MEMS technology makes it possible to manufacture the miniaturized fuel cell systems. The majority of research on micro-scale fuel cells is aimed at micro-power applications. Performance of micro-fuel cells are closely related to many factors, such as designs and operating conditions. CFD modeling and simulation for heat and mass transport in micro PEM fuel cells are being used extensively in researches and industrial applications to gain better understanding of the fundamental processes and to optimize the micro fuel cell designs before building a prototype for engineering application. In this research, full three-dimensional, non-isothermal computational fluid dynamics model of a micro proton exchange membrane (PEM fuel cell with serpentine gas flow channels has been developed. This comprehensive model accounts for the major transport phenomena such as convective and diffusive heat and mass transfer, electrode kinetics, transport and phase-change mechanism of water, and potential fields in a micro PEM fuel cell. The model explains many interacting, complex electrochemical, and transport phenomena that cannot be studied experimentally.

  6. Effect of placing different obstacles in flow fields on performance of a PEM fuel cell: numerical investigation and experimental comparison

    Science.gov (United States)

    Khazaee, I.

    2013-09-01

    In this study a complete two-dimensional model for proton exchange membrane (PEM) fuel cells was used to investigate the effect of using different obstacles on the performances, current density and gas concentration for different aspect ratios (ARs). The proposed model is a full cell model, which includes all the parts of the PEM fuel cell, flow channels, gas diffusion electrodes, catalyst layers and the membrane. Also a series of tests are carried out to investigate and validate the numerical results of the polarization curve under the normal conditions. A PEM fuel cell with 25 cm2 active area and Nafion 117 membrane with 4 mg Pt/cm2 for the anode and cathode is employed as a membrane electrode assembly. The results show that the predicted polarization curves by using this model are in good agreement with the experimental results. Also the results show that the local current density reduces more obviously at a higher overpotential than at a lower overpotential because of the more obvious reflection phenomena in the downstream region. At lower operating voltage conditions, the overall cell performance decreases as the AR decreases.

  7. A CFD analysis of transport phenomena and electrochemical reactions in a tubular-shaped PEM fuel cell

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2013-01-01

    Full Text Available A fuel cell is most interesting new power source because it solves not only the environment problem but also natural resource exhaustion problem. CFD modeling and simulation for heat and mass transport in PEM fuel cells are being used extensively in researches and industrial applications to gain better understanding of the fundamental processes and to optimize fuel cell designs before building a prototype for engineering application. In this research, full three-dimensional, non-isothermal computational fluid dynamics model of a tubular-shaped proton exchange membrane (PEM fuel cell has been developed. This comprehensive model accounts for the major transport phenomena such as convective and diffusive heat and mass transfer, electrode kinetics, transport and phase-change mechanism of water, and potential fields in a tubular-shaped PEM fuel cell. The model explains many interacting, complex electrochemical, and transport phenomena that cannot be studied experimentally. Three-dimensional results of the species profiles, temperature distribution, potential distribution, and local current density distribution are presented and analysed, with the focus on the physical insight and fundamental understanding.

  8. A CFD analysis of transport phenomena and electrochemical reactions in a tubular-shaped PEM fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Sadiq Al-Baghdadi, Maher A.R. [Fuel Cell Research Center, International Energy and Environment Foundation, Al-Najaf, P.O.Box 39 (Iraq)

    2013-07-01

    A fuel cell is most interesting new power source because it solves not only the environment problem but also natural resource exhaustion problem. CFD modeling and simulation for heat and mass transport in PEM fuel cells are being used extensively in researches and industrial applications to gain better understanding of the fundamental processes and to optimize fuel cell designs before building a prototype for engineering application. In this research, full three-dimensional, non-isothermal computational fluid dynamics model of a tubular-shaped proton exchange membrane (PEM) fuel cell has been developed. This comprehensive model accounts for the major transport phenomena such as convective and diffusive heat and mass transfer, electrode kinetics, transport and phase-change mechanism of water, and potential fields in a tubular-shaped PEM fuel cell. The model explains many interacting, complex electrochemical, and transport phenomena that cannot be studied experimentally. Three-dimensional results of the species profiles, temperature distribution, potential distribution, and local current density distribution are presented and analysed, with the focus on the physical insight and fundamental understanding.

  9. Characteristics of liquid water removal from the gas diffusion layer by reactant flow in a PEM fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Jiao, K.; Park, J.; Li, X. [Waterloo Univ., ON (Canada). Dept. of Mechanical and Mechatronics Engineering

    2008-07-01

    Water in proton exchange membrane (PEM) fuel cells is accumulated in the gas diffusion layer (GDL) and removed by the static pressure gradient caused by the fast reactant flow in the flow channel. Reactants can leak into the neighbouring channels via the porous GDL and inhibit the removal of liquid water. This study examined the characteristics of liquid water removal from the GDL by measuring unsteady pressure drop in a PEM fuel cell in which the GDL was initially wetted with liquid water. GDL thickness was controlled by inserting metal shims between the fuel cell plates. The experiment showed that the amount of pressure drop is inversely proportional to GDL thickness. Thicker GDLs with higher porosity levels increased cross flow. Liquid water removal was also influenced by the change of inlet Reynolds number, which demonstrated that air flow rates must be high enough for efficient water removal. Various GDL porosities and permeabilities were calculated, and their influence on the characteristics of liquid water removal were evaluated. A transparent flow channel design was used to visualize water movement in the GDL. It was concluded that the effects of cross flow and GDL compression levels should be considered in the analysis and design of PEM fuel cells. 23 refs., 8 figs.

  10. Analytical Investigation and Improvement of Performance of a Proton Exchange Membrane (Pem Fuel Cell in Mobile Applications

    Directory of Open Access Journals (Sweden)

    Khazaee I.

    2015-05-01

    Full Text Available In this study, the performance of a proton exchange membrane fuel cell in mobile applications is investigated analytically. At present the main use and advantages of fuel cells impact particularly strongly on mobile applications such as vehicles, mobile computers and mobile telephones. Some external parameters such as the cell temperature (Tcell , operating pressure of gases (P and air stoichiometry (λair affect the performance and voltage losses in the PEM fuel cell. Because of the existence of many theoretical, empirical and semi-empirical models of the PEM fuel cell, it is necessary to compare the accuracy of these models. But theoretical models that are obtained from thermodynamic and electrochemical approach, are very exact but complex, so it would be easier to use the empirical and smi-empirical models in order to forecast the fuel cell system performance in many applications such as mobile applications. The main purpose of this study is to obtain the semi-empirical relation of a PEM fuel cell with the least voltage losses. Also, the results are compared with the existing experimental results in the literature and a good agreement is seen.

  11. Experimental study of humidity changes on the performance of an elliptical single four-channel PEM fuel cell

    Science.gov (United States)

    Gholizadeh, Mohammad; Ghazikhani, Mohsen; Khazaee, Iman

    2017-01-01

    Humidity and humidification in a proton exchange membrane fuel cells (PEM) can significantly affect the performance of these energy generating devices. Since protons (H+) needs to be accompanied by water molecules to pass from the anode side to the cathode side, the PEM fuel cell membrane should be sufficiently wet. Low or high amount of water in the membrane can interrupt the flow of protons and thus reduce the efficiency of the fuel cell. In this context, several experimental studies and modeling have been carried out on PEM fuel cell and interesting results have been achieved. In this paper, the humidity and flow rate of gas in the anode and cathode are modified to examine its effect on fuel cell performance. The results show that the effect of humidity changing in the anode side is greater than that of the cathode so that at zero humidity of anode and 70 % humidity of the cathode, a maximum current flow of 0.512 A/cm2 for 0.12 V was obtained. However, at 70 % anode humidity and zero cathode humidity, a maximum flow of 0.86 A/cm2 for 0.13 V was obtained.

  12. Analysis of liquid water formation in polymer electrolyte membrane (PEM) fuel cell flow fields with a dry cathode supply

    Science.gov (United States)

    Gößling, Sönke; Klages, Merle; Haußmann, Jan; Beckhaus, Peter; Messerschmidt, Matthias; Arlt, Tobias; Kardjilov, Nikolay; Manke, Ingo; Scholta, Joachim; Heinzel, Angelika

    2016-02-01

    PEM fuel cells can be operated within a wide range of different operating conditions. In this paper, the special case of operating a PEM fuel cell with a dry cathode supply and without external humidification of the cathode, is considered. A deeper understanding of the water management in the cells is essential for choosing the optimal operation strategy for a specific system. In this study a theoretical model is presented which aims to predict the location in the flow field at which liquid water forms at the cathode. It is validated with neutron images of a PEM fuel cell visualizing the locations at which liquid water forms in the fuel cell flow field channels. It is shown that the inclusion of the GDL diffusion resistance in the model is essential to describe the liquid water formation process inside the fuel cell. Good agreement of model predictions and measurement results has been achieved. While the model has been developed and validated especially for the operation with a dry cathode supply, the model is also applicable to fuel cells with a humidified cathode stream.

  13. HyLIFT-0. 'Development and benchmarking of a 1st gen. HT-PEM/Li-lon hybrid motive power system for forklifts'. Slutrapport

    Energy Technology Data Exchange (ETDEWEB)

    Poulsen, Karsten (H2 Logic A/S, Herning (Denmark)); Elkjaer Toennesen, A. (Teknologisk Institut, AArhus (Denmark)); Torrendrup, C. (Lithium Balance A/S, Ishoej (Denmark)); Sangers, A. (Grundfos DK A/S, Bjerringbro (Denmark)); Junge, S. (Atlet Danmark A/S, Engesvang (Denmark))

    2010-04-15

    In the HyLIFT-0 project a HT-PEM/Li-Ion hybrid system for a forklift was developed and built. The system has been benchmark'et and tested both at H2 Logic, in a test bench at the Teknologisk Institut and by an end user, Grene A/S, who already has a hydrogen hybrid vehicle in service with LT-PEM system. The HT-PEM/Li-Ion system is based on a 1 kW SerEnergy fuel cell, with a 2.5 kWh Li-Ion battery pack and the newly developed BMS. Both Fuel cell systems were measured in the test bench at Teknologisk Institut. The conclusions are not fully accurate because there are many factors influencing such as the HT-PEM system not being fully optimized. The benchmark at Grene, showed that the heat up time is critical for the vehicle, but once it is in operation, there are no difference to the LT-PEM system, either in experienced performance or in user experience. The purpose of HyLIFT-0 project is met since the measurements and the benchmark has revealed the technology's advantages and disadvantages. Above all the conclusion is that HT-PEM/Li-Ion hybrid fuel cell system at the present stage of development is not a disruptive technology compared to known LT-PEM systems. There are numerous advantages of the system, but there are also some disadvantages, doing that, overall, it is not a usable technology in forklifts - it is especially the long start-up time of up to 45 minutes that is unacceptable for the fork lifter user; the user wants to have immediate maximum output and the battery cannot handle this during the time it lasts until the HT-PEM fuel cell is warm and producing power. The HT-PEM/Li-Ion system is relatively simple to build and it saves a number of components compared to the LT-PEM system, but the economic advantage of this is counterbalanced by the fuel cell being rather expensive and furthermore it has a relatively low efficiency. This will probably change over time when the technology completed development and volume increase. (LN)

  14. HyLIFT-0. 'Development and benchmarking of a 1st gen. HT-PEM/Li-lon hybrid motive power system for forklifts'. Slutrapport

    Energy Technology Data Exchange (ETDEWEB)

    Poulsen, Karsten (H2 Logic A/S, Herning (Denmark)); Elkjaer Toennesen, A. (Teknologisk Institut, AArhus (Denmark)); Torrendrup, C. (Lithium Balance A/S, Ishoej (Denmark)); Sangers, A. (Grundfos DK A/S, Bjerringbro (Denmark)); Junge, S. (Atlet Danmark A/S, Engesvang (Denmark))

    2010-04-15

    In the HyLIFT-0 project a HT-PEM/Li-Ion hybrid system for a forklift was developed and built. The system has been benchmark'et and tested both at H2 Logic, in a test bench at the Teknologisk Institut and by an end user, Grene A/S, who already has a hydrogen hybrid vehicle in service with LT-PEM system. The HT-PEM/Li-Ion system is based on a 1 kW SerEnergy fuel cell, with a 2.5 kWh Li-Ion battery pack and the newly developed BMS. Both Fuel cell systems were measured in the test bench at Teknologisk Institut. The conclusions are not fully accurate because there are many factors influencing such as the HT-PEM system not being fully optimized. The benchmark at Grene, showed that the heat up time is critical for the vehicle, but once it is in operation, there are no difference to the LT-PEM system, either in experienced performance or in user experience. The purpose of HyLIFT-0 project is met since the measurements and the benchmark has revealed the technology's advantages and disadvantages. Above all the conclusion is that HT-PEM/Li-Ion hybrid fuel cell system at the present stage of development is not a disruptive technology compared to known LT-PEM systems. There are numerous advantages of the system, but there are also some disadvantages, doing that, overall, it is not a usable technology in forklifts - it is especially the long start-up time of up to 45 minutes that is unacceptable for the fork lifter user; the user wants to have immediate maximum output and the battery cannot handle this during the time it lasts until the HT-PEM fuel cell is warm and producing power. The HT-PEM/Li-Ion system is relatively simple to build and it saves a number of components compared to the LT-PEM system, but the economic advantage of this is counterbalanced by the fuel cell being rather expensive and furthermore it has a relatively low efficiency. This will probably change over time when the technology completed development and volume increase. (LN)

  15. Integration Process for the Habitat Demonstration Unit

    Science.gov (United States)

    Gill, Tracy; Merbitz, Jerad; Kennedy, Kriss; Tn, Terry; Toups, Larry; Howe, A. Scott; Smitherman, David

    2011-01-01

    The Habitat Demonstration Unit (HDU) is an experimental exploration habitat technology and architecture test platform designed for analog demonstration activities. The HDU previously served as a test bed for testing technologies and sub-systems in a terrestrial surface environment. in 2010 in the Pressurized Excursion Module (PEM) configuration. Due to the amount of work involved to make the HDU project successful, the HDU project has required a team to integrate a variety of contributions from NASA centers and outside collaborators The size of the team and number of systems involved With the HDU makes Integration a complicated process. However, because the HDU shell manufacturing is complete, the team has a head start on FY--11 integration activities and can focus on integrating upgrades to existing systems as well as integrating new additions. To complete the development of the FY-11 HDU from conception to rollout for operations in July 2011, a cohesive integration strategy has been developed to integrate the various systems of HDU and the payloads. The highlighted HDU work for FY-11 will focus on performing upgrades to the PEM configuration, adding the X-Hab as a second level, adding a new porch providing the astronauts a larger work area outside the HDU for EVA preparations, and adding a Hygiene module. Together these upgrades result in a prototype configuration of the Deep Space Habitat (DSH), an element under evaluation by NASA's Human Exploration Framework Team (HEFT) Scheduled activates include early fit-checks and the utilization of a Habitat avionics test bed prior to installation into HDU. A coordinated effort to utilize modeling and simulation systems has aided in design and integration concept development. Modeling tools have been effective in hardware systems layout, cable routing, sub-system interface length estimation and human factors analysis. Decision processes on integration and use of all new subsystems will be defined early in the project to

  16. WaterTransport in PEM Fuel Cells: Advanced Modeling, Material Selection, Testing and Design Optimization

    Energy Technology Data Exchange (ETDEWEB)

    J. Vernon Cole; Abhra Roy; Ashok Damle; Hari Dahr; Sanjiv Kumar; Kunal Jain; Ned Djilai

    2012-10-02

    Water management in Proton Exchange Membrane, PEM, Fuel Cells is challenging because of the inherent conflicts between the requirements for efficient low and high power operation. Particularly at low powers, adequate water must be supplied to sufficiently humidify the membrane or protons will not move through it adequately and resistance losses will decrease the cell efficiency. At high power density operation, more water is produced at the cathode than is necessary for membrane hydration. This excess water must be removed effectively or it will accumulate in the Gas Diffusion Layers, GDLs, between the gas channels and catalysts, blocking diffusion paths for reactants to reach the catalysts and potentially flooding the electrode. As power density of the cells is increased, the challenges arising from water management are expected to become more difficult to overcome simply due to the increased rate of liquid water generation relative to fuel cell volume. Thus, effectively addressing water management based issues is a key challenge in successful application of PEMFC systems. In this project, CFDRC and our partners used a combination of experimental characterization, controlled experimental studies of important processes governing how water moves through the fuel cell materials, and detailed models and simulations to improve understanding of water management in operating hydrogen PEM fuel cells. The characterization studies provided key data that is used as inputs to all state-of-the-art models for commercially important GDL materials. Experimental studies and microscopic scale models of how water moves through the GDLs showed that the water follows preferential paths, not branching like a river, as it moves toward the surface of the material. Experimental studies and detailed models of water and airflow in fuel cells channels demonstrated that such models can be used as an effective design tool to reduce operating pressure drop in the channels and the associated

  17. Managing Reverse Logistics or Reversing Logistics Management?

    OpenAIRE

    Brito, Marisa

    2004-01-01

    textabstractIn the past, supply chains were busy fine-tuning the logistics from raw material to the end customer. Today an increasing flow of products is going back in the chain. Thus, companies have to manage reverse logistics as well.This thesis contributes to a better understanding of reverse logistics. The thesis brings insights on reverse logistics decision-making and it lays down theoretical principles for reverse logistics as a research field.In particular it puts together a framework ...

  18. Prediction of deformation and hygro-thermal stresses distribution in PEM fuel cell vehicle using three-dimensional CFD model

    Energy Technology Data Exchange (ETDEWEB)

    Sadiq Al-Baghdadi, Maher A.R. [Fuel Cell Research Center, International Energy & Environment Foundation, Al-Najaf, P.O.Box 39 (Iraq)

    2012-07-01

    Durability is one of the most critical remaining issues impeding successful commercialization of broad PEM fuel cell transportation energy applications. Automotive fuel cells are likely to operate with neat hydrogen under load-following or load-levelled modes and be expected to withstand variations in environmental conditions, particularly in the context of temperature and atmospheric composition. In addition, they are also required to survive over the course of their expected operational lifetimes i.e., around 5,500 hrs, while undergoing as many as 30,000 startup/shutdown cycles. The damage mechanisms in a PEM fuel cell are accelerated by mechanical stresses arising during fuel cell assembly (bolt assembling), and the stresses arise during fuel cell running, because it consists of the materials with different thermal expansion and swelling coefficients. Therefore, in order to acquire a complete understanding of the damage mechanisms in the membrane, mechanical response under steady-state hygro-thermal stresses should be studied under real cell operating conditions and in real cell geometry (three-dimensional). In this work, full three-dimensional, non-isothermal computational fluid dynamics model of a PEM fuel cell has been developed to simulate the stresses inside the PEM fuel cell, which are occurring during fuel cell assembly (bolt assembling), and the stresses arise during fuel cell running due to the changes of temperature and relative humidity. A unique feature of the present model is to incorporate the effect of hygro and thermal stresses into actual three-dimensional fuel cell model. In addition, the temperature and humidity dependent material properties are utilize in the simulation for the membrane. The model is shown to be able to understand the many interacting, complex electrochemical, transport phenomena, and stresses distribution that have limited experimental data. This model is used to study and analyse the effect of operating parameters on the

  19. Prediction of deformation and hygro-thermal stresses distribution in PEM fuel cell vehicle using three-dimensional CFD model

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2012-01-01

    Full Text Available Durability is one of the most critical remaining issues impeding successful commercialization of broad PEM fuel cell transportation energy applications. Automotive fuel cells are likely to operate with neat hydrogen under load-following or load-levelled modes and be expected to withstand variations in environmental conditions, particularly in the context of temperature and atmospheric composition. In addition, they are also required to survive over the course of their expected operational lifetimes i.e., around 5,500 hrs, while undergoing as many as 30,000 startup/shutdown cycles. The damage mechanisms in a PEM fuel cell are accelerated by mechanical stresses arising during fuel cell assembly (bolt assembling, and the stresses arise during fuel cell running, because it consists of the materials with different thermal expansion and swelling coefficients. Therefore, in order to acquire a complete understanding of the damage mechanisms in the membrane, mechanical response under steady-state hygro-thermal stresses should be studied under real cell operating conditions and in real cell geometry (three-dimensional. In this work, full three-dimensional, non-isothermal computational fluid dynamics model of a PEM fuel cell has been developed to simulate the stresses inside the PEM fuel cell, which are occurring during fuel cell assembly (bolt assembling, and the stresses arise during fuel cell running due to the changes of temperature and relative humidity. A unique feature of the present model is to incorporate the effect of hygro and thermal stresses into actual three-dimensional fuel cell model. In addition, the temperature and humidity dependent material properties are utilize in the simulation for the membrane. The model is shown to be able to understand the many interacting, complex electrochemical, transport phenomena, and stresses distribution that have limited experimental data. This model is used to study and analyse the effect of operating

  20. Effect of channel geometrical configuration on the pressure distribution and stress failure in a running PEM fuel cell

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2017-01-01

    Full Text Available Proton Exchange membrane (PEM fuel cells are still undergoing intense development, and the combination of new and optimized materials, improved product development, novel architectures, more efficient transport processes, and design optimization and integration are expected to lead to major gains in performance, efficiency, durability, reliability, manufacturability and cost-effectiveness. PEM fuel cell assembly pressure is known to cause large strains in the cell components. All components compression occurs during the assembly process of the cell, but also during fuel cell operation due to membrane swelling when absorbs water and cell materials expansion due to heat generating in catalyst layers. Additionally, the repetitive channel-rib pattern of the bipolar plates results in a highly inhomogeneous compressive load, so that while large strains are produced under the rib, the region under the channels remains approximately at its initial uncompressed state. This leads to significant spatial variations in GDL thickness and porosity distributions, as well as in electrical and thermal bulk conductivities and contact resistances (both at the ribe-GDL and membrane-GDL interfaces. These changes affect the rates of mass, charge, and heat transport through the GDL, thus impacting fuel cell performance and lifetime. In this study, computational fluid dynamics (CFD model of a PEM fuel cell has been developed to simulate the pressure distribution inside the cell, which are occurring during fuel cell assembly (bolt assembling, and membrane swelling and cell materials expansion during fuel cell running due to the changes of temperature and relative humidity. The PEM fuel cell model simulated includes the following components; two bi-polar plates, two GDLs, and, an MEA (membrane plus two CLs. This model is used to study and analyse the effect of channel geometrical configuration on the mechanical behaviour of the PEM fuel cell components. The analysis

  1. Designing novel reversible BCD adder and parallel adder/subtraction using new reversible logic gates

    Science.gov (United States)

    Zhou, Rigui; Zhang, Manqun; Wu, Qian; Shi, Yang

    2012-10-01

    Reversible logic has received much attention in recent years when calculation with minimum energy consumption is considered. Especially, interest is sparked in reversible logic by its applications in some technologies, such as quantum computing, low-power CMOS design, optical information processing and nanotechnology. This article proposes two new reversible logic gates, ZRQ and NC. The first gate ZRQ not only implements all Boolean functions but also can be used to design optimised adder/subtraction architectures. One of the prominent functionalities of the proposed ZRQ gate is that it can work by itself as a reversible full adder/subtraction unit. The second gate NC can complete overflow detection logic of Binary Coded Decimal (BCD) adder. This article proposes two approaches to design novel reversible BCD adder using new reversible gates. A comparative result which is presented shows that the proposed designs are more optimised in terms of number of gates, garbage outputs, quantum costs and unit delays than the existing designs.

  2. Measurements of nitric acid, carboxylic acids, and selected aerosol species for the NASA/GTE Pacific Mission - West (PEM-WEST)

    Science.gov (United States)

    Talbot, Robert W.; Dibb, Jack E.

    1993-01-01

    The research investigation funded through this grant to the University of New Hampshire was performed during a major field expedition conducted by the NASA Tropospheric Chemistry Program. The NASA Global Tropospheric Experiment (GTE) executed an airborne science mission (PEM-WEST A) aboard the NASA Ames DC-8 over the Pacific Ocean during Sep./Oct. 1981. The atmosphere over the central Pacific Ocean is the only major region in the Northern Hemisphere that is relatively free from direct anthropogenic influence. Thus, this environment is ideally suited to study the natural biogeochemical cycles of carbon, nitrogen, ozone, sulfur, and aerosols without serious confounding problems related to anthropogenic emissions. Asian sources account for about 17 percent of the global budgets of nitrogen oxides (NO(x)) and sulfur dioxide (SO2). The Pacific Rim region therefore provides the opportunity to study the anthropogenic impact on natural atmospheric chemical cycles. The PEM-WEST A flights were focused on contrasting the chemistry of 'clean' air over the central Pacific with anthropogenically impacted air advected off the Asian continent. The principal objectives of PEM-WEST A were to investigate the atmospheric chemistry of ozone (O3) and its precursors, and to study important aspects of the atmospheric sulfur cycle over the western Pacific Ocean. Measurements conducted by the University of New Hampshire contributed directly to both of these objectives. Subsequent PEM-WEST field missions are planned by GTE in the mid-1990's to contrast atmospheric chemistry documented during PEM-WEST A with other time periods. This report presents preliminary findings from the PEM-WEST A field mission. Data interpretation is currently ongoing with the goal of manuscript submission of scientific results to a special issue of the Journal of Geophysical Research-Atmospheres in Feb. 1994. The reader is strongly encouraged to review this suite of profession articles to appreciate the overall

  3. Background {sup 18}F-FDG uptake in positron emission mammography (PEM): Correlation with mammographic density and background parenchymal enhancement in breast MRI

    Energy Technology Data Exchange (ETDEWEB)

    Koo, Hye Ryoung, E-mail: huilings@hanmail.net [Department of Radiology, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul 110-744 (Korea, Republic of); Moon, Woo Kyung, E-mail: moonwk@snu.ac.kr [Department of Radiology, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul 110-744 (Korea, Republic of); Chun, In Kook, E-mail: inkook.chun@gmail.com [Department of Nuclear Medicine, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul 110-744 (Korea, Republic of); Eo, Jae Seon, E-mail: jaeseon76@gmail.com [Department of Nuclear Medicine, Korea University Guro Hospital, 148 Gurodongro, Guro-gu, Seoul 152-703 (Korea, Republic of); Jeyanth, Joseph Xavier, E-mail: jeyanth7@snu.ac.kr [Department of Radiology, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul 110-744 (Korea, Republic of); Chang, Jung Min, E-mail: imchangjm@gmail.com [Department of Radiology, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul 110-744 (Korea, Republic of); Cho, Nariya, E-mail: river7774@gmail.com [Department of Radiology, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul 110-744 (Korea, Republic of); Kang, Keon Wook, E-mail: kangkw@snu.ac.kr [Department of Nuclear Medicine, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul 110-744 (Korea, Republic of)

    2013-10-01

    We aimed to determine whether background {sup 18}F-FDG uptake in positron emission mammography (PEM) was related to mammographic density or background parenchymal enhancement in breast MRI. Methods: We studied a total of 52 patients (mean age, 50.9 years, 26 premenopausal, 26 postmenopausal) with newly diagnosed breast cancer who underwent {sup 18}F-FDG PEM (positron emission mammography), conventional mammography and breast MRI. The background mean {sup 18}F-FDG uptake value on PEM was obtained by drawing a user-defined region of interest (ROI) in a normal area of the contralateral breast. We reviewed the mammography retrospectively for overall breast density of contralateral breast according to the four-point scale (grade 1–4) of the Breast Imaging Reporting and Data System (BI-RADS) classification. The background parenchymal enhancement of breast MRI was classified as minimal, mild, moderate, or marked. All imaging findings were interpreted by two readers in consensus without knowledge of image findings of other modalities. Results: Multiple linear regression analysis revealed a significant correlation between background {sup 18}F-FDG uptake on PEM and mammographic density after adjustment for age and menopausal status (P < 0.01), but not between background {sup 18}F-FDG uptake on PEM and background parenchymal enhancement on MRI. Conclusion: Background {sup 18}F-FDG uptake on PEM significantly increases as mammographic density increases. Background parenchymal enhancement in breast MRI was not an independent predictor of the background {sup 18}F-FDG uptake on PEM unlike mammographic density.

  4. Performance comparison of dual-head PEM scanner by Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Mengdie; Hu, Guangshu; Zhang, Hui, E-mail: hzhang@mail.tsinghua.edu.cn

    2014-02-11

    To evaluate the effects of the flat panel dimension on the overall performance qualitatively and quantitatively, the performance of two dual-head Positron Emission Mammography (PEM) cameras with different configurations, the 3×3 modules system and the 1×3 modules system, has been compared, using Monte Carlo simulation based on the Geant4 Application for Tomographic Emission (GATE) open source software. Besides traditional evaluation methods, imaging capability in terms of spatial resolution and lesion detectability have been integrated into the evaluation. Compared with the 3×3 modules system, the 1×3 modules system produces higher spatial resolution along the direction of the 1-module side but lower resolution along the other direction. No significant difference in small and weak lesion visualization has been noted between two systems. In addition, the slight disadvantage in semi-quantification of the 1×3 modules system can be further compensated by other methods such as increasing the imaging time while still in a practically acceptable range.

  5. DESIGN AND IMPLEMENTATION OF A PEM FUEL CELL EMULATOR FOR STATIC AND DYNAMIC BEHAVIOR

    Directory of Open Access Journals (Sweden)

    CARLOS ANDRÉS RAMOS-PAJA

    2011-01-01

    Full Text Available Este artículo presenta el diseño, implementación y validación experimental de un emulador controlado digitalmente de pilas de combustible con membrana de intercambio protónico (PEM, tanto para comportamiento estático como dinámico, el cual es fácil de usar y proporciona autonomía y portabilidad a bajo costo. El emulador permite la evaluación de sistemas de potencia y estrategias de control en sistemas basados en pilas de combustible. Para la implementación del emulador se seleccionó, ajustó y validó un modelo matemático apropiado. El modelo es procesado digitalmente en el emulador, el cual genera el comportamiento eléctrico apropiado a la carga. La etapa de potencia fue implementada usando un convertidor DC/DC conmutado de dos inductores, controlado directamente con el sistema de procesamiento digital. El artículo presenta el esquema eléctrico y diagrama de bloques de la etapa de potencia, y el comportamiento del emulador es ilustrado con resultados de simulación. Finalmente, el emulador es validado experimentalmente.

  6. A complete two-phase model of a porous cathode of a PEM fuel cell

    Science.gov (United States)

    Hwang, J. J.

    This paper has developed a complete two-phase model of a proton exchange membrane (PEM) fuel cell by considering fluid flow, heat transfer and current simultaneously. In fluid flow, two momentum equations governing separately the gaseous-mixture velocity (u g) and the liquid-water velocity (u w) illustrate the behaviors of the two-phase flow in a porous electrode. Correlations for the capillary pressure and the saturation level connect the above two-fluid transports. In heat transfer, a local thermal non-equilibrium (LTNE) model accounting for intrinsic heat transfer between the reactant fluids and the solid matrices depicts the interactions between the reactant-fluid temperature (T f) and the solid-matrix temperature (T s). The irreversibility heating due to electrochemical reactions, Joule heating arising from Ohmic resistance, and latent heat of water condensation/evaporation are considered in the present non-isothermal model. In current, Ohm's law is applied to yield the conservations in ionic current (i m) and electronic current (i s) in the catalyst layer. The Butler-Volmer correlation describes the relation of the potential difference (overpotential) and the transfer current between the electrolyte (such as Nafion™) and the catalyst (such as Pt/C).

  7. Ice formation in PEM fuel cells operated isothermally at sub-freezing temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Mukundan, Rangachary [Los Alamos National Laboratory; Luhan, Roger W [Los Alamos National Laboratory; Davey, John R [Los Alamos National Laboratory; Spendelow, Jacob S [Los Alamos National Laboratory; Borup, Rodney L [Los Alamos National Laboratory; Hussey, Daniel S [NIST; Jacobson, David L [NIST; Arif, Muhammad [NIST

    2009-01-01

    The effect of MEA and GDL structure and composition on the performance of single-PEM fuel cells operated isothermally at subfreezing temperatures is presented. The cell performance and durability are not only dependent on the MEA/GDL materials used but also on their interfaces. When a cell is operated isothermally at sub-freezing temperatures in constant current mode, the water formation due to the current density initially hydrates the membrane/ionomer and then forms ice in the catalyst layer/GDL. An increase in high frequency resistance was also observed in certain MEAs where there is a possibility of ice formation between the catalyst layer and GDL leading to a loss in contact area. The total water/ice holding capacity for any MEA was lower at lower temperatures and higher current densities. The durability of MEAs subjected to multiple isothermal starts was better for LANL prepared MEAs as compared to commercial MEAs, and cloth GDLs when compared to paper GDLs. The ice formation was monitored using high-resolution neutron radiography and was found to be concentrated near the cathode catalyst layer. However, there was significant ice formation in the GDLs especially at the higher temperature ({approx} -10 C) and lower current density (0.02 A/cm{sup 2}) operations. These results are consistent with the longer-term durability observations that show more severe degradation at the lower temperatures.

  8. Low-cost polyvinyl alcohol hydrogel membrane electrolyte for PEM fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Sahai, Y. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering

    2010-07-01

    This paper presented a newly developed polyvinyl alcohol (PVA) chemical hydrogel membrane electrolyte (PCHME) for use in proton exchange membrane (PEM) fuel cells. The method of PCHME preparation was described along with its properties. The membrane is much less expensive than the commonly used Nafion membrane. A direct borohydride fuel cell (DBFC) using a polyvinyl alcohol (PVA) chemical hydrogel membrane electrolyte and a nickel-based composite anode was assembled in order to test the performance of the new membrane. The cathode catalysts were carbon-supported platinum and sputtered gold. Oxygen, air, and acidified hydrogen peroxide were used as oxidants in the DBFC. Performance characteristics of the PCHME-based DBFC were obtained at different temperatures and compared with similar DBFCs using Nafion membrane electrolytes under the same operating conditions. The peak power density of the PCHME-based DBFC was somewhat higher than that of the Nafion membrane electrolyte based DBFC at 60 degrees C. The borohydride-oxygen fuel cell with PCHME yielded a maximum peak power density of 242 mW cm{sup -2} at 60 degrees C. It was concluded that the membrane presents an inexpensive alternative to widely used polymer membrane electrolytes.

  9. Temperature control of a PEM fuel cell test bench for experimental MEA assessment

    Energy Technology Data Exchange (ETDEWEB)

    More, J.J.; Puleston, P.F.; Kunusch, C. [LEICI, Departamento de Electrotecnia, Universidad Nacional de La Plata (UNLP), calle 1 esq. 47 s/n, 1900 La Plata (Argentina); Consejo de Investigaciones Cientificas y Tecnicas (CONICET), Av. Rivadavia, N 1917, C1033AAJ, Ciudad Autonoma de Buenos Aires (Argentina); Visintin, A. [Consejo de Investigaciones Cientificas y Tecnicas (CONICET), Av. Rivadavia, N 1917, C1033AAJ, Ciudad Autonoma de Buenos Aires (Argentina); Instituto de Investigaciones Fisico-Quimicas Teoricas y Aplicadas (INIFTA), Diag. 113 y 64 s/n, 1900, La Plata (Argentina)

    2010-06-15

    This paper presents the design, implementation and testing of a temperature control for a laboratory PEM fuel cell stack work bench intended for evaluation of experimental MEAs. The controller design is based on a thermal model of the fuel cell stack developed by the authors. The model is extended to the complete temperature range by considering a nonlinear description of the heating resistances. Its parameters are experimentally adjusted and its accuracy is validated in all the temperature operating range. Then, the temperature control is developed, using a proportional-integral structure with anti-windup features. It is implemented in a PC connected to an ad-hoc equipment of acquisition and control, that drives distributed cycles actuators to energize two heating resistances. The controller proved to be capable of regulating the stack temperature in a wide operating range, while eliminating the ripple typical of ON-OFF actuators. Finally, experimental results of closed loop operation are presented, demonstrating the good performance of the proposed control set up and thermal model. (author)

  10. Development and experimental validation of a PEM fuel cell dynamic model

    Energy Technology Data Exchange (ETDEWEB)

    del Real, Alejandro J.; Arce, Alicia; Bordons, Carlos [Departamento de Ingenieria de Sistemas y Automatica, Universidad de Sevilla, 41092 Seville (Spain)

    2007-11-08

    A dynamic model of a 1.2 kW polymer electrolyte membrane (PEM) fuel cell (FC) is developed and validated through a series of experiments. This dynamic model is mostly oriented towards control and operation optimization and can be a useful tool for the design of FC-based systems. In the methodology proposed, theoretical equations are combined with experimental relations, resulting in a semi-empirical formulation. The model assumptions are discussed extensively as the equations are presented. This model contributes to the description of the following areas: fluid dynamics in the gas flow fields and gas diffusion layers (oxygen, hydrogen, liquid water and vapor); thermal dynamics and temperature effects; a novel algorithm to calculate an empirical polarization curve. As a result, this model can predict both steady and transient states (such as flooding and anode purges) due to variable loads, as well as the system start-up. Based on this model, a simulator software package has been developed, which is available upon request. The model parameters have been adjusted specifically for a 1.2 kW Ballard stack, which can be considered a benchmark as it is widely used by research groups worldwide. Finally, the simulated results are compared to experimental data from the Ballard stack, demonstrating the accuracy of the proposed model methodology. (author)

  11. Experimental study on the performance of PEM fuel cells with interdigitated flow channels

    Science.gov (United States)

    Yan, Wei-Mon; Mei, Sheng-Chin; Soong, Chyi-Yeou; Liu, Zhong-Sheng; Song, Datong

    In this work, the effects of interdigitated flow channel design on the cell performance of proton exchange membrane fuel cells (PEMFCs) are investigated experimentally. To compare the effectiveness of the interdigitated flow field, the performance of the PEM fuel cells with traditional flow channel design is also tested. Besides, the effects of the flow area ratio and the baffle-blocked position of the interdigitated flow field are examined in details. The experimental results indicate that the cell performance can be enhanced with an increase in the inlet flow rate and cathode humidification temperature. Either with oxygen or air as the cathode fuel, the cells with interdigitated flow fields have better performance than conventional ones. With air as the cathode fuel, the measurements show that the interdigitated flow field results in a larger limiting current density, and the power output is about 1.4 times that with the conventional flow field. The results also show that the cell performance of the interdigitated flow field with flow area ratio of 40.23% or 50.75% is better than that with 66.75%.

  12. Experimental study on the performance of PEM fuel cells with interdigitated flow channels

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Wei-Mon; Mei, Sheng-Chin [Department of Mechatronic Engineering, Huafan University, Shih-Ting, Taipei 223, Taiwan (ROC); Soong, Chyi-Yeou [Department of Aerospace and System Engineering, Feng Chia University, Seatwen, Taichung 40724, Taiwan (ROC); Liu, Zhong-Sheng; Song, Datong [Institute for Fuel Cell Innovation, National Research Council, 3250 East Mall, Vancouver, BC (Canada V6T 1W5)

    2006-09-29

    In this work, the effects of interdigitated flow channel design on the cell performance of proton exchange membrane fuel cells (PEMFCs) are investigated experimentally. To compare the effectiveness of the interdigitated flow field, the performance of the PEM fuel cells with traditional flow channel design is also tested. Besides, the effects of the flow area ratio and the baffle-blocked position of the interdigitated flow field are examined in details. The experimental results indicate that the cell performance can be enhanced with an increase in the inlet flow rate and cathode humidification temperature. Either with oxygen or air as the cathode fuel, the cells with interdigitated flow fields have better performance than conventional ones. With air as the cathode fuel, the measurements show that the interdigitated flow field results in a larger limiting current density, and the power output is about 1.4 times that with the conventional flow field. The results also show that the cell performance of the interdigitated flow field with flow area ratio of 40.23% or 50.75% is better than that with 66.75%. (author)

  13. Water behavior in a u-shaped flow channel of PEM fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Quan, P.; Zhou, B.; Sobiesiak, A. [Windsor Univ., ON (Canada). Dept. of Mechanical, Automotive and Materials Engineering; Liu, Z.S. [National Research Council of Canada, Vancouver, BC (Canada). Inst. for Fuel Cell Innovation

    2005-07-01

    A study was conducted to find a practical approach for predicting liquid water distribution in the U-shaped flow channels of a proton exchange membrane (PEM) fuel cell. Computational fluid dynamics modeling with the FLUENT software package was used to demonstrate the two-phase flow of the air-water transport process inside the channel. It was noted that no chemical reaction occurs inside the flow channels and the liquid water is formed either on the surfaces of the flow channels or inside the flow channels. The problem can therefore be simplified as a fluid mechanics problem with water sources inside its physical domain or on its boundaries. The volume-of-fluid (VOF) model was used to track dynamic air-water interactions. Three cases with a range of initial water phase distributions corresponding to different fuel cell operating conditions were simulated numerically to gain a better understanding of water behaviour inside the serpentine channel. It was concluded that the bend area in the serpentine flow field affects the fuel cell performance. This is because it influences the flow field which in turn influences the air-water flow and water liquid distribution inside the channel or along the inside channel surfaces. 15 refs., 1 tab., 11 figs.

  14. Numerical study of water management in the air flow channel of a PEM fuel cell cathode

    Energy Technology Data Exchange (ETDEWEB)

    Quan, Peng; Lai, Ming-Chia [Department of Mechanical Engineering, Wayne State University, Detroit, MI 48202 (United States)

    2007-01-10

    The water management in the air flow channel of a proton exchange membrane (PEM) fuel cell cathode is numerically investigated using the FLUENT software package. By enabling the volume of fraction (VOF) model, the air-water two-phase flow can be simulated under different operating conditions. The effects of channel surface hydrophilicity, channel geometry, and air inlet velocity on water behavior, water content inside the channel, and two-phase pressure drop are discussed in detail. The results of the quasi-steady-state simulations show that: (1) the hydrophilicity of reactant flow channel surface is critical for water management in order to facilitate water transport along channel surfaces or edges; (2) hydrophilic surfaces also increase pressure drop due to liquid water spreading; (3) a sharp corner channel design could benefit water management because it facilitates water accumulation and provides paths for water transport along channel surface opposite to gas diffusion layer; (4) the two-phase pressure drop inside the air flow channel increases almost linearly with increasing air inlet velocity. (author)

  15. Hydrogen-Oxygen PEM Regenerative Fuel Cell at NASA Glenn Research Center

    Science.gov (United States)

    Bents, David J.

    2004-01-01

    The NASA Glenn Research Center has constructed a closed-cycle hydrogen-oxygen PEM regenerative fuel cell (RFC) to explore its potential use as an energy storage device for a high altitude solar electric aircraft. Built up over the last 2 years from specialized hardware and off the shelf components the Glenn RFC is a complete "brassboard" energy storage system which includes all the equipment required to (1) absorb electrical power from an outside source and store it as pressurized hydrogen and oxygen and (2) make electrical power from the stored gases, saving the product water for re-use during the next cycle. It consists of a dedicated hydrogen-oxygen fuel cell stack and an electrolyzer stack, the interconnecting plumbing and valves, cooling pumps, water transfer pumps, gas recirculation pumps, phase separators, storage tanks for oxygen (O2) and hydrogen (H2), heat exchangers, isolation valves, pressure regulators, nitrogen purge provisions, instrumentation, and other components. It specific developmental functions include: (1) Test fuel cells and fuel cell components under repeated closed-cycle operation (nothing escapes; everything is used over and over again). (2) Simulate diurnal charge-discharge cycles (3) Observe long-term system performance and identify degradation and loss mechanisms. (4) Develop safe and convenient operation and control strategies leading to the successful development of mission-capable, flight-weight RFC's.

  16. Hydrogen-Oxygen PEM Regenerative Fuel Cell Development at NASA Glenn Research Center

    Science.gov (United States)

    Bents, David J.; Scullin, Vincent J.; Chang, B. J.; Johnson, Donald W.; Garcia, Christopher P.; Jakupca, Ian J.

    2006-01-01

    The closed-cycle hydrogen-oxygen PEM regenerative fuel cell (RFC) at NASA Glenn Research Center has demonstrated multiple back to back contiguous cycles at rated power, and round trip efficiencies up to 52 percent. It is the first fully closed cycle regenerative fuel cell ever demonstrated (entire system is sealed: nothing enters or escapes the system other than electrical power and heat). During FY2006 the system has undergone numerous modifications and internal improvements aimed at reducing parasitic power, heat loss and noise signature, increasing its functionality as an unattended automated energy storage device, and in-service reliability. It also serves as testbed towards development of a 600 W-hr/kg flight configuration, through the successful demonstration of lightweight fuel cell and electrolyser stacks and supporting components. The RFC has demonstrated its potential as an energy storage device for aerospace solar power systems such as solar electric aircraft, lunar and planetary surface installations; any airless environment where minimum system weight is critical. Its development process continues on a path of risk reduction for the flight system NASA will eventually need for the manned lunar outpost.

  17. Test of Hydrogen-Oxygen PEM Fuel Cell Stack at NASA Glenn Research Center

    Science.gov (United States)

    Bents, David J.; Scullin, Vincent J.; Chang, Bei-Jiann; Johnson, Donald W.; Garcia, Christopher P.; Jakupca, Ian J.

    2003-01-01

    This paper describes performance characterization tests of a 64 cell hydrogen oxygen PEM fuel cell stack at NASA Glenn Research Center in February 2003. The tests were part of NASA's ongoing effort to develop a regenerative fuel cell for aerospace energy storage applications. The purpose of the tests was to verify capability of this stack to operate within a regenerative fuel cell, and to compare performance with earlier test results recorded by the stack developer. Test results obtained include polarization performance of the stack at 50 and 100 psig system pressure, and a steady state endurance run at 100 psig. A maximum power output of 4.8 kWe was observed during polarization runs, and the stack sustained a steady power output of 4.0 kWe during the endurance run. The performance data obtained from these tests compare reasonably close to the stack developer's results although some additional spread between best to worst performing cell voltages was observed. Throughout the tests, the stack demonstrated the consistent performance and repeatable behavior required for regenerative fuel cell operation.

  18. Mechanical behaviour of PEM fuel cell catalyst layers during regular cell operation

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2010-11-01

    Full Text Available Damage mechanisms in a proton exchange membrane fuel cell are accelerated by mechanical stresses arising during fuel cell assembly (bolt assembling, and the stresses arise during fuel cell running, because it consists of the materials with different thermal expansion and swelling coefficients. Therefore, in order to acquire a complete understanding of the mechanical behaviour of the catalyst layers during regular cell operation, mechanical response under steady-state hygro-thermal stresses should be studied under real cell operating conditions and in real cell geometry (three-dimensional. In this work, full three-dimensional, non-isothermal computational fluid dynamics model of a PEM fuel cell has been developed to investigate the behaviour of the cathode and anode catalyst layers during the cell operation. A unique feature of the present model is to incorporate the effect of hygro and thermal stresses into actual three-dimensional fuel cell model. In addition, the temperature and humidity dependent material properties are utilize in the simulation for the membrane. The model is shown to be able to understand the many interacting, complex electrochemical, transport phenomena, and deformation that have limited experimental data.

  19. Analytic determination of the effective thermal conductivity of PEM fuel cell gas diffusion layers

    Energy Technology Data Exchange (ETDEWEB)

    Sadeghi, E.; Bahrami, M.; Djilali, N. [Department of Mechanical Engineering and the Institute for Integrated Energy Systems, University of Victoria, Victoria, BC V8W 3P6 (Canada)

    2008-04-15

    Accurate information on the temperature field and associated heat transfer rates are particularly important in devising appropriate heat and water management strategies in proton exchange membrane (PEM) fuel cells. An important parameter in fuel cell performance analysis is the effective thermal conductivity of the gas diffusion layer (GDL). Estimation of the effective thermal conductivity is complicated because of the random nature of the GDL micro structure. In the present study, a compact analytical model for evaluating the effective thermal conductivity of fibrous GDLs is developed. The model accounts for conduction in both the solid fibrous matrix and in the gas phase; the spreading resistance associated with the contact area between overlapping fibers; gas rarefaction effects in microgaps; and salient geometric and mechanical features including fiber orientation and compressive forces due to cell/stack clamping. The model predictions are in good agreement with existing experimental data over a wide range of porosities. Parametric studies are performed using the proposed model to investigate the effect of bipolar plate pressure, aspect ratio, fiber diameter, fiber angle, and operating temperature. (author)

  20. Technology data for high temperature solid oxide electrolyser cells, alkali and PEM electrolysers

    Energy Technology Data Exchange (ETDEWEB)

    Vad Mathiesen, B.; Ridjan, I.; Connolly, D.; Pagh Nielsen, M. [Aalborg Univ., Aalborg (Denmark); Vang Hendriksen, P.; Bjerg Mogensen, M.; Hoejgaard Jensen, S.; Dalgaard Ebbesen, S. [Technical Univ. of Denmark. DTU Energy Conversion, DTU Risoe Campus, Roskilde (Denmark)

    2013-08-15

    The transition to 100% renewable energy systems will require a more integrated energy system. Connecting the electricity sector to transport is one of the major challenges in this transition, especially for long-distance and heavy-duty transport. Hydrogen is one potential solution to this challenge, by either using it directly in vehicles or indirectly via the production of synthetic fuels. Electrolysers are necessary to convert electricity to hydrogen and so they will have an essential role in the future smart energy system. However, at present there is a lot of uncertainty in relation to the current and forecasted development of electrolysers. The aim in this report is to reduce this uncertainty by gathering and aligning current knowledge in relation to the technical and economic potential of electrolysers. The results highlight existing and forecasted costs and efficiencies for alkaline, polymer electrolyte membrane (PEM), and solid oxide (SOEC) electrolysers between 2012 and 2050. These inputs can be used for analysing energy systems that include electrolysers. (Author)

  1. A review of PEM hydrogen fuel cell contamination: Impacts, mechanisms, and mitigation

    Science.gov (United States)

    Cheng, Xuan; Shi, Zheng; Glass, Nancy; Zhang, Lu; Zhang, Jiujun; Song, Datong; Liu, Zhong-Sheng; Wang, Haijiang; Shen, Jun

    This paper reviewed over 150 articles on the subject of the effect of contamination on PEM fuel cell. The contaminants included were fuel impurities (CO, CO 2, H 2S, and NH 3); air pollutants (NO x, SO x, CO, and CO 2); and cationic ions Fe 3+ and Cu 2+ resulting from the corrosion of fuel cell stack system components. It was found that even trace amounts of impurities present in either fuel or air streams or fuel cell system components could severely poison the anode, membrane, and cathode, particularly at low-temperature operation, which resulted in dramatic performance drop. Significant progress has been made in identifying fuel cell contamination sources and understanding the effect of contaminants on performance through experimental, theoretical/modeling, and methodological approaches. Contamination affects three major elements of fuel cell performance: electrode kinetics, conductivity, and mass transfer. This review was focused on three areas: (1) contamination impacts on the fuel cell performance, (2) mechanism approaches dominated by modeling studies, and (3) mitigation development. Some future work on fuel cell contamination research is suggested in order to facilitate the move toward commercialization.

  2. Development method of Hybrid Energy Storage System, including PEM fuel cell and a battery

    Science.gov (United States)

    Ustinov, A.; Khayrullina, A.; Borzenko, V.; Khmelik, M.; Sveshnikova, A.

    2016-09-01

    Development of fuel cell (FC) and hydrogen metal-hydride storage (MH) technologies continuously demonstrate higher efficiency rates and higher safety, as hydrogen is stored at low pressures of about 2 bar in a bounded state. A combination of a FC/MH system with an electrolyser, powered with a renewable source, allows creation of an almost fully autonomous power system, which could potentially replace a diesel-generator as a back-up power supply. However, the system must be extended with an electro-chemical battery to start-up the FC and compensate the electric load when FC fails to deliver the necessary power. Present paper delivers the results of experimental and theoretical investigation of a hybrid energy system, including a proton exchange membrane (PEM) FC, MH- accumulator and an electro-chemical battery, development methodology for such systems and the modelling of different battery types, using hardware-in-the-loop approach. The economic efficiency of the proposed solution is discussed using an example of power supply of a real town of Batamai in Russia.

  3. Managing Reverse Logistics or Reversing Logistics Management?

    NARCIS (Netherlands)

    M.P. de Brito (Marisa)

    2004-01-01

    textabstractIn the past, supply chains were busy fine-tuning the logistics from raw material to the end customer. Today an increasing flow of products is going back in the chain. Thus, companies have to manage reverse logistics as well.This thesis contributes to a better understanding of reverse

  4. Managing Reverse Logistics or Reversing Logistics Management?

    NARCIS (Netherlands)

    M.P. de Brito (Marisa)

    2004-01-01

    textabstractIn the past, supply chains were busy fine-tuning the logistics from raw material to the end customer. Today an increasing flow of products is going back in the chain. Thus, companies have to manage reverse logistics as well.This thesis contributes to a better understanding of reverse log

  5. Reverse logistics - a framework

    OpenAIRE

    Brito, Marisa; Dekker, Rommert

    2002-01-01

    textabstractIn this paper we define and compare Reverse Logistics definitions. We start by giving an understanding framework of Reverse Logistics: the why-what-how. By this means, we put in context the driving forces for Reverse Logistics, a typology of return reasons, a classification of products, processes and actors. In addition we provide a decision framework for Reverse Logistics and we present it according to long, medium and short term decisions, i.e. strategic-tactic-operational decis...

  6. Reverse cholesterol transport revisited

    Institute of Scientific and Technical Information of China (English)

    Astrid; E; van; der; Velde

    2010-01-01

    Reverse cholesterol transport was originally described as the high-density lipoprotein-mediated cholesterol flux from the periphery via the hepatobiliary tract to the intestinal lumen, leading to fecal excretion. Since the introduction of reverse cholesterol transport in the 1970s, this pathway has been intensively investigated. In this topic highlight, the classical reverse cholesterol transport concepts are discussed and the subject reverse cholesterol transport is revisited.

  7. Feasibility of implementation of an autonomous hybrid system for PEM fuel cells to electrify localities in rural Cuba; Factibilidad de implementacion de un sistema hibrido autonomo con celda de combustible PEM para electrificar localidades rurales en Cuba

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez Torres, Yamir [Centro de Estudios de Tecnologias Energeticas Renovables (CETER), Ciudad de la Habana (Cuba)] e-mail: yamir@ceter.cujae.edu.cu

    2009-09-15

    The use of PEM fuel cells to produce electric energy in autonomous systems is closely linked with the production and storage of hydrogen. Eventually joined with sources of renewable energy, this creates an ecologically clean and sustainable system. In several developing countries, localities exist that do not have electricity but have significant unexploited renewable energy power, where an autonomous hybrid system can be designed to electrify these population centers. This work presents a hybrid electricity scheme with a PEM fuel cell to produce hydrogen and electricity in order to electrify rural zones far from the national power grid in Cuba. The electric demand of the zone and available energy power was calculated using the informatics modeling and simulation programs HOMER, PVSYST and Matlab 1,2,3. Variability in wind and photovoltage power was determined based on daylight hours and seasonal periods throughout the year as well as their effect on the production of hydrogen and electricity. It was shown that the energy demand is met even for the most adverse scenarios. This work offers a detailed description of the behavior of the system and evidence of no effect on the environment, enabling the electrification and wellbeing of residents of the locality. [Spanish] El uso de celdas de combustible PEM para la produccion de energia electrica en sistemas autonomos esta estrechamente ligado a la produccion y almacenamiento de hidrogeno. Esto eventualmente unido a las fuentes renovables de energia forma un sistema ecologicamente limpio y sustentable. En varios paises subdesarrollados existen localidades que no cuentan con electricidad y que tienen importantes potenciales energeticos renovables no explotados actualmente en los cuales se puede disenar un sistema hibrido autonomo para electrificar estas poblaciones. En este trabajo se presenta el esquema de un sistema hibrido autonomo con celda de combustible PEM, para la produccion de hidrogeno y electricidad encaminado

  8. Experimental study of a PEM 15 W fuel cell; Influencia das temperaturas de operacao e umidificacao no desempenho de uma celula combustivel tipo 'PEM' de 15 W

    Energy Technology Data Exchange (ETDEWEB)

    Heusi, Daniel S.; Steidel, Paulo S.; Matelli, Jose A. [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil). Lab. de Combustao e Engenharia de Sistemas Termicos (LabCET); Bazzo, Edson [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil)

    2004-07-01

    Experimental results are presented for a fuel cell type PEM of 15 W. The influence of the operating temperature, as well as the effect of the humidification temperature in the draining of the gases Hydrogen and oxygen, are considered for analysis. The tests were performed at operating temperature in the range of 30 to 70 deg C and humidification temperature form 30 to 85 deg C. For hydrogen flows fixed to be 200 ml/min and 300 ml/min, as well as for oxygen flow of 165 ml/min, the polarization curves were raised taking into account different combinations of operation and different combinations of humidification temperatures. (author)

  9. Reverse logistics - a framework

    NARCIS (Netherlands)

    M.P. de Brito (Marisa); R. Dekker (Rommert)

    2002-01-01

    textabstractIn this paper we define and compare Reverse Logistics definitions. We start by giving an understanding framework of Reverse Logistics: the why-what-how. By this means, we put in context the driving forces for Reverse Logistics, a typology of return reasons, a classification of product

  10. Drinking water purification by electrosynthesis of hydrogen peroxide in a power-producing PEM fuel cell.

    Science.gov (United States)

    Li, Winton; Bonakdarpour, Arman; Gyenge, Előd; Wilkinson, David P

    2013-11-01

    The industrial anthraquinone auto-oxidation process produces most of the world's supply of hydrogen peroxide. For applications that require small amounts of H2 O2 or have economically difficult transportation means, an alternate, on-site H2 O2 production method is needed. Advanced drinking water purification technologies use neutral-pH H2 O2 in combination with UV treatment to reach the desired water purity targets. To produce neutral H2 O2 on-site and on-demand for drinking water purification, the electroreduction of oxygen at the cathode of a proton exchange membrane (PEM) fuel cell operated in either electrolysis (power consuming) or fuel cell (power generating) mode could be a possible solution. The work presented here focuses on the H2 /O2 fuel cell mode to produce H2 O2 . The fuel cell reactor is operated with a continuous flow of carrier water through the cathode to remove the product H2 O2 . The impact of the cobalt-carbon composite cathode catalyst loading, Teflon content in the cathode gas diffusion layer, and cathode carrier water flowrate on the production of H2 O2 are examined. H2 O2 production rates of up to 200 μmol h(-1)  cmgeometric (-2) are achieved using a continuous flow of carrier water operating at 30 % current efficiency. Operation times of more than 24 h have shown consistent H2 O2 and power production, with no degradation of the cobalt catalyst.

  11. An experimental study of a PEM fuel cell power train for urban bus application

    Science.gov (United States)

    Corbo, P.; Migliardini, F.; Veneri, O.

    An experimental study was carried out on a fuel cell propulsion system for minibus application with the aim to investigate the main issues of energy management within the system in dynamic conditions. The fuel cell system (FCS), based on a 20 kW PEM stack, was integrated into the power train comprising DC-DC converter, Pb batteries as energy storage systems and asynchronous electric drive of 30 kW. As reference vehicle a minibus for public transportation in historical centres was adopted. A preliminary experimental analysis was conducted on the FCS connected to a resistive load through a DC-DC converter, in order to verify the stack dynamic performance varying its power acceleration from 0.5 kW s -1 to about 4 kW s -1. The experiments on the power train were conducted on a test bench able to simulate the vehicle parameters and road characteristics on specific driving cycles, in particular the European R40 cycle was adopted as reference. The "soft hybrid" configuration, which permitted the utilization of a minimum size energy storage system and implied the use of FCS mainly in dynamic operation, was compared with the "hard hybrid" solution, characterized by FCS operation at limited power in stationary conditions. Different control strategies of power flows between fuel cells, electric energy storage system and electric drive were adopted in order to verify the two above hybrid approaches during the vehicle mission, in terms of efficiencies of individual components and of the overall power train. The FCS was able to support the dynamic requirements typical of R40 cycle, but an increase of air flow rate during the fastest acceleration phases was necessary, with only a slight reduction of FCS efficiency. The FCS efficiency resulted comprised between 45 and 48%, while the overall power train efficiency reached 30% in conditions of constant stack power during the driving cycle.

  12. Composite polymer electrolyte containing ionic liquid and functionalized polyhedral oligomeric silsesquioxanes for anhydrous PEM applications.

    Science.gov (United States)

    Subianto, Surya; Mistry, Mayur K; Choudhury, Namita Roy; Dutta, Naba K; Knott, Robert

    2009-06-01

    A new type of supported liquid membrane was made by combining an ionic liquid (IL) with a Nafion membrane reinforced with multifunctional polyhedral oligomeric silsesquioxanes (POSSs) using a layer-by-layer strategy for anhydrous proton-exchange membrane (PEM) application. The POSS was functionalized by direct sulfonation, and the sulfonated POSS (S-POSS) was incorporated into Nafion 117 membranes by the infiltration method. The resultant hybrid membrane shows strong ionic interaction between the Nafion matrix and the multifunctional POSS, resulting in increased glass transition temperature and thermal stability at very low loadings of S-POSS (1%). The presence of S-POSS has also improved the proton conductivity especially at low humidities, where it shows a marked increase due to its confinement in the ionic domains and promotes water uptake by capillary condensation. In order to achieve anhydrous conductivity, the IL 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMI-BTSI) was incorporated into these membranes to provide proton conduction in the absence of water. Although the incorporation of an IL shows a plasticizing effect on the Nafion membrane, the S-POSS composite membrane with an IL shows a higher modulus at high temperatures compared to Nafion 117 and a Nafion-IL membrane, with significantly higher proton conductivity (5 mS/cm at 150 degrees C with 20% IL). This shows the ability of the multifunctional POSS and IL to work symbiotically to achieve the desirable proton conductivity and mechanical properties of such membranes by enhancing the ionic interaction within the material.

  13. Immunization status and childhood morbidities as determinants of PEM among under-five children in slums of Kanpur

    Directory of Open Access Journals (Sweden)

    Neha Agarwal

    2014-12-01

    Full Text Available Introduction: Childhood morbidities like Acute Respiratory Infections (ARI, diarrhoea and malnutrition are very common.  As per NFHS-3, only 23% children aged 12-23 months were fully immunized in Uttar Pradesh. 9% under-five children had diarrhoea and 7.1% had ARI. Objective: To assess the impact of immunization status and childhood morbidities on nutritional status of under five children. Material & Methods: A cross sectional study was carried out among under five children in slums of Kanpur, using 30 cluster sampling technique. The sample size was calculated to be 375. From each slum, 13 subjects were studied thus giving a total sample size of 390. A pre-designed and pre-tested questionnaire was used to illicit the requisite information from the mothers of study subjects. Weight was recorded using standard technique for the same. Protein Energy Malnutrition (PEM was graded using IAP classification. Analysis of data was done using percentages and Chi square test. Results: The overall prevalence of PEM was found to be 54.87%. Malnutrition was found to be significantly higher (69.23% among unimmunized study subjects (p≤0.05. Among children who reported episodes of ARI and diarrhoea within last 1 month, 67.86% and 78.52% subjects respectively were malnourished. The association between PEM and these childhood morbidities was found to be statistically significant (p≤0.05. Conclusion: Prevention of diarrhoea and ARI and complete immunization of children under five years of age through National programmes and other health measures is the need of the hour for combating malnutrition in under five.

  14. Novel design of a disk-shaped compacted micro-structured air-breathing PEM fuel cell

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2012-01-01

    Full Text Available The presence of microelectromechanical system (MEMS technology makes it possible to manufacture the miniaturized fuel cell systems for application in portable electronic devices. The majority of research on micro-scale fuel cells is aimed at micro-power applications. There are many new miniaturized applications which can only be realized if a higher energy density power source is available compared to button cells and other small batteries. In small-scale applications, the fuel cell should be exceptionally small and have highest energy density. One way to achieve these requirements is to reduce the thickness of the cell (compacted-design for increasing the volumetric power density of a fuel cell power supply. A novel, simple to construct, air-breathing micro-structured PEM fuel cell which work in still or slowly moving air has been developed. The novel geometry enables optimum air access to the cathode without the need for pumps, fans or similar devices. In addition, the new design can achieve much higher active area to volume ratios, and hence higher volumetric power densities. Three-dimensional, multi-phase, non-isothermal CFD model of this novel design has been developed. This comprehensive model account for the major transport phenomena in an air-breathing micro-structured PEM fuel cell: convective and diffusive heat and mass transfer, electrode kinetics, transport and phase-change mechanism of water, and potential fields. The model is shown to understand the many interacting, complex electrochemical, and transport phenomena that cannot be studied experimentally. Fully three-dimensional results of the species profiles, temperature distribution, potential distribution, and local current density distribution are presented and analyzed with a focus on the physical insight and fundamental understanding. They can provide a solid basis for optimizing the geometry of the PEM micro fuel cell stack running with a passive mode.

  15. Performance evaluation and characterization of metallic bipolar plates in a proton exchange membrane (PEM) fuel cell

    Science.gov (United States)

    Hung, Yue

    Bipolar plate and membrane electrode assembly (MEA) are the two most repeated components of a proton exchange membrane (PEM) fuel cell stack. Bipolar plates comprise more than 60% of the weight and account for 30% of the total cost of a fuel cell stack. The bipolar plates perform as current conductors between cells, provide conduits for reactant gases, facilitate water and thermal management through the cell, and constitute the backbone of a power stack. In addition, bipolar plates must have excellent corrosion resistance to withstand the highly corrosive environment inside the fuel cell, and they must maintain low interfacial contact resistance throughout the operation to achieve optimum power density output. Currently, commercial bipolar plates are made of graphite composites because of their relatively low interfacial contact resistance (ICR) and high corrosion resistance. However, graphite composite's manufacturability, permeability, and durability for shock and vibration are unfavorable in comparison to metals. Therefore, metals have been considered as a replacement material for graphite composite bipolar plates. Since bipolar plates must possess the combined advantages of both metals and graphite composites in the fuel cell technology, various methods and techniques are being developed to combat metallic corrosion and eliminate the passive layer formed on the metal surface that causes unacceptable power reduction and possible fouling of the catalyst and the electrolyte. The main objective of this study was to explore the possibility of producing efficient, cost-effective and durable metallic bipolar plates that were capable of functioning in the highly corrosive fuel cell environment. Bulk materials such as Poco graphite, graphite composite, SS310, SS316, incoloy 800, titanium carbide and zirconium carbide were investigated as potential bipolar plate materials. In this work, different alloys and compositions of chromium carbide coatings on aluminum and SS316

  16. Final Project Report: Development of Micro-Structural Mitigation Strategies for PEM Fuel Cells: Morphological Simulations and Experimental Approaches

    Energy Technology Data Exchange (ETDEWEB)

    Wessel, Silvia [Ballard Materials Products; Harvey, David [Ballard Materials Products

    2013-06-28

    The durability of PEM fuel cells is a primary requirement for large scale commercialization of these power systems in transportation and stationary market applications that target operational lifetimes of 5,000 hours and 40,000 hours by 2015, respectively. Key degradation modes contributing to fuel cell lifetime limitations have been largely associated with the platinum-based cathode catalyst layer. Furthermore, as fuel cells are driven to low cost materials and lower catalyst loadings in order to meet the cost targets for commercialization, the catalyst durability has become even more important. While over the past few years significant progress has been made in identifying the underlying causes of fuel cell degradation and key parameters that greatly influence the degradation rates, many gaps with respect to knowledge of the driving mechanisms still exist; in particular, the acceleration of the mechanisms due to different structural compositions and under different fuel cell conditions remains an area not well understood. The focus of this project was to address catalyst durability by using a dual path approach that coupled an extensive range of experimental analysis and testing with a multi-scale modeling approach. With this, the major technical areas/issues of catalyst and catalyst layer performance and durability that were addressed are: 1. Catalyst and catalyst layer degradation mechanisms (Pt dissolution, agglomeration, Pt loss, e.g. Pt in the membrane, carbon oxidation and/or corrosion). a. Driving force for the different degradation mechanisms. b. Relationships between MEA performance, catalyst and catalyst layer degradation and operational conditions, catalyst layer composition, and structure. 2. Materials properties a. Changes in catalyst, catalyst layer, and MEA materials properties due to degradation. 3. Catalyst performance a. Relationships between catalyst structural changes and performance. b. Stability of the three-phase boundary and its effect on

  17. Modelado dinámico y validación experimental de una pila de combustible PEM

    OpenAIRE

    Husar, Attila Peter; Kunusch, Cristian; Puleston, Paul; Mayosky, Miguel Á.

    2008-01-01

    Resumen: En el presente trabajo se desarrolla un modelo dinámico apto para el diseño de control de un sistema de celdas de combustible experimental tipo PEM (Polymer Electrolyte Membrane). El sistema bajo análisis está basado fundamentalmente en una pila ElectroChem de 7 celdas alimentada por un compresor de aire e hidrógeno presurizado, humidificadores de aire e hidrógeno y válvulas reguladoras de presión. Se modela el sistema completo a partir de subsistemas acoplados, utilizando una combin...

  18. Vehicle emission factors of solid nanoparticles in the laboratory and on the road using Portable Emission Measurement Systems (PEMS

    Directory of Open Access Journals (Sweden)

    Barouch eGiechaskiel

    2015-12-01

    Full Text Available Emission inventories are used to quantify sources and identify trends in the emissions of air pollutants. They use vehicle-specific emission factors that are typically determined in the laboratory, through remote-sensing, vehicle chasing experiments and, more recently, on-board Portable Emission Measurement Systems (PEMS. Although PEMS is widely applied to measure gaseous pollutants, their application to Solid Particle Number (SPN emissions is new. In this paper, we discuss the current status of determining SPN emission factors both on the chassis dynamometer and on-road using PEMS-SPN. First, we determine the influence of the measurement equipment, ambient temperature, driving style and cycle characteristics, and the extra mass of the PEMS equipment on the SPN emissions. Afterward, we present the SPN emissions under type-approval conditions as well as on the road of two heavy-duty diesel vehicles equipped with Diesel Particulate Filter (DPF (one Euro VI, two light-duty diesel vehicles equipped with DPF, one light-duty vehicle equipped with a Port Fuel Injection engine (PFI, and seven Gasoline Direct Injection (GDI passenger cars (two Euro 6. We find that cold-start and strong accelerations tend to substantially increase SPN emissions. The two heavy-duty vehicles showed emissions around 2×10^13 p/km (Euro V truck and 6×10^10 p/km (Euro VI truck, respectively. One of the DPF-equipped light-duty vehicles showed emissions of 8×10^11 p/km, while the other one had one order of magnitude lower emissions. The PFI car had SPN emissions slightly higher than 1×10^12 p/km. The emissions of GDI cars spanned approximately from 8×10^11 p/km to 8×10^12 p/km. For the cars without DPF, the SPN emissions remained within a factor of two of the laboratory results. This factor was on average around 0.8 for the Euro 6 and 1.6 for the Euro 5 GDIs. The DPF equipped vehicles showed a difference of almost one order of magnitude between laboratory and on-road tests

  19. The Effect of PFSA Membrane Compression on the Predicted Performance of a High Pressure PEM Electrolysis Cell

    DEFF Research Database (Denmark)

    Olesen, Anders Christian; Kær, Søren Knudsen

    2015-01-01

    In this work, a non-equilibrium formulation of a compression dependent water uptake model has been implemented in a two-dimensional, two-phase, multi-component and non-isothermal high pressure PEM electrolysis model. The non-equilibrium formulation of the water uptake model was chosen in order...... to account for interfacial transport kinetics between each fluid phase and the perfluorinated sulfonic acid membrane. Besides modeling water uptake, the devised membrane model accounts for water transport through diffusion and electro-osmotic drag in the electrolyte phase, and hydraulic permeation...

  20. An Innovative Hybrid 3D Analytic-Numerical Approach for System Level Modelling of PEM Fuel Cells

    OpenAIRE

    Gregor Tavčar; Tomaž Katrašnik

    2013-01-01

    The PEM fuel cell model presented in this paper is based on modelling species transport and coupling electrochemical reactions to species transport in an innovative way. Species transport is modelled by obtaining a 2D analytic solution for species concentration distribution in the plane perpendicular to the gas-flow and coupling consecutive 2D solutions by means of a 1D numerical gas-flow model. The 2D solution is devised on a jigsaw puzzle of multiple coupled domains which enables the modell...

  1. On the Existence of a Weak Solution of a Half-Cell Model for PEM Fuel Cells

    Directory of Open Access Journals (Sweden)

    Shuh-Jye Chern

    2010-01-01

    Full Text Available A nonlinear boundary value problem (BVP from the modelling of the transport phenomena in the cathode catalyst layer of a one-dimensional half-cell single-phase model for proton exchange membrane (PEM fuel cells, derived from the 3D model of Zhou and Liu (2000, 2001, is studied. It is a BVP for a system of three coupled ordinary differential equations of second order. Schauder's fixed point theorem is applied to show the existence of a solution in the Sobolev space 1.

  2. Preparación y evaluación de electrocatalizadores de platino sobre diferentes soportes para celdas de combustible PEM

    OpenAIRE

    2016-01-01

    Se sintetizaron electrocatalizadores de Pt para celdas de combustible PEM sobre diferentes soportes: SC, modificado y sin modificar, y Vulcan XC72 para comparación. El material SC exhibió características que lo hacen un potencial sustituto del soporte Vulcan XC72. El estudio de estabilidad en las condiciones de operación de una celda de combustible PEM mostró que el electrocatalizador soportado sobre SC tiene una velocidad de degradación mayor al soportado sobre Vulcan XC72. Se requiere optim...

  3. Development and characterization of a portable high-temperature PEM fuel cell system; Entwicklung und Charakterisierung eines portablen Hochtemperatur-PEM-Brennstoffzellensystems

    Energy Technology Data Exchange (ETDEWEB)

    Kurz, Timo

    2011-07-01

    In this thesis, the development of a High Temperature Polymer Electrolyte Membrane Fuel Cell (HT-PEMFC) system prototype is presented. In order to identify appropriate operating conditions and design factors, the development is supported by characterisation and modelling of HT-PEM single cells. The specific properties of this fuel cell type, together with the modelling and characterisation results, are used to achieve a compact and portable system design. Two non-isothermal 2D models are developed and coupled to each other in order to obtain fast and precise calculations in all dimensions in the cell. The models account for the conservation of mass, momentum, species, charge and energy. Additionally, the CO tolerance is investigated in detail. This is achieved by calculating catalyst coverage with four different species on the anode catalyst layer. The modelling results are validated using experimental data over a wide operating range. With the two coupled models, variations caused by different channel-rib structures, both parallel and perpendicular to the channel are investigated and optimal channel-rib ratios are identified. Based on the modelling and experimental results, the design of a compact and portable HT-PEMFC stack module is presented. The aim of the prototype development is to construct a modular system with high power density that meets the specific demands of HT-PEMFC operation. In order to reach this goal, innovative constructive details are developed: Stack compression is achieved with an aramid fibre coil to reduce weight and volume compared to threaded bolts. The development of this compression design is supported by experimental and modelling work. The principle of an open cathode is applied to combine the cathode-fed stream with the air cooling by only one channel, reducing the balance of plant. The air channel configuration is designed with the aid of Computational Fluid Dynamics. The developed channel design helps to maintain a small pressure

  4. Influence of the gas diffusion layer on PEM fuel cell power density and cost; Einfluesse der Gasdiffusionslage auf Leistungsdichte und Kosten der PEM-Brennstoffzelle

    Energy Technology Data Exchange (ETDEWEB)

    Joerg, Kleemann

    2012-07-01

    revealed the performance potential of an optimized channel/landing structure in the flowfield plate, that was afterwards proven experimentally in adapted plates. In this way, performance with the initially poor performing roll good diffusion layers could be improved by up to 50% and even exceeded the original level of the non-rollable reference material. Accordingly, a cost reduction of roughly 30% for the fuel cell stack can be derived just based on reduced material usage. Thus, a considerable step in understanding the gas diffusion layer influence on PEM fuel cell performance could be verified and at the same time, performance was optimized significantly along with applying cheaper materials. (orig.)

  5. Increasing the efficiency of a portable PEM fuel cell by altering the cathode channel geometry: A numerical and experimental study

    Energy Technology Data Exchange (ETDEWEB)

    Henriques, T.; Cesar, B.; Branco, P.J. Costa [Instituto Superior Tecnico (IST), Center for Innovation in Electrical and Energy Engineering, CIE3, Av. Rovisco Pais, 1049-001, Lisboa (Portugal)

    2010-04-15

    Portable fuel cells are receiving great attention today mainly because their energy density is higher than any portable battery solution. Among other types, portable polymer electrolyte membrane (PEM) fuel cells are an established technology where research on increasing their efficiency is leading product development and manufacturing. The objective of this work was to study and evaluate the redesign of a commercial portable fuel cell, improving its efficiency. A three-dimensional model of the original PEM fuel cell with parallel plus a transversal flow channel design was developed using Comsol Multiphysics, including the effects of liquid water formation and electric current production. Using this model, the effects of different channel geometries and respective cathode flow rates on the cell's performance, including the local transport characteristics, were studied. Laboratory tests with various fuel cell stacks using the new channels structure were effectuated for an evaluation of the fuel cell's performance, showing improvements in its efficiency of up to 26.4%. (author)

  6. Investigation of membrane electrode assemblies (MEAs) for efficient and optimum performance of polymer electrolyte membrane (PEM) fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Okafor, A.C.; Mogbo, H.M.C. [Missouri Univ. of Science and Technology, Rolla, MO (United States). Dept. of Mechanical and Aerospace Engineering

    2009-07-01

    The core component of a proton exchange membrane (PEM) fuel cell is the membrane electrode assembly (MEA) which includes an assembled stack of ion exchange membrane reaction catalysts, and the electrodes that converts hydrogen ions into electricity. This study investigated various MEAs in an effort to improve fuel cell performance and durability. First, a literature review of different commercially available and innovative PEM fuel cell MEAs was conducted. The best performing MEAs were then investigated in terms of fuel cell output voltage, operating temperature, thermal and chemical stability, methanol permeability, proton conductivity, and hydrogen crossover. The selected MEAs based on their high output voltage, ability to withstand chemical/radical attacks, overall fuel cell performance, and other excellent physical properties were identified as phosphoric acid-doped polybenzimidazole (PBI/H{sub 3}PO{sub 4}), disulfonated poly(sulfide sulfone)s (SPSSF), and Nafion 212. Finally, in-house designed and manufactured bipolar plates of different materials and flow field configurations are being used to validate these 3 identified MEAs in a single fuel cell and 3 fuel cell stacks.

  7. Investigation of GDL compression effects on the performance of a PEM fuel cell cathode by lattice Boltzmann method

    Science.gov (United States)

    Molaeimanesh, G. R.; Nazemian, M.

    2017-08-01

    Proton exchange membrane (PEM) fuel cells with a great potential for application in vehicle propulsion systems will have a promising future. However, to overcome the exiting challenges against their wider commercialization further fundamental research is inevitable. The effects of gas diffusion layer (GDL) compression on the performance of a PEM fuel cell is not well-recognized; especially, via pore-scale simulation technique capturing the fibrous microstructure of the GDL. In the current investigation, a stochastic microstructure reconstruction method is proposed which can capture GDL microstructure changes by compression. Afterwards, lattice Boltzmann pore-scale simulation technique is adopted to simulate the reactive gas flow through 10 different cathode electrodes with dissimilar carbon paper GDLs produced from five different compression levels and two different carbon fiber diameters. The distributions of oxygen mole fraction, water vapor mole fraction and current density for the simulated cases are presented and analyzed. The results of simulations demonstrate that when the fiber diameter is 9 μm adding compression leads to lower average current density while when the fiber diameter is 7 μm the compression effect is not monotonic.

  8. Oxygen reduction on a Pt(111) catalyst in HT-PEM fuel cells by density functional theory

    Science.gov (United States)

    Sun, Hong; Li, Jie; Almheiri, Saif; Xiao, Jianyu

    2017-08-01

    The oxygen reduction reaction plays an important role in the performance of high-temperature proton exchange membrane (HT-PEM) fuel cells. In this study, a molecular dynamics model, which is based on the density functional theory and couples the system's energy, the exchange-correlation energy functional, the charge density distribution function, and the simplified Kohn-Sham equation, was developed to simulate the oxygen reduction reaction on a Pt(111) surface. Additionally, an electrochemical reaction system on the basis of a four-electron reaction mechanism was also developed for this simulation. The reaction path of the oxygen reduction reaction, the product structure of each reaction step and the system's energy were simulated. It is found that the first step reaction of the first hydrogen ion with the oxygen molecule is the controlling step of the overall reaction. Increasing the operating temperature speeds up the first step reaction rate and slightly decreases its reaction energy barrier. Our results provide insight into the working principles of HT-PEM fuel cells.

  9. Oxygen reduction on a Pt(111 catalyst in HT-PEM fuel cells by density functional theory

    Directory of Open Access Journals (Sweden)

    Hong Sun

    2017-08-01

    Full Text Available The oxygen reduction reaction plays an important role in the performance of high-temperature proton exchange membrane (HT-PEM fuel cells. In this study, a molecular dynamics model, which is based on the density functional theory and couples the system’s energy, the exchange-correlation energy functional, the charge density distribution function, and the simplified Kohn–Sham equation, was developed to simulate the oxygen reduction reaction on a Pt(111 surface. Additionally, an electrochemical reaction system on the basis of a four-electron reaction mechanism was also developed for this simulation. The reaction path of the oxygen reduction reaction, the product structure of each reaction step and the system’s energy were simulated. It is found that the first step reaction of the first hydrogen ion with the oxygen molecule is the controlling step of the overall reaction. Increasing the operating temperature speeds up the first step reaction rate and slightly decreases its reaction energy barrier. Our results provide insight into the working principles of HT-PEM fuel cells.

  10. Reversible cortical blindness: posterior reversible encephalopathy syndrome.

    Science.gov (United States)

    Bandyopadhyay, Sabyasachi; Mondal, Kanchan Kumar; Das, Somnath; Gupta, Anindya; Biswas, Jaya; Bhattacharyya, Subir Kumar; Biswas, Gautam

    2010-11-01

    Cortical blindness is defined as visual failure with preserved pupillary reflexes in structurally intact eyes due to bilateral lesions affecting occipital cortex. Bilateral oedema and infarction of the posterior and middle cerebral arterial territory, trauma, glioma and meningioma of the occipital cortex are the main causes of cortical blindness. Posterior reversible encephalopathy syndrome (PRES) refers to the reversible subtype of cortical blindness and is usually associated with hypertension, diabetes, immunosuppression, puerperium with or without eclampsia. Here, 3 cases of PRES with complete or partial visual recovery following treatment in 6-month follow-up are reported.

  11. Introduction to reversible computing

    CERN Document Server

    Perumalla, Kalyan S

    2013-01-01

    Few books comprehensively cover the software and programming aspects of reversible computing. Filling this gap, Introduction to Reversible Computing offers an expanded view of the field that includes the traditional energy-motivated hardware viewpoint as well as the emerging application-motivated software approach. Collecting scattered knowledge into one coherent account, the book provides a compendium of both classical and recently developed results on reversible computing. It explores up-and-coming theories, techniques, and tools for the application of rever

  12. Fundamental study of mechanical and chemical degradation mechanisms of PEM fuel cell membranes

    Science.gov (United States)

    Yoon, Wonseok

    One of the important factors determining the lifetime of polymer electrolyte membrane fuel cells (PEMFCs) is membrane degradation and failure. The lack of effective mitigation methods is largely due to the currently very limited understanding of the underlying mechanisms for mechanical and chemical degradations of fuel cell membranes. In order to understand degradation of membranes in fuel cells, two different experimental approaches were developed; one is fuel cell testing under open circuit voltage (OCV) with bi-layer configuration of the membrane electrode assemblies (MEAs) and the other is a modified gas phase Fenton's test. Accelerated degradation tests for polymer electrolyte membrane (PEM) fuel cells are frequently conducted under open circuit voltage (OCV) conditions at low relative humidity (RH) and high temperature. With the bi-layer MEA technique, it was found that membrane degradation is highly localized across thickness direction of the membrane and qualitatively correlated with location of platinum (Pt) band through mechanical testing, Infrared (IR) spectroscopy, fluoride emission, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS) measurement. One of the critical experimental observations is that mechanical behavior of membranes subjected to degradation via Fenton's reaction exhibit completely different behavior with that of membranes from the OCV testing. This result led us to believe that other critical factors such as mechanical stress may affect on membrane degradation and therefore, a modified gas phase Fenton's test setup was developed to test the hypothesis. Interestingly, the results showed that mechanical stress directly accelerates the degradation rate of ionomer membranes, implying that the rate constant for the degradation reaction is a function of mechanical stress in addition to commonly known factors such as temperature and humidity. Membrane degradation induced by

  13. Engineered Nano-scale Ceramic Supports for PEM Fuel Cells. Tech Team Meeting Presentaion

    Energy Technology Data Exchange (ETDEWEB)

    Brosha, Eric L. [Los Alamos National Laboratory; Elbaz Alon, Lior [Los Alamos National Laboratory; Henson, Neil J. [Los Alamos National Laboratory; Rockward, Tommy [Los Alamos National Laboratory; Roy, Aaron [University of New Mexico; Serov, Alexey [University of New Mexico; Ward, Timothy [University of New Mexico

    2012-08-13

    Catalyst support durability is currently a technical barrier for commercialization of polymer electrolyte membrane (PEM) fuel cells, especially for transportation applications. Degradation and corrosion of the conventional carbon supports leads to losses in active catalyst surface area and, consequently, reduced performance. As a result, the goal of this work is to develop support materials that interact strongly with Pt, yet sustain bulk-like catalytic activities with very highly dispersed particles. Ceramic materials that are prepared using conventional solid-state methods have large grain sizes and low surface areas that can only be minimally ameliorated through grinding and ball milling. Other synthesis routes to produce ceramic materials must be investigated and utilized in order to obtain desired surface areas. In this work, several different synthesis methods are being utilized to prepare electronically conductive ceramic boride, nitride, and oxide materials with high surface areas and have the potential for use as PEMFC catalyst supports. Polymer-assisted deposition (PAD) and aerosol-through plasma (A-T-P) torch are among several methods used to obtain ceramic materials with surface areas that are equal to, or exceed Vulcan XC-72R supports. Cubic Mo-based ceramic phases have been prepared with average XRD-determined crystallite sizes as low as 1.6 nm (from full profile, XRD fitting) and a BET surface area exceeding 200 m{sup 2}/g. Additionally, black, sub-stoichiometric TiO{sub 2-x}, have been prepared with an average crystallite size in the 4 nm range and surface areas exceeding 250 m{sup 2}/gr. Pt disposition using an incipient wetness approach produced materials with activity for hydrogen redox reactions and ORR. Cyclic voltammetry data will be shown for a variety of potential Pt/ceramic catalysts. Initial experiments indicate enhanced Pt metal-support interactions as well. Plane wave periodic density functional calculations (VASP) are being used to

  14. Habitat Demonstration Unit Project Leadership and Management Strategies

    Science.gov (United States)

    Kennedy, Kriss J.

    2011-01-01

    This paper gives an overview of the National Aeronautics and Space Administration (NASA) led multi-center Habitat Demonstration Unit (HDU) project leadership and management strategies. The HDU project team constructed and tested an analog prototype lunar surface habitat/laboratory called the Pressurized Excursion Module (PEM) during 2010. The prototype unit subsystems were integrated in a short amount of time, utilizing a tiger team approach that brought together over 20 habitation-related technologies and innovations from a variety of NASA centers. This paper describes the leadership and management strategies as well as lessons learned pertaining to leading and managing a multi-center diverse team in a rapid prototype environment. The PEM configuration went from a paper design to an operational surface habitat demonstration unit in less than 12 months. The HDU project is part of the strategic plan from the Exploration Systems Mission Directorate (ESMD) Directorate Integration Office (DIO) and the Exploration Mission Systems Office (EMSO) to test destination elements in analog environments. The 2011 HDU-Deep Space Habitat (DSH) configuration will build upon the PEM work, and emphasize validity of crew operations (remote working and living), EVA operations, mission operations, logistics operations, and science operations that might be required in a deep space context for Near Earth Object (NEO) exploration mission architectures. The 2011 HDU-DSH will be field-tested during the 2011 Desert Research and Technologies Studies (DRaTS) field tests. The HDU project is a "technology-pull" project that integrates technologies and innovations from multiple NASA centers. This project will repurpose the HDU 2010 demo unit that was field tested in the 2010 DRaTS, adding habitation functionality to the prototype unit. This paper will describe the strategy of establishing a multi-center project management team that put in place the key multi-center leadership skills and

  15. Reversible Logic Circuit Synthesis

    CERN Document Server

    Shende, V V; Markov, I L; Prasad, A K; Hayes, John P.; Markov, Igor L.; Prasad, Aditya K.; Shende, Vivek V.

    2002-01-01

    Reversible, or information-lossless, circuits have applications in digital signal processing, communication, computer graphics and cryptography. They are also a fundamental requirement for quantum computation. We investigate the synthesis of reversible circuits that employ a minimum number of gates and contain no redundant input-output line-pairs (temporary storage channels). We propose new constructions for reversible circuits composed of NOT, Controlled-NOT, and TOFFOLI gates (the CNT gate library) based on permutation theory. A new algorithm is given to synthesize optimal reversible circuits using an arbitrary gate library. We also describe much faster heuristic algorithms. We also pursue applications of the proposed techniques to the synthesis of quantum circuits.

  16. Reverse Core Engine with Thrust Reverser

    Science.gov (United States)

    Suciu, Gabriel L. (Inventor); Chandler, Jesse M. (Inventor)

    2017-01-01

    An engine system has a gas generator, a bi-fi wall surrounding at least a portion of the gas generator, a casing surrounding a fan, and the casing having first and second thrust reverser doors which in a deployed position abut each other and the bi-fi wall.

  17. Compendium of NASA Data Base for the Global Tropospheric Experiment's Pacific Exploratory Mission-Tropics B (PEM-Tropics B). Volume 1; DC-8

    Science.gov (United States)

    Scott, A. Donald, Jr.; Kleb, Mary M.; Raper, James L.

    2000-01-01

    This report provides a compendium of NASA aircraft data that are available from NASA's Global Tropospheric Experiment's (GTE) Pacific Exploratory Mission-Tropics B (PEM-Tropics B) conducted in March and April 1999. PEM-Tropics B was conducted during the southern-tropical wet season when the influence from biomass burning observed in PEM-Tropics A was minimal. Major deployment sites were Hawaii, Kiritimati (Christmas Island), Tahiti, Fiji, and Easter Island. The broad goals of PEM-Tropics B were to improved understanding of the oxidizing power of the atmosphere and the processes controlling sulfur aerosol formation and to establish baseline values for chemical species that are directly coupled to the oxidizing power and aerosol loading of the troposphere. The purpose of this document is to provide a representation of aircraft data that will be available in archived format via NASA Langley's Distributed Active Archive Center (DAAC) or are available through the GTE Project Office archive. The data format is not intended to support original research/analysis, but to assist the reader in identifying data that are of interest.

  18. Compendium of NASA Data Base for the Global Tropospheric Experiment's Pacific Exploratory Mission - Tropics B (PEM-Tropics B). Volume 2; P-3B

    Science.gov (United States)

    Scott, A. Donald, Jr.; Kleb, Mary M.; Raper, James L.

    2000-01-01

    This report provides a compendium of NASA aircraft data that are available from NASA's Global Tropospheric Experiment's (GTE) Pacific Exploratory Mission-Tropics B (PEM-Tropics B) conducted in March and April 1999. PEM-Tropics B was conducted during the southern-tropical wet season when the influence from biomass burning observed in PEM-Tropics A was minimal. Major deployment sites were Hawaii, Kiritimati (Christmas Island), Tahiti, Fiji, and Easter Island. The broad goals of PEM-Tropics B were to improved understanding of the oxidizing power of the atmosphere and the processes controlling sulfur aerosol formation and to establish baseline values for chemical species that are directly coupled to the oxidizing power and aerosol loading of the troposphere. The purpose of this document is to provide a representation of aircraft data that will be available in archived format via NASA Langley's Distributed Active Archive Center (DAAC) or are available through the GTE Project Office archive. The data format is not intended to support original research/analysis, but to assist the reader in identifying data that are of interest.

  19. AN IMPROVED DESIGN OF A MULTIPLIER USING REVERSIBLE LOGIC GATES

    Directory of Open Access Journals (Sweden)

    H.R.BHAGYALAKSHMI

    2010-08-01

    Full Text Available Reversible logic gates are very much in demand for the future computing technologies as they are known to produce zero power dissipation under ideal conditions. This paper proposes an improved design of a multiplier using reversible logic gates. Multipliers are very essential for the construction of various computational units of a quantum computer. The quantum cost of a reversible logic circuit can be minimized by reducing the number of reversible logic gates. For this two 4*4 reversible logic gates called a DPG gate and a BVF gate are used.

  20. Quantum reverse hypercontractivity

    Energy Technology Data Exchange (ETDEWEB)

    Cubitt, Toby [Department of Computer Science, University College London, London, United Kingdom and Centre for Quantum Information and Foundations, DAMTP, University of Cambridge, Cambridge (United Kingdom); Kastoryano, Michael [NBIA, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen (Denmark); Montanaro, Ashley [School of Mathematics, University of Bristol, Bristol (United Kingdom); Temme, Kristan [Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125 (United States)

    2015-10-15

    We develop reverse versions of hypercontractive inequalities for quantum channels. By generalizing classical techniques, we prove a reverse hypercontractive inequality for tensor products of qubit depolarizing channels. We apply this to obtain a rapid mixing result for depolarizing noise applied to large subspaces and to prove bounds on a quantum generalization of non-interactive correlation distillation.

  1. Clocked Thrust Reversers

    Science.gov (United States)

    Suciu, Gabriel L. (Inventor); Chandler, Jesse M. (Inventor)

    2017-01-01

    An aircraft includes a fuselage including a propulsion system supported within an aft portion. A thrust reverser is mounted proximate to the propulsion system for directing thrust in a direction to slow the aircraft. The thrust reverser directs thrust at an angle relative to a vertical plane to reduce interference on control surfaces and reduce generation of underbody lift.

  2. Atrioventricular Pacemaker Lead Reversal

    Directory of Open Access Journals (Sweden)

    Mehmet K Aktas, MD

    2007-01-01

    Full Text Available During cardiac surgery temporary epicardial atrial and ventricular leads are placed in case cardiac pacing is required postoperatively. We present the first reported series of patients with reversal of atrioventricular electrodes in the temporary pacemaker without any consequent deleterious hemodynamic effect. We review the electrocardiographic findings and discuss the findings that lead to the discovery of atrioventricular lead reversal.

  3. Reversible cerebral vasoconstriction syndrome

    Directory of Open Access Journals (Sweden)

    Saini Monica

    2009-01-01

    Full Text Available Reversible cerebral vasoconstriction syndromes (RCVS are a group of disorders that have in common an acute presentation with headache, reversible vasoconstriction of cerebral arteries, with or without neurological signs and symptoms. In contrast to primary central nervous system vasculitis, they have a relatively benign course. We describe here a patient who was diagnosed with RCVS.

  4. Towards Reversible Sessions

    Directory of Open Access Journals (Sweden)

    Francesco Tiezzi

    2014-06-01

    Full Text Available In this work, we incorporate reversibility into structured communication-based programming, to allow parties of a session to automatically undo, in a rollback fashion, the effect of previously executed interactions. This permits taking different computation paths along the same session, as well as reverting the whole session and starting a new one. Our aim is to define a theoretical basis for examining the interplay in concurrent systems between reversible computation and session-based interaction. We thus enrich a session-based variant of pi-calculus with memory devices, dedicated to keep track of the computation history of sessions in order to reverse it. We discuss our initial investigation concerning the definition of a session type discipline for the proposed reversible calculus, and its practical advantages for static verification of safe composition in communication-centric distributed software performing reversible computations.

  5. Purchasing Power Parity and Heterogeneous Mean Reversion

    NARCIS (Netherlands)

    C.G. Koedijk (Kees); B. Tims (Ben); M.A. van Dijk (Mathijs)

    2005-01-01

    textabstractThis paper analyzes the properties of multivariate tests of purchasing power parity (PPP) that fail to take heterogeneity in the speed of mean reversion across real exchange rates into account. We compare the performance of homogeneous and heterogeneous unit root testing methodologies.

  6. Calculation of the hydrogen produced by a PEM electrolyzer based on solar radiation in Zacatecas; Estimacion del hidrogeno producido por un electrolizador PEM a partir de la radiacion solar en Zacatecas

    Energy Technology Data Exchange (ETDEWEB)

    Duron-Torres, S. M.; Villagrana-Munoz, L.E.; Garcia-Saldivar, V.M. [Universidad Autonoma de Zacatecas, Zacatecas (Mexico)]. E-mail: duronsm@prodigy.net.mx; Arriaga-Hurtado, L.G. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, Pedro Escobedo, Queretaro (Mexico)

    2009-09-15

    This work presents the calculation of the amount of hydrogen obtained from the use of a proton exchange membrane electrolysis cell. Measurements performed at the solarimeter station of the Campus Siglo XXI at the Zacatecas Autonomous University were used as a basis. Solar radiation was analyzed for the period November 2007 to April 2008, corresponding to when there is less solar radiation. The amount of average irradiation measured was de 6.6 kW-h/ m{sup 2}. The evaluation of the solar-hydrogen system was conducted with linear regressions of the behavior of the hydrogen flow in LN/min versus the solar irradiance in W/m{sup 2} for a PEM electrolyzer. The results obtained indicate that the maximum amount of hydrogen produced occurred in the month of April, with 9LN/min produced with a radiation intensity of roughly 900 W/m{sup 2}; a minimum of 6 LN/min was produced with a radiation of roughly 600 W/m{sup 2} during the month of December. Based on these results, we can foresee a minimum amount of hydrogen generated of 6 to 9 LN/min in the state of Zacatecas during an entire year, since the months evaluated are those with the least solar radiation. The measurements performed by the Siglo XXI station show that the solar radiation power measured is higher than the national and worldwide means, making Zacatecas a strategic state for the use of this renewable energy. The amounts calculated of hydrogen produced would indicate that it is feasible to establish solar-hydrogen systems in this region in order to obtain this energy using PEM electrolyzers. [Spanish] En este trabajo se presenta el calculo de la cantidad de hidrogeno que se obtendria, empleando un electrolizador de membrana de intercambio de protones tipo, tomando como base las medidas realizadas en la Estacion Solarimetrica del Campus Siglo XXI en la Universidad Autonoma de Zacatecas. El analisis de la radiacion solar se realizo en el periodo de noviembre de 2007 a abril de 2008 correspondiendo a la epoca de menor

  7. Analysis of early ageing of PEM fuel cell stacks in a SAM light electric vehicle; Analyse der vorzeitigen Alterung des PEM-Stacks im LEV SAM - Jahresbericht/Schlussbericht 2006

    Energy Technology Data Exchange (ETDEWEB)

    Hoeckel, M.; Ruge, M.

    2006-12-15

    This illustrated final report for the Swiss Federal Office of Energy (SFOE) presents and discusses the results of investigations concerning a PEM fuel cell stack made at the University of Applied Sciences in Bienne, Switzerland. The six-kilowatt stack showed considerable loss of power over a two-year period. The reasons behind these losses are discussed, including those caused by insufficient sealing and long periods of standstill. The measurements made on the fuel cell stack are presented and discussed. The causes of the loss of power are discussed and resulting modifications made to the stack are described. Recommendations concerning the regular use of the fuel cell stack are made in order to ensure correct operation in the future.

  8. New composite membranes based on modified Nafion or Flemion for PEM fuel cell application

    Science.gov (United States)

    Tian, Huimin

    Nafion and Flemion during the procedure of casting composite membrane and there was the interaction between the sulphonic acid group and STA. X-ray photoelectron spectroscopy shows the existence of W-S and W-C bonds in composite membrane. This can be used to explain the previous experimental observation that the composite membrane with STA has higher conductivity and water uptake than the composite membrane without STA. The above studies allowed us to conclude that the improvements in ionic conductivity and water uptake are due to the change of the chemical composition of the composite membranes by the addition of silicotungstic acid. The current-potential polarization characterization of composite Nafion/STA and Flemion/STA membranes was measured using H2/O2 single polymer electrolyte membrane (PEM) fuel cell system. The performance based on composite Nafion/STA and Flemion/STA membranes is always better than that based on cast Nafion or cast Flemion without STA membranes. The improvement in the fuel cell characteristics for the composite Nafion/STA and Flemion/STAmembrane is due to a combined effect of the polymer and STA. The existence of STA improves the fuel cell performance and make this operation feasible under high temperature.

  9. Development of Ultra-Low Platinum Alloy Cathode Catalysts for PEM Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Popov, Branko N. [Univ. of South Carolina, Columbia, SC (United States). Dept. of Chemical Engineering; Weidner, John [Univ. of South Carolina, Columbia, SC (United States)

    2016-01-07

    The goal of this project is to synthesize a low cost PEM fuel cell cathode catalyst and support with optimized average mass activity, stability of mass activity, initial high current density performance under H2/air (power density), and catalyst and support stability able to meet 2017 DOE targets for electrocatalysts for transportation applications. Pt*/ACCS-2 catalyst was synthesized according to a novel methodology developed at USC through: (i) surface modification, (ii) metal catalyzed pyrolysis and (iii) chemical leaching to remove excess meal used to dope the support. Pt* stands for suppressed platinum catalyst synthesized with Co doped platinum. The procedure results in increasing carbon graphitization, inclusion of cobalt in the bulk and formation of non-metallic active sites on the carbon surface. Catalytic activity of the support shows an onset potential of 0.86 V for the oxygen reduction reaction (ORR) with well-defined kinetic and mass transfer regions and 2.5% H2O2 production. Pt*/ACCS-2 catalyst durability under 0.6-1.0 V potential cycling and support stability under 1.0-1.5 V potential cycling was evaluated. The results indicated excellent catalyst and support performance under simulated start-up/shut down operating conditions (1.0 – 1.5 V, 5000 cycles) which satisfy DOE 2017 catalyst and support durability and activity. The 30% Pt*/ACCS-2 catalyst showed high initial mass activity of 0.34 A/mgPGM at 0.9 ViR-free and loss of mass activity of 45% after 30,000 cycles (0.6-1.0 V). The catalyst performance under H2-air fuel cell operating conditions showed only 24 mV (iR-free) loss at 0.8 A/cm2 with an ECSA loss of 42% after 30,000 cycles (0.6-1.0 V). The support stability under 1.0-1.5 V potential cycling showed mass activity loss of 50% and potential loss of 8 mV (iR-free) at 1.5 A/cm2. The ECSA loss was 22% after 5,000 cycles. Furthermore, the Pt*/ACCS-2 catalyst showed an

  10. Simulation of a hydrogen production and purification system for a PEM fuel-cell using bioethanol as raw material

    Energy Technology Data Exchange (ETDEWEB)

    Giunta, Pablo; Amadeo, Norma; Laborde, Miguel [Facultad de Ingenieria, Universidad de Buenos Aires, Laboratorio de Procesos Cataliticos, Pabellon de Industrias, Ciudad Universitaria, 1428 Buenos Aires (Argentina); Mosquera, Carlos [Facultad de Ingenieria, Universidad de Buenos Aires, Departamento de Fisica, 1063 Buenos Aires (Argentina)

    2007-01-10

    A process to produce 'fuel-cell grade' hydrogen from ethanol steam reforming is analyzed from a thermodynamic point of view. The hydrogen purification process consists of WGS and COPROX reactors. Equations to evaluate the efficiency of the system, including the fuel cell, are presented. A heat exchange network is proposed in order to improve the exploitation of the available power. The effect of key variables such as the reformer temperature and the ethanol/water molar feed ratio on the fuel-cell efficiency is discussed. Results show that it is feasible to carry out the energy integration of the hydrogen catalytic production and purification-PEM fuel-cell system, using ethanol as raw material. The technology of 'fuel-cell grade' hydrogen production using ethanol as raw material is a very attractive alternative to those technologies based in fossil fuels. (author)

  11. Integrated modeling and control of a PEM fuel cell power system with a PWM DC/DC converter

    Energy Technology Data Exchange (ETDEWEB)

    Choe, Song-Yul; Ahn, Jong-Woo [Mechanical Engineering Department, Auburn University, Auburn, AL 36848 (United States); Lee, Jung-Gi [Electrical Engineering Department, Pohang University of Science and Technology, Pohang (Korea); Baek, Soo-Hyun [Electrical Engineering Department, Dong-guk University, Seoul (Korea)

    2007-02-10

    A fuel cell powered system is regarded as a high current and low voltage source. To boost the output voltage of a fuel cell, a DC/DC converter is employed. Since these two systems show different dynamics, they need to be coordinated to meet the demand of a load. This paper proposes models for the two systems with associated controls, which take into account a PEM fuel cell stack with air supply and thermal systems, and a PWM DC/DC converter. The integrated simulation facilitates optimization of the power control strategy, and analyses of interrelated effects between the electric load and the temperature of cell components. In addition, the results show that the proposed power control can coordinate the two sources with improved dynamics and efficiency at a given dynamic load. (author)

  12. Estimating Important Electrode Parameters of High Temperature PEM Fuel Cells By Fitting a Model to Polarisation Curves and Impedance Spectra

    DEFF Research Database (Denmark)

    Vang, Jakob Rabjerg; Zhou, Fan; Andreasen, Søren Juhl;

    2015-01-01

    A high temperature PEM (HTPEM) fuel cell model capable of simulating both steady state and dynamic operation is presented. The purpose is to enable extraction of unknown parameters from sets of impedance spectra and polarisation curves. The model is fitted to two polarisation curves and four...... impedance spectra measured on a Dapozol 77 MEA. The model is capable of achieving good agreement with the recorded curves. Except at OCV, where the voltage is overpredicted, the simulated polarisation curves deviate maximum 3.0% from the measurements. The impedance spectra deviate maximum 3.7%. The fitted...... parameter values are within the range reported in literature. The only exception is the catalyst layer acid content, which is an order of magnitude lower. This may derive from acid migration. The model is used to illustrate the effect of reactant dynamics on the impedance spectrum. The model can aid...

  13. Adaptive Passivity-Based Control of PEM Fuel Cell/Battery Hybrid Power Source for Stand-Alone Applications

    Directory of Open Access Journals (Sweden)

    KALANTAR, A.

    2010-11-01

    Full Text Available In this paper, a DC hybrid power source composed of PEM fuel cell as main source, Li-ion battery storage as transient power source and their power electronic interfacing is modelled based on Euler-Lagrange framework. Subsequently, adaptive passivity-based controllers are synthesized using the energy shaping and damping injection technique. Local asymptotic stability is insured as well. In addition, the power management system is designed in order to manage power flow between components. Evaluation of the proposed system and simulation of the hybrid system are accomplished using MATLAB/Simulink. Afterwards, linear PI controllers are provided for the purpose of comparison with proposed controllers responses. The results show that the outputs of hybrid system based on adaptive passivity-based controllers have a good tracking response, low overshoot, short settling time and zero steady-state error. The comparison of results demonstrates the robustness of the proposed controllers for reference DC voltage and resistive load changes.

  14. New highly active oxygen reduction electrode for PEM fuel cell and Zn/air battery applications (NORA). Final report

    Energy Technology Data Exchange (ETDEWEB)

    Thiele, D.; Zuettel, A.

    2008-04-15

    This illustrated final report for the Swiss Federal Office of Energy (SFOE) presents the results of a project concerning a new, highly active oxygen reduction electrode for PEM fuel cell and zinc/air battery applications. The goal of this project was, according to the authors, to increase the efficiency of the oxygen reduction reaction by lowering the activation polarisation through the right choice of catalyst and by lowering the concentration polarisation. In this work, carbon nanotubes are used as support material. The use of these nanotubes grown on perovskites is discussed. Theoretical considerations regarding activation polarisation are discussed and alternatives to the use of platinum are examined. The results of experiments carried out are presented in graphical and tabular form. The paper is completed with a comprehensive list of references.

  15. Water behavior in a U-shaped flow channel of PEM fuel cells. Paper no. IGEC-1-036

    Energy Technology Data Exchange (ETDEWEB)

    Quan, P.; Zhou, B.; Sobiesiak, A. [Univ. of Windsor, Dept. of Mechanical, Automotive and Materials Engineering, Windsor, Ontario (Canada)]. E-mail: bzhou@uwindsor.ca; Liu, Z.-S. [National Research Council Canada, Inst. for Fuel Cell innovation, Vancouver, British Columbia (Canada)

    2005-07-01

    The behavior of liquid water inside a U-shaped channel for a Proton Exchange Membrane (PEM) fuel cell was investigated through CFD modeling with the FLUENT software package. The Volume-Of-Fluid (VOF) model was adopted to track dynamic air-water interfaces. Three cases with varying initial water phase distributions corresponding to different fuel cell operating conditions were numerically simulated to obtain a better understanding of water behavior inside the serpentine channel. The results show that the bend area in the serpentine flow channel has significant effects on the flow field, which in turn affects the air-water flow and water liquid distribution inside the channel or along the interior channel surfaces, thus affecting fuel cell performance. (author)

  16. Solvent and acidification method effects in the performance of new sulfonated copolyimides membranes in PEM-fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Blazquez, J. Alberto; Iruin, Juan J.; Eceolaza, Sorkunde [Dpto. Ciencia y Tecnologia de Polimeros e Inst. de Materiales Polimericos (POLYMAT), UPV/EHU, M. de Lardizabal 3, 20018 San Sebastian (Spain); Marestin, Catherine; Mercier, Regis [Laboratoire des Materiaux Organiques a Proprietes Specifiques (LMOPS), CNRS-UMR 5041, BP24, 69390 Vernaison (France); Mecerreyes, David; Miguel, Oscar; Vela, Ana; Marcilla, Rebeca [CIDETEC, Centro de Tecnologias Electroquimicas, Paseo Miramon 196, 20009 San Sebastian (Spain)

    2005-10-10

    A series of new sequenced sulfonated naphthalenic polyimides were synthesized containing a flexible aromatic-aliphatic diamine. The obtained membranes present the advantage of being soluble in N-methyl pyrrolidone (NMP) which is a less toxic solvent than the previously used m-cresol. In this work, we report on the solvent and acidification method effects on the properties of the membranes such as density, water uptake, proton conductivity as well as on the performance of these membranes in fuel cell operation. The membranes prepared from NMP solution and acidified with ion-exchange resins give the best results. They have good mechanical properties as well as high ionic conductivity (14.4x10{sup -2}Scm{sup -1} at 80{sup o}C) and good performances as proton exchange membrane (PEM) in fuel cell at 70{sup o}C. (author)

  17. Evolutionary programming-based methodology for economical output power from PEM fuel cell for micro-grid application

    Science.gov (United States)

    El-Sharkh, M. Y.; Rahman, A.; Alam, M. S.

    This paper presents a methodology for finding the optimal output power from a PEM fuel cell power plant (FCPP). The FCPP is used to supply power to a small micro-grid community. The technique used is based on evolutionary programming (EP) to find a near-optimal solution of the problem. The method incorporates the Hill-Climbing technique (HCT) to maintain feasibility during the solution process. An economic model of the FCPP is used. The model considers the production cost of energy and the possibility of selling and buying electrical energy from the local grid. In addition, the model takes into account the thermal energy output from the FCPP and the thermal energy requirement for the micro-grid community. The results obtained are compared against a solution based on genetic algorithms. Results are encouraging and indicate viability of the proposed technique.

  18. Theoretical model with experimental validation of a regenerative blower for hydrogen recirculation in a PEM fuel cell system

    Energy Technology Data Exchange (ETDEWEB)

    Badami, M.; Mura, M. [Dipartimento di Energetica, Politecnico di Torino, C.so Duca degli Abruzzi 24, Torino (Italy)

    2010-03-15

    A theoretical model of a regenerative blower used for the hydrogen recirculation of a Proton Exchange Membrane (PEM) fuel cell (FC) for automotive applications has been implemented and validated by means of experimental data. A momentum exchange theory was used to determine the head-flow rate curves, whereas the circulatory flow rate was determined through a theory based on the consideration of the centrifugal force field in the side channel and in the impeller vane grooves. The model allows a good forecast to be made of the blower behaviour, and only needs its main geometrical characteristics and some fluid-dynamic data as input. For this reason, the model could be very interesting, especially during the first sizing and the design activity of the blower. (author)

  19. An algebra of reversible computation

    OpenAIRE

    2016-01-01

    We design an axiomatization for reversible computation called reversible ACP (RACP). It has four extendible modules, basic reversible processes algebra (BRPA), algebra of reversible communicating processes (ARCP), recursion and abstraction. Just like process algebra ACP in classical computing, RACP can be treated as an axiomatization foundation for reversible computation.

  20. An Algebra of Reversible Computation

    OpenAIRE

    Yong WANG

    2014-01-01

    We design an axiomatization for reversible computation called reversible ACP (RACP). It has four extendible modules, basic reversible processes algebra (BRPA), algebra of reversible communicating processes (ARCP), recursion and abstraction. Just like process algebra ACP in classical computing, RACP can be treated as an axiomatization foundation for reversible computation.

  1. An algebra of reversible computation.

    Science.gov (United States)

    Wang, Yong

    2016-01-01

    We design an axiomatization for reversible computation called reversible ACP (RACP). It has four extendible modules: basic reversible processes algebra, algebra of reversible communicating processes, recursion and abstraction. Just like process algebra ACP in classical computing, RACP can be treated as an axiomatization foundation for reversible computation.

  2. A CFD model for analysis of performance, water and thermal distribution, and mechanical related failure in PEM fuel cells

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2016-07-01

    Full Text Available This paper presents a comprehensive three–dimensional, multi–phase, non-isothermal model of a Proton Exchange Membrane (PEM fuel cell that incorporates significant physical processes and key parameters affecting the fuel cell performance. The model construction involves equations derivation, boundary conditions setting, and solution algorithm flow chart. Equations in gas flow channels, gas diffusion layers (GDLs, catalyst layers (CLs, and membrane as well as equations governing cell potential and hygro-thermal stresses are described. The algorithm flow chart starts from input of the desired cell current density, initialization, iteration of the equations solution, and finalizations by calculating the cell potential. In order to analyze performance, water and thermal distribution, and mechanical related failure in the cell, the equations are solved using a computational fluid dynamic (CFD code. Performance analysis includes a performance curve which plots the cell potential (Volt against nominal current density (A/cm2 as well as losses. Velocity vectors of gas and liquid water, liquid water saturation, and water content profile are calculated. Thermal distribution is then calculated together with hygro-thermal stresses and deformation. The CFD model was executed under boundary conditions of 20°C room temperature, 35% relative humidity, and 1 MPA pressure on the lower surface. Parameters values of membrane electrode assembly (MEA and other base conditions are selected. A cell with dimension of 1 mm x 1 mm x 50 mm is used as the object of analysis. The nominal current density of 1.4 A/cm2 is given as the input of the CFD calculation. The results show that the model represents well the performance curve obtained through experiment. Moreover, it can be concluded that the model can help in understanding complex process in the cell which is hard to be studied experimentally, and also provides computer aided tool for design and optimization of PEM

  3. Reversible Data Hiding Techniques

    Directory of Open Access Journals (Sweden)

    Dhananjay Yadav

    2012-03-01

    Full Text Available Reversible data hiding is a technique that is used to hide data inside an image. The data is hidden in such a way that the exact or original data is not visible. The hidden data can be retrieved as and when required. There are several methods that are used in reversible data hiding techniques like Watermarking, Lossless embedding and encryption. In this paper we present a review of reversible watermarking techniques and show different methods that are used to get reversible data hiding technique with higher embedding capacity and invisible objects. Watermark need not be hidden. Watermarking can be applied to 1. Images, 2. Text, 3. Audio/video, 4. Software.

  4. Reversible flowchart languages and the structured reversible program theorem

    DEFF Research Database (Denmark)

    Yokoyama, Tetsuo; Axelsen, Holger Bock; Glück, Robert

    2008-01-01

    Many irreversible computation models have reversible counterparts, but these are poorly understood at present. We introduce reversible flowcharts with an assertion operator and show that any reversible flowchart can be simulated by a structured reversible flowchart using only three control flow o...... justification for low-level machine code for reversible microprocessors as well as high-level block-structured reversible languages. We give examples for both such languages and illustrate them with a lossless encoder for permutations given by Dijkstra....

  5. Adaptive Pairing Reversible Watermarking.

    Science.gov (United States)

    Dragoi, Ioan-Catalin; Coltuc, Dinu

    2016-05-01

    This letter revisits the pairwise reversible watermarking scheme of Ou et al., 2013. An adaptive pixel pairing that considers only pixels with similar prediction errors is introduced. This adaptive approach provides an increased number of pixel pairs where both pixels are embedded and decreases the number of shifted pixels. The adaptive pairwise reversible watermarking outperforms the state-of-the-art low embedding bit-rate schemes proposed so far.

  6. A Reverse Osmosis System for an Advanced Separation Process Laboratory.

    Science.gov (United States)

    Slater, C. S.; Paccione, J. D.

    1987-01-01

    Focuses on the development of a pilot unit for use in an advanced separations process laboratory in an effort to develop experiments on such processes as reverse osmosis, ultrafiltration, adsorption, and chromatography. Discusses reverse osmosis principles, the experimental system design, and some experimental studies. (TW)

  7. Reverse Triangle Inequalities for Riesz Potentials and Connections with Polarization

    OpenAIRE

    Pritsker, I. E.; Saff, E. B.; Wise, W.

    2013-01-01

    We study reverse triangle inequalities for Riesz potentials and their connection with polarization. This work generalizes inequalities for sup norms of products of polynomials, and reverse triangle inequalities for logarithmic potentials. The main tool used in the proofs is the representation for a power of the farthest distance function as a Riesz potential of a unit Borel measure.

  8. A novel reversible carry-selected adder with low latency

    Science.gov (United States)

    Li, Ming-Cui; Zhou, Ri-Gui

    2016-07-01

    Reversible logic is getting more and more attention in quantum computing, optical computing, nanotechnology and low-power complementary metal oxide semiconductor designs since reversible circuits do not loose information during computation and have only small energy dissipation. In this paper, a novel carry-selected reversible adder is proposed primarily optimised for low latency. A 4-bit reversible full adder with two kinds of outputs, minimum delay and optimal quantum cost is presented as the building block for ?-bit reversible adder. Three new reversible gates NPG (new Peres gate), TEPG (triple extension of Peres gate) and RMUX21 (reversible 2-to-1 multiplexer) are proposed and utilised to design efficient adder units. The secondary carry propagation chain is carefully designed to reduce the time consumption. The novelty of the proposed design is the consideration of low latency. The comparative study shows that the proposed adder achieves the improvement from 61.46% to 95.29% in delay over the existing designs.

  9. Computer-based Reverse Engineering of a Manual Weighting ...

    African Journals Online (AJOL)

    PROF. O. E. OSUAGWU

    2013-06-01

    Jun 1, 2013 ... Keywords: Reverse Engineering, Weighting Spring balance, Systematic reconstruction, Digital interface, Digital ... Our body, food we eat and ... video display unit a corresponding and the ... structure, function, and operation.

  10. Final Project Report: Development of Micro-Structural Mitigation Strategies for PEM Fuel Cells: Morphological Simulations and Experimental Approaches

    Energy Technology Data Exchange (ETDEWEB)

    Wessel, Silvia [Ballard Materials Products; Harvey, David [Ballard Materials Products

    2013-06-28

    The durability of PEM fuel cells is a primary requirement for large scale commercialization of these power systems in transportation and stationary market applications that target operational lifetimes of 5,000 hours and 40,000 hours by 2015, respectively. Key degradation modes contributing to fuel cell lifetime limitations have been largely associated with the platinum-based cathode catalyst layer. Furthermore, as fuel cells are driven to low cost materials and lower catalyst loadings in order to meet the cost targets for commercialization, the catalyst durability has become even more important. While over the past few years significant progress has been made in identifying the underlying causes of fuel cell degradation and key parameters that greatly influence the degradation rates, many gaps with respect to knowledge of the driving mechanisms still exist; in particular, the acceleration of the mechanisms due to different structural compositions and under different fuel cell conditions remains an area not well understood. The focus of this project was to address catalyst durability by using a dual path approach that coupled an extensive range of experimental analysis and testing with a multi-scale modeling approach. With this, the major technical areas/issues of catalyst and catalyst layer performance and durability that were addressed are: 1. Catalyst and catalyst layer degradation mechanisms (Pt dissolution, agglomeration, Pt loss, e.g. Pt in the membrane, carbon oxidation and/or corrosion). a. Driving force for the different degradation mechanisms. b. Relationships between MEA performance, catalyst and catalyst layer degradation and operational conditions, catalyst layer composition, and structure. 2. Materials properties a. Changes in catalyst, catalyst layer, and MEA materials properties due to degradation. 3. Catalyst performance a. Relationships between catalyst structural changes and performance. b. Stability of the three-phase boundary and its effect on

  11. On thermodynamic and microscopic reversibility

    Energy Technology Data Exchange (ETDEWEB)

    Crooks, Gavin E.

    2011-07-12

    The word 'reversible' has two (apparently) distinct applications in statistical thermodynamics. A thermodynamically reversible process indicates an experimental protocol for which the entropy change is zero, whereas the principle of microscopic reversibility asserts that the probability of any trajectory of a system through phase space equals that of the time reversed trajectory. However, these two terms are actually synonymous: a thermodynamically reversible process is microscopically reversible, and vice versa.

  12. Design of a reversible single precision floating point subtractor.

    Science.gov (United States)

    Anantha Lakshmi, Av; Sudha, Gf

    2014-01-04

    In recent years, Reversible logic has emerged as a major area of research due to its ability to reduce the power dissipation which is the main requirement in the low power digital circuit design. It has wide applications like low power CMOS design, Nano-technology, Digital signal processing, Communication, DNA computing and Optical computing. Floating-point operations are needed very frequently in nearly all computing disciplines, and studies have shown floating-point addition/subtraction to be the most used floating-point operation. However, few designs exist on efficient reversible BCD subtractors but no work on reversible floating point subtractor. In this paper, it is proposed to present an efficient reversible single precision floating-point subtractor. The proposed design requires reversible designs of an 8-bit and a 24-bit comparator unit, an 8-bit and a 24-bit subtractor, and a normalization unit. For normalization, a 24-bit Reversible Leading Zero Detector and a 24-bit reversible shift register is implemented to shift the mantissas. To realize a reversible 1-bit comparator, in this paper, two new 3x3 reversible gates are proposed The proposed reversible 1-bit comparator is better and optimized in terms of the number of reversible gates used, the number of transistor count and the number of garbage outputs. The proposed work is analysed in terms of number of reversible gates, garbage outputs, constant inputs and quantum costs. Using these modules, an efficient design of a reversible single precision floating point subtractor is proposed. Proposed circuits have been simulated using Modelsim and synthesized using Xilinx Virtex5vlx30tff665-3. The total on-chip power consumed by the proposed 32-bit reversible floating point subtractor is 0.410 W.

  13. Effect of water temperature on reverse osmosis unit and countermeasures%水温对反渗透装置运行的影响及对策措施

    Institute of Scientific and Technical Information of China (English)

    陈乾荣; 何驹; 娄伦武; 王启延

    2015-01-01

    This paper sketches obvious effects of water temperature on operation pressure, desalination rate, pressure drop and producing water capacity, it also introduces producing water capacity in winter appears linear decrease with reduction of water temperature in reverse osmosis plants, through heating reverse osmosis feedwater with steam condensate, on condition of no-adding new device and energy consumption which solves producing water capacity low in winter, guaranteed efficiently water demand for follow-up devices.%简述了进水温度对反渗透装置的运行压力、脱盐率、压降以及产水能力影响极为明显,介绍该公司反渗透装置出现了冬季产水量随着水温降低而呈现线性下降的情况,通过换热装置用蒸汽冷凝液加热反渗透进水,在不增加新装置和能耗的前提下解决了冬季产水量少的问题,有效保障了后续装置的用水需求。

  14. A novel hybrid process of reverse electrodialysis and reverse osmosis for low energy seawater desalination and brine management

    NARCIS (Netherlands)

    Li, W.; Krantz, W.B.; Cornelissen, E.R.; Post, J.W.; Verliefde, A.R.D.; Tang, C.Y.

    2013-01-01

    This paper introduces a novel concept for a hybrid desalination system that combines reverse electrodialysis (RED) and reverse osmosis (RO) processes. In this hybrid process the RED unit harvests the energy in the form of electricity from the salinity gradient between a highly concentrated solution

  15. Develop High Efficiency Liquid-Feed PEM Electrolyzer Based on Integrated Flow Field (IFF) Structure Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Polymer electrolyte membrane water electrolysis units are currently designed to require active water flow and phase separation, or are based on a passive vapor...

  16. Reversible Communicating Processes

    Directory of Open Access Journals (Sweden)

    Geoffrey Brown

    2016-02-01

    Full Text Available Reversible distributed programs have the ability to abort unproductive computation paths and backtrack, while unwinding communication that occurred in the aborted paths. While it is natural to assume that reversibility implies full state recovery (as with traditional roll-back recovery protocols, an interesting alternative is to separate backtracking from local state recovery. For example, such a model could be used to create complex transactions out of nested compensable transactions where a programmer-supplied compensation defines the work required to "unwind" a transaction. Reversible distributed computing has received considerable theoretical attention, but little reduction to practice; the few published implementations of languages supporting reversibility depend upon a high degree of central control. The objective of this paper is to demonstrate that a practical reversible distributed language can be efficiently implemented in a fully distributed manner. We discuss such a language, supporting CSP-style synchronous communication, embedded in Scala. While this language provided the motivation for the work described in this paper, our focus is upon the distributed implementation. In particular, we demonstrate that a "high-level" semantic model can be implemented using a simple point-to-point protocol.

  17. Research of view invariant human action recognition based on fusion of projection depth vector decomposition and PEMS%投影深度向量分解融合 PEMS 的视角不变人体动作识别

    Institute of Scientific and Technical Information of China (English)

    杨建; 刘述木; 王晓林

    2016-01-01

    As the uncertainty of the inside camera parameter and hard to choose the projection plane,this paper proposed a new algorithm for the perspective projection depth invariant action recognition.The proposed algorithm used the strategy of planes extraction from mirror symmetry(PEMS),which was an effective solution to the projection plane choosing.Firstly,it observed a 3D postures by the camera group,and then used PEMS strategies to extract the plane from the scene,the plane es-timated projected depth of the body relatived to the extraction point,and finally used this information in action recognition. The core of proposed algorithm was to extract the depth of the projection plane and the solution of projection of the vector com-position.It obtained overall accuracies:94%,91%,and 90% with the proposed algorithm on the CMU MoCap data sets, TUMdata sets and the IXMAS data sets respectively.And it is still able to accurately define new actions in the case of small movements’instance.The proposed algorithm has better recognition performance for action recognition than several other ad-vanced algorithms.%针对摄像机内部参数的不确定性和投影平面选择难的问题,提出一种新的投影深度算法用于视角不变的动作识别,该算法采用对称镜面平面提取(plane extraction from mirror symmetry,PEMS)策略,有效解决了投影平面选择难的问题。首先通过摄像机组观察获得3D 动作姿势,然后运用 PEMS 策略从场景中提取平面,相对于提取平面估计身体点的投影深度,最后使用这个信息进行动作识别。该算法的核心是投影平面的提取和投影深度组成向量的求解。利用该算法在 CMU MoCap 数据集、TUM数据集和多视图 IXMAS 数据集上进行测试,精度可分别高达94%、91%和90%,且在较少动作实例情况下,仍然能够准确定义新动作。比较表明,该算法的人体动作识别性能明显优于其他几种较新的算法。

  18. A numerical study of the gas-liquid, two-phase flow maldistribution in the anode of a high pressure PEM water electrolysis cell

    DEFF Research Database (Denmark)

    Olesen, Anders Christian; Rømer, Carsten; Kær, Søren Knudsen

    2016-01-01

    In this work, the use of a circular-planar, interdigitated flow field for the anode of a high pressure proton exchange membrane (PEM) water electrolysis cell is investigated in a numerical study. While PEM fuel cells have separated flow fields for reactant transport and coolant, it is possible...... causes maldistribution, if land areas of equal width are applied. Moreover, below a water stoichiometry of 350, and at a current density of 1 A/cm2, flow and temperature maldistribution is adversely affected by the presence of the gas phase; particularly gas hold-up near outlet channels can cause...... excessive formation of hotspots. As the water stoichiometry increases, the flow maldistribution increases as well. Nonetheless, its impact on the temperature distribution is counterbalanced by an overall increase in heat capacity of the flow. Hence, a relative uniform temperature distribution is achieved...

  19. A Study of influence on sulfonated TiO2-Poly (Vinylidene fluoride-co-hexafluoropropylene) nano composite membranes for PEM Fuel cell application

    Science.gov (United States)

    kumar, K. Selva; Rajendran, S.; Prabhu, M. Ramesh

    2017-10-01

    The present work describes the sulfonated Titania directly blended with Poly (Vinylidene fluoride-co-hexafluoropropylene) as a host polymer by solvent casting technique for PEM fuel cell application. Characterization studies such as FT-IR, SEM, EDX, AFM, Proton conductivity, contact angle measurement, IEC, TG, water uptake, tensile strength were performed by for synthesized proton conducting polymer electrolytes. The maximum proton conductivity value was found to be 3.6 × 10-3S/cm for 25 wt% sulfonated Titania based system at 80 °C. The temperature dependent proton conductivity of the polymer electrolyte follows an Arrhenius relationship. Surface morphology of the composite membranes was investigated by tapping mode. Thermal stability of the system was studied by TG analysis. The fabricated composite membranes with high proton conductivity, good water uptake and IEC parameters exhibited a maximum fuel cell power density of 85 Mw/cm2for PEM fuel cell application.

  20. Manufacturing the Gas Diffusion Layer for PEM Fuel Cell Using a Novel 3D Printing Technique and Critical Assessment of the Challenges Encountered.

    Science.gov (United States)

    Jayakumar, Arunkumar; Singamneni, Sarat; Ramos, Maximiano; Al-Jumaily, Ahmed M; Pethaiah, Sethu Sundar

    2017-07-14

    The conventional gas diffusion layer (GDL) of polymer electrolyte membrane (PEM) fuel cells incorporates a carbon-based substrate, which suffers from electrochemical oxidation as well as mechanical degradation, resulting in reduced durability and performance. In addition, it involves a complex manufacturing process to produce it. The proposed technique aims to resolve both these issues by an advanced 3D printing technique, namely selective laser sintering (SLS). In the proposed work, polyamide (PA) is used as the base powder and titanium metal powder is added at an optimised level to enhance the electrical conductivity, thermal, and mechanical properties. The application of selective laser sintering to fabricate a robust gas diffusion substrate for PEM fuel cell applications is quite novel and is attempted here for the first time.

  1. Optimization Approaches for Designing a Novel 4-Bit Reversible Comparator

    Science.gov (United States)

    Zhou, Ri-gui; Zhang, Man-qun; Wu, Qian; Li, Yan-cheng

    2013-02-01

    Reversible logic is a new rapidly developed research field in recent years, which has been receiving much attention for calculating with minimizing the energy consumption. This paper constructs a 4×4 new reversible gate called ZRQ gate to build quantum adder and subtraction. Meanwhile, a novel 1-bit reversible comparator by using the proposed ZRQC module on the basis of ZRQ gate is proposed as the minimum number of reversible gates and quantum costs. In addition, this paper presents a novel 4-bit reversible comparator based on the 1-bit reversible comparator. One of the vital important for optimizing reversible logic is to design reversible logic circuits with the minimum number of parameters. The proposed reversible comparators in this paper can obtain superiority in terms of the number of reversible gates, input constants, garbage outputs, unit delays and quantum costs compared with the existed circuits. Finally, MATLAB simulation software is used to test and verify the correctness of the proposed 4-bit reversible comparator.

  2. Radiation controlling reversible window

    Energy Technology Data Exchange (ETDEWEB)

    Gell, H.A. Jr.

    1980-01-01

    A coated glass glazing system is presented including a transparent glass substrate having one surface coated with a radiation absorptive film which is overcoated with a radiation reflective film by a technique which renders the radiation reflective film radiation absorptive at the surface contracting the radiating absorptive film. The coated glass system is used as glazing for storm windows which are adapted to be reversible so that the radiation reflective surface may be exposed to the outside of the dwelling during the warm seasons to prevent excessive solar radiation from entering a dwelling and reversed during cold seasons to absorb solar radiation and utilize it to aid in keeping the dwelling interior warm.

  3. Neural Network-Based Modeling of PEM fuel cell and Controller Synthesis of a stand-alone system for residential application

    OpenAIRE

    Khaled Mammar; Abdelkader Chaker

    2012-01-01

    The paper is focused especially on presenting possibilities of applying artificial neural networks at creating the optimal model PEM fuel cell. Various ANN approaches have been tested; the back-propagation feed-forward networks show satisfactory performance with regard to cell voltage prediction. The model is then used in a power system for residential application. This models include an ANN fuel cell stack model, reformer model and DC/AC inverter model. Furthermore a neural network (NNTC) an...

  4. Sequential Polarity-Reversing Circuit

    Science.gov (United States)

    Labaw, Clayton C.

    1994-01-01

    Proposed circuit reverses polarity of electric power supplied to bidirectional dc motor, reversible electro-mechanical actuator, or other device operating in direction depending on polarity. Circuit reverses polarity each time power turned on, without need for additional polarity-reversing or direction signals and circuitry to process them.

  5. Application of lattice Boltzmann method to a micro-scale flow simulation in the porous electrode of a PEM fuel cell

    Science.gov (United States)

    Park, J.; Matsubara, M.; Li, X.

    The electrode of a PEM fuel cell is a porous medium generally made of carbon cloth or paper. Such a porous electrode has been widely modeled as a homogeneous porous medium with a constant permeability in the literature of PEM fuel cell. In fact, most of gas diffusion media are not homogeneous having non-isotropic permeability. In case of carbon cloth, the porous structure consists of carbon fiber tows, the bundles of carbon fiber, and void spaces among tows. The combinational effect of the void space and tow permeability results in the effective permeability of the porous electrode. In this work, the lattice Boltzmann method is applied to the simulation of the flow in the electrode of a PEM fuel cell. The electrode is modeled as void space and porous region which has certain permeability and the Stokes and Brinkman equations are solved in the flow field using the lattice Boltzmann model. The effective permeability of the porous medium is calculated and compared to an analytical calculation showing a good agreement. It has been shown that the permeability of porous medium is strongly dependant on the fiber tow orientation in three-dimensional simulations. The lattice Boltzmann method is an efficient and effective numerical scheme to analyze the flow in a complicated geometry such as the porous medium.

  6. A novel large signal and dynamic characterization to parameter a novel large signal and dynamic circuit model of a PEM fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Turpin, C.; Fontes, G.; Astier, S.; Arregui, M.G.; Phlippoteau, V. [LAPLACE - Laboratory Plasmas and Energy Conversion, Toulouse (France)

    2007-07-01

    An innovative large signal and dynamic circuit model of a proton exchange membrane (PEM) fuel cell was presented. It was developed from a generic approach that considers the energy exchange and the energy coupling within a fuel cell. This new model can be used to characterize a PEM fuel cell by exciting it with low frequency current sweeps whose amplitudes are high. It can be used for PEM fuel cells having activation; an electrochemical double layer; gas diffusion through the gas diffusion layer and the active layer; and ohmic losses. The proposed model is based on the theory of converting chemical energy into electrical energy, which is modelled by a voltage source. The activation phenomena and the gas diffusion phenomena are modeled by a current source in parallel with a capacity. The current source is piloted by the voltage which varies dynamically because of the associated capacitor. This paper describes the modelling steps in detail. It also proposed a parameter extraction method through experiments performed with a commercial PEMFC stack. It was concluded that both electrochemists and electrical engineers will be interested in this newly developed and validated model. 6 refs., 2 tabs., 8 figs.

  7. The use of a medical dictionary for regulatory activities terminology (MedDRA) in prescription-event monitoring in Japan (J-PEM).

    Science.gov (United States)

    Yokotsuka, M; Aoyama, M; Kubota, K

    2000-07-01

    The Medical Dictionary for Regulatory Activities Terminology (MedDRA) version 2.1 (V2.1) was released in March 1999 accompanied by the MedDRA/J V2.1J specifically for Japanese users. In prescription-event monitoring in Japan (J-PEM), we have employed the MedDRA/J for data entry, signal generation and event listing. In J-PEM, the lowest level terms (LLTs) in the MedDRA/J are used in data entry because the richness of LLTs is judged to be advantageous. A signal is generated normally at the preferred term (PT) level, but it has been found that various reporters describe the same event using descriptions that are potentially encoded by LLTs under different PTs. In addition, some PTs are considered too specific to generate the proper signal. In the system used in J-PEM, when an LLT is selected as a candidate to encode an event, another LLT under a different PT, if any, is displayed on the computer screen so that it may be coded instead of, or in addition to, the candidate LLT. The five-level structure of the MedDRA is used when listing events but some modification is required to generate a functional event list.

  8. Time reversal communication system

    Science.gov (United States)

    Candy, James V.; Meyer, Alan W.

    2008-12-02

    A system of transmitting a signal through a channel medium comprises digitizing the signal, time-reversing the digitized signal, and transmitting the signal through the channel medium. The channel medium may be air, earth, water, tissue, metal, and/or non-metal.

  9. Engineering Encounters: Reverse Engineering

    Science.gov (United States)

    McGowan, Veronica Cassone; Ventura, Marcia; Bell, Philip

    2017-01-01

    This column presents ideas and techniques to enhance your science teaching. This month's issue shares information on how students' everyday experiences can support science learning through engineering design. In this article, the authors outline a reverse-engineering model of instruction and describe one example of how it looked in our fifth-grade…

  10. Reverse Coherent Information

    Science.gov (United States)

    García-Patrón, Raúl; Pirandola, Stefano; Lloyd, Seth; Shapiro, Jeffrey H.

    2009-05-01

    In this Letter we define a family of entanglement distribution protocols assisted by feedback classical communication that gives an operational interpretation to reverse coherent information, i.e., the symmetric counterpart of the well-known coherent information. This leads to the definition of a new entanglement distribution capacity that exceeds the unassisted capacity for some interesting channels.

  11. Reversed extension flow

    DEFF Research Database (Denmark)

    Nielsen, Jens Kromann; Rasmussen, Henrik K.

    2008-01-01

    Afilament stretching rheometer (FSR) was used for measuring the start-up of uni-axial elongational flow followed by reversed bi-axial flow, both with a constant elongational rate. A narrow molecular mass distribution linear polystyrene with a molecular weight of 145 kg / mole wis subjected to the...

  12. REVERSE SUPPLY CHAIN

    Directory of Open Access Journals (Sweden)

    Tomasz DOMAGAŁA

    2013-10-01

    Full Text Available The paper focuses on the presentation of the reverse supply chain, of which the role in the modern business grows along with the increasing number of environmental regulations and possibilities of reducing an operating cost. The paper also describes main problems in developing the profitable chain and possibilities to take an action in order to overcome them.

  13. On reverse hypercontractivity

    CERN Document Server

    Mossel, Elchanan; Sen, Arnab

    2011-01-01

    We study the notion of reverse hypercontractivity. We show that reverse hypercontractive inequalities are implied by standard hypercontractive inequalities as well as by the modified log-Sobolev inequality. Our proof is based on a new comparison lemma for Dirichlet forms and an extension of the Strook-Varapolos inequality. A consequence of our analysis is that {\\em all} simple operators $L=Id-\\E$ as well as their tensors satisfy uniform reverse hypercontractive inequalities. That is, for all $qreverse hypercontractive inequalities established here imply new mixing and isoperimetric results for short random walks in product spaces, for certain card-shufflings, for Glauber dynamics in high-temperat...

  14. Reversing Discrimination: A Perspective

    Science.gov (United States)

    Pati, Gopal; Reilly, Charles W.

    1977-01-01

    Examines the debate over affirmative action and reverse discrimination, and discusses how and why the present dilemma has developed. Suggests that organizations can best address the problem through an honest, in-depth analysis of their organizational structure and management practices. (JG)

  15. Experimental and modeling investigations on the effects of electrode flooding on the performance of PEM fuel cells

    Science.gov (United States)

    Lin, Guangyu

    Electrode flooding, one of the major causes of poor performance of a proton exchange membrane (PEM) fuel cell, is still not fully understood. However, a comprehensive understanding of this phenomenon and the dynamics of water in the electrode is critical to the optimization of the performance of PEM fuel cells. Mathematical models were developed to study the effect of electrode flooding on the fuel cell performance. Experiments were also conducted to investigate the effect of the thickness and wetproof level of gas diffusion media on the electrode flooding level and cell performance. The modeling and experimental studies showed that liquid water accumulated in the gas diffusion and catalyst layers if it was not removed efficiently. Excessive liquid water accumulation could lead to electrode flooding and significantly impact the fuel cell performance. Any means that could facilitate liquid water removal from the cathode were found to enhance the cell performance. High operating temperature, high in-plane liquid water permeability of the gas diffusion layer, more channels and smaller shoulder widths were predicted to increase the fuel cell performance. The decrease in the in-plane electronic conductivity of the gas diffusion layer was not found to affect the fuel cell performance; however, a highly non-uniform distribution of the electronic current density was observed within the electrode. Excessive catalyst loading would not improve the fuel cell performance. On the contrary, it might reduce the fuel cell performance due to the increased thickness of the catalyst layer. Adding polytetrafluroethylene (PTFE) to the gas diffusion layer could enhance gas and water transport when a fuel cell operated under flooding situation. But excessive PTFE loading may make the electrodes more prone to flooding. It was also found that a thinner gas diffusion material without the microporous layer was more sensitive to water accumulation than a thicker one. Higher performance was

  16. Use of portable emissions measurement system (PEMS) for the development and validation of passenger car emission factors

    Science.gov (United States)

    Kousoulidou, Marina; Fontaras, Georgios; Ntziachristos, Leonidas; Bonnel, Pierre; Samaras, Zissis; Dilara, Panagiota

    2013-01-01

    This paper discusses the development and validation of passenger car emission factors, using real world operation data. In total, six passenger cars of different technologies were studied. The tested vehicles were operated under various driving conditions and over two different routes in the region of Lombardia, Italy. These routes were specifically defined in order to provide a range of driving conditions, including urban, rural and highway driving. Tailpipe emissions and exhaust gas flows were measured on-board the vehicle, using a portable emissions measurement system (PEMS). In addition, all vehicles were tested over the European type-approval driving cycle (NEDC) with the same PEMS equipment. The testing of gasoline vehicles showed that emissions are well below the emission standards and do not raise any concern. However, the testing of diesel vehicles both under real-world driving conditions and over the NEDC brought to the surface important concerns regarding the actual NOx emissions of modern diesel vehicles, since they seem to comply with the corresponding emission standard over the type-approval cycle, but they constantly exceed the specified limit when tested under real-world driving conditions. Results from real-world operation revealed that there is a significant deviation from the NOx emission standard limit (especially for the newly introduced Euro 5 technology). These observations raise concerns regarding the actual NOx emissions of modern vehicles and their impact on urban air-quality. The emission factors originally measured on the road are also compared to the corresponding COPERT average speed emission factors. In general, emissions of CO2, THC and CO correlate fairly well with COPERT, for all vehicles. In the case of NOx emissions, emission levels of the two tested Euro 5 diesel passenger cars are consistently higher in urban, rural, and highway driving compared to the corresponding COPERT emission factor. Thus, leading to the conclusion that

  17. Modelling and characterization of the PEM fuel cell to study interactions with power converters; Modelisation et caracterisation de la pile pem pour l'etude des interactions avec les convertisseurs statiques

    Energy Technology Data Exchange (ETDEWEB)

    Fontes, G.

    2005-09-15

    The climatic and energy challenges were now clearly stated. The use of hydrogen is one of the best ways which gives many hopes. Fuel cells are an essential link in the chain of the use of hydrogen. Thus, a lot of studies have been undertaken throughout the world on fuel cells in many fields of physics. Concerning the field of power electronics, a lot of work on distributed generation technologies using fuel cells has been realised too and a great number of power converters dedicated to fuel cells have been studied. However, very few studies have been undertaken on the interactions between fuel cells and power converters. The goals of this work are to study interactions between fuel cells and power converters. Some requirements for the power electronic engineer can follow from this work. This work proposes high signal dynamic models of a H{sub 2}/O{sub 2} PEM fuel cell. These models include the different physical and chemical phenomena. Specific methods based on a limited number of original experiments (low frequency current sweeps) allow to extract the model parameters. These models are used to study the interactions between fuel cells and power converters which are the most used: buck chopper, boost chopper, inverters. The important part of the double layer capacitors has thus been underlined: they can filter the current harmonics created by the power converters. Finally, some choices of filtering elements to be connected to the fuel cell are proposed. (author)

  18. Measurements of Acidic Gases and Aerosol Species Aboard the NASA DC-8 Aircraft During the Pacific Exploratory Mission in the Tropics (PEM-Tropics A)

    Science.gov (United States)

    Talbot, Robert W.; Dibb, Jack E.

    1999-01-01

    We received funding to provide measurements of nitric acid (HNO3), formic acid (HCOOH), acetic acid (CH3COOH), and the chemical composition of aerosols aboard the NASA Ames DC-8 research aircraft during the PEM-Tropics A mission. These measurements were successfully completed and the final data resides in the electronic archive (ftp-gte.larc.nasa.gov) at NASA Langley Research Center. For the PEM-Tropics A mission the University of New Hampshire group was first author of four different manuscripts. Three of these have now appeared in the Journal of Geophysical Research-Atmospheres, included in the two section sections on PEM-Tropics A. The fourth manuscript has just recently been submitted to this same journal as a stand alone paper. All four of these papers are included in this report. The first paper (Influence of biomass combustion emissions on the distribution of acidic trace gases over the Southern Pacific basin during austral springtime) describes the large-scale distributions of HNO3, HCOOH, and CH3COOH. Arguments were presented to show, particularly in the middle tropospheric region, that biomass burning emissions from South America and Africa were a major source of acidic gases over the South Pacific basin. The second paper (Aerosol chemical composition and distribution during the Pacific Exploratory Mission (PEM) Tropics) covers the aerosol aspects of our measurement package. Compared to acidic gases, O3, and selected hydrocarbons, the aerosol chemistry showed little influence from biomass burning emissions. The data collected in the marine boundary layer showed a possible marine source of NH3 to the troposphere in equatorial areas. This source had been speculated on previously, but our data was the first collected from an airborne platform to show its large-scale features. The third paper (Constraints on the age and dilution of Pacific Exploratory Mission-Tropics biomass burning plumes from the natural radionuclide tracer Pb-210) utilized the unexpectedly

  19. A Novel Reversible BCD Adder For Nanotechnology Based Systems

    Directory of Open Access Journals (Sweden)

    Majid Haghparast

    2008-01-01

    Full Text Available This paper proposes two reversible logic gates, HNFG and HNG. The first gate HNFG can be used as two Feynman Gates. It is suitable for a single copy of two bits with no garbage outputs. It can be used as “Copying Circuit” to increase fan-out because fan-out is not allowed in reversible circuits. The second gate HNG can implement all Boolean functions. It also can be used to design optimized adder architectures. This paper also proposes a novel reversible full adder. One of the prominent functionalities of the proposed HNG gate is that it can work singly as a reversible full adder unit. The proposed reversible full adder contains only one gate. We show that its hardware complexity is less than the existing reversible full adders. The proposed full adder is then applied to the design of a reversible 4-bit parallel adder. A reversible Binary Coded Decimal (BCD adder circuit is also proposed. The proposed circuit can add two 4-bit binary variables and it transforms the result into the appropriate BCD number using efficient error correction modules. We show that the proposed reversible BCD adder has lower hardware complexity and it is much better and optimized in terms of number of reversible gates and garbage outputs with compared to the existing counterparts.

  20. Characterization of a module with pixelated CdTe detectors for possible PET, PEM and compton camera applications

    Science.gov (United States)

    Ariño-Estrada, G.; Chmeissani, M.; de Lorenzo, G.; Puigdengoles, C.; Martínez, R.; Cabruja, E.

    2014-05-01

    We present the measurement of the energy resolution and the impact of charge sharing for a pixel CdTe detector. This detector will be used in a novel conceptual design for diagnostic systems in the field of nuclear medicine such as positron emission tomography (PET), positron emission mammography (PEM) and Compton camera. The detector dimensions are 10 mm × 10 mm × 2 mm and with a pixel pitch of 1 mm × 1 mm. The pixel CdTe detector is a Schottky diode and it was tested at a bias of -1000 V. The VATAGP7.1 frontend ASIC was used for the readout of the pixel detector and the corresponding single channel electronic noise was found to be σ < 2 keV for all the pixels. We have achieved an energy resolution, FWHM/Epeak, of 7.1%, 4.5% and 0.98% for 59.5, 122 and 511 keV respectively. The study of the charge sharing shows that 16% of the events deposit part of their energy in the adjacent pixel.

  1. In-situ diagnostic tools for hydrogen transfer leak characterization in PEM fuel cell stacks part II: Operational applications

    Science.gov (United States)

    Niroumand, Amir M.; Homayouni, Hooman; DeVaal, Jake; Golnaraghi, Farid; Kjeang, Erik

    2016-08-01

    This paper describes a diagnostic tool for in-situ characterization of the rate and distribution of hydrogen transfer leaks in Polymer Electrolyte Membrane (PEM) fuel cell stacks. The method is based on reducing the air flow rate from a high to low value at a fixed current, while maintaining an anode overpressure. At high air flow rates, the reduction in air flow results in lower oxygen concentration in the cathode and therefore reduction in cell voltages. Once the air flow rate in each cell reaches a low value at which the cell oxygen-starves, the voltage of the corresponding cell drops to zero. However, oxygen starvation results from two processes: 1) the electrochemical oxygen reduction reaction which produces current; and 2) the chemical reaction between oxygen and the crossed over hydrogen. In this work, a diagnostic technique has been developed that accounts for the effect of the electrochemical reaction on cell voltage to identify the hydrogen leak rate and number of leaky cells in a fuel cell stack. This technique is suitable for leak characterization during fuel cell operation, as it only requires stack air flow and voltage measurements, which are readily available in an operational fuel cell system.

  2. Estimation of the hydrogen flux from a PEM electrolyzer, based in the solar irradiation measured in Zacatecas Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Duron-Torres, S.M.; Villagrana-Munoz, L.E.; Garcia-Saldivar, V.M.; Escalante-Garcia, I.L. [Univ. Autonoma de Zacatecas, Zacatecas (Mexico). Unidad Academica de Ciencias Quimicas; Arriaga-Hurtado, L.G. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, Pedro Escobedo (Mexico)

    2010-07-15

    The current cost of obtaining hydrogen from electrolyzers is higher than the cost of producing fossil fuels. However, with advances in technology and greater use of alternative energy sources, the cost of electrolytic hydrogen production may decrease to the point of being competitive. This study calculated how much hydrogen can be produced in a typical polymer exchange membrane (PEM) electrolyzer. Local solar irradiation measurements were carried out from November 2007 to April 2008 at the Campus Siglo 21 Solarimetric Station at Zacatecas University in Mexico. The mean irradiation measured was 6.6 kW-h per m{sup 2}. Based on the solar data obtained at the station, the hydrogen produced by a typical solar-hydrogen (SH) system was evaluated. The study showed that an important quantity of hydrogen as an energy vector could be obtained from solar radiation. April was determined to be the month of maximum hydrogen production. The lowest hydrogen production was in November. The data obtained during this study can be used to evaluate the solar renewable energy resource expressed as hydrogen production. 19 refs., 1 tab., 4 figs.

  3. Research and development of proton-exchange membrane (PEM) fuel cell system for transportation applications. Phase I final report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-01-01

    Objective during Phase I was to develop a methanol-fueled 10-kW fuel cell power source and evaluate its feasibility for transportation applications. This report documents research on component (fuel cell stack, fuel processor, power source ancillaries and system sensors) development and the 10-kW power source system integration and test. The conceptual design study for a PEM fuel cell powered vehicle was documented in an earlier report (DOE/CH/10435-01) and is summarized herein. Major achievements in the program include development of advanced membrane and thin-film low Pt-loaded electrode assemblies that in reference cell testing with reformate-air reactants yielded performance exceeding the program target (0.7 V at 1000 amps/ft{sup 2}); identification of oxidation catalysts and operating conditions that routinely result in very low CO levels ({le} 10 ppm) in the fuel processor reformate, thus avoiding degradation of the fuel cell stack performance; and successful integrated operation of a 10-kW fuel cell stack on reformate from the fuel processor.

  4. Platinized Graphene/ceramics Nano-sandwiched Architectures and Electrodes with Outstanding Performance for PEM Fuel Cells.

    Science.gov (United States)

    Chen, Xu; He, Daping; Wu, Hui; Zhao, Xiaofeng; Zhang, Jian; Cheng, Kun; Wu, Peng; Mu, Shichun

    2015-11-05

    For the first time a novel oxygen reduction catalyst with a 3D platinized graphene/nano-ceramic sandwiched architecture is successfully prepared by an unusual method. Herein the specific gravity of graphene nanosheets (GNS) is tailored by platinizing graphene in advance to shorten the difference in the specific gravity between carbon and SiC materials, and then nano-SiC is well intercalated into GNS interlayers. This nano-architecture with highly dispersed Pt nanoparticles exhibits a very high oxygen reduction reaction (ORR) activity and polymer electrolyte membrane (PEM) fuel cell performance. The mass activity of half cells is 1.6 times of that of the GNS supported Pt, and 2.4 times that of the commercial Pt/C catalyst, respectively. Moreover, after an accelerated stress test our catalyst shows a predominantly electrochemical stability compared with benchmarks. Further fuel cell tests show a maximum power density as high as 747 mW/cm(2) at low Pt loading, which is more than 2 times higher than that of fuel cells with the pristine graphene electrode.

  5. An Innovative Hybrid 3D Analytic-Numerical Approach for System Level Modelling of PEM Fuel Cells

    Directory of Open Access Journals (Sweden)

    Gregor Tavčar

    2013-10-01

    Full Text Available The PEM fuel cell model presented in this paper is based on modelling species transport and coupling electrochemical reactions to species transport in an innovative way. Species transport is modelled by obtaining a 2D analytic solution for species concentration distribution in the plane perpendicular to the gas-flow and coupling consecutive 2D solutions by means of a 1D numerical gas-flow model. The 2D solution is devised on a jigsaw puzzle of multiple coupled domains which enables the modelling of parallel straight channel fuel cells with realistic geometries. Electrochemical and other nonlinear phenomena are coupled to the species transport by a routine that uses derivative approximation with prediction-iteration. A hybrid 3D analytic-numerical fuel cell model of a laboratory test fuel cell is presented and evaluated against a professional 3D computational fluid dynamic (CFD simulation tool. This comparative evaluation shows very good agreement between results of the presented model and those of the CFD simulation. Furthermore, high accuracy results are achieved at computational times short enough to be suitable for system level simulations. This computational efficiency is owed to the semi-analytic nature of its species transport modelling and to the efficient computational coupling of electrochemical kinetics and species transport.

  6. The influence of iridium chemical oxidation state on the performance and durability of oxygen evolution catalysts in PEM electrolysis

    Science.gov (United States)

    Siracusano, S.; Baglio, V.; Grigoriev, S. A.; Merlo, L.; Fateev, V. N.; Aricò, A. S.

    2017-10-01

    Nanosized Ir-black (3 nm) and Ir-oxide (5 nm) oxygen evolution electrocatalysts showing high performance in polymer electrolyte membrane (PEM) water electrolysis based on Aquivion® short-side chain ionomer membrane are investigated to understand the role of the Ir oxidation state on the electrocatalytic activity and stability. Despite the smaller mean crystallite size, the Ir-black electrocatalyst shows significantly lower initial performance than the Ir-oxide. During operation at high current density, the Ir-black shows a decrease of cell potential with time whereas the Ir-oxide catalyst shows increasing cell potential resulting in a degradation rate of about 10 μV/h, approaching 1000 h. The unusual behaviour of the Ir-black results from the oxidation of metallic Ir to IrOx. The Ir-oxide catalyst shows instead a hydrated structure on the surface and a negative shift of about 0.5 eV for the Ir 4f binding energy after 1000 h electrolysis operation. This corresponds to the formation of a sub-stoichiometric Ir-oxide on the surface. These results indicate that a hydrated IrO2 with high oxidation state on the surface is favourable in decreasing the oxygen evolution overpotential. Modifications of the Ir chemical oxidation state during operation can affect significantly the catalytic activity and durability of the electrolysis system.

  7. A parametric study of cathode catalyst layer structural parameters on the performance of a PEM fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Khajeh-Hosseini-Dalasm, N.; Kermani, M.J.; Moghaddam, D. Ghadiri [Department of Mechanical Engineering, Energy Conversion Research Laboratory, and The New Technologies Research Center, 424 Hafez Avenue, Amirkabir University of Technology (Tehran Polytechnic), Tehran 15875-4413 (Iran); Stockie, J.M. [Department of Mathematics, Simon Fraser University, Burnaby, BC (Canada)

    2010-03-15

    This paper is a computational study of the cathode catalyst layer (CL) of a proton exchange membrane fuel cell (PEMFC) and how changes in its structural parameters affect performance. The underlying mathematical model assumes homogeneous and steady-state conditions, and consists of equations that include the effects of oxygen diffusion, electrochemical reaction rates, and transport of protons and electrons through the Nafion ionomer (PEM) and solid phases. Simulations are concerned with the problem of minimizing activation overpotential for a given current density. The CL consists of four phases: ionomer, solid substrate, catalyst particles and void spaces. The void spaces are assumed to be fully flooded by liquid water so that oxygen within the CL can diffuse to reaction sites via two routes: within the flooded void spaces and dissolved within the ionomer phase. The net diffusive flux of oxygen through the cathode CL is obtained by incorporating these two diffusive fluxes via a parallel resistance type model. The effect of six structural parameters on the CL performance is considered: platinum and carbon mass loadings, ionomer volume fraction, the extent to which the gas diffusion layer (GDL) extends into the CL, the GDL porosity and CL thickness. Numerical simulations demonstrate that the cathode CL performance is most strongly affected by the ionomer volume fraction, CL thickness and carbon mass loading. These results give useful guidelines for manufactures of PEMFC catalyst layers. (author)

  8. Micro reactor integrated μ-PEM fuel cell system: a feed connector and flow field free approach

    Science.gov (United States)

    Balakrishnan, A.; Mueller, C.; Reinecke, H.

    2013-12-01

    A system level microreactor concept for hydrogen generation with Sodium Borohydride (NaBH4) is demonstrated. The uniqueness of the system is the transport and distribution feature of fuel (hydrogen) to the anode of the fuel cell without any external feed connectors and flow fields. The approach here is to use palladium film instead of feed connectors and the flow fields; palladium's property to adsorb and desorb the hydrogen at ambient and elevated condition. The proof of concept is demonstrated with a polymethyl methacrylate (PMMA) based complete system integration which includes microreactor, palladium transport layer and the self-breathing polymer electrolyte membrane (PEM) fuel cell. The hydrolysis of NaBH4 was carried out in the presence of platinum supported by nickel (NiPt). The prototype functionality is tested with NaBH4 chemical hydride. The characterization of the integrated palladium layer and fuel cell is tested with constant and switching load. The presented integrated fuel cell is observed to have a maximum power output and current of 60 mW and 280 mA respectively.

  9. Gas and water management system in a 5 kW PEM fuel cell stack%5 kW质子交换膜燃料电池堆之气体与水管理系统

    Institute of Scientific and Technical Information of China (English)

    马小康; 郑为阳; 方富民

    2012-01-01

    A gas and water management system has been developed to increase the performance of the 5 kW proton exchange membrane fuel cell stack used for a small on board PEMFC auxiliary power unit(APU).The gas and water management system included four subsystems: oxidant supply subsystem,hydrogen supply subsystem,water cooling subsystem and control subsystem.The original design combined with excessive sensors and over-length pipes would cause the higher heat dissipation and decrease the inlet air temperature.The new compact design with less sensors and shorter pipe length could keep the higher inlet gas flow temperature and better performance of the fuel cell stack.In addition,stack performance could be influenced by the gas relative humidity and the hydrogen consumption under different loads.Hydrogen consumption under high load of 100 A might have 1.44 times more than that under low load of 10 A.Thus,the analysis of the hydrogen consumption under different loads and the gas relative humidity could help us to have an optimal design of the hydrogen recycling and increase the stack efficiency.Another 5 kW PEM fuel cell stack system is fabricated to couple with the original fuel cell stack system to have a 10 kW power output.The two stacks are electrically parallel or cascade;and the diodes are adopted in the circuit to avoid reverse current.The whole system should deliver a high power output stably in a long time because the performances of the two stacks are controlled to be almost identical to one another.The experimental results show that the stack ideal efficiency could reach 65.5% under the input air temperature of 51℃ and relative humidity of 54%.%开发了一个气体与水管理系统,藉以配合5kW质子交换膜燃料电池堆(Ballard 1310),使燃料电池的发电效率提升,并应用在小型运输工具之辅助动力装置(APU).气体与水管理系统包含4个子系统:氧化物供应系统、氢气供应系统、冷却系统与控制系统.

  10. Reversible quantum cellular automata

    CERN Document Server

    Schumacher, B

    2004-01-01

    We define quantum cellular automata as infinite quantum lattice systems with discrete time dynamics, such that the time step commutes with lattice translations and has strictly finite propagation speed. In contrast to earlier definitions this allows us to give an explicit characterization of all local rules generating such automata. The same local rules also generate the global time step for automata with periodic boundary conditions. Our main structure theorem asserts that any quantum cellular automaton is structurally reversible, i.e., that it can be obtained by applying two blockwise unitary operations in a generalized Margolus partitioning scheme. This implies that, in contrast to the classical case, the inverse of a nearest neighbor quantum cellular automaton is again a nearest neighbor automaton. We present several construction methods for quantum cellular automata, based on unitaries commuting with their translates, on the quantization of (arbitrary) reversible classical cellular automata, on quantum c...

  11. Partial Reversible Gates(PRG) for Reversible BCD Arithmetic

    CERN Document Server

    Thapliyal, Himanshu; Bajpai, Rajnish; Sharma, Kamal K

    2007-01-01

    IEEE 754r is the ongoing revision to the IEEE 754 floating point standard and a major enhancement to the standard is the addition of decimal format. Furthermore, in the recent years reversible logic has emerged as a promising computing paradigm having its applications in low power CMOS, quantum computing, nanotechnology, and optical computing. The major goal in reversible logic is to minimize the number of reversible gates and garbage outputs. Thus, this paper proposes the novel concept of partial reversible gates that will satisfy the reversibility criteria for specific cases in BCD arithmetic. The partial reversible gate is proposed to minimize the number of reversible gates and garbage outputs, while designing the reversible BCD arithmetic circuits.

  12. Reversible hysteresis loop tuning

    Science.gov (United States)

    Berger, A.; Binek, Ch.; Margulies, D. T.; Moser, A.; Fullerton, E. E.

    2006-02-01

    We utilize antiferromagnetically coupled bilayer structures to magnetically tune hysteresis loop properties. Key element of this approach is the non-overlapping switching field distribution of the two magnetic layers that make up the system: a hard magnetic CoPtCrB layer (HL) and a soft magnetic CoCr layer (SL). Both layers are coupled antiferromagnetically through an only 0.6-nm-thick Ru interlayer. The non-overlapping switching field distribution allows the measurement of magnetization reversal in the SL at low fields while keeping the magnetization state of the HL unperturbed. Applying an appropriate high field or high field sequence changes the magnetic state of the HL, which then influences the SL magnetization reversal due to the interlayer coupling. In this way, the position and shape of the SL hysteresis loop can be changed or tuned in a fully reversible and highly effective manner. Here, we study specifically how the SL hysteresis loop characteristics change as we move the HL through an entire high field hysteresis loop sequence.

  13. Reversible multi-head finite automata characterize reversible logarithmic space

    DEFF Research Database (Denmark)

    Axelsen, Holger Bock

    2012-01-01

    Deterministic and non-deterministic multi-head finite automata are known to characterize the deterministic and non- deterministic logarithmic space complexity classes, respectively. Recently, Morita introduced reversible multi-head finite automata (RMFAs), and posed the question of whether RMFAs...... characterize reversible logarithmic space as well. Here, we resolve the question affirmatively, by exhibiting a clean RMFA simulation of logarithmic space reversible Turing machines. Indirectly, this also proves that reversible and deterministic multi-head finite automata recognize the same languages....

  14. [Reverse Chaddock sign].

    Science.gov (United States)

    Tashiro, Kunio

    2011-08-01

    It is widely accepted that the Babinski reflex is the most well-known and important pathological reflex in clinical neurology. Among many other pathological reflexes that elicit an upgoing great toe, such as Chaddock, Oppenheim, Gordon, Schaefer, and Stransky, only the Chaddock reflex is said to be as sensitive as the Babinski reflex. The optimal receptive fields of the Babinski and Chaddock reflexes are the lateral plantar surface and the external inframalleolar area of the dorsum, respectively. It has been said that the Babinski reflex, obtained by stroking the sole, is by far the best and most reliable method of eliciting an upgoing great toe. However, the Chaddock reflex, the external malleolar sign, is also considered sensitive and reliable according to the literature and everyday neurological practice. The major problems in eliciting the Babinski reflex by stroking the lateral part of the sole are false positive or negative responses due to foot withdrawal, tonic foot response, or some equivocal movements. On the other hand, according to my clinical experience, the external inframalleolar area, which is the receptive field of the Chaddock reflex, is definitely suitable for eliciting the upgoing great toe. In fact, the newly proposed method to stimulate the dorsum of the foot from the medial to the lateral side, which I term the "reversed Chaddock method," is equally sensitive to demonstrate pyramidal tract involvement. With the "reversed Chaddock method", the receptive field of the Chaddock reflex may be postulated to be in the territory of the sural nerve, which could be supported by the better response obtained on stimulation of the postero-lateral calf than the anterior shin. With regard to the receptive fields of the Babinski and Chaddock reflexes, the first sacral dermatome (S1) is also considered a reflexogenous zone, but since the dermatome shows marked overlapping, the zones vary among individuals. As upgoing toe responses are consistently observed in

  15. A Semi-Empirical Two Step Carbon Corrosion Reaction Model in PEM Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Young, Alan; Colbow, Vesna; Harvey, David; Rogers, Erin; Wessel, Silvia

    2013-01-01

    The cathode CL of a polymer electrolyte membrane fuel cell (PEMFC) was exposed to high potentials, 1.0 to 1.4 V versus a reversible hydrogen electrode (RHE), that are typically encountered during start up/shut down operation. While both platinum dissolution and carbon corrosion occurred, the carbon corrosion effects were isolated and modeled. The presented model separates the carbon corrosion process into two reaction steps; (1) oxidation of the carbon surface to carbon-oxygen groups, and (2) further corrosion of the oxidized surface to carbon dioxide/monoxide. To oxidize and corrode the cathode catalyst carbon support, the CL was subjected to an accelerated stress test cycled the potential from 0.6 VRHE to an upper potential limit (UPL) ranging from 0.9 to 1.4 VRHE at varying dwell times. The reaction rate constants and specific capacitances of carbon and platinum were fitted by evaluating the double layer capacitance (Cdl) trends. Carbon surface oxidation increased the Cdl due to increased specific capacitance for carbon surfaces with carbon-oxygen groups, while the second corrosion reaction decreased the Cdl due to loss of the overall carbon surface area. The first oxidation step differed between carbon types, while both reaction rate constants were found to have a dependency on UPL, temperature, and gas relative humidity.

  16. Habitat Demonstration Unit Project: Leadership and Management Strategies for a Rapid Prototyping Project

    Science.gov (United States)

    Kennedy, Kriss J.; Toup, Larry; Gill, Tracy; Tri, Terry; Howe, Scott; Smitherman, David

    2011-01-01

    This paper gives an overview of the National Aeronautics and Space Administration (NASA) led multi-center Habitat Demonstration Unit (HDU) project leadership and management strategies being used by the NASA HDU team for a rapid prototyping project. The HDU project team constructed and tested an analog prototype lunar surface habitat/laboratory called the Pressurized Excursion Module (PEM) during 2010. The prototype unit subsystems were integrated in a short amount of time, utilizing a tiger team rapid prototyping approach that brought together over 20 habitation-related technologies and innovations from a variety of NASA centers. This paper describes the leadership and management strategies as well as lessons learned pertaining to leading and managing a multi-center diverse team in a rapid prototype environment. The PEM configuration went from a paper design to an operational surface habitat demonstration unit in less than 12 months. The HDU project is part of the strategic plan from the Exploration Systems Mission Directorate (ESMD) Directorate Integration Office (DIO) and the Exploration Mission Systems Office (EMSO) to test destination elements in analog environments. The 2011 HDU-Deep Space Habitat (DSH) configuration will build upon the PEM work, and emphasize validity of crew operations (remote working and living), EVA operations, mission operations, logistics operations, and science operations that might be required in a deep space context for Near Earth Object (NEO) exploration mission architectures. The 2011 HDU-DSH will be field-tested during the 2011 Desert Research and Technologies Studies (DRaTS) field tests. The HDU project is a "technology-pull" project that integrates technologies and innovations from multiple NASA centers. This project will repurpose the HDU 2010 demo unit that was field tested in the 2010 DRaTS, adding habitation functionality to the prototype unit. This paper will describe the strategy of establishing a multi-center project

  17. Reversible paraneoplastic encephalomyelitis as the presenting feature of ovarian teratoma: A clinicopathological correlate

    Directory of Open Access Journals (Sweden)

    Rajappa Senthil

    2007-01-01

    Full Text Available Paraneoplastic encephalomyelitis (PEM is a well-characterized neurological syndrome. Its association with ovarian teratoma is rare. A young lady presented with features suggestive of encephalomyelitis with predominant cerebellar syndrome. Magnetic resonance imaging brain was normal. Cerebrospinal fluid showed lymphocytic pleocytosis. Computerized tomography scan of the pelvis revealed a complex left ovarian cyst. With a clinical diagnosis of PEM she underwent a left salpingo-oopherectomy. This was followed by total recovery of the PEM in two weeks. The histopathology revealed immature teratoma. The interesting feature was the clinicopathological correlation between the finding of fetal cerebellar tissue in the tumor and the PEM with predominant cerebellar features.

  18. Experimental study of cell reversal of a high temperature polymer electrolyte membrane fuel cell caused by H2 starvation

    DEFF Research Database (Denmark)

    Zhou, Fan; Andreasen, Søren Juhl; Kær, Søren Knudsen

    2015-01-01

    Operation under fuel starvation has been proved to be harmful to the fuel cell by causing severe and irreversible degradation. To characterize the behaviors of the high temperature PEM fuel cell under fuel starvation conditions, the cell voltage and local current density is measured simultaneously...... under different H2 stoichiometries below 1.0 and at different current loads. The experimental results show that the cell voltage decreases promptly when the H2 stoichiometry decreases to below 1.0. Negative cell voltage can be observed which indicates cell reversal. The local current density starts...... to diverge when the cell voltage decreases. In the H2 upstream regions the current densities show an increasing trend, while those in the H2 downstream regions show a decreasing trend. Consequently, the current density distribution becomes very uneven. The current density is the highest in the upstream...

  19. Demonstration of a residential CHP system based on PEM fuel cells

    Science.gov (United States)

    Gigliucci, G.; Petruzzi, L.; Cerelli, E.; Garzisi, A.; La Mendola, A.

    Fuel cell-based CHP systems are very attractive for stationary energy generation, since they allow production of electricity and heat in a decentralised, quiet, efficient and environmentally friendly way. As a means of evaluating this new technology, Enel Produzione installed a beta-version fuel cell CHP system, supplied by H-Power, at its experimental area sited in Livorno (Italy), and submitted it to a series of tests. The system is a co-generative unit, converting natural gas into electricity and heat: the former is delivered to local loads using electric load following capability; the latter is delivered to the experimental area hydraulic refrigeration circuit. Experiments were aimed at assessing the suitability of this kind of system to supply Italian residential customers. Factors such as performances, flexibility and operational requirements were evaluated under all the possible operating conditions, both under grid connected and stand alone configurations. At the same time, a mathematical model of the FC/CHP unit was developed to allow for the prediction of system performances and operating parameters under off-design conditions. This model can be used as an effective tool to optimise system operation when a particular customer has to be supplied. Results show that the prototype behaved as expected by a first "proof of concept" system and outline improvements to be achieved in order to satisfy the energy needs of small residential applications.

  20. Study of a small heat and power PEM fuel cell system generator

    Science.gov (United States)

    Hubert, Charles-Emile; Achard, Patrick; Metkemeijer, Rudolf

    A micro-cogenerator based on a natural gas reformer and a PEMFC is studied in its entirety, pointing out the links between different sub-systems. The study is conducted within the EPACOP project, which aims at testing PEMFC systems on user sites to evaluate development and acceptance of this technology for small stationary applications. Five units were installed from November 2002 to May 2003 and have been operated until now, in real life conditions. They deliver up to 4 kW of AC power and about 6 kW of heat. Center for Energy and Processes (CEP), one of the scientific partners, processes and analyses the experimental data from the five units, running in different regions of France. This database and the study of the flowsheet enable to propose changes to enhance the efficiency of the system composed of a steam reforming, a shift and a preferential oxidation reactor, a fuel cell stack and heat exchangers. The steady state modelling and optimisation of the system is done with Thermoptim ®, a software developed within CEP for applied thermodynamics. At constant power, main targets are to decrease natural gas consumption, to increase heat recovery and to improve the water balance. This study is made using the pinch point analysis, at full load and partial load. Main results of this study are different system configurations that allow improvement of gross electrical and thermal efficiency and enable to obtain a positive water balance.

  1. Study of the flooding and dehydration processes of a PEM fuel cell using the EIS technique; Estudio de los procesos de inundacion y deshidratacion en una celda de combustible tipo PEM mediante la tecnica EIS

    Energy Technology Data Exchange (ETDEWEB)

    Loyola-Morales, F.; Cano-Castillo, U. [Instituto de Investigaciones Electricas, Cuernavaca, Morelos (Mexico)]. E-mail: feloyola@yahoo.com.mx

    2009-09-15

    In this work, a study was conducted of the flooding and dehydration processes of a PEM fuel cell using the EIS technique. The experiments were conducted in a 50 cm{sup 2} cell. The gradual flooding of the system was induced by operating the cell at a potential of 0.3 V and maintaining the gas outlet closed (that is, stoichiometry of 1 for the anode (H{sub 2}) and the cathode (O{sub 2})) to enable the water produced by the reaction to accumulate inside. The gradual dehydration was induced by operating the cell at a potential of 0.3V and establishing a oxidized gas flow at a stoichiometry of 4. EIS tests were applied throughout both processes. The results showed that the EIS technique is highly sensitive for the analysis of the different degrees of the flooding processes by monitoring variations in the imaginary components of total impedance (Z{sup )} or the phase angle ({theta}). For low degrees of flooding, the technique had good sensitivity, between 1 and 6 Hz, while at high degrees of flooding the technique's greatest sensitivity was limited to a range between 1 and 2 Hz. In the case of the dehydration process of the system, the results showed that this type of process can be analyzed for variations in the value of the real component (Z{sup '}) as well as for the imaginary component of total impedance and variations in the phase angle. The analysis of dehydration with Z{sup '} was possible at a rather wide range, from 100 to 1000 Hz; with Z{sup }or {theta} it was only possible at a range of 20 to 200 Hz. [Spanish] En el presente trabajo, se llevo a cabo el estudio de los procesos de inundacion y deshidratacion de una celda de combustible tipo PEM mediante la tecnica EIS. Los experimentos fueron realizados en una celda de 50 cm{sup 2}. La inundacion gradual del sistema se indujo operando la celda a un potencial de 0.3 V de celda y manteniendo la salida de gases cerrada (i. e. estequiometria de 1 tanto en anodo (H{sub 2}) como en catodo (O{sub 2

  2. Reverse Engineering of RFID devices

    OpenAIRE

    Bokslag, Wouter

    2015-01-01

    This paper discusses the relevance and potential impact of both RFID and reverse engineering of RFID technology, followed by a discussion of common protocols and internals of RFID technology. The focus of the paper is on providing an overview of the different approaches to reverse engineering RFID technology and possible countermeasures that could limit the potential of such reverse engineering attempts.

  3. Efficient Reversible Montgomery Multiplier and Its Application to Hardware Cryptography

    Directory of Open Access Journals (Sweden)

    Noor M. Nayeem

    2009-01-01

    Full Text Available Problem Statement: Arithmetic Logic Unit (ALU of a crypto-processor and microchips leak information through power consumption. Although the cryptographic protocols are secured against mathematical attacks, the attackers can break the encryption by measuring the energy consumption. Approach: To thwart attacks, this study proposed the use of reversible logic for designing the ALU of a crypto-processor. Ideally, reversible circuits do not dissipate any energy. If reversible circuits are used, then the attacker would not be able to analyze the power consumption. In order to design the reversible ALU of a crypto-processor, reversible Carry Save Adder (CSA using Modified TSG (MTSG gates and architecture of Montgomery multiplier were proposed. For reversible implementation of Montgomery multiplier, efficient reversible multiplexers and sequential circuits such as reversible registers and shift registers were presented. Results: This study showed that modified designs perform better than the existing ones in terms of number of gates, number of garbage outputs and quantum cost. Lower bounds of the proposed designs were established by providing relevant theorems and lemmas. Conclusion: The application of reversible circuit is suitable to the field of hardware cryptography.

  4. Reverse Engineering Malicious Applications

    Directory of Open Access Journals (Sweden)

    Ioan Cristian Iacob

    2015-06-01

    Full Text Available Detecting new and unknown malware is a major challenge in today’s software. Security profession. A lot of approaches for the detection of malware using data mining techniques have already been proposed. Majority of the works used static features of malware. However, static detection methods fall short of detecting present day complex malware. Although some researchers proposed dynamic detection methods, the methods did not use all the malware features. In this work, an approach for the detection of new and unknown malware was proposed and implemented. Each sample was reverse engineered for analyzing its effect on the operating environment and to extract the static and behavioral features. 

  5. The development and characterization of gas diffusion layers for a PEM fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Jhuly Nascimento dos; Kunst, Sandra Raquel; Malfatti, Celia de Fraga; Amico, Sandro Campos [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil)], Email: Jhuly.nascimento@gmail.com

    2010-07-01

    The need for electrical power generation with minimal environmental impact has driven the development of new systems for energy conversion, such as fuel cells. However, the short life of components and their high cost have limited the production of these devices. The fundamental unit of a PEMFC fuel cell consists of a gas diffusion layer (GDL), a catalyst layer and a polymeric membrane. The GDL drives the flow of gas to the catalytic layer and must possess suitable characteristics with respect to porosity, conductivity, hydrophobicity and chemical stability. In this work, a GDL for low-temperature fuel cells was produced from a suspension containing short carbon fibers in PVA or acrylic water-based resin. The obtained GDL was characterized via wettability and conductivity tests. Besides, the GDL morphology was analyzed by scanning electron microscopy. (author)

  6. Synthesis of protons exchange polymeric membranes via co-poly-esters doped with sodium dodecyl sulfate for application in PEM fuel cells; Sintese de membranas polimericas condutoras de protons por imobilizacao de MDs em copoliesteres para aplicacao em PEM-FC

    Energy Technology Data Exchange (ETDEWEB)

    Fiuza, R.A.; Brioude, M.M.; Bresciani, D.; Jose, N.M.; Boaventura, J.S. [Universidade Federal da Bahia (IQ/UFBA), Salvador, BA (Brazil). Inst. de Quimica

    2008-07-01

    Polymers are largely studied for use in PEM-type fuel cell (Proton Exchange membrane, PEMFC). These fuel cells are based on polymer membranes as electrolyte, also called protons conductor. This work developed co-polyesters made electrical conductors by doping with sodium dodecyl sulfate. The copolymers were synthesized from the copolymerization of terephthalic and adipic acids with glycerol. The material was processed in a reactor and shaped by hot pressing, yielding homogeneous and flexible plates, with excellent surface finish. The co-polyesters were analyzed by SEM, FTIR, TG, DSC, and XRD. The thermal analysis showed that the composites were thermally stable up to about 250 deg C. The micrographics revealed the MDS homogeneously dispersed in the polymeric matrix. These copolymers showed electrical conductivity between 10-7 to 10-1 S/cm, suggesting strong potential use in PEM fuel cells. (author)

  7. Low Power Reversible Parallel Binary Adder/Subtractor

    Directory of Open Access Journals (Sweden)

    Rangaraju H G

    2010-09-01

    Full Text Available In recent years, Reversible Logic is becoming more and more prominent technology having its applications in Low Power CMOS, Quantum Computing, Nanotechnology, and Optical Computing. Reversibility plays an important role when energy efficient computations are considered. In this paper, Reversible eight-bit Parallel Binary Adder/Subtractor with Design I, Design II and Design III are proposed. In all the three design approaches, the full Adder and Subtractors are realized in a single unit as compared to only full Subtractor in the existing design. The performance analysis is verified using number reversible gates, Garbage input/outputs and Quantum Cost. It is observed that Reversible eight-bit Parallel Binary Adder/Subtractor with Design III is efficient compared to Design I, Design II and existing design

  8. Low Power Reversible Parallel Binary Adder/Subtractor

    CERN Document Server

    Rangaraju, H G; Muralidhara, K N; Raja, K B; 10.5121/vlsic.2010.1303

    2010-01-01

    In recent years, Reversible Logic is becoming more and more prominent technology having its applications in Low Power CMOS, Quantum Computing, Nanotechnology, and Optical Computing. Reversibility plays an important role when energy efficient computations are considered. In this paper, Reversible eight-bit Parallel Binary Adder/Subtractor with Design I, Design II and Design III are proposed. In all the three design approaches, the full Adder and Subtractors are realized in a single unit as compared to only full Subtractor in the existing design. The performance analysis is verified using number reversible gates, Garbage input/outputs and Quantum Cost. It is observed that Reversible eight-bit Parallel Binary Adder/Subtractor with Design III is efficient compared to Design I, Design II and existing design.

  9. KOMITMEN DAN KAPABILITAS UNTUK MENINGKATKAN KINERJA REVERSE LOGISTICS

    Directory of Open Access Journals (Sweden)

    I Nyoman Sutapa

    2009-01-01

    Full Text Available Artikel ini mengkaji pengaruh pengorganisasian dan pemanfaatan teknologi logistic dalam pengelolaan reverse logistics di perusahaan manufaktur penghasil barang/kemasan plastik terhadap kapabilitas inovasi dan komunikasi perusahaan dalam meningkatkan kinerja reverse logistics perusahaan. Analisis yang digunakan adalah Structural Equation Modeling dengan menggunakan program SmartPLS. Hasil penelitian menunjukkan bahwa pengelolaan reverse logistics melalui alokasi anggaran dan pembentukan unit pengelola tersendiri disertai pendayagunaan teknologi, terutama pertukaran data secara elektronik, mampu meningkatkan kapabilitas inovasi, khususnya kemampuan kustomisasi dan fleksibilitas perusahaan dalam meningkatkan kinerja reverse logistics, dalam hal ketepatan waktu dan biaya operasional yang rendah. Di sisi lain, kapabilitas komunikasi belum terbukti dapat memengaruhi kinerja reverse logistics dikarenakan kapabilitas yang dimiliki belum dimanfaatkan secara optimal.

  10. Low Power Reversible Parallel Binary Adder/Subtractor

    Directory of Open Access Journals (Sweden)

    Muralidhara K N

    2010-09-01

    Full Text Available In recent years, Reversible Logic is becoming more and more prominent technology having its applications inLow Power CMOS, Quantum Computing, Nanotechnology, and Optical Computing. Reversibility plays animportant role when energy efficient computations are considered. In this paper, Reversible eight-bit ParallelBinary Adder/Subtractor with Design I, Design II and Design III are proposed. In all the three designapproaches, the full Adder and Subtractors are realized in a single unit as compared to only full Subtractorin the existing design. The performance analysis is verified using number reversible gates, Garbageinput/outputs and Quantum Cost. It is observed that Reversible eight-bit Parallel Binary Adder/Subtractorwith Design III is efficient compared to Design I, Design II and existing design

  11. Reversibly Bistable Flexible Electronics

    KAUST Repository

    Alfaraj, Nasir

    2015-05-01

    Introducing the notion of transformational silicon electronics has paved the way for integrating various applications with silicon-based, modern, high-performance electronic circuits that are mechanically flexible and optically semitransparent. While maintaining large-scale production and prototyping rapidity, this flexible and translucent scheme demonstrates the potential to transform conventionally stiff electronic devices into thin and foldable ones without compromising long-term performance and reliability. In this work, we report on the fabrication and characterization of reversibly bistable flexible electronic switches that utilize flexible n-channel metal-oxide-semiconductor field-effect transistors. The transistors are fabricated initially on rigid (100) silicon substrates before they are peeled off. They can be used to control flexible batches of light-emitting diodes, demonstrating both the relative ease of scaling at minimum cost and maximum reliability and the feasibility of integration. The peeled-off silicon fabric is about 25 µm thick. The fabricated devices are transferred to a reversibly bistable flexible platform through which, for example, a flexible smartphone can be wrapped around a user’s wrist and can also be set back to its original mechanical position. Buckling and cyclic bending of such host platforms brings a completely new dimension to the development of flexible electronics, especially rollable displays.

  12. Inorganic-based proton conductive composite membranes for elevated temperature and reduced relative humidity PEM fuel cells

    Science.gov (United States)

    Wang, Chunmei

    Proton exchange membrane (PEM) fuel cells are regarded as highly promising energy conversion systems for future transportation and stationary power generation and have been under intensive investigations for the last decade. Unfortunately, cutting edge PEM fuel cell design and components still do not allow economically commercial implementation of this technology. The main obstacles are high cost of proton conductive membranes, low-proton conductivity at low relative humidity (RH), and dehydration and degradation of polymer membranes at high temperatures. The objective of this study was to develop a systematic approach to design a high proton conductive composite membrane that can provide a conductivity of approximately 100 mS cm-1 under hot and dry conditions (120°C and 50% RH). The approach was based on fundamental and experimental studies of the proton conductivity of inorganic additives and composite membranes. We synthesized and investigated a variety of organic-inorganic Nafion-based composite membranes. In particular, we analyzed their fundamental properties, which included thermal stability, morphology, the interaction between inorganic network and Nafion clusters, and the effect of inorganic phase on the membrane conductivity. A wide range of inorganic materials was studied in advance in order to select the proton conductive inorganic additives for composite membranes. We developed a conductivity measurement method, with which the proton conductivity characteristics of solid acid materials, zirconium phosphates, sulfated zirconia (S-ZrO2), phosphosilicate gels, and Santa Barbara Amorphous silica (SBA-15) were discussed in detail. Composite membranes containing Nafion and different amounts of functionalized inorganic additives (sulfated inorganics such as S-ZrO2, SBA-15, Mobil Composition of Matter MCM-41, and S-SiO2, and phosphonated inorganic P-SiO2) were synthesized with different methods. We incorporated inorganic particles within Nafion clusters

  13. Why do proton conducting polybenzimidazole phosphoric acid membranes perform well in high-temperature PEM fuel cells?

    Science.gov (United States)

    Melchior, Jan-Patrick; Majer, Günter; Kreuer, Klaus-Dieter

    2016-12-21

    Transport properties and hydration behavior of phosphoric acid/(benz)imidazole mixtures are investigated by diverse NMR techniques, thermogravimetric analysis (TGA) and conductivity measurements. The monomeric systems can serve as models for phosphoric acid/poly-benzimidazole membranes which are known for their exceptional performance in high temperature PEM fuel cells. (1)H- and (31)P-NMR data show benzimidazole acting as a strong Brønsted base with respect to neat phosphoric acid. Since benzimidazole's nitrogens are fully protonated with a low rate for proton exchange with phosphate species, proton diffusion and conduction processes must take place within the hydrogen bond network of phosphoric acid only. The proton exchange dynamics between phosphate and benzimidazole species pass through the intermediate exchange regime (with respect to NMR line separations) with exchange times being close to typical diffusion times chosen in PFG-NMR diffusion measurements (ms regime). The resulting effects, as described by the Kärger equation, are included into the evaluation of PFG-NMR data for obtaining precise proton diffusion coefficients. The highly reduced proton diffusion coefficient within the phosphoric acid part of the model systems compared to neat phosphoric acid is suggested to be the immediate consequence of proton subtraction from phosphoric acid. This reduces hydrogen bond network frustration (imbalance of the number of proton donors and acceptors) and therefore also the rate of structural proton diffusion, phosphoric acid's acidity and hygroscopicity. Reduced water uptake, shown by TGA, goes along with reduced electroosmotic water drag which is suggested to be the reason for PBI-phosphoric acid membranes performing better in fuel cells than other phosphoric-acid-containing electrolytes with higher protonic conductivity.

  14. Fundamentals of reversible flowchart languages

    DEFF Research Database (Denmark)

    Yokoyama, Tetsuo; Axelsen, Holger Bock; Glück, Robert

    2016-01-01

    . Although reversible flowcharts are superficially similar to classical flowcharts, there are crucial differences: atomic steps are limited to locally invertible operations, and join points require an explicit orthogonalizing conditional expression. Despite these constraints, we show that reversible......Abstract This paper presents the fundamentals of reversible flowcharts. They are intended to naturally represent the structure and control flow of reversible (imperative) programming languages in a simple computation model, in the same way classical flowcharts do for conventional languages......, structured reversible flowcharts are as expressive as unstructured ones, as shown by a reversible version of the classic Structured Program Theorem. We illustrate how reversible flowcharts can be concretized with two example programming languages, complete with syntax and semantics: a low-level unstructured...

  15. Novel design of a compacted micro-structured air-breathing PEM fuel cell as a power source for mobile phones

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2010-07-01

    Full Text Available The presence of microelectromechanical system (MEMS technology makes it possible to manufacture the miniaturized fuel cell systems for application in portable electronic devices. The majority of research on micro-scale fuel cells is aimed at micro-power applications. There are many new miniaturized applications which can only be realized if a higher energy density power source is available compared to button cells and other small batteries. In small-scale applications, the fuel cell should be exceptionally small and have highest energy density. One way to achieve these requirements is to reduce the thickness of the cell (compacted-design for increasing the volumetric power density of a fuel cell power supply. A novel, simple to construct, air-breathing micro-structured PEM fuel cell which work in still or slowly moving air has been developed. The novel geometry enables optimum air access to the cathode without the need for pumps, fans or similar devices. In addition, the new design can achieve much higher active area to volume ratios, and hence higher volumetric power densities. Three-dimensional, multi-phase, non-isothermal CFD model of this novel design has been developed. This comprehensive model account for the major transport phenomena in an air-breathing micro-structured PEM fuel cell: convective and diffusive heat and mass transfer, electrode kinetics, transport and phase-change mechanism of water, and potential fields. The model is shown to understand the many interacting, complex electrochemical, and transport phenomena that cannot be studied experimentally. Fully three-dimensional results of the species profiles, temperature distribution, potential distribution, and local current density distribution are presented and analyzed with a focus on the physical insight and fundamental understanding. They can provide a solid basis for optimizing the geometry of the PEM micro fuel cell stack running with a passive mode.

  16. Observador de estado de un sistema de generación de energía de tipo celda de combustible PEM mediante un modelo lineal variante

    OpenAIRE

    Lira, S. de; Puig, Vicenç; Quevedo, Joseba; Husar, Attila

    2010-01-01

    [ES]: En este trabajo se presenta el modelado de un sistema generador de energía basado en pilas de combustible PEM mediante un modelo variante con el punto de operación (modelo LPV). Dicho modelo ha sido obtenido mediante la linealización del modelo dinámico no lineal que ha sido previamente calibrado con datos reales de laboratorio. El modelo LPV obtenido está pensado para ser utilizado en el diseño de controladores y algoritmos de diagnóstico de fallos basados en modelos.

  17. A general tank test of a model of the hull of the Pem-1 flying boat including a special working chart for the determination of hull performance

    Science.gov (United States)

    Dawson, John R

    1938-01-01

    The results of a general tank test of a 1/6 full-size model of the hull of the Pem-1 flying boat (N.A.C.A. model 18) are given in non-dimensional form. In addition to the usual curves, the results are presented in a new form that makes it possible to apply them more conveniently than in the forms previously used. The resistance was compared with that of N.A.C.A. models 11-C and 26(Sikorsky S-40) and was found to be generally less than the resistance of either.

  18. Global atmospheric energy deposition by energetic electrons - Quantitative spatial and temporal characteristics inferred from the Atmospheric X-ray Imaging Spectrometer (PEM/AXIS) on UARS

    Science.gov (United States)

    Chenette, D. L.; Datlowe, D. W.; Robinson, R. M.; Schumaker, T. L.; Vondrak, R. R.; Frahm, R. A.; Sharber, J. R.; Winningham, J. D.

    1993-01-01

    The primary purpose of PEM/AXIS is to provide a global monitor of the energy input to the upper atmosphere due to energetic electrons. The design, development, and calibration of AXIS are described and an assessment of its excellent on-orbit performance is presented. The unique capabilities of X-ray imaging spectrometers to monitor the global patterns of electron energy deposition in the atmosphere are shown through an analysis of some specific cases during the first year of the UARS mission.

  19. CD播放机中使用的DAC(7)——高性能1比特的PDM和PEM

    Institute of Scientific and Technical Information of China (English)

    从余

    2010-01-01

    @@ 最早的1比特DAC采用脉冲密度调制(PDM)方式,但在MASH方式出现之后,脉冲宽度调制(PWM)方式很快就成了1比特DAC的主流.为了与PWM 1比特DAC抗衡,飞利浦、先锋、雅马哈等先后开发出了高性能的PDM1比特DAC,JVC开发出了构想新颖的脉冲沿调制(PEM)1比特DAC.

  20. Diesel fuel processor for PEM fuel cells: Two possible alternatives (ATR versus SR)

    Science.gov (United States)

    Cutillo, A.; Specchia, S.; Antonini, M.; Saracco, G.; Specchia, V.

    There are large efforts in exploring the on-board reforming technologies, which would avoid the actual lack of hydrogen infrastructure and related safety issues. From this view point, the present work deals with the comparison between two different 10 kW e fuel processors (FP) systems for the production of hydrogen-rich fuel gas starting from diesel oil, based respectively on autothermal (ATR) and steam-reforming (SR) process and related CO clean-up technologies; the obtained hydrogen rich gas is fed to the PEMFC stack of an auxiliary power unit (APU). Based on a series of simulations with Matlab/Simulink, the two systems were compared in terms of FP and APU efficiency, hydrogen concentration fed to the FC, water balance and process scheme complexity. Notwithstanding a slightly higher process scheme complexity and a slightly more difficult water recovery, the FP based on the SR scheme, as compared to the ATR one, shows higher efficiency and larger hydrogen concentration for the stream fed to the PEMFC anode, which represent key issues for auxiliary power generation based on FCs as compared, e.g. to alternators.