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Sample records for cell pefc stack

  1. Experimental 1 kW 20 cell PEFC stack

    Energy Technology Data Exchange (ETDEWEB)

    Buechi, F.N.; Marmy, C.A.; Scherer, G.G. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Ruge, M. [Swiss Federal Inst. of Technology (ETH), Zuerich (Switzerland)

    1999-08-01

    A 20-cell PEFC stack was designed and built. Resin impregnated graphite was used as bipolar plate material. The air cooling of the stack was optimized by introducing high surface structures into the open space of the cooling plates. At {eta} (H{sub 2} LHV) = 0.5 a power of 880 W was obtained under conditions of low gas-pressures of 1.15 bar{sub a}. The auxiliary power for process air supply and cooling at 880 W power is less than 7% of the power output, indicating that the described system may be operated at a high efficiency. (author) 5 figs., 2 refs.

  2. Miniaturized polymer electrolyte fuel cell (PEFC) stack using micro structured bipolar plate

    Energy Technology Data Exchange (ETDEWEB)

    Veziridis, Z.; Scherer, G.G.; Marmy, Ch.; Glaus, F. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    In Polymer Electrolyte Fuel Cell (PEFC) technology the reducing of volume and mass of the fuel cell stack and the improvement of catalyst utilization are of great interest. These parameters affect applicability and system cost. In this work we present an alternative way for reducing the stack volume by combining gas distribution and catalytic active area in one plate. Micro machined glassy carbon electrodes serve as support material for the platinum catalyst, as well as gas distributor at the same time. A comparison of these electrodes with conventional platinum-black gas diffusion electrodes under fuel cell conditions shows that the new system is a promising electrode type for enhanced power density and catalyst utilization. (author) 3 figs., 5 refs.

  3. Experimental Dynamic Performance of a 30kW 90Cell PEFC Stack under Transportation Load Cycle Constraints

    OpenAIRE

    DE-BERNARDINIS, A; Harel, F.; Candusso, D.; Coquery, G.; GIRARDOT,L; Hissel, D.; Francois, X.; BESSE, S

    2009-01-01

    The paper presents a synthesis with analysis of different experiments performed on a 30kW PEFC (Polymer Electrolyte Fuel Cell) stack in order to evaluate its dynamic performance. The PEFC stack is a pilot prototype manufactured by the French company HELION and is composed of 90 cells, 800cm2 MEA area (Membrane Electrode Assembly) fed by dry hydrogen and compressed air. The tests were performed in the framework of the French SPACT-80 research project which concerns the study, the realization a...

  4. Fuel cells multi-stack power architectures and experimental validation of 1 kW parallel twin stack PEFC generator based on high frequency magnetic coupling dedicated to on board power unit

    International Nuclear Information System (INIS)

    This paper presents a study of a polymer electrolyte fuel cell (PEFC) multi-stack generator and its power electronic interface dedicated to an on board vehicle power unit. A parallel electric architecture has been designed and tested. First, a dynamic model of the PEFC stack, valid for high frequencies and compatible with power converter interactions, has been developed. This model is used for simulations of the global fuel cell and power converter behaviors. Second, an inventory of generic multi-stack fuel cells architectures is presented in order to couple electrically the fuel cell stacks to an on board DC bus (in series, parallel, through magnetic coupling..). This state of the art is completed by an overview of several candidate power converter topologies for fuel cells. Then, among all the possible technical solutions, an original power converter architecture using a high frequency planar transformer is proposed, which allows parallel and series magnetic couplings of two fuel cell stacks. Then, the study focuses on a first step, which is the association of two PEFC stacks. Such a structure, having good efficiency, is well adapted for testing and operation of fuel cells in normal and degraded working modes, which correspond to real constraints on board a vehicle. Finally, experimental validations on a 2 x 500 W twin stack PEFC with power converter interface demonstrate the technological feasibility for the embarked multi-stack fuel cells generator. The 1 kW power level chosen for the experimentation is close to that of a small on board PEFC auxiliary power unit (APU)

  5. From the components to the stack. Developing and designing 5kW HT-PEFC stacks; Von der Komponente zum Stack. Entwicklung und Auslegung von HT-PEFC-Stacks der 5 kW-Klasse

    Energy Technology Data Exchange (ETDEWEB)

    Bendzulla, Anne

    2010-12-22

    The aim of the present project is to develop a stack design for a 5-kW HTPEFC system. First, the state of the art of potential materials and process designs will be discussed for each component. Then, using this as a basis, three potential stack designs with typical attributes will be developed and assessed in terms of practicality with the aid of a specially derived evaluation method. Two stack designs classified as promising will be discussed in detail, constructed and then characterized using short stack tests. Comparing the stack designs reveals that both designs are fundamentally suitable for application in a HT-PEFC system with on-board supply. However, some of the performance data differ significantly for the two stack designs. The preferred stack design for application in a HT-PEFC system is characterized by robust operating behaviour and reproducible high-level performance data. Moreover, in compact constructions (120 W/l at 60 W/kg), the stack design allows flexible cooling with thermal oil or air, which can be adapted to suit specific applications. Furthermore, a defined temperature gradient can be set during operation, allowing the CO tolerance to be increased by up to 10 mV. The short stack design developed within the scope of the present work therefore represents an ideal basis for developing a 5-kW HT-PEFC system. Topics for further research activities include improving the performance by reducing weight and/or volume, as well as optimizing the heat management. The results achieved within the framework of this work clearly show that HTPEFC stacks have the potential to play a decisive role in increasing efficiency in the future, particularly when combined with an on-board supply system. (orig.) [German] Ziel der vorliegenden Arbeit ist die Entwicklung eines Stackkonzeptes fuer ein 5 kW-HT-PEFC System. Dazu wird zunaechst fuer jede Komponente der Stand der Technik moeglicher Materialien und Prozesskonzepte diskutiert. Darauf aufbauend werden drei

  6. Performance evaluation of 1 kw PEFC

    Energy Technology Data Exchange (ETDEWEB)

    Komaki, Hideaki [Ishikawajima-Harima Heavy Industries Co., Ltd. Tokyo (Japan); Tsuchiyama, Syozo [Shipbuilding Research Association, Minato-ky, Tokyo (Japan)

    1996-12-31

    This report covers part of a joint study on a PEFC propulsion system for surface ships, summarized in a presentation to this Seminar, entitled {open_quote}Study on a PEFC Propulsion System for Surface Ships{close_quotes}, and which envisages application to a 1,500 DWT cargo vessel. The aspect treated here concerns the effects brought on PEFC operating performance by conditions particular to shipboard operation. The performance characteristics were examined through tests performed on a 1 kw stack and on a single cell (Manufactured by Fuji Electric Co., Ltd.). The tests covered the items (1) to (4) cited in the headings of the sections that follow. Specifications of the stack and single cell are as given.

  7. Endurance of Nafion-composite membranes in PEFCs operating at elevated temperature under low relative-humidity

    Indian Academy of Sciences (India)

    A K Sahu; A Jalajakshi; S Pitchumani; P Sridhar; A K Shukla

    2012-03-01

    PEFCs employing Nafion-silica (Nafion-SiO2) and Nafion-mesoporous zirconium phosphate (Nafion-MZP) composite membranes are subjected to accelerated-durability test at 100°C and 15% relative humidity (RH) at open-circuit voltage (OCV) for 50 h and performance compared with the PEFC employing pristine Nafion-1135 membrane. PEFCs with composite membranes sustain the operating voltage better with fluoride-ion-emission rate at least an order of magnitude lower than PEFC with pristine Nafion-1135 membrane. Reduced gas-crossover, fast fuel-cell-reaction kinetics and superior performance of the PEFCs with Nafion-SiO2 and Nafion-MZP composite membranes in relation to the PEFC with pristine Nafion-1135 membrane support the long-term operational usage of the former in PEFCs. An 8-cell PEFC stack employing Nafion-SiO2 composite membrane is also assembled and successfully operated at 60°C without external humidification.

  8. A polymer electrolyte fuel cell stack for stationary power generation from hydrogen fuel

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, M.S.; Moeller-Holst, S.; Webb, D.M.; Zawodzinski, C.; Gottesfeld, S. [Los Alamos National Lab., NM (United States). Materials Science and Technology Div.

    1998-08-01

    The objective is to develop and demonstrate a 4 kW, hydrogen-fueled polymer electrolyte fuel cell (PEFC) stack, based on non-machined stainless steel hardware and on membrane/electrode assemblies (MEAs) of low catalyst loadings. The stack is designed to operate at ambient pressure on the air-side and can accommodate operation at higher fuel pressures, if so required. This is to be accomplished by working jointly with a fuel cell stack manufacturer, based on a CRADA. The performance goals are 57% energy conversion efficiency hydrogen-to-electricity (DC) at a power density of 0.9 kW/liter for a stack operating at ambient inlet pressures. The cost goal is $600/kW, based on present materials costs.

  9. Testing of a De Nora polymer electrolyte fuel cell stack of 1 kW for naval applications

    Science.gov (United States)

    Schmal, D.; Kluiters, C. E.; Barendregt, I. P.

    In a previous study calculations were carried out for a navy frigate with respect to the energy consumption of a propulsion/electricity generation system based on fuel cells. The fuel consumption for the 'all-fuel cell' ship was compared with the consumption of the current propulsion/electricity generation system based on gas turbines and diesel engines; it showed potential energy savings of a fuel cell based system amounting from 25 to 30%. On the basis of these results and taking into account various military aspects it was decided to start tests with a polymer electrolyte fuel cell (PEFC) stack. For this purpose a De Nora 1 kW PEFC was chosen. Results of the first tests after installation are satisfying.

  10. On the materials issues for pefc applications

    Directory of Open Access Journals (Sweden)

    Savadogo Oumarou

    2004-01-01

    Full Text Available Current limitations related to the development of effective, durable and reliable MEA components for PEFC applications are addressed. Advancements made in the development of materials (catalysts, high temperature membranes, bipolar plates, etc. for PEFC are shown. The effect of the catalyst on PEFC performances based on cells fed by hydrogen, direct methanol, direct propane, or direct acetal fuels are presented. The progress in cell performance and cathode research are discussed. Perspectives related to CO tolerance anodes are indicated. The effect of the membranes on the cell performance are shown and parameters which may help the development of appropriate membranes depending on the fuel are suggested. Openings for the future in materials processing and development for PEFC mass production are discussed. The development of New Materials is the key factor to meet those requirements. The aim of this paper is to present challenges related to the development of new materials for PEFC applications and perspectives related to components cost issues are discussed.

  11. Cell resistances of ABPBI-based HT-PEFC-MEAs. Time dependence and influence of operating parameters

    Energy Technology Data Exchange (ETDEWEB)

    Lehnert, W.; Wippermann, K.; Wannek, C. [Forschungszentrum Juelich GmbH (DE). Inst. of Energy Research - Fuel Cells (IEF-3)

    2010-07-01

    Time-dependent measurements of cell impedance of a HT-PEFC based on ABPBI (poly (2,5-benzimidazole)) were performed at constant frequencies close to the high-frequency (h.f.) intercept of the corresponding Nyquist plots with the real axis. The h.f. impedances approximate the ohmic resistance of the cell and they decrease, when current (140 mA/cm{sup 2}) is switched on. Steady state values are attained after 10 minutes. Vice versa, when current is switched off (OCV), the h.f. impedances instantaneously increase but reach steady state values only after about 1 hour. These values rise with increasing gas flow rates. The results are discussed in terms of hydration/dehydration processes, changing the equilibrium between orthophosphoric and pyrophosphoric acid and thus the conductivity of the electrolyte as well as the mobility of molecules and charge carriers. Impedance spectra were recorded after each time-dependent measurement under OCV conditions. The fit of these impedance data based on an equivalent circuit revealed ohmic resistances corrected by h.f. inductances and low frequency impedances associated with the cathode oxygen exchange reaction. The charge transfer resistances deduced from the low frequency impedances strongly depend on both air and hydrogen flow rates. (orig.)

  12. PEFC R&D technology at Toyota

    Energy Technology Data Exchange (ETDEWEB)

    Kawatsu, Shigeyuki; Aoyama, Satoshi; Iwase, Masayoshi [Toyota Motor Corp., Shizuoka (Japan)

    1996-12-31

    Fuel cells are being considered as notable new energy sources due to, not only their potential for obtaining high energy conversion efficiencies, but also their environmental sensitive features. These are especially important now that the problems relating to global environmental pollution are regarded as serious social issues. Polymer electrolyte fuel cells (PEFCs) in particular are being pursued due in part to the prospect of realizing timely enhancements to several key characteristics, including size and power. Encouraged by these anticipated improvements, PEFCs are being investigated as promising power generator candidates for hybrid electric vehicles. The substantial future potential of PEFCs has been noted by TOYOTA, and has motivated extensive R&D activities toward the practical application of PEFCs to hybrid electric vehicles. These R&D efforts include, not only activities on such key areas as performance enhancement, but also extensive attention to a broad range of related concerns, such as cost reduction, reformer development, system integration, durability, reliability and so on. From these diverse tasks, this paper focuses on the issues related to ensuring adequate PEFC performance when reformed fuel is utilized. Recent outcomes of R&D conducted at TOYOTA on this topic will be described.

  13. Dynamic simulator for PEFC propulsion plant

    Energy Technology Data Exchange (ETDEWEB)

    Hiraide, Masataka; Kaneda, Eiichi; Sato, Takao [Mitsui Engineering & Shipbuilding Co., Ltd., Tokyo (Japan)] [and others

    1996-12-31

    This report covers part of a joint study on a PEFC propulsion system for surface ships, summarized in a presentation to this Seminar, entitled {open_quote}Study on a Polymer Electrolyte Fuel Cell (PEFC) Propulsion System for Surface Ships{close_quotes}, and which envisages application to a 1,500 DWT cargo vessel. The work presented here focuses on a simulation study on PEFC propulsion plant performance, and particularly on the system response to changes in load. Using a dynamic simulator composed of system components including fuel cell, various simulations were executed, to examine the performance of the system as a whole and of the individual system components under quick and large load changes such as occasioned by maneuvering operations and by racing when the propeller emerges above water in heavy sea.

  14. Modular fuel-cell stack assembly

    Science.gov (United States)

    Patel, Pinakin; Urko, Willam

    2008-01-29

    A modular multi-stack fuel-cell assembly in which the fuel-cell stacks are situated within a containment structure and in which a gas distributor is provided in the structure and distributes received fuel and oxidant gases to the stacks and receives exhausted fuel and oxidant gas from the stacks so as to realize a desired gas flow distribution and gas pressure differential through the stacks. The gas distributor is centrally and symmetrically arranged relative to the stacks so that it itself promotes realization of the desired gas flow distribution and pressure differential.

  15. Modular fuel-cell stack assembly

    Science.gov (United States)

    Patel, Pinakin

    2010-07-13

    A fuel cell assembly having a plurality of fuel cells arranged in a stack. An end plate assembly abuts the fuel cell at an end of said stack. The end plate assembly has an inlet area adapted to receive an exhaust gas from the stack, an outlet area and a passage connecting the inlet area and outlet area and adapted to carry the exhaust gas received at the inlet area from the inlet area to the outlet area. A further end plate assembly abuts the fuel cell at a further opposing end of the stack. The further end plate assembly has a further inlet area adapted to receive a further exhaust gas from the stack, a further outlet area and a further passage connecting the further inlet area and further outlet area and adapted to carry the further exhaust gas received at the further inlet area from the further inlet area to the further outlet area.

  16. Solid Oxide Fuel Cell Stack Diagnostics

    DEFF Research Database (Denmark)

    Mosbæk, Rasmus Rode; Barfod, Rasmus Gottrup

    time was cut down significantly and it was demonstrated parallel acquisition of 16 repeating units (cells) and the total stack impedance could be made fully automated. The performance and degradation of a 13-cell cross-flow stack was monitored for more than 2500 hours at steady operating conditions...... using the sequential impedance measurement setup. Impedance measurements was used to examine the long-term behavior and monitor the evolution of the series and polarization resistances for four out of the 13 repeating units during the first 1400 hours of operation. The losses for the four selected...... repeating units are reported and discussed. The performance and degradation of a 14-cell co-flow stack was monitored for more than 667 hours at steady operating conditions using the sequential impedance measurement setup. The stack was tested galvanostatically (at constant current) with 50% steam in the...

  17. Power feature required for PEFC powered electric propulsion ship

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Isao [NKK Corp., Yokohama (Japan); Oka, Masaru [Mitsubishi Heavy Industries, Ltd., Nagasaki (Japan)

    1996-12-31

    This report covers part of a joint study on a PEFC system for ship propulsion, summarized in a presentation to this Seminar, entitled {open_quote}Study on a Polymer Electrolyte Fuel Cell (PEFC) Propulsion System for Surface Ships{close_quotes}, and which envisages application to a 1,500 DWT cargo vessel. The aspect treated here concerns an analysis of the load-following performance required and estimated of a PEFC system to power the envisaged ship. The analysis proved that difficulty should be expected of the fuel supply circuit in following with adequate rapidity the sharp changes of load on fuel cell under certain conditions. Further integrated experiments and simulation exercises are currently in progress to further analyze the response characteristics of the fuel supply circuit-particularly of the methanol reformer and gas reservoir-to determine the best measure to be adopted for overcoming the expected difficulty.

  18. Development of PEFC for transportable applications

    Energy Technology Data Exchange (ETDEWEB)

    Maeda, Hideo; Fuklumoto, Hisatoshi; Mitsuda, Kenro [Mitsubishi Electric Corp., Hyogo (Japan)] [and others

    1996-12-31

    Since FY1992, we have been developing PEFC technologies under NEDO`s R&D program. High power density and rapid start-up are essential requirements for transportable applications. Also, if reformed gas is used as fuel, the prevention of CO poisoning and improvement of response to loading are essential. In this paper, methods to increase the effective surface area of a cell, start-up and endurance test results, the study of CO poisoning with a pulse electrolyzing method and the demonstration of a hydrogen recovery subsystem are presented.

  19. Electrode structures of polymer-electrolyte fuel cells (PEFC). An electron microscopy approach to the characterization of the electrode structure of polymer electrolyte fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Scheiba, Frieder

    2009-01-28

    Polymer electrolyte fuel cells (PEFC) have a complex electrode structure, which usually consists of a catalyst, a catalyst support, a polymer electrolyte and pores. The materials used are largely amorphous, have a strong defective structure or have particle diameter of only a few nanometers. In the electrode the materials form highly disordered aggregated structures. Both aspects complicate a systematic structural analysis significantly. However, thorough knowledge of the electrode structure, is needed for systematic advancement of fuel cell technology and to obtain a better understanding of mass and charge carrier transport processes in the electrode. Because of the complex structure of the electrode, an approach based on the examination of electrode thin-sections by electron microscopy was chosen in this work to depicting the electrode structure experimentally. The present work presents these studies of the electrode structure. Some fundamental issues as the influence of the polymer electrolyte concentration and the polarity of the solvent used in the electrode manufacturing process were addressed. During the analysis particular attention was payed to the distribution and structure of the polymer electrolyte. A major problem to the investigations, were the low contrast between the polymer electrolyte, the catalyst support material and the embedding resin. Therefore, dilerent techniques were investigated in terms of their ability to improve the contrast. In this context, a computer-assisted acquisition procedure for energy filtered transmission electron microscopy (EF-TEM) was developed. The acquisition procedure permits a significant extension of the imageable sample. At the same time, it was possible to substantially reduce beam damage of the specimen and to minimize drift of the sample considerably. This allowed unambiguous identification of the polymer electrolyte in the electrode. It could further be shown, that the polymer electrolyte not only coats the

  20. In-plane resolved in-situ measurements of the membrane resistance in PEFCs

    Energy Technology Data Exchange (ETDEWEB)

    Buechi, F.N.; Scherer, G.G. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    The conductivity of the membrane is a limiting factor for the efficiency and power density of PEFCs. Because this conductivity is strongly dependent on the membrane hydration, water management is an important aspect of PEFC optimisation. Single cell model experiments were made in order to determine the in-plane hydration of a Nafion{sup R} membrane under fuel cell conditions as function of the gas humidities. (author) 4 fig., 3 refs.

  1. Solid oxide cell stack and method for preparing same

    DEFF Research Database (Denmark)

    2012-01-01

    A method for producing and reactivating a solid oxide cell stack structure by providing a catalyst precursor in at least one of the electrode layers by impregnation and subsequent drying after the stack has been assembled and initiated. Due to a significantly improved performance and an unexpecte...... voltage improvement this solid oxide cell stack structure is particularly suitable for use in solid oxide fuel cell (SOFC) and solid oxide electrolysing cell (SOEC) applications....

  2. Simple Stacking Methods for Silicon Micro Fuel Cells

    Directory of Open Access Journals (Sweden)

    Gianmario Scotti

    2014-08-01

    Full Text Available We present two simple methods, with parallel and serial gas flows, for the stacking of microfabricated silicon fuel cells with integrated current collectors, flow fields and gas diffusion layers. The gas diffusion layer is implemented using black silicon. In the two stacking methods proposed in this work, the fluidic apertures and gas flow topology are rotationally symmetric and enable us to stack fuel cells without an increase in the number of electrical or fluidic ports or interconnects. Thanks to this simplicity and the structural compactness of each cell, the obtained stacks are very thin (~1.6 mm for a two-cell stack. We have fabricated two-cell stacks with two different gas flow topologies and obtained an open-circuit voltage (OCV of 1.6 V and a power density of 63 mW·cm−2, proving the viability of the design.

  3. Description of gasket failure in a 7 cell PEMFC stack

    Energy Technology Data Exchange (ETDEWEB)

    Husar, Attila; Serra, Maria [Institut de Robotica i Informatica Industrial, Parc Tecnologic de Barcelona, Edifici U, C. Llorens i Artigas, 4-6, 2a Planta, 08028 Barcelona (Spain); Kunusch, Cristian [Laboratorio de Electronica Industrial Control e Instrumentacion, Facultad de Ingenieria, UNLP (Argentina)

    2007-06-10

    This article presents the data and the description of a fuel cell stack that failed due to gasket degradation. The fuel cell under study is a 7 cell stack. The unexpected change in several variables such as temperature, pressure and voltage indicated the possible failure of the stack. The stack was monitored over a 6 h period in which data was collected and consequently analyzed to conclude that the fuel cell stack failed due to a crossover leak on the anode inlet port located on the cathode side gasket of cell 2. This stack failure analysis revealed a series of indicators that could be used by a super visional controller in order to initiate a shutdown procedure. (author)

  4. Compact bipolar plate-free direct methanol fuel cell stacks.

    Science.gov (United States)

    Dong, Xue; Takahashi, Motohiro; Nagao, Masahiro; Hibino, Takashi

    2011-05-14

    Fuel cells with a PtAu/C anode and a Pr-doped Mn(2)O(3)/C cathode were stacked without using a bipolar plate, and their discharge properties were investigated in a methanol aqueous solution bubbled with air. A three-cell stack exhibited a stack voltage of 2330 mV and a power output of 21 mW. PMID:21451850

  5. Nondestructive cell evaluation techniques in SOFC stack manufacturing

    Science.gov (United States)

    Wunderlich, C.

    2016-04-01

    Independent from the specifics of the application, a cost efficient manufacturing of solid oxide fuel cells (SOFC), its electrolyte membranes and other stack components, leading to reliable long-life stacks is the key for the commercial viability of this fuel cell technology. Tensile and shear stresses are most critical for ceramic components and especially for thin electrolyte membranes as used in SOFC cells. Although stack developers try to reduce tensile stresses acting on the electrolyte by either matching CTE of interconnects and electrolytes or by putting SOFC cells under some pressure - at least during transient operation of SOFC stacks ceramic cells will experience some tensile stresses. Electrolytes are required to have a high Weibull characteristic fracture strength. Practical experiences in stack manufacturing have shown that statistical fracture strength data generated by tests of electrolyte samples give limited information on electrolyte or cell quality. In addition, the cutting process of SOFC electrolytes has a major influence on crack initiation. Typically, any single crack in one the 30 to 80 cells in series connection will lead to a premature stack failure drastically reducing stack service life. Thus, for statistical reasons only 100% defect free SOFC cells must be assembled in stacks. This underlines the need for an automated inspection. So far, only manual processes of visual or mechanical electrolyte inspection are established. Fraunhofer IKTS has qualified the method of optical coherence tomography for an automated high throughput inspection. Alternatives like laser speckle photometry and acoustical methods are still under investigation.

  6. Dynamic Model of High Temperature PEM Fuel Cell Stack Temperature

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Kær, Søren Knudsen

    2007-01-01

    The present work involves the development of a model for predicting the dynamic temperature of a high temperature PEM (HTPEM) fuel cell stack. The model is developed to test different thermal control strategies before implementing them in the actual system. The test system consists of a prototype...... stack at a high stoichiometric air flow. This is possible because of the PBI fuel cell membranes used, and the very low pressure drop in the stack. The model consists of a discrete thermal model dividing the stack into three parts: inlet, middle and end and predicting the temperatures in these three...... parts, where also the temperatures are measured. The heat balance of the system involves a fuel cell model to describe the heat added by the fuel cells when a current is drawn. Furthermore the model also predicts the temperatures, when heating the stack with external heating elements for start-up, heat...

  7. Marketingové aspekty cetifikace lesů PEFC

    OpenAIRE

    Tomek, Michal

    2013-01-01

    This work is about forest certification, systems of certification in Czech republic, about their differences and about forest certification PEFC. I focus on the marketing concept of PEFC, consumer behavior, marketing communications on the consumer markets and on market organizations and the possibility to use communication strategies. The main focus of my work is to investigate the possibilities for marketing use PEFC forest certification, position of the organization PEFC on consumer markets...

  8. PEDOT–PSSA as an alternative support for Pt electrodes in PEFCs

    Indian Academy of Sciences (India)

    K K Tintula; S Pitchumani; P Sridhar; A K Shukla

    2010-04-01

    Poly (3,4-ethylenedioxythiophene) (PEDOT) and poly (styrene sulphonic acid) (PSSA) supported platinum (Pt) electrodes for application in polymer electrolyte fuel cells (PEFCs) are reported. PEDOT–PSSA support helps Pt particles to be uniformly distributed on to the electrodes, and facilitates mixed electronic and ionic (H+-ion) conduction within the catalyst, ameliorating Pt utilization. The inherent proton conductivity of PEDOT–PSSA composite also helps reducing Nafion content in PEFC electrodes. During prolonged operation of PEFCs, Pt electrodes supported onto PEDOT–PSSA composite exhibit lower corrosion in relation to Pt electrodes supported onto commercially available Vulcan XC-72R carbon. Physical properties of PEDOT–PSSA composite have been characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. PEFCs with PEDOT–PSSA-supported Pt catalyst electrodes offer a peak power-density of 810 mW cm-2 at a load current-density of 1800 mA cm-2 with Nafion content as low as 5 wt.% in the catalyst layer. Accordingly, the present study provides a novel alternative support for platinized PEFC electrodes.

  9. Electrolytic cell stack with molten electrolyte migration control

    Science.gov (United States)

    Kunz, H. Russell; Guthrie, Robin J.; Katz, Murray

    1988-08-02

    An electrolytic cell stack includes inactive electrolyte reservoirs at the upper and lower end portions thereof. The reservoirs are separated from the stack of the complete cells by impermeable, electrically conductive separators. Reservoirs at the negative end are initially low in electrolyte and the reservoirs at the positive end are high in electrolyte fill. During stack operation electrolyte migration from the positive to the negative end will be offset by the inactive reservoir capacity. In combination with the inactive reservoirs, a sealing member of high porosity and low electrolyte retention is employed to limit the electrolyte migration rate.

  10. Ablation of film stacks in solar cell fabrication processes

    Science.gov (United States)

    Harley, Gabriel; Kim, Taeseok; Cousins, Peter John

    2013-04-02

    A dielectric film stack of a solar cell is ablated using a laser. The dielectric film stack includes a layer that is absorptive in a wavelength of operation of the laser source. The laser source, which fires laser pulses at a pulse repetition rate, is configured to ablate the film stack to expose an underlying layer of material. The laser source may be configured to fire a burst of two laser pulses or a single temporally asymmetric laser pulse within a single pulse repetition to achieve complete ablation in a single step.

  11. Continued SOFC cell and stack technology and improved production methods

    Energy Technology Data Exchange (ETDEWEB)

    Wandel, M.; Brodersen, K.; Phair, J. (and others)

    2009-05-15

    Within this project significant results are obtained on a number of very diverse areas ranging from development of cell production, metallic creep in interconnect to assembling and test of stacks with foot print larger than 500 cm2. Out of 38 milestones 28 have been fulfilled and 10 have been partly fulfilled. This project has focused on three main areas: 1) The continued cell development and optimization of manufacturing processes aiming at production of large foot-print cells, improving cell performance and development environmentally more benign production methods. 2) Stack technology - especially stacks with large foot print and improving the stack design with respect to flow geometry and gas leakages. 3) Development of stack components with emphasis on sealing (for 2G as well as 3G), interconnect (coat, architecture and creep) and test development. Production of cells with a foot print larger than 500 cm2 is very difficult due to the brittleness of the cells and great effort has been put into this topic. Eight cells were successfully produced making it possible to assemble and test a real stack thereby giving valuable results on the prospects of stacks with large foot print. However, the yield rate is very low and a significant development to increase this yield lies ahead. Several lessons were learned on the stack level regarding 'large foot print' stacks. Modelling studies showed that the width of the cell primarily is limited by production and handling of the cell whereas the length (in the flow direction) is limited by e.g. pressure drop and necessary manifolding. The optimal cell size in the flow direction was calculated to be between approx20 cm and < 30 cm. From an economical point of view the production yield is crucial and stacks with large foot print cell area are only feasible if the cell production yield is significantly enhanced. Co-casting has been pursued as a production technique due to the possibilities in large scale production

  12. High specific power, direct methanol fuel cell stack

    Science.gov (United States)

    Ramsey, John C.; Wilson, Mahlon S.

    2007-05-08

    The present invention is a fuel cell stack including at least one direct methanol fuel cell. A cathode manifold is used to convey ambient air to each fuel cell, and an anode manifold is used to convey liquid methanol fuel to each fuel cell. Tie-bolt penetrations and tie-bolts are spaced evenly around the perimeter to hold the fuel cell stack together. Each fuel cell uses two graphite-based plates. One plate includes a cathode active area that is defined by serpentine channels connecting the inlet manifold with an integral flow restrictor to the outlet manifold. The other plate includes an anode active area defined by serpentine channels connecting the inlet and outlet of the anode manifold. Located between the two plates is the fuel cell active region.

  13. 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...

  14. Parametric Sensitivity Tests- European PEM Fuel Cell Stack Test Procedures

    DEFF Research Database (Denmark)

    Araya, Samuel Simon; Andreasen, Søren Juhl; Kær, Søren Knudsen

    2014-01-01

    As fuel cells are increasingly commercialized for various applications, harmonized and industry-relevant test procedures are necessary to benchmark tests and to ensure comparability of stack performance results from different parties. This paper reports the results of parametric sensitivity tests...

  15. Modelling and Evaluation of Heating Strategies for High Temperature Polymer Electrolyte Membrane Fuel Cell Stacks

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Kær, Søren Knudsen

    2008-01-01

    Experiments were conducted on two different cathode air cooled high temperature PEM (HTPEM) fuel cell stacks; a 30 cell 400W prototype stack using two bipolar plates per cell, and a 65 cell 1 kW commercial stack using one bipolar plate per cell. The work seeks to examine the use of different...

  16. Measurement of water distribution by using neutron radiography and network analysis of gas-velocity distributions in a PEFC

    International Nuclear Information System (INIS)

    Fuel gas (hydrogen gas) and oxidant gas (air) are supplied to a Polymer Electrolyte Fuel Cell (PEFC). Condensation may occur in the cathode side, since air is super-saturated by the fuel cell reactions. If condensed water exists in a gas diffusion layer (GDL) or the gas channels, it may affect the fuel cell performances because of blocking the oxygen from reaching the cathode reaction site. In order to clarify water effects on performances of a PEFC, visualization and quantitative measurements of water distributions in a PEFC were carried out by means of neutron radiography. A network analysis of gas-velocity distribution was applied for the experimental results. It analyzes the gas-velocity distribution depending on the flow resistance which is the pressure drop. Applying the measured data of water thickness, pressure drop in the gas channel and the GDL can be obtained. (author)

  17. Development of Bipolar Plate Stack Type Microbial Fuel Cells

    International Nuclear Information System (INIS)

    Microbial fuel cells (MFC) stacked with bipolar plates have been constructed and their performance was tested. In this design, single fuel cell unit was connected in series by bipolar plates where an anode and a cathode were made in one graphite block. Two types of bipolar plate stacked MFCs were constructed. Both utilized the same glucose oxidation reaction catalyzed by Gram negative bacteria, Proteus vulgaris as a biocatalyst in an anodic compartment, but two different cathodic reactions were employed: One with ferricyanide reduction and the other with oxygen reduction reactions. In both cases, the total voltage was the mathematical sum of individual fuel cells and no degradation in performance was found. Electricity from these MFCs was stored in a supercapacitor to drive external loads such as a motor and electric bulb

  18. Dynamic Model of the High Temperature Proton Exchange Membrane Fuel Cell Stack Temperature

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Kær, Søren Knudsen

    2009-01-01

    consists of a prototype cathode air cooled 30 cell HTPEM fuel cell stack developed at the Institute of Energy Technology at Aalborg University. This fuel cell stack uses PEMEAS Celtec P-1000 membranes and runs on pure hydrogen in a dead-end anode configuration with a purge valve. The cooling of the stack...

  19. Solid Oxide Cell and Stack Testing, Safety and Quality Assurance (SOCTESQA)

    DEFF Research Database (Denmark)

    Auer, C.; Lang, M.; Couturier, K.; Ravn Nielsen, Eva; J. McPhail, S.; Tsotridis, G.; Fu, Q.; H. Chan, S.

    2015-01-01

    In the EU-funded project “SOCTESQA” partners from Europe and Singapore are working together to develop uniform and industry wide test procedures and protocols for solid oxide cells and stacks SOC cell/stack assembly. New application fields which are based on the operation of the SOC cell/stack as...

  20. Maturing of SOFC cell and stack production technology and preparation for demonstration of SOFC stacks. Part 2

    Energy Technology Data Exchange (ETDEWEB)

    2006-07-01

    The TOFC/Riso pilot plant production facility for the manufacture of anode-supported cells has been further up-scaled with an automated continuous spraying process and an extra sintering capacity resulting in production capacity exceeding 15,000 standard cells (12x12 cm2) in 2006 with a success rate of about 85% in the cell production. All processing steps such as tape-casting, spraying, screen-printing and atmospheric air sintering in the cell production have been selected on condition that up-scaling and cost effective, flexible, industrial mass production are feasible. The standard cell size is currently being increased to 18x18 cm2, and 150 cells of this size have been produced in 2006 for our further stack development. To improve quality and lower production cost, a new screen printing line is under establishment. TOFC's stack design is an ultra compact multilayer assembly of cells (including contact layers), metallic interconnects, spacer frames and glass seals. The compactness ensures minimized material consumption and low cost. Standard stacks with cross flow configuration contains 75 cells (12x12cm2) delivering about 1.2 kW at optimal operation conditions with pre-reformed NG as fuel. Stable performance has been demonstrated for 500-1000 hours. Significantly improved materials, especially concerning the metallic interconnect and the coatings have been introduced during the last year. Small stacks (5-10 cells) exhibit no detectable stack degradation using our latest cells and stack materials during test periods of 500-1000 hours. Larger stacks (50-75 cells) suffer from mal-distribution of gas and air inside the stacks, gas leakage, gas cross-over, pressure drop, and a certain loss of internal electrical contact during operation cycles. Measures have been taken to find solutions during the following development work. The stack production facilities have been improved and up-scaled. In 2006, 5 standard stacks have been assembled and burned in based on

  1. 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

  2. Change of electrochemical impedance spectra during CO poisoning of the Pt and Pt-Ru anodes in a membrane fuel cell (PEFC)

    International Nuclear Information System (INIS)

    The influence of carbon monoxide poisoning on the platinum and platinum-ruthenium anode in a polymer electrolyte fuel cell was investigated using electrochemical impedance spectroscopy (EIS). EIS is a very useful method for the characterisation of fuel cells. Therefore, impedance measurements of the cell under constant load were performed at periodic time intervals. Due to the poisoning effect of the carbon monoxide, the system changes its state during the experiment. The reconstruction of quasi-causal spectra was made possible using enhanced numerical procedures, especially the time course interpolation and the Z-HIT refinement. The reconstructed impedance spectra show a strong time dependence and exhibit pseudo-inductive contributions at the low-frequency part of the spectra which increase during the experiment. The analysis of the spectra suggests that the pseudo-inductive behaviour can be attributed to a surface relaxation process of the anode. Furthermore, the influence of the carbon monoxide on the electrochemical behaviour of the contaminated fuel cell may be interpreted by means of a Faraday impedance in addition to a potential-dependent hindrance of the charge transfer

  3. System for adding sulfur to a fuel cell stack system for improved fuel cell stability

    Science.gov (United States)

    Mukerjee, Subhasish; Haltiner, Jr., Karl J; Weissman, Jeffrey G

    2013-08-13

    A system for adding sulfur to a reformate stream feeding a fuel cell stack, having a sulfur source for providing sulfur to the reformate stream and a metering device in fluid connection with the sulfur source and the reformate stream. The metering device injects sulfur from the sulfur source to the reformate stream at a predetermined rate, thereby providing a conditioned reformate stream to the fuel cell stack. The system provides a conditioned reformate stream having a predetermined sulfur concentration that gives an acceptable balance of minimal drop in initial power with the desired maximum stability of operation over prolonged periods for the fuel cell stack.

  4. Performance of advanced automotive fuel cell systems with heat rejection constraint

    Science.gov (United States)

    Ahluwalia, R. K.; Wang, X.; Steinbach, A. J.

    2016-03-01

    Although maintaining polymer electrolyte fuel cells (PEFC) at temperatures below 80 °C is desirable for extended durability and enhanced performance, the automotive application also requires the PEFC stacks to operate at elevated temperatures and meet the heat rejection constraint, stated as Q/ΔT automotive stack subject to this Q/ΔT constraint, and illustrate it by applying it to a state-of-the-art stack with nano-structured thin film ternary catalysts in the membrane electrode assemblies. In the illustrative example, stack coolant temperatures >90 °C, stack inlet pressures >2 atm, and cathode stoichiometries <2 are needed to satisfy the Q/ΔT constraint in a cost effective manner. The reference PEFC stack with 0.1 mg/cm2 Pt loading in the cathode achieves 753 mW cm-2 power density at the optimum conditions for heat rejection, compared to 964 mW cm-2 in the laboratory cell at the same cell voltage (663 mV) and pressure (2.5 atm) but lower temperature (85 °C), higher cathode stoichiometry (2), and 100% relative humidity.

  5. Two-phase behavior and compression effects in the PEFC gas diffusion medium

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, Partha P [Los Alamos National Laboratory; Kang, Qinjun [Los Alamos National Laboratory; Schulz, Volker P [APL-LANDAU GMBH; Wang, Chao - Yang [PENN STATE UNIV; Becker, Jurgen [NON LANL; Wiegmann, Andreas [NON LANL

    2009-01-01

    A key performance limitation in the polymer electrolyte fuel cell (PEFC), manifested in terms of mass transport loss, originates from liquid water transport and resulting flooding phenomena in the constituent components. A key contributor to the mass transport loss is the cathode gas diffusion layer (GDL) due to the blockage of available pore space by liquid water thus rendering hindered oxygen transport to the active reaction sites in the electrode. The GDL, therefore, plays an important role in the overall water management in the PEFC. The underlying pore-morphology and the wetting characteristics have significant influence on the flooding dynamics in the GDL. Another important factor is the role of cell compression on the GDL microstructural change and hence the underlying two-phase behavior. In this article, we present the development of a pore-scale modeling formalism coupled With realistic microstructural delineation and reduced order compression model to study the structure-wettability influence and the effect of compression on two-phase behavior in the PEFC GDL.

  6. A New, Scalable and Low Cost Multi-Channel Monitoring System for Polymer Electrolyte Fuel Cells.

    Science.gov (United States)

    Calderón, Antonio José; González, Isaías; Calderón, Manuel; Segura, Francisca; Andújar, José Manuel

    2016-01-01

    In this work a new, scalable and low cost multi-channel monitoring system for Polymer Electrolyte Fuel Cells (PEFCs) has been designed, constructed and experimentally validated. This developed monitoring system performs non-intrusive voltage measurement of each individual cell of a PEFC stack and it is scalable, in the sense that it is capable to carry out measurements in stacks from 1 to 120 cells (from watts to kilowatts). The developed system comprises two main subsystems: hardware devoted to data acquisition (DAQ) and software devoted to real-time monitoring. The DAQ subsystem is based on the low-cost open-source platform Arduino and the real-time monitoring subsystem has been developed using the high-level graphical language NI LabVIEW. Such integration can be considered a novelty in scientific literature for PEFC monitoring systems. An original amplifying and multiplexing board has been designed to increase the Arduino input port availability. Data storage and real-time monitoring have been performed with an easy-to-use interface. Graphical and numerical visualization allows a continuous tracking of cell voltage. Scalability, flexibility, easy-to-use, versatility and low cost are the main features of the proposed approach. The system is described and experimental results are presented. These results demonstrate its suitability to monitor the voltage in a PEFC at cell level. PMID:27005630

  7. A New, Scalable and Low Cost Multi-Channel Monitoring System for Polymer Electrolyte Fuel Cells

    Directory of Open Access Journals (Sweden)

    Antonio José Calderón

    2016-03-01

    Full Text Available In this work a new, scalable and low cost multi-channel monitoring system for Polymer Electrolyte Fuel Cells (PEFCs has been designed, constructed and experimentally validated. This developed monitoring system performs non-intrusive voltage measurement of each individual cell of a PEFC stack and it is scalable, in the sense that it is capable to carry out measurements in stacks from 1 to 120 cells (from watts to kilowatts. The developed system comprises two main subsystems: hardware devoted to data acquisition (DAQ and software devoted to real-time monitoring. The DAQ subsystem is based on the low-cost open-source platform Arduino and the real-time monitoring subsystem has been developed using the high-level graphical language NI LabVIEW. Such integration can be considered a novelty in scientific literature for PEFC monitoring systems. An original amplifying and multiplexing board has been designed to increase the Arduino input port availability. Data storage and real-time monitoring have been performed with an easy-to-use interface. Graphical and numerical visualization allows a continuous tracking of cell voltage. Scalability, flexibility, easy-to-use, versatility and low cost are the main features of the proposed approach. The system is described and experimental results are presented. These results demonstrate its suitability to monitor the voltage in a PEFC at cell level.

  8. PEM Fuel Cells from Single Cell to Stack - Fundamental, Modeling, Analysis, and Applications

    OpenAIRE

    Maher A.R. Sadiq Al-Baghdadi

    2015-01-01

    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 (CFD). Part III: Analysis Chapter 7: PEM fuel cell analysis. Chapter 8: PEM fuel cell stack desig...

  9. Modeling and simulation of a reformate supplied PEM fuel cell stack, application to fault detection

    OpenAIRE

    Najafi, Masoud; Dipenta, Damiano; Bencherif, Karim; Sorine, Michel

    2007-01-01

    A method to reduce the model of a nonlinear dynamic fuel cell stack, which is suitable for control and fault detection studies, is presented. In order to model the fuel cell stack, we have assumed that the fuel cells are arranged in a stack, electrically in series, with thermal and electrical contacts. Since in practical applications a stack may be composed of several (at least fifty) fuel cells, such model will be a large set of differential equations which may be difficult to simulate espec...

  10. Mechanically Stacked Four-Junction Concentrator Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Steiner, Myles A.; Geisz, John F.; Ward, J. Scott; Garcia, Ivan; Friedman, Daniel J.; King, Richard R.; Chiu, Philip T.; France, Ryan M.; Duda, Anna; Olavarria, Waldo J.; Young, Michelle; Kurtz, Sarah R.

    2015-06-14

    Multijunction solar cells can be fabricated by bonding together component cells that are grown separately. Because the component cells are each grown lattice-matched to suitable substrates, this technique allows alloys of different lattice constants to be combined without the structural defects introduced when using metamorphic buffers. Here we present results on the fabrication and performance of four-junction mechanical stacks composed of GaInP/GaAs and GaInAsP/GaInAs tandems, grown on GaAs and InP substrates, respectively. The two tandems were bonded together with a low-index, transparent epoxy that acts as an omni-directional reflector to the GaAs bandedge luminescence, while simultaneously transmitting nearly all of the sub-bandgap light. As determined by electroluminescence measurements and optical modeling, the GaAs subcell demonstrates a higher internal radiative limit and thus higher subcell voltage, compared with GaAs subcells without enhanced internal optics; all four subcells exhibit excellent material quality. The device was fabricated with four contact terminals so that each tandem can be operated at its maximum power point, which raises the cumulative efficiency and decreases spectral sensitivity. Efficiencies exceeding 38% at one-sun have been demonstrated. Eliminating the series resistance is the key challenge for the concentrator cells. We will discuss the performance of one-sun and concentrator versions of the device, and compare the results to recently fabricated monolithic four-junction cells.

  11. Occurrence and implications of voltage reversal in stacked microbial fuel cells.

    Science.gov (United States)

    An, Junyeong; Lee, Hyung-Sool

    2014-06-01

    Voltage reversal in stacked microbial fuel cells (MFCs) is a significant challenge that must be addressed, and the information on its definite cause and occurrence process is still obscure. In this work, we first demonstrated that different anodic reaction rates caused voltage reversal in a stacked MFC. Sluggish reaction rates on the anode in unit 1 of the stacked MFC resulted in a significantly increased anode overpotential of up to 0.132 V, as compared to negligible anode overpotential (0.0247 V) in unit 2. This work clearly verified the process of voltage reversal in the stacked MFC. As the current was gradually increased in the stacked MFC, the voltage in the stacked unit 1 decreased to 0 V prior to that of the stacked unit 2. Then, when the voltage in unit 1 became 0 V, it was converted from a galvanic cell to an electrochemical cell powered by unit 2. We found that the stacked unit 2 provided electrical energy for the stacked unit 1 as a power supply. Finally, the anode potential of the stacked unit 1 significantly increased over cathode potential as current increased further, which caused voltage reversal in unit 1. Voltage reversal occurs in stacked MFCs as a result of non-spontaneous anode overpotential in a unit MFC that has sluggish anode kinetics compared to the other unit MFCs. PMID:24771553

  12. Fade to Green: A Biodegradable Stack of Microbial Fuel Cells.

    Science.gov (United States)

    Winfield, Jonathan; Chambers, Lily D; Rossiter, Jonathan; Stinchcombe, Andrew; Walter, X Alexis; Greenman, John; Ieropoulos, Ioannis

    2015-08-24

    The focus of this study is the development of biodegradable microbial fuel cells (MFCs) able to produce useful power. Reactors with an 8 mL chamber volume were designed using all biodegradable products: polylactic acid for the frames, natural rubber as the cation-exchange membrane and egg-based, open-to-air cathodes coated with a lanolin gas diffusion layer. Forty MFCs were operated in various configurations. When fed with urine, the biodegradable stack was able to power appliances and was still operational after six months. One useful application for this truly sustainable MFC technology includes onboard power supplies for biodegradable robotic systems. After operation in remote ecological locations, these could degrade harmlessly into the surroundings to leave no trace when the mission is complete. PMID:26212495

  13. Recent Progress and Spectral Robustness Study for Mechanically Stacked Multi-junction Solar Cells

    Science.gov (United States)

    Zhao, Lu; Flamand, Giovanni; Poortmans, Jef

    2010-10-01

    Multi-terminal mechanically stacked multi-junction solar cells are an attractive candidate for terrestrial concentrator photovoltaics applications. Unlike monolithically integrated multi-junction solar cells which require current matching, all the available photon currents can be fully extracted from each junction of a mechanically stacked solar cell. Therefore, it has a high performance potential, and more importantly is less sensitive to spectrum variations. Lower losses due to current mismatch translate into a higher annual energy output for the mechanical stack. This paper presents the baseline processing developed at imec for the mechanical stacking process, and the most recent cell results by means of this technology. A GaAs-Ge dual-junction mechanically stacked multi-junction solar cell is demonstrated, with 24.7% plus 2.52% under AM1.5g, and 27.7% plus 4.42% under 30Suns concentration. In addition, spectral sensitivity is studied for both monolithically stacked and mechanically stacked solar cells, to learn the influence of spectrum variations on multi-junction solar cell performance. SMARTS model is used to predict the spectral irradiances, with solar radiation and meteorological elements from typical meteorological year 3 (TMY3) data set. The generated spectra are then fed into TCAD numerical simulation tool, to simulate the device performance. The simulation results show a reduced spectral sensitivity for mechanically stacked cell, and there is a 6% relative gain in annual energy production for the site studied (Las Vegas), compared with the monolithic stack.

  14. Improved solid oxide fuel cell stacks: Power density, durability and modularity. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Lund Frandsen, H.; Kiebach, W.R.; Hoeegh, J. (Technical Univ. of Denmark. Risoe National Lab. for Sustainable Energy, Roskilde (Denmark)) (and others)

    2010-10-15

    This report presents the work performed within the project PSO2009-1-10207 during the period from 01-04-2009 - 31-06-2010. The report is divided into three parts covering the three work packages: Stack components; Stacks and durability; and Large SOFC systems: modularity and scalability. The project contains 38 milestones and all milestones in the project have been either fully or partly fulfilled. Two major achievements within this project concern the robustness towards dynamic operations and implementation of cells with more active cathodes: Within this project tools to evaluate and test SOFC stacks with respect to robustness during dynamic operations has been developed. From stack tests performed under dynamic conditions it was observed that the effect on degradation and failure seemed to be very little. The thermo-mechanical models developed in this project in combination with the dynamic stack model was used in combination to understand why. The results clearly showed that the hardest stress field applied to the cells arises from the steady state operating point rather than from the dynamic conditions. This is a very promising result concerning the fact that especially small CHP units in a commercial system will experience dynamic conditions from load cycling and thermal cycling. A new type of cell with a more active cathode has been formulated and introduced into the TOFC stacks in this project. The aim was to improve the effect of the stack by 25 %. However, compared to a standard stack with the ''old'' cells, the stack effect was increased by 44% - from a cross flow stack with standard 2G cells to a cross flow stack with 2.5G cells. The new type of cells also show an excellent stability towards moisture in the cathode feed, and a stack with 2.5G cells has been tested for 12.000 hrs with a degradation rate of 30 mOMEGAcm2/1000 hr. (Author)

  15. Electrochemical removal of NOx with porous cell stacks

    DEFF Research Database (Denmark)

    Werchmeister, Rebecka Maria Larsen; Kammer Hansen, Kent; Mogensen, Mogens Bjerg

    2010-01-01

    In this study porous cell stacks were investigated for their ability to remove NOx electrochemically. The cell stacks were made from laminated tapes of porous electrolyte Ce0.9Gd0.1O1.95 and composite electrodes of La1−xSrxMnO3 (x = 0.15, and 0.5) and ceria doped with Gd or Pr. The cell stacks were...... infiltrated with nano-particles of pure ceria, Ce0.9Gd0.1O1.95 and Ce0.8Pr0.2O2−δ after sintering. A gas stream containing NO were sent through the cell stack. When the cell stacks were polarised with 0.75 V per cell then it was possible to remove some of the NOx in the temperature interval of 250–400 °C. The...

  16. Fabrication of highly porous LSM/CGO cell stacks for electrochemical flue gas purification

    DEFF Research Database (Denmark)

    Andersen, Kjeld Bøhm; Bræstrup, Frantz Radzik; Kammer Hansen, Kent

    2013-01-01

    In this study porous cell stacks for electrochemical flue gas purification were fabricated using tape casting and lamination followed by sintering. Two different mixtures of pore formers were used; either a mixture of two types of graphite or a mixture of graphite with polymethyl methacrylate micro......-particles. It was shown that the porous cell stacks fabricated with polymethyl methacrylate had a higher porosity but a similar back pressure compared to the porous cell stacks fabricated with only graphite as a pore former. This was due to a high back pressure of the electrolyte layer. The porous cell stacks...... polymethyl methacrylate pore former, especially in the electrolyte layer, is needed, in order to lower the back pressure of the porous cell stack....

  17. Continued maturing of SOFC cell production technology and development and demonstration of SOFC stacks. Final report

    Energy Technology Data Exchange (ETDEWEB)

    2008-08-15

    The overall objective of the 6385 project was to develop stack materials, components and stack technology including industrial relevant manufacturing methods for cells components and stacks. Furthermore, the project should include testing and demonstration of the stacks under relevant operating conditions. A production of 6.829 cells, twenty 75-cell stacks and a number of small stacks was achieved. Major improvements were also made in the manufacturing methods and in stack design. Two test and demonstration activities were included in the project. The first test unit was established at H.C. OErsted power plant at the Copenhagen waterfront in order to perform test of SOFC stacks. The unit will be used for tests in other projects. The second demonstration unit is the alpha prototype demonstration in a system running on natural gas in Finland. The alpha prototype demonstration system with 24 TOFC (Topsoe Fuel Cell) stacks was established and started running in October 2007 and operational experience was gained in the period from October 2007 to February 2008. (auther)

  18. Dynamic Operation of HT-PEFC: in-operando imaging of phosphoric acid profiles and (re)distribution

    OpenAIRE

    Eberhardt, S H; Toulec, M; Marone, F.; Stampanoni, M.; Buchi, F N; Schmidt, T.J.

    2015-01-01

    Synchrotron based X-ray tomographic microscopy (XTM) is used for imaging and quantifying the redistribution of phosphoric acid (PA) in high temperature polymer electrolyte fuel cells (HT-PEFC) in-operando. The main focus of this work is the redistribution of phosphoric acid under dynamic load conditions. Therefore, two different load cycling protocols were applied and the transient redistribution within the fuel cell components was imaged. XTM, for the first time, revealed that the examined P...

  19. Development of a polymer electrolyte membrane fuel cell stack for an underwater vehicle

    Science.gov (United States)

    Han, In-Su; Kho, Back-Kyun; Cho, Sungbaek

    2016-02-01

    This paper presents a polymer electrolyte membrane (PEM) fuel cell stack that is specifically designed for the propulsion of an underwater vehicle (UV). The stack for a UV must be continuously operated in a closed space using hydrogen and pure oxygen; it should meet various performance requirements such as high hydrogen and oxygen utilizations, low hydrogen and oxygen consumptions, a high ramp-up rate, and a long lifetime. To this end, a cascade-type stack design is employed and the cell components, including the membrane electrode assembly and bipolar plate, are evaluated using long-term performance tests. The feasibility of a fabricated 4-kW-class stack was confirmed through various performance evaluations. The proposed cascade-type stack exhibited a high efficiency of 65% and high hydrogen and oxygen utilizations of 99.89% and 99.68%, respectively, resulting in significantly lesser purge-gas emissions to the outside of the stack. The load-following test was successfully performed at a high ramp-up rate. The lifetime of the stack was confirmed by a 3500-h performance test, from which the degradation rate of the cell voltage was obtained. The advantages of the cascade-type stack were also confirmed by comparing its performance with that of a single-stage stack operating in dead-end mode.

  20. Cell separator for use in bipolar-stack energy storage devices

    Science.gov (United States)

    Mayer, Steven T.; Feikert, John H.; Kachmitter, James L.; Pekala, Richard W.

    1995-01-01

    An improved multi-cell electrochemical energy storage device, such as a battery, fuel cell, or double layer capacitor using a cell separator which allows cells to be stacked and interconnected with low electrical resistance and high reliability while maximizing packaging efficiency. By adding repeating cells, higher voltages can be obtained. The cell separator is formed by applying an organic adhesive on opposing surfaces of adjacent carbon electrodes or surfaces of aerogel electrodes of a pair of adjacent cells prior to or after pyrolysis thereof to form carbon aerogel electrodes. The cell separator is electronically conductive, but ionically isolating, preventing an electrolytic conduction path between adjacent cells in the stack.

  1. Real-time Monitoring of Internal Temperature and Voltage of High-temperature Fuel Cell Stack

    International Nuclear Information System (INIS)

    The nonuniform local temperature and voltage in the chemical reaction process of high-temperature proton exchange membrane fuel cell (HT-PEMFC) stack can affect the reaction of membrane electrode assembly (MEA) and the performance and life of fuel cell stack. The effectiveness and internal information of fuel cell stack can be discussed by using external measurement, invasive, theoretical modeling, and single temperature, or voltage measurement. But there are some problems, such as mm scale sensor, inaccurate measurement, influencing the fuel cell stack performance, and failing to know internal actual reactive state instantly. This study uses micro-electro-mechanical systems (MEMS) technology to develop a new generation flexible micro temperature and voltage sensors applicable to high-temperature electrochemical environment. Micro sensors have embedded in the cathode channel plate of HT-PEMFC stack. At the operating temperature of 170 °C and constant current (2, 10, 20 A), the curvilinear trends of local temperature and voltage inside the fuel cell stack measured by flexible micro sensors are consistent, proving the reliability of micro sensors. The test result also shows that the heat distribution in the fuel cell stack is nonuniform

  2. Series assembly of microbial desalination cells containing stacked electrodialysis cells for partial or complete seawater desalination.

    Science.gov (United States)

    Kim, Younggy; Logan, Bruce E

    2011-07-01

    A microbial desalination cell (MDC) is a new approach for desalinating water based on using the electrical current generated by exoelectrogenic bacteria. Previously developed MDCs have used only one or two desalination chambers with substantial internal resistance, and used low salinity catholytes containing a buffered or acid solution. Here we show that substantially improved MDC performance can be obtained even with a nonbuffered, saline catholyte, by using an electrodialysis stack consisting of 5 pairs of desalting and concentrating cells. When 4 stacked MDCs were used in series (20 total pairs of desalination chambers), the salinity of 0.06 L of synthetic seawater (35 g/L NaCl) was reduced by 44% using 0.12 L of anode solution (2:1). The resistive loss in the electrodialysis stack was negligible due to minimization of the intermembrane distances, and therefore the power densities produced by the MDC were similar to those produced by single chamber microbial fuel cells (MFCs) lacking desalination chambers. The observed current efficiency was 86%, indicating separation of 4.3 pairs of sodium and chloride ions for every electron transferred through the circuit. With two additional stages (total of 3.8 L of anolyte), desalination was increased to 98% salt removal, producing 0.3 L of fresh water (12.6:1). These results demonstrate that stacked MDCs can be used for efficient desalination of seawater while at the same time achieving power densities comparable to those obtained in MFCs. PMID:21671676

  3. Series Assembly of Microbial Desalination Cells Containing Stacked Electrodialysis Cells for Partial or Complete Seawater Desalination

    KAUST Repository

    Kim, Younggy

    2011-07-01

    A microbial desalination cell (MDC) is a new approach for desalinating water based on using the electrical current generated by exoelectrogenic bacteria. Previously developed MDCs have used only one or two desalination chambers with substantial internal resistance, and used low salinity catholytes containing a buffered or acid solution. Here we show that substantially improved MDC performance can be obtained even with a nonbuffered, saline catholyte, by using an electrodialysis stack consisting of 5 pairs of desalting and concentrating cells. When 4 stacked MDCs were used in series (20 total pairs of desalination chambers), the salinity of 0.06 L of synthetic seawater (35 g/L NaCl) was reduced by 44% using 0.12 L of anode solution (2:1). The resistive loss in the electrodialysis stack was negligible due to minimization of the intermembrane distances, and therefore the power densities produced by the MDC were similar to those produced by single chamber microbial fuel cells (MFCs) lacking desalination chambers. The observed current efficiency was 86%, indicating separation of 4.3 pairs of sodium and chloride ions for every electron transferred through the circuit. With two additional stages (total of 3.8 L of anolyte), desalination was increased to 98% salt removal, producing 0.3 L of fresh water (12.6:1). These results demonstrate that stacked MDCs can be used for efficient desalination of seawater while at the same time achieving power densities comparable to those obtained in MFCs. © 2011 American Chemical Society.

  4. Development of a 100 W PEM fuel cell stack for portable applications

    Energy Technology Data Exchange (ETDEWEB)

    Eroglu, Inci; Erkan, Serdar [Middle East Technical Univ., Ankara (Turkey). Dept. of Chemical Engineering

    2010-07-01

    In this work, an air cooled 100 W stack was designed, manufactured and tested. The bipolar plates were manufactured by CNC machining of graphite. Membrane electrode assemblies (MEAs) were produced by spraying catalyst ink onto the gas diffusion layer (GDL). A fuel cell stack was assembled with 20 cells each having 12.25 cm{sup 2} active area. The test was carried out with H{sub 2} at anode and air at cathode side both at 100% relative humidity having 1.2 and 2 stoichiometric ratios, respectively. The operating temperature of the stack was kept at 60 C during the test. The results indicated that the stack has a maximum power of 60 W at 12 V operation. Cell numbers 1, 2, 3 and 20 always had less potential than the 0.6 V average cell voltage. Uniform cell voltage distribution has been achieved by improving thermal management and reactant distribution. (orig.)

  5. Development of Sulfonated FEP / Nafion Hybrid Proton Exchange Membranes for PEFC

    International Nuclear Information System (INIS)

    Membrane Electrode Assemblies (MEAs) in polymer electrolyte fuel cells (PEFCs) are consisted of proton exchange membranes (PEMs), binder and Pt/C electrodes. In our previous work, the partial-fluorinated sulfonic acid membranes have been fabricated by pre EB-grafting method. However, in the PEFC operation at higher temperatures, the difference of thermo-physical properties in MEAs consists of obtained PEMs, Pt/C, electrodes and binder such as Nafion-dispersion would be induced de-lamination between the PEM and electrodes. The poor adhesion between PEM and electrodes causes higher membrane resistance and decreasing of PEFC performance. In this study, in order to get well-laminated MEA, PEMs based on partial-fluorinated sulfonic acid were fabricated by adding same polymeric components with binder materials. Fluorinated ethylene-propylene co-polymer (FEP) films (thickness: 25μm) were grafted with styrene monomer at 80 degree in liquid phase after EB irradiation under nitrogen gas atmosphere at room temperature, and then sulfonated by chlorosulfonic acid solution. The sulfonated FEP membranes (s-FEP) were milled to fine powders and the average diameter was 73.6μm. Then, s-FEP / Nafion hybrid membranes (FN) were obtained by mixing s-FEP powder with Nafion-dispersion and 1-propanol. The thickness of obtained FN was about 90μm. Ion exchange capacity (IEC) was measured by titration. IECs of FN and Nafion were 1.2 meq/g and 0.9 meq/g, respectively. MEA was fabricated by hot-pressing, and was measured by electrochemical spectroscopy. PEFC performances at 60 degree of FN, Nafion 112 and s-FEP were evaluated. The power density of FN at 500 mA/cm2 and the maximum power density were about 1.1 times higher than those of Nafion 112, respectively.The membrane resistance and ion conductivity (IC) of MEAs were measured by 4-electrode AC impedance method. Ohmic resistance and charge transfer resistance of FN were lower than those of s-FEP. These indicate that interface properties

  6. Correlating variability of modeling parameters with non-isothermal stack performance: Monte Carlo simulation of a portable 3D planar solid oxide fuel cell stack

    International Nuclear Information System (INIS)

    Highlights: • A Monte Carlo simulation of a SOFC stack model is conducted for sensitivity analysis. • The non-isothermal stack model allows fast computation for statistical modeling. • Modeling parameters are ranked in view of their correlations with stack performance. • Rankings are different when varying the parameters simultaneously and individually. • Rankings change with the variability of the parameters and positions in the stack. - Abstract: The development of fuel cells has progressed to portable applications recently. This paper conducts a Monte Carlo simulation (MCS) of a spatially-smoothed non-isothermal model to correlate the performance of a 3D 5-cell planar solid oxide fuel cell (P-SOFC) stack with the variability of modeling parameters regarding material and geometrical properties and operating conditions. The computationally cost-efficient P-SOFC model for the MCS captures the leading-order transport phenomena and electrochemical mechanics of the 3D stack. Sensitivity analysis is carried out in two scenarios: first, by varying modeling parameters individually, and second by varying them simultaneously. The stochastic parameters are ranked according to the strength of their correlations with global and local stack performances. As a result, different rankings are obtained for the two scenarios. Moreover, in the second scenario, the rankings change with the nominal values and variability of the stochastic parameters as well as local positions within the stack, because of compensating or reinforcing effects between the varying parameters. Apart from the P-SOFCs, the present MCS can be extended to other types of fuel cells equipped with parallel flow channels. The fast stack model allows statistical modeling of a large stack of hundreds of cells for high-power applications without a prohibitive computational cost

  7. Development of internal manifold heat exchanger (IMHEX reg-sign) molten carbonate fuel cell stacks

    International Nuclear Information System (INIS)

    The Institute of Gas Technology (IGT) has been in the forefront of molten carbonate fuel cell (MCFC) development for over 25 years. Numerous cell designs have been tested and extensive tests have been performed on a variety of gas manifolding alternatives for cells and stacks. Based upon the results of these performance tests, IGT's development efforts started focusing on an internal gas manifolding concept. This work, initiated in 1988, is known today as the IMHEX reg-sign concept. MCP has developed a comprehensive commercialization program loading to the sale of commercial units in 1996. MCP's role is in the manufacture of stack components, stack assembly, MCFC subsystem testing, and the design, marketing and construction of MCFC power plants. Numerous subscale (1 ft2) stacks have been operated containing between 3 and 70 cells. These tests verified and demonstrated the viability of internal manifolding from technical (no carbonate pumping), engineering (relaxed part dimensional tolerance requirements), and operational (good gas sealing) aspects. Simplified fabrication, ease of assembly, the elimination of external manifolds and all associated clamping requirements has significantly lowered anticipated stack costs. Ongoing 1 ft2 stack testing is generating performance and endurance characteristics as a function of system specified operating conditions. Commercial-sized, full-area stacks (10 ft2) are in the process of being assembled and will be tested in November. This paper will review the recent developments the MCFC scale-up and manufacture work of MCP, and the research and development efforts of IGT which support those efforts. 17 figs

  8. Pt–Au/C cathode with enhanced oxygen-reduction activity in PEFCs

    Indian Academy of Sciences (India)

    G Selvarani; S Vinod Selvaganesh; P Sridhar; S Pitchumani; A K Shukla

    2011-04-01

    Carbon-supported Pt–Au (Pt–Au/C) catalyst is prepared separately by impregnation, colloidal and micro-emulsion methods, and characterized by physical and electrochemical methods. Highest catalytic activity towards oxygen-reduction reaction (ORR) is exhibited by Pt–Au/C catalyst prepared by colloidal method. The optimum atomic ratio of Pt to Au in Pt–Au/C catalyst prepared by colloidal method is determined using linear-sweep and cyclic voltammetry in conjunction with cell-polarization studies. Among 3:1, 2:1 and 1:1 Pt–Au/C catalysts, (3:1) Pt–Au/C exhibits maximum electrochemical activity towards ORR. Powder X-ray diffraction pattern and transmission electron micrograph suggest Pt–Au alloy nanoparticles to be well dispersed onto the carbon-support. Energy dispersive X-ray analysis and inductively coupled plasma-optical emission spectroscopy data suggest that the atomic ratios of the alloying elements match well with the expected values. A polymer electrolyte fuel cell (PEFC) operating at 0.6 V with (3:1) Pt–Au/C cathode delivers a maximum power-density of 0.65 W/cm2 in relation to 0.53 W/cm2 delivered by the PEFC with pristine carbon-supported Pt cathode.

  9. 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.)

  10. Design, fabrication and performance test of a planar array module-type micro fuel cell stack

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • A new and novel planar array module. • Easy handling/assembling as well as fast fabrication upon its commercialization. • Compact configuration design and geometry could be secured. - Abstract: We proposed and tested a new and novel planar array module (4 N style; N is an integer) consisting of 4, 8, 12 and 16 single polymer electrotype membrane (PEM) fuel cells connected in series on a plane with two different pin electrode flowfield configurations. This module has the potential to be not only easily handled and assembled but also to be fabricated quickly upon its commercialization. Using a Lithography Galvanic Abformung (LIGA)-like microfabrication technique, copper metal sheets were used to make two different flowfield plates with serpentine flow channels. A 4-cell (short stack), 8-cell, 12-cell and 16-cell (long stack) stack were developed and tested for performance study under different operating conditions. These were connected in a series of micro fuel cells consisting of an anode/cathode and Membrane Electrode Assembly (MEA). Performance results for a short stack/unit module (4 cells), 8 cells, 12 cells and a long stack/four modules (16 cells) were presented; it was found that significant improvements in VI/PI characteristics could be attained due to uniform and compact configuration design and geometry

  11. Sustainable Forest management: example of implementation of PEFC certification schemes

    Directory of Open Access Journals (Sweden)

    2006-01-01

    Full Text Available After a short description of forest certification standards, the Authors outline PEFC certification schemes implemented in a study-case (municipal forest of Montano Antilia, in the National Park of Cilento and Vallo di Diano, South of Italy, discussing the limited success of certification and some of the obstacles to its adoption in the specific case. One of the barriers for the adoption of forest certification is the lack of basic information, even in presence of the Forests Management Plan.

  12. Methane Steam Reforming over an Ni-YSZ Solid Oxide Fuel Cell Anode in Stack Configuration

    Directory of Open Access Journals (Sweden)

    D. Mogensen

    2014-01-01

    Full Text Available The kinetics of catalytic steam reforming of methane over an Ni-YSZ anode of a solid oxide fuel cell (SOFC have been investigated with the cell placed in a stack configuration. In order to decrease the degree of conversion, a single cell stack with reduced area was used. Measurements were performed in the temperature range 600–800°C and the partial pressures of all reactants and products were varied. The obtained rates could be well fitted with a power law expression (r ∝PCH40.7. A simple model is presented which is capable of predicting the methane conversion in a stack configuration from intrinsic kinetics of the anode support material. The predictions are compared with the stack measurements presented here, and good agreement is observed.

  13. Improved electrochemical in-situ characterization of polymer electrolyte membrane fuel cell stacks

    Science.gov (United States)

    Hartung, I.; Kirsch, S.; Zihrul, P.; Müller, O.; von Unwerth, T.

    2016-03-01

    In-situ diagnostics for single polymer electrolyte membrane fuel cells are well known and established. Comparable stack level techniques are urgently needed to enhance the understanding of degradation during real system operation, but have not yet reached a similar level of sophistication. We have therefore developed a new method for the quantification of the hydrogen crossover current in stacks, which in combination with a previously published technique now allows a clear quantitative characterization of the individual cells' membranes and electrodes. The limits of the reported methods are theoretically assessed and application is then demonstrated on automotive short stacks. The results prove to be highly reproducible and are validated for individual cells of the respective stacks by direct comparison with cyclic voltammetry results, showing good quantitative agreement for the hydrogen crossover current, the double layer capacitance and the electrochemically active surface area.

  14. A polymer electrolyte fuel cell stack for stationary power generation from hydrogen fuel

    Energy Technology Data Exchange (ETDEWEB)

    Zawodzinski, C.; Wilson, M.; Gottesfeld, S. [Los Alamos National Lab., NM (United States)

    1996-10-01

    The fuel cell is the most efficient device for the conversion of hydrogen fuel to electric power. As such, the fuel cell represents a key element in efforts to demonstrate and implement hydrogen fuel utilization for electric power generation. A central objective of a LANL/Industry collaborative effort supported by the Hydrogen Program is to integrate PEM fuel cell and novel stack designs at LANL with stack technology of H-Power Corporation (H-Power) in order to develop a manufacturable, low-cost/high-performance hydrogen/air fuel cell stack for stationary generation of electric power. A LANL/H-Power CRADA includes Tasks ranging from exchange, testing and optimization of membrane-electrode assemblies of large areas, development and demonstration of manufacturable flow field, backing and bipolar plate components, and testing of stacks at the 3-5 cell level and, finally, at the 4-5 kW level. The stack should demonstrate the basic features of manufacturability, overall low cost and high energy conversion efficiency. Plans for future work are to continue the CRADA work along the time line defined in a two-year program, to continue the LANL activities of developing and testing stainless steel hardware for longer term stability including testing in a stack, and to further enhance air cathode performance to achieve higher energy conversion efficiencies as required for stationary power application.

  15. Solid oxide fuel cells SOFCRoll single cell and stack design and development

    OpenAIRE

    Tesfai, Alem T.

    2013-01-01

    This study has focused on the implementation of a stack system for a novel design of solid oxide fuel cell (SOFCRoll). The issues affecting the commercialization of SOFCs are mainly based on durability and cost. The new design offers a number of advantages over the existing designs; it seeks to retain the specific advantages of both the tubular (high unit strength, no sealing problems) and planar arrangements (high power density). This design also aims to achieve low manufac...

  16. 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...

  17. An Evaluation Study of the Reduction Effects of the CO2 Emission Quantity and the Primary Energy in the Residential PEFC Co-generation System

    Science.gov (United States)

    Maeda, Kazushige; Yonemori, Hideto; Yasaka, Yasuyoshi

    This paper deals with the introduction effects on the basis of the comparative study of residential PEFC (polymer electrolyte fuel cell) co-generation systems and conventional systems that consist of a conventional gas boiler or a condensing gas boiler or a CO2 heat pump and the thermal power plant, by using the computer simulation. The target systems for estimation conform to real systems in the market and the energy demand data acquired from the past field tests was applied. As a result, it becomes clear that the residential PEFC co-generation systems have high performance in the energy saving and the CO2 reduction, from a comparison study with conventional systems and CO2 heat pump system. Concretely to say, the average energy saving rate that the residential PEFC co-generation system provides is 13.9% and the average CO2 reduction rate is 16.5% using quantity of reduction of CO2 as estimate function. Otherwise, the average energy saving rate that the CO2 heat pump system provides is 13.7% and the average CO2 reduction rate is 10.0%. Furthermore, we have proved the effectiveness a radiator in the residential PEFC co-generation system.

  18. Identification and analysis based on genetic algorithm for proton exchange membrane fuel cell stack

    Institute of Scientific and Technical Information of China (English)

    LI Xi; CAO Guang-yi; ZHU Xin-jian; WEI Dong

    2006-01-01

    The temperature of proton exchange membrane fuel cell stack and the stoichiometric oxygen in cathode have relationship with the performance and life span of fuel cells closely. The thermal coefficients were taken as important factors affecting the temperature distribution of fuel cells and components. According to the experimental analysis, when the stoichiometric oxygen in cathode is greater than or equal to 1.8, the stack voltage loss is the least. A novel genetic algorithm was developed to identify and optimize the variables in dynamic thermal model of proton exchange membrane fuel cell stack, making the outputs of temperature model approximate to the actual temperature, and ensuring that the maximal error is less than 1℃. At the same time, the optimum region of stoichiometric oxygen is obtained, which is in the range of 1.8 -2.2 and accords with the experimental analysis results. The simulation and experimental results show the effectiveness of the proposed algorithm.

  19. Methane Steam Reforming over an Ni-YSZ Solid Oxide Fuel Cell Anode in Stack Configuration

    DEFF Research Database (Denmark)

    Mogensen, David; Grunwaldt, Jan-Dierk; Hendriksen, Peter Vang;

    2014-01-01

    The kinetics of catalytic steam reforming of methane over an Ni-YSZ anode of a solid oxide fuel cell (SOFC) have been investigated with the cell placed in a stack configuration. In order to decrease the degree of conversion, a single cell stack with reduced area was used. Measurements were...... performed in the temperature range 600-800 degrees C and the partial pressures of all reactants and products were varied. The obtained rates could be well fitted with a power law expression (r proportional to P-CH4(0.7)). A simple model is presented which is capable of predicting the methane conversion in a...

  20. Methane Steam Reforming over an Ni-YSZ Solid Oxide Fuel Cell Anode in Stack Configuration

    OpenAIRE

    Mogensen, D.; J.-D. Grunwaldt; Hendriksen, P. V.; J. U. Nielsen; K. Dam-Johansen

    2014-01-01

    The kinetics of catalytic steam reforming of methane over an Ni-YSZ anode of a solid oxide fuel cell (SOFC) have been investigated with the cell placed in a stack configuration. In order to decrease the degree of conversion, a single cell stack with reduced area was used. Measurements were performed in the temperature range 600-800 degrees C and the partial pressures of all reactants and products were varied. The obtained rates could be well fitted with a power law expression (r proportional ...

  1. 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.

  2. Water transport during startup and shutdown of polymer electrolyte fuel cell stacks

    Energy Technology Data Exchange (ETDEWEB)

    Wang, X.; Tajiri, K.; Ahluwalia, R.K. [Argonne National Laboratory, 9700 S Cass Avenue, Argonne, IL 60439 (United States)

    2010-10-01

    A dynamic three-phase transport model is developed to analyze water uptake and transport in the membrane and catalyst layers of polymer electrolyte fuel cells during startup from subfreezing temperatures and subsequent shutdown. The initial membrane water content ({lambda}, the number of water molecules per sulfonic acid site) is found to be an important parameter that determines whether a successful unassisted self-start is possible. For a given initial subfreezing temperature at startup, there is a critical {lambda} ({lambda}{sub h}), above which self-start is not possible because the product water completely engulfs the catalyst layers with ice before the stack can warm-up to 0 C. There is a second value of {lambda} ({lambda}{sub l}), below which the stack can be self-started without forming ice. Between {lambda}{sub l} and {lambda}{sub h}, the stack can be self-started, but with intermediate formation of ice that melts as the stack warms up to 0 C. Both {lambda}{sub l} and {lambda}{sub h} are functions of the initial stack temperature, cell voltage at startup, membrane thickness, catalyst loading, and stack heat capacity. If the stack is purged during the previous shutdown by flowing air in the cathode passages, then depending on the initial amount of water in the membrane and gas diffusion layers and the initial stack temperature, it may not be possible to dry the membrane to the critical {lambda} for a subsequent successful startup. There is an optimum {lambda} for robust and rapid startup and shutdown. Startup and shutdown time and energy may be unacceptable if the {lambda} is much less than the optimum. Conversely, a robust startup from subfreezing temperatures cannot be assured if the {lambda} is much higher than this optimum. (author)

  3. Water transport during startup and shutdown of polymer electrolyte fuel cell stacks.

    Energy Technology Data Exchange (ETDEWEB)

    Wang, X.; Tajiri, K.; Ahluwalia, R.; Nuclear Engineering Division

    2010-10-01

    A dynamic three-phase transport model is developed to analyze water uptake and transport in the membrane and catalyst layers of polymer electrolyte fuel cells during startup from subfreezing temperatures and subsequent shutdown. The initial membrane water content (?, the number of water molecules per sulfonic acid site) is found to be an important parameter that determines whether a successful unassisted self-start is possible. For a given initial subfreezing temperature at startup, there is a critical ? (?h), above which self-start is not possible because the product water completely engulfs the catalyst layers with ice before the stack can warm-up to 0 C. There is a second value of ? (?l), below which the stack can be self-started without forming ice. Between ?l and ?h, the stack can be self-started, but with intermediate formation of ice that melts as the stack warms up to 0 C. Both ?l and ?h are functions of the initial stack temperature, cell voltage at startup, membrane thickness, catalyst loading, and stack heat capacity. If the stack is purged during the previous shutdown by flowing air in the cathode passages, then depending on the initial amount of water in the membrane and gas diffusion layers and the initial stack temperature, it may not be possible to dry the membrane to the critical ? for a subsequent successful startup. There is an optimum ? for robust and rapid startup and shutdown. Startup and shutdown time and energy may be unacceptable if the ? is much less than the optimum. Conversely, a robust startup from subfreezing temperatures cannot be assured if the ? is much higher than this optimum.

  4. A polymer electrolyte fuel cell stack for stationary power generation from hydrogen fuel

    Energy Technology Data Exchange (ETDEWEB)

    Gottesfeld, S. [Los Alamos National Lab., NM (United States)

    1995-09-01

    The fuel cell is the most efficient device for the conversion of hydrogen fuel to electric power. As such, the fuel cell represents a key element in efforts to demonstrate and implement hydrogen fuel utilization for electric power generation. The low temperature, polymer electrolyte membrane fuel cell (PEMFC) has recently been identified as an attractive option for stationary power generation, based on the relatively simple and benign materials employed, the zero-emission character of the device, and the expected high power density, high reliability and low cost. However, a PEMFC stack fueled by hydrogen with the combined properties of low cost, high performance and high reliability has not yet been demonstrated. Demonstration of such a stack will remove a significant barrier to implementation of this advanced technology for electric power generation from hydrogen. Work done in the past at LANL on the development of components and materials, particularly on advanced membrane/electrode assemblies (MEAs), has contributed significantly to the capability to demonstrate in the foreseeable future a PEMFC stack with the combined characteristics described above. A joint effort between LANL and an industrial stack manufacturer will result in the demonstration of such a fuel cell stack for stationary power generation. The stack could operate on hydrogen fuel derived from either natural gas or from renewable sources. The technical plan includes collaboration with a stack manufacturer (CRADA). It stresses the special requirements from a PEMFC in stationary power generation, particularly maximization of the energy conversion efficiency, extension of useful life to the 10 hours time scale and tolerance to impurities from the reforming of natural gas.

  5. Optimized scalable stack of fluorescent solar concentrator systems with bifacial silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Martínez Díez, Ana Luisa, E-mail: a.martinez@itma.es [Fundación ITMA, Parque Empresarial Principado de Asturias, C/Calafates, Parcela L-3.4, 33417 Avilés (Spain); Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstr. 2, 79110 Freiburg (Germany); Gutmann, Johannes; Posdziech, Janina; Rist, Tim; Goldschmidt, Jan Christoph [Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstr. 2, 79110 Freiburg (Germany); Plaza, David Gómez [Fundación ITMA, Parque Empresarial Principado de Asturias, C/Calafates, Parcela L-3.4, 33417 Avilés (Spain)

    2014-10-21

    In this paper, we present a concentrator system based on a stack of fluorescent concentrators (FCs) and a bifacial solar cell. Coupling bifacial solar cells to a stack of FCs increases the performance of the system and preserves its efficiency when scaled. We used an approach to optimize a fluorescent solar concentrator system design based on a stack of multiple fluorescent concentrators (FC). Seven individual fluorescent collectors (20 mm×20 mm×2 mm) were realized by in-situ polymerization and optically characterized in regard to their ability to guide light to the edges. Then, an optimization procedure based on the experimental data of the individual FCs was carried out to determine the stack configuration that maximizes the total number of photons leaving edges. Finally, two fluorescent concentrator systems were realized by attaching bifacial silicon solar cells to the optimized FC stacks: a conventional system, where FC were attached to one side of the solar cell as a reference, and the proposed bifacial configuration. It was found that for the same overall FC area, the bifacial configuration increases the short-circuit current by a factor of 2.2, which is also in agreement with theoretical considerations.

  6. Optimized scalable stack of fluorescent solar concentrator systems with bifacial silicon solar cells

    Science.gov (United States)

    Martínez Díez, Ana Luisa; Gutmann, Johannes; Posdziech, Janina; Rist, Tim; Plaza, David Gómez; Goldschmidt, Jan Christoph

    2014-10-01

    In this paper, we present a concentrator system based on a stack of fluorescent concentrators (FCs) and a bifacial solar cell. Coupling bifacial solar cells to a stack of FCs increases the performance of the system and preserves its efficiency when scaled. We used an approach to optimize a fluorescent solar concentrator system design based on a stack of multiple fluorescent concentrators (FC). Seven individual fluorescent collectors (20 mm × 20 mm × 2 mm) were realized by in-situ polymerization and optically characterized in regard to their ability to guide light to the edges. Then, an optimization procedure based on the experimental data of the individual FCs was carried out to determine the stack configuration that maximizes the total number of photons leaving edges. Finally, two fluorescent concentrator systems were realized by attaching bifacial silicon solar cells to the optimized FC stacks: a conventional system, where FC were attached to one side of the solar cell as a reference, and the proposed bifacial configuration. It was found that for the same overall FC area, the bifacial configuration increases the short-circuit current by a factor of 2.2, which is also in agreement with theoretical considerations.

  7. Optimized scalable stack of fluorescent solar concentrator systems with bifacial silicon solar cells

    International Nuclear Information System (INIS)

    In this paper, we present a concentrator system based on a stack of fluorescent concentrators (FCs) and a bifacial solar cell. Coupling bifacial solar cells to a stack of FCs increases the performance of the system and preserves its efficiency when scaled. We used an approach to optimize a fluorescent solar concentrator system design based on a stack of multiple fluorescent concentrators (FC). Seven individual fluorescent collectors (20 mm × 20 mm × 2 mm) were realized by in-situ polymerization and optically characterized in regard to their ability to guide light to the edges. Then, an optimization procedure based on the experimental data of the individual FCs was carried out to determine the stack configuration that maximizes the total number of photons leaving edges. Finally, two fluorescent concentrator systems were realized by attaching bifacial silicon solar cells to the optimized FC stacks: a conventional system, where FC were attached to one side of the solar cell as a reference, and the proposed bifacial configuration. It was found that for the same overall FC area, the bifacial configuration increases the short-circuit current by a factor of 2.2, which is also in agreement with theoretical considerations.

  8. Analysis and Improvement of a Scaled-Up and Stacked Microbial Fuel Cell

    NARCIS (Netherlands)

    Dekker, A.J.G.; Heijne, ter A.; Saakes, M.; Hamelers, H.V.M.; Buisman, C.J.N.

    2009-01-01

    Scaling up microbial fuel cells (MFCs) is inevitable when power outputs have to be obtained that can power electrical devices other than small sensors. This research has used a bipolar plate MFC stack of four cells with a total working volume of 20 L and a total membrane surface area of 2 m2. The ca

  9. Fuel cell system including a unit for electrical isolation of a fuel cell stack from a manifold assembly and method therefor

    Science.gov (United States)

    Kelley; Dana A. , Farooque; Mohammad , Davis; Keith

    2007-10-02

    A fuel cell system with improved electrical isolation having a fuel cell stack with a positive potential end and a negative potential, a manifold for use in coupling gases to and from a face of the fuel cell stack, an electrical isolating assembly for electrically isolating the manifold from the stack, and a unit for adjusting an electrical potential of the manifold such as to impede the flow of electrolyte from the stack across the isolating assembly.

  10. Using qualimetric engineering and extremal analysis to optimize a proton exchange membrane fuel cell stack

    International Nuclear Information System (INIS)

    Highlights: • We consider the optimal configuration of a PEMFC stack. • We utilize qualimetric engineering tools (Taguchi screening, regression analysis). • We achieve analytical solution on a restructured power-law fitting. • We discuss the Pt-cost involvement in the unit and area minimization scope. - Abstract: The optimal configuration of the proton exchange membrane fuel-cell (PEMFC) stack has received attention recently because of its potential use as an isolated energy distributor for household needs. In this work, the original complex problem for generating an optimal PEMFC stack based on the number of cell units connected in series and parallel arrangements as well as on the cell area is revisited. A qualimetric engineering strategy is formulated which is based on quick profiling the PEMFC stack voltage response. Stochastic screening is initiated by employing an L9(33) Taguchi-type OA for partitioning numerically the deterministic expression of the output PEMFC stack voltage such that to facilitate the sizing of the magnitude of the individual effects. The power and current household specifications for the stack system are maintained at the typical settings of 200 W at 12 V, respectively. The minimization of the stack total-area requirement becomes explicit in this work. The relationship of cell voltage against cell area is cast into a power-law model by regression fitting that achieves a coefficient of determination value of 99.99%. Thus, the theoretical formulation simplifies into a non-linear extremal problem with a constrained solution due to a singularity which is solved analytically. The optimal solution requires 22 cell units connected in series where each unit is designed with an area value of 151.4 cm2. It is also demonstrated how to visualize the optimal solution using the graphical method of operating lines. The total area of 3270.24 cm2 becomes a new benchmark for the optimal design of the studied PEMFC stack configuration. It is

  11. PEFC COC -sertifioinnin hakeminen : case: Kotkan Viilutehdas KVT Oy

    OpenAIRE

    Lappalainen, Markku

    2016-01-01

    Opinnäytetyön tarkoituksena oli selvittää tarkasteluhetkellä Kotkan Viilutehdas KVT Oy:n mahdollisuuksia hakea puun alkuperän seuranta- järjestelmän mukaista PEFC CoC -sertifiointia, Programme for the Endorsement of Forest Certification, Chain of Custody, siihen liittyviä viranomaismääräyksiä, kustannuksia ja vaikutuksia tuotantoon sekä markkinatilannetta haastatellun asiakaskunnan kannalta. Toimeksiantajayrityksen toimintaan perehdyttiin työskentelemällä yrityksessä syksyn 2015 aikana. ...

  12. Pressurized Testing of Solid Oxide Electrolysis Stacks with Advanced Electrode-Supported Cells

    Energy Technology Data Exchange (ETDEWEB)

    J. E. O' Brien; X. Zhang; G. K. Housley; K. DeWall; L. Moore-McAteer; G. Tao

    2012-06-01

    A new facility has been developed at the Idaho National Laboratory for pressurized testing of solid oxide electrolysis stacks. Pressurized operation is envisioned for large-scale hydrogen production plants, yielding higher overall efficiencies when the hydrogen product is to be delivered at elevated pressure for tank storage or pipelines. Pressurized operation also supports higher mass flow rates of the process gases with smaller components. The test stand can accommodate cell dimensions up to 8.5 cm x 8.5 cm and stacks of up to 25 cells. The pressure boundary for these tests is a water-cooled spool-piece pressure vessel designed for operation up to 5 MPa. The stack is internally manifolded and operates in cross-flow with an inverted-U flow pattern. Feed-throughs for gas inlets/outlets, power, and instrumentation are all located in the bottom flange. The entire spool piece, with the exception of the bottom flange, can be lifted to allow access to the internal furnace and test fixture. Lifting is accomplished with a motorized threaded drive mechanism attached to a rigid structural frame. Stack mechanical compression is accomplished using springs that are located inside of the pressure boundary, but outside of the hot zone. Initial stack heatup and performance characterization occurs at ambient pressure followed by lowering and sealing of the pressure vessel and subsequent pressurization. Pressure equalization between the anode and cathode sides of the cells and the stack surroundings is ensured by combining all of the process gases downstream of the stack. Steady pressure is maintained by means of a backpressure regulator and a digital pressure controller. A full description of the pressurized test apparatus is provided in this paper.

  13. A parametric study of the natural vibration and mode shapes of PEM fuel cell stacks

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2016-01-01

    Full Text Available A PEM fuel cell stack is laminated with a number of plate-type cells, and the latest model is assembled by compression from both ends of plates.PEM fuel cells are exposed to high magnitude vibrations, shocks, and cyclic loads in many applications. Vibrations during operation show significant impact in the longer run of the fuel cells. Frequencies which are not close to the resonant frequencies or natural frequencies show very little effect on the overall performance. However, if the frequency ranges of operation approaches the resonant frequency range, the probability of component failure increases. It is possible that there will be lateral transition of cells or leakage of fuel gas and coolant water. Therefore, it is necessary to evaluate the effects vibration has on the fuel cell. This work aims to understand the vibration characteristics of a PEM fuel cell stack and to evaluate their seismic resistance under a vibration environment. Natural frequencies and mode shapes of the PEM fuel cell stack are modelling using finite element methods (FEM.A parametric study is conducted to investigate how the natural frequency varies as a function of thickness, Young’s modulus, and density for each component layer. In addition, this work provides insight into how the natural frequencies of the PEM fuel cell stack should be tuned to avoid high amplitude vibrations by modifying the material and geometric properties of individual components. The mode shapes of the PEM fuel cell stack provide insight into the maximum displacement exhibited under vibration conditions that should be considered for transportation and stationary applications.

  14. Fuel cell program - Overview reports 2007; Programm Brennstoffzellen inkl. Wasserstoff - Ueberblicksberichte der BFE-Programmleiter 2007

    Energy Technology Data Exchange (ETDEWEB)

    Luzzi, A.; Spirig, M.

    2008-07-01

    This report for the Swiss Federal Office of Energy (SFOE) presents the overview reports made by SFOE Heads of Program on work done in 2007. Projects reported on in the natural gas-fired fuel cell area include the EU-project REAL-SFOC, the long-term testing of anode-supported SOFC stacks, intermediate-temperature fuel cells based on proton conducting electrolytes, the interdisciplinary ONEBAT project and lifetime-enhancement of SOFC stacks for CHP applications. In the polymer-electrolyte fuel cell (PEFC) area, projects concerning proton-conducting polymer membranes, factors limiting the lifetime of fuel cell membranes, a new highly active oxygen reduction electrode for PEM fuel cell and zinc/air battery applications, the enhancement of PEFC durability and reliability, model-based investigation of PEFC performance, and local gas analysis of PE fuel cells are briefly reported on. Long-term research activities in the hydrogen technology area reported on include those concerning the photo-chemical conversion and storage of solar energy and the storage of hydrogen in metallic and complex hydrides. Further projects reported on include those concerning the physical aspects of hydrides for system integration and safety and new, complex metal hydrides. Swiss national and international co-ordination is reviewed in the areas of fuel cell technology and hydrogen technology. Work done in several projects run within the framework of the IEA's Advanced Fuel Cells Program is reviewed. Several pilot and demonstration (P and D) projects are also reported on in the natural-gas SOFC and PEFC areas. Comments on the 2007 results and a review of work to be done in 2008, along with a list of R, D, P and D projects, complete the report.

  15. Pressurized Operation of a Planar Solid Oxide Cell Stack

    DEFF Research Database (Denmark)

    Jensen, Søren Højgaard; Sun, Xiufu; Ebbesen, Sune Dalgaard;

    2016-01-01

    Solid oxide cells (SOCs) can be operated either as fuel cells (SOFC) to convert fuels to electricity or as electrolyzers (SOEC) to convert electricity to fuels such as hydrogen or methane. Pressurized operation of SOCs provide several benefits on both cell and system level. If successfully matured...

  16. Modelling the impact of creep on the probability of failure of a solid oxidefuel cell stack

    DEFF Research Database (Denmark)

    Greco, Fabio; Frandsen, Henrik Lund; Nakajo, Arata; Madsen, Mads Find; Van herle, Jan

    2014-01-01

    In solid oxide fuel cell (SOFC) technology a major challenge lies in balancing thermal stresses from an inevitable thermal field. The cells are known to creep, changing over time the stress field. The main objective of this study was to assess the influence of creep on the failure probability of an...... SOFC stack. A finite element analysis on a single repeating unit of the stack was performed, in which the influence of the mechanical interactions,the temperature-dependent mechanical properties and creep of the SOFC materials are considered. Moreover, stresses from the thermo-mechanical simulation of...... sintering of the cells have been obtained and were implemented into the model of the single repeating unit. The significance of the relaxation of the stresses by creep in the cell components and its influence on the probability of cell survival was investigated. Finally, the influence of cell size on the...

  17. Stack configurations for tubular solid oxide fuel cells

    Science.gov (United States)

    Armstrong, Timothy R.; Trammell, Michael P.; Marasco, Joseph A.

    2010-08-31

    A fuel cell unit includes an array of solid oxide fuel cell tubes having porous metallic exterior surfaces, interior fuel cell layers, and interior surfaces, each of the tubes having at least one open end; and, at least one header in operable communication with the array of solid oxide fuel cell tubes for directing a first reactive gas into contact with the porous metallic exterior surfaces and for directing a second reactive gas into contact with the interior surfaces, the header further including at least one busbar disposed in electrical contact with at least one surface selected from the group consisting of the porous metallic exterior surfaces and the interior surfaces.

  18. Optimum design of bipolar plates for separate air flow cooling system of PEM fuel cells stacks

    Science.gov (United States)

    Franco, Alessandro

    2015-12-01

    The paper discusses about thermal management of PEM fuel cells. The objective is to define criteria and guidelines for the design of the air flow cooling system of fuel cells stacks for different combination of power density, bipolar plates material, air flow rate, operating temperature It is shown that the optimization of the geometry of the channel permits interesting margins for maintaining the use of separate air flow cooling systems for high power density PEM fuel cells.

  19. Parametric Sensitivity Tests—European Polymer Electrolyte Membrane Fuel Cell Stack Test Procedures

    DEFF Research Database (Denmark)

    Araya, Samuel Simon; Andreasen, Søren Juhl; Kær, Søren Knudsen

    2014-01-01

    As fuel cells are increasingly commercialized for various applications, harmonized and industry-relevant test procedures are necessary to benchmark tests and to ensure comparability of stack performance results from different parties. This paper reports the results of parametric sensitivity tests...

  20. Solid Oxide Cell and Stack Testing, Safety and Quality Assurance (SOCTESQA)

    DEFF Research Database (Denmark)

    Auer, C.; Lang, M.; Couturier, K.;

    2015-01-01

    /stack assembly in the fuel cell (SOFC), in the electrolysis (SOEC) and in the combined SOFC/SOEC mode are addressed. This covers the wide field of power generation systems, e.g. stationary SOFC µ-CHP, mobile SOFC APU and SOFC/SOEC power-to-gas systems. This paper presents the results which have been achieved so...

  1. Prognostics of Proton Exchange Membrane Fuel Cells stack using an ensemble of constraints based connectionist networks

    Science.gov (United States)

    Javed, Kamran; Gouriveau, Rafael; Zerhouni, Noureddine; Hissel, Daniel

    2016-08-01

    Proton Exchange Membrane Fuel Cell (PEMFC) is considered the most versatile among available fuel cell technologies, which qualify for diverse applications. However, the large-scale industrial deployment of PEMFCs is limited due to their short life span and high exploitation costs. Therefore, ensuring fuel cell service for a long duration is of vital importance, which has led to Prognostics and Health Management of fuel cells. More precisely, prognostics of PEMFC is major area of focus nowadays, which aims at identifying degradation of PEMFC stack at early stages and estimating its Remaining Useful Life (RUL) for life cycle management. This paper presents a data-driven approach for prognostics of PEMFC stack using an ensemble of constraint based Summation Wavelet- Extreme Learning Machine (SW-ELM) models. This development aim at improving the robustness and applicability of prognostics of PEMFC for an online application, with limited learning data. The proposed approach is applied to real data from two different PEMFC stacks and compared with ensembles of well known connectionist algorithms. The results comparison on long-term prognostics of both PEMFC stacks validates our proposition.

  2. Unsteady 2D PEM fuel cell modeling for a stack emphasizing thermal effects

    Energy Technology Data Exchange (ETDEWEB)

    Shan, Yuyao; Choe, Song-Yul [Department of Mechanical Engineering, Auburn University, Auburn (United States); Choi, Seo-Ho [Fuel Cell Vehicle Team, Hyundai Motor Company and Kia Motors Corporation (United States)

    2007-02-25

    Models currently used for analyses of thermal and water behavior of a PEM fuel cell are based 3D computational fluid dynamics (CFD). However, the analyses are limited to a single cell with static behavior. Thus, these models cannot be used for analyses of dynamic behavior of a stack that continuously varies according to operating conditions. The model proposed describes dynamic behavior of a stack with two adjoining cells and endplate assembly, and work as a current controlled voltage source that can be used for optimization of BOPs and the associated controls. Simulations have been conducted to analyze start-up behaviors and the performance of the stack. Our analyses deliver following results: (1) dynamic temperature distribution in both the through-plane direction and the along channel direction of the fuel cell stack, (2) effects influencing the source terms of current density, and (3) dynamic oxygen concentration distribution. The temperature profile and its variation propensity are comparable to the previous results [Y. Shan, S.Y. Choe, J. Power Sources, 145 (1) (2005) 30-39; Y. Shan, S.Y. Choe, J. Power Sources, in press]. (author)

  3. Accelerated testing of solid oxide fuel cell stacks for micro combined heat and power application

    DEFF Research Database (Denmark)

    Hagen, Anke; Høgh, Jens Valdemar Thorvald; Barfod, Rasmus

    2015-01-01

    State-of-the-art (SoA) solid oxide fuel cell (SOFC) stacks are tested using profiles relevant for use in micro combined heat and power (CHP) units. Such applications are characterised by dynamic load profiles. In order to shorten the needed testing time and to investigate potential acceleration of...

  4. 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

    In designing and controlling fuel cell systems it is advantageous having models predicting fuel cell behavior in steady-state as well as in dynamic operation. This work examines the use of Electro-chemical Impedance Spectroscopy (EIS) for characterizing and developing an impedance model for a high...... used to predict the fuel cell stack performance, e.g. in systems where different electronic components introduce current harmonics....... 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 of...

  5. A “4-cell” modular passive DMFC (direct methanol fuel cell) stack for portable applications

    International Nuclear Information System (INIS)

    A “4-cell” modular passive DMFC (direct methanol fuel cell) stack, which can be freely combined and applied to various electronic devices, is designed, fabricated and tested. Two PCB (printed circuit board) based accessories are designed and fabricated for electrically connecting and mechanically assembling the “4-cell” modules. The maximum power density of the “4-cell” module is 27 mW cm−2 at 5 M methanol concentration. The steady-state performances of the modular stacks with different numbers of modules are tested. The extra power loss of the multiple module stacks due to inter-module electrical connections is predicted by mathematical fitting method. The fitting results indicate that the efficiencies of the multiple module stacks are all above 90% up to 10 modules. The dynamic performances of the modular stacks are also investigated for portable applications. The results show that the modular stacks exhibit good responsiveness and reproducibility at high loading current (>100 mA). Finally, the modular stacks are successfully applied to drive the experimental fan and charge the mobile phone. - Highlights: • A “4-cell” modular passive DMFC (direct methanol fuel cell) stack is designed, fabricated and tested. • This modular DMFC stack can assemble more single cells with high efficiency. • The modular stack exhibit good responsiveness and reproducibility for portable application

  6. Carrier recombination effects in strain compensated quantum dot stacks embedded in solar cells

    OpenAIRE

    Alonso Alvarez, Diego; González Taboada, Alfonso; Ripalda Cobián, Jose María; Alén Millán, Benito; González Diez, M. Yolanda; González Soto, Luisa; García Martín, Jorge Miguel; Martí Vega, Antonio; Luque López, Antonio; Briones Fernández-Pola, Fernando; Sanchez, A. M.; Molina Rubio, Sergio Ignacio

    2008-01-01

    In this work we report the stacking of 50 InAs/GaAs quantum dot layers with a GaAs spacer thickness of 18 nm using GaP monolayers for strain compensation. We find a good structural and optical quality of the fabricated samples including a planar growth front across the whole structure, a reduction in the quantum dot size inhomogeneity, and an enhanced thermal stability of the emission. The optimized quantum dot stack has been embedded in a solar cell structure and we discuss the benefits and ...

  7. Identification of critical stacking faults in thin-film CdTe solar cells

    International Nuclear Information System (INIS)

    Cadmium telluride (CdTe) is a p-type semiconductor used in thin-film solar cells. To achieve high light-to-electricity conversion, annealing in the presence of CdCl2 is essential, but the underlying mechanism is still under debate. Recent evidence suggests that a reduction in the high density of stacking faults in the CdTe grains is a key process that occurs during the chemical treatment. A range of stacking faults, including intrinsic, extrinsic, and twin boundary, are computationally investigated to identify the extended defects that limit performance. The low-energy faults are found to be electrically benign, while a number of higher energy faults, consistent with atomic-resolution micrographs, are predicted to be hole traps with fluctuations in the local electrostatic potential. It is expected that stacking faults will also be important for other thin-film photovoltaic technologies

  8. Scaled-up dual anode/cathode microbial fuel cell stack for actual ethanolamine wastewater treatment.

    Science.gov (United States)

    An, Byung-Min; Heo, Yoon; Maitlo, Hubdar-Ali; Park, Joo-Yang

    2016-06-01

    The aim of this work was to develop the scale-up microbial fuel cell technology for actual ethanolamine wastewater treatment, dual anode/cathode MFC stacks connected in series to achieve any desired current, treatment capacity, and volume capacity. However, after feeding actual wastewater into the MFC, maximum power density decreased while the corresponding internal resistance increased. With continuous electricity production, a stack of eight MFCs in series achieved 96.05% of COD removal and 97.30% of ammonia removal at a flow rate of 15.98L/d (HRT 12h). The scaled-up dual anode/cathode MFC stack system in this research was demonstrated to treat actual ETA wastewater with the added benefit of harvesting electricity energy. PMID:26888335

  9. Hybrid Dynamic Modeling and Control of Molten Carbonate Fuel Cell Stack Shutdown

    Institute of Scientific and Technical Information of China (English)

    LI Yong; CAO Guang-yi; ZHU Xin-jian

    2007-01-01

    A hybrid automaton modeling approach that incorporates state space partitioning, phase dynamic modeling and control law synthesis by control strategy is utilized to develop a hybrid automaton model of molten carbonate fuel cell (MCFC) stack shutdown. The shutdown operation is divided into several phases and their boundaries are decided according to a control strategy, which is a set of specifications about the dynamics of MCFC stack during shutdown. According to the control strategy, the specification of increasing stack temperature is satisfied in a phase that can be modeled accurately. The model for phase that has complex dynamic is approximated. The duration of this kind of phase is decreased to minimize the error caused by model approximation.

  10. A novel pilot-scale stacked microbial fuel cell for efficient electricity generation and wastewater treatment.

    Science.gov (United States)

    Wu, Shijia; Li, Hui; Zhou, Xuechen; Liang, Peng; Zhang, Xiaoyuan; Jiang, Yong; Huang, Xia

    2016-07-01

    A novel stacked microbial fuel cell (MFC) which had a total volume of 72 L with granular activated carbon (GAC) packed bed electrodes was constructed and verified to present remarkable power generation and COD removal performance due to its advantageous design of stack and electrode configuration. During the fed-batch operation period, a power density of 50.9 ± 1.7 W/m(3) and a COD removal efficiency of 97% were achieved within 48 h. Because of the differences among MFC modules in the stack, reversal current occurred in parallel circuit connection with high external resistances (>100 Ω). This reversal current consequently reduced the electrochemical performance of some MFC modules and led to a lower power density in parallel circuit connection than that in independent circuit connection. While increasing the influent COD concentrations from 200 to 800 mg/L at hydraulic retention time of 1.25 h in continuous operation mode, the power density of stacked MFC increased from 25.6 ± 2.5 to 42.1 ± 1.2 W/m(3) and the COD removal rates increased from 1.3 to 5.2 kg COD/(m(3) d). This study demonstrated that this novel MFC stack configuration coupling with GAC packed bed electrode could be a feasible strategy to effectively scale up MFC systems. PMID:27131320

  11. Dynamic modeling and experimental investigation of a high temperature PEM fuel cell stack

    DEFF Research Database (Denmark)

    Sahlin, Simon Lennart

    2016-01-01

    High temperature polymer fuel cells operating at 100 to 200◦C require simple fuel processing and produce high quality heat that can integrate well with domestic heating systems. Because the transportation of hydrogen is challenging, an alternative option is to reform natural gas on site. This...... article presents the development of a dynamic model and the comparison with experimental data from a high temperature proton exchange membrane fuel cell stack operating on hydrogen with carbon monoxide concentrations up to 0.8%, and temperatures from 155 to 175◦C. The dynamic response of the fuel cell is...... investigated with simulated reformate gas. The dynamic response of the fuel cell stack was compared with a step change in current from 0.09 to 0.18 and back to 0.09 A/cm2 . This article shows that the dynamic model calculates the voltage at steady state well. The dynamic response for a change in current shows...

  12. Analysis of Entropy Generation for the Performance Improvement of a Tubular Solid Oxide Fuel Cell Stack

    Directory of Open Access Journals (Sweden)

    Vittorio Verda

    2009-03-01

    Full Text Available The aim of the paper is to investigate possible improvements in the design and operation of a tubular solid oxide fuel cell. To achieve this purpose, a CFD model of the cell is introduced. The model includes thermo-fluid dynamics, chemical reactions and electrochemistry. The fluid composition and mass flow rates at the inlet sections are obtained through a finite difference model of the whole stack. This model also provides boundary conditions for the radiation heat transfer. All of these conditions account for the position of each cell within the stack. The analysis of the cell performances is conducted on the basis of the entropy generation. The use of this technique makes it possible to identify the phenomena provoking the main irreversibilities, understand their causes and propose changes in the system design and operation.

  13. Dynamic cell performance of kW-grade proton exchange membrane fuel cell stack with dead-ended anode

    International Nuclear Information System (INIS)

    Highlights: • A kW-grade fuel cell stack with anode dead-ended mode was examined. • The dead-ended anode is achieved by controlling the anode outlet solenoid valve. • Results indicated an optimal purge interval and duration for cell performance. - Abstract: This paper examines the dynamic cell performance of a kW-grade proton exchange membrane fuel cell stack with anode dead-ended mode fuel supply. A self-made kW-grade 40 cells stack with reaction area of 112.85 cm2 has been used in the experiment. A single-chip (DSPIC30F4011) is utilized for establishing a control circuit to monitor the voltage and current with constant-current loading. The stack temperature is controlled at a low-level temperature rise. To enhance the hydrogen utilization and reduce the water flooding in the fuel cell stack, the dead-ended anode operation is accomplished by controlling the open or close of the anode outlet solenoid valve. As the loading is heavy, the anode outlet solenoid valve is purged frequently to force the water to flow out. While a light load, the anode outlet solenoid valve is shut down for a period time for hydrogen saving. The solenoid valve is controlled to be opened, referred as purge interval, reaching the discharge amount for 1000 C, 1500 C, and 2000 C as parameter, respectively. The open period of solenoid valve, referred as purge duration, is set as 1 s, 3 s, and 5 s for this study. Experimental results indicate an optimal purge interval and duration for water management and cell performance of the fuel cell stack

  14. Flow distribution measurements at the exit of bipolar plates in a PEM fuel cell stack; Messung der Stroemungsverteilung am Austritt der Bipolarplatten eines Brennstoffzellen-Stacks

    Energy Technology Data Exchange (ETDEWEB)

    Klinner, Joachim; Willert, Christian [DLR Deutsches Zentrum fuer Luft- und Raumfahrt e.V., Koeln (Germany). Abt. Triebwerksmesstechnik; Schneider, Armin; Mack-Gardner, Andre [Adam Opel GmbH, Ruesselsheim (Germany). Alternative Propulsion Center Europe

    2011-07-01

    This paper presents two different experimental approaches which concentrate on capturing the flow distribution close to the anode exit header of a prototype 8-12 KW fuel cell stack operated with air at realistic flow rates. The first approach intends to visualize the penetration depth of millimeter-sized jets towards the exit manifold. The second one is focused on obtaining the exit jet velocity field downstream of the bipolar plate exit header across the entire stack height by repeated 2C-PIV measurements on densely spaced adjacent light sheet planes. An overview of the experimental setup and the data evaluation is given. (orig.)

  15. The use of additive manufacture for metallic bipolar plates in polymer electrolyte fuel cell stacks

    OpenAIRE

    Dawson, Richard; Patel, Anant; Rennie, Allan; White, Simon

    2014-01-01

    The bipolar plate is of critical importance to the efficient and long lasting operation of a polymer electrolyte fuel cell (PEMFC) stack. With advances in membrane electrode assembly (MEA) design greater attention has been focused on the bipolar plate and the important role it plays in performance and durability. Although carbon composite plates are a likely candidate for the mass introduction of fuel cells, it is metallic plates made from thin strip materials (typically 0.2 mm thick stainles...

  16. On-line and real-time diagnosis method for proton membrane fuel cell (PEMFC) stack by the superposition principle

    Science.gov (United States)

    Lee, Young-Hyun; Kim, Jonghyeon; Yoo, Seungyeol

    2016-09-01

    The critical cell voltage drop in a stack can be followed by stack defect. A method of detecting defective cell is the cell voltage monitoring. The other methods are based on the nonlinear frequency response. In this paper, the superposition principle for the diagnosis of PEMFC stack is introduced. If critical cell voltage drops exist, the stack behaves as a nonlinear system. This nonlinearity can explicitly appear in the ohmic overpotential region of a voltage-current curve. To detect the critical cell voltage drop, a stack is excited by two input direct test-currents which have smaller amplitude than an operating stack current and have an equal distance value from the operating current. If the difference between one voltage excited by a test current and the voltage excited by a load current is not equal to the difference between the other voltage response and the voltage excited by the load current, the stack system acts as a nonlinear system. This means that there is a critical cell voltage drop. The deviation from the value zero of the difference reflects the grade of the system nonlinearity. A simulation model for the stack diagnosis is developed based on the SPP, and experimentally validated.

  17. Linear identification and model adjustment of a PEM fuel cell stack

    Energy Technology Data Exchange (ETDEWEB)

    Kunusch, C.; Puleston, P.F.; More, J.J. [LEICI, Departamento de Electrotecnia, Universidad Nacional de La Plata, calle 1 esq. 47 s/n, 1900 La Plata (Argentina); Consejo de Investigaciones Cientificas y Tecnicas (CONICET) (Argentina); Husar, A. [Institut de Robotica i Informatica Industrial (CSIC-UPC), c/ Llorens i Artigas 4-6, 08028 Barcelona (Spain); Mayosky, M.A. [LEICI, Departamento de Electrotecnia, Universidad Nacional de La Plata, calle 1 esq. 47 s/n, 1900 La Plata (Argentina); Comision de Investigaciones Cientificas (CIC), Provincia de Buenos Aires (Argentina)

    2008-07-15

    In the context of fuel cell stack control a mayor challenge is modeling the interdependence of various complex subsystem dynamics. In many cases, the states interaction is usually modeled through several look-up tables, decision blocks and piecewise continuous functions. Many internal variables are inaccessible for measurement and cannot be used in control algorithms. To make significant contributions in this area, it is necessary to develop reliable models for control and design purposes. In this paper, a linear model based on experimental identification of a 7-cell stack was developed. The procedure followed to obtain a linear model of the system consisted in performing spectroscopy tests of four different single-input single-output subsystems. The considered inputs for the tests were the stack current and the cathode oxygen flow rate, while the measured outputs were the stack voltage and the cathode total pressure. The resulting model can be used either for model-based control design or for on-line analysis and errors detection. (author)

  18. Flow network analysis in PEM fuel cell stacks incorporating minor losses. Paper no. IGEC-1-062

    International Nuclear Information System (INIS)

    The performance of a polymer electrolyte membrane (PEM) fuel cell stack consisting 51 cells has been analyzed using a flow network model incorporating the minor losses. The distributions of pressure, molar flow rate and concentration for the fuel and oxidant streams in the stack are determined. The distributions are used in the single cell model developed previously to evaluate the stack voltage and the cell-to-cell voltage distributions. Analysis has been carried out for a variety of flow configurations and bipolar plate designs. It was found that the minor losses increase the stack operating pressure and the power requirement for oxidant supply and change the cell-to-cell voltage variations in the stack. A symmetric double inlet-single outlet topology provides optimal stack performance with reasonably low compressor power requirement for the reactant flow and minimum cell-to-cell voltage variations. The stack performance is considerably affected by the size and the number of flow channels on bipolar plate. (author)

  19. 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.

  20. Validation of a novel method for detecting and stabilizing malfunctioning areas in fuel cell stacks

    Science.gov (United States)

    Müller, Martin; Hirschfeld, Julian; Lambertz, Rita; Schulze Lohoff, Andreas; Lustfeld, Hans; Pfeifer, Heinz; Reißel, Martin

    2014-12-01

    In this paper a setup for detecting malfunctioning areas of MEAs in fuel cell stacks is described. Malfunctioning areas generate electric cross currents inside bipolar plates. To exploit this we suggest bipolar plates consisting not of two but of three layers. The third one is a highly conducting layer and segmented such that the cross currents move along the segments to the surface of the stack where they can be measured by an inductive sensor. With this information a realistic model can be used to detect the malfunctioning area. Furthermore the third layer will prevent any current inhomogeneity of a malfunctioning cell to spread to neighbouring cells in the stack. In this work the results of measurements in a realistic cell setup will be compared with the results obtained in simulation studies with the same configuration. The basis for the comparison is the reliable characterisation of the electrical properties of the cell components and the implication of these results into the simulation model. The experimental studies will also show the limits in the maximum number of segments, which can be used for a reliable detection of cross currents.

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

    International Nuclear Information System (INIS)

    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

  2. Assessment of Compliance with PEFC Forest Certification Indicators with Remote Sensing

    OpenAIRE

    Eugene Lopatin; Maxim Trishkin; Olga Gavrilova

    2016-01-01

    The majority of Finnish forests (95%) are certified by the Programme for the Endorsement of Forest Certification (PEFC). It is a worldwide leading forest certification scheme. The aim of this study is to analyze the Finnish National Standard of PEFC certification and identify the indicators that can be reliably estimated with remote sensing (RS) techniques. The retrieved data are further verified with a chosen geographical information system (GIS) application. The rapid increase in certified ...

  3. Elucidation of hydrogen cross leak mechanism in PEFC by magnetic resonance imaging and in-line direct gas mass spectroscopy

    International Nuclear Information System (INIS)

    Hydrogen (H2) permeability of polymer electrolyte membranes (PEMs) is of great importance since cross-leak H2 has an effect on degradation of membranes and/or catalyst layers in polymer electrolyte fuel cells (PEFCs). In this study, H2 cross-leak measurement by direct gas mass spectroscopy (DGMS) and water content measurement using magnetic resonance imaging (MRI) technique were carried out to investigate H2 cross-leak mechanism in a polymer electrolyte membrane (PEM). High H2 permeability was detected at elevated temperature, higher humidity and large H2 partial pressure in the anode. H2 permeability through the membrane was strongly affected by the volume fraction of the hydrophilic ion-cluster domain as MRI revealed the membrane was hydrated at higher humidity. Increase of cell temperature possibly accelerates H2 diffusion through the ion-cluster domain and the hydrophobic domain. Observed H2 permeability depending on H2 partial pressure in the anode shows H2 cross-leak process was closely related to both dissolution and diffusion of hydrogen in the membrane. Based on the experimental results, a comprehensive H2 cross-leak mechanism in PEFC was proposed. (author)

  4. Study of the distribution of air flow in a proton exchange membrane fuel cell stack

    Energy Technology Data Exchange (ETDEWEB)

    Mustata, Radu; Valino, Luis; Barreras, Felix; Gil, Maria Isabel; Lozano, Antonio [LITEC, CSIC - Univ. Zaragoza - DGA Maria de Luna 10, 50018, Zaragoza (Spain)

    2009-07-01

    The flow of air to feed oxygen to the cathode of each plate in a proton exchange membrane fuel cell (PEMFC) is studied for a 300 W stack in a realistic 3D configuration. Two configurations for gas income are solved, a ''U'' shape, where both the inlet and outlet of the air collectors are at the same end plate, and a ''Z'' shape, where inlet and outlet are at opposite sides of the stack. Under a simplified assumption for the flow of oxygen entering the gas diffusion layer of each cell, detailed mass flow and pressure distributions are shown, including the possibility of a turbulent flow inside the main collectors. (author)

  5. Corrosion-resistant, electrically-conductive plate for use in a fuel cell stack

    Science.gov (United States)

    Carter, J. David; Mawdsley, Jennifer R.; Niyogi, Suhas; Wang, Xiaoping; Cruse, Terry; Santos, Lilia

    2010-04-20

    A corrosion resistant, electrically-conductive, durable plate at least partially coated with an anchor coating and a corrosion resistant coating. The corrosion resistant coating made of at least a polymer and a plurality of corrosion resistant particles each having a surface area between about 1-20 m.sup.2/g and a diameter less than about 10 microns. Preferably, the plate is used as a bipolar plate in a proton exchange membrane (PEMFC) fuel cell stack.

  6. Development and characterization of a novel air-breathing micro direct methanol fuel cell stack for portable applications

    International Nuclear Information System (INIS)

    An air-breathing 10-cell micro direct methanol fuel cell (µDMFC) stack with four anode feeding patterns is designed, fabricated and tested. For a better understanding of the operational characteristics of both the single cell and the stack, a two-dimensional numerical model is established and calculated. Employing micro-stamping technology, the current collectors of each single cell are microfabricated on the stainless steel plate with a thickness of 300 µm. The single µDMFC is first tested under various operating parameters. On the basis of the simulation and experimental observation of the single cell performance, the µDMFC stack performance is thoroughly analyzed with different anode feeding patterns. The results indicate that the µDMFC stack with pattern B can ensure the uniform performance of each single cell and generate the highest power output. With pattern B, further experiments are carried out to investigate the influence of the anode flow rate on the stack performance. As a result, the µDMFC stack achieves the best performance with the maximum power density of about 24.75 mW cm−2 at 5.0 ml min−1. Finally, the stack is successfully applied to two electronic devices of different rated power

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

    OpenAIRE

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

    2008-01-01

    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 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. In designing and contro...

  8. Efficiency Enhancement of InGaN-Based Solar Cells via Stacking Layers of Light-Harvesting Nanospheres.

    Science.gov (United States)

    Al-Amri, Amal M; Fu, Po-Han; Lai, Kun-Yu; Wang, Hsin-Ping; Li, Lain-Jong; He, Jr-Hau

    2016-01-01

    An effective light-harvesting scheme for InGaN-based multiple quantum well solar cells is demonstrated using stacking layers of polystyrene nanospheres. Light-harvesting efficiencies on the solar cells covered with varied stacks of nanospheres are evaluated through numerical and experimental methods. The numerical simulation reveals that nanospheres with 3 stacking layers exhibit the most improved optical absorption and haze ratio as compared to those obtained by monolayer nanospheres. The experimental demonstration, agreeing with the theoretical analyses, shows that the application of 3-layer nanospheres improves the conversion efficiency of the solar cell by ~31%. PMID:27339612

  9. Efficiency Enhancement of InGaN-Based Solar Cells via Stacking Layers of Light-Harvesting Nanospheres

    Science.gov (United States)

    Al-Amri, Amal M.; Fu, Po-Han; Lai, Kun-Yu; Wang, Hsin-Ping; Li, Lain-Jong; He, Jr-Hau

    2016-01-01

    An effective light-harvesting scheme for InGaN-based multiple quantum well solar cells is demonstrated using stacking layers of polystyrene nanospheres. Light-harvesting efficiencies on the solar cells covered with varied stacks of nanospheres are evaluated through numerical and experimental methods. The numerical simulation reveals that nanospheres with 3 stacking layers exhibit the most improved optical absorption and haze ratio as compared to those obtained by monolayer nanospheres. The experimental demonstration, agreeing with the theoretical analyses, shows that the application of 3-layer nanospheres improves the conversion efficiency of the solar cell by ~31%. PMID:27339612

  10. Efficiency Enhancement of InGaN-Based Solar Cells via Stacking Layers of Light-Harvesting Nanospheres

    KAUST Repository

    Al-Amri, Amal M.

    2016-06-24

    An effective light-harvesting scheme for InGaN-based multiple quantum well solar cells is demonstrated using stacking layers of polystyrene nanospheres. Light-harvesting efficiencies on the solar cells covered with varied stacks of nanospheres are evaluated through numerical and experimental methods. The numerical simulation reveals that nanospheres with 3 stacking layers exhibit the most improved optical absorption and haze ratio as compared to those obtained by monolayer nanospheres. The experimental demonstration, agreeing with the theoretical analyses, shows that the application of 3-layer nanospheres improves the conversion efficiency of the solar cell by ~31%.

  11. LONG-TERM PERFORMANCE OF SOLID OXIDE STACKS WITH ELECTRODE-SUPPORTED CELLS OPERATING IN THE STEAM ELECTROLYSIS MODE

    Energy Technology Data Exchange (ETDEWEB)

    J. E. O' Brien; R. C. O' Brien; X. Zhang; G. Tao; B. J. Butler

    2011-11-01

    Performance characterization and durability testing have been completed on two five-cell high-temperature electrolysis stacks constructed with advanced cell and stack technologies. The solid oxide cells incorporate a negative-electrode-supported multi-layer design with nickel-zirconia cermet negative electrodes, thin-film yttria-stabilized zirconia electrolytes, and multi-layer lanthanum ferrite-based positive electrodes. The per-cell active area is 100 cm2. The stack is internally manifolded with compliant mica-glass seals. Treated metallic interconnects with integral flow channels separate the cells. Stack compression is accomplished by means of a custom spring-loaded test fixture. Initial stack performance characterization was determined through a series of DC potential sweeps in both fuel cell and electrolysis modes of operation. Results of these sweeps indicated very good initial performance, with area-specific resistance values less than 0.5 ?.cm2. Long-term durability testing was performed with A test duration of 1000 hours. Overall performance degradation was less than 10% over the 1000-hour period. Final stack performance characterization was again determined by a series of DC potential sweeps at the same flow conditions as the initial sweeps in both electrolysis and fuel cell modes of operation. A final sweep in the fuel cell mode indicated a power density of 0.356 W/cm2, with average per-cell voltage of 0.71 V at a current of 50 A.

  12. Engineering aspects and hardware verification of a volume producable solid oxide fuel cell stack design for diesel auxiliary power units

    Science.gov (United States)

    Stelter, Michael; Reinert, Andreas; Mai, Björn Erik; Kuznecov, Mihail

    A solid oxide fuel cell (SOFC) stack module is presented that is designed for operation on diesel reformate in an auxiliary power unit (APU). The stack was designed using a top-down approach, based on a specification of an APU system that is installed on board of vehicles. The stack design is planar, modular and scalable with stamped sheet metal interconnectors. It features thin membrane electrode assemblies (MEAs), such as electrolyte supported cells (ESC) and operates at elevated temperatures around 800 °C. The stack has a low pressure drop in both the anode and the cathode to facilitate a simple system layout. An overview of the technical targets met so far is given. A stack power density of 0.2 kW l -1 has been demonstrated in a fully integrated, thermally self-sustaining APU prototype running with diesel and without an external water supply.

  13. Accelerated testing of solid oxide fuel cell stacks for micro combined heat and power application

    Science.gov (United States)

    Hagen, Anke; Høgh, Jens Valdemar Thorvald; Barfod, Rasmus

    2015-12-01

    State-of-the-art (SoA) solid oxide fuel cell (SOFC) stacks are tested using profiles relevant for use in micro combined heat and power (CHP) units. Such applications are characterised by dynamic load profiles. In order to shorten the needed testing time and to investigate potential acceleration of degradation, the profiles are executed faster than required for real applications. Operation with fast load cycling, both using hydrogen and methane/steam as fuels, does not accelerate degradation compared to constant operation, which demonstrates the maturity of SoA stacks and enables transferring knowledge from testing at constant conditions to dynamic operation. 7.5 times more cycles than required for 80,000 h lifetime as micro CHP are achieved on one-cell-stack level. The results also suggest that degradation mechanisms that proceed on a longer time-scale, such as creep, might have a more dominating effect for long life-times than regular short time changes of operation. In order to address lifetime testing it is suggested to build a testing program consisting of defined modules that represent different application profiles, such as one module at constant conditions, followed by modules at one set of dynamic conditions etc.

  14. Cell and stack design alternatives. Second quarterly report, November 1, 1978-January 31, 1979

    Energy Technology Data Exchange (ETDEWEB)

    1979-02-14

    Progress on a program to develop commercially viable phosphoric acid fuel cell driven on-site integration energy systems is presented. A mass and energy balance was completed for one operating point of a selected power generation sub-system with a power output of 119 kW. Potentially, 87% of the LHV of the input fuel is available as bus bar electricity or useful heat. A 2 kW stack of conventional design and a 0.5 kW DIGAS cooled stack have been constructed and are on test at ERC. Renovation of a space for the Westinghouse stack test facility is underway and procurement of equipment has been initiated. The coupled cell temperature - current density analysis has been modified to include the effects of turbulent coolant flow and extended to permit analysis of up to 10 process plates between cooling plates. The REFORM computer program was verified by comparison with data received from the government project manager. A method for predicting carbon deposition was developed and compared with data from the literature.

  15. Cell and stack design alternatives. Second quarterly report, November 1, 1978-January 31, 1979

    Energy Technology Data Exchange (ETDEWEB)

    Hoover, D.Q.

    1979-02-14

    Work on the design of an on-site fuel cell total energy system for an apartment building is described. A mass and energy balance was completed for one operating point of a selected power generation sub-system with a power output of 119 kW. Potentially, 87 percent of the LHV of the input fuel is available as bus bar electricity or useful heat. A 2 kW stack of conventional design and a 0.5 kW DIGAS cooled stack have been constructed and are on test at ERC. Renovation of a space for the Westinghouse stack test facility is underway and procurement of equipment has been initiated. The coupled cell temperature - current density analysis has been modified to include the effects of turbulent coolant flow and extended to permit analysis of up to 10 process plates between cooling plates. The REFORM computer program was verified by comparison with data received from the government project manager. A method for predicting carbon deposition was developed and compared with data from the literature.

  16. Enhanced water desalination efficiency in an air-cathode stacked microbial electrodeionization cell (SMEDIC)

    KAUST Repository

    Chehab, Noura A.

    2014-11-01

    A microbial desalination cell was developed that contained a stack of membranes packed with ion exchange resins between the membranes to reduce ohmic resistances and improve performance. This new configuration, called a stacked microbial electro-deionization cell (SMEDIC), was compared to a control reactor (SMDC) lacking the resins. The SMEDIC+S reactors contained both a spacer and 1.4±0.2. mL of ion exchange resin (IER) per membrane channel, while the spacer was omitted in the SMEDIC-S reactors and so a larger volume of resin (2.4±0.2. mL) was used. The overall extent of desalination using the SMEDIC with a moderate (brackish water) salt concentration (13. g/L) was 90-94%, compared to only 60% for the SMDC after 7 fed-batch cycles of the anode. At a higher (seawater) salt concentration of 35. g/L, the extent of desalination reached 61-72% (after 10 cycles) for the SMEDIC, compared to 43% for the SMDC. The improved performance was shown to be due to the reduction in ohmic resistances, which were 130. Ω (SMEDIC-S) and 180. Ω (SMEDIC+S) at the high salt concentration, compared to 210. Ω without resin (SMDC). These results show that IERs can improve performance of stacked membranes for both moderate and high initial salt concentrations. © 2014 Elsevier B.V.

  17. Influence of Ring Oxidation-Induced Stack Faults on Efficiency in Silicon Solar Cells

    Institute of Scientific and Technical Information of China (English)

    ZHOU Chun-Lan; WANG Wen-Jing; LI Hai-Ling; ZHAO Lei; DIAO Hong-Wei; LI Xu-Dong

    2008-01-01

    @@ We observe a strong correlation between the ring oxidation-induced stack faults (OISF) formed in the course of phosphor diffusion and the efficiency of Czochralski-grown silicon solar cells. The main reason for ring-OISF formation and growth in substrate is the silicon oxidation and phosphorus diffusion process induced silicon self-interstitial point defect during POCl3 diffusion. The decreasing of minority carrier diffusion length in crystal silicon solar cell induced by ring-OISF defects is identified to be one of the major causes of efficiency loss.

  18. Novel composite Zr/PBI-O-PhT membranes for HT-PEFC applications

    Directory of Open Access Journals (Sweden)

    Mikhail S. Kondratenko

    2013-08-01

    Full Text Available Novel composite membranes for high temperature polymer-electrolyte fuel cells (HT-PEFC based on a poly[oxy-3,3-bis(4′-benzimidazol-2″-ylphenylphtalide-5″(6″-diyl] (PBI-O-PhT polymer with small amounts of added Zr were prepared. It was shown in a model reaction between zirconium acetylacetonate (Zr(acac4 and benzimidazole (BI that Zr-atoms are capable to form chemical bonds with BI. Thus, Zr may be used as a crosslinking agent for PBI membranes. The obtained Zr/PBI-O-PhT composite membranes were examined by means of SAXS, thermomechanical analysis (TMA, and were tested in operating fuel cells by means of stationary voltammetry and impedance spectroscopy. The new membranes showed excellent stability in a 2000-hour fuel cell (FC durability test. The modification of the PBI-O-PhT films with Zr facilitated an increase of the phosphoric acid (PA uptake by the membranes, which resulted in an up to 2.5 times increased proton conductivity. The existence of an optimal amount of Zr content in the modified PBI-O-PhT film was shown. Larger amounts of Zr lead to a lower PA doping level and a reduced conductivity due to an excessively high degree of crosslinking.

  19. Nonlinear modelling of polymer electrolyte membrane fuel cell stack using nonlinear cancellation technique

    International Nuclear Information System (INIS)

    Fuel cells are promising new energy conversion devices that are friendly to the environment. A set of control systems are required in order to operate a fuel cell based power plant system optimally. For the purpose of control system design, an accurate fuel cell stack model in describing the dynamics of the real system is needed. Currently, linear model are widely used for fuel cell stack control purposes, but it has limitations in narrow operation range. While nonlinear models lead to nonlinear control implemnetation whos more complex and hard computing. In this research, nonlinear cancellation technique will be used to transform a nonlinear model into a linear form while maintaining the nonlinear characteristics. The transformation is done by replacing the input of the original model by a certain virtual input that has nonlinear relationship with the original input. Then the equality of the two models is tested by running a series of simulation. Input variation of H2, O2 and H2O as well as disturbance input I (current load) are studied by simulation. The error of comparison between the proposed model and the original nonlinear model are less than 1 %. Thus we can conclude that nonlinear cancellation technique can be used to represent fuel cell nonlinear model in a simple linear form while maintaining the nonlinear characteristics and therefore retain the wide operation range

  20. Optimization of membrane stack configuration in enlarged microbial desalination cells for efficient water desalination

    Science.gov (United States)

    Chen, Xi; Sun, Haotian; Liang, Peng; Zhang, Xiaoyuan; Huang, Xia

    2016-08-01

    Microbial desalination cells are considered a low-energy-consumption, clean technology to simultaneously purify wastewater and desalinate saline water by utilizing the in situ energy source contained in wastewater. To enhance desalination performance and achieve an optimal membrane stack configuration, an enlarged stacked microbial desalination cell (SMDC) has been developed and tested with 6-14 desalination cells. The cross-membrane area of the enlarged SMDC is 100 cm2. The anode and cathode volumes are both 200 mL. To reduce internal resistance, the width of desalination cells is kept as <0.5 mm. The optimal configuration with 10 desalination cells achieves the highest total desalination rate (TDR) of 423 mg/h and the highest charge transfer efficiency (CTE) of 836% when treating the 20 g/L NaCl solution. During this process, the junction potential across membranes increases from 0 to 374 mV, and occupies up to 74% of the total potential loss inside the SMDC. This shows that the SMDC used in this work achieves the highest TDR and CTE among the reported studies, and the junction potential should be effectively controlled to achieve the desired desalination performance in future practical applications.

  1. Optimization of membrane stack configuration in enlarged microbial desalination cells for efficient water desalination

    Science.gov (United States)

    Chen, Xi; Sun, Haotian; Liang, Peng; Zhang, Xiaoyuan; Huang, Xia

    2016-08-01

    Microbial desalination cells are considered a low-energy-consumption, clean technology to simultaneously purify wastewater and desalinate saline water by utilizing the in situ energy source contained in wastewater. To enhance desalination performance and achieve an optimal membrane stack configuration, an enlarged stacked microbial desalination cell (SMDC) has been developed and tested with 6-14 desalination cells. The cross-membrane area of the enlarged SMDC is 100 cm2. The anode and cathode volumes are both 200 mL. To reduce internal resistance, the width of desalination cells is kept as cells achieves the highest total desalination rate (TDR) of 423 mg/h and the highest charge transfer efficiency (CTE) of 836% when treating the 20 g/L NaCl solution. During this process, the junction potential across membranes increases from 0 to 374 mV, and occupies up to 74% of the total potential loss inside the SMDC. This shows that the SMDC used in this work achieves the highest TDR and CTE among the reported studies, and the junction potential should be effectively controlled to achieve the desired desalination performance in future practical applications.

  2. Documentation of Short Stack and Button Cell Experiments Performed at INL and Ceramatec during FY07

    Energy Technology Data Exchange (ETDEWEB)

    J. E. O' Brien; C. M. Stoots; J. J. Hartvigsen; J. S. Herring

    2007-09-01

    This report provides documentation of experimental research activities performed at the Idaho National Laboratory and at Ceramatec, Inc. during FY07 under the DOE Nuclear Hydrogen Initiative, High Temperature Electrolysis Program. The activities discussed in this report include tests on single (button) cells, short planar stacks and tubular cells. The objectives of these small-scale tests are to evaluate advanced electrode, electrolyte, and interconnect materials, alternate modes of operation (e.g., coelectrolysis), and alternate cell geometries over a broad range of operating conditions, with the aim of identifying the most promising material et, cell and stack geometry, and operating conditions for the high-temperature electrolysis application. Cell performance is characterized in erms of initial area-specific resistance and long-term stability in the electrolysis mode. Some of the tests were run in the coelectrolysis mode. Research into coelectrolysis was funded by Laboratory Directed Research and Development (LDRD). Coelectrolysis simultaneously converts steam to hydrogen and carbon dioxide to carbon monoxide. This process is complicated by the reverse shift reaction. An equilibrium model was developed to predict outlet compositions of steam, hydrogen, carbon dioxide, and carbon monoxide resulting from coelectrolysis. Predicted ompositions were compared to measurements obtained with a precision micro-channel gas chromatograph.

  3. Nonlinear modelling of polymer electrolyte membrane fuel cell stack using nonlinear cancellation technique

    Energy Technology Data Exchange (ETDEWEB)

    Barus, R. P. P., E-mail: rismawan.ppb@gmail.com [Engineering Physics, Faculty of Industrial Technology, Institut Teknologi Bandung, Jalan Ganesa 10 Bandung and Centre for Material and Technical Product, Jalan Sangkuriang No. 14 Bandung (Indonesia); Tjokronegoro, H. A.; Leksono, E. [Engineering Physics, Faculty of Industrial Technology, Institut Teknologi Bandung, Jalan Ganesa 10 Bandung (Indonesia); Ismunandar [Chemistry Study, Faculty of Mathematics and Science, Institut Teknologi Bandung, Jalan Ganesa 10 Bandung (Indonesia)

    2014-09-25

    Fuel cells are promising new energy conversion devices that are friendly to the environment. A set of control systems are required in order to operate a fuel cell based power plant system optimally. For the purpose of control system design, an accurate fuel cell stack model in describing the dynamics of the real system is needed. Currently, linear model are widely used for fuel cell stack control purposes, but it has limitations in narrow operation range. While nonlinear models lead to nonlinear control implemnetation whos more complex and hard computing. In this research, nonlinear cancellation technique will be used to transform a nonlinear model into a linear form while maintaining the nonlinear characteristics. The transformation is done by replacing the input of the original model by a certain virtual input that has nonlinear relationship with the original input. Then the equality of the two models is tested by running a series of simulation. Input variation of H2, O2 and H2O as well as disturbance input I (current load) are studied by simulation. The error of comparison between the proposed model and the original nonlinear model are less than 1 %. Thus we can conclude that nonlinear cancellation technique can be used to represent fuel cell nonlinear model in a simple linear form while maintaining the nonlinear characteristics and therefore retain the wide operation range.

  4. 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 ...... 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.......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...

  5. A hybrid microbial fuel cell stack based on single and double chamber microbial fuel cells for self-sustaining pH control

    Science.gov (United States)

    Yang, Wei; Li, Jun; Ye, Dingding; Zhang, Liang; Zhu, Xun; Liao, Qiang

    2016-02-01

    Proton accumulation in the anode chamber is the major problem that affects the operational stability and electricity generation performance of double chamber microbial fuel cells (MFCs). In this study, a hybrid microbial fuel cell stack (DS-DS stack) based on single (SCMFCs) and double chamber MFCs (DCMFCs) is proposed for self-sustaining pH control in the MFC stack. It is found that the aerobic microbial oxidation of acetate by the biofilm that is attached to the air cathode of SCMFCs is responsible for the self-sustaining removal of accumulated H+ in the effluent of DCMFCs. Compared with the stack that solely consists of SCMFCs (SS-SS stack) or DCMFCs (DD-DD stack), the hybrid stack exhibits the highest electricity output performance and the most effective conversion of acetate into electricity at high power levels. Furthermore, the hybrid stack demonstrates the operation time of 15.7 ± 1.1 h when the operating voltage is above 0.8 V. This value is much higher than that of the DD-DD (8.5 ± 2.4 h) and SS-SS (8.1 ± 1.4 h) stacks, which suggests that the hybrid stack had a good operational stability.

  6. Cell and stack design alternatives. First quarterly report, August 1, 1978-October 31, 1978

    Energy Technology Data Exchange (ETDEWEB)

    Hoover, D.Q.

    1979-01-01

    An apartment house in Albany, New York with HUD minimum insulation was selected as the application to be used in evaluating various system configurations of on-site fuel cell total energy systems. Methods for calculating the static and dynamic thermal loads for a simulated season were developed. Computer models of some major subsystems are now being developed. Finite element models of the electrochemistry, thermodynamics and heat transfer relationships for fuel cells were developed and have been used to calculate current density and temperature distributions for sets of large cells and cooling plates. The results obtained led to several innovative ideas for advanced stack designs. A single lump model of a fuel cell stack was developed for use in the systems study. The available information on methane conditioning was collected and reviewed and a plan for attaining the missing design data has been developed. Simple models of reformer and water-gas shift reactors were developed for use in the systems study. The lines of communication among technical tasks were established, required documentation of plans and progress was prepared and delivered and the monthly review meetings were held as planned.

  7. On modifying the condition for the local current density decoupling in fuel cell stacks for moderate perturbations

    International Nuclear Information System (INIS)

    Two adjacent cells in a fuel cell stack are said to be decoupled when they do not affect each other's local current density distribution. This paper proposes a condition for local current density decoupling between two adjacent cells with arbitrary degree of perturbations. The proposed condition in the form of a bound comprising some measure of the perturbation on a dimensionless number comprising the design, operating conditions, and material properties of the bipolar plate is correlated with the current redistribution between cells and verified with a non-isothermal proton exchange membrane fuel cell stack model

  8. Monopolar fuel cell stack coupled together without use of top or bottom cover plates or tie rods

    Science.gov (United States)

    Narayanan, Sekharipuram R. (Inventor); Valdez, Thomas I. (Inventor)

    2009-01-01

    A monopolar fuel cell stack comprises a plurality of sealed unit cells coupled together. Each unit cell comprises two outer cathodes adjacent to corresponding membrane electrode assemblies and a center anode plate. An inlet and outlet manifold are coupled to the anode plate and communicate with a channel therein. Fuel flows from the inlet manifold through the channel in contact with the anode plate and flows out through the outlet manifold. The inlet and outlet manifolds are arranged to couple to the inlet and outlet manifolds respectively of an adjacent one of the plurality of unit cells to permit fuel flow in common into all of the inlet manifolds of the plurality of the unit cells when coupled together in a stack and out of all of the outlet manifolds of the plurality of unit cells when coupled together in a stack.

  9. Fuel cell; Nenryo denchi

    Energy Technology Data Exchange (ETDEWEB)

    Nakayama, T. [New Energy and Industrial Technology Development Organization, Tokyo (Japan)

    1999-07-20

    More than 100 sets of phosphoric acid fuel cells (PAFC) have been installed by now, and accumulated operation performance exceeding 40 thousand hours, which is regarded as a development target, has been achieved. Further, there are also PAFCs that have achieved continuous operation performance exceeding 9,000 hours, thus being most approachable to practical use. On the other hand, developments of the solid oxide fuel cells (SOFC) and the molten carbonate fuel cells (MCFC), which operate at high temperatures, have high power generation efficiencies due to the capability of operating associatively with gas turbines or vapor turbines, and may use coal gasified gases as fuels, are carried out for an aim of realizing the practical use at the begging of the 21st century. Further, in recent years, researches and developments of the polymer electrolyte fuel cells (PEFC) have been accelerated mainly in vehicle business for the purpose of using PEFC as power sources for movable bodies, and researches and development for accelerative development of cell stacks and power generation systems are executed. In this paper, situations of the researches and developments in respect to the above-mentioned four kinds of fuel cells are summarily introduced. (NEDO)

  10. Experiment and numerical simulation on the performance of a kw-scale molten carbonate fuel cell stack

    Directory of Open Access Journals (Sweden)

    L. J. Yu

    2007-12-01

    Full Text Available A high-temperature molten carbonate fuel cell stack was studied experimentally and computationally. Experimental data for fuel cell temperature was obtained when the stack was running under given operational conditions. A 3-D CFD numerical model was set up and used to simulate the central fuel cell in the stack. It includes the mass, momentum and energy conservation equations, the ideal gas law and an empirical equation for cell voltage. The model was used to simulate the transient behavior of the fuel cell under the same operational conditions as those of the experiment. Simulation results show that the transient temperature and current and power densities reach their maximal values at the channel outlet. A comparison of the modeling results and the experimental data shows the good agreement.

  11. Experiences from design and testing of a small PEM fuel cell stack

    International Nuclear Information System (INIS)

    'Full text:' Introduction The Proton Exchange Membrane Fuel Cell (PEMFC) technology is considered the most promising candidate for mobile applications, due to its high power density, short start-up times and immediate response to changes in power demand. PEMFC systems tend, however, to become rather complex in order to provide for optimum water and thermal management, and facilitate stable operation. Auxiliary components add to cost and volume, and may reduce reliability. Pressurized operation may increase system power density, but to the sacrifice of efficiency. The atmospheric systems are inferior to pressurized systems with respect to water self-sufficiency and usually demand voluminous water condenser systems. At high power densities the amount of waste heat becomes considerable, and for larger systems liquid cooling is usually inevitable. But even for smaller, air-cooled systems, thermal management is challenging because of the relatively small temperature difference between the fuel cell and the surroundings. Over more than a decade there has been a trend towards simpler PEMFC systems holding a minimum number of auxiliary components, operating at atmospheric pressure and utilizing various self-humidifying techniques. However, due to the complexity of PEMFC operation, the degree of simplification becomes a trade-off between system cost and volume, and controllability. Experimental In the present work a small 10 cell PEMFC stack for demonstrational purposes was designed, assembled and tested. Commercial MEAs (Gore) and GDLs (E-TEK) were used. Thermocouples were inserted into the cathode air channels. Based on a total of 300 temperature measurements a semi-3-dimensional temperature distribution in the stack was obtained. Cell performance was characterized by obtaining polarization curves for each cell and measuring the steady state temperature distribution at a current density of 0.10 A/cm2. Results and Discussion Stable performance was obtained at 0.10 A/cm2

  12. A new stack effluent monitoring system at the Risoe Hot Cell plant

    International Nuclear Information System (INIS)

    This report describes a new stack effluent monitoring system that has been installed at the Hot Cell facility. It is an integrating iodine/particulate system consisting of a γ-shielded flow house in which a continous air sample from the ventilation channel ia sucked through coal and glass filter papers. Activity is accumulated on the filter papers and a thin plastic scintillator detects the β-radiation from the trapped iodine or particulate activity. The stack effluent monitoring system has a two-step regulating function as applied to the ventilation system, first switching it to a recirculating mode, and finally to building-seal after given releases of 131I. The collection efficiency for iodine in form of elementary iodine (I2) and methyliodide (CH3I) has been determined experimentally. The unwanted response from a noble gas release has also been determined from experiments. The noble gas response was determined from puff releases of the nuclide 41Ar in the concrete cells. It is concluded that the iodine/particulate system is extremely sensitive and that it can easily detect iodine or particulate releases as low as a few MBq. A gamma monitor placed in connection with the iodine/particulate system detects Xe/Kr-releases as low as a few tens of MBq per second. (author)

  13. Mechanically Stacked Triple-junction GaInP / GaAs / Si Solar Cell Simulation

    Directory of Open Access Journals (Sweden)

    A.B. Gnilenko

    2014-01-01

    Full Text Available Mechanically stacked triple-junction GaInP / GaAs / Si solar cell is simulated by Silvaco TCAD computer software and compared to more conventional GaInP / GaAs / Ge mechanically stacked configuration. External quantum efficiency, I-V characteristics and basic I-V parameters are obtained to demonstrate the advantages of using the silicon active substrate as the bottom sub-cell instead of the germanium substrate based bottom sub-cell.

  14. Design of low power SRAM Cell with combined effect of sleep stack and variable body bias technique

    Directory of Open Access Journals (Sweden)

    Anjana R1 , Dr. Ajay kumar somkuwar

    2013-06-01

    Full Text Available Power consumption has become major concern in Very Large Scale Integration circuit and according to International technology roadmap of semiconductors (ITRS leakage power dissipation may dominate more of total power dissipation [1]. Sub threshold leakage power tends to increase as the leakage power increases. Variable sleepy biased keeper is compared with previously available technique like Sleep, Stack, Sleepy Stack, Sleepy Keeper, and Zigzag. In this paper, we design SRAM cell by combining two techniques, namely sleep stack and body biasing technique. The sleepy stack reduces leakage power, but loses its logic state during sleep mode. And body biasing technique reduces the static power consumption and maintains the logic state of the circuit. One main advantage of using variable sleepy biased keeper is, it can also use high Vth transistors

  15. Post-experimental analysis of a solid oxide fuel cell stack using hybrid seals

    Science.gov (United States)

    Thomann, O.; Rautanen, M.; Himanen, O.; Tallgren, J.; Kiviaho, J.

    2015-01-01

    A post-experimental analysis of a SOFC stack is presented. The stack was operated for 1800 h at 700 °C with air and hydrogen and contained hybrid glass-Thermiculite 866 seals. The goal of this work was to investigate the sealing microstructure and possible corrosion during mid-term operation. It was found that hybrid seals could effectively compensate for manufacturing tolerances of cells and other components due to the compliance of the glass layer. Additionally, different interfaces were investigated for corrosion. Corrosion was not observed at two-phase interfaces such as Crofer 22 APU/glass, glass/electrolyte and glass/Thermiculite 866. The three-phase interface between Crofer 22 APU/glass/hydrogen exhibited no corrosion. Some evidence of non-systematic corrosion was found at the Crofer 22 APU/glass/air interface. The possible reasons for the corrosion are discussed. Lastly, dual exposure to humid hydrogen and air of the 0.2 mm Crofer 22 APU interconnect had no detrimental effect on the corrosion compared to air exposure. Overall the hybrid seals used in combination with the thin interconnects were found to be a promising solution due to the low leak rate and limited material interactions.

  16. Optimization of membrane stack configuration for efficient hydrogen production in microbial reverse-electrodialysis electrolysis cells coupled with thermolytic solutions.

    Science.gov (United States)

    Luo, Xi; Nam, Joo-Youn; Zhang, Fang; Zhang, Xiaoyuan; Liang, Peng; Huang, Xia; Logan, Bruce E

    2013-07-01

    Waste heat can be captured as electrical energy to drive hydrogen evolution in microbial reverse-electrodialysis electrolysis cells (MRECs) by using thermolytic solutions such as ammonium bicarbonate. To determine the optimal membrane stack configuration for efficient hydrogen production in MRECs using ammonium bicarbonate solutions, different numbers of cell pairs and stack arrangements were tested. The optimum number of cell pairs was determined to be five based on MREC performance and a desire to minimize capital costs. The stack arrangement was altered by placing an extra low concentration chamber adjacent to anode chamber to reduce ammonia crossover. This additional chamber decreased ammonia nitrogen losses into anolyte by 60%, increased the coulombic efficiency to 83%, and improved the hydrogen yield to a maximum of 3.5 mol H2/mol acetate, with an overall energy efficiency of 27%. These results improve the MREC process, making it a more efficient method for renewable hydrogen gas production. PMID:23711946

  17. Optimization of membrane stack configuration for efficient hydrogen production in microbial reverse-electrodialysis electrolysis cells coupled with thermolytic solutions

    KAUST Repository

    Luo, Xi

    2013-07-01

    Waste heat can be captured as electrical energy to drive hydrogen evolution in microbial reverse-electrodialysis electrolysis cells (MRECs) by using thermolytic solutions such as ammonium bicarbonate. To determine the optimal membrane stack configuration for efficient hydrogen production in MRECs using ammonium bicarbonate solutions, different numbers of cell pairs and stack arrangements were tested. The optimum number of cell pairs was determined to be five based on MREC performance and a desire to minimize capital costs. The stack arrangement was altered by placing an extra low concentration chamber adjacent to anode chamber to reduce ammonia crossover. This additional chamber decreased ammonia nitrogen losses into anolyte by 60%, increased the coulombic efficiency to 83%, and improved the hydrogen yield to a maximum of 3.5mol H2/mol acetate, with an overall energy efficiency of 27%. These results improve the MREC process, making it a more efficient method for renewable hydrogen gas production. © 2013 Elsevier Ltd.

  18. Small stack performance of intermediate temperature-operating solid oxide fuel cells using stainless steel interconnects and anode-supported single cell

    Science.gov (United States)

    Bae, Joongmyeon; Lim, Sungkwang; Jee, Hyunjin; Kim, Jung Hyun; Yoo, Young-Sung; Lee, Taehee

    We are developing 1 kW class solid oxide fuel cell (SOFC) system for residential power generation (RPG) application supported by Korean Government. Anode-supported single cells with thin electrolyte layer of YSZ (yttria-stabilized zirconia) or ScSZ (scandia-stabilized zirconia) for intermediate temperature operation (650-750 °C), respectively, were fabricated and small stacks were built and evaluated. The LSCF/ScSZ/Ni-YSZ single cell showed performance of 543 mW cm -2 at 650 °C and 1680 mW cm -2 at 750 °C. The voltage of 15-cell stack based on 5 cm × 5 cm single cell (LSM/YSZ/Ni-YSZ) at 150 mW was 12.5 V in hydrogen as fuel of 120 sccm per cell at 750 °C and decreased to about 10.9 V at 500 h operation time. A 5-cell stack based on the LSCF/YSZ/FL/Ni-YSZ showed the maximum power density of 30 W, 25 W and 20 W at 750 °C, 700 °C and 650 °C, respectively. LSCF/ScSZ/Ni-YSZ-based stack showed better performance than LSCF/YSZ/Ni-YSZ stack from the experiment temperature range. I- V characteristics by using hydrogen gas and reformate gas of methane as fuel were investigated at 750 °C in LSCF/ScSZ/FL/Ni-YSZ-based 5-cell stack.

  19. Small stack performance of intermediate temperature-operating solid oxide fuel cells using stainless steel interconnects and anode-supported single cell

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Joongmyeon; Lim, Sungkwang; Kim, Jung Hyun [Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701 (Korea); Jee, Hyunjin [Agency for Defense Development (ADD), Jochiwongil 462, Yuseong, Daejeon (Korea); Yoo, Young-Sung; Lee, Taehee [Korea Electric Power Research Institute (KEPRI), Daejeon 305-380 (Korea)

    2007-10-11

    We are developing 1 kW class solid oxide fuel cell (SOFC) system for residential power generation (RPG) application supported by Korean Government. Anode-supported single cells with thin electrolyte layer of YSZ (yttria-stabilized zirconia) or ScSZ (scandia-stabilized zirconia) for intermediate temperature operation (650-750 C), respectively, were fabricated and small stacks were built and evaluated. The LSCF/ScSZ/Ni-YSZ single cell showed performance of 543 mW cm{sup -2} at 650 C and 1680 mW cm{sup -2} at 750 C. The voltage of 15-cell stack based on 5 cm x 5 cm single cell (LSM/YSZ/Ni-YSZ) at 150 mW was 12.5 V in hydrogen as fuel of 120 sccm per cell at 750 C and decreased to about 10.9 V at 500 h operation time. A 5-cell stack based on the LSCF/YSZ/FL/Ni-YSZ showed the maximum power density of 30 W, 25 W and 20 W at 750 C, 700 C and 650 C, respectively. LSCF/ScSZ/Ni-YSZ-based stack showed better performance than LSCF/YSZ/Ni-YSZ stack from the experiment temperature range. I-V characteristics by using hydrogen gas and reformate gas of methane as fuel were investigated at 750 C in LSCF/ScSZ/FL/Ni-YSZ-based 5-cell stack. (author)

  20. Modeling and simulation of high-temperature polymer electrolyte fuel cells; Modellierung und Simulation von Hochtemperatur-Polymerelektrolyt-Brennstoffzellen

    Energy Technology Data Exchange (ETDEWEB)

    Kvesic, Mirko

    2012-07-01

    Fuel cells are electrochemical energy converters that convert chemical energy of constantly fed reactants directly into electricity. The most commonly used fuel gas in this respect is hydrogen, which is either produced in pure form by electrolysis, for example, or as a hydrogen-rich gas mixture (reformate gas), produced by reforming diesel or kerosene e.g. However, a disadvantage of reformate gas is that it contains additional carbon monoxide (CO), which leads to catalyst poisoning in the fuel cell. Since higher operating temperatures also lead to a higher CO tolerance, the use of high-temperature Polymer-Electrolyte-Fuel-Cells (HT-PEFCs) is particularly suitable for reformate operation. The aim of the presented work is the modeling and CFD-simulation of HT-PEFC stacks with the intention of gaining a better understanding of multi-physical processes in the stack operation as well as the optimization and analysis of existing stack designs. The geometric modeling used is based on the Porous Volume Model, which significantly reduces the required number of computing elements. Furthermore, the electrochemical models for hydrogen / air and reformate / air operation, which were taking the CO poisoning effects into account, are developed in this work and implemented in the software ANSYS / Fluent. The resulting simulations indicated the optimal flow configuration for the stack operation in terms of the homogeneous current density distribution, which has a positive effect on the stack aging. Thus, the current densities showed a strong homogeneity regarding the stack configuration anode / cathode in counter-flow and anode / cooling in co-flow. The influence of cooling strategies was examined for the stack performance in a similar way. In the following, the local temperature distribution as well as temperature peaks within the stack could be predicted and validated with experimental measurements. Further on, the model scalability and thus the general validity of the developed

  1. Compact Design of 10 kW Proton Exchange Membrane Fuel Cell Stack Systems with Microcontroller Units

    Directory of Open Access Journals (Sweden)

    Hsiaokang Ma

    2014-04-01

    Full Text Available In this study, fuel, oxidant supply and cooling systems with microcontroller units (MCU are developed in a compact design to fit two 5 kW proton exchange membrane fuel cell (PEMFC stacks. At the initial stage, the testing facility of the system has a large volume (2.0 m × 2.0 m × 1.5 m with a longer pipeline and excessive control sensors for safe testing. After recognizing the performance and stability of stack, the system is redesigned to fit in a limited space (0.4 m × 0.5 m × 0.8 m. Furthermore, the stack performance is studied under different hydrogen recycling modes. Then, two similar 5 kW stacks are directly coupled with diodes to obtain a higher power output and safe operation. The result shows that the efficiency of the 5 kW stack is 43.46% with a purge period of 2 min with hydrogen recycling and that the hydrogen utilization rate µf is 66.31%. In addition, the maximum power output of the twin-coupled module (a power module with two stacks in electrical cascade/parallel arrangement is 9.52 kW.

  2. A double-fuzzy diagnostic methodology dedicated to online fault diagnosis of proton exchange membrane fuel cell stacks

    Science.gov (United States)

    Zheng, Zhixue; Péra, Marie-Cécile; Hissel, Daniel; Becherif, Mohamed; Agbli, Kréhi-Serge; Li, Yongdong

    2014-12-01

    To improve the performance and lifetime of the low temperature polymer electrolyte membrane fuel cell (PEMFC) stack, water management is an important issue. This paper aims at developing an online diagnostic methodology with the capability of discriminating different degrees of flooding/drying inside the fuel cell stack. Electrochemical impedance spectroscopy (EIS) is utilized as a basis tool and a double-fuzzy method consisting of fuzzy clustering and fuzzy logic is developed to mine diagnostic rules from the experimental data automatically. Through online experimental verification, a high interpretability and computational efficiency of the proposed methodology can be achieved.

  3. TEST RESULTS OF HIGH TEMPERATURE STEAM/CO2 CO-ELECTROLYSIS IN A 10-CELL STACK

    Energy Technology Data Exchange (ETDEWEB)

    James E. O' Brien; Joseph J. Hartvigsen

    2007-06-01

    High temperature coelectrolysis experiments with CO2 / H2O mixtures were performed in a 10-cell planar solid oxide stack. Results indicated that stack apparent ASR values were shown not to vary significantly between pure steam electrolysis and steam / CO2 coelectrolysis values. Product gas compositions measured via an online micro gas chromatograph (GC) showed excellent agreement to predictions obtained from a chemical equilibrium coelectrolysis model developed for this study. Experimentally determined open cell potentials and thermal neutral voltages for coelectrolysis compared favorably to predictions obtained from a chemical equilibrium coelectrolysis and energy balance model, also developed for this study.

  4. Solid oxide fuel cell anode degradation by the effect of hydrogen chloride in stack and single cell environments

    Science.gov (United States)

    Madi, Hossein; Lanzini, Andrea; Papurello, Davide; Diethelm, Stefan; Ludwig, Christian; Santarelli, Massimo; Van herle, Jan

    2016-09-01

    The poisoning effect by hydrogen chloride (HCl) on state-of-the-art Ni anode-supported solid oxide fuel cells (SOFCs) at 750 °C is evaluated in either hydrogen or syngas fuel. Experiments are performed on single cells and short stacks and HCl concentration in the fuel gas is increased from 1 ppm(v) up to 1000 ppm(v) at different current densities. Characterization methods such as cell voltage monitoring vs. time and electrochemical impedance response analysis (distribution of relaxation times (DRT), equivalent electrical circuit) are used to identify the prevailing degradation mechanism. Single cell experiments revealed that the poisoning is more severe when feeding with hydrogen than with syngas. Performance loss is attributed to the effects of HCl adsorption onto nickel surfaces, which lowered the catalyst activity. Interestingly, in syngas HCl does not affect stack performance even at concentrations up to 500 ppm(v), even when causing severe corrosion of the anode exhaust pipe. Furthermore, post-test analysis suggests that chlorine is present on the nickel particles in the form of adsorbed chlorine, rather than forming a secondary phase of nickel chlorine.

  5. High temperature operation of a solid polymer electrolyte fuel cell stack based on a new ionomer membrane

    Energy Technology Data Exchange (ETDEWEB)

    Arico, A.S.; Di Blasi, A.; Brunaccini, G.; Sergi, F.; Dispenza, G.; Andaloro, L.; Ferraro, M.; Antonucci, V. [CNR-ITAE, Messina (Italy); Asher, P.; Buche, S.; Fongalland, D.; Hards, G.A.; Sharman, J.D.B. [Johnson Matthey Fuel Cells Ltd, Blounts Court, Sonning Common, Reading, Berks (United Kingdom); Bayer, A.; Heinz, G.; Zandona, N. [SolviCore GmbH and Co KG, Hanau (Germany); Zuber, R. [Umicore AG and Co KG, Dept. RD-EP, Hanau (Germany); Gebert, M.; Corasaniti, M.; Ghielmi, A. [Solvay Solexis, Bollate (Italy)

    2010-12-15

    Polymer electrolyte fuel cell stacks assembled with Johnson Matthey Fuel Cells and SolviCore MEAs based on the Aquivion trademark E79-03S short-side chain (SSC), chemically stabilised perfluorosulphonic acid membrane developed by Solvay Solexis were investigated at CNR-ITAE in the EU Sixth Framework 'Autobrane' project. Electrochemical experiments in fuel cell short stacks were performed under practical automotive operating conditions at pressures of 1-1.5 bar abs. over a wide temperature range, up to 130 C, with varying levels of humidity (down to 18% R. H.). The stacks using large area (360 cm{sup 2}) MEAs showed elevated performance in the temperature range from ambient to 100 C (cell power density in the range of 600-700 mWcm{sup -2}) with a moderate decrease above 100 C. The performances and electrical efficiencies achieved at 110 C (cell power density of about 400 mWcm{sup -2} at an average cell voltage of about 0.5-0.6 V) are promising for automotive applications. Duty-cycle and steady-state galvanostatic experiments showed excellent stack stability for operation at high temperature. A performance comparison of Aquivion trademark and Nafion trademark -based MEAs under practical operating conditions showed a significantly better capability for the Solvay Solexis membrane to sustain high temperature operation. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Analysis and improvement of a scaled-up and stacked microbial fuel cell.

    Science.gov (United States)

    Dekker, Arjan; Ter Heijne, Annemiek; Saakes, Michel; Hamelers, Hubertus V M; Buisman, Cees J N

    2009-12-01

    Scaling up microbial fuel cells (MFCs) is inevitable when power outputs have to be obtained that can power electrical devices other than small sensors. This research has used a bipolar plate MFC stack of four cells with a total working volume of 20 L and a total membrane surface area of 2 m(2). The cathode limited MFC performance due to oxygen reduction rate and cell reversal. Furthermore, residence time distribution curves showed that bending membranes resulted in flow paths through which the catholyte could flow from inlet to outlet, while leaving the reactants unconverted. The cathode was improved by decreasing the pH, purging pure oxygen, and increasing the flow rate, which resulted in a 13-fold power density increase to 144 W m(-3) and a volumetric resistivity of only 1.2 mOmega m(3) per cell. Both results are major achievements compared to results currently published for laboratory and scaled-up MFCs. When designing a scaled-up MFC, it is important to ensure optimal contact between electrodes and substrate and to minimize the distances between electrodes. PMID:19943685

  7. Consideration of Numerical Simulation Parameters and Heat Transfer Models for a Molten Carbonate Fuel Cell Stack

    Energy Technology Data Exchange (ETDEWEB)

    Koh, J.H.; Seo, H.K.; Lim, H.C. [Korea Electric Power Research Institute, Taejon (Korea)

    2001-07-01

    A fuel cell stack model based on differential heat balance equations was solved numerically with a computational fluid dynamics code. Theoretical aspects in the simulation of a molten carbonate fuel cell (MCFC) performance model were discussed with regard to numerical accuracy of temperature prediction. The effect of grid setting for gas channel depth was studied to ensure how coarse it can be. A single computational element was sufficient for temperature prediction, while more grid elements are required for calculation of flow field and pressure distribution. The use of constant velocities is not recommended because it cannot account for the change of linear velocity within fuel cells, indicating the momentum equations have to be solved together with the heat balance equations. Thermal radiation has little effect on calculation of temperature field from the model. Gas properties vary within fuel cells, but most of them can be treated constant except for specific heat capacity of anode gas. Convection heat transfer by anode gas can be overestimated when a constant specific heat capacity is used, resulting in prediction of lower temperature curves. (author). 18 refs., 12 figs., 4 tabs.

  8. Design and development of a 7kW polymer electrolyte membrane fuel cell stack for UPS application

    Energy Technology Data Exchange (ETDEWEB)

    Squadrito, G.; Giacoppo, G.; Barbera, O.; Urbani, F.; Passalacqua, E. [CNR - Istituto di Tecnologie Avanzate per l' Energia ' ' Nicola Giordano' ' (CNR-ITAE), Salita S. Lucia sopra Contesse 5, 98126 Messina (Italy); Borello, L.; Musso, A.; Rosso, I. [Electro Power Systems spa (EPS), Via Grange Palmero 104, 10091 Alpignano (Italy)

    2010-09-15

    This work presents the PEMFC stack design methodology developed at CNR-ITAE, in the frame of a collaboration with an industrial partner, Electro Power Systems (EPS), operating in the Uninterruptable Power Supply (UPS) market. A detailed description of the design procedure of a 7 kW PEMFC stack is reported, starting from technical requirements of the UPS system to experimental tests. Bipolar plate layout, active area surface and shape, maximum (OCV) and minimum voltage, maximum cooling circuit pressure drop, maximum cathodic flow-field pressure drop, were the main constraint that influenced the constructive solutions. The electrochemical performances of Gore Primea 5621 MEA with SGL Sigracet GDL were chosen as reference to select the appropriate operating point in terms of current density and single cell voltage. A current density of 800 mA/cm{sup 2} was imposed as operating point of the stack, subsequently main stack parameters were calculated. Three different cathodic flow fields, that were designed to fulfill UPS system requirements, were tested in a single cell arrangement, to find the best gas flow path in terms of compromise between cell performance and pressure drop. Also a specific study was dedicated to the selection of gasket material to find the best compromise between cell performance and limited mechanical stress. The assembled 70 cells unit was tested in a test bench simulating the power system. Preliminary tests of the full unit yielded to a power of 6.2kW at 36 V. (author)

  9. 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.

  10. Experimental investigation on a turbine compressor for air supply system of a fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Matsuda, Masayasu [Sumitomo Heavy Industries, Ltd., Yokosuka (Japan); Tsuchiyama, Syozo [Shipbuilding Research Association, Minato-ku, Tokyo (Japan)

    1996-12-31

    This report covers part of a joint study on a PEFC propulsion system for surface ships, summarized in a presentation to this Seminar, entitled {open_quotes}Study on a Polymer Electrolyte Fuel Cell (PEFC) Propulsion System for Surface Ships{close_quotes}, and which envisages application to a 1,500 DWT cargo vessel. The aspect treated here concerns a study on the air supply system for the PEFC, with particular reference to system components.

  11. Electrodeposited ultrafine TaOx/CB catalysts for PEFC cathode application: Their oxygen reduction reaction kinetics

    KAUST Repository

    Seo, Jeongsuk

    2014-12-01

    Ultrafine TaOx nanoparticles were electrodeposited on carbon black (CB) powder in a nonaqueous Ta complex solution at room temperature, and the resultant TaOx/CB catalysts were assessed as oxygen reduction reaction (ORR) electrocatalysts for polymer electrolyte fuel cell (PEFC) cathodes. The Ta electrodeposition process was scaled up using a newly designed working electrode containing a CB dense layer, without introducing any binder such as the ionomer Nafion in the electrode for electrodeposition. The electrodeposited TaOx/CB powders were removed from the deposition electrode and subsequent H2 treatment at varying temperatures between 523 and 1073 K was attempted to increase the ORR performance. The TaOx/CB samples were characterized by SEM, STEM, XPS, and EELS measurements. XPS and EELS results indicated the reduced nature of the Ta species caused by the high-temperature treatment in H2, while STEM images clearly revealed that the TaOx particles aggregated as the treatment temperature increased. When the TaOx/CB catalyst, which was treated at 873 K for 2 h, was deposited on a glassy carbon substrate with Nafion ionomer, it resulted in the highest activity among the samples investigated, giving an onset potential of 0.95 VRHE at -2 μA cm-2 in a 0.1 M H2SO4 solution. Moreover, the long-term stability test with 10,000 cycles of the voltammetry only led to a 6% loss in the ORR currents, demonstrating the high stability of the TaOx/CB catalysts. Kinetic analysis by R(R)DE indicated that the four-electron transfer pathway in the ORR process was dominant for this TaOx/CB catalyst, and Tafel plots showed a slope corresponding to a one-electron reaction for the rate-determining step.

  12. Experimental Evaluation of a Pt-based Heat Exchanger Methanol Reformer for a HTPEM Fuel Cell Stack

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Kær, Søren Knudsen; Nielsen, Mads Pagh

    2008-01-01

    automotive applications. Using a liquid hydrocarbon as e.g. methanol as the hydrogen carrier and reforming it to a hydrogen rich gas can solve some of these storage issues. The work presented here examines the use of a heat exchanger methanol reformer for use with a HTPEM fuel cell stack. Initial...

  13. Estimation of Membrane Hydration Status for Standby Proton Exchange Membrane Fuel Cell Systems by Impedance Measurement: First Results on Variable Temperature Stack Characterization

    DEFF Research Database (Denmark)

    Bidoggia, Benoit; Kær, Søren Knudsen

    2013-01-01

    , the measurement of the complex impedance of a fuel cell stack during standby is used as an index of its membrane hydration status. In this article, the complex impedance of a fuel cell stack has been measured and characterized as a function of relative humidity and temperature. A non-conventional electrochemical...

  14. Parametric Characterization of Reformate-operated PBI-based High Temperature PEM Fuel Cell Stack

    DEFF Research Database (Denmark)

    Sahlin, Simon Lennart

    2016-01-01

    This paper presents an experimental characterization of a HT-PEMFC short stack performed by means of impedance spectroscopy. Selected operating parameters; temperature, stoichiometry and reactant compositions were varied to investigate their effects on a reformate operated stack. Polarization...

  15. The performance of a grid-tied microgrid with hydrogen storage and a hydrogen fuel cell stack

    International Nuclear Information System (INIS)

    Highlights: • Two microgrids with different structure are simulated. • Their performance are comprehensively evaluated and compared. • The one with DES and a FC stack has high environmental and quality indexes. - Abstract: In a heat-power system, the use of distributed energy generation and storage not only improves system’s efficiency and reliability but also reduce the emission. This paper is focused on the comprehensive performance evaluation of a grid-tied microgrid, which consists of a PV system, a hydrogen fuel cell stack, a PEM electrolyzer, and a hydrogen tank. Electricity and heat are generated in this system, to meet the local electric and heat demands. The surplus electricity can be stored as hydrogen, which is supplied to the fuel cell stack to generate heat and power as needed. The performance of the microgrid is comprehensively evaluated and is compared with another microgrid without a fuel cell stack. As a result, the emission and the service quality in the first system are higher than those in the second one. But they both have the same overall performance

  16. Measurements of water distributions in in-plane direction of a PEFC by using neutron radiography and analysis of gas-velocity distributions in the channel and the GDL

    International Nuclear Information System (INIS)

    Visualization and measurement of water distributions in a polymer electrolyte fuel cell (PEFC) were carried out by means of neutron radiography for clarifying water effects on the performances. The two-dimensional water distributions were applied for a network model. It analyzes the gas-velocity distributions depending on the local pressure drop which is affected by the gas-flow rate and the water accumulation. Formation of the accumulated water in the channel was assumed based on measurement results of water distributions in through-plane direction. Furthermore, it was estimated that maximum water accumulation in the gas diffusion layer (GDL) and mechanism of water discharge from the GDL to the channel. From the analysis results, change of gas-velocity distributions depending on the water accumulation in the PEFC could be obtained. (author)

  17. Performance and cost of automotive fuel cell systems with ultra-low platinum loadings

    Science.gov (United States)

    Ahluwalia, R. K.; Wang, X.; Kwon, J.; Rousseau, A.; Kalinoski, J.; James, B.; Marcinkoski, J.

    2011-05-01

    An automotive polymer-electrolyte fuel cell (PEFC) system with ultra-low platinum loading (0.15 mg-Pt cm-2) has been analyzed to determine the relationship between its design-point efficiency and the system efficiency at part loads, efficiency over drive cycles, stack and system costs, and heat rejection. The membrane electrode assemblies in the reference PEFC stack use nanostructured, thin-film ternary catalysts supported on organic whiskers and a modified perfluorosulfonic acid membrane. The analyses show that the stack Pt content can be reduced by 50% and the projected high-volume manufacturing cost by >45% for the stack and by 25% for the system, if the design-point system efficiency is lowered from 50% to 40%. The resulting penalties in performance are a system peak efficiency; a 2-4% decrease in the system efficiency on the urban, highway, and LA92 drive cycles; and a 6.3% decrease in the fuel economy of the modeled hybrid fuel-cell vehicle on the combined cycle used by EPA for emission and fuel economy certification. The stack heat load, however, increases by 50% at full power (80 kWe) but by only 23% at the continuous power (61.5 kWe) needed to propel the vehicle on a 6.5% grade at 55 mph. The reduced platinum and system cost advantages of further lowering the design-point efficiency from 40% to 35% are marginal. The analyses indicate that thermal management in the lower efficiency systems is very challenging and that the radiator becomes bulky if the stack temperature cannot be allowed to increase to 90-95 °C under driving conditions where heat rejection is difficult.

  18. Development and testing of a hybrid system with a sub-kW open-cathode type PEM (proton exchange membrane) fuel cell stack

    International Nuclear Information System (INIS)

    In this study, the performance of a polymer electrolyte membrane fuel cell stack has been evaluated for a hybrid power system test platform. To simulate vehicle acceleration, the stack was operated under dynamic-loading, and to demonstrate the exchange of power flow between two power sources the hybrid power system was tested under three different modes. A unit cell was fabricated for high stack performance and the stack was constructed with 18 open-cathode type fuel cells. Air which acts as a coolant as well as an oxidant for electrochemical reactions is provided by a pair of fans. The capabilities of the stack for hybrid power system test platform were validated by successful dynamic-loading tests. The performance of the stack for various air fan voltage was evaluated and an optimal value was concluded. The conditions like inlet temperature of H2 and the stack current were established for maximum power. It was also found that humidification of hydrogen at anode inlet degrades the stack performance and stability due to flooding. Evidence shows that for the higher overall performance, the fuel cell acts continuously on constant current output. The study contributes to the design of mobility hybrid system to get better performance and reliability. - Highlights: • An open-cathode type PEMFC (polymer electrolyte membrane fuel cell) stack (rated output 300 W) was fabricated. • The open-cathode configuration simplifies the design of a stack system. • Assess the feasibility of combining a fuel cell stack in a hybrid system. • The study contributes to the design of mobility hybrid system to get better performance and reliability

  19. Doping Evolution and Junction Formation in Stacked Cyanine Dye Light-Emitting Electrochemical Cells.

    Science.gov (United States)

    Jenatsch, Sandra; Wang, Lei; Bulloni, Matia; Véron, Anna C; Ruhstaller, Beat; Altazin, Stéphane; Nüesch, Frank; Hany, Roland

    2016-03-16

    Cyanine dyes are fluorescent organic salts with intrinsic conductivity for ionic and electronic charges. Recently ( J. Am. Chem. Soc. 2013 , 135 , 18008 - 18011 ), these features have been exploited in cyanine light-emitting electrochemical cells (LECs). Here, we demonstrate that stacked, constant-voltage driven trimethine cyanine LECs with various counteranions develop a p-i-n junction that is composed of p- and n-doped zones and an intrinsic region where light-emission occurs. We introduce a method that combines spectral photocurrent response measurements with optical modeling and find that at maximum current the intrinsic region is centered at ∼37% away from the anode. Transient capacitance, photoluminescence and attenuance experiments indicate a device situation with a narrow p-doped region, an undoped region that occupies ∼72% of the dye layer thickness and an n-doped region with a maximum doping concentration of 0.08 dopant/cyanine molecule. Finally, we observe that during device relaxation the parent cyanines are not reformed. We ascribe this to irreversible reactions between doped cyanine radicals. For sterically conservative cyanine dyes, this suggests that undesired radical decomposition pathways limit the LEC long-term stability in general. PMID:26914281

  20. NOx conversion on LSM15-CGO10 cell stacks with BaO impregnation

    DEFF Research Database (Denmark)

    Traulsen, Marie Lund; Andersen, Kjeld Bøhm; Kammer Hansen, Kent

    2012-01-01

    The electrochemical conversion of NOx on non-impregnated and BaO-impregnated LSM15-CGO10 (La0.85Sr0.15MnO3-Ce0.9Gd0.1O1.95) porous cell stacks has been investigated, and extensive impedance analysis have been performed to identify the effect of the BaO on the electrode processes. The investigation......O impregnation greatly enhanced the NOx conversion and at 400 degrees C and 9 V polarisation a BaO-impregnated cell stack showed 60% NOx conversion into N-2 with 8% current efficiency in 1000 ppm NO + 10% O-2. This demonstrates high NOx conversion can be achieved on an entirely ceramic cell without expensive...

  1. Assessment of Compliance with PEFC Forest Certification Indicators with Remote Sensing

    Directory of Open Access Journals (Sweden)

    Eugene Lopatin

    2016-04-01

    Full Text Available The majority of Finnish forests (95% are certified by the Programme for the Endorsement of Forest Certification (PEFC. It is a worldwide leading forest certification scheme. The aim of this study is to analyze the Finnish National Standard of PEFC certification and identify the indicators that can be reliably estimated with remote sensing (RS techniques. The retrieved data are further verified with a chosen geographical information system (GIS application. The rapid increase in certified areas globally has created a certain level of mistrust that makes the evaluation by certification bodies (CB questionable. Firstly, the area of the field audit is limited, and the verification results are based on sampling techniques. Secondly, the evaluation of the indicators of sustainable forest management (SFM is based on auditor expertise and thus is prone to bias. Thirdly, the actual condition of large forest stands in Eastern and Northern Finland are not easy to determine and verify. Thus, PEFC certification in Finland, in particular, faces numerous challenges in regard to the quality of field assessment due to the intensive forest management model with a high number of annual felling sites. At the same time, small scale and scattered harvesting sites are difficult to assess. Our proposed approach combined with remote assessment reliably verified 18% of the standard and could substantially reduce the costs associated with field audits in Finland. The results from our verification analysis are spatially explicit and geographically referenced and can be published in open access portals for interested parties. Moreover, it provides improved transparency in field assessments for the PEFC certification. The novel approach proposed here requires further investigation at larger scales (e.g., national level.

  2. Toughness of membranes applied in polymer electrolyte fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Kiefer, J.; Brack, H.P.; Scherer, G.G. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    Since several years we apply the radiation-grafting technique to prepare polymeric membranes for application in polymer electrolyte fuel cells (PEFCs). Our investigations presented here focus on changes in toughness of these materials after the various synthesis steps and the importance of membrane toughness for their application in PEFCs. (author) 2 figs., 4 refs.

  3. Numerical investigations on two-phase flow in polymer electrolyte fuel cells

    NARCIS (Netherlands)

    Qin, C.Z.

    2012-01-01

    Numerical modeling plays an important role in understanding various transport processes in polymer electrolyte fuel cells (PEFCs). It can not only provide insights into the development of new PEFC architectures, but also optimize operating conditions for better cell performance. Water balance is cri

  4. Algebraic Stacks

    Indian Academy of Sciences (India)

    Tomás L Gómez

    2001-02-01

    This is an expository article on the theory of algebraic stacks. After introducing the general theory, we concentrate in the example of the moduli stack of vector bundles, giving a detailed comparison with the moduli scheme obtained via geometric invariant theory.

  5. Simulation of a tubular solid oxide fuel cell stack using AspenPlusTM unit operation models

    International Nuclear Information System (INIS)

    The design of a fuel cell system involves both optimization of the fuel cell stack and the balance of plant with respect to efficiency and economics. Many commercially available process simulators, such as AspenPlusTM, can facilitate the analysis of a solid oxide fuel cell (SOFC) system. A SOFC system may include fuel pre-processors, heat exchangers, turbines, bottoming cycles, etc., all of which can be very effectively modelled in process simulation software. The current challenge is that AspenPlusTM or any other commercial process simulators do not have a model of a basic SOFC stack. Therefore, to enable performing SOFC system simulation using one of these simulators, one must construct an SOFC stack model that can be implemented in them. The most common approach is to develop a complete SOFC model in a programming language, such as Fortran, Visual Basic or C++, first and then link it to a commercial process simulator as a user defined model or subroutine. This paper introduces a different approach to the development of a SOFC model by utilizing existing AspenPlusTM functions and existing unit operation modules. The developed ''AspenPlusTM SOFC'' model is able to provide detailed thermodynamic and parametric analyses of the SOFC operation and can easily be extended to study the entire power plant consisting of the SOFC and the balance of plant without the requirement for linking with other software. Validation of this model is performed by comparison to a Siemens-Westinghouse 100 kW class tubular SOFC stack. Sensitivity analyses of major operating parameters, such as utilization factor (Uf), current density (Ic) and steam-carbon ratio (S/C), were performed using the developed model, and the results are discussed in this paper

  6. Stress compensation by gap monolayers for stacked InAs/GaAs quantum dots solar cells

    OpenAIRE

    Alonso Alvarez, Diego; González Taboada, Alfonso; González Diez, M. Yolanda; Ripalda Cobián, Jose María; Alén Millán, Benito; González Soto, Luisa; García Martín, Jorge Miguel; Luque López, Antonio; Martí Vega, Antonio; Briones Fernández-Pola, Fernando; Sánchez, Almudena M.; Molina Rubio, Sergio Ignacio

    2008-01-01

    In this work we report the stacking of 10 and 50 InAs quantum dots layers using 2 monolayers of GaP for stress compensation and a stack period of 18 nm on GaAs (001) substrates. Very good structural and optical quality is found in both samples. Vertical alignment of the dots is observed by transmission electron microscopy suggesting the existence of residual stress around them. Photocurrent measurements show light absorption up to 1.2 μm in the nanostructures together with a reduction in the ...

  7. Cooling Performance Characteristics of the Stack Thermal Management System for Fuel Cell Electric Vehicles under Actual Driving Conditions

    Directory of Open Access Journals (Sweden)

    Ho-Seong Lee

    2016-04-01

    Full Text Available The cooling performance of the stack radiator of a fuel cell electric vehicle was evaluated under various actual road driving conditions, such as highway and uphill travel. The thermal stability was then optimized, thereby ensuring stable operation of the stack thermal management system. The coolant inlet temperature of the radiator in the highway mode was lower than that associated with the uphill mode because the corresponding frontal air velocity was higher than obtained in the uphill mode. In both the highway and uphill modes, the coolant temperatures of the radiator, operated under actual road driving conditions, were lower than the allowable limit (80 °C; this is the maximum temperature at which stable operation of the stack thermal management system of the fuel cell electric vehicle could be maintained. Furthermore, under actual road driving conditions in uphill mode, the initial temperature difference (ITD between the coolant temperature and air temperature of the system was higher than that associated with the highway mode; this higher ITD occurred even though the thermal load of the system in uphill mode was greater than that corresponding to the highway mode. Since the coolant inlet temperature is expected to exceed the allowable limit (80 °C in uphill mode under higher ambient temperature with air conditioning system operation, the FEM design layout should be modified to improve the heat capacity. In addition, the overall volume of the stack cooling radiator is 52.2% higher than that of the present model and the coolant inlet temperature of the improved radiator is 22.7% lower than that of the present model.

  8. Live-Cell Imaging of Dual-Labeled Golgi Stacks in Tobacco BY-2 Cells Reveals Similar Behaviors for Different Cisternae during Movement and Brefeldin A Treatment

    Institute of Scientific and Technical Information of China (English)

    Stephanie L. Madison; Andreas Nebenführ

    2011-01-01

    In plant cells,the Golgi apparatus consists of numerous stacks that,in turn,are composed of several flattened cisternae with a clear cis-to-trans polarity.During normal functioning within living cells,this unusual organelle displays a wide range of dynamic behaviors such as whole stack motility,constant membrane flux through the cisternae,and Golgi enzyme recycling through the ER.In order to further investigate various aspects of Golgi stack dynamics and integrity,we co-expressed pairs of established Golgi markers in tobacco BY-2 cells to distinguish sub-compartments of the Golgi during monensin treatments,movement,and brefeldin A (BFA)-induced disassembly.A combination of cis and trans markers revealed that Golgi stacks remain intact as they move through the cytoplasm.The Golgi stack orientation during these movements showed a slight preference for the cis side moving ahead,but trans cisternae were also found at the leading edge.During BFA treatments,the different sub-compartments of about half of the observed stacks fused with the ER sequentially; however,no consistent order could be detected.In contrast,the ionophore monensin resulted in swelling of trans cisternae while medial and particularly cis cisternae were mostly unaffected.Our results thus demonstrate a remarkable equivalence of the different cisternae with respect to movement and BFA-induced fusion with the ER.In addition,we propose that a combination of dual-label fluorescence microscopy and drug treatments can provide a simple alternative approach to the determination of protein localization to specific Golgi sub-compartments.

  9. Mass and charge transfer on various relevant scales in polymer electrolyte fuel cells[Dissertation 16991

    Energy Technology Data Exchange (ETDEWEB)

    Freunberger, S. A.

    2007-07-01

    This dissertation is concerned with the development, experimental diagnostics and mathematical modelling and simulation of polymer electrolyte fuel cells (PEFC). The central themes throughout this thesis are the closely interlinked phenomena of mass and charge transfer. In the face of developing a PEFC system for vehicle propulsion these phenomena are scrutinized on a broad range of relevant scales. Starting from the material related level of the membrane and the gas diffusion layer (GDL) we turn to length scales, where structural features of the cell additionally come into play. These are the scale of flow channels and ribs, the single cell and the cell stack followed by the cell, stack, and system development for an automotive power train. In Chapter 3 selected fundamental material models and properties, respectively, are explored that are crucial for the mathematical modelling and simulation of PEFC, as needed in some succeeding parts of this work. First, established mathematical models for mass and charge transfer in the membrane are compared within the framework of the membrane electrode assembly (MEA), which represents the electrochemical unit. Second, reliable values for effective diffusivities in the GDLs which are vital for the simulation of gaseous mass transport are measured. Therefore, a method is developed that allows measuring this quantity both as a function of compression and direction as this is a prerequisite of sophisticated more-dimensional numerical PEFC-models. Besides the cross section of the catalyst layer (CL) mass transfer under channels and ribs is considered as a major source of losses in particular under high load operation. As up to now there have been solely non-validated theoretical investigations, in Chapter 4 an experimental method is developed that is for the first time capable of resolving the current density distribution on the this scale. For this, the electron conductors in the cell are considered as 2-dimensional shunt

  10. Directly connected series coupled HTPEM fuel cell stacks to a Li-ion battery DC bus for a fuel cell electrical vehicle

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Ashworth, Leanne; Remón, Ian Natanael;

    2008-01-01

    connected directly parallel to the battery pack during operation. This enables efficient charging of the batteries for increased driving range. With no power electronics used, the fuel cell stacks follow the battery pack voltage, and charge the batteries passively. This saves the electrical and economical...

  11. Employing Hot Wire Anemometry to Directly Measure the Water Balance of a Commercial Proton Exchange Membrane Fuel Cell Stack

    DEFF Research Database (Denmark)

    Shakhshir, Saher Al; Berning, Torsten

    increased degradation rates. Clearly, a fundamental understanding of all aspects of water management in PEMFC is imperative. This includes the fuel cell water balance, i.e. which fraction of the product water leaves the fuel cell via the anode channels versus the cathode channel. Our research group is...... currently developing a novel technique to obtain an ad-hoc and real time electrical signal of the fuel cell water balance by employing hot wire anemometry. In this work, the hot wire sensor is placed in the anode outlet of a commercial air-cooled fuel cell stack by Ballard Power Systems, and the voltage......Proton exchange membrane fuel cells (PEMFC’s) are currently being commercialized for various applications ranging from automotive (e.g. the Toyota Mirai) to stationary such as powering telecom backup units. In PEMFC’s, oxygen from air is internally combined with hydrogen to form water and produce...

  12. Investigation of the flow field inside the manifold of a real operated fuel cell stack using optical measurements and Computational Fluid Mechanics

    Science.gov (United States)

    Schmieder, Felix; Kinaci, Mustafa E.; Wartmann, Jens; König, Jörg; Büttner, Lars; Czarske, Jürgen; Burgmann, Sebastian; Heinzel, Angelika

    2016-02-01

    The versatility of fuel cells enables a wide range of applications. Usually fuel cells are combined to stacks such that the reactant supply of the single cells is achieved via a pipe branching system, the manifold. The overall performance significantly depends on cell flow rates which are related to the fluidic interaction of the manifold and the cells. Computational Fluid Dynamics (CFD) simulations, which are often used to find a suitable design, lack experimental flow data for validation of the numerical results. To enable flow measurements within the small geometries of the manifold and to provide reliable velocity information inside a real fuel cell stack, a low-coherence Laser Doppler Anemometer (LDA) is applied, which uses multi-mode laser light to achieve a spatial resolution of <100 μm. The use of fluorescent particles and backward scatter mode make the sensor highly suitable for the application in small manifold geometries like in fuel cell stacks. Sensor and measurement technique are validated in simplified stack models and the applicability to air flows is demonstrated. Finally, for the first time, velocity profiles with high spatial resolution inside an operated fuel cell stack are presented, which serve as benchmark for CFD to find an optimal geometry.

  13. Heat balance of a molten carbonate fuel cell production hydrogen for a polymer electrolyte fuel cell-CoCell; Waermehaushalt einer Karbonat-Brennstoffzelle zur Wasserstoffherstellung fuer eine Polymerelektrolyt-Brennstoffzelle

    Energy Technology Data Exchange (ETDEWEB)

    Adamek, L.

    2006-10-17

    Molten carbonate fuel cells (MCFC) are being used in decentralised power plants, as they can reform hydrocarbon bound fuels internally, e.g. natural gas with a energy density of 10 kWh/m{sup 3} at standard conditions, and the efficiency of this mode of operation is around 50 %. However in comparison to other fuel cell systems the power density is only 5 kW/m{sup 3}. The power density of a polymerelectrolyte fuel cell (PEFC) is much higher (50 kW/m{sup 3}). These systems can be run with an efficiency of 50 %, too. Therefore they need hydrogen as a fuel, with an energy density of 2,9 kWh/m{sup 3} at standard conditions. Efficiency decreases to 35 to 40% using Methane as fuel, because of the reforming losses. The power density than is 6 kW/m3 and therefore as high as for a MCFC-system. Acombination of MCFC and PEFC, the so called CoCell, offers the following advantages: - A highly energetic, hydrocarbon based fuel can be used, e.g. Methane. - A high electrical efficiency is achieved. - The power density of this system is higher than for a fuel cell with reformer. In the CoCell the MCFC is working as electricity producing reformer for the PEFC. The off heat of the MCFC is used for reforming, whereby hydrogen is available, being utilised further in the power dense PEFC. The reforming capacity of the MCFC is limited by the internal heat balance. If the endothermic reforming consumes more heat than supplied by the material streams and the fuel cell waste heat, the stack cools down. The performance of such a combined fuel cell system has been evaluated in this thesis using the thermodynamic simulation software Aspen. Calculations reducing the utilisation in the MCFC by various heating techniques showed, that additional heat is supplied most efficiently by increasing the current density of the MCFC. Thereby the stack is heated electrically and the power density of the system is increased by the improved power density of the MCFC. The reduction of the utilisation is achieved

  14. Transients of Water Distribution and Transport in PEFCs

    KAUST Repository

    Hussaini, Irfan

    2008-01-01

    Response of PEM fuel cells to a step-change in load is investigated experimentally in this work. Voltage undershoot, a characteristic feature of such transient response, is shown to be due to transients of water distribution in membrane phase occurring at sub-second time scales. Use of humidified reactants as a means to control magnitude of voltage undershoot has been demonstrated. Constant stoichiometry operation under certain current-step conditions is found to result in reactant starvation, potentially leading to cell shut down. Further, response under step decrease in current density has been explored to determine existence of hysteresis. Under sufficiently humidified conditions, response under forward and reverse step changes are found to be symmetric, but under low RH conditions, voltage undershoot is found to be twice as large as the overshoot. © The Electrochemical Society.

  15. Investigation of sulfonated polysulfone membranes as electrolyte in a passive-mode direct methanol fuel cell mini-stack

    Energy Technology Data Exchange (ETDEWEB)

    Lufrano, F.; Baglio, V.; Staiti, P.; Stassi, A.; Arico, A.S.; Antonucci, V. [CNR - ITAE, Istituto di Tecnologie Avanzate per l' Energia ' ' Nicola Giordano' ' , Via Salita S. Lucia sopra Contesse n. 5 - 98126 S. Lucia - Messina (Italy)

    2010-12-01

    This paper reports on the development of polymer electrolyte membranes (PEMs) based on sulfonated polysulfone for application in a DMFC mini-stack operating at room temperature in passive mode. The sulfonated polysulfone (SPSf) with two degrees of sulfonation (57 and 66%) was synthesized by a well-known sulfonation process. SPSf membranes with different thicknesses were prepared and investigated. These membranes were characterized in terms of methanol/water uptake, proton conductivity, and fuel cell performance in a DMFC single cell and mini-stack operating at room temperature. The study addressed (a) control of the synthesis of sulfonated polysulfone, (b) optimization of the assembling procedure, (c) a short lifetime investigation and (d) a comparison of DMFC performance in active-mode operation vs. passive-mode operation. The best passive DMFC performance was 220 mW (average cell power density of about 19 mW cm{sup -2}), obtained with a thin SPSf membrane (70 {mu}m) at room temperature, whereas the performance of the same membrane-based DMFC in active mode was 38 mW cm{sup -2}. The conductivity of this membrane, SPSf (IEC = 1.34 mequiv. g{sup -1}) was 2.8 x 10{sup -2} S cm{sup -1}. A preliminary short-term test (200 min) showed good stability during chrono-amperometry measurements. (author)

  16. Evaluation of in-plane local stress distribution in stacked IC chip using dynamic random access memory cell array for highly reliable three-dimensional IC

    Science.gov (United States)

    Tanikawa, Seiya; Kino, Hisashi; Fukushima, Takafumi; Koyanagi, Mitsumasa; Tanaka, Tetsu

    2016-04-01

    As three-dimensional (3D) ICs have many advantages, IC performances can be enhanced without scaling down of transistor size. However, 3D IC has mechanical stresses inside Si substrates owing to its 3D stacking structure, which induces negative effects on transistor performances such as carrier mobility changes. One of the mechanical stresses is local bending stress due to organic adhesive shrinkage among stacked IC chips. In this paper, we have proposed an evaluation method for in-plane local stress distribution in the stacked IC chips using retention time modulation of a dynamic random access memory (DRAM) cell array. We fabricated a test structure composed of a DRAM chip bonded on a Si interposer with dummy Cu/Sn microbumps. As a result, we clarified that the DRAM cell array can precisely evaluate the in-plane local stress distribution in the stacked IC chips.

  17. Type II GaSb/GaAs quantum dot/ring stacks with extended photoresponse for efficient solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Carrington, Peter James, E-mail: p.carrington@lancaster.ac.uk [Physics Department, Lancaster University, Lancaster LA1 4YB (United Kingdom); Mahajumi, Abu Syed [Physics Department, Lancaster University, Lancaster LA1 4YB (United Kingdom); Wagener, Magnus C.; Botha, Johannes Reinhardt [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Zhuang Qian; Krier, Anthony [Physics Department, Lancaster University, Lancaster LA1 4YB (United Kingdom)

    2012-05-15

    We report on the fabrication of GaAs based p-i-n solar cells containing 5 and 10 layers of type II GaSb quantum rings grown by molecular beam epitaxy. Solar cells containing quantum rings show improved efficiency at longer wavelengths into the near-IR extending up to 1500 nm and show enhanced short-circuit current under 1 sun illumination compared to a GaAs control cell. A reduction in the open-circuit voltage is observed due to the build-up of internal strain. The MBE growth, formation and photoluminescence of single and stacked layers of GaSb/GaAs quantum rings are also presented.

  18. An experimental study of the dynamic behavior of a 2 kW proton exchange membrane fuel cell stack under various loading conditions

    International Nuclear Information System (INIS)

    The dynamic behavior of the PEM (proton exchange membrane) fuel cell stack has great effect on the safety and effective operation of its applications. In this paper, a self-designed bulb-array is used to simulate the various loading conditions and study the dynamic behavior of a 2 kW PEM fuel cell stack. An evaluation index, including oscillation rate, pressure variation and dynamic resistance factor, is used to analyze the transient response of the PEM fuel cell stack. It is observed that the stack current increases about 8.6%, and the Oscillation rate decreases more rapidly after activation. In the step-up load stage, the oscillation rate and the dynamic resistance decrease more rapidly as the external load increases. Due to the periodic anodic purge process, a periodic voltage fluctuation can be seen. In addition, when the stack works in the open-loop state (working without the external load), the transient response of the stack current is significantly affected by the hydrogen humidity and the charge double-layer. - Highlights: • The working time of open-loop state significantly affects the transient response. • Oscillation rate decreases faster as the external load increases. • Dynamic resistance factor decreases as the external load increases. • The periodic anodic purge process leads to a slight periodic oscillation of voltage

  19. Process analysis of a liquid-feed direct methanol fuel cell system

    Science.gov (United States)

    Andrian, Stefanie v.; Meusinger, Josefin

    Recently, a greatly increasing interest in solid polymer electrolyte fuel cells (PEFC) for a range of applications has been observed. The direct methanol fuel cell (DMFC) based on a PEFC uses methanol directly for electric power generation and promises technical advantages, for example, for power trains. This study analyses the interaction between a DMFC stack fed with a liquid aqueous methanol solution and the peripheral system equipment. A simulation model of a DMFC system for mobile applications (from methanol to net electricity) is presented to calculate system efficiencies on the basis of thermodynamic engineering calculations. Based on the simulation calculations, useful operating requirements can be specified. To optimise the performance of DMFC systems, it is necessary to consider the operational characteristics of all the components required in the system. There are worldwide activities to improve the performance of a DMFC stack, which depends on numerous operating parameters. But it is not sufficient to optimise only the current/potential curves of the fuel cell without taking all the consequences for the system into consideration. The results of the computer simulation presented here emphasise the difficulties in improving fuel cell performance without decreasing system efficiency and describes the consequences for the system's operation conditions. Priorities are additionally set concerning the heat management of the fuel cell stack. In the case of liquid fuel supply, the water crossover through the membrane and the ensuing vapourisation at the cathode side impairs the thermal balance. Key operating parameters, which influence these effects, are pressure, temperature, air flow and methanol permeation rate.

  20. Channeling of electron transport to improve collection efficiency in mesoporous titanium dioxide dye sensitized solar cell stacks

    Energy Technology Data Exchange (ETDEWEB)

    Fakharuddin, Azhar; Ahmed, Irfan; Yusoff, Mashitah M.; Jose, Rajan, E-mail: rjose@ump.edu.my, E-mail: joserajan@gmail.com [Nanostructured Renewable Energy Materials Laboratory, Faculty of Industrial Sciences and Technology, Universiti Malaysia Pahang, 26300 Pahang (Malaysia); Khalidin, Zulkeflee [Faculty of Electrical and Electronics Engineering, Universiti Malaysia Pahang, 26300 Pahang (Malaysia)

    2014-02-03

    Dye-sensitized solar cell (DSC) modules are generally made by interconnecting large photoelectrode strips with optimized thickness (∼14 μm) and show lower current density (J{sub SC}) compared with their single cells. We found out that the key to achieving higher J{sub SC} in large area devices is optimized photoelectrode volume (V{sub D}), viz., thickness and area which facilitate the electron channeling towards working electrode. By imposing constraints on electronic path in a DSC stack, we achieved >50% increased J{sub SC} and ∼60% increment in photoelectric conversion efficiency in photoelectrodes of similar V{sub D} (∼3.36 × 10{sup −4} cm{sup 3}) without using any metallic grid or a special interconnections.

  1. Performance of a 1 kW Class Nafion-PTFE Composite Membrane Fuel Cell Stack

    Directory of Open Access Journals (Sweden)

    Pattabiraman Krishnamurthy

    2012-01-01

    Full Text Available Composite membranes have been prepared by impregnation of Nafion into the expanded polytetrafluoroethylene (EPTFE matrix. Nafion loading in the composite membranes was kept constant at 2 mg/cm2. The lower amount of electrolyte per unit area in the composite membranes offers cost advantages compared to conventional membrane of 50 μm thickness with an electrolyte loading of ~9 mg/cm2. Composite membranes (30 μm thickness were found to have higher thermal stability and mechanical strength compared to the conventional membranes (50 μm thickness. The performance of the membrane electrode assembly made with these composite membranes was comparable to that of the conventional membranes. Single cells fabricated from these MEAs were tested for their performance and durability before scaling them up for large area. The performance of a 20-cell stack of active area 330 cm2 fabricated using these membranes is reported.

  2. Channeling of electron transport to improve collection efficiency in mesoporous titanium dioxide dye sensitized solar cell stacks

    International Nuclear Information System (INIS)

    Dye-sensitized solar cell (DSC) modules are generally made by interconnecting large photoelectrode strips with optimized thickness (∼14 μm) and show lower current density (JSC) compared with their single cells. We found out that the key to achieving higher JSC in large area devices is optimized photoelectrode volume (VD), viz., thickness and area which facilitate the electron channeling towards working electrode. By imposing constraints on electronic path in a DSC stack, we achieved >50% increased JSC and ∼60% increment in photoelectric conversion efficiency in photoelectrodes of similar VD (∼3.36 × 10−4 cm3) without using any metallic grid or a special interconnections

  3. Analysis and modeling of PEM fuel cell stack performance: Effect of in situ reverse water gas shift reaction and oxygen bleeding

    Science.gov (United States)

    Karimi, G.; Li, Xianguo

    In this study the performance of a polymer electrolyte membrane (PEM) fuel cell stack is analyzed with a mathematical model when the stack operates on hydrocarbon reformate gas as the anode feed stream. It is shown that the effect of carbon dioxide dilution of the hydrogen dominated reformate gas has a minimal impact on the stack performance. However, the CO-poisoning effect due to the in situ reverse water gas shift reaction in the anode feed stream could have a very serious adverse impact on the stack performance, especially at high current densities. Thermodynamic calculations indicate that the equilibrium concentrations of CO could be as high as 100 ppm, generated by the in situ reverse water gas shift reaction, under the typical conditions of PEM fuel cell operation; and are influenced by the stack operating temperature and water content of the reformate anode feed. This CO-poisoning of the stack performance is shown mitigated effectively by introducing about 0.5-1% oxygen to the anode feed.

  4. Sustainable water desalination and electricity generation in a separator coupled stacked microbial desalination cell with buffer free electrolyte circulation.

    Science.gov (United States)

    Chen, Xi; Liang, Peng; Wei, Zhimou; Zhang, Xiaoyuan; Huang, Xia

    2012-09-01

    A separator coupled circulation stacked microbial desalination cell (c-SMDC-S) was constructed to stabilize the pH imbalances in MDCs without buffer solution and achieved the stable desalination. The long-term operation of c-SMDC-S, regular stacked MDC (SMDC) and no separator coupled circulation SMDC (c-SMDC) were tested. The SMDC and c-SMDC could only stably operate for 1 week and 1 month owing to dramatic anolyte pH decrease and serious biofilm growth on the air cathode, respectively. The c-SMDC-S gained in anolyte alkalinity and operated stably for about 60 days without the thick biofilm growth on cathode. Besides, the chemical oxygen demand removal and coulombic efficiency were 64 ± 6% and 30 ± 2%, higher than that of SMDC and c-SMDC, respectively. It was concluded that the circulation of alkalinity could remove pH imbalance while the separator could expand the operation period and promote the conversion of organic matter to electricity. PMID:22728187

  5. PEM Fuel Cell Freeze Durability and Cold Start Project

    Energy Technology Data Exchange (ETDEWEB)

    Patterson, T.; O' Neill, Jonathan

    2008-01-02

    UTC has taken advantage of the unique water management opportunities inherent in micro-porous bipolar-plates to improve the cold-start performance of its polymer electrolyte fuel cells (PEFC). Diagnostic experiments were used to determine the limiting factors in micro-porous plate PEFC freeze performance and the causes of any performance decay. Alternative cell materials were evaluated for their freeze performance. Freeze-thaw cycling was also performed to determine micro-porous plate PEFC survivability. Data from these experiments has formed the basis for continuing development of advanced materials capable of supporting DOE's cold-start and durability objectives.

  6. Development and durability of SOFC stacks

    Energy Technology Data Exchange (ETDEWEB)

    Beeaff, D.; Dinesen, A.R.; Mikkelsen, Lars; Nielsen, Karsten A.; Solvang, M.; Hendriksen, Peter V.

    2004-12-01

    The present project is a part of the Danish SOFC programme, which has the overall aim of establishing a Danish production of SOFC - cells, stacks and systems for economical and environmentally friendly power production. The aim of the present project was to develop and demonstrate (on a small scale, few cells, few thousand hours) a durable, thermally cyclable stack with high performance at 750 deg. C. Good progress towards this target has been made and demonstrated at the level of stack-elements (one cell between two interconnects) or small stacks (3 5 cells). Three different stacks or stack-elements have been operated for periods exceeding 3000 hr. The work has covered development of stack-components (seals, interconnects, coatings, contact layers), establishment of procedures for stack assembly and initiation, and detailed electrical characterisation with the aims of identifying performance limiting factors as well as long term durability. Further, post test investigations have been carried out to identify possible degradation mechanisms. (BA)

  7. Charge–discharge performance of carbon fiber-based electrodes in single cell and short stack for vanadium redox flow battery

    International Nuclear Information System (INIS)

    Highlights: • Carbon-fiber based electrodes are investigated in a zero-gap flow field cell configuration. • Charge–discharge curves are carried out in single cell and short stack for VRB application. • Three electrode half-cell data are corroborated both in single cell and short stack for VRB. - Abstract: Electrode materials, having a different graphitic character, are investigated by using a zero-gap flow field cell configuration for vanadium redox flow battery applications (VRFBs). Carbon felt (CF) and carbon paper (CP) are used as electrodes for the membrane–electrode assemblies (MEAs) realization. The samples are electrochemically characterized both as-received and after chemical treatment by using a 5 cm2 single cell. A Nafion 117 membrane is used as polymer electrolyte separators. A MEAs scale-up from 5 to 25 cm2 is carried out in order to assembly a 3-cells short stack in series connected. Charge–discharge cycles are carried out both in a small area single cell and in a 3-cells short stack for all samples. CF treated and untreated samples show SOC values of 45% vs. 22% at 60 mA cm−2, respectively. After the chemical treatment, the worst performance of the CF sample is attributed to the mass transport issues due to the beginning of corrosion phenomena. On the contrary, CP treated electrode shows a better energy efficiency values than raw sample (72% vs. 67% at 60 mA cm−2) without any morphology change on the electrode surface. A proper stack assembly and flow field scale-up record similar performance to the small single cell configuration

  8. Optimization of Al2O3/SiNx stacked antireflection structures for N-type surface-passivated crystalline silicon solar cells

    International Nuclear Information System (INIS)

    In the case of N-type solar cells, the anti-reflection property, as one of the important factors to further improve the energy-conversion efficiency, has been optimized using a stacked Al2O3/SiNx layer. The effect of SiNx layer thickness on the surface reflection property was systematically studied in terms of both experimental and theoretical measurement. In the stacked Al2O3/SiNx layers, results demonstrated that the surface reflection property can be effectively optimized by adding a SiNx layer, leading to the improvement in the final photovoltaic characteristic of the N-type solar cells. (semiconductor devices)

  9. Long-term evaluation of solid oxide fuel cell candidate materials in a 3-cell generic short stack fixture, Part II: sealing glass stability, microstructure and interfacial reactions.

    Energy Technology Data Exchange (ETDEWEB)

    Chou, Y. S.; Stevenson, Jeffry W.; Choi, Jung-Pyung

    2014-03-15

    A generic solid oxide fuel cell stack test fixture was developed to evaluate candidate materials and processing methods under realistic conditions. Part I of the work addressed the stack fixture, seal system and cell performance of a 3-cell short stack tested at 800oC for 6000h. Commercial NiO-YSZ anode-supported thin YSZ electrolyte cells with LSM cathodes were used for assessment and were tested in constant current mode with dilute (~50% H2) fuel versus air. Part II of the work examined the sealing glass stability, microstructure development, interfacial reactions, and volatility issues. Part III of the work investigated the stability of Ce-(Mn,Co) spinel coating, AISI441 metallic interconnect, alumina coating, and cell degradation. After 6000h of testing, the refractory sealing glass YSO77 (Ba-Sr-Y-B-Si) showed desirable chemical compatibility with YSZ electrolyte in that no discernable interfacial reaction was identified, consistent with thermodynamic calculations. In addition, no glass penetration into the thin electrolyte was observed. At the aluminized AISI441 interface, the protective alumina coating appeared to be corroded by the sealing glass. Air side interactions appeared to be more severe than fuel side interactions. Metal species such as Cr, Mn, and Fe were detected in the glass, but were limited to the vicinity of the interface. No alkaline earth chromates were found at the air side. Volatility was also studied in a similar glass and weight loss in a wet reducing environment was determined. Using the steady-state volatility data, the life time (40,000h) weight loss of refractory sealing glass YSO77 was estimated to be less than 0.1 wt%.

  10. Cu2ZnSn(S,Se)4 solar cells processed by rapid thermal processing of stacked elemental layer precursors

    International Nuclear Information System (INIS)

    In this contribution we report on the development of a two-step process for the formation of Cu2ZnSn(S,Se)4 thin films for solar cells. The two-step formation process of the pentanary kesterite consists of (i) sputter deposition of the metals Cu, Zn and Sn followed by thermal evaporation of chalcogen and (ii) rapid thermal processing of the metal/chalcogen precursors in chalcogen containing ambient. After the absorber formation process, solar cells were processed by deposition of CdS buffer, window layer and metal grid. We evaluated different metal precursor compositions in the ternary Cu–Zn–Sn metal systems regarding their behavior as appropriate precursors for the crystallization of Cu2ZnSn(S,Se)4 absorbers. X-ray diffraction analyses show the presence of secondary chalcogenide phases in absorbers with Cu-poor composition. In combination with Raman spectroscopy, the efficient sulfoselenization could be demonstrated. A broad compositional region is found giving cell efficiencies above 6% via this process route and the potentials for further improvements are discussed. The best solar cell measured so far reached 6.6% efficiency on 1.34 cm2 cell size. - Highlights: ► Kesterite absorber layers via rapid thermal process from stacked elemental layers ► Relative sulfur content of 7–28% was deduced from Raman measurements. ► Identification of secondary phases via X-ray diffraction ► Best cell with 6.6% efficiency on a cell size of 1.34 cm2 ► Best cell performance was found for either low Cu-content or high Zn-content

  11. Preparation and Photovoltaic Properties of Dye Sensitized Solar Cells Using ZnO Nanorods Stacking Films on AZO Substrate as Photoanode.

    Science.gov (United States)

    Xu, Yang; Wang, Xina; Liu, Rong; Wang, Hao

    2016-04-01

    Three-dimensional stacking of ZnO nanorods on conducting aluminum-doped ZnO (AZO) glass were studied as efficient photoanodes of dye sensitized solar cells (DSSCs). By changing hydrothermal growth time and cycle times, the thickness of ZnO nanorods stacking films varied from 30 µm to 64 µm, and its influence on the energetic conversion efficiency of the DSSCs based on the stacking films photoanodes was investigated. The loading density of N719 on the surface of ZnO nanorods was studied to increase the efficiency of the cells. Annealing experiments showed that the AZO substrates remained good conductors until heated above 350 °C. A photoelectric conversion efficiency as high as ~2.0% together with ISC of ~9.5 mA/cm2, VOC of ~0.5 V and FF of ~41.4% was achieved for the DSSC using 50 µm-thick film stacking by ZnO nanorods as photoanode and N719 as sensitizer under illumination of AM1.5G solar light (power density of 100 mW/cm2). A charge separation and transfer mechanism was proposed for the ZnO nanorods stacking electrode-based DSSCs. PMID:27451677

  12. Impact of power converter current ripple on the durability of a fuel cell stack

    OpenAIRE

    WAHDAME, B; GIRARDOT, L; Hissel, D.; Harel, F.; Francois, X.; Candusso, D.; PERA, MC; DUMERCY, L

    2008-01-01

    The durability and performance of Polymer Electrolyte Membrane Fuel Cell (PEMFC) have a major impact on the most important challenges facing fuel cell commercialization including final cost, mass production, system integration, functionality and reliability. This work is supported by French Government via an ANR' project (PAN'H) named SPACT80. The global objective is to develop and validate the use of a fuel cell based power system for heavy-duty vehicles (dedicated to railway applications or...

  13. NASA Glenn Research Center's Fuel Cell Stack, Ancillary and System Test and Development Laboratory

    Science.gov (United States)

    Loyselle, Patricia L.; Prokopius, Kevin P.; Becks, Larry A.; Burger, Thomas H.; Dick, Joseph F.; Rodriguez, George; Bremenour, Frank; Long, Zedock

    2011-01-01

    At the NASA Glenn Research Center, a fully operational fuel cell test and evaluation laboratory is available which is capable of evaluating fuel cell components and systems for future NASA missions. Components and subsystems of various types can be operated and monitored under a variety of conditions utilizing different reactants. This fuel cell facility can test the effectiveness of various component and system designs to meet NASA's needs.

  14. Sizing stack and battery of a fuel cell hybrid distribution truck

    NARCIS (Netherlands)

    Bosch, P.P.J. van den; Hofman, T.; Veenhuizen, Bram; Shen, Y.; Tazelaar, Edwin

    2012-01-01

    Fuel cell hybrid vehicles are believed to provide a solution to cut down emissions in the long term. They provide local zero-emission propulsion and when the hydrogen as fuel is derived from renewable energy sources, fuel cell hybrids enable well-to-wheel zero-emission transportation,

  15. Estimation of Membrane Hydration Status for Standby Proton Exchange Membrane Fuel Cell Systems by Impedance Measurement: First Results on Stack Characterization

    DEFF Research Database (Denmark)

    Bidoggia, Benoit; Kær, Søren Knudsen

    Fuel cells have started replacing traditional lead-acid battery banks in backup systems. Although these systems are characterized by long periods of standby, they must be able to start at any instant in the shortest time. In the case of low temperature proton exchange membrane fuel cell systems, a...... precise estimation of hydration status of the fuel cell during standby is important for a fast and safe startup. In this article, the measurement of the complex impedance of the fuel cell is suggested as a method to estimate the membrane hydration status. A 56-cell fuel cell stack has been symmetrically...

  16. Long-term evaluation of solid oxide fuel cell candidate materials in a 3-cell generic short stack fixture, Part II: Sealing glass stability, microstructure and interfacial reactions

    Science.gov (United States)

    Chou, Yeong-Shyung; Stevenson, Jeffry W.; Choi, Jung-Pyung

    2014-03-01

    A generic solid oxide fuel cell stack test fixture was developed to evaluate candidate materials and processing methods under realistic conditions. Part II of the work examined the sealing glass stability, microstructure development, interfacial reaction, and volatility issues of a 3-cell stack with LSM-based cells. After 6000 h of testing, the refractory sealing glass YSO7 showed desirable chemical compatibility with YSZ electrolyte in that no discernable interfacial reaction was identified. In addition, no glass penetration into the thin electrolyte was observed. At the aluminized AISI441 interface, the protective alumina coating appeared to be corroded by the sealing glass. Air side interactions appeared to be more severe than fuel side interactions. Metal species such as Cr, Mn, and Fe were detected in the glass, but were limited to the vicinity of the interface. No alkaline earth chromates were found at the air side. Volatility was also studied in a similar glass and weight loss in a wet reducing environment was determined. Using the steady-state volatility data, the life time weight loss of refractory sealing glass YSO77 was estimated to be less than 0.1 wt%.

  17. Experimental study on the 300W class planar type solid oxide fuel cell stack: Investigation for appropriate fuel provision control and the transient capability of the cell performance

    International Nuclear Information System (INIS)

    The present paper reports the experimental study on the dynamic behavior of a solid oxide fuel cell (SOFC). The cell stack consists of planar type cells with standard power output 300W. A Major subject of the present study is characterization of the transient response to the electric current change, assuming load-following operation. The present studies particularly focus on fuel provision control to the load change. Optimized fuel provision improves power generation efficiency. However, the capability of SOFC must be restricted by a few operative parameters. Fuel utilization factor, which is defined as the ratio of the consumed fuel to the supplied fuel is adopted for a reference in the control scheme. The fuel flow rate was regulated to keep the fuel utilization at 50%, 60% and 70% during the current ramping. Lower voltage was observed with the higher fuel utilization, but achieved efficiency was higher. The appropriate mass flow control is required not to violate the voltage transient behavior. Appropriate fuel flow manipulation can contribute to moderate the overshoot on the voltage that may appear to the current change. The overshoot on the voltage response resulted from the gradual temperature behavior in the SOFC stack module.

  18. Investigation of InGaP/(In)AlGaAs/GaAs triple-junction top cells for smart stacked multijunction solar cells grown using molecular beam epitaxy

    Science.gov (United States)

    Sugaya, Takeyoshi; Mochizuki, Toru; Makita, Kikuo; Oshima, Ryuji; Matsubara, Koji; Okano, Yoshinobu; Niki, Shigeru

    2015-08-01

    We report high-quality InGaP/(In)AlGaAs/GaAs triple-junction solar cells fabricated using solid-source molecular beam epitaxy (MBE) for the first time. The triple-junction cells can be used as top cells for smart stacked multijunction solar cells. A growth temperature of 480 °C was found to be suitable for an (In)AlGaAs second cell to obtain high-quality tunnel junctions. The properties of AlGaAs solar cells were better than those of InAlGaAs solar cells when a second cell was grown at 480 °C. The high-quality InGaP/AlGaAs/GaAs solar cell had an impressive open-circuit voltage of 3.1 V. This result indicates that high-performance InGaP/AlGaAs/GaAs triple-junction solar cells can be fabricated using solid-source MBE.

  19. A model-based approach for current voltage analyses to quantify degradation and fuel distribution in solid oxide fuel cell stacks

    Science.gov (United States)

    Linder, Markus; Hocker, Thomas; Meier, Christoph; Holzer, Lorenz; Friedrich, K. Andreas; Iwanschitz, Boris; Mai, Andreas; Schuler, J. Andreas

    2015-08-01

    Reliable quantification and thorough interpretation of the degradation of solid oxide fuel cell (SOFC) stacks under real conditions is critical for the improvement of its long-term stability. The degradation behavior is often analyzed based on the evolution of current-voltage (V,I) curves. However, these overall resistances often contain unavoidable fluctuations in the fuel gas amount and composition and hence are difficult to interpret. Studying the evolution of internal repeat unit (RU) resistances is a more appropriate measure to assess stack degradation. RU-resistances follow from EIS-data through subtraction of the gas concentration impedance from the overall steady-state resistance. In this work a model-based approach where a local equilibrium model is used for spatial discretization of a SOFC stack RU running on hydrocarbon mixtures such as natural gas. Since under stack operation, fuel leakages, uneven fuel distribution and varying natural gas composition can influence the performance, they are taken into account by the model. The model extracts the time-dependent internal resistance from (V,I)-data and local species concentration without any fitting parameters. RU resistances can be compared with the sum of the resistances of different components that allows one to make links between laboratory degradation experiments and the behavior of SOFC stacks during operation.

  20. Multi-stacked InAs/GaAs quantum dots grown with different growth modes for quantum dot solar cells

    International Nuclear Information System (INIS)

    We have studied the material properties and device performance of InAs/GaAs quantum dot solar cells (QDSCs) made using three different QD growth modes: Stranski-Krastanov (S-K), quasi-monolayer (QML), and sub-monolayer (SML) growth modes. All QDSCs show an extended external quantum efficiency (EQE) at near infrared wavelengths of 950–1070 nm from the QD absorption. Compared to the S-K and SML QDSCs, the QML QDSC with a higher strain exhibits a poor EQE response in the wavelength region of 300–880 nm due to increased non-radiative recombination. The conversion efficiency of the S-K and SML QDSCs exceeds that of the reference cell (13.4%) without QDs due to an enhanced photocurrent (>16% increase) produced by the silicon doped QD stacks. However, as expected from the EQE of the QML QDSC, the increase of strain-induced crystalline defects greatly degrades the photocurrent and open-circuit voltage, leading to the lowest conversion efficiency (8.9%)

  1. Solid Oxide Cell and Stack Testing, Safety and Quality Assurance (SOCTESQA)

    DEFF Research Database (Denmark)

    Auer, C.; Lang, M.; Couturier, K.;

    2015-01-01

    in the fuel cell (SOFC), in the electrolysis (SOEC) and in the reversible SOFC/SOEC mode are addressed. This covers the wide field of power generation systems, e.g. stationary SOFC µ-CHP, mobile SOFC APU and SOFC/SOEC power-to-gas systems. The paper presents the results which have been achieved so far...

  2. Self-stacked submersible microbial fuel cell (SSMFC) for improved remote power generation from lake sediments

    DEFF Research Database (Denmark)

    Zhang, Yifeng; Angelidaki, Irini

    2012-01-01

    external resistance (≤400 Ω in this study) was applied. In addition, the internal resistance and OCV were the most important parameters for predicting which cell unit had the highest probability to undergo voltage reversal. Use of a capacitor was found to be an effective way to prevent voltage reversal and...

  3. Solid Oxide Cell and Stack Testing, Safety and Quality Assurance (SOCTESQA)

    DEFF Research Database (Denmark)

    Auer, C.; Lang, M.; Couturier, K.;

    2015-01-01

    the fuel cell (SOFC), in the electrolysis (SOEC) and in the reversible SOFC/SOEC mode are addressed. This covers the wide field of power generation systems, e.g. stationary SOFC µ-CHP, mobile SOFC APU and SOFC/SOEC power-to-gas systems. The paper presents the results which have been achieved so far in...

  4. High performance PEM fuel cells - from electrochemistry and material science to engineering development of a multicell stack. Monthly report No. 19

    Energy Technology Data Exchange (ETDEWEB)

    Appleby, A.J.; Inivasan, S.

    1996-07-01

    Several 50 sq cm MEAs were prepared to test the reproducibility of the authors techniques for electrodes and MEAs manufacture. At low current densities the performance of the cells is identical in the range of current densities of practical interest differences of up to 40 mV can be observed. During this month a four cell stack with MEAs provided by BCS Technology was assembled and tested. The MEAs were with electrodes with catalyst loading of 4.5 mg Pt/sq cm, area 50 sq cm, and Nafion(R) 112 membrane. The uncatalyzed gas diffusion substrate for these MEAs was provided by CESHR. The cell stack was operated with dry reactant gases at atmospheric pressure and at 50 deg C continuously for 600 hours at different power levels. The average cell voltage at a current density of 300 mA/sq cm was 0.61 V.

  5. An investigation into the use of additive manufacture for the production of metallic bipolar plates for polymer electrolyte fuel cell stacks

    OpenAIRE

    Dawson, Richard; Patel, Anant; Rennie, Allan; White, Simon

    2015-01-01

    The bipolar plate is of critical importance to the efficient and long lasting operation of a polymer electrolyte fuel cell (PEMFC) stack. With advances in membrane electrode assembly design, greater attention has been focused on the bipolar plate and the important role it plays. Although carbon composite plates are a likely candidate for the mass introduction of fuel cells, it is metallic plates made from thin strip materials which could deliver significant advantages in terms of part cost, e...

  6. Sobol's sensitivity analysis for a fuel cell stack assembly model with the aid of structure-selection techniques

    Science.gov (United States)

    Zhang, Wei; Cho, Chongdu; Piao, Changhao; Choi, Hojoon

    2016-01-01

    This paper presents a novel method for identifying the main parameters affecting the stress distribution of the components used in assembly modeling of proton exchange membrane fuel cell (PEMFC) stack. This method is a combination of an approximation model and Sobol's method, which allows a fast global sensitivity analysis for a set of uncertain parameters using only a limited number of calculations. Seven major parameters, i.e., Young's modulus of the end plate and the membrane electrode assembly (MEA), the contact stiffness between the MEA and bipolar plate (BPP), the X and Y positions of the bolts, the pressure of each bolt, and the thickness of the end plate, are investigated regarding their effect on four metrics, i.e., the maximum stresses of the MEA, BPP, and end plate, and the stress distribution percentage of the MEA. The analysis reveals the individual effects of each parameter and its interactions with the other parameters. The results show that the X position of a bolt has a major influence on the maximum stresses of the BPP and end plate, whereas the thickness of the end plate has the strongest effect on both the maximum stress and the stress distribution percentage of the MEA.

  7. Numerical simulations of a full-scale polymer electrolyte fuel cell with analysing systematic performance in an automotive application

    International Nuclear Information System (INIS)

    Highlights: • A 3-D full-scale fuel cell performance is numerically simulated. • Generated and consumed power in the system is affected by operating condition. • Systematic analysis predicts the net power of conceptual PEFC stack. - Abstract: In fuel cell powered electric vehicles, the net power efficiency is a critical factor in terms of fuel economy and commercialization. Although the fuel cell stack produces enough power to drive the vehicles, the transferred power to the power train could be significantly reduced due to the power consumption to operate the system components of air blower and cooling module. Thus the systematic analysis on the operating condition of the fuel cell stack is essential to predict the net power generation. In this paper numerical simulation is conducted to characterize the fuel cell performance under various operating conditions. Three dimensional and full-scale fuel cell of the active area of 355 cm2 is numerically modelled with 47.3 million grids to capture the complexities of the fluid dynamics, heat transfer and electrochemical reactions. The proposed numerical model requires large computational time and cost, however, it can be powerful to reasonably predict the fuel cell system performance at the early stage of conceptual design without requiring prototypes. Based on the model, it has been shown that the net power is reduced down to 90% of the gross power due to the power consumption of air blower and cooling module

  8. Process simulation of biomass gasification integrated with a solid oxide fuel cell stack

    Science.gov (United States)

    Doherty, Wayne; Reynolds, Anthony; Kennedy, David

    2015-03-01

    Biomass gasification-solid oxide fuel cell (BG-SOFC) combined heat and power (CHP) systems are of major interest in the context of climate change mitigation, energy security and increasing energy efficiency. Aspen Plus is employed to simulate various BG-SOFC CHP systems. The aim of the research work is to investigate the technical feasibility of these systems and to study the influence of important operating parameters and examine integration options. Systems based on dual fluidised bed steam gasification and tubular SOFC technologies are modelled. The cathode recycle and electric heater integration options are not attractive in comparison to the base case anode recycle system. Thermal integration, i.e. using SOFC flue gas as gasifier oxidant, is desirable. Lowering the syngas preheat temperature (prior to SOFC anodes) is highly recommended and is more practical than lowering the cathode air preheat temperature. Results of the parametric study indicate that: steam to carbon ratio and biomass moisture content should be as low as possible; fuel utilisation factor can change the mode of operation of the plant (focus on electricity or heat); high temperature syngas cleaning is very attractive; gasification air preheating is more attractive than gasification steam superheating. High efficiencies are predicted, proving the technical feasibility of BG-SOFC CHP systems.

  9. Effect of cross-flow on PEFC liquid-water distribution: An in-situ high-resolution neutron radiography study

    Science.gov (United States)

    Santamaria, Anthony D.; Becton, Maxwell K.; Cooper, Nathanial J.; Weber, Adam Z.; Park, Jae Wan

    2015-10-01

    Liquid-water management in polymer-electrolyte fuel cells (PEFCs) remains an area of ongoing research. To enhance water removal, certain flow-fields induce cross-flow, or flow through the gas-diffusion layer (GDL) via channel-to-channel pressure differences. While beneficial to water removal, cross-flow comes at the cost of higher pumping pressures and may lead to membrane dehydration and other deleterious issues. This paper examines the impact of cross-flow on component saturation levels as determined through in-plane high-resolution neutron radiography. Various humidities and operating conditions are examined, and the results demonstrate that cell saturation levels correlate strongly with the level of cross-flow rate, and lower GDL saturation levels are found to correlate with an increase in permeability at higher flow rates. Effective water removal is found to occur at channel-to-channel pressure gradients greater than the measured breakthrough pressure of the GDL, evidence that similar liquid-water transport mechanisms exist for under-land area transport as in transverse GDL flow.

  10. Development of a 400 W High Temperature PEM Fuel Cell Power Pack:Fuel Cell Stack Test

    OpenAIRE

    Andreasen, Søren Juhl; Bang, Mads; Korsgaard, Anders; Nielsen, Mads Pagh; Kær, Søren Knudsen

    2006-01-01

    When using pressurized hydrogen to fuel a fuel cell, much space is needed for fuel storage. This is undesirable especially with mobile or portable fuel cell systems, where refuelling also often is inconvenient. Using a reformed liquid carbonhydrate can reduce this fuel volume considerably. Nafion based low temperature PEM (LTPEM) fuel cells are very intolerant to reformate gas because of the presence of CO. PBI based high temperature PEM (HTPEM) fuel cells can operate stable at much higher CO...

  11. 质子交换膜燃料电池电堆的动态热模型及其温度控制%Dynamic Thermal Model and Temperature Control of Proton Exchange Membrane Fuel Cell Stack

    Institute of Scientific and Technical Information of China (English)

    邵庆龙; 卫东; 曹广益; 朱新坚

    2005-01-01

    A dynamic thermal transfer model of a proton exchange membrane fuel cell (PEMFC) stack is developed based on energy conservation in order to reach better temperature control of PEMFC stack. Considering its uncertain parameters and disturbance, we propose a robust adaptive controller based on backstepping algorithm of Lyaponov function. Numerical simulations indicate the validity of the proposed controller.

  12. Nafion and modified-Nafion membranes for polymer electrolyte fuel cells: An overview

    Indian Academy of Sciences (India)

    A K Sahu; S Pitchumani; P Sridhar; A K Shukla

    2009-06-01

    Polymer electrolyte fuel cells (PEFCs) employ membrane electrolytes for proton transport during the cell reaction. The membrane forms a key component of the PEFC and its performance is controlled by several physical parameters, viz. water up-take, ion-exchange capacity, proton conductivity and humidity. The article presents an overview on Nafion membranes highlighting their merits and demerits with efforts on modified-Nafion membranes.

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

    OpenAIRE

    PeiwenLi

    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 ...

  14. Layer-by-layer paper-stacking nanofibrous membranes to deliver adipose-derived stem cells for bone regeneration

    Directory of Open Access Journals (Sweden)

    Wan W

    2015-02-01

    Full Text Available Wenbing Wan,1–3,* Shiwen Zhang,2–4,* Liangpeng Ge,2,3,5 Qingtao Li,1 Xingxing Fang,1 Quan Yuan,4 Wen Zhong,6 Jun Ouyang,1 Malcolm Xing1,2,7 1Department of Anatomy, Guangdong Provincial Medical Biomechanical Key Laboratory, Southern Medical University, Guangzhou, People’s Republic of China; 2Department of Mechanical Engineering, University of Manitoba, Winnipeg, MB, Canada; 3Manitoba Institute of Child Health, Winnipeg, MB, Canada; 4Sichuan University, Chengdu, People’s Republic of China; 5Chongqing Academy of Animal Sciences, Chongqing, People’s Republic of China; 6Department of Textile Sciences, University of Manitoba, Winnipeg, MB, Canada; 7Department of Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, MB, Canada *These authors contributed equally to this work Abstract: Bone tissue engineering through seeding of stem cells in three-dimensional scaffolds has greatly improved bone regeneration technology, which historically has been a constant challenge. In this study, we researched the use of adipose-derived stem cell (ADSC-laden layer-by-layer paper-stacking polycaprolactone/gelatin electrospinning nanofibrous membranes for bone regeneration. Using this novel paper-stacking method makes oxygen distribution, nutrition, and waste transportation work more efficiently. ADSCs can also secrete multiple growth factors required for osteogenesis. After the characterization of ADSC surface markers CD29, CD90, and CD49d using flow cytometry, we seeded ADSCs on the membranes and found cells differentiated, with significant expression of the osteogenic-related proteins osteopontin, osteocalcin, and osteoprotegerin. During 4 weeks in vitro, the ADSCs cultured on the paper-stacking membranes in the osteogenic medium exhibited the highest osteogenic-related gene expressions. In vivo, the paper-stacking scaffolds were implanted into the rat calvarial defects (5 mm diameter, one defect per parietal bone for 12 weeks. Investigating

  15. Evaluation of a 2.5 kWel automotive low temperature PEM fuel cell stack with extended operating temperature range up to 120 °C

    Science.gov (United States)

    Ruiu, Tiziana; Dreizler, Andreas M.; Mitzel, Jens; Gülzow, Erich

    2016-01-01

    Nowadays, the operating temperature of polymer electrolyte membrane fuel cell stacks is typically limited to 80 °C due to water management issues of membrane materials. In the present work, short-term operation at elevated temperatures up to 120 °C and long-term steady-state operation under automotive relevant conditions at 80 °C are examined using a 30-cell stack developed at DLR. The high temperature behavior is investigated by using temperature cycles between 90 and 120 °C without adjustment of the gases dew points, to simulate a short-period temperature increase, possibly caused by an extended power demand and/or limited heat removal. This galvanostatic test demonstrates a fully reversible performance decrease of 21 ± 1% during each thermal cycle. The irreversible degradation rate is about a factor of 6 higher compared to the one determined by the long-term test. The 1200-h test at 80 °C demonstrates linear stack voltage decay with acceptable degradation rate, apart from a malfunction of the air compressor, which results in increased catalyst degradation effects on individual cells. This interpretation is based on an end-of-life characterization, aimed to investigate catalyst, electrode and membrane degradation, by determining hydrogen crossover rates, high frequency resistances, electrochemically active surface areas and catalyst particle sizes.

  16. CZTSe solar cells prepared by electrodeposition of Cu/Sn/Zn stack layer followed by selenization at low Se pressure.

    Science.gov (United States)

    Yao, Liyong; Ao, Jianping; Jeng, Ming-Jer; Bi, Jinlian; Gao, Shoushuai; He, Qing; Zhou, Zhiqiang; Sun, Guozhong; Sun, Yun; Chang, Liann-Be; Chen, Jian-Wun

    2014-01-01

    Cu2ZnSnSe4 (CZTSe) thin films are prepared by the electrodeposition of stack copper/tin/zinc (Cu/Sn/Zn) precursors, followed by selenization with a tin source at a substrate temperature of 530°C. Three selenization processes were performed herein to study the effects of the source of tin on the quality of CZTSe thin films that are formed at low Se pressure. Much elemental Sn is lost from CZTSe thin films during selenization without a source of tin. The loss of Sn from CZTSe thin films in selenization was suppressed herein using a tin source at 400°C (A2) or 530°C (A3). A copper-poor and zinc-rich CZTSe absorber layer with Cu/Sn, Zn/Sn, Cu/(Zn + Sn), and Zn/(Cu + Zn + Sn) with metallic element ratios of 1.86, 1.24, 0.83, and 0.3, respectively, was obtained in a selenization with a tin source at 530°C. The crystallized CZTSe thin film exhibited an increasingly (112)-preferred orientation at higher tin selenide (SnSe x ) partial pressure. The lack of any obvious Mo-Se phase-related diffraction peaks in the X-ray diffraction (XRD) diffraction patterns may have arisen from the low Se pressure in the selenization processes. The scanning electron microscope (SEM) images reveal a compact surface morphology and a moderate grain size. CZTSe solar cells with an efficiency of 4.81% were produced by the low-cost fabrication process that is elucidated herein. PMID:25593559

  17. Energy-saving effect of a residential polymer electrolyte fuel cell cogeneration system combined with a plug-in hybrid electric vehicle

    International Nuclear Information System (INIS)

    Highlights: • Combined use of PEFC-CGS and PHEV is focused on for energy savings. • Optimal operational planning considering daily start–stop operation is modeled. • Charging PHEV with PEFC-CGS increases electric capacity factor of PEFC-CGS. • Combined use has higher energy-saving effect than their separate use. • Combined use synergistically saves energies in residential and transport sectors. - Abstract: The energy-saving effect of a residential polymer electrolyte fuel cell cogeneration system (PEFC-CGS) that adopts a daily start–stop operation with no reverse power flow, combined with a plug-in hybrid electric vehicle (PHEV) is analyzed by optimal operational planning model based on mixed-integer linear programming. This combined use aims to increase the electric capacity factor of the PEFC-CGS by charging the PHEV using the PEFC-CGS output late at night, and targets the application in regions where the reverse power flow from residential cogeneration systems to commercial electric power systems is not permitted, like in Japan. First, the optimal operational planning model that incorporates the daily start–stop operation of the PEFC-CGS is developed. The energy-saving effect of the combined use of the PEFC-CGS and PHEV is then analyzed on the basis of observations of the optimal operation patterns for a 0.75-kWe PEFC-CGS, a simulated energy demand with a sampling time of 5 min, and various daily running distances of the PHEV. The results show that the combined use of the PEFC-CGS and PHEV increases the electric capacity factor and hot water supply rate of the PEFC-CGS and saves more energy in comparison with their separate use in which the PEFC-CGS is used but the PHEV is charged only using purchased electric power. Consequently, this feasibility study reveals that the combined use of the PEFC-CGS and PHEV provides the synergistic effect on energy savings in the residential and transport sectors

  18. Mass and charge transfer on various relevant scales in polymer electrolyte fuel cells[Dissertation 16991

    Energy Technology Data Exchange (ETDEWEB)

    Freunberger, S. A.

    2007-07-01

    This dissertation is concerned with the development, experimental diagnostics and mathematical modelling and simulation of polymer electrolyte fuel cells (PEFC). The central themes throughout this thesis are the closely interlinked phenomena of mass and charge transfer. In the face of developing a PEFC system for vehicle propulsion these phenomena are scrutinized on a broad range of relevant scales. Starting from the material related level of the membrane and the gas diffusion layer (GDL) we turn to length scales, where structural features of the cell additionally come into play. These are the scale of flow channels and ribs, the single cell and the cell stack followed by the cell, stack, and system development for an automotive power train. In Chapter 3 selected fundamental material models and properties, respectively, are explored that are crucial for the mathematical modelling and simulation of PEFC, as needed in some succeeding parts of this work. First, established mathematical models for mass and charge transfer in the membrane are compared within the framework of the membrane electrode assembly (MEA), which represents the electrochemical unit. Second, reliable values for effective diffusivities in the GDLs which are vital for the simulation of gaseous mass transport are measured. Therefore, a method is developed that allows measuring this quantity both as a function of compression and direction as this is a prerequisite of sophisticated more-dimensional numerical PEFC-models. Besides the cross section of the catalyst layer (CL) mass transfer under channels and ribs is considered as a major source of losses in particular under high load operation. As up to now there have been solely non-validated theoretical investigations, in Chapter 4 an experimental method is developed that is for the first time capable of resolving the current density distribution on the this scale. For this, the electron conductors in the cell are considered as 2-dimensional shunt

  19. Low cost CuInSe2 thin films production by stacked elemental layers process for large area fabrication of solar cell application

    International Nuclear Information System (INIS)

    Highlights: ► CuInSe2 (CIS) thin film has deposited by stacked elemental layer technique (SEL). ► CuInSe2 phase have been obtained after annealing at temperature 350 °C. ► The structural, morphology and electrical properties have been obtained. ► The red shift in energy band gap of CIS thin films are found due to annealing. - Abstract: Low cost deposition of large area CuInSe2 (CIS) thin films have been grown on Mo-coated glass substrate by simple and economic stacked elemental layer deposition technique in vacuum. The grown parameters such as concentration of Cu, In and Se elements have been optimized to achieve uniform thin film in vacuum chamber. The as-grown Cu/In/Se stacked layers have been annealed at 200 °C and 350 °C for 1 h in air ambient. The as-grown and annealed films have been further subjected to characterization by X-ray diffraction (XRD), optical absorption, atomic force microscopy (AFM) and I–V measurement techniques. XRD patterns revealed that as-grown Cu/In/Se stacked layers represent amorphous nature while annealed CIS film reproduces nano-polycrystalline nature with chalcopyrite structure. The optical band gap of annealed films increases with respect to air annealing which confirms the reduction of crystallite size. Surface morphology of as-grown Cu/In/Se stacked layers and annealed CIS thin films have been confirmed by AFM images. The electrical measurements show enhancement of conductivity which is useful for solar cell application.

  20. Numerical evaluation of various gas and coolant channel designs for high performance liquid-cooled proton exchange membrane fuel cell stacks

    International Nuclear Information System (INIS)

    A careful design of gas and coolant channel is essential to ensure high performance and durability of proton exchange membrane (PEM) fuel cell stack. The channel design should allow for good thermal, water and gas management whilst keeping low pressure drop. This study evaluates numerically the performance of various gas and coolant channel designs simultaneously, e.g. parallel, serpentine, oblique-fins, coiled, parallel-serpentine and a novel hybrid parallel-serpentine-oblique-fins designs. The stack performance and local distributions of key parameters are investigated with regards to the thermal, water and gas management. The results indicate that the novel hybrid channel design yields the best performance as it constitutes to a lower pumping power and good thermal, water and gas management as compared to conventional channels. Advantages and limitation of the designs are discussed in the light of present numerical results. Finally, potential application and further improvement of the design are highlighted. -- Highlights: ► We evaluate various gas and coolant channel designs in liquid-cooled PEM fuel cell stack. ► The model considers coupled electrochemistry, channel design and cooling effect simultaneously. ► We propose a novel hybrid channel design. ► The novel hybrid channel design yields the best thermal, water and gas management which is beneficial for long term durability. ► The novel hybrid channel design exhibits the best performance.

  1. Mechanical properties of catalyst coated membranes: A powerful indicator of membrane degradation in fuel cells

    OpenAIRE

    Sadeghi Alavijeh, Alireza

    2015-01-01

    Mechanical durability of perfluorosulfonic acid (PFSA) ionomer membranes in polymer electrolyte fuel cells (PEFCs) is investigated in this thesis. This work contributes to a systematic characterization of the decay in mechanical properties of membranes and catalyst coated membranes (CCMs) that are subjected to controlled chemical and/or mechanical degradation mechanisms. During field operation of PEFCs, the membrane is subjected to a combination of chemical and mechanical degradation, resulti...

  2. High performance PEM fuel cells - from electrochemistry and material science to engineering development of a multicell stack. Quarterly report No. 6, April-June 1996

    Energy Technology Data Exchange (ETDEWEB)

    Appleyby, A.J.; Inivasan, S.

    1996-08-16

    To increase the electrocatalytic activity of the air electrode and simultaneously minimize the transport limitations, mixture of a 10 wt.% alloy supported on carbon and a high platinum loading (40 wt.%) on carbon was used as the electrocatalyst. The presence of the alloy electrocatalyst enhances the electrocatalytic activity at low current densities and the presence of the Pt electrocatalyst preserves the open structure of the electrode in this way the performance enhancement is evident over the entire range of current densities. This experiment was repeated with 20 micrometers thick GORE-SELECT (TM) membrane and a similar effect was observed. One 3-cell stack of area 50 sq cm was assembled at BCS Technology, Inc. with MEAs prepared using a Nafion 112 membrane and electrodes containing a Pt loading of 4.5 mg/sq cm. At 2.1 V (0.7 V per cell), the current density was about 0.48 A/sq cm with air and about 0.65 A/sq cm with oxygen. The cells required slight pressurization on the air side of the cell. The performance of the third cell was found to be slightly lower, and required a rapid flow (flushing) of hydrogen periodically. This problem did not result from the quality of the MEAs used, but was probably due to a design problem associated with stacking or the internal manifolding. The stack was tested at CESHR for performance verification and approximately the same performance was observed as that at BCS. However, problems similar to those noted at BCS were also seen at CESHR.

  3. Understanding the effect of reformate gas components and stack component impurities on the performance of PEM fuel cells

    Science.gov (United States)

    Gu, Tao

    The performance can be lost depending on the concentration and type of reformate components. Gas crossover in PEMFCs can also cause performance loss and these effects are also presented. Impurities such as acetone coming from composite stack components and sealants can also deteriorate the performance severely. Electrochemical impedance spectroscopy (EIS) is used as a diagnostic tool to study the impurity poisoning. Reformate contains N2 and CO2 and these components affect performance differently. These effects were quantified using anode overvoltage. Data for anode overvoltage shows that CO2 yields a significant poisoning effect (about 30 mV) on a Pt electrode. Cyclic voltammetry (CV) data showed that CO was produced in-situ from CO2 and H 2 (reverse water gas shift (RWGS) reaction) on both Pt and Pt/Ru electrodes. The coverage of CO achieved by RWGS can reach 5 x 10-7 mol/cm2 on an electrode with 0.4 mg/cm2 Pt under open circuit with normal operating conditions. This work also investigated how pressure, gas composition, and temperature affect the RWGS reaction in a PEMFC for both Pt and Pt/Ru alloy catalysts. The data are shown to be consistent with a kinetic catalytic model and not with an equilibrium model. Data was presented on H2 and O2 crossover in PEMFCs. Electrochemical techniques and mass balance measurements were used to quantify the crossover under typical working conditions. Mixed potential theory was applied to analyze the effect of gas crossover on open circuit voltage (OCV) of PEMFCs. Off-gassing from bipolar plates previously identified styrene, acetone, t-butyl alcohol, and dimethyl succinate as impurities. The effects of those impurities were quantified with both poisoning-recovery transient curves and steady state VI curves before, during, and after poisoning on anode and cathode side respectively. The poisoning effects of them to the anode side are smaller than to the cathode side. Cyclic voltammetry and electrochemical impedance spectroscopy

  4. Experimental investigation of dynamic performance and transient responses of a kW-class PEM fuel cell stack under various load changes

    International Nuclear Information System (INIS)

    The dynamic performance is a very important evaluation index of proton exchange membrane (PEM) fuel cells used for real application, which is mostly related with water, heat and gas management. A commercial PEM fuel cell system of Nexa module is employed to experimentally investigate the dynamic behavior and transient response of a PEM fuel cell stack and reveal involved influential factors. Five groups of dynamic tests are conducted and divided into different stage such as start-up, shut-down, step-up load, regular load variation and irregular load variation. It is observed that the external load changes the current output proportionally and reverses stack voltage accordingly. The purge operation benefits performance recovery and enhancement during a constant load and its time strongly depends on the operational current level. Overshoot and undershoot behaviors are observed during transience. But the current undershoot does not appear due to charge double-layer effect. Additionally, magnitudes of the peaks of the voltage overshoot and undershoot vary at different current levels. The operating temperature responds fast to current load but changes slowly showing an arc-like profile without any overshoot and undershoot events. The air flow rate changes directly following the dynamic load demand. But the increased amount of air flow rate during different step-change is not identical, which depends on the requirement of internal reaction and flooding intensity. The results can be utilized for validation of dynamic fuel cell models, and regarded as reference for effective control and management strategies.

  5. Embedded LTPS flash cells with oxide-nitride-oxynitride stack structure for realization of multi-function mobile flat panel displays

    International Nuclear Information System (INIS)

    In this paper, embedded flash (eFlash) cells were fabricated for realization of multi-functions, such as systems on panels (SOPs) and threshold voltage (VTH) stabilization of flat panel displays (FPDs). Fabrication was via low temperature polycrystalline silicon (LTPS) thin film transistor (TFT) technology and an oxide-nitride-oxynitride (ONOn) stack structure on glass. Poly-silicon (poly-Si) on glass, which was annealed via an excimer laser, has a very rough surface. To fabricate LTPS eFlash cells on glass with a very rough poly-Si surface, plasma-assisted oxynitridation was performed; nitrous oxide (N2O) served as a reactive gas. LTPS eFlash cells have excellent TFT electrical properties, such as VTH, a high On/Off current ratio and a low sub-threshold swing (S). The results demonstrate that eFlash cells fabricated on glass with a rough silicon surface, via an ONOn stack structure, have switching characteristics suitable for data storage, such as a low operating voltage (TH, which exceeds 2.3 V, between the programming and erasing (P/E) states, over a period of 10 years, and the capacity to retain the initial ΔVTH over a period of 105 P/E operations. (fast track communication)

  6. Embedded LTPS flash cells with oxide-nitride-oxynitride stack structure for realization of multi-function mobile flat panel displays

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Sungwook; Kim, Jaehong; Son, Hyukjoo; Jang, Kyungsoo; Cho, Jaehyun; Kim, Kyunghae; Choi, Byoungdeog; Yi, Junsin [School of Information and Communication Engineering, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of)], E-mail: yi@yurim.skku.ac.kr

    2008-09-07

    In this paper, embedded flash (eFlash) cells were fabricated for realization of multi-functions, such as systems on panels (SOPs) and threshold voltage (V{sub TH}) stabilization of flat panel displays (FPDs). Fabrication was via low temperature polycrystalline silicon (LTPS) thin film transistor (TFT) technology and an oxide-nitride-oxynitride (ONOn) stack structure on glass. Poly-silicon (poly-Si) on glass, which was annealed via an excimer laser, has a very rough surface. To fabricate LTPS eFlash cells on glass with a very rough poly-Si surface, plasma-assisted oxynitridation was performed; nitrous oxide (N{sub 2}O) served as a reactive gas. LTPS eFlash cells have excellent TFT electrical properties, such as V{sub TH}, a high On/Off current ratio and a low sub-threshold swing (S). The results demonstrate that eFlash cells fabricated on glass with a rough silicon surface, via an ONOn stack structure, have switching characteristics suitable for data storage, such as a low operating voltage (<{+-}10 V) suitable for mobile FPDs, a threshold voltage window, {delta}V{sub TH}, which exceeds 2.3 V, between the programming and erasing (P/E) states, over a period of 10 years, and the capacity to retain the initial {delta}V{sub TH} over a period of 10{sup 5} P/E operations. (fast track communication)

  7. Influences of Stacking Architectures of TiO2 Nanoparticle Layers on Characteristics of Dye-Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Chih-Hung Tsai

    2013-01-01

    Full Text Available We investigated the influences of stacking architectures of the TiO2 nanoparticle layers on characteristics and performances of DSSCs. TiO2 nanoparticles of different sizes and compositions were characterized for their morphological and optical/scattering properties in thin films. They were used to construct different stacking architectures of the TiO2 nanoparticle layers for use as working electrodes of DSSCs. Characteristics and performances of DSSCs were examined to establish correlation of the stacking architectures of TiO2 nanoparticle layers with characteristics of DSSCs. The results suggest that the three-layer DSSC architecture, with sandwiching a 20 nm TiO2 nanoparticle layer between a 37 nm TiO2 nanoparticle layer and a hundred nm sized TiO2 back scattering/reflection layer, is effective in enhancing DSSC efficiencies. The high-total-transmittance 37 nm TiO2 nanoparticle layer with a larger haze can serve as an effective front scattering layer to scatter a portion of the incident light into larger oblique angles and therefore increase optical paths and absorption.

  8. CZTS absorber layer for thin film solar cells from electrodeposited metallic stacked precursors (Zn/Cu-Sn)

    Science.gov (United States)

    Khalil, M. I.; Atici, O.; Lucotti, A.; Binetti, S.; Le Donne, A.; Magagnin, L.

    2016-08-01

    In the present work, Kesterite-Cu2ZnSnS4 (CZTS) thin films were successfully synthesized from stacked bilayer precursor (Zn/Cu-Sn) through electrodeposition-annealing route. Adherent and homogeneous Cu-poor, Zn-rich stacked metal Cu-Zn-Sn precursors with different compositions were sequentially electrodeposited, in the order of Zn/Cu-Sn onto Mo foil substrates. Subsequently, stacked layers were soft annealed at 350 °C for 20 min in flowing N2 atmosphere in order to improve intermixing of the elements. Then, sulfurization was completed at 585 °C for 15 min in elemental sulfur environment in a quartz tube furnace with N2 atmosphere. Morphological, compositional and structural properties of the films were investigated using SEM, EDS and XRD methods. Raman spectroscopy with two different excitation lines (514.5 and 785 nm), has been carried out on the sulfurized films in order to fully characterize the CZTS phase. Higher excitation wavelength showed more secondary phases, but with low intensities. Glow discharge optical emission spectroscopy (GDOES) has also been performed on films showing well formed Kesterite CZTS along the film thickness as compositions of the elements do not change along the thickness. In order to investigate the electronic structure of the CZTS, Photoluminescence (PL) spectroscopy has been carried out on the films, whose results matched up with the literatures.

  9. Investigations of proton conducting polymers and gas diffusion electrodes in the polymer electrolyte fuel cell

    OpenAIRE

    Gode, Peter

    2005-01-01

    Polymer electrolyte fuel cells (PEFC) convert the chemically bound energy in a fuel, e.g. hydrogen, directly into electricity by an electrochemical process. Examples of future applications are energy conversion such as combined heat and power generation (CHP), zero emission vehicles (ZEV) and consumer electronics. One of the key components in the PEFC is the membrane / electrode assembly (MEA). Both the membrane and the electrodes consist of proton conducting polymers (ionomers). In the membr...

  10. A High-Gain Three-Port Power Converter with Fuel Cell, Battery Sources and Stacked Output for Hybrid Electric Vehicles and DC-Microgrids

    OpenAIRE

    Ching-Ming Lai; Ming-Ji Yang

    2016-01-01

    This paper proposes a novel high-gain three-port power converter with fuel cell (FC), battery sources and stacked output for a hybrid electric vehicle (HEV) connected to a dc-microgrid. In the proposed power converter, the load power can be flexibly distributed between the input sources. Moreover, the charging or discharging of the battery storage device can be controlled effectively using the FC source. The proposed converter has several outputs in series to achieve a high-voltage output, wh...

  11. MCFC燃料电池的非线性建模及基于FGA的模糊控制%Nonlinear modeling of molten carbonate fuel cell stack and FGA-based fuzzy control

    Institute of Scientific and Technical Information of China (English)

    戚志东; 朱新坚; 曹广益

    2006-01-01

    To improve the performance of fuel cells, the operating temperature of molten carbonate fuel cell (MCFC) stack should be controlled within a specified range. In this paper, with the RBF neural network's ability of identifying complex nonlinear systems, a neural network identification model of MCFC stack is developed based on the sampled input-output data. Also, a novel online fuzzy control procedure for the temperature of MCFC stack is developed based on the fuzzy genetic algorithm (FGA). Parameters and rules of the fuzzy controller are optimized. With the neural network identification model, simulation of MCFC stack control is carried out. Validity of the model and the superior performance of the fuzzy controller are demonstrated.

  12. Stacking with stochastic cooling

    International Nuclear Information System (INIS)

    Accumulation of large stacks of antiprotons or ions with the aid of stochastic cooling is more delicate than cooling a constant intensity beam. Basically the difficulty stems from the fact that the optimized gain and the cooling rate are inversely proportional to the number of particles 'seen' by the cooling system. Therefore, to maintain fast stacking, the newly injected batch has to be strongly 'protected' from the Schottky noise of the stack. Vice versa the stack has to be efficiently 'shielded' against the high gain cooling system for the injected beam. In the antiproton accumulators with stacking ratios up to 105 the problem is solved by radial separation of the injection and the stack orbits in a region of large dispersion. An array of several tapered cooling systems with a matched gain profile provides a continuous particle flux towards the high-density stack core. Shielding of the different systems from each other is obtained both through the spatial separation and via the revolution frequencies (filters). In the 'old AA', where the antiproton collection and stacking was done in one single ring, the injected beam was further shielded during cooling by means of a movable shutter. The complexity of these systems is very high. For more modest stacking ratios, one might use azimuthal rather than radial separation of stack and injected beam. Schematically half of the circumference would be used to accept and cool new beam and the remainder to house the stack. Fast gating is then required between the high gain cooling of the injected beam and the low gain stack cooling. RF-gymnastics are used to merge the pre-cooled batch with the stack, to re-create free space for the next injection, and to capture the new batch. This scheme is less demanding for the storage ring lattice, but at the expense of some reduction in stacking rate. The talk reviews the 'radial' separation schemes and also gives some considerations to the 'azimuthal' schemes

  13. 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.)

  14. Horizontal high speed stacking for batteries with prismatic cans

    Energy Technology Data Exchange (ETDEWEB)

    Bartos, Andrew L.; Lin, Yhu-Tin; Turner, III, Raymond D.

    2016-06-14

    A system and method for stacking battery cells or related assembled components. Generally planar, rectangular (prismatic-shaped) battery cells are moved from an as-received generally vertical stacking orientation to a generally horizontal stacking orientation without the need for robotic pick-and-place equipment. The system includes numerous conveyor belts that work in cooperation with one another to deliver, rotate and stack the cells or their affiliated assemblies. The belts are outfitted with components to facilitate the cell transport and rotation. The coordinated movement between the belts and the components promote the orderly transport and rotation of the cells from a substantially vertical stacking orientation into a substantially horizontal stacking orientation. The approach of the present invention helps keep the stacked assemblies stable so that subsequent assembly steps--such as compressing the cells or attaching electrical leads or thermal management components--may proceed with a reduced chance of error.

  15. Optical properties of multi-stacked InGaAs/GaNAs quantum dot solar cell fabricated on GaAs (311)B substrate

    International Nuclear Information System (INIS)

    Quantum dot solar cells (QDSCs) comprised of 10 stacked pairs of strain-compensated InGaAs/GaNAs QD structure have been fabricated by atomic hydrogen-assisted molecular beam epitaxy. A homogeneous and high-density QD array structure with improved in-plane ordering and total density of ∼1012 cm−2 has been achieved on GaAs (311)B grown at 460 °C after stacking. The external quantum efficiency (EQE) of InGaAs/GaNAs QDSC increases in the longer wavelength range due to additive contribution from QD layers inserted in the intrinsic region. The short-circuit current density measured for QDSC is 17.2 mA/cm2 compared to 14.8 mA/cm2 of GaAs reference cell. Further, an increase in EQE due to photocurrent production by 2-step photon absorption has been observed at room temperature though it is still small at around 0.1%.

  16. The nature of excited states in dipolar donor/fullerene complexes for organic solar cells: evolution with the donor stack size.

    Science.gov (United States)

    Shen, Xingxing; Han, Guangchao; Yi, Yuanping

    2016-06-21

    Electronic delocalization at donor/acceptor (D/A) interfaces can play an important role in photocurrent generation for organic solar cells. Here, we have investigated the nature of local excited and interfacial charge transfer (CT) states in model complexes including one to four anti-parallel stacking dipolar donor (DTDCTB) molecules and one fullerene (C60) molecule by means of density functional theory (DFT) and time-dependent DFT (TDDFT). For all the donor-to-acceptor CT states, despite the number of DTDCTB molecules in the complexes, the hole is mainly localized on a single DTDCTB, and moves farther away from C60 for the energy higher level. However, the highest occupied molecular orbitals (HOMOs) and the excitonic states (EX) including the bright and dark EX are delocalized over the whole donor stacks in the complexes. This implies that the formation of ordered DTDCTB arrangements can substantially shorten the exciton diffusion process and facilitate ultrafast charge generation. Interestingly, owing to strong intermolecular Coulomb attraction, the donor-to-donor CT states are situated below the local excited states, but can approach the donor-to-acceptor CT states, indicating a weak role as charge traps. Our work would be helpful for understanding the electronic delocalization effects in organic solar cells. PMID:27241621

  17. Status of MCFC stack technology at IHI

    Energy Technology Data Exchange (ETDEWEB)

    Hosaka, M.; Morita, T.; Matsuyama, T.; Otsubo, M. [Ishikawajima-Harima Heavy Industries Co., Ltd., Tokyo (Japan)

    1996-12-31

    The molten carbonate fuel cell (MCFC) is a promising option for highly efficient power generation possible to enlarge. IHI has been studying parallel flow MCFC stacks with internal manifolds that have a large electrode area of 1m{sup 2}. IHI will make two 250 kW stacks for MW plant, and has begun to make cell components for the plant. To improve the stability of stack, soft corrugated plate used in the separator has been developed, and a way of gathering current from stacks has been studied. The DC output potential of the plant being very high, the design of electric insulation will be very important. A 20 kW short stack test was conducted in 1995 FY to certificate some of the improvements and components of the MW plant. These activities are presented below.

  18. Water recovery and air humidification by condensing the moisture in the outlet gas of a proton exchange membrane fuel cell stack

    International Nuclear Information System (INIS)

    Humidification is one of the most important factors for the operation of proton exchange membrane fuel cell (PEMFC). To maintain the membrane at hydrated state, plenty of water is needed for the state-of-the-art of PEMFC technology, especially in large power applications or long time operation. A condenser is introduced to separate liquid water from the air outlet for air self-sufficient in water of the stack in this study. The condensed temperature at the outlet of the condenser and water recovered amount for air self-sufficient in water are investigated theoretically and experimentally. It is shown that the condensed temperature for air self-sufficient in water is irrelevant with the working current of the stack. When the condenser outlet temperature was above the theoretical line, recovery water was not sufficient for the air humidification. On the contrary, it is sufficient while the temperature was below the theoretical line. It is also shown that when the moisture is sufficiently cooled, large amount water can be separated from the outlet gas, and it increased almost linearly with the time. With the introduction of the condenser, the recovered amount of water can easily satisfy the air self-sufficient in water by condensing the outlet gas to a proper temperature. - Highlights: ► We introduce a condenser to separate liquid water from the air outlet in the stack. ► The mechanism of air self-sufficient in water by condensing gas is presented. ► The condensed temperature and water recovered amount are investigated. ► An experiment is present to validate simplicity and feasibility of the criterion. ► The criterion for air humidification is used for choosing the condenser.

  19. Sizing Stack and Battery of a Fuel Cell Hybrid Distribution Truck Dimensionnement pile et batterie d’un camion hybride à pile à combustible de distribution

    Directory of Open Access Journals (Sweden)

    Tazelaar E.

    2012-08-01

    Full Text Available An existing fuel cell hybrid distribution truck, built for demonstration purposes, is used as a case study to investigate the effect of stack (kW and battery (kW, kWh sizes on the hydrogen consumption of the vehicle. Three driving cycles, the NEDC for Low Power vehicles, CSC and JE05 cycle, define the driving requirements for the vehicle. The Equivalent Consumption Minimization Strategy (ECMS is used for determining the control setpoint for the fuel cell and battery system. It closely approximates the global minimum in fuel consumption, set by Dynamic Programming (DP. Using DP the sizing problem can be solved but ECMS can also be implemented real-time. For the considered vehicle and hardware, all three driving cycles result in optimal sizes for the fuel cell stack of approximately three times the average drive power demand. This demonstrates that sizing the fuel cell stack the average or maximum power demand is not necessarily optimal with respect to a minimum fuel consumption. The battery is sized to deliver the difference between specified stack power and the peak power in the total power demand. The sizing of the battery is dominated by its power handling capabilities. Therefore, a higher maximum C-rate leads to a lower battery weight which in turn leads to a lower hydrogen consumption. The energy storage capacity of the battery only becomes an issue for C-rates over 30. Compared to a Range Extender (RE configuration, where the stack size is comparable to the average power demand and the stack is operated on a constant power level, optimal stack and battery sizes with ECMS as EnergyManagement Strategy significantly reduce the fuel consumption. Compared to a RE strategy, ECMS makes much better use of the combined power available from the fuel cell stack and the battery, resulting in a lower fuel consumption but also enabling a lower battery weight which consequently leads to improved payload capabilities. Un camion hybride, utilisant une pile

  20. Spray deposition of Nafion membranes: Electrode-supported fuel cells

    Science.gov (United States)

    Bayer, Thomas; Pham, Hung Cuong; Sasaki, Kazunari; Lyth, Stephen Matthew

    2016-09-01

    Fuel cells are a key technology for the successful transition towards a hydrogen society. In order to accelerate fuel cell commercialization, improvements in performance are required. Generally, polymer electrolyte membrane fuel cells (PEFCs) are membrane-supported; the electrocatalyst layer is sprayed onto both sides of the membrane, and sandwiched between carbon-based gas diffusion layers (GDLs). In this work we redesign the membrane electrode assembly (MEA) and fabricate an electrode-supported PEFC. First the electrocatalyst layer is sprayed onto the GDL, and then Nafion dispersion is sprayed over the top of this to form a thin membrane. This method has the advantage of simplifying the fabrication process, allowing the fabrication of extremely thin electrolyte layers (down to ∼10 μm in this case), and reducing the amount of ionomer required in the cell. Electrode-supported PEFCs operate at significantly increased power density compared to conventional membrane-supported PEFCs, with a maximum of 581 mW/cm2 at 80 °C (atmospheric pressure, air at the cathode). Impedance spectroscopy confirmed that the origin of the improved performance was an 80% reduction in the membrane resistance due the thinner Nafion layer. This novel fabrication method is a step towards cheaper, thinner, fully printable PEFCs with high power density and efficiency.

  1. A High-Gain Three-Port Power Converter with Fuel Cell, Battery Sources and Stacked Output for Hybrid Electric Vehicles and DC-Microgrids

    Directory of Open Access Journals (Sweden)

    Ching-Ming Lai

    2016-03-01

    Full Text Available This paper proposes a novel high-gain three-port power converter with fuel cell (FC, battery sources and stacked output for a hybrid electric vehicle (HEV connected to a dc-microgrid. In the proposed power converter, the load power can be flexibly distributed between the input sources. Moreover, the charging or discharging of the battery storage device can be controlled effectively using the FC source. The proposed converter has several outputs in series to achieve a high-voltage output, which makes it suitable for interfacing with the HEV and dc-microgrid. On the basis of the charging and discharging states of the battery storage device, two power operation modes are defined. The proposed power converter comprises only one boost inductor integrated with a flyback transformer; the boost and flyback circuit output terminals are stacked to increase the output voltage gain and reduce the voltage stress on the power devices. This paper presents the circuit configuration, operating principle, and steady-state analysis of the proposed converter, and experiments conducted on a laboratory prototype are presented to verify its effectiveness.

  2. Current density and catalyst-coated membrane resistance distribution of hydro-formed metallic bipolar plate fuel cell short stack with 250 cm2 active area

    Science.gov (United States)

    Haase, S.; Moser, M.; Hirschfeld, J. A.; Jozwiak, K.

    2016-01-01

    An automotive fuel cell with an active area of 250 cm2 is investigated in a 4-cell short stack with a current and temperature distribution device next to the bipolar plate with 560 current and 140 temperature segments. The electrical conductivities of the bipolar plate and gas diffusion layer assembly are determined ex-situ with this current scan shunt module. The applied fuel cell consists of bipolar plates constructed of 75-μm-thick, welded stainless-steel foils and a graphitic coating. The electrical conductivities of the bipolar plate and gas diffusion layer assembly are determined ex-situ with this module with a 6% deviation in in-plane conductivity. The current density distribution is evaluated up to 2.4 A cm-2. The entire cell's investigated volumetric power density is 4.7 kW l-1, and its gravimetric power density is 4.3 kW kg-1 at an average cell voltage of 0.5 V. The current density distribution is determined without influencing the operating cell. In addition, the current density distribution in the catalyst-coated membrane and its effective resistivity distribution with a finite volume discretisation of Ohm's law are evaluated. The deviation between the current density distributions in the catalyst-coated membrane and the bipolar plate is determined.

  3. 2010 Manufacturing Readiness Assessment Update to the 2008 Report for Fuel Cell Stacks and Systems for the Backup Power and Materials Handling Equipment Markets

    Energy Technology Data Exchange (ETDEWEB)

    Wheeler, D.; Ulsh, M.

    2012-08-01

    In 2008, the National Renewable Energy Laboratory (NREL), under contract to the US Department of Energy (DOE), conducted a manufacturing readiness assessment (MRA) of fuel cell systems and fuel cell stacks for back-up power and material handling applications (MHE). To facilitate the MRA, manufacturing readiness levels (MRL) were defined that were based on the Technology Readiness Levels previously established by the US Department of Energy (DOE). NREL assessed the extensive existing hierarchy of MRLs developed by Department of Defense (DoD) and other Federal entities, and developed a MRL scale adapted to the needs of the Fuel Cell Technologies Program (FCTP) and to the status of the fuel cell industry. The MRL ranking of a fuel cell manufacturing facility increases as the manufacturing capability transitions from laboratory prototype development through Low Rate Initial Production to Full Rate Production. DOE can use MRLs to address the economic and institutional risks associated with a ramp-up in polymer electrolyte membrane (PEM) fuel cell production. In 2010, NREL updated this assessment, including additional manufacturers, an assessment of market developments since the original report, and a comparison of MRLs between 2008 and 2010.

  4. Non-radiative carrier recombination mechanism in the InGaAs/GaAsP strain-balanced quantum well solar cells with different number of stacks by using a piezoelectric photothermal method

    Science.gov (United States)

    Fukuyama, Atsuhiko; Nakano, Yosuke; Aihara, Taketo; Fujii, Hiroaki; Sugiyama, Masakazu; Nakano, Yoshiaki; Ikari, Tetsuo

    2012-10-01

    To optimize the multiple quantum well (QW) structure of the strain-balanced InGaAs/GaAsP inserted into GaAs p-i-n solar cell, carrier escaping process from QW, carrier radiative and non-radiative recombination processes in QW were investigated by using surface photovoltage (SPV), photoluminescence (PL) and piezoelectric photothermal (PPT) spectroscopies, respectively. Distinctive peaks at 1.19 eV were observed for all spectra below the bandgap of GaAs substrate (1.42 eV) and concluded that the peak was arisen from the excitonic transitions associated between the 1st order subbband in QWs. Although the optical absorption intensity of this transition was proportional to the number of QW stacks, SPV and PPT signals showed saturation above the QW stacks of 20. Band diagram calculation showed that an entire region of 10-stacked QWs was located in the flat band potential area, whereas a part of 20-stacked QWs was placed in an internal electric field. It was then suggested that the potential barrier height of 20-stacked QWs is small than that of 10-stacked QW.

  5. Mastering OpenStack

    CERN Document Server

    Khedher, Omar

    2015-01-01

    This book is intended for system administrators, cloud engineers, and system architects who want to deploy a cloud based on OpenStack in a mid- to large-sized IT infrastructure. If you have a fundamental understanding of cloud computing and OpenStack and want to expand your knowledge, then this book is an excellent checkpoint to move forward.

  6. OpenStack essentials

    CERN Document Server

    Radez, Dan

    2015-01-01

    If you need to get started with OpenStack or want to learn more, then this book is your perfect companion. If you're comfortable with the Linux command line, you'll gain confidence in using OpenStack.

  7. Stacking with stochastic cooling

    Energy Technology Data Exchange (ETDEWEB)

    Caspers, Fritz E-mail: Fritz.Caspers@cern.ch; Moehl, Dieter

    2004-10-11

    Accumulation of large stacks of antiprotons or ions with the aid of stochastic cooling is more delicate than cooling a constant intensity beam. Basically the difficulty stems from the fact that the optimized gain and the cooling rate are inversely proportional to the number of particles 'seen' by the cooling system. Therefore, to maintain fast stacking, the newly injected batch has to be strongly 'protected' from the Schottky noise of the stack. Vice versa the stack has to be efficiently 'shielded' against the high gain cooling system for the injected beam. In the antiproton accumulators with stacking ratios up to 10{sup 5} the problem is solved by radial separation of the injection and the stack orbits in a region of large dispersion. An array of several tapered cooling systems with a matched gain profile provides a continuous particle flux towards the high-density stack core. Shielding of the different systems from each other is obtained both through the spatial separation and via the revolution frequencies (filters). In the 'old AA', where the antiproton collection and stacking was done in one single ring, the injected beam was further shielded during cooling by means of a movable shutter. The complexity of these systems is very high. For more modest stacking ratios, one might use azimuthal rather than radial separation of stack and injected beam. Schematically half of the circumference would be used to accept and cool new beam and the remainder to house the stack. Fast gating is then required between the high gain cooling of the injected beam and the low gain stack cooling. RF-gymnastics are used to merge the pre-cooled batch with the stack, to re-create free space for the next injection, and to capture the new batch. This scheme is less demanding for the storage ring lattice, but at the expense of some reduction in stacking rate. The talk reviews the 'radial' separation schemes and also gives some

  8. Effect of number of stack on the thermal escape and non-radiative and radiative recombinations of photoexcited carriers in strain-balanced InGaAs/GaAsP multiple quantum-well-inserted solar cells

    Science.gov (United States)

    Aihara, Taketo; Fukuyama, Atsuhiko; Suzuki, Hidetoshi; Fujii, Hiromasa; Sugiyama, Masakazu; Nakano, Yoshiaki; Ikari, Tetsuo

    2015-02-01

    Three non-destructive methodologies, namely, surface photovoltage (SPV), photoluminescence, and piezoelectric photothermal (PPT) spectroscopies, were adopted to detect the thermal carrier escape from quantum well (QW) and radiative and non-radiative carrier recombinations, respectively, in strain-balanced InGaAs/GaAsP multiple-quantum-well (MQW)-inserted GaAs p-i-n solar cell structure samples. Although the optical absorbance signal intensity was proportional to the number of QW stack, the signal intensities of the SPV and PPT methods decreased at high number of stack. To explain the temperature dependency of these signal intensities, we proposed a model that considers the three carrier dynamics: the thermal escape from the QW, and the non-radiative and radiative carrier recombinations within the QW. From the fitting procedures, it was estimated that the activation energies of the thermal escape ΔEb a r r and non-radiative recombination ΔEN R were 68 and 29 meV, respectively, for a 30-stacked MQW sample. The estimated ΔEb a r r value agreed well with the difference between the first electron subband and the top of the potential barrier in the conduction band. We found that ΔEb a r r remained constant at approximately 70 meV even with increasing QW stack number. However, the ΔENR value monotonically increased with the increase in the number of stack. Since this implies that non-radiative recombination becomes improbable as the number of stack increases, we found that the radiative recombination probability for electrons photoexcited within the QW increased at a large number of QW stack. Additional processes of escaping and recapturing of carriers at neighboring QW were discussed. As a result, the combination of the three non-destructive methodologies provided us new insights for optimizing the MQW components to further improve the cell performance.

  9. Effect of number of stack on the thermal escape and non-radiative and radiative recombinations of photoexcited carriers in strain-balanced InGaAs/GaAsP multiple quantum-well-inserted solar cells

    International Nuclear Information System (INIS)

    Three non-destructive methodologies, namely, surface photovoltage (SPV), photoluminescence, and piezoelectric photothermal (PPT) spectroscopies, were adopted to detect the thermal carrier escape from quantum well (QW) and radiative and non-radiative carrier recombinations, respectively, in strain-balanced InGaAs/GaAsP multiple-quantum-well (MQW)-inserted GaAs p-i-n solar cell structure samples. Although the optical absorbance signal intensity was proportional to the number of QW stack, the signal intensities of the SPV and PPT methods decreased at high number of stack. To explain the temperature dependency of these signal intensities, we proposed a model that considers the three carrier dynamics: the thermal escape from the QW, and the non-radiative and radiative carrier recombinations within the QW. From the fitting procedures, it was estimated that the activation energies of the thermal escape ΔEbarr and non-radiative recombination ΔENR were 68 and 29 meV, respectively, for a 30-stacked MQW sample. The estimated ΔEbarr value agreed well with the difference between the first electron subband and the top of the potential barrier in the conduction band. We found that ΔEbarr remained constant at approximately 70 meV even with increasing QW stack number. However, the ΔENR value monotonically increased with the increase in the number of stack. Since this implies that non-radiative recombination becomes improbable as the number of stack increases, we found that the radiative recombination probability for electrons photoexcited within the QW increased at a large number of QW stack. Additional processes of escaping and recapturing of carriers at neighboring QW were discussed. As a result, the combination of the three non-destructive methodologies provided us new insights for optimizing the MQW components to further improve the cell performance

  10. Effect of number of stack on the thermal escape and non-radiative and radiative recombinations of photoexcited carriers in strain-balanced InGaAs/GaAsP multiple quantum-well-inserted solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Aihara, Taketo; Fukuyama, Atsuhiko; Ikari, Tetsuo [Faculty of Engineering, University of Miyazaki, 1-1 Gakuen-Kibanadai-Nishi, Miyazaki 889-2192 (Japan); Suzuki, Hidetoshi [Interdisciplinary Research Organization, University of Miyazaki, 1-1 Gakuen-Kibanadai-Nishi, Miyazaki 889-2192 (Japan); Fujii, Hiromasa; Nakano, Yoshiaki [Research Center for Advanced Science and Technology, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032 (Japan); Sugiyama, Masakazu [School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032 (Japan)

    2015-02-28

    Three non-destructive methodologies, namely, surface photovoltage (SPV), photoluminescence, and piezoelectric photothermal (PPT) spectroscopies, were adopted to detect the thermal carrier escape from quantum well (QW) and radiative and non-radiative carrier recombinations, respectively, in strain-balanced InGaAs/GaAsP multiple-quantum-well (MQW)-inserted GaAs p-i-n solar cell structure samples. Although the optical absorbance signal intensity was proportional to the number of QW stack, the signal intensities of the SPV and PPT methods decreased at high number of stack. To explain the temperature dependency of these signal intensities, we proposed a model that considers the three carrier dynamics: the thermal escape from the QW, and the non-radiative and radiative carrier recombinations within the QW. From the fitting procedures, it was estimated that the activation energies of the thermal escape ΔE{sub barr} and non-radiative recombination ΔE{sub NR} were 68 and 29 meV, respectively, for a 30-stacked MQW sample. The estimated ΔE{sub barr} value agreed well with the difference between the first electron subband and the top of the potential barrier in the conduction band. We found that ΔE{sub barr} remained constant at approximately 70 meV even with increasing QW stack number. However, the ΔE{sub NR} value monotonically increased with the increase in the number of stack. Since this implies that non-radiative recombination becomes improbable as the number of stack increases, we found that the radiative recombination probability for electrons photoexcited within the QW increased at a large number of QW stack. Additional processes of escaping and recapturing of carriers at neighboring QW were discussed. As a result, the combination of the three non-destructive methodologies provided us new insights for optimizing the MQW components to further improve the cell performance.

  11. Development of the electric utility dispersed use PAFC stack

    Energy Technology Data Exchange (ETDEWEB)

    Horiuchi, Hiroshi; Kotani, Ikuo [Mitsubishi Electric Co., Kobe (Japan); Morotomi, Isamu [Kansai Electric Power Co., Hyogo (Japan)] [and others

    1996-12-31

    Kansai Electric Power Co. and Mitsubishi Electric Co. have been developing the electric utility dispersed use PAFC stack operated under the ambient pressure. The new cell design have been developed, so that the large scale cell (1 m{sup 2} size) was adopted for the stack. To confirm the performance and the stability of the 1 m{sup 2} scale cell design, the short stack study had been performed.

  12. Development of electrically conductive DLC coated stainless steel separators for polymer electrolyte membrane fuel cell

    International Nuclear Information System (INIS)

    Polymer electrolyte fuel cell (PEFC) as one of generation devices of electrical power is rapidly expanding the market as clean energy instead of petroleum and atomic energy. Residential fuel cell goes into quantity production and introduction of fuel cell for use in automobiles starts in the year 2015 in Japan. Critical subject for making fuel cell expand is how to reduce cost of fuel cell. In this paper we describe about separator plate which domains large ratio of cost in fuel cell stack. In present time, carbon is used in material of residential fuel cell separator. Metal separators are developed in fuel cell for use in automobiles because of need of mechanical strength at first. In order to make fuel cell expand in market, further cost reduction is required. But the metal separator has problem that by using metal separator contact resistance occurred by metal corrosion increases and catalyst layer and membrane degrade. In recent time we found out to protect from corrosion and dissolution of metals by coating the film of porous free conductive DLC with plasma ion implantation and deposition technology that we have developed. Film of electrically conductive DLC was formed with high speed of 13 μm/hr by ICP plasma, and coating cost breakout was performed.

  13. Stacking with Stochastic Cooling

    CERN Document Server

    Caspers, Friedhelm

    2004-01-01

    Accumulation of large stacks of antiprotons or ions with the aid of stochastic cooling is more delicate than cooling a constant intensity beam. Basically the difficulty stems from the fact that the optimized gain and the cooling rate are inversely proportional to the number of particles seen by the cooling system. Therefore, to maintain fast stacking, the newly injected batch has to be strongly protected from the Schottky noise of the stack. Vice versa the stack has to be efficiently shielded against the high gain cooling system for the injected beam. In the antiproton accumulators with stacking ratios up to 105, the problem is solved by radial separation of the injection and the stack orbits in a region of large dispersion. An array of several tapered cooling systems with a matched gain profile provides a continuous particle flux towards the high-density stack core. Shielding of the different systems from each other is obtained both through the spatial separation and via the revolution frequencies (filters)....

  14. Experimental study and modelling of degradation phenomena in HTPEM fuel cell stacks for use in CHP systems

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl

    2009-01-01

    Degradation phenomena in HTPEM fuel cells for use in CHP systems were investigated experimentally and by modelling. It was found that the two main degradation mechanisms in HTPEM fuel cells are carbon corrosion and Pt agglomeration. On basis of this conclusion a mechanistic model, describing the...

  15. Experimental study and modeling of degradation phenomena in HTPEM fuel cell stacks for use in CHP systems

    DEFF Research Database (Denmark)

    Nielsen, Mads Pagh; Andreasen, Søren Juhl; Rasmussen, Peder Lund;

    2009-01-01

    Degradation phenomena in HTPEM fuel cells for use in CHP systems were investigated experimentally and by modeling. It was found that the two main degradation mechanisms in HTPEM fuel cells are carbon corrosion and Pt agglomeration. On basis of this conclusion a mechanistic model, describing the...

  16. A critical assessment of fuel cell technology

    International Nuclear Information System (INIS)

    Cold combustion is a promised technology to mankind since the middle of the last century. The fuel cell may at last become the energy machine of the one to come after a long journey on a road bordered with expectations, successes and disappointments. Ten billion people will need the cell for their well-being. The progress and the state-of-art is assessed by means of figures of merit for performance, normalized to standard conditions, life and variability. State-of-art current densities for multi-kW stacks operating on atmospheric pressure air at 0.74 V cell voltage (50% efficiency, HHV) are estimated to be 150 mA/cm2 for MCFC, 160 mA/cm2 for AFC, 239 mA/cm2 for PEFC and 270 mA/cm2 for SOFC. PAFC gives 260 mA/cm2 at 0.66 V and DMFC 100 mA/cm2 at 0.37 V. Decay rates are about 1%/1000 h for PEFC, PAFC and SOFC compared to 2%/1000 h for AFC and 3%/1000 h for MCFC. Coefficients of variation for cell voltages amount to about 1% for all options, except for MCFC with 3-4%. Improvement of cell performance after 1975 is nil to moderate, except for SOFC with a consistent annual improvement of about 10%. There is room for further development of terrestrial AFCs towards 300-400 mA/cm2 considering the figure 800 mA/cm2 for oxygen AFCs. Life and cost will decide the future of the fuel cell. Prospects are not as good as they could be. The fuel cell community lacks understanding of the basics of fuel processing, as demonstrated by the widespread misbelief ('the CO2 syndrome') that CO2 cannot be removed cost effectively from a hydrogen feed (which is practiced in every NH3 plant around the world). The competition, read the gas turbine, has to be taken very seriously. Emphasis has to be shifted from premature demonstrations to R and D on fundamental problems, which have been around too long. 34 refs

  17. Position of fuel cells in Italy; Situation des piles a combustible en Italie

    Energy Technology Data Exchange (ETDEWEB)

    Janot-Giorgetti, M.; Mottini, N.

    2000-02-01

    The main researches concerning the fuel cells in Italy are the PEFC (Polymer Electrolyte Fuel Cell) and the MCFC (Molten Carbonate Fuel Cell). This reports takes stock of these two techniques in Italy, explaining the running of these two types of cells and relating the Italian situation (development and research program, development programs of fuel cells vehicles). (O.M.)

  18. Laser processing of Al2O3/a-SiCx:H stacks: a feasible solution for the rear surface of high-efficiency p-type c-Si solar cells

    OpenAIRE

    Martín García, Isidro; Ortega Villasclaras, Pablo Rafael; Colina, Monica; Orpella García, Alberto; López, Gema; Alcubilla González, Ramón

    2012-01-01

    We explore the potential of laser processing aluminium oxide (Al2O3)/amorphous silicon carbide (a-SiCx:H) stacks to be used at the rear surface of p-type crystalline silicon (c-Si) solar cells. For this stack, excellent quality surface passivation is measured with effective surface recombination velocities as low as 2 cm/s. By means of an infrared laser, the dielectric film is locally opened. Simultaneously, part of the aluminium in the Al2O3 film is introduced into the c-Si, creating p+ regi...

  19. Annotated Stack Trees

    OpenAIRE

    Hague, Matthew; Penelle, Vincent

    2015-01-01

    Annotated pushdown automata provide an automaton model of higher-order recursion schemes, which may in turn be used to model higher-order programs for the purposes of verification. We study Ground Annotated Stack Tree Rewrite Systems -- a tree rewrite system where each node is labelled by the configuration of an annotated pushdown automaton. This allows the modelling of fork and join constructs in higher-order programs and is a generalisation of higher-order stack trees recently introduced by...

  20. Decoding Stacked Denoising Autoencoders

    OpenAIRE

    Sonoda, Sho; Murata, Noboru

    2016-01-01

    Data representation in a stacked denoising autoencoder is investigated. Decoding is a simple technique for translating a stacked denoising autoencoder into a composition of denoising autoencoders in the ground space. In the infinitesimal limit, a composition of denoising autoencoders is reduced to a continuous denoising autoencoder, which is rich in analytic properties and geometric interpretation. For example, the continuous denoising autoencoder solves the backward heat equation and transpo...

  1. 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.

  2. Cold-start characteristics of polymer electrolyte fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Mishler, Jeff [Los Alamos National Laboratory; Mukundan, Rangachary [Los Alamos National Laboratory; Wang, Yun [UNIV. CAL. RIVERSIDE; Mishler, Jeff [UNIV. CAL. RIVERSIDE; Mukherjee, Partha P [ORNL

    2010-01-01

    In this paper, we investigate the electrochemical reaction kinetics, species transport, and solid water dynamics in a polymer electrolyte fuel cell (PEFC) during cold start. A simplitied analysis is developed to enable the evaluation of the impact of ice volume fraction on cell performance during coldstart. Supporting neutron imaging data are also provided to reveal the real-time water evolution. Temperature-dependent voltage changes due to the reaction kinetics and ohmic loss are also analyzed based on the ionic conductivity of the membrane at subfreezing temperature. The analysis is valuable for the fundamental study of PEFC cold-start.

  3. Interface engineering of layer-by-Layer stacked graphene anodes for high-performance organic solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yu; Tong, Shi Wun; Loh, Kian Ping [Department of Chemistry, National University of Singapore (Singapore); Xu, Xiang Fan; Oezyilmaz, Barbaros [Department of Physics, National University of Singapore (Singapore)

    2011-04-05

    An interface engineering process to deploy graphene film as the anode in poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl C61 butyric acid methyl ester (P3HT:PCBM)-based polymer solar cells is demonstrated. By modifying the interface between the graphene anode and the photoactive layer with MoO{sub 3} and poly(3,4-ethylenedioythiophene):poly(styrenesulfonate) (PEDOT:PSS), the power conversion efficiency of the solar cells reaches {approx}83.3% of control devices that use an indium tin oxide (ITO) anode. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Reconstitution of vesiculated Golgi membranes into stacks of cisternae: requirement of NSF in stack formation

    OpenAIRE

    1995-01-01

    We have developed an in vitro system to study the biochemical events in the fusion of ilimaquinone (IQ) induced vesiculated Golgi membranes (VGMs) into stacks of cisternae. The Golgi complex in intact normal rat kidney cells (NRK) is vesiculated by treatment with IQ. The cells are washed to remove the drug and then permeabilized by a rapid freeze-thaw procedure. VGMs of 60 nm average diameter assemble into stacks of Golgi cisternae by a process that is temperature dependent, requires ATP and ...

  5. Progress of MCFC stack technology at Toshiba

    Energy Technology Data Exchange (ETDEWEB)

    Hori, M.; Hayashi, T.; Shimizu, Y. [Toshiba Corp., Tokyo (Japan)

    1996-12-31

    Toshiba is working on the development of MCFC stack technology; improvement of cell characteristics, and establishment of separator technology. For the cell technology, Toshiba has concentrated on both the restraints of NiO cathode dissolution and electrolyte loss from cells, which are the critical issues to extend cell life in MCFC, and great progress has been made. On the other hand, recognizing that the separator is one of key elements in accomplishing reliable and cost-competitive MCFC stacks, Toshiba has been accelerating the technology establishment and verification of an advanced type separator. A sub-scale stack with such a separator was provided for an electric generating test, and has been operated for more than 10,000 hours. This paper presents several topics obtained through the technical activities in the MCFC field at Toshiba.

  6. High performance PEM fuel cells - from electrochemistry and material science to engineering development of a multicell stack. Interim report

    Energy Technology Data Exchange (ETDEWEB)

    Appleby, A.J.

    1997-03-04

    Under Task 1, it was shown that apparently identical MEAs of 50 Cm2 active area with 1.4 mg/cm2 Pt./C cathodes (20 wt % Pt on C) and 0.3 mg/cm2 Pt/C anodes with 40 microns thickness Gore-Select(TM) PEM material did not give identical performance, except in the Tafel region. This indicates that their overall active surface areas at low current density were identical, and that performance suffered at high current density in the range of interest. In all cases, this is shown as a change in polarization slope in the linear region. The slope of the best of these cells was 0.25 ohms cm2, and that of the worst was ca. 0.36 ohms cm2. In consequence, the performance of the best cell at 0.7 V with humidified gases was 0.44 A/cm2, and that of the worst was 0.3 A/cm2. These are substantially less than 0.7 A/cm2 at 0.7 V, which has been achieved in 5 cm2 cells. This is the fuel cell performance level required to achieve the overall system` performance goals (i.e., 0.7 A/cm2 and 0.7 V on hydrogen and air at atmospheric pressure). The variable polarization slope gives the impression of an internal resistance component, but the internal resistance measured at high frequency is rather low, about 0.12 ohms cm2. Thus, the differences in performance observed are either due to problems with the flow-field, or to dispersion in performance between individual MEAs, which otherwise contain identical components made by identical methods.

  7. A stack-based flex-compressive piezoelectric energy harvesting cell for large quasi-static loads

    Science.gov (United States)

    Wang, Xianfeng; Shi, Zhifei; Wang, Jianjun; Xiang, Hongjun

    2016-05-01

    In this paper, a flex-compressive piezoelectric energy harvesting cell (F-C PEHC) is proposed. This cell has a large load capacity and adjustable force transmission coefficient assembled from replaceable individual components. A statically indeterminate mechanical model for the cell is established and the theoretical force transmission coefficient is derived based on structural mechanics. An inverse correlation between the force transmission coefficient and the relative stiffness of Element 1’s limbs is found. An experimental study is also conducted to verify the theoretical results. Both weakened and enhanced modes are achieved for this experiment. The maximum power output approaches 4.5 mW at 120 kΩ resistive load under a 4 Hz harmonic excitation with 600 N amplitude for the weakened mode, whereas the maximum power output approaches 17.8 mW at 120 kΩ under corresponding load for the enhanced mode. The experimental measurements of output voltages are compared with the theoretical ones in both weakened and enhanced modes. The experimental measurements of open-circuit voltages are slightly smaller for harmonic excitations with amplitudes that vary from 400 N to 800 N and the errors are within 14%. During the experiment, the maximum load approaches 2.8 kN which is quite large but not the ultimate bearing capacity of the present device. The mechanical model and theoretical transmission coefficient can be used in other flex-compressive mode energy transducers.

  8. Time-resolved photoluminescence for evaluating laser-induced damage during dielectric stack ablation in silicon solar cells

    Science.gov (United States)

    Parola, Stéphanie; Blanc-Pélissier, Danièle; Barbos, Corina; Le Coz, Marine; Poulain, Gilles; Lemiti, Mustapha

    2016-06-01

    Selective laser ablation of dielectric layers on crystalline silicon wafers was investigated for solar cell fabrication. Laser processing was performed on Al2O3, and bi-layers Al2O3/SiNX:H with a nanosecond UV laser at various energy densities ranging from 0.4 to 2 J cm-2. Ablation threshold was correlated to the simulated temperature at the interface between the dielectric coatings and the silicon substrate. Laser-induced damage to the silicon substrate was evaluated by time-resolved photoluminescence. The minority carrier lifetime deduced from time-resolved photoluminescence was related to the depth of the heat affected zone in the substrate.

  9. Detailed Electrochemical Characterisation of Large SOFC Stacks

    DEFF Research Database (Denmark)

    Mosbæk, Rasmus Rode; Hjelm, Johan; Barfod, R.;

    2012-01-01

    As solid oxide fuel cell (SOFC) technology is moving closer to a commercial break through, lifetime limiting factors, determination of the limits of safe operation and methods to measure the “state-of-health” of operating cells and stacks are becoming of increasing interest. This requires...

  10. Stacked Cu1.8S nanoplatelets as Counter Electrode for Quantum Dot-Sensitized Solar Cell

    Energy Technology Data Exchange (ETDEWEB)

    Savariraj, Dennyson A.; Rajendrakumar, G.; Selvam, Samayanan; Karthick, S. N.; Balamuralitharan, B.; Kim, Hee-Je; Viswanathan, Kodakkal K.; Vijayakumar, M.; Prabakar, Kandasamy

    2015-11-09

    It is found that electrocatalytic activity of Cu2-xS thin films used in quantum dots sensitized solar cells (QDSSC) as countner electrode (CE) for the reduction of polysulfide electrolyte depends on the the surface active sulfur species and defficiency of Cu. The preferential bonding between Cu2+ and S2- leading to the selective formation of Cu1.8S stacked platelets like morphology is determined by Cetyl Trimethyl Ammonium Bromide surfactant with temperature and crab like Cu-S coordination bond formed dictates the surface area to volume ratio of the Cu1.8S thin films and the electrocatalytic activity. The Cu deficiency enhances the conductivity of the Cu1.8S thin films and exhibits near- infrared localized surface plasmon resonanc due to free carrier intraband absorption and UV-VIS absorption spectra shows excitonic effect due to quantum size effect. When these Cu1.8S thin films were employed as CE in QDSSC, robust photoconversion efficiency of 5.2 % is yielded by the film deposited at 60°C by a sinlge step chemical bath deposition method.

  11. Treatment of colour industry wastewaters with concomitant bioelectricity production in a sequential stacked mono-chamber microbial fuel cells-aerobic system.

    Science.gov (United States)

    Fernando, Eustace; Keshavarz, Taj; Kyazze, Godfrey; Fonseka, Keerthi

    2016-01-01

    The scalability of any microbial fuel cell (MFC)-based system is of vital importance if it is to be utilized for potential field applications. In this study, an integrated MFC-aerobic bioreactor system was investigated for its scalability with the purpose of treating a simulated dye wastewater and industrial wastewaters originated from textile dyebaths and leather tanning. The influent containing real wastewater was fed into the reactor in continuous mode at ambient temperature. Three MFC units were integrated to act in unison as a single module for wastewater treatment and a continuously stirred aerobic bioreactor operating downstream to the MFC module was installed in order to ensure more complete degradation of colouring agents found in the wastewater. Total colour removal in the final effluent exceeded 90% in all experiments where both synthetic (AO-7 containing) and real wastewater were used as the influent feed. The chemical oxygen demand reduction also exceeded 80% in all experiments under the same conditions. The MFC modules connected in parallel configuration allowed obtaining higher current densities than that can be obtained from a single MFC unit. The maximum current density of the MFC stack reached 1150 mA m(-2) when connected in a parallel configuration. The outcome of this work implies that suitably up-scaled MFC-aerobic integrated bioprocesses could be used for colour industry wastewater treatment under industrially relevant conditions with possible prospects of bioelectricity generation. PMID:26212183

  12. On direct and indirect methanol fuel cells for transportation applications

    Energy Technology Data Exchange (ETDEWEB)

    Gottesfield, S.

    1996-04-01

    Research on direct oxidation methanol fuel cells (DMFCs) and polymer electrolyte fuel cells (PEFCs) is discussed. Systems considered for transportation applications are addressed. The use of platinum/ruthenium anode electrocatalysts and platinum cathode electrocatalysts in polymer electrolyte DMFCs has resulted in significant performance enhancements.

  13. On Stack Reconstruction Problem

    Directory of Open Access Journals (Sweden)

    V. D. Аkeliev

    2014-06-01

    Full Text Available The paper describes analytical investigations that study relation of fuel combustion regimes with concentration values of sulphur anhydride in flue gases and acid dew point. Coefficients of convective heat transfer at internal and external surfaces of stacks have been determined in the paper. The paper reveals the possibility to reconstruct stacks while using gas discharging channel made of composite material on the basis of glass-reinforced plastic which permits to reduce thermo-stressed actions on reinforced concrete and increase volume of released gases due to practically two-fold reduction of gas-dynamic pressure losses along the pipe length.

  14. TARN rf stacking system

    International Nuclear Information System (INIS)

    Repetitive rf stacking system for the TARN was developed. The developed system consists of ferrite loaded rf cavity, rf power amplifier, ferrite bias power supply and low level rf electronics. Ferrite material and rf signal source were studied to obtain a high-duty and precise moving rf bucket. Phase lock technic worked at a low intensity beam was also studied. Repetition rate of 50 Hz and final stacking number of 50 were attained at the injection beam energy of 7 MeV/u. (author)

  15. Description and modelling of the solar-hydrogen-biogas-fuel cell system in GlashusEtt

    Science.gov (United States)

    Hedström, L.; Wallmark, C.; Alvfors, P.; Rissanen, M.; Stridh, B.; Ekman, J.

    The need to reduce pollutant emissions and utilise the world's available energy resources more efficiently has led to increased attention towards e.g. fuel cells, but also to other alternative energy solutions. In order to further understand and evaluate the prerequisites for sustainable and energy-saving systems, ABB and Fortum have equipped an environmental information centre, located in Hammarby Sjöstad, Stockholm, Sweden, with an alternative energy system. The system is being used to demonstrate and evaluate how a system based on fuel cells and solar cells can function as a complement to existing electricity and heat production. The stationary energy system is situated on the top level of a three-floor glass building and is open to the public. The alternative energy system consists of a fuel cell system, a photovoltaic (PV) cell array, an electrolyser, hydrogen storage tanks, a biogas burner, dc/ac inverters, heat exchangers and an accumulator tank. The fuel cell system includes a reformer and a polymer electrolyte fuel cell (PEFC) with a maximum rated electrical output of 4 kW el and a maximum thermal output of 6.5 kW th. The fuel cell stack can be operated with reformed biogas, or directly using hydrogen produced by the electrolyser. The cell stack in the electrolyser consists of proton exchange membrane (PEM) cells. To evaluate different automatic control strategies for the system, a simplified dynamic model has been developed in MATLAB Simulink. The model based on measurement data taken from the actual system. The evaluation is based on demand curves, investment costs, electricity prices and irradiation. Evaluation criteria included in the model are electrical and total efficiencies as well as economic parameters.

  16. Structural color-tunable mesoporous bragg stack layers based on graft copolymer self-assembly for high-efficiency solid-state dye-sensitized solar cells

    Science.gov (United States)

    Lee, Chang Soo; Park, Jung Tae; Kim, Jong Hak

    2016-08-01

    We present a facile fabrication route for structural color-tunable mesoporous Bragg stack (BS) layers based on the self-assembly of a cost-effective graft copolymer. The mesoporous BS layers are prepared through the alternating deposition of organized mesoporous-TiO2 (OM-TiO2) and -SiO2 (OM-SiO2) films on the non-conducting side of the counter electrode in dye-sensitized solar cells (DSSCs). The OM layers with controlled porosity, pore size, and refractive index are templated with amphiphilic graft copolymers consisting of poly(vinyl chloride) backbones and poly(oxyethylene methacrylate) side chains, i.e., PVC-g-POEM. The morphology and properties of the structural color-tunable mesoporous BS-functionalized electrodes are characterized using energy filtered transmission electron microscopy (EF-TEM), field emission-scanning electron microscopy (FE-SEM), spectroscopic ellipsometry, and reflectance spectroscopy. The solid-state DSSCs (ssDSSCs) based on a structural color-tunable mesoporous BS counter electrode with a single-component solid electrolyte show an energy conversion efficiency (η) of 7.1%, which is much greater than that of conventional nanocrystalline TiO2-based cells and one of the highest values for N719 dye-based ssDSSCs. The enhancement of η is due to the enhancement of current density (Jsc), attributed to the improved light harvesting properties without considerable decrease in fill factor (FF) or open-circuit voltage (Voc), as confirmed by incident photon-to-electron conversion efficiency (IPCE) and electrochemical impedance spectroscopy (EIS).

  17. Research on high-power metal bipolar plate PEM fuel cell stack%高功率薄型金属双极板PEM燃料电池堆研究

    Institute of Scientific and Technical Information of China (English)

    王东; 王涛; 张伟; 刘向; 张新荣

    2009-01-01

    对高功率车用薄型金属双极板PEM燃料电池堆模块进行测试研究.电池堆模块可在空气压力110~300 kPa条件下工作,表现出良好的高、低压兼容特性.当空气压力300 kPa,电池堆温度70℃,工作电流350 A时,电池堆输出功率可达27.2 kW,其质量和体积比功率分别为777 W/kg和1 015 W/L.单电池电压方差求和计算结果显示,在工作电流50~120A的窗口区间内,单池电压具有相对最好的均匀一致性.在320A(约为1 A/cm~2)放电电流下,使用纯氢/氧气的电池堆输出功率比使用氢/空气高出约10%.空气相对湿度影响测试结果,电池堆较低功率下,空气的相对湿度80%~100%为佳;而当高功率下,空气相对湿度80%为佳.另外,对4单体薄型金属双极板燃料电池短堆进行耐久性测试,累计超过2 900 h,平均单池电压衰减率约为10 mV/1000 h.%In this paper, a thin metal bipolar-plate PEM fuel cell stack module for transportation was developed and validated. It was verified that the stack could be operated in a wide air pressure range from 110-300 kPa by air pressure compatibility test. The stack electrical power reached 27.2 kW operated at 350 A and 70 ℃ with 300 kPa pressurized air. So the mass specific power and volume specific power of the stack approached 777 W/kg and 1 015 W/L respectively. Variance analysis was adopted to evaluate the uniformity of individual cell voltages in the stack. The calculated results showed the stack had a lower cell to cell voltage variation at load current range from 50 A to 120 A. The stack electrical power operated using pure H_2 and O_2 was about 10% higher than using H_2 and air at a current of 320 A, which corresponds to the current density of 1 A/cm~2. In addition, durability test on the stack was performed for more than 2 900 h with a 4-cell short stack at a given test condition of temperature, pressure and stoichiometry by starting at 100 A. The durability test results indicated that the

  18. Performance enhancement of polymer electrolyte fuel cells by combining liquid removal mechanisms of a gas diffusion layer with wettability distribution and a gas channel with microgrooves

    Science.gov (United States)

    Utaka, Yoshio; Koresawa, Ryo

    2016-08-01

    Although polymer electrolyte fuel cells (PEFCs) are commercially available, there are still many problems that need to be addressed to improve their performance and increase their usage. At a high current density, generated water accumulates in the gas diffusion layer and in the gas channels of the cathode. This excess water obstructs oxygen transport, and as a result, cell performance is greatly reduced. To improve the cell performance, the effective removal of the generated water and the promotion of oxygen diffusion in the gas diffusion layer (GDL) are necessary. In this study, two functions proposed in previous reports were combined and applied to a PEFC: a hybrid GDL to form an oxygen diffusion path using a wettability distribution and a gas separator with microgrooves to enhance liquid removal. For a PEFC with a hybrid GDL and a gas separator with microgrooves, the concentration overvoltage of the PEFC was reduced, and the current density limit and maximum power density were increased compared with a conventional PEFC. Moreover, the stability of the cell voltage was markedly improved.

  19. Metsäsertifioinnin ekologisten kriteerien aiheuttamat tulonmenetykset metsänomistajalle : PEFC:n ja FSC:n vertailu esimerkkitilojen avulla

    OpenAIRE

    Rantanen, Henna

    2014-01-01

    Opinnäytetyössä tarkasteltiin PEFC- ja FSC-sertifioinnin aiheuttamia tulonmenetyksiä metsänomistajalle ekologisten kriteereiden osalta. Työn tilaajana toimi Länsi-Suomen Metsänomistajaliitto, joka valitsi työssä käytettävät kuusi esimerkkitilaa. Vertailukohtana toimi maksimihakkuumäärän mukainen puukauppatulo, kestävän hakkuumäärän mukainen puukauppatulo ja metsäsuunnitelman mukainen puukauppatulo. Hakkuutulot on laskettu seuraavalle 10-vuotiskaudelle. Suurimmat tulonmenetyksiä aiheuttava...

  20. Learning SaltStack

    CERN Document Server

    Myers, Colton

    2015-01-01

    If you are a system administrator who manages multiple servers, then you know how difficult it is to keep your infrastructure in line. If you've been searching for an easier way, this book is for you. No prior experience with SaltStack is required.

  1. Deformations of algebroid stacks

    DEFF Research Database (Denmark)

    Bressler, Paul; Gorokhovsky, Alexander; Nest, Ryszard; Tsygan, Boris

    2011-01-01

    In this paper we consider deformations of an algebroid stack on an étale groupoid. We construct a differential graded Lie algebra (DGLA) which controls this deformation theory. In the case when the algebroid is a twisted form of functions we show that this DGLA is quasiisomorphic to the twist of ...

  2. po_stack_movie

    DEFF Research Database (Denmark)

    2009-01-01

    po_stack® er et reolsystem, hvis enkle elementer giver stor flexibilitet, variation og skulpturel virkning. Elementerne stables og forskydes frit, så reolens rum kan vendes til begge sider, være åbne eller lukkede og farvekombineres ubegrænset. Reolen kan let ombygges, udvides eller opdeles, når ...

  3. Wolfram technology stack

    CERN Multimedia

    2013-01-01

    Stephen Wolfram gives a personal account of his vision for the "Wolfram technology stack" and how it developed, starting with his work in particle physics. The talk was presented at the 2013 ROOT Users' Meeting and followed a talk, earlier in the day, on "Mathematica with ROOT".

  4. Stacking with No Planarity?

    Science.gov (United States)

    Gunaydin, Hakan; Bartberger, Michael D

    2016-04-14

    This viewpoint describes the results obtained from matched molecular pair analyses and quantum mechanics calculations that show unsaturated rings found in drug-like molecules may be replaced with their saturated counterparts without losing potency even if they are engaged in stacking interactions with the side chains of aromatic residues. PMID:27096037

  5. Heat and water transport in a polymer electrolyte fuel cell electrode

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, Partha P [Los Alamos National Laboratory; Mukundan, Rangachary [Los Alamos National Laboratory; Borup, Rod L [Los Alamos National Laboratory; Ranjan, Devesh [TEXAS A& M UNIV

    2010-01-01

    In the present scenario of a global initiative toward a sustainable energy future, the polymer electrolyte fuel cell (PEFC) has emerged as one of the most promising alternative energy conversion devices for various applications. Despite tremendous progress in recent years, a pivotal performance limitation in the PEFC comes from liquid water transport and the resulting flooding phenomena. Liquid water blocks the open pore space in the electrode and the fibrous diffusion layer leading to hindered oxygen transport. The electrode is also the only component in the entire PEFC sandwich which produces waste heat from the electrochemical reaction. The cathode electrode, being the host to several competing transport mechanisms, plays a crucial role in the overall PEFC performance limitation. In this work, an electrode model is presented in order to elucidate the coupled heat and water transport mechanisms. Two scenarios are specifically considered: (1) conventional, Nafion{reg_sign} impregnated, three-phase electrode with the hydrated polymeric membrane phase as the conveyer of protons where local electro-neutrality prevails; and (2) ultra-thin, two-phase, nano-structured electrode without the presence of ionomeric phase where charge accumulation due to electro-statics in the vicinity of the membrane-CL interface becomes important. The electrode model includes a physical description of heat and water balance along with electrochemical performance analysis in order to study the influence of electro-statics/electro-migration and phase change on the PEFC electrode performance.

  6. NOx-conversion on Porous LSF15-CGO10 Cell Stacks with KNO3 or K2O Impregnation

    DEFF Research Database (Denmark)

    Traulsen, Marie Lund; Bræstrup, Frantz Radzik; Kammer Hansen, Kent

    2012-01-01

    In the present work, it was investigated how addition of KNO3 or K2O affected the NOx conversion on LSF15–CGO10 (La0.85Sr15FeO3–Ce0.9Gd0.1O1.95) composite electrodes during polarization. The LSF15–CGO10 electrodes were part of a porous 11-layer cell stack with alternating layers of LSF15–CGO10...... observed during polarization, but the impregnations altered the conversion between NO and NO2 on the electrodes. Both impregnations caused increased degradation of the cell stack, but the exact cause of the degradation has not been identified yet....

  7. Composite Nafion membranes based on PWA-Zirconia for PEFCs operating at medium temperature

    Energy Technology Data Exchange (ETDEWEB)

    Carbone, A.; Sacca, A.; Passalacqua, E. [CNR-ITAE, Messina (Italy); Casciola, M.; Cavalaglio, S.; Costantino, U. [University of Perugia, Chemistry Department, Perugia (Italy); Ornelas, R.; Fodale, I. [Nuvera Fuel Cells Europe Srl, Milano (Italy)

    2004-01-01

    Nafion membranes based on phosphotungstic acid (PWA) were immobilized as Zr(IV) phospho-tungstate, and the solid obtained was used as a filler to recast Nafion. Composite membranes, containing different filler percentages were prepared and characterized for their ion exchange capacity, water uptake and proton conductivity. Results showed that the hydrophilic characteristics of the composite membranes was higher than that of pure Nafion membranes, allowing an increase in fuel cell efficiency above 80 degrees C. This ability to work at temperatures higher than classical proton exchange membranes made it possible to reduce the carbon monoxide poisoning and to feed the cell with processed hydrogen, in effect to extend the operating temperature range of the fuel cell to 120 degrees C. As a general rule, Nafion-based membranes give the best performance at 100 degrees C, yielding a very high power density when compared with results at 120 degrees C. When the synthetic fuel, containing 10 parts per million of carbon monoxide was fed at the platinum-based anode, a power density of 350 mW/sq cm was recorded, which is 70 mW/sq cm lower than pure hydrogen. 22 refs., 3 tabs., 2 figs.

  8. Waste to energy: Exploitation of biogas from organic waste in a 500 Wel solid oxide fuel cell (SOFC) stack

    International Nuclear Information System (INIS)

    Organic waste collection from local municipal areas with subsequent energy valorization through CHP systems allows for a reduction of waste disposal in landfill. Pollutant emissions released into the atmosphere are also reduced in this way. Solid oxide fuel cell (SOFC) systems are among the most promising energy generators, due to their high electrical efficiency (>50%), even at part loads. In this work, the local organic fraction of municipal solid waste has been digested in a dry anaerobic digester pilot plant and a biogas stream with methane and carbon dioxide concentrations ranging from 60–70 and 30–40% vol., respectively, has been obtained. Trace compounds from the digester and after the gas clean-up section have been detected by means of a new technique that exploits the protonation reactions between the volatile compounds of interest and the ion source. Sulfur, chlorine and siloxane compounds have been removed from as-produced biogas through the use of commercial sorbent materials, such as activated carbons impregnated with metals. A buffer gas cylinder tank has been inserted downstream from the filtering section to compensate for the biogas fluctuations from the digester. The technical feasibility of the dry anaerobic process of the organic fraction of municipal solid waste, coupled with a gas cleaning section and an SOFC system, has been proved experimentally with an electrical efficiency ranging from 32 to 36% for 400 h under POx conditions. - Highlights: • Biogas trace compounds were monitored with the innovative PTR-MS technique. • VOCs removal of a filter section was investigated with PTR-MS. • The treated biogas fed a SOFC stack with stable performance for more than 400 h

  9. OpenStack cloud security

    CERN Document Server

    Locati, Fabio Alessandro

    2015-01-01

    If you are an OpenStack administrator or developer, or wish to build solutions to protect your OpenStack environment, then this book is for you. Experience of Linux administration and familiarity with different OpenStack components is assumed.

  10. Energy Expenditure of Sport Stacking

    Science.gov (United States)

    Murray, Steven R.; Udermann, Brian E.; Reineke, David M.; Battista, Rebecca A.

    2009-01-01

    Sport stacking is an activity taught in many physical education programs. The activity, although very popular, has been studied minimally, and the energy expenditure for sport stacking is unknown. Therefore, the purposes of this study were to determine the energy expenditure of sport stacking in elementary school children and to compare that value…

  11. Analytic stacks and hyperbolicity

    OpenAIRE

    Borghesi, Simone; Tomassini, Giuseppe

    2012-01-01

    The classical Brody's theorem asserts the equivalence between two notions of hyperbolicity for compact complex spaces, one named after Kobayashi and one expressed in terms of lack of non constant holomorphic entire functions (compactness is only used to prove the harder implication). We extend this theorem to Deligne-Mumford analytic stacks, by first providing definitions of what we think of Kobayashi and Brody hyperbolicity for such objects and then proving the equivalence of these concepts ...

  12. Development of on-site PAFC stacks

    Energy Technology Data Exchange (ETDEWEB)

    Hotta, K.; Matsumoto, Y. [Kansai Electric Power Co., Amagasaki (Japan); Horiuchi, H.; Ohtani, T. [Mitsubishi Electric Corp., Kobe (Japan)

    1996-12-31

    PAFC (Phosphoric Acid Fuel Cell) has been researched for commercial use and demonstration plants have been installed in various sites. However, PAFC don`t have a enough stability yet, so more research and development must be required in the future. Especially, cell stack needs a proper state of three phases (liquid, gas and solid) interface. It is very difficult technology to keep this condition for a long time. In the small size cell with the electrode area of 100 cm{sup 2}, gas flow and temperature distributions show uniformity. But in the large size cell with the electrode area of 4000 cm{sup 2}, the temperature distributions show non-uniformity. These distributions would cause to be shorten the cell life. Because these distributions make hot-spot and gas poverty in limited parts. So we inserted thermocouples in short-stack for measuring three-dimensional temperature distributions and observed effects of current density and gas utilization on temperature.

  13. Toric Stacks II: Intrinsic Characterization of Toric Stacks

    CERN Document Server

    Geraschenko, Anton

    2011-01-01

    The purpose of this paper and its prequel (Toric Stacks I) is to introduce and develop a theory of toric stacks which encompasses and extends the notions of toric stacks defined in [Laf02, BCS05, FMN09, Iwa09, Sat09, Tyo10], as well as classical toric varieties. While the focus of the prequel is on how to work with toric stacks, the focus of this paper is how to show a stack is toric. For toric varieties, a classical result says that any normal variety with an action of a dense open torus arises from a fan. In [FMN09, Theorem 7.24], it is shown that a smooth separated DM stack with an action of a dense open stacky torus arises from a stacky fan. In the same spirit, the main result of this paper is that any Artin stack with an action of a dense open torus arises from a stacky fan under reasonable hypotheses.

  14. Radiation Effects on Platinum Nanostructured Electrocatalysts for Polymer Electrolyte Fuel Cells

    Science.gov (United States)

    Cemmi, A.; Paoletti, C.; Pozio, A.; Baccaro, S.; Giorgi, L.; Serra, E.

    2008-06-01

    Polymer Electrolyte Fuel Cells (PEFCs) offer low weight and high power density and are being considered for automotive and stationary power production besides space and electronic applications. In this work, gamma radiation effects on carbon materials (carbon powder and multiwalled carbon nanotubes) used as substrates in PEFCs electrodes, were studied. The enhancing of free radicals formation (especially on carbon powder) was observed and studied by EPR spectroscopy. This evidence leads to a significant activation of carbon materials because paramagnetic sites represent the preferential position for platinum electrocatalyst nucleation. Galvanostatic techniques were applied to deposits platinum nanoparticles on carbon substrates while FEG-SEM characterization and cyclic voltammetry (CV) were carried out to study the morphology and the electrochemical performances of PEFCs electrodes.

  15. Policies for dynamic stack composition

    OpenAIRE

    Sora, Ioana; Michiels, Sam; Matthijs, Frank

    2001-01-01

    Currently, protocol stacks operate in various contexts and it is therefore not possible to know the required properties of a stack (both functional and non-functional) in advance. The stack has to be dynamically built up from components, based on the requirements and the momentary situation. The first step in building the stack is to determine the component types to be used and the stack architecture that has to define the way building blocks are connected. In this document we report on how t...

  16. 全钒液流电池10kW单元电堆性能研究%Performance of 10kW cell stack of vanadium redox flow battery

    Institute of Scientific and Technical Information of China (English)

    陈伟; 孟凡明; 李晓兵; 刘效疆; 马海波

    2013-01-01

    详细研究了全钒液流电池10kW单元电堆的功率输出特性和单体电压一致性及不同充放电电流密度与库仑效率和能量效率的关系.研究了电堆长期运行时,库仑效率、能量效率及电压平台的变化.%The power output characteristics and single voltage consistency of 10 kW cell stack of vanadium redox flow battery,as well as the coulombic efficiency and energy efficiency for different charge and discharge current density were studied.The variety of coulombic and energy efficiency and voltage platform of the stack was researched in a long-term operation.

  17. Fungal melanins differ in planar stacking distances.

    Directory of Open Access Journals (Sweden)

    Arturo Casadevall

    Full Text Available Melanins are notoriously difficult to study because they are amorphous, insoluble and often associated with other biological materials. Consequently, there is a dearth of structural techniques to study this enigmatic pigment. Current models of melanin structure envision the stacking of planar structures. X ray diffraction has historically been used to deduce stacking parameters. In this study we used X ray diffraction to analyze melanins derived from Cryptococcus neoformans, Aspergillus niger, Wangiella dermatitides and Coprinus comatus. Analysis of melanin in melanized C. neoformans encapsulated cells was precluded by the fortuitous finding that the capsular polysaccharide had a diffraction spectrum that was similar to that of isolated melanin. The capsular polysaccharide spectrum was dominated by a broad non-Bragg feature consistent with origin from a repeating structural motif that may arise from inter-molecular interactions and/or possibly gel organization. Hence, we isolated melanin from each fungal species and compared diffraction parameters. The results show that the inferred stacking distances of fungal melanins differ from that reported for synthetic melanin and neuromelanin, occupying intermediate position between these other melanins. These results suggest that all melanins have a fundamental diffracting unit composed of planar graphitic assemblies that can differ in stacking distance. The stacking peak appears to be a distinguishing universal feature of melanins that may be of use in characterizing these enigmatic pigments.

  18. Polymer Materials for Fuel Cell Membranes :Sulfonated Poly(ether sulfone) for Universal Fuel Cell Operations

    Institute of Scientific and Technical Information of China (English)

    Hyoung-Juhn Kim

    2005-01-01

    @@ 1Introduction Polymer electrolyte fuel cells (PEFCs) have been spotlighted because they are clean and highly efficient power generation system. Proton exchange membrane fuel cells (PEMFCs), which use reformate gases or pure H2 for a fuel, have been employed for automotives and residential usages. Also, liquid-feed fuel cells such as direct methanol fuel cell (DMFC) and direct formic acid fuel cell (DFAFC) were studied for portable power generation.

  19. Die-stacking architecture

    CERN Document Server

    Xie, Yuan

    2015-01-01

    The emerging three-dimensional (3D) chip architectures, with their intrinsic capability of reducing the wire length, promise attractive solutions to reduce the delay of interconnects in future microprocessors. 3D memory stacking enables much higher memory bandwidth for future chip-multiprocessor design, mitigating the ""memory wall"" problem. In addition, heterogenous integration enabled by 3D technology can also result in innovative designs for future microprocessors. This book first provides a brief introduction to this emerging technology, and then presents a variety of approaches to design

  20. Technology stacks and frameworks for full-stack application development

    OpenAIRE

    Ušaj, Erik

    2016-01-01

    This work aims providing a comprehensive overview and analysis of current JavaScript (JS) technology stacks and frameworks for full-stack application development: from web clients, mobile and desktop applications to server applications and cloud-connected services. Analysis shall focus on MEAN technology stack and frameworks such as Meteor which also tries to leverage mobile app development using Apache Cordova framework. We will include an overview of available JS build tools for desktop app...

  1. Optimization of a fuel cell system based on empirical data of a PEM fuel cell stack and the generalized electrochemical model. Paper no. IGEC-1-126

    International Nuclear Information System (INIS)

    A fuel cell system model is implemented in MATLAB in order to optimize the system operating conditions. The implemented fuel cell model is a modified version of the semi-empirical model introduced by researchers at the Royal Military College of Canada. In addition, in order to model the whole fuel cell system, heat transfer and gas flow considerations and the associated Balance of Plant (BOP) components are incorporated into the model. System design optimizations are carried out using three different methods, including the sequential quadratic programming (SQP) local optimization algorithm and simulated annealing (SA) and genetic algorithm (GA) global optimization algorithms. Using the operating conditions of the fuel cell system as the design variables, the net output power of the system is optimized. The three methods are used in order to gain some insight into the nature of the objective function and the performance of the different algorithms. The optimization results show a good agreement and provide useful information on the design optimization problem. This study prepares us for more complex modeling and system optimization research. (author)

  2. Asymmetric Flexible Supercapacitor Stack

    Directory of Open Access Journals (Sweden)

    Leela Mohana Reddy A

    2008-01-01

    Full Text Available AbstractElectrical double layer supercapacitor is very significant in the field of electrical energy storage which can be the solution for the current revolution in the electronic devices like mobile phones, camera flashes which needs flexible and miniaturized energy storage device with all non-aqueous components. The multiwalled carbon nanotubes (MWNTs have been synthesized by catalytic chemical vapor deposition technique over hydrogen decrepitated Mischmetal (Mm based AB3alloy hydride. The polymer dispersed MWNTs have been obtained by insitu polymerization and the metal oxide/MWNTs were synthesized by sol-gel method. Morphological characterizations of polymer dispersed MWNTs have been carried out using scanning electron microscopy (SEM, transmission electron microscopy (TEM and HRTEM. An assymetric double supercapacitor stack has been fabricated using polymer/MWNTs and metal oxide/MWNTs coated over flexible carbon fabric as electrodes and nafion®membrane as a solid electrolyte. Electrochemical performance of the supercapacitor stack has been investigated using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy.

  3. Stacked Extreme Learning Machines.

    Science.gov (United States)

    Zhou, Hongming; Huang, Guang-Bin; Lin, Zhiping; Wang, Han; Soh, Yeng Chai

    2015-09-01

    Extreme learning machine (ELM) has recently attracted many researchers' interest due to its very fast learning speed, good generalization ability, and ease of implementation. It provides a unified solution that can be used directly to solve regression, binary, and multiclass classification problems. In this paper, we propose a stacked ELMs (S-ELMs) that is specially designed for solving large and complex data problems. The S-ELMs divides a single large ELM network into multiple stacked small ELMs which are serially connected. The S-ELMs can approximate a very large ELM network with small memory requirement. To further improve the testing accuracy on big data problems, the ELM autoencoder can be implemented during each iteration of the S-ELMs algorithm. The simulation results show that the S-ELMs even with random hidden nodes can achieve similar testing accuracy to support vector machine (SVM) while having low memory requirements. With the help of ELM autoencoder, the S-ELMs can achieve much better testing accuracy than SVM and slightly better accuracy than deep belief network (DBN) with much faster training speed. PMID:25361517

  4. Stacking in the Fermilab doubler

    Energy Technology Data Exchange (ETDEWEB)

    Month, M.

    1976-07-14

    The feasibility of stacking beam in a storage ring by the phase displacement technique, i.e. by the accumulation of momentum strips, is determined by a complicated interplay of many factors. Some of these factors are discussed, especially as they relate to stacking beam in the Fermilab doubler ring, but no attempt is made to present a consistent solution. An arbitrary division is made into five subject categories connected with the stacking process: (1) momentum dilution, that is, the dilution of the longitudinal phase space area; (2) rebunching the stack for acceleration; (3) the physical aperture used to create a stack of given current; (4) beam loss during stacking in a superconducting environment; and (5) field errors due to random errors in the placement and support of the superconducting coils, including the amplification of the field errors for orbits displaced from the magnet center. The basic theory is given and applied using doubler parameters.

  5. Beam stacking experiments at TARN

    International Nuclear Information System (INIS)

    After the first success of beam injection in TARN, August of 1979, beam experiments have been performed in succession to show the overall stacking number of around -- 300 turns, 15 RF stackings and 20 multi-turns. These results are in the close agreements with the theoretical calculations and we are now convinced that the stacking method used at TARN is quite useful for the accelerators of protons and heavy ions. (author)

  6. Duality for commutative group stacks

    OpenAIRE

    Brochard, Sylvain

    2014-01-01

    We study in this article the dual of a (strictly) commutative group stack $G$ and give some applications. Using the Picard functor and the Picard stack of $G$, we first give some sufficient conditions for $G$ to be dualizable. Then, for an algebraic stack $X$ with suitable assumptions, we define an Albanese morphism $a_X : X\\to A^1(X)$ where $A^1(X)$ is a torsor under the dual commutative group stack $A^0(X)$ of $Pic_{X/S}$. We prove that $a_X$ satisfies a natural universal property. We give ...

  7. The LSST Software Stack

    Science.gov (United States)

    Jenness, Timothy; LSST Data Management Team

    2016-01-01

    The Large Synoptic Survey Telescope (LSST) is an 8-m optical ground-based telescope being constructed on Cerro Pachon in Chile. LSST will survey half the sky every few nights in six optical bands. The data will be transferred to the data center in North America and within 60 seconds it will be reduced using difference imaging and an alert list be generated for the community. Additionally, annual data releases will be constructed from all the data during the 10-year mission, producing catalogs and deep co-added images with unprecedented time resolution for such a large region of sky. In the paper we present the current status of the LSST stack including the data processing components, Qserv database and data visualization software, describe how to obtain it, and provide a summary of the development road map.

  8. Instant BlueStacks

    CERN Document Server

    Judge, Gary

    2013-01-01

    Get to grips with a new technology, understand what it is and what it can do for you, and then get to work with the most important features and tasks. A fast-paced, example-based approach guide for learning BlueStacks.This book is for anyone with a Mac or PC who wants to run Android apps on their computer. Whether you want to play games that are freely available for Android but not your computer, or you want to try apps before you install them on a physical device or use it as a development tool, this book will show you how. No previous experience is needed as this is written in plain English

  9. Spherical Torus Center Stack Design

    Energy Technology Data Exchange (ETDEWEB)

    C. Neumeyer; P. Heitzenroeder; C. Kessel; M. Ono; M. Peng; J. Schmidt; R. Woolley; I. Zatz

    2002-01-18

    The low aspect ratio spherical torus (ST) configuration requires that the center stack design be optimized within a limited available space, using materials within their established allowables. This paper presents center stack design methods developed by the National Spherical Torus Experiment (NSTX) Project Team during the initial design of NSTX, and more recently for studies of a possible next-step ST (NSST) device.

  10. Current-Distribution Measurement in Polymer Electrolyte Water Electrolysis Equipment and Polymer Electrolyte Fuel Cell Using NMR Sensor

    Science.gov (United States)

    Yokouchi, Yasuo; Ogawa, Kuniyasu; Haishi, Tomoyuki; Ito, Kohei

    In a polymer electrolyte fuel cell (PEFC), the current density through the polymer electrolyte membrane (PEM) is distributed along the electrode on the membrane electrode assembly (MEA). To increase the electric power density of a PEFC, it is necessary to locate local decreases in current density where electric power generation decreases due to a lack of hydrogen, flooding, and so on. Therefore, achieving a higher current density in a PEFC requires monitoring the local current density. We developed a new method to estimate the spatial distribution of current flowing through the MEA in a polymer electrolyte water electrolysis equipment (PEWEE) and a PEFC using Nuclear-Magnetic-Resonance (NMR) sensors. The magnetic field strength induced by current through the MEA in a PEWEE is acquired as the frequency shift of the NMR signal which is measured by the NMR sensor. The spatial distributions of the frequency shifts occurring along the MEA in a PEWEE and a PEFC was measured. In order to verify the method, the magnetic field strength induced by the current through the gas diffusion layer (GDL) in a PEWEE was analyzed theoretically under the assumption that the current through MEA was uniform. The frequency shift was then calculated as a function of the geometry of the GDL, current, and the position of the NMR sensor. From experimental and theoretical results, the frequency shift of the NMR signal is proportional to current density and depends on the position of the sensors. Using the measurement system, we also obtained the current distribution through the GDL in a PEFC generating electric power. In these studies, the experimental and theoretical results agree.

  11. Evaluation and application of PEMFC fuel cell's technologies developed at IPEN applied to a 500 W{sub e} fuel cell stack; Avaliacao e aplicacao de tecnologias de celulas a combustivel tipo PEMFC desenvolvida no IPEN em um modulo de 500 W{sub e} de potencia nominal

    Energy Technology Data Exchange (ETDEWEB)

    Cunha, Edgar Ferrari da

    2009-07-01

    This work is part of a research project on PEMFC technologies carried out in IPEN to develop and optimize a 500 W{sub e} fuel cell stack. The MEAs scaling up from 25 cm{sup 2} to 144 cm{sup 2} produced by the method of sieve printing; computational fluid dynamics by computer simulation of gas flow channels in bipolar plates using COMSOL{sup R} program and the use of Pt/C electrodes developed by alcohol reduction method in single cells were used to build a stack of 500 W{sub e} nominal power for possible commercial applications, produced with national technology and industrial support. A 100 hours fuel cell's test was carried out in a 144 cm{sup 2} single cell to study the stability of the MEA fabricated by sieve printing method. This single cell showed good stability within this period of time. The developed stack has reached the maximum power of 574 W{sub e} at 100 A (694.4 mA cm{sup -2}). The operating power of 500 W{sub e} was obtained at 77.7 A (540.1 mA cm{sup -2}) and potential of 6.43 V, with efficiency of 43.3%. In terms of cogeneration, the thermal power or generated heat by the stack was 652 W{sub t}. The initial estimated cost for the 500 W{sub e} stack was about R$ 4,500.00, considering only the used materials for its construction. (author)

  12. 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.

  13. Seismic qualification of ventilation stack

    International Nuclear Information System (INIS)

    This paper describes the method to be used to qualify the 105 K ventilation stack at the U.S. Department of Energy's Hanford Site, near Richland, Washington, under seismic and wind loadings. The stack stands at 175 ft (53.34 m), with a diameter tapering from 22 ft (6.71 m) at the foundation to 12.83 ft (3.91 m) at the top. Although the stack is classified as Safety Class 3 (low hazard), it is treated as a Safety Class 1 (high hazard) component, as failure could damage a Safety Class 1 facility (the irradiated fuel storage basin). The evaluation used U.S. Department of Energy criteria specified in UCRL 15910 (1990). The seismic responses of the stack under earthquake loading were obtained from modal analyses with response spectrum input that used the ANSYS (1989) finite-element computer code. The moments and shear forces from the results of seismic analysis were used to qualify the reinforcement capacity of the stack structure by the ultimate-strength method. The wind forces acting on the stack in both along-wind and crosswind directions were also calculated. Presented are evaluations of the soil bearing pressure, the moment, and the shear capacity of the stack foundation

  14. Seismic qualification of ventilation stack

    International Nuclear Information System (INIS)

    This paper describes the method to be used to qualify the 105 K ventilation stack at the US Department of Energy's Hanford Site, near Richland, Washington, under seismic and wind loadings. The stack stands at 175 ft (53.34 m), with a diameter tapering from 22 ft (6.71 m) at the foundation to 12.83 ft (3.91 m) at the top. Although the stack is classified as Safety Class 3 (low hazard), it is treated as a Safety Class 1 (high hazard) component, as failure could damage a Safety Class 1 facility (the irradiated fuel storage basin). The evaluation used US Department of Energy criteria specified in UCRL 15910 (1990). The seismic responses of the stack under earthquake loading were obtained from modal analyses with response spectrum input that used the ANSYS (1989) finite-element computer code. The moments and shear forces from the results of seismic analysis were used to qualify the reinforcement capacity of the stack structure by the ultimate-strength method. The wind forces acting on the stack in both along-wind and are evaluations of the soil bearing pressure, the moment, and the shear capacity of the stack foundation

  15. Environmental assessment of phosphogypsum stacks

    International Nuclear Information System (INIS)

    Phosphogypsum is one of the most important by-products of phosphate fertilizer industry. It is kept in large stacks to the west of Homs city. Storing Phosphogypsum as open stacks exposed to various environmental effects, wind and rain, may cause pollution of the surrounding ecosystem (soil, plant, water and air). This study was carried out in order to assess the environmental impact of Phosphogypsum stacks on the surrounding ecosystem. The obtained results show that Phosphogypsum stacks did not increase the concentration of radionuclides, i.e. Radon-222 and Radium-226, the external exposed dose of gamma rays, as well as the concentration of heavy metals in the components of the ecosystem, soil, plant, water and air, as their concentrations did not exceed the permissible limits. However, the concentration of fluorine in the upper layer of soil, located to the east of the Phosphogypsum stacks, increased sufficiently, especially in the dry period of the year. Also, the concentration of fluoride in plants growing up near-by the Phosphogypsum stacks was too high, exceeded the permissible levels. This was reflected in poising plants and animals, feeding on the plants. Consequently, increasing the concentration of fluoride in soil and plants is the main impact of Phosphogypsum stacks on the surrounding ecosystem. Minimising this effect could be achieved by establishing a 50 meter wide protection zone surrounding the Phosphogypsum stacks, which has to be planted with non palatable trees, such as pine and cypress, forming wind barriers. Increasing the concentrations of heavy metals and fluoride in infiltrated water around the stacks was high; hence cautions must be taken to prevent its usage in any application or disposal in adjacent rivers and leaks.(author)

  16. Montagem e caracterização elétrica de pilhas a combustível de óxido sólido (PaCOS Assembly and electrical characterization of solid oxide fuel cell stacks

    Directory of Open Access Journals (Sweden)

    Hosane Aparecida Tarôco

    2009-01-01

    Full Text Available This paper is focused on a review of the design features and the electrochemistry characterization of anode-supported planar SOFC. Studies and results of metallic alloy interconnectors and recovery for protection against corrosion and for contact layer are showed. Moreover a discussion of examples of measurements of impedance spectrometry, according to the literature and our experimental results are made. For the anode supported fuel cells the power density varies from 0.1 to 0.5 Wcm², according to results in the literature (showed in this paper. For electrolyte supported fuel cell the power density can be 10 Wcm-2 for high temperatures. An English-Portuguese glossary of most used terms in SOFC stack is given for greater clarity and to introduce new terms to the reader.

  17. Ekonomické dopady zavedení certifikátů FSC a PEFC do společnosti hospodařící v lesním hospodářství

    OpenAIRE

    Neshybová, Zuzana

    2014-01-01

    The subject of this work is to determine the economic impact in the implementation of the certification systems PEFC and FSC. I have chosen the forest company, for which there were ascertained potential costs and revenues for introduction of these certifications and their maintenance in any company. For my research were used Porter's five forces analysis, questionnaire and theoretical measuring of costs. Recommendation based on collected data, was given to chosen company.

  18. Time-predictable Stack Caching

    DEFF Research Database (Denmark)

    Abbaspourseyedi, Sahar

    complicated and less imprecise. Time-predictable computer architectures provide solutions to this problem. As accesses to the data in caches are one source of timing unpredictability, devising methods for improving the timepredictability of caches are important. Stack data, with statically analyzable...... addresses, provides an opportunity to predict and tighten the WCET of accesses to data in caches. In this thesis, we introduce the time-predictable stack cache design and implementation within a time-predictable processor. We introduce several optimizations to our design for tightening the WCET while...... keeping the timepredictability of the design intact. Moreover, we provide a solution for reducing the cost of context switching in a system using the stack cache. In design of these caches, we use custom hardware and compiler support for delivering time-predictable stack data accesses. Furthermore, for...

  19. Metal/ceria water-gas shift catalysts for automotive polymer electrolyte fuel cell system

    International Nuclear Information System (INIS)

    Polymer electrolyte fuel cell (PEFC) systems are a leading candidate for replacing the internal combustion engine in light duty vehicles. One method of generating the hydrogen necessary for the PEFC is reforming a liquid fuel, such as methanol or gasoline, via partial oxidation, steam reforming, or autothermal reforming (a combination of partial oxidation and steam reforming). The H(sub 2)-rich reformate can contain as much as 10% carbon monoxide. Carbon monoxide has been shown to poison the platinum-based anode catalyst at concentrations as low as 10 ppm,1 necessitating removal of CO to this level before passing the reformate to the fuel cell stack. The water-gas shift (WGS) reaction, CO+ H(sub 2)O(rightleftharpoons) CO(sub 2)+ H(sub 2), is used to convert the bulk of the reformate CO to CO(sub 2). Industrially, the WGS reaction is conducted over two catalysts, which operate in different temperature regimes. One catalyst is a FeCr mixed oxide, which operates at 350-450 C and is termed the high-temperature shift (HTS) catalyst. The second catalyst is a CuZn mixed oxide, which operates at 200-250 C and is termed the low-temperature shift (LTS) catalyst. Although these two catalysts are used industrially in the production of H(sub 2) for ammonia synthesis, they have major drawbacks that make them unsuitable for transportation applications. Both the LTS and the HTS catalysts must first be ''activated'' before being used. For example, the copper in the copper oxide/zinc oxide LTS catalyst must first be reduced to elemental copper in situ before it becomes active for the WGS reaction. This reduction reaction is exothermic and must be carried out under well- controlled conditions using a dilute hydrogen stream (1 vol% H(sub 2)) to prevent high catalyst temperatures, which can result in sintering (agglomeration) of the copper particles and loss of active surface area for the WGS reaction. Also, once the catalyst has been activated by reduction, it must be protected from

  20. Soft X-ray imaging and spectromicroscopy: new insights in chemical state and morphology of the key components in operating fuel-cells.

    Science.gov (United States)

    Bozzini, Benedetto; Abyaneh, Majid Kazemian; Amati, Matteo; Gianoncelli, Alessandra; Gregoratti, Luca; Kaulich, Burkhard; Kiskinova, Maya

    2012-08-13

    Fuel cells are one of the most appealing environmentally friendly devices for the effective conversion of chemical energy into electricity and heat, but still there are key barriers to their broad commercialization. In addition to efficiency, a major challenge of fuel-cell technology is the durability of the key components (interconnects, electrodes, and electrolytes) that can be subject to corrosion or undesired morphology and chemical changes occurring under operating conditions. The complementary capabilities of synchrotron-based soft X-ray microscopes in terms of imaging, spectroscopy, spatial and time resolution, and variable probing depths are opening unique opportunities to shed light on the multiple processes occurring in these complex systems at microscopic length scales. This type of information is prerequisite for understanding and controlling the performance and durability of such devices. This paper reviews the most recent efforts in the implementation of these methods for exploring the evolving structure and chemical composition of some key fuel cell components. Recent achievements are illustrated by selected results obtained with simplified versions of proton-exchange fuel-cells (PEFC) and solid-oxide fuel-cells (SOFC), which allow in situ monitoring of the redox reactions resulting in: 1) undesired deposits at interconnects and electrodes (PEFC); 2) material interactions at the electrode-electrolyte interface (PEFC); 3) release of corrosion products to the electrolyte phase (PEFC, and 4) mass-transport processes and structural changes occurring at the high operation temperatures of SOFC and promoted by the polarization. PMID:22836392

  1. Design and Fabrication of Stack Micro-Direct Methanol Fuel Cell Using Silicon and PDMS%采用硅和PDMS的堆栈式微型直接甲醇燃料电池的设计和制作

    Institute of Scientific and Technical Information of China (English)

    曾毅波; 陈观生; 赵祖光; 刘畅; 刘俊; 王婷婷; 郭航

    2013-01-01

    In order to avoid cracks of the silicon flow field plate caused by high package pressure, silicon and PDMS (Polydimethylsiloxane) are used as anodic and cathode flow field plate respectively in the stack μ-DMFC ( Micro-direct methanol fuel cell). The anodic flow field plate based on silicon is fabricated with MEMS( Micro-Electro-Mechanical Systems)technology,and cathode flow field plate is fabricated using PDMS and its metallic performance is evidently improved by means of integral shaping of copper foil and cathode flow field plate, organic cleaning and activation on PDMS surface. The output of stack μ-DMFC is tested and analyzed, in which 3 different flow channel structures on the anodic plate are introduced. Tested results verify that adhesive capability and strengthen between post-activated PDMS and Cr/Au are greatly improved, and when micro blocks and through holes are introduced alternately in the flow channel of anodic flow field plate the stack μ-DMFC can obtain the maximum output, with voltage of 0. 5 V,current density of 81. 25 mA/cm2 and output power density of 7. 73 mW/cm2. This study shows that using silicon and PDMS as flow field plate respectively not only simplifies the structure of stack μ-DMFC but also cushions clamping force and effectively protects anodic flow field plate,and furthermore to increase the output of stack μ-DMFC by optimizing structure of flow channels on the anodic flow field plate.%在堆栈式微型直接甲醇燃料电池μ-DMFC(Micro-Direct Methanol Fuel Cell)中,为了避免硅基流场板因为封装压力过大而破裂,采用了硅和PDMS(Polydimethylsiloxane,聚二甲基硅氧烷)材料分别制作阳极和阴极流场板.首先,采用微机电系统MEMS(Micro-Electro-Mechanical Systems)技术制作硅基阳极流场板.其次,通过铜箔与阴极流场板一体成型、有机清洗和PDMS表面活化等改进措施显著提升了PDMS阴极流场板金属化的能力.最后,比较和分析阳极流场板上3

  2. Fuel cell power trains for road traffic

    Science.gov (United States)

    Höhlein, Bernd; Biedermann, Peter; Grube, Thomas; Menzer, Reinhard

    Legal regulations, especially the low emission vehicle (LEV) laws in California, are the driving forces for more intensive technological developments with respect to a global automobile market. In the future, high efficient vehicles at very low emission levels will include low temperature fuel cell systems (e.g., polymer electrolyte fuel cell (PEFC)) as units of hydrogen-, methanol- or gasoline-based electric power trains. In the case of methanol or gasoline/diesel, hydrogen has to be produced on-board using heated steam or partial oxidation reformers as well as catalytic burners and gas cleaning units. Methanol could also be used for direct electricity generation inside the fuel cell (direct methanol fuel cell (DMFC)). The development potentials and the results achieved so far for these concepts differ extremely. Based on the experience gained so far, the goals for the next few years include cost and weight reductions as well as optimizations in terms of the energy management of power trains with PEFC systems. At the same time, questions of fuel specification, fuel cycle management, materials balances and environmental assessment will have to be discussed more intensively. On the basis of process engineering analyses for net electricity generation in PEFC-powered power trains as well as on assumptions for both electric power trains and vehicle configurations, overall balances have been carried out. They will lead not only to specific energy demand data and specific emission levels (CO 2, CO, VOC, NO x) for the vehicle but will also present data of its full fuel cycle (FFC) in comparison to those of FFCs including internal combustion engines (ICE) after the year 2005. Depending on the development status (today or in 2010) and the FFC benchmark results, the advantages of balances results of FFC with PEFC vehicles are small in terms of specific energy demand and CO 2 emissions, but very high with respect to local emission levels.

  3. Air-Cooled Stack Freeze Tolerance Freeze Failure Modes and Freeze Tolerance Strategies for GenDriveTM Material Handling Application Systems and Stacks Final Scientific Report

    Energy Technology Data Exchange (ETDEWEB)

    Hancock, David, W.

    2012-02-14

    Air-cooled stack technology offers the potential for a simpler system architecture (versus liquid-cooled) for applications below 4 kilowatts. The combined cooling and cathode air allows for a reduction in part count and hence a lower cost solution. However, efficient heat rejection challenges escalate as power and ambient temperature increase. For applications in ambient temperatures below freezing, the air-cooled approach has additional challenges associated with not overcooling the fuel cell stack. The focus of this project was freeze tolerance while maintaining all other stack and system requirements. Through this project, Plug Power advanced the state of the art in technology for air-cooled PEM fuel cell stacks and related GenDrive material handling application fuel cell systems. This was accomplished through a collaborative work plan to improve freeze tolerance and mitigate freeze-thaw effect failure modes within innovative material handling equipment fuel cell systems designed for use in freezer forklift applications. Freeze tolerance remains an area where additional research and understanding can help fuel cells to become commercially viable. This project evaluated both stack level and system level solutions to improve fuel cell stack freeze tolerance. At this time, the most cost effective solutions are at the system level. The freeze mitigation strategies developed over the course of this project could be used to drive fuel cell commercialization. The fuel cell system studied in this project was Plug Power's commercially available GenDrive platform providing battery replacement for equipment in the material handling industry. The fuel cell stacks were Ballard's commercially available FCvelocity 9SSL (9SSL) liquid-cooled PEM fuel cell stack and FCvelocity 1020ACS (Mk1020) air-cooled PEM fuel cell stack.

  4. The Golgi apparatus in the endomembrane-rich gastric parietal cells exist as functional stable mini-stacks dispersed throughout the cytoplasm

    OpenAIRE

    Gunn, Priscilla A.; Gliddon, Briony L.; Londrigan, Sarah L.; Lew, Andrew M.; van Driel, Ian R.; Gleeson, Paul A.

    2011-01-01

    Background information. Acid-secreting gastric parietal cells are polarized epithelial cells that harbour highly abundant and specialized, H+,K+ ATPase-containing, tubulovesicular membranes in the apical cytoplasm. The Golgi apparatus has been implicated in the biogenesis of the tubulovesicular membranes; however, an unanswered question is how a typical Golgi organization could regulate normal membrane transport within the membrane-dense cytoplasm of parietal cells. Results. Here, we demonstr...

  5. Glassy carbon based supercapacitor stacks

    Energy Technology Data Exchange (ETDEWEB)

    Baertsch, M.; Braun, A.; Koetz, R.; Haas, O. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    Considerable effort is being made to develop electrochemical double layer capacitors (EDLC) that store relatively large quantities of electrical energy and possess at the same time a high power density. Our previous work has shown that glassy carbon is suitable as a material for capacitor electrodes concerning low resistance and high capacity requirements. We present the development of bipolar electrochemical glassy carbon capacitor stacks of up to 3 V. Bipolar stacks are an efficient way to meet the high voltage and high power density requirements for traction applications. Impedance and cyclic voltammogram measurements are reported here and show the frequency response of a 1, 2, and 3 V stack. (author) 3 figs., 1 ref..

  6. Removal of NOx with Porous Cell Stacks with La0.85Sr0.15CoxMn1-xO3+δ-Ce0.9Gd0.1O1.95 Electrodes Infiltrated with BaO

    DEFF Research Database (Denmark)

    Werchmeister, Rebecka Maria Larsen; Bentzen, Janet Jonna; Andersen, Kjeld Bøhm; Kammer Hansen, Kent

    2014-01-01

    Porous cell stacks with composite electrodes of La0.85Sr0.15CoxMn1-xO3-Ce0.9Gd0.1O1.95 were tested for activity toward selective electrochemical reduction of NOx to N2 in the presence of 10% O2. The cell stacks were produced by tape casting, laminating and sintering the backbone structure followed...

  7. Multiple Segmentation of Image Stacks

    DEFF Research Database (Denmark)

    Smets, Jonathan; Jaeger, Manfred

    2014-01-01

    We propose a method for the simultaneous construction of multiple image segmentations by combining a recently proposed “convolution of mixtures of Gaussians” model with a multi-layer hidden Markov random field structure. The resulting method constructs for a single image several, alternative...... segmentations that capture different structural elements of the image. We also apply the method to collections of images with identical pixel dimensions, which we call image stacks. Here it turns out that the method is able to both identify groups of similar images in the stack, and to provide segmentations...

  8. Simulating Small-Scale Object Stacking Using Stack Stability

    DEFF Research Database (Denmark)

    Kronborg Thomsen, Kasper; Kraus, Martin

    2015-01-01

    This paper presents an extension system to a closed-source, real-time physics engine for improving structured stacking behavior with small-scale objects such as wooden toy bricks. The proposed system was implemented and evaluated. The tests showed that the system is able to simulate several common...

  9. Key Materials and Micro-Stack Systems of Single Chamber Solid Oxide Fuel Cells%单气室固体氧化物燃料电池关键材料与微堆系统

    Institute of Scientific and Technical Information of China (English)

    吕喆; 魏波; 田彦婷; 王志红; 苏文辉

    2011-01-01

    单气室固体氧化物燃料电池(SC-SOFC)是一种与传统的双气室结构燃料电池不同的新型燃料电池.SC-SOFC的阴极和阳极都暴露在单一气室中,在工作时通入含有燃料和氧化剂的混合气体,利用阳极和阴极的选择催化作用实现发电.SC-SOFC具有结构简单、无需密封、易于进行堆叠等很多独特的优点.本文介绍了SC-SOFC近期的研究进展,内容包括工作原理的介绍、SC-SOFC的关键材料选择与研究现状、影响SC-SOFC运行的主要因素的讨论,以及微堆(电池组)系统结构设计和试验等.着重介绍了本课题组在SC-SOFC的研究工作,包括对复合阴极材料、Ni修饰氧化物阳极的研究,以及星型和阵列式等多种新型SC-SOFC微堆结构设计与实验等.最后,基于对其优缺点的分析,展望了SC-SOFC各种潜在的应用.%Single chamber solid oxide fuel cell (SC-SOFC) is different from the conventional solid oxide fuel cell with dual gas chamber structure.Both cathode and anode of SC-SOFC are exposed to the only one gas chamber.Mixed gas containing fuel and oxidant is fed during operation and it can generate electric energy by the selectively catalytic activities of cathode and anode.SC-SOFC has many particular advatages, such as more simple structure, eliminating the need for sealing and easy stacking etc.In this paper, the recent research advances of SC-SOFC are reviewed, including brief introduction of operational principle of SC-SOFC, the selection of key materials for SC-SOFC, the discussion of main influencing factors on SC-SOFC, as well as the design and test of micro-stack (battery) system.The investigation results on SC-SOFC of our research group are highlighted, including composite cathode, oxide anode with Ni modification, and some novel designs for SC-SOFC micro stacks, such as star-type and array-type stacks, and so on.Finally, an outlook about the potential applications of SC-SOFC is given according to the analysis of

  10. Pressurized electrolysis stack with thermal expansion capability

    Energy Technology Data Exchange (ETDEWEB)

    Bourgeois, Richard Scott

    2015-07-14

    The present techniques provide systems and methods for mounting an electrolyzer stack in an outer shell so as to allow for differential thermal expansion of the electrolyzer stack and shell. Generally, an electrolyzer stack may be formed from a material with a high coefficient of thermal expansion, while the shell may be formed from a material having a lower coefficient of thermal expansion. The differences between the coefficients of thermal expansion may lead to damage to the electrolyzer stack as the shell may restrain the thermal expansion of the electrolyzer stack. To allow for the differences in thermal expansion, the electrolyzer stack may be mounted within the shell leaving a space between the electrolyzer stack and shell. The space between the electrolyzer stack and the shell may be filled with a non-conductive fluid to further equalize pressure inside and outside of the electrolyzer stack.

  11. Multibeam collimator uses prism stack

    Science.gov (United States)

    Minott, P. O.

    1981-01-01

    Optical instrument creates many divergent light beams for surveying and machine element alignment applications. Angles and refractive indices of stack of prisms are selected to divert incoming laser beam by small increments, different for each prism. Angles of emerging beams thus differ by small, precisely-controlled amounts. Instrument is nearly immune to vibration, changes in gravitational force, temperature variations, and mechanical distortion.

  12. Transgene Stacking in Cotton Improvement

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    To date,more and more transgenic varieties of upland cotton(Gossypium hirsutum L.) generated with transgenes,which derived from varies of alien species,are playing important role in agricultural production.Stacking of multi-transgenes has a potential for combining all the merits of distinct

  13. Multilayer Piezoelectric Stack Actuator Characterization

    Science.gov (United States)

    Sherrit, Stewart; Jones, Christopher M.; Aldrich, Jack B.; Blodget, Chad; Bao, Xioaqi; Badescu, Mircea; Bar-Cohen, Yoseph

    2008-01-01

    Future NASA missions are increasingly seeking to use actuators for precision positioning to accuracies of the order of fractions of a nanometer. For this purpose, multilayer piezoelectric stacks are being considered as actuators for driving these precision mechanisms. In this study, sets of commercial PZT stacks were tested in various AC and DC conditions at both nominal and extreme temperatures and voltages. AC signal testing included impedance, capacitance and dielectric loss factor of each actuator as a function of the small-signal driving sinusoidal frequency, and the ambient temperature. DC signal testing includes leakage current and displacement as a function of the applied DC voltage. The applied DC voltage was increased to over eight times the manufacturers' specifications to investigate the correlation between leakage current and breakdown voltage. Resonance characterization as a function of temperature was done over a temperature range of -180C to +200C which generally exceeded the manufacturers' specifications. In order to study the lifetime performance of these stacks, five actuators from one manufacturer were driven by a 60volt, 2 kHz sine-wave for ten billion cycles. The tests were performed using a Lab-View controlled automated data acquisition system that monitored the waveform of the stack electrical current and voltage. The measurements included the displacement, impedance, capacitance and leakage current and the analysis of the experimental results will be presented.

  14. Validation of a HT-PEMFC stack for CHP applications

    Energy Technology Data Exchange (ETDEWEB)

    Pasupathi, S.; Ulleberg, Oe. [Western Cape Univ. (South Africa). HySA Systems, SAIAMC; Bujlo, P. [Western Cape Univ. (South Africa). HySA Systems, SAIAMC; Electrotechnical Institute Wroclaw Division (Poland); Scholta, J. [Centre for Solar Energy and Hydrogen Research (ZSW) (Germany)

    2010-07-01

    Fuel cell systems are very attractive for stationary co-generation applications as they can produce heat and electricity efficiently in a decentralized and environmentally friendly manner. PEMFC stacks operating at temperatures above 120 C, specifically in the range of 140-180 C, are ideal for co-generation purposes. In this study, preliminary results from a HTPEMFC stack designed for CHP applications is presented and discussed. A short, five-cell, HT-PEMFC stack was assembled with Celtec- P-2100 MEAs and validated in terms of electrical performance. The stack was operated with hydrogen and air at 160 C and the utilization curves for anode and cathode were recorded for a wide range of gas utilization at a current density of 0.52 A/cm{sup 2}. The current voltage characteristic was measured at optimal utilization values at 160 C. A 1kW stack is assembled and is currently being validated for its performance under various operating conditions for use in CHP applications. (orig.)

  15. Manufacturing and characterisation of electrode membrane assemblies for low temperature fuel cells; Herstellung und Charakterisierung von Membran-Elektroden-Einheiten fuer Niedertemperatur Brennstoffzellen

    Energy Technology Data Exchange (ETDEWEB)

    Kaz, Till

    2008-08-22

    The high cost for a Polymer electrolyte Fuel Cell (PEFC) System is still a barrier for commercial breakthrough, which cannot be compensated by the advantages of being pollution free, or nearly noiseless. The most effective way of saving costs is to reduce expensive materials, because the material costs only for the Membrane Electrode Assemblies (MEAs) is more than 70% of the total costs of a PEFC Stack. Within the MEA a main part of the costs is due to the catalyst. It is one of the main goals to decrease the catalyst loading by simultaneously increasing the performance or keeping it at least constant. Because in most electrodes only 20-50% of the catalyst in the electrodes is used, enlarging the electrochemical active area is one of the key problems of the PEFC. For being electrochemical active, the catalyst must be reachable for the gases, he must have a good ionic conductivity to the membrane and he must be attached to the Gas Diffusion Layer (GDL) by electron conductivity. In literature often an inferior ionic contact of the catalyst to the membrane is responsible for the low catalyst utilization. In the first part of the work, model electrodes with different kinds of catalysts and different amounts of electrolyte in the electrodes were investigated to explore the interrelationship between platinum and electrolyte content. Three different catalysts, unsupported Pt- black, 60 wt.% Pt carbon-supported and 20 wt.% Pt carbon-supported with an addition of Nafion powder of 0%, 20%, 40%, 60 wt.%, and 80 wt.% were used. The electrodes were prepared by spraying the electrode material with the DLR dry spray technique directly onto the membrane and then rolling them while hot. Because material solutions were not used, the structure of the electrodes are determinable and predictable. Numerous different in- and ex-situ characterization methods like impedance spectroscopy, U-i characteristic, cyclic voltammetry, proton conductivity measurements, half-cell measurements and

  16. Multi-functional stacked light-trapping structure for stabilizing and boosting solar-electricity efficiency of hydrogenated amorphous silicon solar cells

    Science.gov (United States)

    Huang, Wen-Hsien; Shieh, Jia-Min; Pan, Fu-Ming; Shen, Chang-Hong; Huang, Jung Y.; Wu, Tsung-Ta; Kao, Ming-Hsuan; Hsiao, Tzu-Hsuan; Yu, Peichen; Kuo, Hao-Chung; Lee, Ching-Ting

    2013-08-01

    A sandwiched light-trapping electrode structure, which consists of a capping aluminum-doped ZnO (AZO) layer, dispersed plasmonic Au-nanoparticles (Au-NPs), and a micro-structured transparent conductive substrate, is employed to stabilize and boost the conversion-efficiency of hydrogenated amorphous silicon (a-Si:H) solar cells. The conformal AZO ultrathin layer (5 nm) smoothened the Au-NP-dispersed electrode surface, thereby reducing defects across the AZO/a-Si:H interface and resulting in a high resistance to photo-degradation in the ultraviolet-blue photoresponse band. With the plasmonic light-trapping structure, the cell has a high conversion-efficiency of 10.1% and the photo-degradation is as small as 7%.

  17. Federation of OpenStack clouds

    OpenAIRE

    Tartarini, Luca; Denis, Marek

    2014-01-01

    Project Specification Rackspace and CERN are implementing federated identity of OpenStack clouds within the OpenStack cloud project. The project is to enhance the client tools in OpenStack to support Thefederated identity functionalities, work with the open source community to incorporate these changes into the product and adapt the documentation and testing. The student will learn about the internals of OpenStack, federated identity techniques such as SAML and working with open sour...

  18. Mass transport aspects of polymer electrolyte fuel cells under two-phase flow conditions

    Energy Technology Data Exchange (ETDEWEB)

    Kramer, D.

    2007-03-15

    This well-illustrated, comprehensive dissertation by Dr. Ing. Denis Kramer takes an in-depth look at polymer electrolyte fuel cells (PEFC) and the possibilities for their application. First of all, the operating principles of polymer electrolyte fuel cells are described and discussed, whereby thermodynamics aspects and loss mechanisms are examined. The mass transport diagnostics made with respect to the function of the cells are discussed. Field flow geometry, gas diffusion layers and, amongst other things, liquid distribution, the influence of flow direction and the low-frequency behaviour of air-fed PEFCs are discussed. Direct methanol fuel cells are examined, as are the materials chosen. The documentation includes comprehensive mathematical and graphical representations of the mechanisms involved.

  19. 49 CFR 178.606 - Stacking test.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Stacking test. 178.606 Section 178.606... Testing of Non-bulk Packagings and Packages § 178.606 Stacking test. (a) General. All packaging design types other than bags must be subjected to a stacking test. (b) Number of test samples. Three...

  20. Simulation and Optimization of Air-Cooled PEMFC Stack for Lightweight Hybrid Vehicle Application

    OpenAIRE

    Jingming Liang; Zefeng Wu

    2015-01-01

    A model of 2 kW air-cooled proton exchange membrane fuel cell (PEMFC) stack has been built based upon the application of lightweight hybrid vehicle after analyzing the characteristics of heat transfer of the air-cooled stack. Different dissipating models of the air-cooled stack have been simulated and an optimal simulation model for air-cooled stack called convection heat transfer (CHT) model has been figured out by applying the computational fluid dynamics (CFD) software, based on which, the...

  1. New approaches towards novel composite and multilayer membranes for intermediate temperature-polymer electrolyte fuel cells and direct methanol fuel cells

    Science.gov (United States)

    Branco, Carolina Musse; Sharma, Surbhi; de Camargo Forte, Maria Madalena; Steinberger-Wilckens, Robert

    2016-06-01

    This review analyses the current and existing literature on novel composite and multilayer membranes for Polymer Electrolyte Fuel Cell applications, including intermediate temperature polymer electrolyte fuel cell (IT-PEFC) and direct methanol fuel cell (DMFC) systems. It provides a concise scrutiny of the vast body of literature available on organic and inorganic filler based polymer membranes and links it to the new emerging trend towards novel combinations of multilayered polymer membranes for applications in DMFC and IT-PEFC. The paper carefully explores the advantages and disadvantages of the most common preparation techniques reported for multilayered membranes such as hot-pressing, casting and dip-coating and also summarises various other fresh and unique techniques employed for multilayer membrane preparation.

  2. Nonlinear Predictive Control for PEMFC Stack Operation Temperature

    Institute of Scientific and Technical Information of China (English)

    LI Xi; CAO Guang-yi; ZHU Xin-jian

    2005-01-01

    Operating temperature of proton exchange membrane fuel cell stack should be controlled within a special range. The input-output data and operating experiences were used to establish a PEMFC stack model and operating temperature control system. A nonlinear predictive control algorithm based on fuzzy model was presented for a family of complex system with severe nonlinearity such as PEMFC. Based on the obtained fuzzy model, a discrete optimization of the control action was carried out according to the principle of Branch and Bound method. The test results demonstrate the effectiveness and advantage of this approach.

  3. Durable SOC stacks for production of hydrogen and synthesis gas by high temperature electrolysis

    DEFF Research Database (Denmark)

    Ebbesen, Sune Dalgaard; Høgh, Jens Valdemar Thorvald; Nielsen, Karsten Agersted;

    2011-01-01

    Electrolysis of steam and co-electrolysis of steam and carbon dioxide was studied in Solid Oxide Electrolysis Cell (SOEC) stacks composed of Ni/YSZ electrode supported SOECs. The results of this study show that long-term electrolysis is feasible without notable degradation in these SOEC stacks. T...

  4. High Temperature Co‐Electrolysis of Steam and CO2 in an SOC Stack: Performance and Durability

    DEFF Research Database (Denmark)

    Chen, Ming; Høgh, Jens Valdemar Thorvald; Nielsen, J. U.;

    2013-01-01

    In this work, co‐electrolysis of steam and carbon dioxide was studied in a Topsoe Fuel Cell (TOFC®) 10‐cell stack, containing three different types of Ni/yttria stabilized zirconia (YSZ) electrode supported solid oxide electrolysis cells with a footprint of 12 × 12 cm. The stack was operated at 8...

  5. Modeling Water Management in Polymer-Electrolyte Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Department of Chemical Engineering, University of California, Berkeley; Weber, Adam; Weber, Adam Z.; Balliet, Ryan; Gunterman, Haluna P.; Newman, John

    2007-09-07

    Fuel cells may become the energy-delivery devices of the 21st century with realization of a carbon-neutral energy economy. Although there are many types of fuel cells, polymerelectrolyte fuel cells (PEFCs) are receiving the most attention for automotive and small stationary applications. In a PEFC, hydrogen and oxygen are combined electrochemically to produce water, electricity, and waste heat. During the operation of a PEFC, many interrelated and complex phenomena occur. These processes include mass and heat transfer, electrochemical reactions, and ionic and electronic transport. Most of these processes occur in the through-plane direction in what we term the PEFC sandwich as shown in Figure 1. This sandwich comprises multiple layers including diffusion media that can be composite structures containing a macroporous gas-diffusion layer (GDL) and microporous layer (MPL), catalyst layers (CLs), flow fields or bipolar plates, and a membrane. During operation fuel is fed into the anode flow field, moves through the diffusion medium, and reacts electrochemically at the anode CL to form hydrogen ions and electrons. The oxidant, usually oxygen in air, is fed into the cathode flow field, moves through the diffusion medium, and is electrochemically reduced at the cathode CL by combination with the generated protons and electrons. The water, either liquid or vapor, produced by the reduction of oxygen at the cathode exits the PEFC through either the cathode or anode flow field. The electrons generated at the anode pass through an external circuit and may be used to perform work before they are consumed at the cathode. The performance of a PEFC is most often reported in the form of a polarization curve, as shown in Figure 2. Roughly speaking, the polarization curve can be broken down into various regions. First, it should be noted that the equilibrium potential differs from the open-circuit voltage due mainly to hydrogen crossover through the membrane (i.e., a mixed potential

  6. Simultaneous multilayer formation of the polymer solar cell stack using roll-to-roll double slot-die coating from water

    DEFF Research Database (Denmark)

    Larsen-Olsen, Thue Trofod; Andreasen, Birgitta; Andersen, Thomas Rieks; Böttiger, Arvid P.L.; Bundgaard, Eva; Norrman, Kion; Andreasen, Jens Wenzel; Jørgensen, Mikkel; Krebs, Frederik C

    2012-01-01

    Double slot-die coating using aqueous inks was employed for the simultaneous coating of the active layer and the hole transport layer (HTL) in fully roll-to-roll (R2R) processed polymer solar cells. The double layer film was coated directly onto an electron transport layer (ETL) comprising doped...... zinc oxide that was processed by single slot-die coating from water. The active layer comprised poly-3-hexylthiophene:Phenyl-C61-butyric acid methyl ester (P3HT:PCBM) as a dispersion of nanoparticles with a radius of 46 nm in water characterized using small-angle X-ray scattering (SAXS), transmission...... electron microscopy (TEM), and atomic force microscopy (AFM). The HTL was a dispersion of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) in water. The films were analyzed using time-of-flight secondary ion mass spectrometry (TOF-SIMS) as chemical probe and X-ray reflectometry as...

  7. High temperature steam electrolysis stack with enhanced performance and durability

    International Nuclear Information System (INIS)

    High Temperature Steam Electrolysis (HTSE) is one of the most promising ways for hydrogen production. If coupled to a CO2-free electricity and low cost heat sources, this process is liable to a high efficiency. The present study describes recent promising results obtained in terms of performance and durability in stack environment, thanks to the use of protective coatings on one hand, and of advanced cells on the other hand. As for Solid Oxide Fuel Cells, it has been demonstrated that the integration of protective coatings was mandatory to decrease the degradation rate in HTSE stacks, and that with optimized coatings, (CoMn)3O4 in the present case, the same durability as the one of the single cell tested in a ceramic housing could be reached. The type of cell was also shown to play a major role on the degradation rate. With advanced cells, degradations below 2%/kh could be reached. The higher is the current density, the higher is the degradation rate, with a mostly reversible effect. These degradation rates are close to the objectives, even if a bit higher than in SOFC mode. Finally a low-weight stack has been designed, targeting high performance and durability while reducing the cost by the use of thin interconnects. An electrochemical performance similar to the previous stack design has been obtained for a 3-cell stack (-1 A/cm2) at 1.3 V at 800 degrees C), with degradation rates below 3%/1000 h in the testing conditions. The thermal cyclability of stacks has been demonstrated, from 800 degrees C to 20 degrees C, as well as electrical load cycling. The results showed that the HTSE stacks considered in the present study can cycle very rapidly, and that the cycles considered do not induce any degradation. Therefore it can be concluded that these results makes HTSE technology getting closer to the objectives of performance, durability, thermal and electrical cyclability and cost, and that HTSE is a candidate to produce hydrogen as a mean to store renewable

  8. Fuel quality issues in stationary fuel cell systems.

    Energy Technology Data Exchange (ETDEWEB)

    Papadias, D.; Ahmed, S.; Kumar, R. (Chemical Sciences and Engineering Division)

    2012-02-07

    Fuel cell systems are being deployed in stationary applications for the generation of electricity, heat, and hydrogen. These systems use a variety of fuel cell types, ranging from the low temperature polymer electrolyte fuel cell (PEFC) to the high temperature solid oxide fuel cell (SOFC). Depending on the application and location, these systems are being designed to operate on reformate or syngas produced from various fuels that include natural gas, biogas, coal gas, etc. All of these fuels contain species that can potentially damage the fuel cell anode or other unit operations and processes that precede the fuel cell stack. These detrimental effects include loss in performance or durability, and attenuating these effects requires additional components to reduce the impurity concentrations to tolerable levels, if not eliminate the impurity entirely. These impurity management components increase the complexity of the fuel cell system, and they add to the system's capital and operating costs (such as regeneration, replacement and disposal of spent material and maintenance). This project reviewed the public domain information available on the impurities encountered in stationary fuel cell systems, and the effects of the impurities on the fuel cells. A database has been set up that classifies the impurities, especially in renewable fuels, such as landfill gas and anaerobic digester gas. It documents the known deleterious effects on fuel cells, and the maximum allowable concentrations of select impurities suggested by manufacturers and researchers. The literature review helped to identify the impurity removal strategies that are available, and their effectiveness, capacity, and cost. A generic model of a stationary fuel-cell based power plant operating on digester and landfill gas has been developed; it includes a gas processing unit, followed by a fuel cell system. The model includes the key impurity removal steps to enable predictions of impurity breakthrough

  9. Visualization of Water Accumulation Process in Polymer Electrolyte Fuel Cell Using Neutron Radiography

    Science.gov (United States)

    Murakawa, Hideki; Sugimoto, Katsumi; Kitamura, Nobuki; Sawada, Masataka; Asano, Hitoshi; Takenaka, Nobuyuki; Saito, Yasushi

    In order to clarify the water-accumulation phenomena in an operating polymer electrolyte fuel cell (PEFC), the water distribution in a small fuel cell was measured in the through-plane direction by using neutron radiography. The fuel cell had nine parallel channels for classifying the water-accumulation process in the gas diffusion layer (GDL) under the lands and channels. The experimental results were compared with numerical results. The water accumulation in the GDL under the lands was larger than that under the channels during the period of early PEFC operation. The difference of the water accumulation in the GDL under the land and channel was related to the water vapor. Because of the land, the vapor fraction in the GDL under the land was also higher than that under the channel. As a result, condensation was easy to occur in the GDL under the land.

  10. Numerical and experimental studies of stack shunt current for vanadium redox flow battery

    International Nuclear Information System (INIS)

    Highlights: • A coupled three-dimensional model of VRB cell stack is developed. • Shunt current of the stack is studied with the model and experiment. • Increased electrolyte resistance in channel and manifold lowers the shunt current. • Shunt current loss increases with stack cell number nonlinearly. - Abstract: The stack shunt current of VRB (vanadium redox flow battery) was investigated with experiments and 3D (three-dimensional) simulations. In the proposed model, cell voltages and electrolyte conductivities were calculated based on electrochemical reaction distributions and SOC (state of charge) values, respectively, while coulombic loss was estimated according to shunt current and vanadium ionic crossover through membrane. Shunt current distributions and coulombic efficiency are analyzed in terms of electrolyte conductivities and stack cell numbers. The distributions of cell voltages and shunt currents calculated with proposed model are validated with single cell and short stack tests. The model can be used to optimize VRB stack manifold and channel designs to improve VRB system efficiency

  11. Indium-gallium-zinc-oxide layer used to increase light transmittance efficiency of adhesive layer for stacked-type multijunction solar cells

    Science.gov (United States)

    Yoshidomi, Shinya; Kimura, Shunsuke; Hasumi, Masahiko; Sameshima, Toshiyuki

    2015-11-01

    We report the increase in transmittance efficiency of the intermediate layer for multijunction solar cells caused by the indium-gallium-zinc-oxide (IGZO) layer used as the antireflection layer. Si substrates coated with a 200-nm-thick IGZO layer with a refractive index of 1.85 were prepared. The resistivity of the IGZO layer was increased from 0.0069 (as-deposited) to 0.032 Ω cm by heat treatment at 350 °C for 1 h to prevent free-carrier optical absorption. Samples with the Si/IGZO/adhesive/IGZO/Si structure were fabricated. The average transmissivity for wavelengths between 1200 and 1600 nm was 49%, which was close to 55% of single-crystal silicon substrates. A high effective transmittance efficiency of 89% was experimentally achieved. The numerical calculation showed in an effective transmittance efficiency of 99% for 170-nm-thick antireflection layers with a resistivity of 0.6 Ω cm and a refractive index of 2.1.

  12. Influence of different sulfur to selenium ratios on the structural and electronic properties of Cu(In,Ga)(S,Se)2 thin films and solar cells formed by the stacked elemental layer process

    International Nuclear Information System (INIS)

    In this study, we investigate the effect of different elemental selenium to elemental sulfur ratios on the chalcopyrite phase formation in Cu(In,Ga)(S,Se)2 thin films. The films are formed by the stacked elemental layer process. The structural and electronic properties of the thin films and solar cells are analyzed by means of scanning electron microscopy, glow discharge optical emission spectrometry, X-ray diffraction, X-ray fluorescence, Raman spectroscopy, spectral photoluminescence as well as current-voltage, and quantum efficiency measurements. The influence of different S/(S+Se) ratios on the anion incorporation and on the Ga/In distribution is investigated. We find a homogenous sulfur concentration profile inside the film from the top surface to the bottom. External quantum efficiency measurements show that the band edge of the solar cell device is shifted to shorter wavelength, which enhances the open-circuit voltages. The relative increase of the open-circuit voltage with S/(S+Se) ratio is lower than expected from the band gap energy trend, which is attributed to the presence of S-induced defects. We also observe a linear decrease of the short-circuit current density with increasing S/(S+Se) ratio which can be explained by a reduced absorption. Above a critical S/(S+Se) ratio of around 0.61, the fill factor drops drastically, which is accompanied by a strong series resistance increase which may be attributed to changes in the back contact or p-n junction properties.

  13. Influence of different sulfur to selenium ratios on the structural and electronic properties of Cu(In,Ga)(S,Se){sub 2} thin films and solar cells formed by the stacked elemental layer process

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, B. J., E-mail: bjm.mueller@web.de [Robert Bosch GmbH, Corporate Research and Advance Engineering, Advanced Functional Materials and Microsystems, D-70839 Gerlingen (Germany); Institute of Micro- and Nanomaterials, University of Ulm, D-89081 Ulm (Germany); Zimmermann, C.; Haug, V., E-mail: veronika.haug@de.bosch.com; Koehler, T.; Zweigart, S. [Robert Bosch GmbH, Corporate Research and Advance Engineering, Advanced Functional Materials and Microsystems, D-70839 Gerlingen (Germany); Hergert, F. [Bosch Solar CISTech GmbH, D-14772 Brandenburg (Germany); Herr, U., E-mail: ulrich.herr@uni-ulm.de [Institute of Micro- and Nanomaterials, University of Ulm, D-89081 Ulm (Germany)

    2014-11-07

    In this study, we investigate the effect of different elemental selenium to elemental sulfur ratios on the chalcopyrite phase formation in Cu(In,Ga)(S,Se){sub 2} thin films. The films are formed by the stacked elemental layer process. The structural and electronic properties of the thin films and solar cells are analyzed by means of scanning electron microscopy, glow discharge optical emission spectrometry, X-ray diffraction, X-ray fluorescence, Raman spectroscopy, spectral photoluminescence as well as current-voltage, and quantum efficiency measurements. The influence of different S/(S+Se) ratios on the anion incorporation and on the Ga/In distribution is investigated. We find a homogenous sulfur concentration profile inside the film from the top surface to the bottom. External quantum efficiency measurements show that the band edge of the solar cell device is shifted to shorter wavelength, which enhances the open-circuit voltages. The relative increase of the open-circuit voltage with S/(S+Se) ratio is lower than expected from the band gap energy trend, which is attributed to the presence of S-induced defects. We also observe a linear decrease of the short-circuit current density with increasing S/(S+Se) ratio which can be explained by a reduced absorption. Above a critical S/(S+Se) ratio of around 0.61, the fill factor drops drastically, which is accompanied by a strong series resistance increase which may be attributed to changes in the back contact or p-n junction properties.

  14. Electrocatalytic Activity and Stability of M-Fe Catalysts Synthesized by Polymer Complex Method for PEFC Cathode

    KAUST Repository

    Ou, Yiwei

    2011-11-01

    The polymerized complex (PC) method was used to synthesize highly dispersed iron-based catalysts for the oxygen reduction reaction (ORR). The catalysts were prepared with an addition of 1,10-phenanthroline (Phen) and transition metals (M), such as Ta, Ti, and W, in an attempt to enhance the ORR activity and durability of the catalysts. The composition and properties of the catalysts were characterized by thermogravimetric analysis, X-ray diffraction, and X-ray photoelectron spectroscopy. The catalyst components, after extensive dissolution in a strong acid solution, were characterized by inductively coupled plasma mass spectroscopy and ultraviolet-visible spectroscopy. It was found that the Ti-Fe catalyst showed improved ORR performance, and the Ta-Fe catalyst showed enhanced stability towards ORR in acidic solution. The catalytic activity and stability for ORR was observed by adding Ti or Ta into the catalyst formulation, suggesting that the interaction between added hetero-ions (Ti and Ta) and ionic Fe active sites was beneficial for the ORR. A single-cell test with the synthesized catalyst in the cathode initially generated a high power density, but the low stability remains an issue to be solved.

  15. Reduction of Pt Usage in Fuel Cell Electrocatalysts Using Carbon Nanotubes and Non-Pt Metals

    Institute of Scientific and Technical Information of China (English)

    J. Nakamura; Y. Nagashima; T. Yamazaki; T. Matsumoto; E. Yoo

    2005-01-01

    @@ 1Introduction The high-priced and limited Pt constitutes a high barrier to commercialization of fuel cells. Pt is essential for the electrode catalyst of polymer electrolyte fuel cells (PEFCs). A reduction in Pt usage is one of the key requirements for the commercialization of fuel cells for use in everyday life, because of its high price and limited availability, and the difficulty of finding suitable substitutes. Non-Pt fuel cell catalysts will decrease the demand for Pt by PEFCs, enabling more Pt to be available for use in other essential products, and make fuel cells more popular[1]. The cheaper Mo2C is known to possess similar catalytic activities and electronic structures to Pt[2]. Carbon black (CB) is widely used as the support for Pt nanoparticles. However, we found that when carbon nanotubes (CNTs) rather than CB are used as the support, the performance is improved, especially below 600 mA/cm2[3,4]. Here, we show that a combination of Mo2C catalyst and carbon nanotubes in the anode provides performance as high as half that of the current PEFCs with Pt catalysts below 600mA/cm2.

  16. Self-Adjusting Stack Machines

    CERN Document Server

    Hammer, Matthew A; Chen, Yan; Acar, Umut A

    2011-01-01

    Self-adjusting computation offers a language-based approach to writing programs that automatically respond to dynamically changing data. Recent work made significant progress in developing sound semantics and associated implementations of self-adjusting computation for high-level, functional languages. These techniques, however, do not address issues that arise for low-level languages, i.e., stack-based imperative languages that lack strong type systems and automatic memory management. In this paper, we describe techniques for self-adjusting computation which are suitable for low-level languages. Necessarily, we take a different approach than previous work: instead of starting with a high-level language with additional primitives to support self-adjusting computation, we start with a low-level intermediate language, whose semantics is given by a stack-based abstract machine. We prove that this semantics is sound: it always updates computations in a way that is consistent with full reevaluation. We give a comp...

  17. Temperature and flow distribution in planar SOFC stacks

    Directory of Open Access Journals (Sweden)

    Monica Østenstad

    1995-07-01

    Full Text Available Simulation of a planar Solid Oxide Fuel Cell stack requires the solution of the mass balances of the chemical species, the energy balances, the charge balance and the channel flow equations in order to compute the species concentrations, the temperature distributions, the current density and the channel flows. The unit cell geometry can be taken into account by combining detailed modeling of a unit cell with a homogenized model of a whole stack. In this study the effect of the asymmetric temperature distribution on the channel flows in a conventional cross-flow design has been investigated. The bidirectional cross-flow design is introduced, for which we can show more directional temperature and flow distributions.

  18. Gate stack technology for nanoscale devices

    Directory of Open Access Journals (Sweden)

    Byoung Hun Lee

    2006-06-01

    Full Text Available Scaling of the gate stack has been a key to enhancing the performance of complementary metal-oxide-semiconductor (CMOS field-effect transistors (FETs of past technology generations. Because the rate of gate stack scaling has diminished in recent years, the motivation for alternative gate stacks or novel device structures has increased considerably. Intense research during the last decade has led to the development of high dielectric constant (k gate stacks that match the performance of conventional SiO2-based gate dielectrics. However, many challenges remain before alternative gate stacks can be introduced into mainstream technology. We review the current status of and challenges in gate stack research for planar CMOS devices and alternative device technologies to provide insights for future research.

  19. Diagnosis of PEMFC stack failures via electrochemical impedance spectroscopy

    Science.gov (United States)

    Merida-Donis, Walter Roberto

    Two failure modes related to water management in Proton Exchange Membrane fuel cells (dehydration and flooding) were investigated using electrochemical impedance spectroscopy as a diagnosis tool. It was hypothesised that each failure mode corresponds to changes in the overall stack impedance that are observable in different frequency ranges. This hypothesis was corroborated experimentally. The experimental implementation required new testing hardware and techniques. A four-cell stack capable of delivering individually conditioned reactants to each cell was designed, built, tested, and characterised under a variety of operating conditions. This stack is the first reported prototype of its type. The stack was used to perform galvanostatic, impedance measurements in situ. The measurements were made at three different temperatures (62, 70 and 80°C), covering the current density range 0.1 to 1.0 A cm-2 , and the frequency range 0.1 to 4 x 105 Hz. The recorded data represent the first reported set of measurements covering these ranges. The failure modes were simulated on individual cells within the stack. The effects on individual cell and stack impedance were studied by measuring the changes in stack and cell impedances under flooding or dehydration conditions. Dehydration effects were measurable over a wide frequency range (0.5 to 105 Hz). In contrast, flooding effects were measurable in a narrower frequency range (0.5 to 102 Hz). Using these results, separate or concurrent impedance measurements in these frequency ranges (or narrow bands thereof) can be used to discern and identify the two failure modes quasi-instantaneously. Such detection was not possible with pre-existing, do techniques. The measured spectra were modelled by a simple equivalent circuit whose time constants corresponded to ideal (RC) and distributed (Warburg) components. The model was robust enough to fit all the measured spectra (for single cells and the stack), under normal and simulated

  20. Fabrication techniques and stack assembling methods for micro tubular solid oxide fuel cells%微管式固体氧化物燃料电池制备技术及电堆组装工艺

    Institute of Scientific and Technical Information of China (English)

    孟秀霞; 杨乃涛; 尹屹梅; 谭小耀; 马紫峰

    2011-01-01

    微管式固体氧化物燃料电池(MT-SOFC)能显著减小固体氧化物燃料电池(SOFC)的体积,微型化结构使其传质、传热和反应效率明显提高,可实现快速启动与关闭,易于移动和携带.本文概述了微管式固体氧化物燃料电池的结构、关键制备工艺、研究现状、存在问题和应用前景.对电解质支撑型、阳极支撑型及阴极支撑型MT-SOFC结构和性能进行了分析比较,介绍了等静压成型、挤出成型和相转化纺丝法制备陶瓷中空纤维的技术,综述了微管负载型电解质膜技术和微管电池堆组装技术,并对MT-SOFC发展方向及在便携电源、汽车动力电源和微反应器领域的应用进行了展望.%Micro tubular solid oxide fuel cells (MT-SOFCs) have not only the inherent benefits of SOFCs, but exhibit new advantages over conventional SOFCs, such as higher mass transfer/heat transfer, higher reaction efficiency, rapid start-up/shut-down and significantly reduced volume. Therefore, MT-SOFCs show potential applications in portable and mobile power sources. This paper reviews the progress of MT-SOFC studies, focusing on the properties, structures, and fabrications of the cells. The structures and performances of MT-SOFCs supported with electrolyte, anode and cathode respectively are compared and analyzed. The key step for fabrication of MT-SOFCs is the preparation of micro tubes using methods such as isostatic pressing, plastic extrusion and phase inversion spinning methods for hollow fiber ceramics. Preparation of dense electrolyte membrane and assembling of cell stacks are discussed. The challenges and potential applications of MT-SOFCs in portable power sources, electric vehicles and micro reactors are also highlighted.

  1. Flexural characteristics of a stack leg

    International Nuclear Information System (INIS)

    A 30 MV tandem Van de Graaff accelerator is at present under construction at Daresbury Laboratory. The insulating stack of the machine is of modular construction, each module being 860 mm in length. Each live section stack module contains 8 insulating legs mounted between bulkhead rings. The design, fabrication (from glass discs bonded to stainless steel discs using an epoxy film adhesive) and testing of the stack legs is described. (U.K.)

  2. Hydrogen Embrittlement And Stacking-Fault Energies

    Science.gov (United States)

    Parr, R. A.; Johnson, M. H.; Davis, J. H.; Oh, T. K.

    1988-01-01

    Embrittlement in Ni/Cu alloys appears related to stacking-fault porbabilities. Report describes attempt to show a correlation between stacking-fault energy of different Ni/Cu alloys and susceptibility to hydrogen embrittlement. Correlation could lead to more fundamental understanding and method of predicting susceptibility of given Ni/Cu alloy form stacking-fault energies calculated from X-ray diffraction measurements.

  3. The untyped stack calculus and Bohm's theorem

    OpenAIRE

    Alberto Carraro

    2013-01-01

    The stack calculus is a functional language in which is in a Curry-Howard correspondence with classical logic. It enjoys confluence but, as well as Parigot's lambda-mu, does not admit the Bohm Theorem, typical of the lambda-calculus. We present a simple extension of stack calculus which is for the stack calculus what Saurin's Lambda-mu is for lambda-mu.

  4. Demagnetizing effects in stacked rectangular prisms

    DEFF Research Database (Denmark)

    Christensen, Dennis; Nielsen, Kaspar Kirstein; Bahl, Christian Robert Haffenden;

    2011-01-01

    configuration, temperature distribution and applied magnetic field. In this paper the model is applied to the case of a stack of parallel, ferromagnetic rectangular prisms and the resulting internal field is found as a function of the orientation of the applied field, the number of prisms in the stack, the...... spacing between the prisms and the packing density of the stack. The results show that the resulting internal field is far from being equal to the applied field and that the various stack configurations investigated affect the resulting internal field significantly and non-linearly. The results have a...

  5. Progress in SLIP stacking and barrier bucket

    International Nuclear Information System (INIS)

    The slip stacking for pbar production has been operational in the Main Injector(MI) since December 2004 and has increased the beam intensity on the pbar target by more than 60%. We plan to use slip stacking for the NuMI neutrino experiment to effectively increasing the beam intensity to NuMI target by about a factor two in a MI cycle. In parallel with slip stacking, we plan to study fast momentum stacking using barrier buckets. One barrier rf system has been installed and tested, and a second system is being installed during the current shutdown. (author)

  6. A Time-predictable Stack Cache

    DEFF Research Database (Denmark)

    Abbaspour, Sahar; Brandner, Florian; Schoeberl, Martin

    2013-01-01

    precise results of the cache analysis part of the WCET analysis. Splitting the data cache for different data areas enables composable data cache analysis. The WCET analysis tool can analyze the accesses to these different data areas independently. In this paper we present the design and implementation...... of a cache for stack allocated data. Our port of the LLVM C++ compiler supports the management of the stack cache. The combination of stack cache instructions and the hardware implementation of the stack cache is a further step towards timepredictable architectures....

  7. Ball Bearing Stacking Automation System

    Directory of Open Access Journals (Sweden)

    Shafeequerrahman S . Ahmed

    2013-01-01

    Full Text Available This document is an effort to introduce the concept of automation in small scale industries and or small workshops that are involved in the manufacturing of small objects such as nuts, bolts and ball bearing in this case. This an electromechanical system which includes certain mechanical parts that involves one base stand on which one vertical metallic frame is mounted and hinged to this vertical stand is an in humanized effort seems inadequate in this era making necessary the use of Electronics, Computer in the manufacturing processes leading to the concept of Automated Manufacturing System (AMS.The ball bearing stack automation is an effort in this regard. In our project we go for stack automation for any object for example a ball bearing, be that is still a manual system there. It will be microcontroller based project control system equipped with microcontroller 89C51 from any manufacturer like Atmel or Philips. This could have been easily implemented if a PLC could be used for manufacturing the staking unit but I adopted the microcontroller based system so that some more modification in the system can be effected at will as to use the same hardware .Although a very small object i.e. ball bearig or small nut and fixture will be tried to be stacked, the system with more precision and more power handling capacity could be built for various requirements of the industry. For increasing more control capacity, we can use another module of this series. When the bearing is ready, it will be sent for packing. This is sensed by an inductive sensor. The output will be proceeds by PLC and microcontroller card which will be driving the assembly in order to put it into pads or flaps. This project will also count the total number of bearings to be packed and will display it on a LCD for real time reference and a provision is made using a higher level language using hyper terminal of the computer

  8. Comparison of spatial harmonics in infinite and finite Bragg stacks for metamaterial homogenization

    DEFF Research Database (Denmark)

    Clausen, Niels Christian Jerichau; Arslanagic, Samel; Breinbjerg, Olav

    2014-01-01

    Metamaterial homogenization may be based on the dominance of a single Floquet-Bloch spatial harmonic in an infinite periodic structure - with the dominance quantified in terms of the relative magnitude of the associated spatial harmonic Poynting vector. For the corresponding finite structure...... of the corresponding infinite Bragg stack. This is even the case for finite Bragg stacks having only two unit cells; thus, the number of unit cells does not influence the homogenizability of this type of configuration. ©...

  9. Estimation of localized current anomalies in polymer electrolyte fuel cells from magnetic flux density measurements

    Science.gov (United States)

    Nara, Takaaki; Koike, Masanori; Ando, Shigeru; Gotoh, Yuji; Izumi, Masaaki

    2016-05-01

    In this paper, we propose novel inversion methods to estimate defects or localized current anomalies in membrane electrode assemblies (MEAs) in polymer electrolyte fuel cells (PEFCs). One method is an imaging approach with L1-norm regularization that is suitable for estimation of focal anomalies compared to Tikhonov regularization. The second is a complex analysis based method in which multiple pointwise current anomalies can be identified directly and algebraically from the measured magnetic flux density.

  10. Surface Analytical Methods for the Development of Electrochemical Components of Polymer Electrolyte Fuel Cells

    OpenAIRE

    Biswas, Indro; Gazdzicki, Pawel; Schulze, Mathias

    2013-01-01

    The transition from fossil to renewable energies implies significant changes in the energy system regarding the distribution, storage and energy conversion due to the intrinsic natural fluctuations of renewable power sources. Polymer electrolyte fuel cells (PEFC) are highly efficient electrochemical energy converters that may be implemented in a wide range of power and dynamics. Their high gravimetric energy density makes them attractive for many applications, especially for mobile purpos...

  11. Stacks of SPS Dipole Magnets

    CERN Multimedia

    1974-01-01

    Stacks of SPS Dipole Magnets ready for installation in the tunnel. The SPS uses a separated function lattice with dipoles for bending and quadrupoles for focusing. The 6.2 m long normal conducting dipoles are of H-type with coils that are bent-up at the ends. There are two types, B1 (total of 360) and B2 (384). Both are for a maximum field of 1.8 Tesla and have the same outer dimensions (450x800 mm2 vxh) but with different gaps (B1: 39x129 mm2, B2: 52x92 mm2) tailored to the beam size. The yoke, made of 1.5 mm thick laminations, consists of an upper and a lower half joined together in the median plane once the coils have been inserted.

  12. Investigation of degradation effects in polymer electrolyte fuel cells under automotive-related operating conditions

    Science.gov (United States)

    Enz, S.; Dao, T. A.; Messerschmidt, M.; Scholta, J.

    2015-01-01

    The influence of artificial starvation effects during automotive-related operating conditions is investigated within a polymer electrolyte fuel cell (PEFC) using non-dispersive infrared sensors and a current scan shunt. Driving cycles (DC) and single load change experiments are performed with specific fuel and oxidant starvation conditions. Within the DC experiments, a maximal CO2 amount of 4.67 μmol per cycle is detected in the cathode and 0.97 μmol per cycle in the anode exhaust without reaching fuel starvation conditions during the DC. Massive cell reversal conditions occur within the single load change experiments as a result of anodic fuel starvation. As soon as a fuel starvation appears, the emitted CO2 increases exponentially in the anode and cathode exhaust. A maximal CO2 amount of 143.8 μmol CO2 on the anode side and 5.8 μmol CO2 on the cathode side is detected in the exhaust gases. The critical cell reversal conditions only occur by using hydrogen reformate as anode reactant. The influence of the starvation effects on the PEFC performance is investigated via polarization curves, cyclic and linear sweep voltammetry as well as electrochemical impedance spectroscopy. The PEFC performance is reduced by 47% as a consequence of the dynamic operation.

  13. Detailed experimental characterization of a reformate fuelled PEM stack

    DEFF Research Database (Denmark)

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

    2006-01-01

    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 with...... electric power output from 1-3-kW. All process inputs for the stack can be altered to provide realistic performance analyses, corresponding to those encountered in field applications. These include cathode/anode dew point control, cathode flow rate, cooling water temperature control as well as synthesis...... gas mixing (CO, CO2, N2, Air and H2). The control system includes 12 thermocouple inputs, up to 60 cell voltages, more than 10 flow measurements and 10 pressure measurements, all at sample rates up to 1 kHz. The system design is thoroughly explained to provide valuable information for system...

  14. Project W-420 stack monitoring system upgrades

    International Nuclear Information System (INIS)

    This project will execute the design, procurement, construction, startup, and turnover activities for upgrades to the stack monitoring system on selected Tank Waste Remediation System (TWRS) ventilation systems. In this plan, the technical, schedule, and cost baselines are identified, and the roles and responsibilities of project participants are defined for managing the Stack Monitoring System Upgrades, Project W-420

  15. Demagnetizing effects in stacked rectangular prisms

    International Nuclear Information System (INIS)

    A numerical, magnetostatic model of the internal magnetic field of a rectangular prism is extended to the case of a stack of rectangular prisms. The model enables the calculation of the spatially resolved, three-dimensional internal field in such a stack given any magnetic state function, stack configuration, temperature distribution and applied magnetic field. In this paper the model is applied to the case of a stack of parallel, ferromagnetic rectangular prisms and the resulting internal field is found as a function of the orientation of the applied field, the number of prisms in the stack, the spacing between the prisms and the packing density of the stack. The results show that the resulting internal field is far from being equal to the applied field and that the various stack configurations investigated affect the resulting internal field significantly and non-linearly. The results have a direct impact on the design of, e.g., active magnetic regenerators made of stacked rectangular prisms in terms of optimizing the internal field.

  16. Learning OpenStack networking (Neutron)

    CERN Document Server

    Denton, James

    2014-01-01

    If you are an OpenStack-based cloud operator with experience in OpenStack Compute and nova-network but are new to Neutron networking, then this book is for you. Some networking experience is recommended, and a physical network infrastructure is required to provide connectivity to instances and other network resources configured in the book.

  17. Excitation transfer in stacked quantum dot chains

    International Nuclear Information System (INIS)

    Stacked InAs quantum dot chains (QDCs) on InGaAs/GaAs cross-hatch pattern (CHP) templates yield a rich emission spectrum with an unusual carrier transfer characteristic compared to conventional quantum dot (QD) stacks. The photoluminescent spectra of the controlled, single QDC layer comprise multiple peaks from the orthogonal QDCs, the free-standing QDs, the CHP, the wetting layers and the GaAs substrate. When the QDC layers are stacked, employing a 10 nm GaAs spacer between adjacent QDC layers, the PL spectra are dominated by the top-most stack, indicating that the QDC layers are nominally uncoupled. Under high excitation power densities when the high-energy peaks of the top stack are saturated, however, low-energy PL peaks from the bottom stacks emerge as a result of carrier transfers across the GaAs spacers. These unique PL signatures contrast with the state-filling effects in conventional, coupled QD stacks and serve as a means to quickly assess the presence of electronic coupling in stacks of dissimilar-sized nanostructures. (paper)

  18. Do Stack Traces Help Developers Fix Bugs?

    NARCIS (Netherlands)

    Schröter, A.; Bettenburg, N.; Premraj, R.

    2010-01-01

    A widely shared belief in the software engineering community is that stack traces are much sought after by developers to support them in debugging. But limited empirical evidence is available to confirm the value of stack traces to developers. In this paper, we seek to provide such evidence by condu

  19. Stacking technology for a space constrained microsystem

    DEFF Research Database (Denmark)

    Heschel, Matthias; Kuhmann, Jochen Friedrich; Bouwstra, Siebe;

    1998-01-01

    In this paper we present a stacking technology for an integrated packaging of an intelligent transducer which is formed by a micromachined silicon transducer and an integrated circuit chip. Transducer and circuitry are stacked on top of each other with an intermediate chip in between. The bonding...

  20. 49 CFR 178.815 - Stacking test.

    Science.gov (United States)

    2010-10-01

    ... qualification of all IBC design types intended to be stacked. (b) Special preparation for the stacking test. (1) All IBCs except flexible IBC design types must be loaded to their maximum permissible gross mass. (2) The flexible IBC must be filled to not less than 95 percent of its capacity and to its maximum...

  1. Simulation and Optimization of Air-Cooled PEMFC Stack for Lightweight Hybrid Vehicle Application

    Directory of Open Access Journals (Sweden)

    Jingming Liang

    2015-01-01

    Full Text Available A model of 2 kW air-cooled proton exchange membrane fuel cell (PEMFC stack has been built based upon the application of lightweight hybrid vehicle after analyzing the characteristics of heat transfer of the air-cooled stack. Different dissipating models of the air-cooled stack have been simulated and an optimal simulation model for air-cooled stack called convection heat transfer (CHT model has been figured out by applying the computational fluid dynamics (CFD software, based on which, the structure of the air-cooled stack has been optimized by adding irregular cooling fins at the end of the stack. According to the simulation result, the temperature of the stack has been equally distributed, reducing the cooling density and saving energy. Finally, the 2 kW hydrogen-air air-cooled PEMFC stack is manufactured and tested by comparing the simulation data which is to find out its operating regulations in order to further optimize its structure.

  2. Partially Perfluorinated Hydrocarbon Ionomer for Cathode Catalyst Layer of Polymer Electrolyte Membrane Fuel Cell

    International Nuclear Information System (INIS)

    Hydrocarbon ionomers have not been successfully employed in the cathode of polymer electrolyte fuel cell (PEFC)s due to their low oxygen permeabilities. In this work, we propose a partially fluorinated aromatic polyether with sulfonic acid groups (s-PFPE) as an ionomer for the cathode catalyst layer. Compared to sulfonated poly(ether ether ketone) (s-PEEK), it exhibited more than 1.5 times higher oxygen permeability at RH 40% and 1.3 times higher at RH 100%. The catalyst layer based on s-PFPE showed higher power performance than that based on s-PEEK owing to enhanced oxygen transport and fast proton conduction through the s-PFPE ionomer phase covering the catalyst layer. We demonstrate that the introduction of the perfluorinated moieties to the hydrocarbon backbone is an effective strategy for the use of hydrocarbon ionomer in the cathode of PEMFCs

  3. Interpretation of the current-voltage characteristics of polymer electrolyte fuel cells by impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Andreaus, B.; McEvoy, A.J.; Scherer, G.

    2003-03-01

    We applied electrochemical impedance spectroscopy (EIS) to elucidate the origins of the voltage losses of a H{sub 2} /O{sub 2} polymer electrolyte fuel cell (PEFC) as a function of current density. The results indicate that the commercial electrodes utilized in these experiments suffer from a substantial loss in active catalyst sur-face already at relatively low current densities. The drying out of the electrolyte in the membrane adjacent to the anode as well as in the anode active layer results in an additional voltage loss at high current densities. Therefore, the purely structural aspects of a robust triple phase boundary sustaining harsh conditions under load is at least equally important as the proper choice of catalyst for a high performance PEFC-electrode. (author)

  4. Barrier RF stacking at Fermilab

    International Nuclear Information System (INIS)

    A key issue to upgrade the luminosity of the Tevatron Run2 program and to meet the neutrino requirement of the NuMI experiment at Fermilab is to increase the proton intensity on the target. This paper introduces a new scheme to double the number of protons FR-om the Main Injector (MI) to the pbar production target (Run2) and to the pion production target (NuMI). It is based on the fact that the MI momentum acceptance is about a factor of four larger than the momentum spread of the Booster beam. Two RF barriers--one fixed, another moving--are employed to confine the proton beam. The Booster beams are injected off-momentum into the MI and are continuously reflected and compressed by the two barriers. Calculations and simulations show that this scheme could work provided that the Booster beam momentum spread can be kept under control. Compared with slip stacking, a main advantage of this new method is small beam loading effect thanks to the low peak beam current. The RF barriers can be generated by an inductive device, which uses nanocrystal magnet alloy (Finemet) cores and fast high voltage MOSFET switches. This device has been designed and fabricated by a Fermilab-KEK-Caltech team. The first bench test was successful. Beam experiments are being planned

  5. Pi-stacked interactions in explosive crystals: buffers against external mechanical stimuli.

    Science.gov (United States)

    Zhang, Chaoyang; Wang, Xiaochuan; Huang, Hui

    2008-07-01

    The pi-stacked interactions in some explosive crystal packing are discussed. Taking a typical pi-stacked explosive 2,4,6-trinitrobenzene-1,3,5-triamine (TATB) as a sample and using molecular simulations, we investigated the nature of the pi-stacked interactions versus the external mechanical stimuli causing possible slide and compression of explosives. As a result, between the neighbor layers in the TATB unit cell, the electrostatic attraction decreases with a little decrease of vdW attraction when its top layer slides, whereas the vdW attraction increases with a decrease of electrostatic attraction when TATB crystal is compressed along its c axis. Meanwhile, we studied the correlation between the pi-stacked structures and the impact sensitivities of explosives by means of three representatives including TATB with typical planar pi-stacked structures, 2,2-dinitroethylene-1,1-diamine (Fox-7) with wavelike pi-stacked structures, and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) without pi-stacked structure. The results showed that pi-stacked structures, particularly planar layers, can effectively buffer against external mechanical stimuli. That is, pi-stacked structures can partly convert the mechanical energy acting on them into their intermolecular interaction energy, to avoid the increase of the molecular vibration resulting in the explosive decomposition, the formation of hot spots, and the final detonation. This is another reason for the low mechanical sensitivity of pi-stacked explosives besides their stable conjugated molecular structures. PMID:18529058

  6. Density of oxidation-induced stacking faults in damaged silicon

    NARCIS (Netherlands)

    Kuper, F.G.; Hosson, J.Th.M. De; Verwey, J.F.

    1986-01-01

    A model for the relation between density and length of oxidation-induced stacking faults on damaged silicon surfaces is proposed, based on interactions of stacking faults with dislocations and neighboring stacking faults. The model agrees with experiments.

  7. Technology watch of fuel cells for vehicles in 2012; Teknikbevakning av braensleceller foer fordon 2012

    Energy Technology Data Exchange (ETDEWEB)

    Pohl, Hans

    2013-03-15

    The report presents results from an international survey covering the status and development of tractionary fuel cells. Interviews, study visits, reports, journals, media coverage and participation in IEA Advanced Fuel Cells Annex 26 have served as main sources of information. The development in Korea has been devoted particular attention this period. The report covers the development during the second part of 2011 and the whole 2012. The transport sector must change to provide mobility for people and goods in a long-term sustainable way. Fuel cell technology offers an important opportunity for the vehicle manufacturer and the vehicle user to maintain the same level of performance, comfort and versatility without compromising the sustainability requirements. Fuel cell vehicles typically use polymer electrolyte fuel cells (PEFC) and pressurized hydrogen. They also use tractionary batteries for about the same reasons as other hybrid electric vehicles. For commercial vehicles fuel cells are developed for the production of auxiliary power, to be used when the vehicles are parked, for example. Until 2015, Hyundai aims at making up to 1,000 fuel cell vehicles. After 2015 the plan is for several thousand every year. Until 2025, Hyundai aims at a total delivery of more than 100,000 fuel cell vehicles and the technology is then expected to be fully competitive. A roadmap shows that Korea until 2015 has established 43 and until 2030, a total of 500 hydrogen refuelling stations are indicated. The Skaane Region has carried out the first Swedish procurement of fuel cell vehicles. Two Hyundai iX35 FCEV were purchased for delivery 2013. In addition, the city of Copenhagen has purchased 15 such vehicles. During the next few years three hydrogen refuelling stations will be established in the Copenhagen area. January 2012, the California Air Resources Board decided the new set of regulations Advanced Clean Cars. It comprises three parts; tailpipe emissions and greenhouse gases, Zero

  8. Thermal and Electrochemical Performance of a High-Temperature Steam Electrolysis Stack

    Energy Technology Data Exchange (ETDEWEB)

    J. O' Brien; C. Stoots; G. Hawkes; J. Hartvigsen

    2006-11-01

    A research program is under way at the Idaho National Laboratory (INL) to simultaneously address the research and scale-up issues associated with the implementation of solid-oxide electrolysis cell technology for hydrogen production from steam. We are conducting a progression of electrolysis stack testing activities, at increasing scales, along with a continuation of supporting research activities in the areas of materials development, single-cell testing, detailed computational fluid dynamics (CFD) and systems modeling. This paper will present recent experimental results obtained from testing of planar solid-oxide stacks operating in the electrolysis mode. The hydrogen-production and electrochemical performance of these stacks will be presented, over a range of operating conditions. In addition, internal stack temperature measurements will be presented, with comparisons to computational fluid dynamic predictions.

  9. Dynamical Stability of Slip-stacking Particles

    CERN Document Server

    Eldred, Jeffrey

    2014-01-01

    We study the stability of particles in slip-stacking configuration, used to nearly double proton beam intensity at Fermilab. We introduce universal area factors to calculate the available phase space area for any set of beam parameters without individual simulation. We find perturbative solutions for stable particle trajectories. We establish Booster beam quality requirements to achieve 97\\% slip-stacking efficiency. We show that slip-stacking dynamics directly correspond to the driven pendulum and to the system of two standing-wave traps moving with respect to each other.

  10. Do Stack Traces Help Developers Fix Bugs?

    OpenAIRE

    Schröter, A; Bettenburg, N.; Premraj, R

    2010-01-01

    A widely shared belief in the software engineering community is that stack traces are much sought after by developers to support them in debugging. But limited empirical evidence is available to confirm the value of stack traces to developers. In this paper, we seek to provide such evidence by conducting an empirical study on the usage of stack traces by developers from the ECLIPSE project. Our results provide strong evidence to this effect and also throws light on some of the patterns in bug...

  11. Capping stack: An industry in the making

    Institute of Scientific and Technical Information of China (English)

    Jack Chen; Li Xunke; Xie Wenhui; Kang Yongtian

    2013-01-01

    This paper gives an overview of recent development of the marine well containment system (MWCS)after BP Macondo subsea well blowout occurred on April 20,2010 in the Gulf of Mexico.Capping stack,a hardware utilized to contain blowout well at or near the wellhead is the center piece of MWCS.Accessibility to the dedicated capping stacks is gradually becoming a pre-requirement to obtain the permit for offshore drilling/workover,and the industry for manufacturing,maintenance,transportation and operation of the capping stack is in the making.

  12. Separated Control and Data Stacks to Mitigate Buffer Overflow Exploits

    OpenAIRE

    Christopher Kugler; Tilo Müller

    2015-01-01

    Despite the fact that protection mechanisms like StackGuard, ASLR and NX are widespread, the development on new defense strategies against stack-based buffer overflows has not yet come to an end. In this article, we present a novel compiler-level protection called SCADS: Separated Control and Data Stacks that protects return addresses and saved frame pointers on a separate stack, called the control stack. In common computer programs, a single user mode stack is used to store control informati...

  13. Numerical study of droplet dynamics in a polymer electrolyte fuel cell gas channel using an embedded Eulerian-Lagrangian approach

    Science.gov (United States)

    Jarauta, Alex; Ryzhakov, Pavel; Secanell, Marc; Waghmare, Prashant R.; Pons-Prats, Jordi

    2016-08-01

    An embedded Eulerian-Lagrangian formulation for the simulation of droplet dynamics within a polymer electrolyte fuel cell (PEFC) channel is presented. Air is modeled using an Eulerian formulation, whereas water is described with a Lagrangian framework. Using this framework, the gas-liquid interface can be accurately identified. The surface tension force is computed using the curvature defined by the boundary of the Lagrangian mesh. The method naturally accounts for material property changes across the interface and accurately represents the pressure discontinuity. A sessile drop in a horizontal surface, a sessile drop in an inclined plane and droplets in a PEFC channel are solved for as numerical examples and compared to experimental data. Numerical results are in excellent agreement with experimental data. Numerical results are also compared to results obtained with the semi-analytical model previously developed by the authors in order to discuss the limitations of the semi-analytical approach.

  14. A Dynamic Elimination-Combining Stack Algorithm

    CERN Document Server

    Bar-Nissan, Gal; Suissa, Adi

    2011-01-01

    Two key synchronization paradigms for the construction of scalable concurrent data-structures are software combining and elimination. Elimination-based concurrent data-structures allow operations with reverse semantics (such as push and pop stack operations) to "collide" and exchange values without having to access a central location. Software combining, on the other hand, is effective when colliding operations have identical semantics: when a pair of threads performing operations with identical semantics collide, the task of performing the combined set of operations is delegated to one of the threads and the other thread waits for its operation(s) to be performed. Applying this mechanism iteratively can reduce memory contention and increase throughput. The most highly scalable prior concurrent stack algorithm is the elimination-backoff stack. The elimination-backoff stack provides high parallelism for symmetric workloads in which the numbers of push and pop operations are roughly equal, but its performance d...

  15. Turing Impossibility Properties for Stack Machine Programming

    NARCIS (Netherlands)

    J.A. Bergstra; C.A. Middelburg

    2012-01-01

    The strong, intermediate, and weak Turing impossibility properties are introduced. Some facts concerning Turing impossibility for stack machine programming are trivially adapted from previous work. Several intriguing questions are raised about the Turing impossibility properties concerning different

  16. The stack on software and sovereignty

    CERN Document Server

    Bratton, Benjamin H

    2016-01-01

    A comprehensive political and design theory of planetary-scale computation proposing that The Stack -- an accidental megastructure -- is both a technological apparatus and a model for a new geopolitical architecture.

  17. Characterization of Piezoelectric Stacks for Space Applications

    Science.gov (United States)

    Sherrit, Stewart; Jones, Christopher; Aldrich, Jack; Blodget, Chad; Bao, Xiaoqi; Badescu, Mircea; Bar-Cohen, Yoseph

    2008-01-01

    Future NASA missions are increasingly seeking to actuate mechanisms to precision levels in the nanometer range and below. Co-fired multilayer piezoelectric stacks offer the required actuation precision that is needed for such mechanisms. To obtain performance statistics and determine reliability for extended use, sets of commercial PZT stacks were tested in various AC and DC conditions at both nominal and high temperatures and voltages. In order to study the lifetime performance of these stacks, five actuators were driven sinusoidally for up to ten billion cycles. An automated data acquisition system was developed and implemented to monitor each stack's electrical current and voltage waveforms over the life of the test. As part of the monitoring tests, the displacement, impedance, capacitance and leakage current were measured to assess the operation degradation. This paper presents some of the results of this effort.

  18. Exploring online evolution of network stacks

    OpenAIRE

    Imai, Pierre

    2013-01-01

    Network stacks today follow a one-size-fits-all philosophy. They are mostly kept unmodified due to often prohibitive costs of engineering, deploying and administrating customisation of the networking software, with the Internet stack architecture still largely being based on designs and assumptions made for the ARPANET 40 years ago. We venture that heterogeneous and rapidly changing networks of the future require, in order to be successful, run-time self-adaptation mechanisms at different tim...

  19. Opacity of nitrogen dioxide stack plumes

    International Nuclear Information System (INIS)

    Removal of the NO2 from process off-gases would enable the Purex Plant to comply with the opacity standards for air pollution control. However, a relationship between stack opacity and NO2 content of the stack gases is needed in order to implement a cost effective NO2 control method. A test was conducted in which nitrogen dioxide (NO2) was injected into a 1.3 meter diameter, 150 foot tall stack. Certified visual opacity measurements over a range of 0 to 50 percent were recorded along with the corresponding concentrations of NO2 in the stack effluent. The visual opacity readings were found to be highly imprecise and from 2 to 3 times higher than opacities calculated on the basis of the light absorption parameters used for smoke opacity meters. Agreement was found between the test readings and visual opacity readings reported on 2.13 and 3.28 meter diameter stack when visual opacity was plotted as a function of NO2 concentration and effective stack diameter. The difference between calculated and visual opacity is attributed to a color contrast effect which increases the visual noticeability of the NO2 plume. Calculations based on color contrast show that visual opacity measurements are affected by sunlight conditions and the response of the human eye to color changes. This indicates that a variability in the NO2 emission limit will exist as long as visual opacity measurements are used as the basis for controlling stack discharges. Based on the analysis of the test data it is recommended that concentration limits rather than visual opacity measurements be used as a criteria for setting stack emissons. Concentration limits corresponding to a visual opacity limit can be determined by the appropriate opacity/ppM meter relationship and a formula which is given

  20. Stacking fault energy in some single crystals

    Institute of Scientific and Technical Information of China (English)

    Aditya M.Vora

    2012-01-01

    The stacking fault energy of single crystals has been reported using the peak shift method.Presently studied all single crystals are grown by using a direct vapor transport (DVT) technique in the laboratory.The structural characterizations of these crystals are made by XRD.Considerable variations are shown in deformation (α) and growth (β) probabilities in single crystals due to off-stoichiometry,which possesses the stacking fault in the single crystal.

  1. Stack Characterization System Development and Testing

    International Nuclear Information System (INIS)

    Oak Ridge National Laboratory, as well as the rest of the U.S. Department of Energy community, has numerous off-gas stacks that need to be decommissioned, demolished, and packaged for disposal. Disposal requires a waste disposition determination phase. Process knowledge typically makes a worst-case scenario decision that may place lower-level waste into a more expensive higher-level waste disposal category. Truly useful radiological and chemical sampling can be problematic on old stacks due to their inherent height and access hazards, and many of these stacks have begun to deteriorate structurally. A remote stack characterization system (SCS) that can manage sample and data collection removes people from the hazards and provides an opportunity for access to difficult to reach internal stack areas. The SCS is a remotely operated articulated radiological data recovery system designed to deploy down into off-gas stacks from the top via crane. The battery-powered SCS is designed to stabilize itself against the stack walls and move various data recovery systems into areas of interest on the inner stack walls. Stabilization is provided by a tripod structure; sensors are mounted in a rotatable bipod underneath the tripod. Sensors include a beta/gamma/alpha detector, a removable contaminant multi-sample automated sampler, and a multi-core remote core drill. Multiple cameras provide remote task viewing, support for sampling, and video documentation of the process. A delay in funding has delayed project delivery somewhat. Therefore, this paper describes the technology and shows fabrication and testing progress to the extent that data is available.

  2. Cosmic ray test of INO RPC stack

    International Nuclear Information System (INIS)

    The India-based Neutrino Observatory (INO) collaboration is planning to build a 50 kt magnetised iron calorimeter (ICAL) detector using glass Resistive Plate Chambers (RPCs) as active detector elements. A stack of 12 such glass RPCs of 1 m ×1 m in area is tracking cosmic ray muons for over three years. In this paper, we will review the constructional aspects of the stack and discuss the performance of the RPCs using this cosmic ray data.

  3. Fuel cells, electrolyzers, and microalgae photobioreactors: technologies for long-duration missions in human spaceflight

    Science.gov (United States)

    Belz, Stefan; Bretschneider, Jens; Nathanson, Emil; Buchert, Melanie

    Long-duration and far-distant missions in human spaceflight have higher requirements on life support systems (LSS) technologies than for missions into low Earth orbit (LEO). LSS technologies have to ensure that humans can survive, live, and work in space. Enhancements of existing technologies, new technological developments and synergetic components integration help to close the oxygen, water and carbon loops. For these reasons, the approach of a synergetic integration of Polymer Electrolyte Membrane Fuel Cells (PEFC), Polymer Electrolyte Membrane Electrolyzers (PEL) and Photobioreactors (PBR) for microalgae cultivation into the LSS is investigated. It is demonstrated in which mission scenarii the application of PEFC, PEL, and PBR are useful in terms of mass, reliability, and cycle closures. The paper represents the current status of research at the Institute of Space Systems (IRS) of University of Stuttgart on PEFC, PEL, and PBR development. A final configuration of a prototype of a PEFC system includes the gas, water, and thermal management. The PEL is a state-of-the-art technology for space application, but the specific requirements by a synergetic integration are focused. A prototype configuration of a PBR system, which was tested under microgravity conditions in a parabolic experiment, consists of a highly sophisticated cultivation chamber, adapted sensorics, pumps, nutrients supply and harvesting unit. Additionally, the latest results of the cultivation of the microalgae species Chlorella vulgaris and Scenedesmus obliquus in the laboratories of the IRS are represented. Both species are robust, nutrient-rich for human diet. An outlook of the next steps is given for in-orbit verification.

  4. Stacked subwavelength gratings for imaging polarimetry

    Science.gov (United States)

    Deguzman, Panfilo Castro

    The stacking of subwavelength gratings (SWG) in an integrated structure is presented for an application in imaging polarimetry. Imaging polarimetry extends the capability of conventional imaging by providing polarization information about a scene, in addition to variations in intensity. In this dissertation, a novel approach is introduced to develop a real-time imaging polarimeter. Subwavelength gratings are implemented as linear and circular polarization filters that are directly mounted onto the focal plane array of an infrared (IR) camera. Wire grid polarizers are used as linear polarization filters. The stacked structure, consisting of a wire grid polarizer and a form birefringent quarter-wave plate (QWP), implements the circular polarization filter and is the focus of this dissertation. Initial investigations of the development of the individual SWG components and their integration are presented. Rigorous Coupled Wave Analysis (RCWA) was used to design the SWG structures. A broadband form birefringent quarter-wave plate for the 3.5 to 5 μm wavelength range was designed as a grating structure patterned directly into the substrate. Two fabrication methods for the wire grid polarizer were investigated. A 0.5 μm period polarizer was patterned by interference lithography. A 1 μm period polarizer was patterned by contact printing. The stacking of the subwavelength grating structures was analyzed using the Jones Matrix calculus and a new RCWA method (developed by fellow graduate student Jianhua Jiang). Stacked SWG's were fabricated as large area (1.3 cm x 1.3 cm) filters and as a 256 x 256 array of small aperture (15 μm x 15 μm) pixels. Two stack designs were investigated, referred to as Stack I and Stack II. Stack I consisted of the 0.5 μm period polarizer and the form birefringent QWP. Stack II consisted of the I μm grid period polarizer and the form birefringent QWP. Simulation and measured results are presented to compare the cases of samples with and

  5. High-temperature steam electrolysis for hydrogen production: From material development to stack operation

    International Nuclear Information System (INIS)

    High-temperature steam electrolysis (HTSE) coupled with nuclear energy is one of the most promising options for hydrogen mass production. CEA (the French Atomic Energy Commission) is carrying out research in this field, from materials, cells and components developments to stack design including components and stack testing. One stack design among those developed at CEA will be addressed in this paper. This stack design is targeting high compactness, easy assembling and simple operation. The reliability of this design has been demonstrated through two tests of three cells short stacks, cells being commercial 225 cm2 electrolyte supported cells. Stacks have been operated in pure water vapour (no hydrogen introduced on the cathode side) at 820 deg. C. Hydrogen was produced at a flow rate of 7 mg/h/cm2 for the two stacks. The first stack was operated successfully for 170 hours. The test of the second one was extended up to 650 hours. Details about performance and durability of this second stack will be presented. Besides these activities on stack design, CEA is carrying out researches on new materials and cells in order to increase the cell and stack performances. For that purpose, alternative materials are studied, and among them layered perovskites used as oxygen electrode. This research, carried out jointly by ICMCB-CNRS and CEA highlighted the great potential of nickelates. It has been shown, on button cells at this stage, that the nickelate formulated Nd2NiO4+δ, represents a promising alternative to regular LSM anode (Patent CNRS-EDF (F) 'Procede et dispositif d'electrolyse de l'eau comprenant un materiau oxyde d'electrode particulier', P. Stevens, C. Lalanne, J.M. Bassat, F. Mauvy, J.C. Grenier. French patent: FR 2872174 2005-12-30). This material has been deposited on commercial half electrolyte supported cells, and three times higher performance has been obtained when operated in HTSE mode at 800 deg. C compared to an identical commercial cell containing the

  6. Bipolarly stacked electrolyser for energy and space efficient fabrication of supercapacitor electrodes

    Science.gov (United States)

    Liu, Xiaojuan; Wu, Tao; Dai, Zengxin; Tao, Keran; Shi, Yong; Peng, Chuang; Zhou, Xiaohang; Chen, George Z.

    2016-03-01

    Stacked electrolysers with titanium bipolar plates are constructed for electrodeposition of polypyrrole electrodes for supercapacitors. The cathode side of the bipolar Ti plates are pre-coated with activated carbon. In this new design, half electrolysis occurs which significantly lowers the deposition voltage. The deposited electrodes are tested in a symmetrical unit cell supercapacitor and an asymmetrical supercapacitor stack. Both devices show excellent energy storage performances and the capacitance values are very close to the design value, suggesting a very high current efficiency during the electrodeposition. The electrolyser stack offers multi-fold benefits for preparation of conducting polymer electrodes, i.e. low energy consumption, facile control of the electrode capacitance and simultaneous preparation of a number of identical electrodes. Therefore, the stacked bipolar electrolyser is a technology advance that offers an engineering solution for mass production of electrodeposited conducting polymer electrodes for supercapacitors.

  7. Stacks with TiN/titanium as the bipolar plate for PEMFCs

    International Nuclear Information System (INIS)

    Proton exchange membrane fuel cell (PEMFC) is a potential alternative for the internal combustion engine. But many problems, such as metallic bipolar plate instead of graphite bipolar plate to decrease the cost, should be solved before its application. Based on the previous results that single cell with TiN/Ti as bipolar plates shows high performance and enough long-time durability, the progress on the stacks with TiN/Ti as bipolar plates is reported in this manuscript. Till now seldom report is focused on stacks because of the complicated processing technique, especially for that with TiN/Ti as bipolar plate. The flow field in the plate is punched from titanium deformation, and two plates are welded by laser welding to form one piece of bipolar plate. The adopted processing techniques for stacks with TiN/Ti as bipolar plate exhibit advantage and feasibility in industry. The power density by weight for the stack is as high as 1353 W kg−1, although it still has space to be improved. Next work should be focused on the design of flow channel parameters and flow field type based on plastic deformation of metal materials. -- Highlights: ► The progress on the stacks with TiN/Ti as bipolar plates is reported. ► The adopted processing techniques exhibit feasibility in industry. ► The power density by weight for the stack is as high as 1353 W kg−1.

  8. Principles for Instructional Stack Development in HyperCard.

    Science.gov (United States)

    McEneaney, John E.

    The purpose of this paper is to provide information about obtaining and using HyperCard stacks that introduce users to principles of stack development. The HyperCard stacks described are available for downloading free of charge from a server at Indiana University South Bend. Specific directions are given for stack use, with advice for beginners. A…

  9. Development of cost innovative BPs for a PEMFC stack for a 1 kW-class residential power generator (RPG) system

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Gil-yong; Jung, Min-kyung; Ryoo, Sung-nam; Ha, Sam-chul [Digital Appliance R and D, LG Electronics, Seoul 153-801 (Korea, Republic of); Park, Myung-seok [LG Solar Energy, Seoul 150-721 (Korea, Republic of); Kim, Sunhoe [Department of New Energy and Resource Engineering, Sangji University, Wonju, Gangwon 220-702 (Korea, Republic of)

    2010-12-15

    In order to satisfy the demands of customers, cost innovation of fuel cell systems is required for the commercialization of the fuel cell. Since the stack is one of the most expensive parts in a fuel cell system, cost reduction of stack is required for fuel cell commercialization. For this effort stainless steel 304 sheets were etched for the flow field and then coated for corrosion resistance. This enables the development of highly cost-effective bipolar plates (BPs) for a Proton Exchange Membrane Fuel Cell (PEMFC) stack of a 1 kW-class for Residential Power Generator (RPG). LG Electronics (LGE) developed a metal stack of 64 cells with the developed BPs and achieved a performance rating of 0.75 V/cell at 200 mA/cm{sup 2}. LGE also achieved a stack volume reduction of 20% compared to a stack of the same specifications consisting of graphite material BPs. The volume decrease can be represented as a cost reduction. LGE achieved the very low cost innovation to 1 USD per cell with cells developed from etched metal BPs. LGE also achieved 500 h of operation with LGE's RPG system; this test is still ongoing. The degradation rate of the stack was 27 {mu}V/hr. The end of life of the stack was estimated at approximately 17,000 h. (author)

  10. Technical description of Stack 296-B-5

    International Nuclear Information System (INIS)

    Of particular concern to facilities on the Hanford site is Title 40, Code of Federal Regulations, Chapter 40, Part 61, Subpart H, ''National emission Standards for Emissions of Radionuclides Other Than Radon From Department of Energy Facilities.'' Assessments of facility stacks and potential radionuclide emissions determined whether these stacks would be subject to the sampling and monitoring requirements of 40 CFR 61, Subpart H. Stack 296-B-5 exhausts 221-BB building which houses tanks containing B Plant steam condensate and B Plant process condensate from the operation of the low-level waste concentrator. The assessment of potential radionuclide emissions from the 296-B-5 stack resulted in an effective dose equivalent to the maximally exposed individual of less than 0.1 millirem per year. Therefore, the stack is not subject to the sampling and monitoring requirements of 40 CFR 61, Subpart H. However, the sampling and monitoring system must be in compliance with the Environmental Compliance Manual, WHC-CM-7-5. Currently, 296-B-5 is sampled continuously with a record sampler and continuous air monitor (CAM)

  11. Levitation characteristics of HTS tape stacks

    Energy Technology Data Exchange (ETDEWEB)

    Pokrovskiy, S. V.; Ermolaev, Y. S.; Rudnev, I. A. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation)

    2015-03-15

    Due to the considerable development of the technology of second generation high-temperature superconductors and a significant improvement in their mechanical and transport properties in the last few years it is possible to use HTS tapes in the magnetic levitation systems. The advantages of tapes on a metal substrate as compared with bulk YBCO material primarily in the strength, and the possibility of optimizing the convenience of manufacturing elements of levitation systems. In the present report presents the results of the magnetic levitation force measurements between the stack of HTS tapes containing of tapes and NdFeB permanent magnet in the FC and ZFC regimes. It was found a non- linear dependence of the levitation force from the height of the array of stack in both modes: linear growth at small thickness gives way to flattening and constant at large number of tapes in the stack. Established that the levitation force of stacks comparable to that of bulk samples. The numerical calculations using finite element method showed that without the screening of the applied field the levitation force of the bulk superconductor and the layered superconductor stack with a critical current of tapes increased by the filling factor is exactly the same, and taking into account the screening force slightly different.

  12. Cathode degradation of the polymer electrolyte membrane fuel cell (PEMFC)

    International Nuclear Information System (INIS)

    Morphological changes occurring in membrane electrode assemblies (MEAs) of polymer electrolyte membrane fuel cells (PEMFC's) were monitored using scanning microscopy (SEM) during the course of 600 hours testing of hydrogen/air polymer electrolyte fuel cells (PEFCs). The microstructural study suggests a structural change caused by loss of the recast ionomer could result in deterioration of the integrity of the electrode, a drop in both ionic and electronic conductivities, loss of platinum particle clusters (for carbon support), and increased resistance within the interfacial zone of the membrane and catalyst layer.(author)

  13. Three wafer stacking for 3D integration.

    Energy Technology Data Exchange (ETDEWEB)

    Greth, K. Douglas; Ford, Christine L.; Lantz, Jeffrey W.; Shinde, Subhash L.; Timon, Robert P.; Bauer, Todd M.; Hetherington, Dale Laird; Sanchez, Carlos Anthony

    2011-11-01

    Vertical wafer stacking will enable a wide variety of new system architectures by enabling the integration of dissimilar technologies in one small form factor package. With this LDRD, we explored the combination of processes and integration techniques required to achieve stacking of three or more layers. The specific topics that we investigated include design and layout of a reticle set for use as a process development vehicle, through silicon via formation, bonding media, wafer thinning, dielectric deposition for via isolation on the wafer backside, and pad formation.

  14. Resolution of extensions of Picard 2-stacks

    OpenAIRE

    Bertolin, Cristiana; Tatar, Ahmet Emin

    2014-01-01

    Let S be a site. First we define the 3-category of torsors under a Picard S-2-stack and we furnish (1) a parametrization of the equivalence classes of objects, 1-arrows, 2-arrows and 3-arrows of the 3-category of torsors under a Picard S-2-stack by the cohomology groups of the derived functor of the functor of global sections, and (2) a geometrical description of the cohomology groups of the derived functor of the functor of global sections applied to length 3 complexes of abelian sheaves via...

  15. Seismic qualification of spent fuel storage stacks

    International Nuclear Information System (INIS)

    CANDU reactors designed in Canada are built and operated worldwide for producing electricity economically. The operation of CANDU reactors yields spent fuel bundles that are removed from the reactor core by means of remote mechanisms. The spent fuel bundles are transferred to a Spent Fuel Bay (SFB) for underwater cooling and long term storage. Spent fuel bundles are loaded onto stainless steel trays. A number of such trays are stacked vertically and stored on the floor of the SFB. It is necessary that the storage stacks maintain their structural integrity and stability under a severe design earthquake. This paper presents the methods and process used for seismic qualification of the storage stacks by analysis. The finite element models of the storage stack are developed to represent the behavior of the structure. The models are created for each individual tray and then restructured by using the sub-structuring technique. In this process, the stiffness matrix of a tray is condensed into a number of key points that include the points of contact between trays. In a storage stack the trays are pressed together by their own deadweight and by the weight of the fuel bundles and locked in place against each other at a number of contact points having no structural continuity. It can generally be assumed that the trays are in contact with each other. However the effectiveness of contact between the trays during seismic motion is uncertain due to erratic deflection, manufacturing irregularities and field conditions. Consequently a sensitivity study is carried out to assess the effect of lack of continuity at some of the contact points. The stack models are grouped into a number of multiple stack arrangements with the safeguard covers. They are grouped into different configurations and analyzed. Since the stacks are submerged in water, hydrodynamic effects are considered in the seismic model to more accurately predict the seismic behavior. A time-history analysis was then

  16. Stack Monitoring System At PUSPATI TRIGA Reactor

    International Nuclear Information System (INIS)

    This paper describes the current Stack Monitoring System at PUSPATI TRIGA Reactor (RTP) building. A stack monitoring system is a continuous air monitor placed at the reactor top for monitoring the presence of radioactive gaseous in the effluent air from the RTP building. The system consists of four detectors that provide the reading for background, particulate, Iodine and Noble gas. There is a plan to replace the current system due to frequent fault of the system, thus thorough understanding of the current system is required. Overview of the whole system will be explained in this paper. Some current results would be displayed and moving forward brief plan would be mentioned. (author)

  17. When is Stacking Confusing?: The Impact of Confusion on Stacking in Deep HI Galaxy Surveys

    CERN Document Server

    Jones, Michael G; Giovanelli, Riccardo; Papastergis, Emmanouil

    2015-01-01

    We present an analytic model to predict the HI mass contributed by confused sources to a stacked spectrum in a generic HI survey. Based on the ALFALFA correlation function, this model is in agreement with the estimates of confusion present in stacked Parkes telescope data, and was used to predict how confusion will limit stacking in the deepest SKA-precursor HI surveys. Stacking with LADUMA and DINGO UDEEP data will only be mildly impacted by confusion if their target synthesised beam size of 10 arcsec can be achieved. Any beam size significantly above this will result in stacks that contain a mass in confused sources that is comparable to (or greater than) that which is detectable via stacking, at all redshifts. CHILES' 5 arcsec resolution is more than adequate to prevent confusion influencing stacking of its data, throughout its bandpass range. FAST will be the most impeded by confusion, with HI surveys likely becoming heavily confused much beyond z = 0.1. The largest uncertainties in our model are the reds...

  18. Stacking of SKA data: comparing uv-plane and image-plane stacking

    CERN Document Server

    Knudsen, K K; Vlemmings, W; Conway, J; Marti-Vidal, I

    2015-01-01

    Stacking as a tool for studying objects that are not individually detected is becoming popular even for radio interferometric data, and will be widely used in the SKA era. Stacking is typically done using imaged data rather than directly using the visibilities (the uv-data). We have investigated and developed a novel algorithm to do stacking using the uv-data. We have performed exten- sive simulations comparing to image-stacking, and summarize the results of these simulations. Furthermore, we disuss the implications in light of the vast data volume produced by the SKA. Having access to the uv-stacked data provides a great advantage, as it allows the possibility to properly analyse the result with respect to calibration artifacts as well as source properties such as size. For SKA the main challenge lies in archiving the uv-data. For purposes of robust stacking analysis, it would be strongly desirable to either keep the calibrated uv-data at least in an aver- age form, or implement a stacking queue where stacki...

  19. Technology leadership: a road map to commercially viable PEMFC stack technology. Paper no. IGEC-1-008

    International Nuclear Information System (INIS)

    'Full text:' In February 2005, Ballard announced its most recent advances in PEMFC stack technology. This technology development exhibited, we believe, for the first time the capability of a single PEMFC stack design to demonstrate combined excellence in cost reduction, freeze start capability from -20 C and durability under an automotive OEM defined dynamic operating cycle, comparable to that experienced by a fuel cell stack in an actual vehicle. One month later, building on the above technology leadership demonstration, Ballard announced a technology 'oad map' that defined a path to commercially viability for a PEMFC stack by 2010. The key target parameters for cost reduction, durability, freeze start and stack power density are described in detail along with demonstrated historical capability and a clear path as to how Ballard will achieve the required targets. (author)

  20. Critical assessment of power trains with fuel-cell systems and different fuels

    Science.gov (United States)

    Höhlein, B.; von Andrian, S.; Grube, Th; Menzer, R.

    Legal regulations (USA, EU) are a major driving force for intensifying technological developments with respect to the global automobile market. In the future, highly efficient vehicles with very low emission levels will include low-temperature fuel-cell systems (PEFC) as units of electric power trains. With alcohols, ether or hydrocarbons used as fuels for these new electric power trains, hydrogen as PEFC fuel has to be produced on board. These concepts including the direct use of methanol in fuel-cell systems, differ considerably in terms of both their development prospects and the results achieved so far. Based on process engineering analyses for net electricity generation in PEFC-powered power trains, as well as on assumptions for electric power trains and vehicle configurations, different fuel-cell performances and fuel processing units for octane, diesel, methanol, ethanol, propane and dimethylether have been evaluated as fuels. The possible benefits and key challenges for different solutions of power trains with fuel-cell systems/on-board hydrogen production and with direct methanol fuel-cell (DMFC) systems have been assessed. Locally, fuel-cell power trains are almost emission-free and, unlike battery-powered vehicles, their range is comparable to conventional vehicles. Therefore, they have application advantages cases of particularly stringent emission standards requiring zero emission. In comparison to internal combustion engines, using fuel-cell power trains can lead to clear reductions in primary energy demand and global, climate-relevant emissions providing the advantage of the efficiency of the hydrogen/air reaction in the fuel cell is not too drastically reduced by additional conversion steps of on-board hydrogen production, or by losses due to fuel supply provision.

  1. Stacking non-BPS D-branes

    International Nuclear Information System (INIS)

    We present a candidate supergravity solution for a stacked configuration of stable non-BPS D-branes in Type II string theory compactified on T4/Z2. This gives a supergravity description of nonabelian tachyon condensation on the brane woldvolume. (author)

  2. OpenStack cloud computing cookbook

    CERN Document Server

    Jackson, Kevin

    2013-01-01

    A Cookbook full of practical and applicable recipes that will enable you to use the full capabilities of OpenStack like never before.This book is aimed at system administrators and technical architects moving from a virtualized environment to cloud environments with familiarity of cloud computing platforms. Knowledge of virtualization and managing linux environments is expected.

  3. Average Transmission Probability of a Random Stack

    Science.gov (United States)

    Lu, Yin; Miniatura, Christian; Englert, Berthold-Georg

    2010-01-01

    The transmission through a stack of identical slabs that are separated by gaps with random widths is usually treated by calculating the average of the logarithm of the transmission probability. We show how to calculate the average of the transmission probability itself with the aid of a recurrence relation and derive analytical upper and lower…

  4. Revisiting Stacking Fault Energy of Steels

    Science.gov (United States)

    Das, Arpan

    2016-02-01

    The stacking fault energy plays an important role in the transition of deformation microstructure. This energy is strongly dependent on the concentration of alloying elements and the temperature under which the alloy is exposed. Extensive literature review has been carried out and investigated that there are inconsistencies in findings on the influence of alloying elements on stacking fault energy. This may be attributed to the differences in chemical compositions, inaccuracy in measurements, and the methodology applied for evaluating the stacking fault energy. In the present research, a Bayesian neural network model is created to correlate the complex relationship between the extent of stacking fault energy with its influencing parameters in different austenitic grade steels. The model has been applied to confirm that the predictions are reasonable in the context of metallurgical principles and other data published in the open literature. In addition, it has been possible to estimate the isolated influence of particular variables such as nickel concentration, which exactly cannot in practice be varied independently. This demonstrates the ability of the method to investigate a new phenomenon in cases where the information cannot be accessed experimentally.

  5. OpenStack Object Storage (Swift) essentials

    CERN Document Server

    Kapadia, Amar; Varma, Sreedhar

    2015-01-01

    If you are an IT administrator and you want to enter the world of cloud storage using OpenStack Swift, then this book is ideal for you. Basic knowledge of Linux and server technology is beneficial to get the most out of the book.

  6. SRS reactor stack plume marking tests

    International Nuclear Information System (INIS)

    Tests performed in 105-K in 1987 and 1988 demonstrated that the stack plume can successfully be made visible (i.e., marked) by introducing smoke into the stack breech. The ultimate objective of these tests is to provide a means during an emergency evacuation so that an evacuee can readily identify the stack plume and evacuate in the opposite direction, thus minimizing the potential of severe radiation exposure. The EPA has also requested DOE to arrange for more tests to settle a technical question involving the correct calculation of stack downwash. New test canisters were received in 1988 designed to produce more smoke per unit time; however, these canisters have not been evaluated, because normal ventilation conditions have not been reestablished in K Area. Meanwhile, both the authorization and procedure to conduct the tests have expired. The tests can be performed during normal reactor operation. It is recommended that appropriate authorization and procedure approval be obtained to resume testing after K Area restart

  7. Contemporary sample stacking in analytical electrophoresis

    Czech Academy of Sciences Publication Activity Database

    Malá, Zdeňka; Šlampová, Andrea; Křivánková, Ludmila; Gebauer, Petr; Boček, Petr

    2015-01-01

    Roč. 36, č. 1 (2015), s. 15-35. ISSN 0173-0835 R&D Projects: GA ČR(CZ) GA13-05762S Institutional support: RVO:68081715 Keywords : biological samples * stacking * trace analysis * zone electrophoresis Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 3.028, year: 2014

  8. Experimental and numerical investigations of oscillations in extracted material parameters for finite Bragg stacks using the NRW method

    DEFF Research Database (Denmark)

    Clausen, Niels Christian Jerichau; Arslanagic, Samel; Breinbjerg, Olav

    A 1D dielectric finite Bragg stack situated in a rectangular waveguide and illuminated by the fundamental TE10 mode is examined analytically, numerically, and experimentally. Calculated as well as measured scattering parameters are used to extract the effective/equivalent material parameters for...... three specific configurations of its constituent unit cell. Particular attention is devoted to the absence/presence of certain oscillations in the extracted material parameters, depending on the unit cell configuration. The results for the finite Bragg stack are further verified to agree with those of...... an infinite Bragg stack, for which the dispersion equation is used in conjunction with the Floquet-Bloch harmonics expansion to extract the material parameters. It is shown that the extracted material parameters for the finite and infinite Bragg stacks agree for the symmetric unit cell configuration....

  9. Air plasma treated chitosan fibers-stacked scaffolds

    International Nuclear Information System (INIS)

    Chitosan is a nontoxic, biodegradable and biocompatible polymer. Rapid prototyped chitosan scaffolds were manufactured by liquid-frozen deposition of chitosan fibers in this study. To investigate if the air plasma (AP) treatment could be used to improve the surface properties of these scaffolds for cell attachment, chitosan films were first prepared and treated with AP under different conditions. Under the optimized condition, the water contact angle of chitosan films was significantly reduced from 90 ± 1° to 19 ± 1° after AP treatment. On the other hand, the surface charge and nanometric roughness of chitosan films increased after AP treatment. X-ray photoelectron spectroscopy measurement on AP-treated three-dimensional chitosan scaffolds showed that nitrogen and oxygen increased at each location inside the scaffolds as compared to the untreated ones, which indicated that AP could permeate through the fibrous stacks of the scaffolds and effectively modify the interior (visible) surface of the scaffolds. Moreover, AP treatment enabled the migration of MC3T3-E1 cells into the scaffolds, facilitated their proliferation and promoted the bone mineral deposition. These results suggested that fibers-stacked chitosan scaffolds may be produced by liquid-frozen deposition and treated with AP for bone tissue engineering applications. (paper)

  10. X-ray evaluation of the boundary between polymer electrolyte and platinum and carbon functionalization to conduct protons in polymer electrolyte fuel cells

    Science.gov (United States)

    Oka, Kazuki; Ogura, Yuta; Izumi, Yasuo

    2014-07-01

    In polymer electrolyte fuel cells (PEFCs), it is important to secure proximate diffusion paths of reactants and electrons. One approach is to optimize the boundary between polymer electrolyte and Pt nanoparticle surface. Based on synchrotron X-ray absorption fine structure to monitor directly the status of catalysts in PEFCs, it was found that Pt sites were reduced to Pt0 by alcohols contained in polymer electrolyte dispersion solution during the preparation of cathode of PEFC. As in membrane electrolyte assembly, only the Pt sites not covered by polymer electrolyte re-oxidized to Pt2+/4+. Thus, the interface between Pt and polymer electrolyte was evaluated. The other approach is to functionalize carbon surface with sulfonate/sulfate group to conduct protons. Similar level of proton conductivity was observed in current-voltage dependence compared to using polymer electrolyte, but polymer electrolyte was advantageous to lose less voltage for activation. Based on this comparison, optimum catalyst on cathode is proposed comprising surface sulfonate/sulfate group on carbon mixed with polymer electrolyte. Further optimization of cathode catalyst is proposed to functionalize carbon with sulfonate group linked to fluorocarbon branch.

  11. Micro-electroforming metallic bipolar electrodes for mini-DMFC stacks

    CERN Document Server

    Shyu, R F; Lee, J -H

    2008-01-01

    This paper describes the development of metallic bipolar plate fabrication using micro-electroforming process for mini-DMFC (direct methanol fuel cell) stacks. Ultraviolet (UV) lithography was used to define micro-fluidic channels using a photomask and exposure process. Micro-fluidic channels mold with 300 micrometers thick and 500 micrometers wide were firstly fabricated in a negative photoresist onto a stainless steel plate. Copper micro-electroforming was used to replicate the micro-fluidic channels mold. Following by sputtering silver (Ag) with 1.2 micrometers thick, the metallic bipolar plates were completed. The silver layer is used for corrosive resistance. The completed mini-DMFC stack is a 2x2 cm2 fuel cell stack including a 1.5x1.5 cm2 MEA (membrane electrode assembly). Several MEAs were assembly into mini-DMFC stacks using the completed metallic bipolar plates. All test results showed the metallic bipolar plates suitable for mini-DMFC stacks. The maximum output power density is 9.3mW/cm2 and curren...

  12. Graphite-based photovoltaic cells

    Science.gov (United States)

    Lagally, Max; Liu, Feng

    2010-12-28

    The present invention uses lithographically patterned graphite stacks as the basic building elements of an efficient and economical photovoltaic cell. The basic design of the graphite-based photovoltaic cells includes a plurality of spatially separated graphite stacks, each comprising a plurality of vertically stacked, semiconducting graphene sheets (carbon nanoribbons) bridging electrically conductive contacts.

  13. Nuclearite Search with the TL Stack Detector at Ground Level

    Science.gov (United States)

    Akitsu, Y.; Iwata, K.; Kirihara, Y.; Kuga, K.; Lan, S.; Nakagawa, M.; Okei, K.; Saavedra, O.; Tada, J.; Takahashi, N.; Tsuji, S.; Yamashita, Y.; Yamamoto, I.; Wada, T.

    2003-07-01

    The TL stack has been develoved as a nuclearite detector. We are planning a nuclearite search experiment at ground level with the TL stacks. Results from a test experiment at Okayama University is reported.

  14. Project W-420 Stack Monitoring system upgrades conceptual design report

    International Nuclear Information System (INIS)

    This document describes the scope, justification, conceptual design, and performance of Project W-420 stack monitoring system upgrades on six NESHAP-designated, Hanford Tank Farms ventilation exhaust stacks

  15. Stacking from Tags: Clustering Bookmarks around a Theme

    OpenAIRE

    Zubiaga, Arkaitz; García-Plaza, Alberto Pérez; Fresno, Víctor; Martínez, Raquel

    2013-01-01

    Since very recently, users on the social bookmarking service Delicious can stack web pages in addition to tagging them. Stacking enables users to group web pages around specific themes with the aim of recommending to others. However, users still stack a small subset of what they tag, and thus many web pages remain unstacked. This paper presents early research towards automatically clustering web pages from tags to find stacks and extend recommendations.

  16. Anisotropic electronic conduction in stacked two-dimensional titanium carbide

    OpenAIRE

    Tao Hu; Hui Zhang; Jiemin Wang; Zhaojin Li; Minmin Hu; Jun Tan; Pengxiang Hou; Feng Li; Xiaohui Wang

    2015-01-01

    Stacked two-dimensional titanium carbide is an emerging conductive material for electrochemical energy storage which requires an understanding of the intrinsic electronic conduction. Here we report the electronic conduction properties of stacked Ti3C2 T 2 (T = OH, O, F) with two distinct stacking sequences (Bernal and simple hexagonal). On the basis of first-principles calculations and energy band theory analysis, both stacking sequences give rise to metallic conduction with Ti 3d electrons c...

  17. Space plasma physics: isotopic stack: measurement of heavy cosmic rays.

    Science.gov (United States)

    Beaujean, R; Schmidt, M; Enge, W; Siegmon, G; Krause, J; Fischer, E

    1984-07-13

    A stack of plastic nuclear track detectors was exposed to heavy cosmic rays on the pallet of Spacelab 1. Some layers of the stack were rotated with respect to the main stack to determine the arrival time of the particles. After return of the stack the latent particle tracks are revealed by chemical etching. Under the optical microscope the charge, mass, energy, and impact direction of the particles can be deduced from the track geometry. PMID:17837938

  18. Funcionamiento y Estabilidad en el Tiempo de un Sistema Energético con Batería PEM a Combustible y sus Componentes Periféricos Work Conditions and Time Stability Study on a Fuel Cell Stack and its Peripheral Components

    Directory of Open Access Journals (Sweden)

    Juan I Franco

    2010-01-01

    Full Text Available En este trabajo se presenta el desarrollo completo de una batería de tipo membrana de electrolito polimérico (protón exchange membrane fuel cell stack, PEMFCS, y se muestra el funcionamiento de un sistema experimental completo que está siendo probado en la Base Esperanza que el Ejército Argentino posee en la Antártida. El conjunto desarrollado permite trabajar con un mínimo de componentes periféricos y ser manejado por personal entrenado con capacitación básica para su operación y mantenimiento. La resistencia óhmica de la batería no difiere de la que se obtendría con seis elementos en serie; su pendiente de Tafel es de 80 mV/déc. Las pruebas de estabilidad en el tiempo alcanzaron 2278 horas y la energía entregada en ese tiempo fue de 4.2 kWh.The development and working performance of a protón exchange membrane fuel cell stack (PEMFCS which was installed at Base Esperanza belonging to the Argentinean Army in the Antarctic territory is presented. The set designed and installed allows working with mínimum peripherical devices and can be operated and maintained by personnel with basic training. The ohmic resistance of the battery is the same that could be obtained from six elements in series; the Tafel slope is 80 mV/dec. Stability experiments were performed during 2278 hours, and the energy generated was 4.2 kWh.

  19. Text-Filled Stacked Area Graphs

    DEFF Research Database (Denmark)

    Kraus, Martin

    2011-01-01

    Text can add a significant amount of detail and value to an information visualization. In particular, it can integrate more of the data that a visualization is based on, and it can also integrate information that is personally relevant to readers of a visualization. This may influence readers...... to consider a visualization a detailed enrichment of their personal experience instead of an abstract representation of anonymous numbers. However, the integration of textual detail into a visualization is often very challenging. This work discusses one particular approach to this problem, namely text......-filled stacked area graphs; i.e., graphs that feature stacked areas that are filled with small-typed text. Since these graphs allow for computing the text layout automatically, it is possible to include large amounts of textual detail with very little effort. We discuss the most important challenges and some...

  20. Industrial stacks design; Diseno de chimeneas industriales

    Energy Technology Data Exchange (ETDEWEB)

    Cacheux, Luis [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

    1986-12-31

    The Instituto de Investigaciones Electricas (IIE) though its Civil Works Department, develops, under contract with CFE`s Gerencia de Proyectos Termoelectricos (Management of Fossil Power Plant Projects), a series of methods for the design of stacks, which pretends to solve the a present day problem: the stack design of the fossil power plants that will go into operation during the next coming years in the country. [Espanol] El Instituto de Investigaciones Electricas (IIE), a traves del Departamento de Ingenieria Civil, desarrolla, bajo contrato con la Gerencia de Proyectos Termoelectricos, de la Comision Federal de Electricidad (CFE), un conjunto de metodos para el diseno de chimeneas, con el que se pretende resolver un problema inmediato: el diseno de las chimeneas de las centrales termoelectricas que entraran en operacion durante los proximos anos, en el pais.

  1. High power collimated diode laser stack

    Institute of Scientific and Technical Information of China (English)

    LIU Yuan-yuan; FANG Gao-zhan; MA Xiao-yu; LIU Su-ping; FENG Xiao-ming

    2006-01-01

    A high power collimated diode laser stack is carried out based on fast-axis collimation and stack packaging techniques.The module includes ten typical continuous wave (cw) bars and the total output power can be up to 368W at 48.6A.Using a cylindrical lens as the collimation elements,we can make the fast-axis divergence and the slow-axis divergence are 0.926 40 and 8.2060 respectively.The light emitting area is limited in a square area of 18.3 mm×11 mm.The module has the advantage of high power density and offers a wide potential applications in pumping and material processing.

  2. System for inspection of stacked cargo containers

    Science.gov (United States)

    Derenzo, Stephen

    2011-08-16

    The present invention relates to a system for inspection of stacked cargo containers. One embodiment of the invention generally comprises a plurality of stacked cargo containers arranged in rows or tiers, each container having a top, a bottom a first side, a second side, a front end, and a back end; a plurality of spacers arranged in rows or tiers; one or more mobile inspection devices for inspecting the cargo containers, wherein the one or more inspection devices are removeably disposed within the spacers, the inspection means configured to move through the spacers to detect radiation within the containers. The invented system can also be configured to inspect the cargo containers for a variety of other potentially hazardous materials including but not limited to explosive and chemical threats.

  3. Radiation-Tolerant Intelligent Memory Stack - RTIMS

    Science.gov (United States)

    Ng, Tak-kwong; Herath, Jeffrey A.

    2011-01-01

    This innovation provides reconfigurable circuitry and 2-Gb of error-corrected or 1-Gb of triple-redundant digital memory in a small package. RTIMS uses circuit stacking of heterogeneous components and radiation shielding technologies. A reprogrammable field-programmable gate array (FPGA), six synchronous dynamic random access memories, linear regulator, and the radiation mitigation circuits are stacked into a module of 42.7 42.7 13 mm. Triple module redundancy, current limiting, configuration scrubbing, and single- event function interrupt detection are employed to mitigate radiation effects. The novel self-scrubbing and single event functional interrupt (SEFI) detection allows a relatively soft FPGA to become radiation tolerant without external scrubbing and monitoring hardware

  4. Spectral analysis using linearly chirped Gaussian pulse stacking

    International Nuclear Information System (INIS)

    We analyze the spectrum of a stacked pulse with the technique of linearly chirped Gaussian pulse stacking. Our results show that there are modulation structures in the spectrum of the stacked pulse. The modulation frequencies are discussed in detail. By applying spectral analysis, we find that the intensity fluctuation cannot be smoothed by introducing an optical amplitude filter. (authors)

  5. A Late Pleistocene sea level stack

    OpenAIRE

    Spratt, R. M.; L. E. Lisiecki

    2015-01-01

    Late Pleistocene sea level has been reconstructed from ocean sediment core data using a wide variety of proxies and models. However, the accuracy of individual reconstructions is limited by measurement error, local variations in salinity and temperature, and assumptions particular to each technique. Here we present a sea level stack (average) which increases the signal-to-noise ratio of individual reconstructions. Specifically, we perform principal componen...

  6. Angular resolution of stacked resistive plate chambers

    CERN Document Server

    Samuel, Deepak; Murgod, Lakshmi P

    2016-01-01

    We present here detailed derivations of mathematical expressions for the angular resolution of a set of stacked resistive plate chambers (RPCs). The expressions are validated against experimental results using data collected from the prototype detectors (without magnet) of the upcoming India-based Neutrino Observatory (INO). In principle, these expressions can be used for any other detector with an architecture similar to that of RPCs.

  7. Fresnel aperture pre-stack depth migration

    OpenAIRE

    2005-01-01

    In this thesis, I present the results of a new approach to pre-stack Kirchoff depth migration using the Kirchoff algorithm and the Fresnel aperture features in order to improve the signal-to-noise ratio of the seismic data in depth imaging. Another advantage of this method is that it requires no additionnal measurments compared to the traditionnal PSDM. Indeed, the Fresnel apertures are picked interactively, in a way that is similar to velocity picking, and thereafter used during the migratio...

  8. CAM and stack air sampler design guide

    International Nuclear Information System (INIS)

    About 128 air samplers and CAMs presently in service to detect and document potential radioactive release from 'H' and 'F' area tank farm ventilation stacks are scheduled for replacement and/or upgrade by Projects S-5764, S-2081, S-3603, and S-4516. The seven CAMs scheduled to be upgraded by Project S-4516 during 1995 are expected to provide valuable experience for the three remaining projects. The attached document provides design guidance for the standardized High Level Waste air sampling system

  9. Development and Characterization of an Electrically Rechargeable Zinc-Air Battery Stack

    Directory of Open Access Journals (Sweden)

    Hongyun Ma

    2014-10-01

    Full Text Available An electrically rechargeable zinc-air battery stack consisting of three single cells in series was designed using a novel structured bipolar plate with air-breathing holes. Alpha-MnO2 and LaNiO3 severed as the catalysts for the oxygen reduction reaction (ORR and oxygen evolution reaction (OER. The anodic and cathodic polarization and individual cell voltages were measured at constant charge-discharge (C-D current densities indicating a uniform voltage profile for each single cell. One hundred C-D cycles were carried out for the stack. The results showed that, over the initial 10 cycles, the average C-D voltage gap was about 0.94 V and the average energy efficiency reached 89.28% with current density charging at 15 mA·cm−2 and discharging at 25 mA·cm−2. The total increase in charging voltage over the 100 C-D cycles was ~1.56% demonstrating excellent stability performance. The stack performance degradation was analyzed by galvanostatic electrochemical impedance spectroscopy. The charge transfer resistance of ORR increased from 1.57 to 2.21 Ω and that of Zn/Zn2+ reaction increased from 0.21 to 0.34 Ω after 100 C-D cycles. The quantitative analysis guided the potential for the optimization of both positive and negative electrodes to improve the cycle life of the cell stack.

  10. Initiation and Performance of a Coating for Countering Chromium Poisoning in a SOFC-stack

    DEFF Research Database (Denmark)

    Nielsen, Karsten Agersted; Persson, Åsa Helen; Beeaff, Dustin;

    2007-01-01

    Minimising transport of chromium from the metallic interconnect (e.g. of Crofer 22APU) to the cathode in a planar solid oxide fuel cell is done by application of a coating between the two parts. The coating is applied by slurry coating, and taken through stack initialisation it transforms...

  11. HTS twisted stacked-tape cable conductor

    International Nuclear Information System (INIS)

    The feasibility of high field magnet applications of the twisted stacked-tape cabling method with 2G YBCO tapes has been investigated. An analysis of torsional twist strains of a thin HTS tape has been carried out taking into account the internal shortening compressive strains accompanied with the lengthening tensile strains due to the torsional twist. The model is benchmarked against experimental tests using YBCO tapes. The critical current degradation and current distribution of a four-tape conductor was evaluated by taking account of the twist strain, the self-field and the termination resistances. The critical current degradation for the tested YBCO cables can be explained by the perpendicular self-field effect. It is shown that the critical current of a twisted stacked-tape conductor with a four-tape cable does not degrade with a twist pitch length as short as 120 mm. Current distribution among tapes and hysteresis losses are also investigated. A compact joint termination method for a 2G YBCO tape cable has been developed. The twisted stacked-tape conductor method may be an attractive means for the fabrication of highly compact, high current cables from multiple flat HTS tapes.

  12. Range Extender Vehicle Concept Based on High Temperature Polymer Electrolyte Membrane Fuel Cell

    OpenAIRE

    Dickinson, Dave; Nasri, Mounir

    2014-01-01

    Battery electric vehicles that would be suitable for urban traffic as well as for longer distances will be equipped with a range extender (REX). In this range extender vehicle concept, the powertrain is driven mainly by the high performance li-ion battery added by a HT-PEFC (Polymer Electrolyte Membrane Fuel Cell). The on-board fuel cell range extender serves as an additional energy source, which charges the high performance battery during the trip especially in a long distance trip. O...

  13. Mathematical Modeling of Transport Phenomena in Polymer Electrolyte and Direct Methanol Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Birgersson, Erik

    2004-02-01

    This thesis deals with modeling of two types of fuel cells: the polymer electrolyte fuel cell (PEFC) and the direct methanol fuel cell (DMFC), for which we address four major issues: a) mass transport limitations; b) water management (PEFC); c) gas management (DMFC); d) thermal management. Four models have been derived and studied for the PEFC, focusing on the cathode. The first exploits the slenderness of the cathode for a two-dimensional geometry, leading to a reduced model, where several non dimensional parameters capture the behavior of the cathode. The model was extended to three dimensions, where four different flow distributors were studied for the cathode. A quantitative comparison shows that the interdigitated channels can sustain the highest current densities. These two models, comprising isothermal gas phase flow, limit the studies to (a). Returning to a two-dimensional geometry of the PEFC, the liquid phase was introduced via a separate flow model approach for the cathode. In addition to conservation of mass, momentum and species, the model was extended to consider simultaneous charge and heat transfer for the whole cell. Different thermal, flow fields, and hydrodynamic conditions were studied, addressing (a), (b) and (d). A scale analysis allowed for predictions of the cell performance prior to any computations. Good agreement between experiments with a segmented cell and the model was obtained. A liquid-phase model, comprising conservation of mass, momentum and species, was derived and analyzed for the anode of the DMFC. The impact of hydrodynamic, electrochemical and geometrical features on the fuel cell performance were studied, mainly focusing on (a). The slenderness of the anode allows the use of a narrow-gap approximation, leading to a reduced model, with benefits such as reduced computational cost and understanding of the physical trends prior to any numerical computations. Adding the gas-phase via a multiphase mixture approach, the gas

  14. Transport studies in polymer electrolyte fuel cell with porous metallic flow field at ultra high current density

    Science.gov (United States)

    Srouji, Abdul-Kader

    Achieving cost reduction for polymer electrolyte fuel cells (PEFC) requires a simultaneous effort in increasing power density while reducing precious metal loading. In PEFCs, the cathode performance is often limiting due to both the slow oxygen reduction reaction (ORR), and mass transport limitation caused by limited oxygen diffusion and liquid water flooding at high current density. This study is motivated by the achievement of ultra-high current density through the elimination of the channel/land (C/L) paradigm in PEFC flow field design. An open metallic element (OME) flow field capable of operating at unprecedented ultra-high current density (3 A/cm2) introduces new advantages and limitations for PEFC operation. The first part of this study compares the OME with a conventional C/L flow field, through performance and electrochemical diagnostic tools such as electrochemical impedance spectroscopy (EIS). The results indicate the uniqueness of the OME's mass transport improvement. No sign of operation limitation due to flooding is noted. The second part specifically examines water management at high current density using the OME flow field. A unique experimental setup is developed to measure steady-state and transient net water drag across the membrane, in order to characterize the fundamental aspects of water transport at high current density with the OME. Instead of flooding, the new limitation is identified to be anode side dry-out of the membrane, caused by electroosmotic drag. The OME improves water removal from the cathode, which immediately improves oxygen transport and performance. However, the low water content in the cathode reduces back diffusion of water to the membrane, and electroosmotic drag dominates at high current density, leading to dry-out. The third part employs the OME flow field as a tool that avoids C/L effects endemic to a typical flow field, in order to study oxygen transport resistance at the catalyst layer of a PEFC. In open literature, a

  15. Spectral shifts in the properties of a periodic multilayered stack due to isotropic chiral layers

    CERN Document Server

    Ramakrishna, S Anantha

    2009-01-01

    Investigating the canonical problem of a periodic multilayered stack containing isotropic chiral layers, we homogenized it as a uniaxial bianisotropic medium and derived its effective constitutive parameters. The stack shows a resonant behavior, when its unit cell consists of a metallic layer and an isotropic chiral layer. The presence of isotropic chirality can result in small shifts of the resonance frequency for reasonably large values of the chirality parameter, implying that the sign of an effective permittivity can be switched. Such spectral shifts in the dielectric properties can be potentially useful for spectroscopic purposes.

  16. Manila – OpenStack File Sharing Service

    OpenAIRE

    Patrascoiu, Mihai; Leon, Jose Castro

    2015-01-01

    Abstract  The report presents a short overview on what OpenStack is, how and why is it used at CERN and also goes into detail about the OpenStack Manila component, a service that enables file based storage and file sharing within OpenStack virtual machines.  OpenStack Manila is a relatively new OpenStack component, having started in 2012 and in 2014 it has reached the latest cycle of development, where it could still be found at the time of the report. The fundamental object...

  17. Swiss fuel cell passenger and pleasure boats

    Energy Technology Data Exchange (ETDEWEB)

    Affolter, J.-F.

    2000-07-01

    This paper published by the University of Applied Science in Yverdon-les-Bains, Switzerland, looks at the development of electrically driven small boats that are powered by fuel cells. The various implementations of the test boats are described. Starting with a 100-watt PEM fuel cell built by the Paul Scherrer Institute (PSI) and the University of Applied Science in Solothurn, Switzerland, for educational purposes, a small pedal-boat was electrified. The paper describes the development of four further prototypes and introduces a new project for a 6-passenger leisure boat powered by a 2 kW PEFC fuel cell. Apart from the fuel cells, various other components such as propellers and control electronics are discussed as are the remaining problems still to be solved before the cells and boats can be marketed. Since they were carried out at a technical university, these projects are said to have provided an excellent way of teaching new technologies to students.

  18. Ab initio engineering of materials with stacked hexagonal tin frameworks

    Science.gov (United States)

    Shao, Junping; Beaufils, Clément; Kolmogorov, Aleksey N.

    2016-01-01

    The group-IV tin has been hypothesized to possess intriguing electronic properties in an atom-thick hexagonal form. An attractive pathway of producing sizable 2D crystallites of tin is based on deintercalation of bulk compounds with suitable tin frameworks. Here, we have identified a new synthesizable metal distannide, NaSn2, with a 3D stacking of flat hexagonal layers and examined a known compound, BaSn2, with buckled hexagonal layers. Our ab initio results illustrate that despite being an exception to the 8-electron rule, NaSn2 should form under pressures easily achievable in multi-anvil cells and remain (meta)stable under ambient conditions. Based on calculated Z2 invariants, the predicted NaSn2 may display topologically non-trivial behavior and the known BaSn2 could be a strong topological insulator. PMID:27387140

  19. Compliant Glass Seals for SOFC Stacks

    Energy Technology Data Exchange (ETDEWEB)

    Chou, Y. S.; Choi, Jung-Pyung; Xu, Wei; Stephens, Elizabeth V.; Koeppel, Brian J.; Stevenson, Jeffry W.; Lara-Curzio, Edgar

    2014-04-01

    This report summarizes results from experimental and modeling studies performed by participants in the Solid-State Energy Conversion Alliance (SECA) Core Technology Program, which indicate that compliant glass-based seals offer a number of potential advantages over conventional seals based on de-vitrifying glasses, including reduced stresses during stack operation and thermal cycling, and the ability to heal micro-damage induced during thermal cycling. The properties and composition of glasses developed and/or investigated in these studies are reported, along with results from long-term (up to 5,800h) evaluations of seals based on a compliant glass containing ceramic particles or ceramic fibers.

  20. Simple model of stacking-fault energies

    DEFF Research Database (Denmark)

    Stokbro, Kurt; Jacobsen, Lærke Wedel

    1993-01-01

    metals, and thereby explain the pronounced differences in energetics in these two classes of metals. The model is discussed in the framework of the effective-medium theory where it is possible to find a functional form for the pair potential and relate the contribution associated with the fourth moment......A simple model for the energetics of stacking faults in fcc metals is constructed. The model contains third-nearest-neighbor pairwise interactions and a term involving the fourth moment of the electronic density of states. The model is in excellent agreement with recently published local...

  1. Stacking faults in SiC nanowires.

    Science.gov (United States)

    Wallis, K L; Wieligor, M; Zerda, T W; Stelmakh, S; Gierlotka, S; Palosz, B

    2008-07-01

    SiC nanowires were obtained by a reaction between vapor silicon and multiwall carbon nanotubes, CNT, in vacuum at 1200 degrees C. Raman and IR spectrometry, X-ray diffraction and high resolution transmission electron microscopy, HRTEM, were used to characterize properties of SiC nanowires. Morphology and chemical composition of the nanowires was similar for all samples, but concentration of structural defects varied and depended on the origin of CNT. Stacking faults were characterized by HRTEM and Raman spectroscopy, and both techniques provided complementary results. Raman microscopy allowed studying structural defects inside individual nanowires. A thin layer of amorphous silicon carbide was detected on the surface of nanowires. PMID:19051903

  2. A metallic seal for high-temperature electrolysis stacks

    International Nuclear Information System (INIS)

    Gas tightness over a long period of time is a real challenge in high-temperature electrolysis. The seals must indeed be able to run at high temperature between metals and brittle ceramic materials, which is a major issue to be solved. The common sealing solution relies on glass-made seals, despite their low mechanical strength at high temperature. Metallic seals have seldom been used in this field, because their stiffness and their hardness require a much higher load to achieve the appropriate tightness. In the French project ANR Pan-H/SEMIEHT, two different sealing solutions were investigated in two different locations of the GENHEPIS-G1 stack. Experiments were carried out with a glass-made seal between the cell and its ceramic support, and with metallic seals between the interconnect and the cell support, in order to seal the gas input and output as well as the cathodic chamber. An initial Garlock seal design has been optimised in order to decrease the seating load. Seals were also manufactured by Garlock. The C-shaped seals are made of two components: an Inconel-X750-made elastic inner part, and a specially profiled Fecralloy-made 'soft' outer lining. The use of Fecralloy enables the generation of an alumina thin layer, which both protects the seal and eases disassembly. In this study, these seals were tested on specific equipments and on actual stacks. It is shown that they are tight enough to achieve the electrolysis tests at 800 deg. C. Therefore a significant breakthrough in high-temperature electrolysis sealing has been achieved. It sheds new light on the actual potential of metallic seals and constitutes a basis for ongoing studies, such as another French project, namely ANR/Pan-H/EMAIL. (authors)

  3. Computerized plutonium laboratory-stack monitoring system

    International Nuclear Information System (INIS)

    The Los Alamos Scientific Laboratory has recently designed and constructed a Plutonium Research and Development Facility to meet design criteria imposed by the United States Energy Research and Development Administration. A primary objective of the design criteria is to assure environmental protection and to reliably monitor plutonium effluent via the ventilation exhaust systems. A state-of-the-art facility exhaust air monitoring system is described which establishes near ideal conditions for evaluating plutonium activity in the stack effluent. Total and static pressure sensing manifolds are incorporated to measure average velocity and integrated total discharge air volume. These data are logged at a computer which receives instrument data through a multiplex scanning system. A multipoint isokinetic sampling assembly with associated instrumentation is described. Continuous air monitors have been designed to sample from the isokinetic sampling assembly and transmit both instantaneous and integrated stack effluent concentration data to the computer and various cathode ray tube displays. The continuous air monitors also serve as room air monitors in the plutonium facility with the primary objective of timely evacuation of personnel if an above tolerance airborne plutonium concentration is detected. Several continuous air monitors are incorporated in the ventilation system to assist in identification of release problem areas

  4. Control of heteroepitaxial stacking by substrate miscut

    Energy Technology Data Exchange (ETDEWEB)

    Bonham, S.W.; Flynn, C.P. [Materials Research Laboratory, University of Illinois at Urbana-Champaign, 104 South Goodwin, Urbana, Illinois 61801 (United States)

    1998-10-01

    We report studies of fcc epitaxial crystals, grown on Nb(110), in which the Nb surface offers a template for selection between the two alternative stackings, {ital ABCA}{hor_ellipsis} and {ital ACBA}{hor_ellipsis} of the fcc close-packed planes. The Nb templates were grown epitaxially about 500 {Angstrom} thick on sapphire (11{bar 2}0), and the fcc material studied was Cu{sub 3}Au. From symmetry it is not possible for the perfect bcc (110) surface to cause any such selection, which is here attributed instead to vicinal miscut: the logarithm of the stacking ratio must be even in miscut along [001] and odd in miscut along [1{bar 1}0]. We find that the measured selectivity is small for miscuts less than about 0.5{degree}, but approaches a factor 10{sup 3} for miscuts along [1{bar 1}0] greater than about 1{degree}. A mechanism for the selection process is discussed in terms of fingered mesostructures that grow on Nb(110) in this regime, as observed first by Zhou, Bonham, and Flynn. {copyright} {ital 1998} {ital The American Physical Society}

  5. Stacking interactions and the twist of DNA

    DEFF Research Database (Denmark)

    Cooper, V.R.; Thonhauser, T.; Puzder, A.;

    2008-01-01

    The importance of stacking interactions for the Twist and stability of DNA is investigated using the fully ab initio van der Waals density functional (vdW-DF).(1,2) Our results highlight the role that binary interactions between adjacent sets of base pairs play in defining the sequence-dependent ......The importance of stacking interactions for the Twist and stability of DNA is investigated using the fully ab initio van der Waals density functional (vdW-DF).(1,2) Our results highlight the role that binary interactions between adjacent sets of base pairs play in defining the sequence......-dependent Twists observed in high-resolution experiments. Furthermore, they demonstrate that additional stability gained by the presence of thymine is due to methyl interactions with neighboring bases, thus adding to our understanding of the mechanisms that contribute to the relative stability of DNA and RNA. Our...... mapping of the energy required to twist each of the 10 unique base pair steps should provide valuable information for future studies of nucleic acid stability and dynamics. The method introduced will enable the nonempirical theoretical study of significantly larger pieces of DNA or DNA/amino acid...

  6. Effects of cooling system parameters on heat transfer in PAFC stack

    Science.gov (United States)

    Abdul-Aziz, Ali A.

    1985-08-01

    Analytical and experimental study for the effects of cooling system parameters on the heat transfer and temperature distribution in the electrode plates of a phosphoric acid fuel-cell has been conducted. An experimental set-up that simulates the operating conditions prevailing in a phosphoric-acid fuel-cell stack was designed and constructed. The set-up was then used to measure the overall heat transfer coefficient, the thermal contact resistance, and the electrode temperature distribution for two different cooling plate configurations. Two types of cooling plate configurations, serpentine and straight, were tested. Air, water, and oil were used as coolants. Measurements for the heat transfer coefficient and the thermal contact resistance were made for various flow rates ranging from 16 to 88 Kg/hr, and stack clamping pressure ranging from O to 3448 Kpa. The experimental results for the overall heat transfer coefficient were utilized to derive mathematical relations for the overall heat transfer coefficient as a function of stack clamping pressure and Reynolds number for the three coolants. The empirically derived formulas were incorporated in a previously developed computer program to predict electrodes temperature distribution and the performance of the stack cooling system. The results obtained were then compared with those available in the literature. The comparison showed maximum deviation of +/- 11%.

  7. A long-term stable power supply µDMFC stack for wireless sensor node applications

    International Nuclear Information System (INIS)

    In this paper, a passive, air-breathing four-cell micro direct methanol fuel cell (µDMFC) stack featuring a fuel delivery structure for long-term and stable power supply is designed, fabricated and tested. The fuel is reserved in a T-shaped tank and diffuses through the porous diffusion layer to the catalyst at the anode. A peak power density of 25.7 mW cm−2 and a maximum power output of 113 mW are achieved with 3 M methanol at room temperature, and the stack can produce 60 mW of power, even though only 5% fuel remains in the reservoir. Combined with a low-input dc–dc convertor, the stack can realize a stable and optional constant voltage output from 1 V–6 V. The stack successfully powered a heavy metal sensor node for water environment monitoring 12 d continuously, with consumption of 10 mL 5 M methanol solution. As such, it is believed to be applicable for powering wireless sensor nodes. (paper)

  8. Effects of cooling system parameters on heat transfer in PAFC stack. Ph.D. Thesis

    Science.gov (United States)

    Abdul-Aziz, Ali A.

    1985-01-01

    Analytical and experimental study for the effects of cooling system parameters on the heat transfer and temperature distribution in the electrode plates of a phosphoric acid fuel-cell has been conducted. An experimental set-up that simulates the operating conditions prevailing in a phosphoric-acid fuel-cell stack was designed and constructed. The set-up was then used to measure the overall heat transfer coefficient, the thermal contact resistance, and the electrode temperature distribution for two different cooling plate configurations. Two types of cooling plate configurations, serpentine and straight, were tested. Air, water, and oil were used as coolants. Measurements for the heat transfer coefficient and the thermal contact resistance were made for various flow rates ranging from 16 to 88 Kg/hr, and stack clamping pressure ranging from O to 3448 Kpa. The experimental results for the overall heat transfer coefficient were utilized to derive mathematical relations for the overall heat transfer coefficient as a function of stack clamping pressure and Reynolds number for the three coolants. The empirically derived formulas were incorporated in a previously developed computer program to predict electrodes temperature distribution and the performance of the stack cooling system. The results obtained were then compared with those available in the literature. The comparison showed maximum deviation of +/- 11%.

  9. A long-term stable power supply µDMFC stack for wireless sensor node applications

    Science.gov (United States)

    Wu, Zonglin; Wang, Xiaohong; Li, Xiaozhao; Xu, Manqi; Liu, Litian

    2014-10-01

    In this paper, a passive, air-breathing four-cell micro direct methanol fuel cell (µDMFC) stack featuring a fuel delivery structure for long-term and stable power supply is designed, fabricated and tested. The fuel is reserved in a T-shaped tank and diffuses through the porous diffusion layer to the catalyst at the anode. A peak power density of 25.7 mW cm-2 and a maximum power output of 113 mW are achieved with 3 M methanol at room temperature, and the stack can produce 60 mW of power, even though only 5% fuel remains in the reservoir. Combined with a low-input dc-dc convertor, the stack can realize a stable and optional constant voltage output from 1 V-6 V. The stack successfully powered a heavy metal sensor node for water environment monitoring 12 d continuously, with consumption of 10 mL 5 M methanol solution. As such, it is believed to be applicable for powering wireless sensor nodes.

  10. Cloud Computing with Open Source Tool :OpenStack

    Directory of Open Access Journals (Sweden)

    Dr. Urmila R. Pol

    2014-09-01

    Full Text Available OpenStack is a especially scalable open source cloud operating system that is a global alliance of developers and cloud computing technologists producing the ubiquitous open source cloud computing platform for public and private clouds. OpenStack provides series of interrelated projects delivering various components for a cloud infrastructure solution as well as controls large pools of storage, compute and networking resources throughout a datacenter that all managed through a Dashboard(Horizon that gives administrators control while empowering their users to provision resources through a web interface.In this paper, we present a overview of Cloud Computing Platform such as, Openstack, Eucalyptus ,CloudStack and Opennebula which is open source software, cloud computing layered model, components of OpenStack, architecture of OpenStack. The aim of this paper is to show mainly importance of OpenStack as a Cloud provider and its installation.

  11. Study of Ce-Pt/γ-Al 2O 3 for the selective oxidation of CO in H 2 for application to PEFCs: Effect of gases

    Science.gov (United States)

    Son, In Hyuk

    In order to supply pure hydrogen to proton exchange membrane (PEM) fuel cells and avoid CO poisoning, selective CO oxidation in H 2 was studied over Ce-Pt/γ-Al 2O 3. Adding the Ce promoted the CO conversion and selectivity of Pt/γ-Al 2O 3 with changing loading weights of Pt and Ce, oxygen concentration, residence time, and the composition of gases (H 2O, CO 2, and N 2). At 250 °C, adding H 2O to the feed gas enhanced the CO conversion due to the water-gas shift reaction. While, adding CO 2 to the feed gas suppressed the CO conversion due to the reversible water-gas shift reaction. In situ BET and XRD tests showed that well-dispersed metallic Pt particles (-2 nm) existed on the Ce oxide over the alumina support, which helps to supply oxygen to the Pt for a high activity of CO oxidation and selectivity.

  12. Implementing Stack E6 via OS Linux Sockets

    Directory of Open Access Journals (Sweden)

    Dmitry A Zaitsev

    2012-06-01

    Full Text Available New software implementation of Ukrainian national stack of networking protocols E6 was presented. Within operating system Linux kernel, families of E6 protocols and addresses were created as well as functions of their processing, in the form of a loadable module. Application of socket technology gives a series of considerable advantages among which unified with other stacks application interface, reuse of the kernel resources facilitating the further development and enterprise implementation of stack E6, engineering corresponding networking devices.

  13. Stacked Heterogeneous Neural Networks for Time Series Forecasting

    Directory of Open Access Journals (Sweden)

    Florin Leon

    2010-01-01

    Full Text Available A hybrid model for time series forecasting is proposed. It is a stacked neural network, containing one normal multilayer perceptron with bipolar sigmoid activation functions, and the other with an exponential activation function in the output layer. As shown by the case studies, the proposed stacked hybrid neural model performs well on a variety of benchmark time series. The combination of weights of the two stack components that leads to optimal performance is also studied.

  14. Conceptual design of 20 kV RF stacking cavity

    International Nuclear Information System (INIS)

    RF stacking process for heavy ions is analyzed in HIRFL cooler storage ring (HIRFL-CSR). A RF cavity for heavy ions stacking is designed according to the requirement of the stacking processes. Its frequency range is 18.0-28.0 MHz and peak RF voltage is 20.0 kV. The other main parameters of the cavity are obtained by using transmission line theory and SUPERFISH code

  15. Complexity of the FIFO Stack-Up Problem

    OpenAIRE

    Gurski, Frank; Rethmann, Jochen; Wanke, Egon

    2013-01-01

    We study the combinatorial FIFO stack-up problem. In delivery industry, bins have to be stacked-up from conveyor belts onto pallets with respect to customer orders. Given k sequences q_1, ..., q_k of labeled bins and a positive integer p, the aim is to stack-up the bins by iteratively removing the first bin of one of the k sequences and put it onto an initially empty pallet of unbounded capacity located at one of p stack-up places. Bins with different pallet labels have to be placed on differ...

  16. GRB neutrino detection via time profile stacking

    CERN Document Server

    van Eijndhoven, Nick

    2007-01-01

    A method is presented for the identification of high-energy neutrinos from gamma ray bursts by means of a large-scale neutrino telescope. The procedure makes use of a time profile stacking technique of observed neutrino induced signals in correlation with satellite observations. By selecting a rather wide time window, a possible difference between the arrival times of the gamma and neutrino signals may also be identified. This might provide insight in the particle production processes at the source. By means of a toy model it will be demonstrated that a statistically significant signal can be obtained with a km$^{3}$-scale neutrino telescope on a sample of 500 gamma ray bursts for a signal rate as low as 1 detectable neutrino for 3% of the bursts.

  17. Rapid Feature Learning with Stacked Linear Denoisers

    CERN Document Server

    Xu, Zhixiang Eddie; Sha, Fei

    2011-01-01

    We investigate unsupervised pre-training of deep architectures as feature generators for "shallow" classifiers. Stacked Denoising Autoencoders (SdA), when used as feature pre-processing tools for SVM classification, can lead to significant improvements in accuracy - however, at the price of a substantial increase in computational cost. In this paper we create a simple algorithm which mimics the layer by layer training of SdAs. However, in contrast to SdAs, our algorithm requires no training through gradient descent as the parameters can be computed in closed-form. It can be implemented in less than 20 lines of MATLABTMand reduces the computation time from several hours to mere seconds. We show that our feature transformation reliably improves the results of SVM classification significantly on all our data sets - often outperforming SdAs and even deep neural networks in three out of four deep learning benchmarks.

  18. Dielectric elastomer generators that stack up

    International Nuclear Information System (INIS)

    This paper reports the design, fabrication, and testing of a soft dielectric elastomer power generator with a volume of less than 1 cm3. The generator is well suited to harvest energy from ambient and from human body motion as it can harvest from low frequency (sub-Hz) motions, and is compact and lightweight. Dielectric elastomers are highly stretchable variable capacitors. Electrical energy is produced when the deformation of a stretched, charged dielectric elastomer is relaxed; like-charges are compressed together and opposite-charges are pushed apart, resulting in an increased voltage. This technology provides an opportunity to produce soft, high energy density generators with unparalleled robustness. Two major issues block this goal: current configurations require rigid frames that maintain the dielectric elastomer in a prestretched state, and high energy densities have come at the expense of short lifetime. This paper presents a self-supporting stacked generator configuration which does not require rigid frames. The generator consists of 48 generator films stacked on top of each other, resulting in a structure that fits within an 11 mm diameter footprint while containing enough active material to produce useful power. To ensure sustainable power production, we also present a mathematical model for designing the electronic control of the generator which optimizes energy production while limiting the electrical stress on the generator below failure limits. When cyclically compressed at 1.6 Hz, our generator produced 1.8 mW of power, which is sufficient for many low-power wireless sensor nodes. This performance compares favorably with similarly scaled electromagnetic, piezoelectric, and electrostatic generators. The generator’s small form factor and ability to harvest useful energy from low frequency motions such as tree swaying or shoe impact provides an opportunity to deliver power to remote wireless sensor nodes or to distributed points in the human body

  19. Dielectric elastomer generators that stack up

    Science.gov (United States)

    McKay, T. G.; Rosset, S.; Anderson, I. A.; Shea, H.

    2015-01-01

    This paper reports the design, fabrication, and testing of a soft dielectric elastomer power generator with a volume of less than 1 cm3. The generator is well suited to harvest energy from ambient and from human body motion as it can harvest from low frequency (sub-Hz) motions, and is compact and lightweight. Dielectric elastomers are highly stretchable variable capacitors. Electrical energy is produced when the deformation of a stretched, charged dielectric elastomer is relaxed; like-charges are compressed together and opposite-charges are pushed apart, resulting in an increased voltage. This technology provides an opportunity to produce soft, high energy density generators with unparalleled robustness. Two major issues block this goal: current configurations require rigid frames that maintain the dielectric elastomer in a prestretched state, and high energy densities have come at the expense of short lifetime. This paper presents a self-supporting stacked generator configuration which does not require rigid frames. The generator consists of 48 generator films stacked on top of each other, resulting in a structure that fits within an 11 mm diameter footprint while containing enough active material to produce useful power. To ensure sustainable power production, we also present a mathematical model for designing the electronic control of the generator which optimizes energy production while limiting the electrical stress on the generator below failure limits. When cyclically compressed at 1.6 Hz, our generator produced 1.8 mW of power, which is sufficient for many low-power wireless sensor nodes. This performance compares favorably with similarly scaled electromagnetic, piezoelectric, and electrostatic generators. The generator’s small form factor and ability to harvest useful energy from low frequency motions such as tree swaying or shoe impact provides an opportunity to deliver power to remote wireless sensor nodes or to distributed points in the human body

  20. Proposal of high efficiency solar cells with closely stacked InAs/In0.48Ga0.52P quantum dot superlattices: Analysis of polarized absorption characteristics via intermediate–band

    International Nuclear Information System (INIS)

    We present a theoretical study of the electronic structures and polarized absorption properties of quantum dot superlattices (QDSLs) using wide–gap matrix material, InAs/In0.48Ga0.52P QDSLs, for realizing intermediate–band solar cells (IBSCs) with two–step photon–absorption. The plane–wave expanded Burt–Foreman operator ordered 8–band k·p theory is used for this calculation, where strain effect and piezoelectric effect are taken into account. We find that the absorption spectra of the second transitions of two–step photon–absorption can be shifted to higher energy region by using In0.48Ga0.52P, which is lattice–matched material to GaAs substrate, as a matrix material instead of GaAs. We also find that the transverse magnetic polarized absorption spectra in InAs/In0.48Ga0.52P QDSL with a separate IB from the rest of the conduction minibands can be shifted to higher energy region by decreasing the QD height. As a result, the second transitions of two–step photon–absorption by the sunlight occur efficiently. These results indicate that InAs/In0.48Ga0.52P QDSLs are suitable material combination of IBSCs toward the realization of ultrahigh efficiency solar cells.