Solar Metal Sulfate-Ammonia Based Thermochemical Water Splitting Cycle for Hydrogen Production

Science.gov (United States)

Huang, Cunping (Inventor); T-Raissi, Ali (Inventor); Muradov, Nazim (Inventor)

2014-01-01

Two classes of hybrid/thermochemical water splitting processes for the production of hydrogen and oxygen have been proposed based on (1) metal sulfate-ammonia cycles (2) metal pyrosulfate-ammonia cycles. Methods and systems for a metal sulfate MSO.sub.4--NH3 cycle for producing H2 and O2 from a closed system including feeding an aqueous (NH3)(4)SO3 solution into a photoctalytic reactor to oxidize the aqueous (NH3)(4)SO3 into aqueous (NH3)(2)SO4 and reduce water to hydrogen, mixing the resulting aqueous (NH3)(2)SO4 with metal oxide (e.g. ZnO) to form a slurry, heating the slurry of aqueous (NH4)(2)SO4 and ZnO(s) in the low temperature reactor to produce a gaseous mixture of NH3 and H2O and solid ZnSO4(s), heating solid ZnSO4 at a high temperature reactor to produce a gaseous mixture of SO2 and O2 and solid product ZnO, mixing the gaseous mixture of SO2 and O2 with an NH3 and H2O stream in an absorber to form aqueous (NH4)(2)SO3 solution and separate O2 for aqueous solution, recycling the resultant solution back to the photoreactor and sending ZnO to mix with aqueous (NH4)(2)SO4 solution to close the water splitting cycle wherein gaseous H2 and O2 are the only products output from the closed ZnSO4--NH3 cycle.

Thermochemical reactivity of 5–15 mol% Fe, Co, Ni, Mn-doped cerium oxides in two-step water-splitting cycle for solar hydrogen production

Energy Technology Data Exchange (ETDEWEB)

Gokon, Nobuyuki, E-mail: ngokon@eng.niigata-u.ac.jp [Center for Transdisciplinary Research, Niigata University, 8050 Ikarashi 2-nocho, Nishi-ku, Niigata 950-2181 (Japan); Suda, Toshinori [Graduate School of Science and Technology, Niigata University, 8050 Ikarashi 2-nocho, Niigata 950-2181 (Japan); Kodama, Tatsuya [Department of Chemistry & Chemical Engineering, Faculty of Engineering, Niigata University, 8050 Ikarashi 2-nocho, Niigata 950-2181 (Japan)

2015-10-10

Highlights: • 5–15 mol% M-doped ceria are examined for thermochemical two-step water-splitting. • 5 mol% Fe- and Co-doped ceria have stoichiometric production of oxygen and hydrogen. • 10–15 mol% Fe- and Mn-doped ceria showed near-stoichiometric production. - Abstract: The thermochemical two-step water-splitting cycle using transition element-doped cerium oxide (M–CeO{sub 2−δ}; M = Fe, Co, Ni, Mn) powders was studied for hydrogen production from water. The oxygen/hydrogen productivity and repeatability of M–CeO{sub 2−δ} materials with M doping contents in the 5–15 mol% range were examined using a thermal reduction (TR) temperature of 1500 °C and water decomposition (WD) temperatures in the 800–1150 °C range. The temperature, steam partial pressure, and steam flow rate in the WD step had an impact on the hydrogen productivity and production rate. 5 mol% Fe- and Co-doped CeO{sub 2−δ} enhances hydrogen productivity by up to 25% on average compared to undoped CeO{sub 2}, and shows stable repeatability of stoichiometric oxygen and hydrogen production for the cyclic thermochemical two-step water-splitting reaction. In addition, 5 mol% Mn-doped CeO{sub 2−δ}, 10 and 15 mol% Fe- and Mn-doped CeO{sub 2−δ} show near stoichiometric reactivities.

Solar hydrogen project - Thermochemical process design

Energy Technology Data Exchange (ETDEWEB)

Allen, D.J.; Ng, L.F.; Rao, M.S.M.; Wu, S.F.; Zoschak, R.J.

1984-08-01

The thermochemical decomposition of water using solar energy offers an elegant way of combining solar and chemical technologies to produce a high quality fuel. The DOE has sponsored Foster Wheeler to develop a process design for a solar water-splitting process based on the sulfuric acid/iodine cycle. The study has centered around the design of a sulfuric acid decomposition reactor and the central receiver. Materials' properties impose severe constraints upon the design of decomposition reactor. In this paper, the constraints imposed on the design are specified and a reactor and receiver design is presented together with a preliminary design of the balance of plant.

R and D thermochemical I-S process at JAERI

International Nuclear Information System (INIS)

Onuki, K.; Kubo, S.; Nakajima, H.; Higashi, S.; Kasahara, S.; Ishiyama, S.; Okuda, H.

2004-01-01

The Japan Atomic Energy Research Institute (JAERI) has conducted a study on the thermochemical water-splitting process of the iodine-sulfur family (IS process). In the IS process, water will react with iodine and sulfur dioxide to produce hydrogen iodide and sulfuric acid, which are then decomposed thermally to produce hydrogen and oxygen. High temperature nuclear heat, mainly supplied by a High Temperature Gas-cooled Reactor (HTGR), is used to drive the endothermic decomposition of sulfuric acid. JAERI has demonstrated the feasibility of the water-splitting hydrogen production process by carrying out laboratory-scale experiments in which combined operation of fundamental reactions and separations using the IS process was performed continuously. At present, the hydrogen production test is continuing, using a scaled-up glass apparatus. Corrosion-resistant materials for constructing a large-scale plant and process improvements by introducing advanced separation techniques, such as membrane separation, are under study. Future R and D items are discussed based on the present activities. (author)

Thermochemical production of hydrogen from water

International Nuclear Information System (INIS)

Funk, J.E.; Conger, W.L.; Carty, R.H.; Barker, R.E.

1975-01-01

A review of recent developments in the selection and evaluation of multi-step thermochemical water-splitting cycles is presented. A computerized and thermodynamic and chemical engineering analysis procedure is discussed with calculates, among other things, the thermal efficiency of the process which is defined to be the ratio of the enthalpy change for water decomposition to the total thermal energy required by the process. Changes in the thermodynamic state in each step of the process are also determined. Engineering considerations such as the effect of approach to equilibrium in the chemical reaction steps on the work of separation, and the magnitude of the recycle streams are included. Important practical matters such as thermal regeneration in the product and reactant streams are dealt with in some detail. The effect of reaction temperature on thermal efficiency is described and the use of the analysis procedure is demonstrated by applying it to several processes. (author)

Comparing Electrochemical and Biological Water Splitting

DEFF Research Database (Denmark)

Rossmeisl, Jan; Dimitrievski, Kristian; Siegbahn, P.

2007-01-01

On the basis of density functional theory calculations, we compare the free energies of key intermediates in the water splitting reaction over transition metal oxide surfaces to those of the Mn cluster in photo system II. In spite of the very different environments in the enzyme system and on the......On the basis of density functional theory calculations, we compare the free energies of key intermediates in the water splitting reaction over transition metal oxide surfaces to those of the Mn cluster in photo system II. In spite of the very different environments in the enzyme system...... and on the inorganic catalyst surface of an acidic electrolysis cell, the thermochemical features of the catalysts can be directly compared. We suggest a simple test for a thermochemically optimal catalyst. We show that, although both the RuO2 surface and the Mn cluster in photo system II are quite close to optimal...

Hydrogen production by thermochemical cycles of water splitting coupled to a solar energy source

International Nuclear Information System (INIS)

Charvin, P.

2007-11-01

The aim of this work is to identify, to test and to estimate new thermochemical cycles able to efficiently produce hydrogen from concentrated solar energy. In fact, the aim is to propose a hydrogen production way presenting a global energetic yield similar to electrolysis, that is to say 20-25%, electrolysis being at the present time the most advanced current process for a clean hydrogen production from water. After a first chapter dealing with the past and present researches on thermochemical cycles, the first step of this study has consisted on a selection of a limited number of thermochemical cycles able to produce great quantities of hydrogen from concentrated solar energy. It has consisted in particular on a review of the thermochemical cycles present in literature, on a first selection from argued criteria, and on an exergetic and thermodynamic analysis of the retained cycles for a first estimation of their potential. The second step of this study deals with the experimental study of all the chemical reactions occurring in the retained cycles. Two different oxides cycles have been particularly chosen and the aims are to demonstrate the feasibility of the reactions, to identify the optimal experimental conditions, to estimate and optimize the kinetics and the chemical yields. The following part of this work deals with the design, the modeling and the test of a solar reactor. A CFD modeling of a high temperature reactor of cavity type allows to identify the main heat losses of the reactor and to optimize the geometry of the cavity. A dynamic modeling of the reactor gives data on its behaviour in transient regime and under a real solar flux. The results of the preliminary experimental results are presented. The last part of this study deals with a process analysis of the thermochemical cycles from the results of the experimental study (experimental conditions, yields...). The matter and energy balances are established in order to estimate the global energetic

A pilot test plan of the thermochemical water-splitting iodine-sulfur process

International Nuclear Information System (INIS)

Kubo, Shinji; Kasahara, Seiji; Okuda, Hiroyuki; Terada, Atsuhiko; Tanaka, Nobuyuki; Inaba, Yoshitomo; Ohashi, Hirofumi; Inagaki, Yoshiyuki; Onuki, Kaoru; Hino, Ryutaro

2004-01-01

Research and development (R and D) of hydrogen production systems using high-temperature gas-cooled reactors (HTGR) are being conducted by the Japan Atomic Research Institute (JAERI). To develop the systems, superior hydrogen production methods are essential. The thermochemical hydrogen production cycle, the IS (iodine-sulfur) process, is a prospective candidate, in which heat supplied by HTGR can be consumed for the thermal driving load. With this attractive feature, JAERI will conduct pilot-scale tests, aiming to establish technical bases for practical plant designs using HTGR. The hydrogen will be produced at a maximum rate of 30 m 3 /h, continuously using high-temperature helium gas supplied by a helium gas loop, with an electric heater of about 400 kW. The plant will employ an advanced hydroiodic acid-processing device for efficient hydrogen production, and the usefulness of the device was confirmed from mass and heat balance analysis. Through design works and the hydrogen production tests, valuable data for construction and operation will be acquired to evaluate detailed process performance for practical systems. After completing the pilot-scale tests, JAERI will move onto the next R and D step, which will be demonstrations of the IS process to which heat is supplied from a high-temperature engineering test reactor (HTTR)

Advances in hydrogen production by thermochemical water decomposition: A review

International Nuclear Information System (INIS)

Rosen, Marc A.

2010-01-01

Hydrogen demand as an energy currency is anticipated to rise significantly in the future, with the emergence of a hydrogen economy. Hydrogen production is a key component of a hydrogen economy. Several production processes are commercially available, while others are under development including thermochemical water decomposition, which has numerous advantages over other hydrogen production processes. Recent advances in hydrogen production by thermochemical water decomposition are reviewed here. Hydrogen production from non-fossil energy sources such as nuclear and solar is emphasized, as are efforts to lower the temperatures required in thermochemical cycles so as to expand the range of potential heat supplies. Limiting efficiencies are explained and the need to apply exergy analysis is illustrated. The copper-chlorine thermochemical cycle is considered as a case study. It is concluded that developments of improved processes for hydrogen production via thermochemical water decomposition are likely to continue, thermochemical hydrogen production using such non-fossil energy will likely become commercial, and improved efficiencies are expected to be obtained with advanced methodologies like exergy analysis. Although numerous advances have been made on sulphur-iodine cycles, the copper-chlorine cycle has significant potential due to its requirement for process heat at lower temperatures than most other thermochemical processes.

Construction apparatus for thermochemical hydrogen production process

Energy Technology Data Exchange (ETDEWEB)

Kubo, S.; Nakajima, H.; Higashi, S.; Onuki, K.; Akino, S.S.N. [Japan Atomic Energy Research Inst., Ibaraki-ken (Japan). Nuclear Heat Utilization Engineering Lab

2001-06-01

Studies have been carried out at the Japan Atomic Energy Research Institute (JAERI) on hydrogen production through thermochemical processes such as water-splitting. These studies are classified with iodine-sulphur cycle studies using heat from high temperature gas-cooled reactors. An experimental apparatus was constructed with fluorine resin, glass and quartz. It can produce hydrogen at a rate of 50 litres per hour. Electricity provides the heat required for the operation. The closed chemical process requires special control techniques. The process flow diagram for the apparatus was designed based on the results of previous studies including one where hydrogen production was successfully achieved at a rate of one liter per hour for 48 hours. Experimental operations under atmospheric pressure will be carried out for the next four years to develop the process. The data will be used in the next research and development programs aimed at designing a bench-scale apparatus. 7 refs., 1 tab., 8 figs.

Life cycle assessment of nuclear-based hydrogen production via thermochemical water splitting using a copper-chlorine (Cu-Cl) cycle

Science.gov (United States)

Ozbilen, Ahmet Ziyaettin

The energy carrier hydrogen is expected to solve some energy challenges. Since its oxidation does not emit greenhouse gases (GHGs), its use does not contribute to climate change, provided that it is derived from clean energy sources. Thermochemical water splitting using a Cu-Cl cycle, linked with a nuclear super-critical water cooled reactor (SCWR), which is being considered as a Generation IV nuclear reactor, is a promising option for hydrogen production. In this thesis, a comparative environmental study is reported of the three-, four- and five-step Cu-Cl thermochemical water splitting cycles with various other hydrogen production methods. The investigation uses life cycle assessment (LCA), which is an analytical tool to identify and quantify environmentally critical phases during the life cycle of a system or a product and/or to evaluate and decrease the overall environmental impact of the system or product. The LCA results for the hydrogen production processes indicate that the four-step Cu-Cl cycle has lower environmental impacts than the three- and five-step Cu-Cl cycles due to its lower thermal energy requirement. Parametric studies show that acidification potentials (APs) and global warming potentials (GWPs) for the four-step Cu-Cl cycle can be reduced from 0.0031 to 0.0028 kg SO2-eq and from 0.63 to 0.55 kg CO2-eq, respectively, if the lifetime of the system increases from 10 to 100 years. Moreover, the comparative study shows that the nuclear-based S-I and the four-step Cu-Cl cycles are the most environmentally benign hydrogen production methods in terms of AP and GWP. GWPs of the S-I and the four-step Cu-Cl cycles are 0.412 and 0.559 kg CO2-eq for reference case which has a lifetime of 60 years. Also, the corresponding APs of these cycles are 0.00241 and 0.00284 kg SO2-eq. It is also found that an increase in hydrogen plant efficiency from 0.36 to 0.65 decreases the GWP from 0.902 to 0.412 kg CO 2-eq and the AP from 0.00459 to 0.00209 kg SO2-eq for the

Giant onsite electronic entropy enhances the performance of ceria for water splitting.

Science.gov (United States)

Naghavi, S Shahab; Emery, Antoine A; Hansen, Heine A; Zhou, Fei; Ozolins, Vidvuds; Wolverton, Chris

2017-08-18

Previous studies have shown that a large solid-state entropy of reduction increases the thermodynamic efficiency of metal oxides, such as ceria, for two-step thermochemical water splitting cycles. In this context, the configurational entropy arising from oxygen off-stoichiometry in the oxide, has been the focus of most previous work. Here we report a different source of entropy, the onsite electronic configurational entropy, arising from coupling between orbital and spin angular momenta in lanthanide f orbitals. We find that onsite electronic configurational entropy is sizable in all lanthanides, and reaches a maximum value of ≈4.7 k B per oxygen vacancy for Ce 4+ /Ce 3+ reduction. This unique and large positive entropy source in ceria explains its excellent performance for high-temperature catalytic redox reactions such as water splitting. Our calculations also show that terbium dioxide has a high electronic entropy and thus could also be a potential candidate for solar thermochemical reactions.Solid-state entropy of reduction increases the thermodynamic efficiency of ceria for two-step thermochemical water splitting. Here, the authors report a large and different source of entropy, the onsite electronic configurational entropy arising from coupling between orbital and spin angular momenta in f orbitals.

System and process for producing fuel with a methane thermochemical cycle

Science.gov (United States)

Diver, Richard B.

2015-12-15

A thermochemical process and system for producing fuel are provided. The thermochemical process includes reducing an oxygenated-hydrocarbon to form an alkane and using the alkane in a reforming reaction as a reducing agent for water, a reducing agent for carbon dioxide, or a combination thereof. Another thermochemical process includes reducing a metal oxide to form a reduced metal oxide, reducing an oxygenated-hydrocarbon with the reduced metal oxide to form an alkane, and using the alkane in a reforming reaction as a reducing agent for water, a reducing agent for carbon dioxide, or a combination thereof. The system includes a reformer configured to perform a thermochemical process.

Hydrogen Production From Water By Thermo-Chemical Methods (UT-3): Evaluation of Side Reactions By Simulation Process

International Nuclear Information System (INIS)

Rusli, A.

1997-01-01

Hydogen fuel with its advantages will be able to replace all the positions of fossil fuels post o il and gas or migas . Among the advantages of hydrogen fuel are pollution free, abundant of raw material in the form of water molecule, flexible in application, able to stroge and transport as well as fossil energy sources (oil and gas). Hydogen could be produced from water by means of thermochemical, thermolysis, photolysis and electrolysis. Nuclear heat (HTGR), solar heat or waste heat from steel industry can be used as energy source for these processes. In case of thermochemical method, some problems realated to production process should be studied and evaluated. Simulation is considered can be applied to study the effects of side reactions and also to resolve its problems in hydrogen production process. In this paper is reported the evalution results of hydrogen production process by thermochemical (UT-3) through both of the experimental and computer simulation. It has been proposed a new flow chart of hydrogen production to achieve the hydrogen production continuously. A simulator has been developed based on experimental data and related mathematical equations. This simulator can be used to scle-up the UT-3 thermochemical cycle for hydrogen production process

Thermo-chemical production of hydrogen from water by metal oxides fixed on ceramic substrates

International Nuclear Information System (INIS)

Roeb, M.; Monnerie, N.; Schmitz, M.; Sattler, C.; Konstandopoulos, A.G.; Agrafiotis, C.; Zaspalis, V.T.; Nalbandian, L.; Steele, A.; Stobbe, P.

2006-01-01

In the European project HYDROSOL a simple two-step thermo-chemical cycle process has been developed and investigated. It is based on metal oxide redox pair systems, which can split water molecules by abstracting oxygen atoms and reversibly incorporating them into their lattice. If concentrated solar radiation is used as the heat source one has a promising method in hand to produce hydrogen without any environmentally critical emissions. The basic idea is to combine a support capable of achieving high temperatures when heated by concentrated solar radiation, with a redox pair system suitable for water dissociation and at the same time for regeneration at these temperatures, so that complete operation of the whole process could be achieved by a single solar energy converter. The feasibility of the process has proven possible in a mini-plant scale using concentrated sunlight provided by the solar furnace in Cologne. Suitable redox materials as coatings and a dedicated receiver-reactor have been developed to produce hydrogen with significant conversions by repeating several subsequent water splitting and regeneration steps. In a design study a possible way of operating the process in commercial scale is demonstrated. (authors)

Generation of H2 and CO by solar thermochemical splitting of H2O and CO2 by employing metal oxides

International Nuclear Information System (INIS)

Rao, C.N.R.; Dey, Sunita

2016-01-01

Generation of H 2 and CO by splitting H 2 O and CO 2 respectively constitutes an important aspect of the present-day concerns with energy and environment. The solar thermochemical route making use of metal oxides is a viable means of accomplishing these reduction reactions. The method essentially involves reducing a metal oxide by heating and passing H 2 O or CO 2 over the nonstoichiometric oxide to cause reverse oxidation by abstracting oxygen from H 2 O or CO 2 . While ceria, perovskites and other oxides have been investigated for this purpose, recent studies have demonstrated the superior performance of perovskites of the type Ln 1−x A x Mn 1−y M y O 3 (Ln=rare earth, A=alkaline earth, M=various +2 and +3 metal ions), in the thermochemical generation of H 2 and CO. We present the important results obtained hitherto to point out how the alkaine earth and the Ln ions, specially the radius of the latter, determine the performance of the perovskites. The encouraging results obtained are exemplefied by Y 0.5 Sr 0.5 MnO 3 which releases 483 µmol/g of O 2 at 1673 K and produces 757 µmol/g of CO from CO 2 at 1173 K. The production of H 2 from H 2 O is also quite appreciable. Modification of the B site ion of the perovskite also affects the performance. In addition to perovskites, we present the generation of H 2 based on the Mn 3 O 4 /NaMnO 2 cycle briefly. - Graphical abstract: Ln 0.5 A 0.5 Mn 1−x M x O 3 (Ln=lanthanide; A=Ca, Sr; M=Al, Ga, Sc, Mg, Cr, Fe, Co) perovskites are employed for the two step thermochemical splitting of CO 2 and H 2 O for the generation of CO and H 2 . - Highlights: • Perovskite oxides based on Mn are ideal for the two-step thermochemical splitting of CO 2 and H 2 O. • In Ln 1−x A x MnO 3 perovskite (Ln=rare earth, A=alkaline earth) both Ln and A ions play major roles in the thermochemical process. • H 2 O splitting is also achieved by the use of the Mn 3 O 4 -sodium carbonate system. • Thermochemical splitting of CO 2 and H

Novel separation process of gaseous mixture of SO2 and O2 with ionic liquid for hydrogen production in thermochemical sulfur-iodine water splitting cycle

International Nuclear Information System (INIS)

Kim, Chang Soo; Gong, Gyeong Taek; Yoo, Kye Sang; Kim, Honggon; Lee, Byoung Gwon; Ahn, Byoung Sung; Jung, Kwang Deog; Lee, Ki Yong; Song, Kwang Ho

2007-01-01

Sulfur-Iodine cycle is the most promising thermochemical cycle for water splitting to produce hydrogen which can replace the fossil fuels in the future. As a sub-cycle in the thermochemical Sulfur-Iodine water splitting cycle, sulfuric acid (H 2 SO 4 ) decomposes into oxygen (O 2 ) and sulfur dioxide (SO 2 ) which should be separated for the recycle of SO 2 into the sulfuric acid generation reaction (Bunsen Reaction). In this study, absorption and desorption process of SO 2 by ionic liquid which is useful for the recycle of SO 2 into sulfuric acid generation reaction after sulfuric acid decomposition in the thermochemical Sulfur-Iodine cycle is investigated. At first, the operability as an absorbent for the SO 2 absorption and desorption at high temperature without the volatilization of absorbents which is not suitable for the recycle of absorbent-free SO 2 after the absorption process. The temperature range of operability is determined by TGA and DTA analysis. Most of ionic liquids investigated are applicable at high temperature desorption without volatility around 300 deg. C except [BMIm] Cl, and [BMIm] OAc which show the decomposition of ionic liquids. To evaluate the capability of SO 2 absorption, each ionic liquid is located in the absorption tube and gaseous SO 2 is bubbled into the ionic liquid. During the bubbling, the weight of the system is measured and converted into the absorbed SO 2 amount at each temperature controlled by the heater. Saturated amounts of absorbed SO 2 by ionic liquids at 50 deg. C are presented. The effect of anions for the SO 2 absorption capability is shown in the order of Cl, OAc, MeSO 3 , BF 4 , MeSO 4 , PF 6 , and HSO 4 when they are combined with [BMIm] cation. [BMIm]Cl has the largest amount of SO 2 absorbed which can be the most promising absorbent; however, from the point of operability at high temperature which includes desorption process, [BMIm]Cl is vulnerable to high temperature around 250 deg. C based on the TGA

Analysis of the hybrid copper oxide-copper sulfate cycle for the thermochemical splitting of water for hydrogen production

International Nuclear Information System (INIS)

Gonzales, Ross B.; Law, Victor J.; Prindle, John C.

2009-01-01

The hybrid copper oxide-copper sulfate water-splitting thermochemical cycle involves two principal steps: (1) hydrogen production from the electrolysis of water, SO 2 (g) and CuO(s) at room temperature and (2) the thermal decomposition of the CuSO 4 product to form oxygen and SO 2 , which is recycled to the first step. A four-reaction version of the cycle (known in the literature as Cycle H-5) was used as the basis of the present work. For several of the four reactions, a rotating batch reactor sequence is proposed in order to overcome equilibrium limitations. Pinch technology was used to optimize heat integration. Sensitivity analyses revealed it to be economically more attractive to use a 10 C approach to minimize heat loss (rather than 20 C). Using standard Aspen Plus features and the Peng-Robinson equation of state for separations involving oxygen and sulfur oxides, a proposed flowsheet for the cycle was generated to yield ''Level 3'' results. A cost analysis of the designed plant (producing 100 million kmol/yr hydrogen) indicates a total major equipment cost of approximately $45 million. This translates to a turnkey plant price (excluding the cost of the high-temperature heat source or electrolyzer internals) of approximately $360 million. Based on a $2.50/kg selling price for hydrogen, gross annual revenue could be on the order of $500 million, resulting in a reasonable payback period when all capital and operating costs are considered. Previous efficiency estimates using Level 1 and Level 2 methods gave the process efficiency in the neighborhood of 47-48%. The Level 3 efficiency computation was 24-25% depending on the approach temperature used for recuperation. If the low quality heat rejected by the process can be recovered and used elsewhere, the Level 3 analysis could be as high as 51-53%. (author)

Development of hydraulic analysis code for optimizing thermo-chemical is process reactors

International Nuclear Information System (INIS)

Terada, Atsuhiko; Hino, Ryutaro; Hirayama, Toshio; Nakajima, Norihiro; Sugiyama, Hitoshi

2007-01-01

The Japan Atomic Energy Agency has been conducting study on thermochemical IS process for water splitting hydrogen production. Based on the test results and know-how obtained through the bench-scale test, a pilot test plant, which has a hydrogen production performance of 30 Nm 3 /h, is being designed conceptually as the next step of the IS process development. In design of the IS pilot plant, it is important to make chemical reactors compact with high performance from the viewpoint of plant cost reduction. A new hydraulic analytical code has been developed for optimizing mixing performance of multi-phase flow involving chemical reactions especially in the Bunsen reactor. Complex flow pattern with gas-liquid chemical interaction involving flow instability will be characterized in the Bunsen reactor. Preliminary analytical results obtained with above mentioned code, especially flow patterns induced by swirling flow agreed well with that measured by water experiments, which showed vortex breakdown pattern in a simplified Bunsen reactor. (author)

Conceptual design of SO3 decomposer for thermo-chemical iodine-sulfur process pilot plant

International Nuclear Information System (INIS)

Akihiro Kanagawa; Seiji Kasahara; Atsuhiko Terada; Shinji Kubo; Ryutaro Hino; Yoshiyuki Kawahara; Masaharu Watabe; Hiroshi Fukui; Kazuo Ishino; Toshio Takahashi

2005-01-01

Thermo-chemical water-splitting cycle is a method to make an effective use of the high temperature nuclear heat for hydrogen production. Japan Atomic Energy Research Institute (JAERI) has been conducting R and D on HTGR and also on thermo-chemical hydrogen production by using a thermo-chemical iodine-sulfur cycle (IS process). Based on the test results and know-how obtained through a bench-scale tests of hydrogen production of about 30 NL/hr, JAERI has a plan to construct a pilot test plant heated by high temperature helium gas, which has a hydrogen production performance of 30 Nm 3 /hr and will be operated under the high pressure up to 2 MPa. One of the key components of the pilot test plant is a SO 3 decomposer under high temperature conditions up to 850 degree C and high pressure up to 2 MPa. In this paper, a concept of the SO 3 decomposer for the pilot test plant fabricated with SiC ceramics, a corrosion-resistant material is investigated. Preliminary analyses on temperature and flow-rate distributions in the SO 3 decomposer and on thermal stress were carried out. A SO 3 decomposer model was experimentally manufactured. (authors)

Mitigation of climate change via a copper-chlorine hybrid thermochemical water splitting cycle for hydrogen production from nuclear energy

International Nuclear Information System (INIS)

Orhan, M.F.; Dincer, I.; Rosen, M.A.

2009-01-01

Concerns regarding climate change have motivated research on clean energy resources. While many energy resources have limitations, nuclear energy has the potential to supply a significant share of energy supply without contributing to climate change. Nuclear energy has been used mainly for electric power generation, but hydrogen production via thermochemical water decomposition provides another option for the utilization of nuclear thermal energy. This paper describes nuclear-based hydrogen production technologies and discusses the role of the Cu-Cl cycle for thermochemical water decomposition, potentially driven in part by waste heat from a nuclear generating station, in reducing greenhouse gas emissions. (author)

Hybrid Thermochemical/Biological Processing

Science.gov (United States)

Brown, Robert C.

The conventional view of biorefineries is that lignocellulosic plant material will be fractionated into cellulose, hemicellulose, lignin, and terpenes before these components are biochemically converted into market products. Occasionally, these plants include a thermochemical step at the end of the process to convert recalcitrant plant components or mixed waste streams into heat to meet thermal energy demands elsewhere in the facility. However, another possibility for converting high-fiber plant materials is to start by thermochemically processing it into a uniform intermediate product that can be biologically converted into a bio-based product. This alternative route to bio-based products is known as hybrid thermochemical/biological processing. There are two distinct approaches to hybrid processing: (a) gasification followed by fermentation of the resulting gaseous mixture of carbon monoxide (CO), hydrogen (H2), and carbon dioxide (CO2) and (b) fast pyrolysis followed by hydrolysis and/or fermentation of the anhydrosugars found in the resulting bio-oil. This article explores this "cart before the horse" approach to biorefineries.

Copper oxide--copper sulfate water-splitting cycle

Energy Technology Data Exchange (ETDEWEB)

Foh, S. E.; Schreiber, J. D.; Dafler, J. R.

1978-08-01

A hybrid copper oxide--copper sulfate thermochemical water-splitting cycle, IGT's H-5, has been demonstrated in the laboratory with recycled materials. The optimum configuration and operating conditions for the electrolytic hydrogen-producing step have not yet been defined. With cooperative funding (A.G.A./G.R.I./DOE) a conceptual flowsheet was developed for this cycle and a load-line efficiency of about 37% calculated. This figure is the result of a single iteration on the original base case flow sheet and compares well with the values calculated for other processes at this stage of development. An iterative optimization of process conditions would improve efficiency. The data required to perform an economic analysis are not yet available and the electrolysis step must be more fully defined. An attractive process efficiency, relatively few corrosive materials, and few gas-phase separations are attributes of Cycle H-5 that lead us to believe hydrogen costs (to be developed during future analyses) would be improved significantly over similar processes analyzed to date.

Renewable hydrogen production via thermochemical/electrochemical coupling

Energy Technology Data Exchange (ETDEWEB)

Ambrosini, Andrea [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Babiniec, Sean Michael [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Miller, James E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2017-10-01

A coupled electrochemical/thermochemical cycle was investigated to produce hydrogen from renewable resources. Like a conventional thermochemical cycle, this cycle leverages chemical energy stored in a thermochemical working material that is reduced thermally by solar energy. However, in this concept, the stored chemical energy only needs to be partially, but not fully, capable of splitting steam to produce hydrogen. To complete the process, a proton-conducting membrane is driven to separate hydrogen as it is produced, thus shifting the thermodynamics toward further hydrogen production. This novel coupled-cycle concept provides several benefits. First, the required oxidation enthalpy of the reversible thermochemical material is reduced, enabling the process to occur at lower temperatures. Second, removing the requirement for spontaneous steam-splitting widens the scope of materials compositions, allowing for less expensive/more abundant elements to be used. Lastly, thermodynamics calculations suggest that this concept can potentially reach higher efficiencies than photovoltaic-to-electrolysis hydrogen production methods. This Exploratory Express LDRD involved assessing the practical feasibility of the proposed coupled cycle. A test stand was designed and constructed and proton-conducting membranes were synthesized. While the full proof of concept was not achieved, the individual components of the experiment were validated and new capabilities that can be leveraged by a variety of programs were developed.

Coupling of copper-chloride hybrid thermochemical water splitting cycle with a desalination plant for hydrogen production from nuclear energy

International Nuclear Information System (INIS)

Orhan, Mehmet F.; Dincer, Ibrahim; Naterer, Greg F.; Rosen, Marc A.

2010-01-01

Energy and environmental concerns have motivated research on clean energy resources. Nuclear energy has the potential to provide a significant share of energy supply without contributing to environmental emissions and climate change. Nuclear energy has been used mainly for electric power generation, but hydrogen production via thermochemical water decomposition provides another pathway for the utilization of nuclear thermal energy. One option for nuclear-based hydrogen production via thermochemical water decomposition uses a copper-chloride (Cu-Cl) cycle. Another societal concern relates to supplies of fresh water. Thus, to avoid causing one problem while solving another, hydrogen could be produced from seawater rather than limited fresh water sources. In this study we analyze a coupling of the Cu-Cl cycle with a desalination plant for hydrogen production from nuclear energy and seawater. Desalination technologies are reviewed comprehensively to determine the most appropriate option for the Cu-Cl cycle and a thermodynamic analysis and several parametric studies of this coupled system are presented for various configurations. (author)

Generation of H{sub 2} and CO by solar thermochemical splitting of H{sub 2}O and CO{sub 2} by employing metal oxides

Energy Technology Data Exchange (ETDEWEB)

Rao, C.N.R., E-mail: cnrrao@jncasr.ac.in; Dey, Sunita

2016-10-15

in the thermochemical process. • H{sub 2}O splitting is also achieved by the use of the Mn{sub 3}O{sub 4}-sodium carbonate system. • Thermochemical splitting of CO{sub 2} and H{sub 2}O using perovskite oxides is explained. • Mn based perovskites.

Technical and thermodynamic problems of medium-temperature membrane processes, illustrated by the example of water splitting

International Nuclear Information System (INIS)

Behr, F.

1983-01-01

The author discusses the economic, technical, and thermodynamic aspects of hydrogen production from water by means of nuclear process heat and then proceeds to describe membranes used in electrolysis cells and in systems in which thermochemical or hybrid processes take place. (GG) [de

Giant onsite electronic entropy enhances the performance of ceria for water splitting

DEFF Research Database (Denmark)

Naghavi, S. Shahab; Emery, Antoine A.; Hansen, Heine Anton

2017-01-01

lanthanides, and reaches a maximum value of ≈4.7 kB per oxygen vacancy for Ce4+/Ce3+ reduction. This unique and large positive entropy source in ceria explains its excellent performance for high-temperature catalytic redox reactions such as water splitting. Our calculations also show that terbium dioxide has...... a high electronic entropy and thus could also be a potential candidate for solar thermochemical reactions....

Solar High Temperature Water-Splitting Cycle with Quantum Boost

Energy Technology Data Exchange (ETDEWEB)

Taylor, Robin [SAIC; Davenport, Roger [SAIC; Talbot, Jan [UCSD; Herz, Richard [UCSD; Genders, David [Electrosynthesis Co.; Symons, Peter [Electrosynthesis Co.; Brown, Lloyd [TChemE

2014-04-25

A sulfur family chemical cycle having ammonia as the working fluid and reagent was developed as a cost-effective and efficient hydrogen production technology based on a solar thermochemical water-splitting cycle. The sulfur ammonia (SA) cycle is a renewable and sustainable process that is unique in that it is an all-fluid cycle (i.e., with no solids handling). It uses a moderate temperature solar plant with the solar receiver operating at 800°C. All electricity needed is generated internally from recovered heat. The plant would operate continuously with low cost storage and it is a good potential solar thermochemical hydrogen production cycle for reaching the DOE cost goals. Two approaches were considered for the hydrogen production step of the SA cycle: (1) photocatalytic, and (2) electrolytic oxidation of ammonium sulfite to ammonium sulfate in aqueous solutions. Also, two sub-cycles were evaluated for the oxygen evolution side of the SA cycle: (1) zinc sulfate/zinc oxide, and (2) potassium sulfate/potassium pyrosulfate. The laboratory testing and optimization of all the process steps for each version of the SA cycle were proven in the laboratory or have been fully demonstrated by others, but further optimization is still possible and needed. The solar configuration evolved to a 50 MW(thermal) central receiver system with a North heliostat field, a cavity receiver, and NaCl molten salt storage to allow continuous operation. The H2A economic model was used to optimize and trade-off SA cycle configurations. Parametric studies of chemical plant performance have indicated process efficiencies of ~20%. Although the current process efficiency is technically acceptable, an increased efficiency is needed if the DOE cost targets are to be reached. There are two interrelated areas in which there is the potential for significant efficiency improvements: electrolysis cell voltage and excessive water vaporization. Methods to significantly reduce water evaporation are

Applicability test of glass lining material for high-temperature acidic solutions of sulfuric acid in thermochemical water-splitting IS process

International Nuclear Information System (INIS)

Iwatsuki, Jin; Tanaka, Nobuyuki; Terada, Atsuhiko; Onuki, Kaoru; Watanabe, Yutaka

2010-01-01

A key issue for realizing the thermochemical IS process for hydrogen production is the selection of materials for working with high-temperature acidic solutions of sulfuric acid and hydriodic acid. Glass lining material is a promising candidate, which is composed of steel having good strength and glass having good corrosion resistance. Since the applicability of glass lining material depends strongly on the service condition, corrosion tests using glass used in glass lining material and heat cycle tests using glass lining piping were carried out to examine the possibility of using the glass lining material with high-temperature acidic solutions of sulfuric acid. It was confirmed that the glass lining materials exhibited sufficient corrosion resistance and heat resistance in high-temperature sulfuric acid of the IS process. (author)

Process simulation of nuclear-based thermochemical hydrogen production with a copper-chlorine cycle

International Nuclear Information System (INIS)

Chukwu, C.C.; Naterer, G.F.; Rosen, M.A.

2008-01-01

Thermochemical processes for hydrogen production driven by nuclear energy are promising alternatives to existing technologies for large-scale commercial production of hydrogen without fossil fuels. The copper-chlorine (Cu-Cl) cycle, in which water is decomposed into hydrogen and oxygen, is promising for thermochemical hydrogen production in conjunction with a Supercritical Water Cooled Reactor. Here, the cycle efficiency is examined using the Aspen Plus process simulation code. Possible efficiency improvements are discussed. The results are expected to assist the development of a lab-scale cycle demonstration, which is currently being undertaken at University of Ontario Institute of Technology in collaboration with numerous partners. (author)

Cyclic thermochemical process for producing hydrogen using cerium-titanium compounds

Science.gov (United States)

Bamberger, C.E.

A thermochemical cyclic process for producing hydrogen employs the reaction between ceric oxide and titanium dioxide to form cerium titanate and oxygen. The titanate is treated with an alkali metal hydroxide to give hydrogen, ceric oxide, an alkali metal titanate and water. Alkali metal titanate and water are boiled to give titanium dioxide which, along with ceric oxide, is recycled.

A process for the thermochemical poduction of H2

International Nuclear Information System (INIS)

Norman, J.H.; Russell, J.L. Jr.; Porter, J.T. II; McCorkl, K.H.; Roemer, T.S.; Sharp, Robert.

1976-01-01

A process is described for the thermochemical production of H 2 from water. HI 3 and H 2 SO 4 are prepared by chemical reaction between I 2 , SO 2 and H 2 O. Then HI 3 is heated and decomposed into H 2 and I 2 . The heat is produced by a nuclear reactor [fr

Energy balance calculations and assessment of two thermochemical sulfur cycles

International Nuclear Information System (INIS)

Leger, D.; Lessart, P.; Manaud, J.P.; Benizri, R.; Courvoisier, P.

1978-01-01

Thermochemical cyclic processes which include the highly endothermal decomposition of sulphuric acid are promising for hydrogen production by water-splitting. Our study is directed toward two cycles of this family, each involving the formation and decomposition of sulphuric acid and including other reactions using iron sulphide for the first and oxides and bromides of copper and magnesium for the second. Thermochemical analyses of the two cycles are undertaken. Thermodynamic studies of the reactions are carried out, taking into account possible side-reactions. The concentration of reactants, products and by-products resulting from simultaneous equilibria are calculated, the problems of separation thoroughly studied and the flow-diagrams of the processes drawn up. Using as heat source the helium leaving a 3000 MWth high temperature nuclear reactor and organizing internal heat exchange the enthalpy diagrams are drawn up and the net energy balances evaluated. The overall thermal efficiencies are about 28%, a value corresponding to non-optimized process schemes. Possible improvements aiming at energy-saving and increased efficiency are indicated

Particulate photocatalysts for overall water splitting

Science.gov (United States)

Chen, Shanshan; Takata, Tsuyoshi; Domen, Kazunari

2017-10-01

The conversion of solar energy to chemical energy is a promising way of generating renewable energy. Hydrogen production by means of water splitting over semiconductor photocatalysts is a simple, cost-effective approach to large-scale solar hydrogen synthesis. Since the discovery of the Honda-Fujishima effect, considerable progress has been made in this field, and numerous photocatalytic materials and water-splitting systems have been developed. In this Review, we summarize existing water-splitting systems based on particulate photocatalysts, focusing on the main components: light-harvesting semiconductors and co-catalysts. The essential design principles of the materials employed for overall water-splitting systems based on one-step and two-step photoexcitation are also discussed, concentrating on three elementary processes: photoabsorption, charge transfer and surface catalytic reactions. Finally, we outline challenges and potential advances associated with solar water splitting by particulate photocatalysts for future commercial applications.

Thermoeconomic analysis of a copper-chlorine thermochemical cycle for nuclear-based hydrogen production

International Nuclear Information System (INIS)

Orhan, Mehmet F.; Dincer, Ibrahim; Rosen, Marc A.

2010-01-01

Thermochemical water splitting with a copper-chlorine (Cu-Cl) cycle is a promising process that could be linked with nuclear reactors to decompose water into its constituents, oxygen and hydrogen, through intermediate copper and chlorine compounds. In this paper, a comprehensive exergoeconomic analysis of the Cu-Cl cycle is reported to evaluate the production costs as a function of the amount and quality of the energy used for hydrogen production, as well as the costs of the exergy losses and the exergoeconomic improvement potential of the equipment used in the process. An additional objective is to determine changes in the design parameters of the Cu-Cl cycle that improve the cost effectiveness of the overall system. (orig.)

Guidelines to Develop Efficient Photocatalysts for Water Splitting

KAUST Repository

Garcia Esparza, Angel T.

2016-01-01

Photocatalytic overall water splitting is the only viable solar-to-fuel conversion technology. The research discloses an investigation process wherein by dissecting the photocatalytic water splitting device, electrocatalysts, and semiconductor

Bibliographic Review about Solar Hydrogen Production Through Thermochemical Cycles

International Nuclear Information System (INIS)

Fernandez Saavedra, R.

2007-01-01

This report presents a summary of the different thermical processes used to obtain hydrogen through solar energy, paying more attention to the production of hydrogen from water through thermochemical cycles. In this aspect, it is briefly described the most interesting thermochemical cycles, focusing on thermochemical cycles based on oxides. (Author) 25 refs

Communication: The electronic entropy of charged defect formation and its impact on thermochemical redox cycles

Science.gov (United States)

Lany, Stephan

2018-02-01

The ideal material for solar thermochemical water splitting, which has yet to be discovered, must satisfy stringent conditions for the free energy of reduction, including, in particular, a sufficiently large positive contribution from the solid-state entropy. By inverting the commonly used relationship between defect formation energy and defect concentration, it is shown here that charged defect formation causes a large electronic entropy contribution manifesting itself as the temperature dependence of the Fermi level. This result is a general feature of charged defect formation and motivates new materials design principles for solar thermochemical hydrogen production.

JAEA’s R&D on the Thermochemical Hydrogen Production IS Process

International Nuclear Information System (INIS)

Kasahara, Seiji; Tanaka, Nobuyuki; Noguchi, Hiroki; Iwatsuki, Jin; Takegami, Hiroaki; Yan, Xing L.; Kubo, Shinji

2014-01-01

Japan Atomic Energy Agency (JAEA) has studied iodine-sulfur (IS) process, a thermochemical cycle to produce hydrogen by water splitting. This process is a candidate application of high temperature heat from high temperature gas-cooled reactors. This paper outlines the IS process study in JAEA, in particular recent situation of the R&D. Reactor components and a total process facility are tested to evaluate their integrity. A Bunsen reactor, a H_2SO_4 decomposer and a HI decomposer made of industrial materials such as SiC ceramic, fluoroplastic and lining materials have been examined separately as reactor components. A semibatch test and a thermal cycle test were operated in the Bunsen reactor. H_2SO_4 decomposition test is in a bayonet type reactor and HI decomposition test in an adiabatic radial flow type reactor are now under way. On the basis of a demonstration of continuous hydrogen production of 31 NL/h by a glass apparatus, an experimental apparatus of the total IS process has just been constructed to verify integrity of process components of industrial materials, H_2 production scale of which is 200 NL/h. Electro-electrodialysis (EED) cells to concentrate HI before distillation and a SiC-made bayonet type H_2SO_4 decomposer are applied in the facility. Process data of EED cells has been collected aiming to improve H_2 production thermal efficiency. Influence of temperature, composition in solution and existence of impurities on the cell properties has been investigated. Reduction of heat input to a HI separation step by applying the results of the study was shown. (author)

Comprehensive characterisation of sewage sludge for thermochemical conversion processes - Based on Singapore survey.

Science.gov (United States)

Chan, Wei Ping; Wang, Jing-Yuan

2016-08-01

Recently, sludge attracted great interest as a potential feedstock in thermochemical conversion processes. However, compositions and thermal degradation behaviours of sludge were highly complex and distinctive compared to other traditional feedstock led to a need of fundamental research on sludge. Comprehensive characterisation of sludge specifically for thermochemical conversion was carried out for all existing Water Reclamation Plants in Singapore. In total, 14 sludge samples collected based on the type, plant, and batch categorisation. Existing characterisation methods for physical and chemical properties were analysed and reviewed using the collected samples. Qualitative similarities and quantitative variations of different sludge samples were identified and discussed. Oxidation of inorganic in sludge during ash forming analysis found to be causing significant deviations on proximate and ultimate analysis. Therefore, alternative parameters and comparison basis including Fixed Residues (FR), Inorganic Matters (IM) and Total Inorganics (TI) were proposed for better understanding on the thermochemical characteristics of sludge. Copyright © 2016 Elsevier Ltd. All rights reserved.

Thermochemical equilibrium modelling of a gasifying process

International Nuclear Information System (INIS)

Melgar, Andres; Perez, Juan F.; Laget, Hannes; Horillo, Alfonso

2007-01-01

This article discusses a mathematical model for the thermochemical processes in a downdraft biomass gasifier. The model combines the chemical equilibrium and the thermodynamic equilibrium of the global reaction, predicting the final composition of the producer gas as well as its reaction temperature. Once the composition of the producer gas is obtained, a range of parameters can be derived, such as the cold gas efficiency of the gasifier, the amount of dissociated water in the process and the heating value and engine fuel quality of the gas. The model has been validated experimentally. This work includes a parametric study of the influence of the gasifying relative fuel/air ratio and the moisture content of the biomass on the characteristics of the process and the producer gas composition. The model helps to predict the behaviour of different biomass types and is a useful tool for optimizing the design and operation of downdraft biomass gasifiers

Solar Thermochemical Hydrogen Production via Terbium Oxide Based Redox Reactions

Directory of Open Access Journals (Sweden)

Rahul Bhosale

2016-01-01

Full Text Available The computational thermodynamic modeling of the terbium oxide based two-step solar thermochemical water splitting (Tb-WS cycle is reported. The 1st step of the Tb-WS cycle involves thermal reduction of TbO2 into Tb and O2, whereas the 2nd step corresponds to the production of H2 through Tb oxidation by water splitting reaction. Equilibrium compositions associated with the thermal reduction and water splitting steps were determined via HSC simulations. Influence of oxygen partial pressure in the inert gas on thermal reduction of TbO2 and effect of water splitting temperature (TL on Gibbs free energy related to the H2 production step were examined in detail. The cycle (ηcycle and solar-to-fuel energy conversion (ηsolar-to-fuel efficiency of the Tb-WS cycle were determined by performing the second-law thermodynamic analysis. Results obtained indicate that ηcycle and ηsolar-to-fuel increase with the decrease in oxygen partial pressure in the inert flushing gas and thermal reduction temperature (TH. It was also realized that the recuperation of the heat released by the water splitting reactor and quench unit further enhances the solar reactor efficiency. At TH=2280 K, by applying 60% heat recuperation, maximum ηcycle of 39.0% and ηsolar-to-fuel of 47.1% for the Tb-WS cycle can be attained.

An overview of renewable hydrogen production from thermochemical process of oil palm solid waste in Malaysia

International Nuclear Information System (INIS)

Hosseini, Seyed Ehsan; Wahid, Mazlan Abdul; Ganjehkaviri, A.

2015-01-01

Highlights: • 40% of energy demand of Malaysia could be supplied by thermochemical process of PSR. • SCWG of PSR is preferable thermochemical process due to char and tar elimination. • Potential of H 2 production from SCWG of PSR is 1.05 × 10 10 kgH 2 per year in Malaysia. • Highly moisturized PSR could be used in hydrogen production by SCWG process. - Abstract: Hydrogen is one of the most promising energy carriers for the future of the world due to its tremendous capability of pollution reduction. Hydrogen utilization is free of toxic gases formation as well as carbon dioxide (CO 2 ) emission. Hydrogen production can be implemented using a wide variety of resources including fossil fuels, nuclear energy and renewable and sustainable energy (RSE). Amongst various RSE resources, biomass has great capacity to be employed for renewable hydrogen production. Hydrogen production from palm solid residue (PSR) via thermochemical process is a perfect candidate for waste-to-well strategy in palm oil mills in Malaysia. In this paper, various characteristics of hydrogen production from thermochemical process of PSR includes pyrolysis and gasification are reviewed. The annual oil palm fruits production in Malaysia is approximately 100 million tonnes which the solid waste of the fruits is capable to generate around 1.05 × 10 10 kgH 2 (1.26 EJ) via supercritical water gasification (SCWG) process. The ratio of energy output to energy input of SCWG process of PSR is about 6.56 which demonstrates the priority of SCWG to transform the energy of PSR into a high energy end product. The high moisture of PSR which is the most important barrier for its direct combustion, emerges as an advantage in thermochemical reactions and highly moisturized PSR (even more than 50%) is utilized directly in SCWG without application of any high cost drying process. Implementation of appropriate strategies could lead Malaysia to supply about 40% of its annual energy demand by hydrogen yield from

Photocatalytic Water-Splitting Reaction from Catalytic and Kinetic Perspectives

KAUST Repository

Hisatomi, Takashi

2014-10-16

Abstract: Some particulate semiconductors loaded with nanoparticulate catalysts exhibit photocatalytic activity for the water-splitting reaction. The photocatalysis is distinct from the thermal catalysis because photocatalysis involves photophysical processes in particulate semiconductors. This review article presents a brief introduction to photocatalysis, followed by kinetic aspects of the photocatalytic water-splitting reaction.Graphical Abstract: [Figure not available: see fulltext.

Water Footprint and Land Requirement of Solar Thermochemical Jet-Fuel Production.

Science.gov (United States)

Falter, Christoph; Pitz-Paal, Robert

2017-11-07

The production of alternative fuels via the solar thermochemical pathway has the potential to provide supply security and to significantly reduce greenhouse gas emissions. H 2 O and CO 2 are converted to liquid hydrocarbon fuels using concentrated solar energy mediated by redox reactions of a metal oxide. Because attractive production locations are in arid regions, the water footprint and the land requirement of this fuel production pathway are analyzed. The water footprint consists of 7.4 liters per liter of jet fuel of direct demand on-site and 42.4 liters per liter of jet fuel of indirect demand, where the dominant contributions are the mining of the rare earth oxide ceria, the manufacturing of the solar concentration infrastructure, and the cleaning of the mirrors. The area-specific productivity is found to be 33 362 liters per hectare per year of jet fuel equivalents, where the land coverage is mainly due to the concentration of solar energy for heat and electricity. The water footprint and the land requirement of the solar thermochemical fuel pathway are larger than the best power-to-liquid pathways but an order of magnitude lower than the best biomass-to-liquid pathways. For the production of solar thermochemical fuels arid regions are best-suited, and for biofuels regions of a moderate and humid climate.

Tantalum nitride for photocatalytic water splitting: concept and applications

KAUST Repository

Nurlaela, Ela

2016-10-12

Along with many other solar energy conversion processes, research on photocatalytic water splitting to generate hydrogen and oxygen has experienced rapid major development over the past years. Developing an efficient visible-light-responsive photocatalyst has been one of the targets of such research efforts. In this regard, nitride materials, particularly Ta3N5, have been the subject of investigation due to their promising properties. This review focuses on the fundamental parameters involved in the photocatalytic processes targeting overall water splitting using Ta3N5 as a model photocatalyst. The discussion primarily focuses on relevant parameters that are involved in photon absorption, exciton separation, carrier diffusion, carrier transport, catalytic efficiency, and mass transfer of the reactants. An overview of collaborative experimental and theoretical approaches to achieve efficient photocatalytic water splitting using Ta3N5 is discussed.

Tantalum nitride for photocatalytic water splitting: concept and applications

KAUST Repository

Nurlaela, Ela; Ziani, Ahmed; Takanabe, Kazuhiro

2016-01-01

Along with many other solar energy conversion processes, research on photocatalytic water splitting to generate hydrogen and oxygen has experienced rapid major development over the past years. Developing an efficient visible-light-responsive photocatalyst has been one of the targets of such research efforts. In this regard, nitride materials, particularly Ta3N5, have been the subject of investigation due to their promising properties. This review focuses on the fundamental parameters involved in the photocatalytic processes targeting overall water splitting using Ta3N5 as a model photocatalyst. The discussion primarily focuses on relevant parameters that are involved in photon absorption, exciton separation, carrier diffusion, carrier transport, catalytic efficiency, and mass transfer of the reactants. An overview of collaborative experimental and theoretical approaches to achieve efficient photocatalytic water splitting using Ta3N5 is discussed.

Guidelines to Develop Efficient Photocatalysts for Water Splitting

KAUST Repository

Garcia Esparza, Angel T.

2016-04-03

Photocatalytic overall water splitting is the only viable solar-to-fuel conversion technology. The research discloses an investigation process wherein by dissecting the photocatalytic water splitting device, electrocatalysts, and semiconductor photocatalysts can be independently studied, developed and optimized. The assumption of perfect catalysts leads to the realization that semiconductors are the limiting factor in photocatalysis. This dissertation presents a guideline for efficient photocatalysis using semiconductor particles developed from idealized theoretical simulations. No perfect catalysts exist; then the discussion focus on the development of efficient non-noble metal electrocatalysts for hydrogen evolution from water reduction. Tungsten carbide (WC) is selective for the catalysis of hydrogen without the introduction of the reverse reaction of water formation, which is critical to achieving photocatalytic overall water splitting as demonstrated in this work. Finally, photoelectrochemistry is used to characterize thoroughly Cu-based p-type semiconductors with potential for large-scale manufacture. Artificial photosynthesis may be achieved by following the recommendations herein presented.

Method for thermochemical decomposition of water

Science.gov (United States)

Abraham, Bernard M.; Schreiner, Felix

1977-01-11

Water is thermochemically decomposed to produce hydrogen by the following sequence of reactions: KI, NH.sub.3, CO.sub. 2 and water in an organic solvent such as ethyl or propyl alcohol are reacted to produce KHCO 3 and NH.sub.4 I. The KHCO.sub.3 is thermally decomposed to K.sub.2 CO.sub.3, H.sub.2 O and CO.sub.2, while the NH.sub.4 I is reacted with Hg to produce HgI.sub.2, NH.sub.3 and H.sub.2. The K.sub.2 CO.sub.3 obtained by calcining KHCO.sub.3 is then reacted with HgI.sub.2 to produce Hg, KI, CO and O.sub.2. All products of the reaction are recycled except hydrogen and oxygen.

Hybrid bio-photo-electro-chemical cells for solar water splitting

OpenAIRE

Pinhassi, Roy I.; Kallmann, Dan; Saper, Gadiel; Dotan, Hen; Linkov, Artyom; Kay, Asaf; Liveanu, Varda; Schuster, Gadi; Adir, Noam; Rothschild, Avner

2016-01-01

Photoelectrochemical water splitting uses solar power to decompose water to hydrogen and oxygen. Here we show how the photocatalytic activity of thylakoid membranes leads to overall water splitting in a bio-photo-electro-chemical (BPEC) cell via a simple process. Thylakoids extracted from spinach are introduced into a BPEC cell containing buffer solution with ferricyanide. Upon solar-simulated illumination, water oxidation takes place and electrons are shuttled by the ferri/ferrocyanide redox...

Advanced Electrochemical Technologies for Hydrogen Production by Alternative Thermochemical Cycles

Energy Technology Data Exchange (ETDEWEB)

Lvov, Serguei; Chung, Mike; Fedkin, Mark; Lewis, Michele; Balashov, Victor; Chalkova, Elena; Akinfiev, Nikolay; Stork, Carol; Davis, Thomas; Gadala-Maria, Francis; Stanford, Thomas; Weidner, John; Law, Victor; Prindle, John

2011-01-06

Hydrogen fuel is a potentially major solution to the problem of climate change, as well as addressing urban air pollution issues. But a key future challenge for hydrogen as a clean energy carrier is a sustainable, low-cost method of producing it in large capacities. Most of the world's hydrogen is currently derived from fossil fuels through some type of reforming processes. Nuclear hydrogen production is an emerging and promising alternative to the reforming processes for carbon-free hydrogen production in the future. This report presents the main results of a research program carried out by a NERI Consortium, which consisted of Penn State University (PSU) (lead), University of South Carolina (USC), Tulane University (TU), and Argonne National Laboratory (ANL). Thermochemical water decomposition is an emerging technology for large-scale production of hydrogen. Typically using two or more intermediate compounds, a sequence of chemical and physical processes split water into hydrogen and oxygen, without releasing any pollutants externally to the atmosphere. These intermediate compounds are recycled internally within a closed loop. While previous studies have identified over 200 possible thermochemical cycles, only a few have progressed beyond theoretical calculations to working experimental demonstrations that establish scientific and practical feasibility of the thermochemical processes. The Cu-Cl cycle has a significant advantage over other cycles due to lower temperature requirements – around 530 °C and below. As a result, it can be eventually linked with the Generation IV thermal power stations. Advantages of the Cu-Cl cycle over others include lower operating temperatures, ability to utilize low-grade waste heat to improve energy efficiency, and potentially lower cost materials. Another significant advantage is a relatively low voltage required for the electrochemical step (thus low electricity input). Other advantages include common chemical agents and

The NREL Biochemical and Thermochemical Ethanol Conversion Processes: Financial and Environmental Analysis Comparison

Directory of Open Access Journals (Sweden)

Jesse Sky Daystar

2015-07-01

Full Text Available The financial and environmental performance of the National Renewable Energy Lab’s (NREL thermochemical and biochemical biofuel conversion processes are examined herein with pine, eucalyptus, unmanaged hardwood, switchgrass, and sweet sorghum. The environmental impacts of the process scenarios were determined by quantifying greenhouse gas (GHG emissions and TRACI impacts. Integrated financial and environmental performance metrics were introduced and used to examine the biofuel production scenarios. The thermochemical and biochemical conversion processes produced the highest financial performance and lowest environmental impacts when paired with pine and sweet sorghum, respectively. The high ash content of switchgrass and high lignin content of loblolly pine lowered conversion yields, resulting in the highest environmental impacts and lowest financial performance for the thermochemical and biochemical conversion processes, respectively. Biofuel produced using the thermochemical conversion process resulted in lower TRACI single score impacts and somewhat lower GHG emissions per megajoule (MJ of fuel than using the biochemical conversion pathway. The cost of carbon mitigation resulting from biofuel production and corresponding government subsidies was determined to be higher than the expected market carbon price. In some scenarios, the cost of carbon mitigation was several times higher than the market carbon price, indicating that there may be other more cost-effective methods of reducing carbon emissions.

Developing new understanding of photoelectrochemical water splitting via in-situ techniques: A review on recent progress

Directory of Open Access Journals (Sweden)

Jiajie Cen

2017-04-01

Full Text Available Photoelectrochemical (PEC water splitting is a promising technology for solar hydrogen production to build a sustainable, renewable and clean energy economy. Given the complexity of the PEC water splitting processes, it is important to note that developing in-situ techniques for studying PEC water splitting presents a formidable challenge. This review is aimed at highlighting advantages and disadvantages of each technique, while offering a pathway of potentially combining several techniques to address different aspects of interfacial processes in PEC water splitting. We reviewed recent progress in various techniques and approaches utilized to study PEC water splitting, focusing on spectroscopic and scanning-probe methods. Keywords: In-situ, Water splitting, IMPS, TAS, SPM

Remarks on the thermochemical production of hydrogen from water using heat from the high temperature reactor

International Nuclear Information System (INIS)

Barnert, H.

1980-06-01

In this report, some aspects of the production of hydrogen from water using heat from the High Temperature Reactor has been studied. These aspects are: the theoretical potential for economic competitivness, the application of hydrogen in the Heat Market, the size of the market potential in the Federal Republic of Germany and the extent of research and development work. In addition another novel proposal for a thermochemical cycle has been studied. For the description of the theoretical potential for economic competitivness, a definition of the 'coupling', has been introduced, which is thermodynamicaly developed; the thermochemical cycle is compared with the thermochemical cycle. Using the coupling, it becomes possible to describe a relation between thermodynamical parameters and the ecomomical basic data of capital costs. Reasons are given from the theoretical point of view for the application of hydrogen as an energy carrier of high exergetic value in the heat market. The discussion of energy problems as 'questions of global survival' leads here to a proposal for the introduction of the term 'extropy'. The market potential in the Federal Republic of Germany is estimated. A further novel proposal for a thermochemical cycle is the 'hydrocarbon-hybrid-process'. The extent of research and development work is explained. (orig.) [de

Energy and exergy analyses of a copper-chlorine thermochemical water decomposition pilot plant for hydrogen production

International Nuclear Information System (INIS)

Orhan, M.F.; Dincer, I.; Rosen, M.A.

2008-01-01

Nuclear-based hydrogen production via thermochemical water decomposition using a copper-chlorine (Cu-Cl) cycle consists of a series of chemical reactions in which water is split into hydrogen and oxygen as the net result. This is accomplished through reactions involving intermediate copper and chlorine compounds, which are recycled. Energy and exergy analyses are reported here of a Cu-Cl pilot plant, including the relevant chemical reactions. The reference environment is taken to be at a temperature of 298.15 K and atmospheric pressure (1 atm). The chemical exergy of a substance, which is the maximum work that can be obtained from it by taking it to chemical equilibrium with the reference environment at constant temperature and pressure, is calculated with property data for the substance and the reference environment, with enthalpy and entropy values calculated using Shomate equations. The reaction heat, exergy destruction and efficiencies in each chemical reaction vary with the reaction temperature and reference-environment temperature. A parametric study with variable reaction and reference-environment temperatures is also presented. (author)

CFD Studies on Biomass Thermochemical Conversion

Directory of Open Access Journals (Sweden)

Lifeng Yan

2008-06-01

Full Text Available Thermochemical conversion of biomass offers an efficient and economically process to provide gaseous, liquid and solid fuels and prepare chemicals derived from biomass. Computational fluid dynamic (CFD modeling applications on biomass thermochemical processes help to optimize the design and operation of thermochemical reactors. Recent progression in numerical techniques and computing efficacy has advanced CFD as a widely used approach to provide efficient design solutions in industry. This paper introduces the fundamentals involved in developing a CFD solution. Mathematical equations governing the fluid flow, heat and mass transfer and chemical reactions in thermochemical systems are described and sub-models for individual processes are presented. It provides a review of various applications of CFD in the biomass thermochemical process field.

IS process for thermochemical hydrogen production

International Nuclear Information System (INIS)

Onuki, Kaoru; Nakajima, Hayato; Ioka, Ikuo; Futakawa, Masatoshi; Shimizu, Saburo

1994-11-01

The state-of-the-art of thermochemical hydrogen production by IS process is reviewed including experimental data obtained at JAERI on the chemistry of the Bunsen reaction step and on the corrosion resistance of the structural materials. The present status of laboratory scale demonstration at JAERI is also included. The study on the chemistry of the chemical reactions and the products separations has identified feasible methods to function the process. The flowsheeting studies revealed a process thermal efficiency higher than 40% is achievable under efficient process conditions. The corrosion resistance of commercially available structural materials have been clarified under various process conditions. The basic scheme of the process has been realized in a laboratory scale apparatus. R and D requirements to proceed to the engineering demonstration coupled with HTTR are briefly discussed. (author)

2-Photon tandem device for water splitting

DEFF Research Database (Denmark)

Seger, Brian; Castelli, Ivano Eligio; Vesborg, Peter Christian Kjærgaard

2014-01-01

Within the field Of photocatalytic water splitting there are several strategies to achieve the goal of efficient and cheap photocatalytic water splitting. This work examines one particular strategy by focusing on monolithically stacked, two-photon photoelectrochemical cells. The overall aim...... for photocatalytic water splitting by using a large bandgap photocathode and a low bandgap photoanode with attached protection layers....

Process development for elemental recovery from PGM tailings by thermochemical treatment: Preliminary major element extraction studies using ammonium sulphate as extracting agent.

Science.gov (United States)

Mohamed, Sameera; van der Merwe, Elizabet M; Altermann, Wladyslaw; Doucet, Frédéric J

2016-04-01

Mine tailings can represent untapped secondary resources of non-ferrous, ferrous, precious, rare and trace metals. Continuous research is conducted to identify opportunities for the utilisation of these materials. This preliminary study investigated the possibility of extracting major elements from South African tailings associated with the mining of Platinum Group Metals (PGM) at the Two Rivers mine operations. These PGM tailings typically contain four major elements (11% Al2O3; 12% MgO; 22% Fe2O3; 34% Cr2O3), with lesser amounts of SiO2 (18%) and CaO (2%). Extraction was achieved via thermochemical treatment followed by aqueous dissolution, as an alternative to conventional hydrometallurgical processes. The thermochemical treatment step used ammonium sulphate, a widely available, low-cost, recyclable chemical agent. Quantification of the efficiency of the thermochemical process required the development and optimisation of the dissolution technique. Dissolution in water promoted the formation of secondary iron precipitates, which could be prevented by leaching thermochemically-treated tailings in 0.6M HNO3 solution. The best extraction efficiencies were achieved for aluminium (ca. 60%) and calcium (ca. 80%). 35% iron and 32% silicon were also extracted, alongside chromium (27%) and magnesium (25%). Thermochemical treatment using ammonium sulphate may therefore represent a promising technology for extracting valuable elements from PGM tailings, which could be subsequently converted to value-added products. However, it is not element-selective, and major elements were found to compete with the reagent to form water-soluble sulphate-metal species. Further development of this integrated process, which aims at achieving the full potential of utilisation of PGM tailings, is currently underway. Copyright © 2016 Elsevier Ltd. All rights reserved.

Global warming potential of the sulfur-iodine process using life cycle assessment methodology

International Nuclear Information System (INIS)

Lattin, William C.; Utgikar, Vivek P.

2009-01-01

A life cycle assessment (LCA) of one proposed method of hydrogen production - thermochemical water-splitting using the sulfur-iodine cycle couple with a very high-temperature nuclear reactor - is presented in this paper. Thermochemical water-splitting theoretically offers a higher overall efficiency than high-temperature electrolysis of water because heat from the nuclear reactor is provided directly to the hydrogen generation process, instead of using the intermediate step of generating electricity. The primary heat source for the S-I cycle is an advanced nuclear reactor operating at temperatures corresponding to those required by the sulfur-iodine process. This LCA examines the environmental impact of the combined advanced nuclear and hydrogen generation plants and focuses on quantifying the emissions of carbon dioxide per kilogram of hydrogen produced. The results are presented in terms of global warming potential (GWP). The GWP of the system is 2500 g carbon dioxide-equivalent (CO 2 -eq) per kilogram of hydrogen produced. The GWP of this process is approximately one-sixth of that for hydrogen production by steam reforming of natural gas, and is comparable to producing hydrogen from wind- or hydro-electric conventional electrolysis. (author)

Experimental investigation of molten salt droplet quenching and solidification processes of heat recovery in thermochemical hydrogen production

International Nuclear Information System (INIS)

Ghandehariun, S.; Wang, Z.; Naterer, G.F.; Rosen, M.A.

2015-01-01

Highlights: • Thermal efficiency of a thermochemical cycle of hydrogen production is improved. • Direct contact heat recovery from molten salt is analyzed. • Falling droplets quenched into water are investigated experimentally. - Abstract: This paper investigates the heat transfer and X-ray diffraction patterns of solidified molten salt droplets in heat recovery processes of a thermochemical Cu–Cl cycle of hydrogen production. It is essential to recover the heat of the molten salt to enhance the overall thermal efficiency of the copper–chlorine cycle. A major portion of heat recovery within the cycle can be achieved by cooling and solidifying the molten salt exiting an oxygen reactor. Heat recovery from the molten salt is achieved by dispersing the molten stream into droplets. In this paper, an analytical study and experimental investigation of the thermal phenomena of a falling droplet quenched into water is presented, involving the droplet surface temperature during descent and resulting composition change in the quench process. The results show that it is feasible to quench the molten salt droplets for an efficient heat recovery process without introducing any material imbalance for the overall cycle integration.

Potential for thermochemical conversion of biomass residues from the integrated sugar-ethanol process - Fate of ash and ash-forming elements.

Science.gov (United States)

Dirbeba, Meheretu Jaleta; Brink, Anders; DeMartini, Nikolai; Zevenhoven, Maria; Hupa, Mikko

2017-06-01

In this work, potential for thermochemical conversion of biomass residues from an integrated sugar-ethanol process and the fate of ash and ash-forming elements in the process are presented. Ash, ash-forming elements, and energy flows in the process were determined using mass balances and analyses of eight different biomass samples for ash contents, elemental compositions, and heating values. The results show that the ash content increases from the sugarcane to the final residue, vinasse. The cane straw, which is left in the field, contains one-third of the energy and 25% of the K and Cl while the vinasse contains 2% of the energy and 40% of the K and Cl in the cane. K and Cl in biomass fuels cause corrosion and fouling problems in boilers and gasifiers. Over 85% of these elements in the straw are water soluble indicating that water leaching would improve it for utilization in thermochemical conversion. Copyright © 2017 Elsevier Ltd. All rights reserved.

Solar thermochemical processing system and method

Science.gov (United States)

Wegeng, Robert S.; Humble, Paul H.; Krishnan, Shankar; Leith, Steven D.; Palo, Daniel R.; Dagle, Robert A.

2018-04-24

A solar thermochemical processing system is disclosed. The system includes a first unit operation for receiving concentrated solar energy. Heat from the solar energy is used to drive the first unit operation. The first unit operation also receives a first set of reactants and produces a first set of products. A second unit operation receives the first set of products from the first unit operation and produces a second set of products. A third unit operation receives heat from the second unit operation to produce a portion of the first set of reactants.

Recent Progress in Energy-Driven Water Splitting.

Science.gov (United States)

Tee, Si Yin; Win, Khin Yin; Teo, Wee Siang; Koh, Leng-Duei; Liu, Shuhua; Teng, Choon Peng; Han, Ming-Yong

2017-05-01

Hydrogen is readily obtained from renewable and non-renewable resources via water splitting by using thermal, electrical, photonic and biochemical energy. The major hydrogen production is generated from thermal energy through steam reforming/gasification of fossil fuel. As the commonly used non-renewable resources will be depleted in the long run, there is great demand to utilize renewable energy resources for hydrogen production. Most of the renewable resources may be used to produce electricity for driving water splitting while challenges remain to improve cost-effectiveness. As the most abundant energy resource, the direct conversion of solar energy to hydrogen is considered the most sustainable energy production method without causing pollutions to the environment. In overall, this review briefly summarizes thermolytic, electrolytic, photolytic and biolytic water splitting. It highlights photonic and electrical driven water splitting together with photovoltaic-integrated solar-driven water electrolysis.

Bimetallic catalysts for HI decomposition in the iodine-sulfur thermochemical cycle

International Nuclear Information System (INIS)

Wang Laijun; Hu Songzhi; Xu Lufei; Li Daocai; Han Qi; Chen Songzhe; Zhang Ping; Xu Jingming

2014-01-01

Among the different kinds of thermochemical water-splitting cycles, the iodine-sulfur (IS) cycle has attracted more and more interest because it is one of the promising candidates for economical and massive hydrogen production. However, there still exist some science and technical problems to be solved before industrialization of the IS process. One such problem is the catalytic decomposition of hydrogen iodide. Although the active carbon supported platinum has been verified to present the excellent performance for HI decomposition, it is very expensive and easy to agglomerate under the harsh condition. In order to decrease the cost and increase the stability of the catalysts for HI decomposition, a series of bimetallic catalysts were prepared and studied at INET. This paper summarized our present research advances on the bimetallic catalysts (Pt-Pd, Pd-Ir and Pt-Ir) for HI decomposition. In the course of the study, the physical properties, structure, and morphology of the catalysts were characterized by specific surface area, X-ray diffractometer; and transmission electron microscopy, respectively. The catalytic activity for HI decomposition was investigated in a fixed bed reactor under atmospheric pressure. The results show that due to the higher activity and better stability, the active carbon supported bimetallic catalyst is more potential candidate than mono metallic Pt catalyst for HI decomposition in the IS thermochemical cycle. (author)

Thermochemical hydrogen generation of indium oxide thin films

Directory of Open Access Journals (Sweden)

Taekyung Lim

2017-03-01

Full Text Available Development of alternative energy resources is an urgent requirement to alleviate current energy constraints. As such, hydrogen gas is gaining attention as a future alternative energy source to address existing issues related to limited energy resources and air pollution. In this study, hydrogen generation by a thermochemical water-splitting process using two types of In2O3 thin films was investigated. The two In2O3 thin films prepared by chemical vapor deposition (CVD and sputtering deposition systems contained different numbers of oxygen vacancies, which were directly related to hydrogen generation. The as-grown In2O3 thin film prepared by CVD generated a large amount of hydrogen because of its abundant oxygen vacancies, while that prepared by sputtering had few oxygen vacancies, resulting in low hydrogen generation. Increasing the temperature of the In2O3 thin film in the reaction chamber caused an increase in hydrogen generation. The oxygen-vacancy-rich In2O3 thin film is expected to provide a highly effective production of hydrogen as a sustainable and efficient energy source.

Hybrid bio-photo-electro-chemical cells for solar water splitting.

Science.gov (United States)

Pinhassi, Roy I; Kallmann, Dan; Saper, Gadiel; Dotan, Hen; Linkov, Artyom; Kay, Asaf; Liveanu, Varda; Schuster, Gadi; Adir, Noam; Rothschild, Avner

2016-08-23

Photoelectrochemical water splitting uses solar power to decompose water to hydrogen and oxygen. Here we show how the photocatalytic activity of thylakoid membranes leads to overall water splitting in a bio-photo-electro-chemical (BPEC) cell via a simple process. Thylakoids extracted from spinach are introduced into a BPEC cell containing buffer solution with ferricyanide. Upon solar-simulated illumination, water oxidation takes place and electrons are shuttled by the ferri/ferrocyanide redox couple from the thylakoids to a transparent electrode serving as the anode, yielding a photocurrent density of 0.5 mA cm(-2). Hydrogen evolution occurs at the cathode at a bias as low as 0.8 V. A tandem cell comprising the BPEC cell and a Si photovoltaic module achieves overall water splitting with solar to hydrogen efficiency of 0.3%. These results demonstrate the promise of combining natural photosynthetic membranes and man-made photovoltaic cells in order to convert solar power into hydrogen fuel.

Thermochemical surface engineering of steels

DEFF Research Database (Denmark)

Thermochemical Surface Engineering of Steels provides a comprehensive scientific overview of the principles and different techniques involved in thermochemical surface engineering, including thermodynamics, kinetics principles, process technologies and techniques for enhanced performance of steels...

Nanoscale strontium titanate photocatalysts for overall water splitting.

Science.gov (United States)

Townsend, Troy K; Browning, Nigel D; Osterloh, Frank E

2012-08-28

SrTiO(3) (STO) is a large band gap (3.2 eV) semiconductor that catalyzes the overall water splitting reaction under UV light irradiation in the presence of a NiO cocatalyst. As we show here, the reactivity persists in nanoscale particles of the material, although the process is less effective at the nanoscale. To reach these conclusions, Bulk STO, 30 ± 5 nm STO, and 6.5 ± 1 nm STO were synthesized by three different methods, their crystal structures verified with XRD and their morphology observed with HRTEM before and after NiO deposition. In connection with NiO, all samples split water into stoichiometric mixtures of H(2) and O(2), but the activity is decreasing from 28 μmol H(2) g(-1) h(-1) (bulk STO), to 19.4 μmol H(2) g(-1) h(-1) (30 nm STO), and 3.0 μmol H(2) g(-1) h(-1) (6.5 nm STO). The reasons for this decrease are an increase of the water oxidation overpotential for the smaller particles and reduced light absorption due to a quantum size effect. Overall, these findings establish the first nanoscale titanate photocatalyst for overall water splitting.

Ultrasonic splitting of oil-in-water emulsions

DEFF Research Database (Denmark)

Hald, Jens; König, Ralf; Benes, Ewald

1999-01-01

Standing resonant ultrasonic wave fields can be utilized for liquid–liquid separation of the dispersed particles and the fluid caused by the acoustic radiation pressure and the induced particle agglomeration or coagulation/coalescence process. For the splitting of oil-in-water emulsions, the avai......Standing resonant ultrasonic wave fields can be utilized for liquid–liquid separation of the dispersed particles and the fluid caused by the acoustic radiation pressure and the induced particle agglomeration or coagulation/coalescence process. For the splitting of oil-in-water emulsions......, the available piezoelectric composite transducer technology was improved and a dedicated resonator with crossed plane wave sonication geometry has been developed. The resonator chamber is entirely made of aluminium or tempax glass and the PZT piezoceramic transducer delivers an acoustic energy flow density...... of up to 24 W/cm2 into the sonication volume. The chosen resonance frequency is kept stable by automatic frequency control utilizing the maximum true power criterion. Physically and chemically well-defined low and high density pure laboratory and also industrially used cooling-lubricating oil...

Biomass Thermochemical Conversion Program: 1986 annual report

Energy Technology Data Exchange (ETDEWEB)

Schiefelbein, G.F.; Stevens, D.J.; Gerber, M.A.

1987-01-01

Wood and crop residues constitute a vast majority of the biomass feedstocks available for conversion, and thermochemical processes are well suited for conversion of these materials. Thermochemical conversion processes can generate a variety of products such as gasoline hydrocarbon fuels, natural gas substitutes, or heat energy for electric power generation. The US Department of Energy is sponsoring research on biomass conversion technologies through its Biomass Thermochemical Conversion Program. Pacific Northwest Laboratory has been designated the Technical Field Management Office for the Biomass Thermochemical Conversion Program with overall responsibility for the Program. This report briefly describes the Thermochemical Conversion Program structure and summarizes the activities and major accomplishments during fiscal year 1986. 88 refs., 31 figs., 5 tabs.

Recommended Ideal-Gas Thermochemical Functions for Heavy Water and its Substituent Isotopologues

Czech Academy of Sciences Publication Activity Database

Simkó, I.; Furtenbacher, T.; Hrubý, Jan; Zobov, N. F.; Polyansky, O. L.; Tennyson, J.; Gamache, R. R.; Szidarovszky, T.; Dénes, N.; Császár, A. G.

2017-01-01

Roč. 46, č. 2 (2017), č. článku 023104. ISSN 0047-2689 R&D Projects: GA ČR GA16-02647S Institutional support: RVO:61388998 Keywords : heavy water * ideal-gas thermochemical functions * partition function Subject RIV: BJ - Thermodynamics OBOR OECD: Thermodynamics Impact factor: 4.204, year: 2016

Lifecycle assessment of microalgae to biofuel: Comparison of thermochemical processing pathways

International Nuclear Information System (INIS)

Bennion, Edward P.; Ginosar, Daniel M.; Moses, John; Agblevor, Foster; Quinn, Jason C.

2015-01-01

Highlights: • Well to pump environmental assessment of two thermochemical processing pathways. • NER of 1.23 and GHG emissions of −11.4 g CO 2-eq (MJ) −1 for HTL pathway. • HTL represents promising conversion pathway based on use of wet biomass. • NER of 2.27 and GHG emissions of 210 g CO 2-eq (MJ) −1 for pyrolysis pathway. • Pyrolysis pathway: drying microalgae feedstock dominates environmental impact. - Abstract: Microalgae is being investigated as a renewable transportation fuel feedstock based on various advantages that include high annual yields, utilization of poor quality land, does not compete with food, and can be integrated with various waste streams. This study focuses on directly assessing the environmental impact of two different thermochemical conversion technologies for the microalgae-to-biofuel process through life cycle assessment. A system boundary of “well to pump” (WTP) is defined and includes sub-process models of the growth, dewatering, thermochemical bio-oil recovery, bio-oil stabilization, conversion to renewable diesel, and transport to the pump. Models were validated with experimental and literature data and are representative of an industrial-scale microalgae-to-biofuel process. Two different thermochemical bio-oil conversion systems are modeled and compared on a systems level, hydrothermal liquefaction (HTL) and pyrolysis. The environmental impact of the two pathways were quantified on the metrics of net energy ratio (NER), defined here as energy consumed over energy produced, and greenhouse gas (GHG) emissions. Results for WTP biofuel production through the HTL pathway were determined to be 1.23 for the NER and GHG emissions of −11.4 g CO 2-eq (MJ renewable diesel) −1 . Biofuel production through the pyrolysis pathway results in a NER of 2.27 and GHG emissions of 210 g CO 2-eq (MJ renewable diesel) −1 . The large environmental impact associated with the pyrolysis pathway is attributed to feedstock drying

A systematic multi-step screening of numerous salt hydrates for low temperature thermochemical energy storage

International Nuclear Information System (INIS)

N’Tsoukpoe, Kokouvi Edem; Schmidt, Thomas; Rammelberg, Holger Urs; Watts, Beatriz Amanda; Ruck, Wolfgang K.L.

2014-01-01

Highlights: • We report an evaluation of the potential of salt hydrates for thermochemical storage. • Both theoretical calculations and experimental measurements using TGA/DSC are used. • Salt hydrates offer very low potential for thermochemical heat storage. • The efficiency of classical processes using salt hydrates is very low: typically 25%. • New processes are needed for the use of salt hydrates in thermochemical heat storage. - Abstract: In this paper, the potential energy storage density and the storage efficiency of salt hydrates as thermochemical storage materials for the storage of heat generated by a micro-combined heat and power (micro-CHP) have been assessed. Because salt hydrates used in various thermochemical heat storage processes fail to meet the expectations, a systematic evaluation of the suitability of 125 salt hydrates has been performed in a three-step approach. In the first step general issues such as toxicity and risk of explosion have been considered. In the second and third steps, the authors implement a combined approach consisting of theoretical calculations and experimental measurements using Thermogravimetric Analysis (TGA). Thus, application-oriented comparison criteria, among which the net energy storage density of the material and the thermal efficiency, have been used to evaluate the potential of 45 preselected salt hydrates for a low temperature thermochemical heat storage application. For an application that requires a discharging temperature above 60 °C, SrBr 2 ·6H 2 O and LaCl 3 ·7H 2 O appear to be the most promising, only from thermodynamic point of view. However, the maximum net energy storage density including the water in the water storage tank that they offer (respectively 133 kW h m −3 and 89 kW h m −3 ) for a classical thermochemical heat storage process are not attractive for the intended application. Furthermore, the thermal efficiency that would result from the storage process based on salt hydrates

Hydrogen Production from Semiconductor-based Photocatalysis via Water Splitting

Directory of Open Access Journals (Sweden)

Jeffrey C. S. Wu

2012-10-01

Full Text Available Hydrogen is the ideal fuel for the future because it is clean, energy efficient, and abundant in nature. While various technologies can be used to generate hydrogen, only some of them can be considered environmentally friendly. Recently, solar hydrogen generated via photocatalytic water splitting has attracted tremendous attention and has been extensively studied because of its great potential for low-cost and clean hydrogen production. This paper gives a comprehensive review of the development of photocatalytic water splitting for generating hydrogen, particularly under visible-light irradiation. The topics covered include an introduction of hydrogen production technologies, a review of photocatalytic water splitting over titania and non-titania based photocatalysts, a discussion of the types of photocatalytic water-splitting approaches, and a conclusion for the current challenges and future prospects of photocatalytic water splitting. Based on the literatures reported here, the development of highly stable visible–light-active photocatalytic materials, and the design of efficient, low-cost photoreactor systems are the key for the advancement of solar-hydrogen production via photocatalytic water splitting in the future.

Development of a seasonal thermochemical storage system

NARCIS (Netherlands)

Cuypers, R.; Maraz, N.; Eversdijk, J.; Finck, C.J.; Henquet, E.M.P.; Oversloot, H.P.; Spijker, J.C. van 't; Geus, A.C. de

2012-01-01

In our laboratories, a seasonal thermochemical storage system for dwellings and offices is being designed and developed. Based on a thermochemical sorption reaction, space heating, cooling and generation of domestic hot water will be achieved with up to 100% renewable energy, by using solar energy

Solar Water Splitting Using Semiconductor Photocatalyst Powders

KAUST Repository

Takanabe, Kazuhiro

2015-07-01

Solar energy conversion is essential to address the gap between energy production and increasing demand. Large scale energy generation from solar energy can only be achieved through equally large scale collection of the solar spectrum. Overall water splitting using heterogeneous photocatalysts with a single semiconductor enables the direct generation of H from photoreactors and is one of the most economical technologies for large-scale production of solar fuels. Efficient photocatalyst materials are essential to make this process feasible for future technologies. To achieve efficient photocatalysis for overall water splitting, all of the parameters involved at different time scales should be improved because the overall efficiency is obtained by the multiplication of all these fundamental efficiencies. Accumulation of knowledge ranging from solid-state physics to electrochemistry and a multidisciplinary approach to conduct various measurements are inevitable to be able to understand photocatalysis fully and to improve its efficiency.

Assessment of thermochemical hydrogen production. Project 61010 (formerly 8994) final report, July 1, 1977-March 31, 1979

Energy Technology Data Exchange (ETDEWEB)

Dafler, J.R.; Foh, S.E.; Lee, T.S.; Schreiber, J.D.

1979-05-01

The Institute of Gas Technology's (IGT) assessment of thermochemical water-splitting processes is given. Eight tasks were performed: evaluation of load-line efficiencies; hydrogen bromide electrolysis; maximum attainable thermal efficiency on a specific bromide hybrid cycle; development of electrolyzer elements for H/sub 2/SO/sub 3/; feasibility of high-temperature reference-state thermochemical cycles; interfacing characteristics - solar high-temperature heat sources; analysis of solar and solar hybrid heat sources; and laboratory assessment of cycle with high-temperature step. Engineering analyses were done on two thermochemical hydrogen production cycles - IGT's cycles B-1 and H-5. The load line efficiency for B-1 was 18.1% and for H-5 37.4%. The electrolysis of HBr (aq) on three substrates: platinum, porous graphite, and vitreous graphite was investigated. Platinum proved to be the most efficient electrode surface, with vitreous graphite showing no promise, and porous graphite showing only slightly better results. On platinum, cell voltages of under 1.0 volt were obtained at current densities up to 200 mA/cm/sup 2/. Five new members of the metal-metal oxide class of cycles were derived. The maximum attainable efficiencies of these high-temperature, two-step cycles range from 64 to 86%. Six high-temperature metal oxide-metal sulfate cycles were derived. Performance and capital costs data for a wide range of solar primary heat sources were tabulated.

Hydrogen production at <550 C using a low temperature thermochemical cycle

International Nuclear Information System (INIS)

Lewis, M.A.; Serban, M.; Basco, J.K.

2004-01-01

A Department of Energy goal is to identify new technologies for producing hydrogen cost effectively without greenhouse gas emissions. Thermochemical cycles are one of the potential options under investigation. Thermochemical cycles consist of a series of reactions in which water is thermally decomposed and all other chemicals are recycled. Only heat and water are consumed. However, most thermochemical cycles require process heat at temperatures of 850-900 deg C. Argonne National Laboratory is developing low temperature cycles designed for lower temperature heat, 500-550 deg C, which is more readily available. For this temperature region, copper-chlorine (Cu-Cl) cycles are the most promising cycle. Several Cu-Cl cycles have been examined in the laboratory and the most promising cycle has been identified. Proof-of-principle experiments are nearly complete. A preliminary assessment of cycle efficiency is promising. Details of the experiments and efficiency calculations are discussed. (author)

Bibliographic Review about Solar Hydrogen Production Through Thermochemical Cycles; Revision Bibliografica sobre la Produccion de Hidrogeno Solar Mediante Ciclos Termoquimicos

Energy Technology Data Exchange (ETDEWEB)

Fernandez Saavedra, R.

2007-12-28

This report presents a summary of the different thermical processes used to obtain hydrogen through solar energy, paying more attention to the production of hydrogen from water through thermochemical cycles. In this aspect, it is briefly described the most interesting thermochemical cycles, focusing on thermochemical cycles based on oxides. (Author) 25 refs.

Bibliographic Review about Solar Hydrogen Production Through Thermochemical Cycles; Revision Bibliografica sobre la Produccion de Hidrogeno Solar Mediante Ciclos Termoquimicos

Energy Technology Data Exchange (ETDEWEB)

Fernandez Saavedra, R.

2008-08-06

This report presents a summary of the different thermical processes used to obtain hydrogen through solar energy, paying more attention to the production of hydrogen from water through thermochemical cycles. In this aspect, it is briefly y described the most interesting thermochemical cycles, focusing on thermochemical cycles based on oxides. (Author) 25 refs.

Tantalum-based semiconductors for solar water splitting.

Science.gov (United States)

Zhang, Peng; Zhang, Jijie; Gong, Jinlong

2014-07-07

Solar energy utilization is one of the most promising solutions for the energy crises. Among all the possible means to make use of solar energy, solar water splitting is remarkable since it can accomplish the conversion of solar energy into chemical energy. The produced hydrogen is clean and sustainable which could be used in various areas. For the past decades, numerous efforts have been put into this research area with many important achievements. Improving the overall efficiency and stability of semiconductor photocatalysts are the research focuses for the solar water splitting. Tantalum-based semiconductors, including tantalum oxide, tantalate and tantalum (oxy)nitride, are among the most important photocatalysts. Tantalum oxide has the band gap energy that is suitable for the overall solar water splitting. The more negative conduction band minimum of tantalum oxide provides photogenerated electrons with higher potential for the hydrogen generation reaction. Tantalates, with tunable compositions, show high activities owning to their layered perovskite structure. (Oxy)nitrides, especially TaON and Ta3N5, have small band gaps to respond to visible-light, whereas they can still realize overall solar water splitting with the proper positions of conduction band minimum and valence band maximum. This review describes recent progress regarding the improvement of photocatalytic activities of tantalum-based semiconductors. Basic concepts and principles of solar water splitting will be discussed in the introduction section, followed by the three main categories regarding to the different types of tantalum-based semiconductors. In each category, synthetic methodologies, influencing factors on the photocatalytic activities, strategies to enhance the efficiencies of photocatalysts and morphology control of tantalum-based materials will be discussed in detail. Future directions to further explore the research area of tantalum-based semiconductors for solar water splitting

Photoelectrochemical water splitting: optimizing interfaces and light absorption

NARCIS (Netherlands)

Park, Sun-Young

2015-01-01

In this thesis several photoelectrochemical water splitting devices based on semiconductor materials were investigated. The aim was the design, characterization, and fabrication of solar-to-fuel devices which can absorb solar light and split water to produce hydrogen.

Microencapsulation of salts for enhanced thermochemical storage materials

NARCIS (Netherlands)

Cuypers, R.; Jong, A.J. de; Eversdijk, J.; Spijker, J.C. van 't; Oversloot, H.P.; Ingenhut, B.L.J.; Cremers, R.K.H.; Papen-Botterhuis, N.E.

2013-01-01

Thermochemical storage is a new and emerging long-term thermal storage for residential use (cooling, heating & domestic hot water generation), offering high thermal storage density without the need for thermal insulation during storage (Fig. 1). However, existing materials for thermochemical storage

Overview of recent advances in thermo-chemical conversion of biomass

International Nuclear Information System (INIS)

Zhang Linghong; Xu Chunbao; Champagne, Pascale

2010-01-01

Energy from biomass, bioenergy, is a perspective source to replace fossil fuels in the future, as it is abundant, clean, and carbon dioxide neutral. Biomass can be combusted directly to generate heat and electricity, and by means of thermo-chemical and bio-chemical processes it can be converted into bio-fuels in the forms of solid (e.g., charcoal), liquid (e.g., bio-oils, methanol and ethanol), and gas (e.g., methane and hydrogen), which can be used further for heat and power generation. This paper provides an overview of the principles, reactions, and applications of four fundamental thermo-chemical processes (combustion, pyrolysis, gasification, and liquefaction) for bioenergy production, as well as recent developments in these technologies. Some advanced thermo-chemical processes, including co-firing/co-combustion of biomass with coal or natural gas, fast pyrolysis, plasma gasification and supercritical water gasification, are introduced. The advantages and disadvantages, potential for future applications and challenges of these processes are discussed. The co-firing of biomass and coal is the easiest and most economical approach for the generation of bioenergy on a large-sale. Fast pyrolysis has attracted attention as it is to date the only industrially available technology for the production of bio-oils. Plasma techniques, due to their high destruction and reduction efficiencies for any form of waste, have great application potential for hazardous waste treatment. Supercritical water gasification is a promising approach for hydrogen generation from biomass feedstocks, especially those with high moisture contents.

Towards Highly Efficient Bias-Free Solar Water Splitting

NARCIS (Netherlands)

Abdi, F.F.

2013-01-01

Solar water splitting has attracted significant attention due to its potential of converting solar to chemical energy. It uses semiconductor to convert sunlight into electron-hole pairs, which then split water into hydrogen and oxygen. The hydrogen can be used as a renewable fuel, or it can serve as

Highly Efficient Photocatalytic Water Splitting over Edge-Modified Phosphorene Nanoribbons.

Science.gov (United States)

Hu, Wei; Lin, Lin; Zhang, Ruiqi; Yang, Chao; Yang, Jinlong

2017-11-01

Two-dimensional phosphorene with desirable optoelectronic properties (ideal band gap, high carrier mobility, and strong visible light absorption) is a promising metal-free photocatalyst for water splitting. However, the band edge positions of the valence band maximum (VBM) and conduction band maximum (CBM) of phosphorene are higher than the redox potentials in photocatalytic water splitting reactions. Thus, phosphorene can only be used as the photocathode for hydrogen evolution reaction as a low-efficiency visible-light-driven photocatalyst for hydrogen production in solar water splitting cells. Here, we propose a new mechanism to improve the photocatalytic efficiency of phosphorene nanoribbons (PNRs) by modifying their edges for full reactions in photocatalytic water splitting. By employing first-principles density functional theory calculations, we find that pseudohalogen (CN and OCN) passivated PNRs not only show desired VBM and CBM band edge positions induced by edge electric dipole layer, but also possess intrinsic optoelectronic properties of phosphorene, for both water oxidation and hydrogen reduction in photocatalytic water splitting without using extra energy. Furthermore, our calculations also predict that the maximum energy conversion efficiency of heterojunction solar cells consisting of different edge-modified PNRs can be as high as 20% for photocatalytic water splitting.

Photoelectrochemical solar water splitting: From basic principles to advanced devices

Directory of Open Access Journals (Sweden)

Bandar Y.Alfaifi

2018-02-01

Full Text Available Photoelectrochemical water splitting (PEC offers a promising path for sustainable generation of hydrogen fuel. However, improving solar fuel water splitting efficiency facing tremendous challenges, due to the energy loss related to fast recombination of the photogenerated charge carriers, electrode degradation, as well as limited light harvesting. This review focuses on the brief introduction of basic fundamental of PEC water splitting and the concept of various types of water splitting approaches. Numerous engineering strategies for the investgating of the higher efficiency of the PEC, including charge separation, light harvesting, and co-catalysts doping, have been discussed. Moreover, recent remarkable progress and developments for PEC water splitting with some promising materials are discussed. Recent advanced applications of PEC are also reviewed. Finally, the review concludes with a summary and future outlook of this hot field.

Photocatalytic water splitting: Quantitative approaches toward photocatalysis by design

KAUST Repository

Takanabe, Kazuhiro

2017-10-11

A widely used term, “photocatalysis”, generally addresses photocatalytic (energetically down-hill) and photosynthetic (energetically up-hill) reactions and refers to the use of photonic energy as a driving force for chemical transformations, i.e., electron reorganization to form/break chemical bonds. Although there are many such important reactions, this contribution focuses on the fundamental aspects of photocatalytic water splitting into hydrogen and oxygen by using light from the solar spectrum, which is one of the most investigated photosynthetic reactions. Photocatalytic water splitting using solar energy is considered to be artificial photosynthesis that produces a solar fuel because the reaction mimics nature’s photosynthesis not only in its redox reaction type but also in its thermodynamics (water splitting: 1.23 eV vs. glucose formation: 1.24 eV). To achieve efficient photocatalytic water splitting, all of the parameters, though involved at different timescales and spatial resolutions, should be optimized because the overall efficiency is obtained as the multiplication of all these fundamental efficiencies. The purpose of this review article is to provide the guidelines of a concept, “photocatalysis by design”, which is the opposite of “black box screening”; this concept refers to making quantitative descriptions of the associated physical and chemical properties to determine which events/parameters have the most impact on improving the overall photocatalytic performance, in contrast to arbitrarily ranking different photocatalyst materials. First, the properties that can be quantitatively measured or calculated are identified. Second, the quantities of these identified properties are determined by performing adequate measurements and/or calculations. Third, the obtained values of these properties are integrated into equations so that the kinetic/energetic bottlenecks of specific properties/processes can be determined, and the properties can

Photocatalytic water splitting: Quantitative approaches toward photocatalysis by design

KAUST Repository

Takanabe, Kazuhiro

2017-01-01

A widely used term, “photocatalysis”, generally addresses photocatalytic (energetically down-hill) and photosynthetic (energetically up-hill) reactions and refers to the use of photonic energy as a driving force for chemical transformations, i.e., electron reorganization to form/break chemical bonds. Although there are many such important reactions, this contribution focuses on the fundamental aspects of photocatalytic water splitting into hydrogen and oxygen by using light from the solar spectrum, which is one of the most investigated photosynthetic reactions. Photocatalytic water splitting using solar energy is considered to be artificial photosynthesis that produces a solar fuel because the reaction mimics nature’s photosynthesis not only in its redox reaction type but also in its thermodynamics (water splitting: 1.23 eV vs. glucose formation: 1.24 eV). To achieve efficient photocatalytic water splitting, all of the parameters, though involved at different timescales and spatial resolutions, should be optimized because the overall efficiency is obtained as the multiplication of all these fundamental efficiencies. The purpose of this review article is to provide the guidelines of a concept, “photocatalysis by design”, which is the opposite of “black box screening”; this concept refers to making quantitative descriptions of the associated physical and chemical properties to determine which events/parameters have the most impact on improving the overall photocatalytic performance, in contrast to arbitrarily ranking different photocatalyst materials. First, the properties that can be quantitatively measured or calculated are identified. Second, the quantities of these identified properties are determined by performing adequate measurements and/or calculations. Third, the obtained values of these properties are integrated into equations so that the kinetic/energetic bottlenecks of specific properties/processes can be determined, and the properties can

Biomass thermochemical conversion program: 1987 annual report

Energy Technology Data Exchange (ETDEWEB)

Schiefelbein, G.F.; Stevens, D.J.; Gerber, M.A.

1988-01-01

The objective of the Biomass Thermochemical Conversion Program is to generate a base of scientific data and conversion process information that will lead to establishment of cost-effective processes for conversion of biomass resources into clean fuels. To accomplish this objective, in fiscal year 1987 the Thermochemical Conversion Program sponsored research activities in the following four areas: Liquid Hydrocarbon Fuels Technology; Gasification Technology; Direct Combustion Technology; Program Support Activities. In this report an overview of the Thermochemical Conversion Program is presented. Specific research projects are then described. Major accomplishments for 1987 are summarized.

Holistic analysis of thermochemical processes by using solid biomass for fuel production in Germany

International Nuclear Information System (INIS)

Henssler, Martin

2015-01-01

According to the German act ''Biokraftstoff-Nachhaltigkeitsverordnung'', biofuels must show a CO 2eq -reduction compared to the fossil reference fuel (83.8 g CO 2eq /MJ fuel /Richtlinie 98/70/EG/) of 35 % beginning with 2011. In new plants, which go into operation after the 31.12.2016 the CO 2eq -savings must be higher than 50 % in 2017 and higher than 60 % in 2018 /Biokraft-NachV/. The biofuels (methyl ester of rapeseed, bioethanol and biomethane) considered in this study do not meet these requirements for new plants. To comply with these rules new processes must be deployed. Alternative thermochemical generated fuels could be an option. The aim of this work is to evaluate through a technical, ecological and economic analysis (Well-to-Wheel) whether and under what conditions the thermochemical production of Fischer-Tropsch-diesel or -gasoline, hydrogen (H 2 ) and Substitute Natural Gas (SNG) complies with the targets. Four different processes are considered (fast pyrolysis and torrefaction with entrained flow gasifier, CHOREN Carbo-V registered -gasifier, Absorption Enhanced Reforming (AER-) gasifier). Beside residues such as winter wheat straw and residual forest wood, wood from short-rotation plantations is taken into account. The technical analysis showed that at present status (2010) two and in 2050 six plants can be operated energy-self-sufficient. The overall efficiency of the processes is in the range of 41.5 (Fischer-Tropsch-diesel or -gasoline) and 59.4 % (H 2 ). Furthermore, it was found that for 2010, all thermochemical produced fuels except the H 2 -production from wood from short-rotation plantations in decentralised or central fast pyrolysis and in decentralised torrefactions with entrained flow gasifier keep the required CO 2eq -saving of 60 %. In 2050, all thermochemical produced fuels will reach these limits. The CO 2eq -saving is between 72 (H 2 ) and 95 % (Fischer-Tropsch-diesel or -gasoline). When the production costs of the

Chemical engineering challenges in driving thermochemical hydrogen processes with the tandem mirror reactor

International Nuclear Information System (INIS)

Galloway, T.R.; Werner, R.W.

1980-01-01

The Tandem Mirror Reactor is described and compared with Tokamaks, both from a basic physics viewpoint and from the suitability of the respective reactor for synfuel production. Differences and similarities between the TMR as an electricity producer or a synfuel producer are also cited. The Thermochemical cycle chosen to link with the fusion energy source is the General Atomic Sulfur-Iodine Cycle, which is a purely thermal-driven process with no electrochemical steps. There are real chemical engineering challenges of getting this high quality heat into the large thermochemical plant in an efficient manner. We illustrate with some of our approaches to providing process heat via liquid sodium to drive a 1050 K, highly-endothermic, catalytic and fluidized-bed SO 3 Decomposition Reactor. The technical, economic, and safety tradeoffs that arise are discussed

Dye-sensitized photocatalyst for effective water splitting catalyst

Science.gov (United States)

Watanabe, Motonori

2017-12-01

Renewable hydrogen production is a sustainable method for the development of next-generation energy technologies. Utilising solar energy and photocatalysts to split water is an ideal method to produce hydrogen. In this review, the fundamental principles and recent progress of hydrogen production by artificial photosynthesis are reviewed, focusing on hydrogen production from photocatalytic water splitting using organic-inorganic composite-based photocatalysts.

Thermochemical transformations of anthracite fractions

Energy Technology Data Exchange (ETDEWEB)

Belkina, T.V.; Privalov, V.E.; Stepanenko, atM.A.

1979-08-01

Research on the nature of thermochemical transformations of anthracite fractions and the possibility of increasing their activity and identifying conditions for their use in the electrode pitch process is described. From research done on different anthracite fractions processed at varying temperatures it was concluded that accumulations of condensates from heating anthracite fractions occur significantly slower in comparison with pitch. As a result the electrode pitch process is prolonged. Thermal treatment of an anthracite fraction causes the formation and accumulation of condensates and promotes thermochemical transformations. Lastly, the use of thermally treated anthracite fractions apparently intensifies the electrode pitch process and improves its quality. (16 refs.) (In Russian)

Comparative Life Cycle Assessment of Lignocellulosic Ethanol Production: Biochemical Versus Thermochemical Conversion

Science.gov (United States)

Mu, Dongyan; Seager, Thomas; Rao, P. Suresh; Zhao, Fu

2010-10-01

Lignocellulosic biomass can be converted into ethanol through either biochemical or thermochemical conversion processes. Biochemical conversion involves hydrolysis and fermentation while thermochemical conversion involves gasification and catalytic synthesis. Even though these routes produce comparable amounts of ethanol and have similar energy efficiency at the plant level, little is known about their relative environmental performance from a life cycle perspective. Especially, the indirect impacts, i.e. emissions and resource consumption associated with the production of various process inputs, are largely neglected in previous studies. This article compiles material and energy flow data from process simulation models to develop life cycle inventory and compares the fossil fuel consumption, greenhouse gas emissions, and water consumption of both biomass-to-ethanol production processes. The results are presented in terms of contributions from feedstock, direct, indirect, and co-product credits for four representative biomass feedstocks i.e., wood chips, corn stover, waste paper, and wheat straw. To explore the potentials of the two conversion pathways, different technological scenarios are modeled, including current, 2012 and 2020 technology targets, as well as different production/co-production configurations. The modeling results suggest that biochemical conversion has slightly better performance on greenhouse gas emission and fossil fuel consumption, but that thermochemical conversion has significantly less direct, indirect, and life cycle water consumption. Also, if the thermochemical plant operates as a biorefinery with mixed alcohol co-products separated for chemicals, it has the potential to achieve better performance than biochemical pathway across all environmental impact categories considered due to higher co-product credits associated with chemicals being displaced. The results from this work serve as a starting point for developing full life cycle

Fusion as a source of synthetic fuels

International Nuclear Information System (INIS)

Powell, J.R.; Fillo, J.A.; Steinberg, M.

1981-01-01

In the near-term, coal derived synthetic fuels will be used; but in the long-term, resource depletion and environmental effects will mandate synthetic fuels from inexhaustible sources - fission, fusion, and solar. Of the three sources, fusion appears uniquely suited for the efficient production of hydrogen-based fuels, due to its ability to directly generate very high process temperatures (up to approx. 2000 0 C) for water splitting reactions. Fusion-based water splitting reactions include high temperature electrolysis (HTE) of steam, thermochemical cycles, hybrid electrochemical/thermochemical, and direct thermal decomposition. HTE appears to be the simplest and most efficient process with efficiencies of 50 to 70% (fusion to hydrogen chemical energy), depending on process conditions

Solar thermochemical production of ammonia from water, air and sunlight: Thermodynamic and economic analyses

International Nuclear Information System (INIS)

Michalsky, Ronald; Parman, Bryon J.; Amanor-Boadu, Vincent; Pfromm, Peter H.

2012-01-01

Ammonia is an important input into agriculture and is used widely as base chemical for the chemical industry. It has recently been proposed as a sustainable transportation fuel and convenient one-way hydrogen carrier. Employing typical meteorological data for Palmdale, CA, solar energy is considered here as an inexpensive and renewable energy alternative in the synthesis of NH 3 at ambient pressure and without natural gas. Thermodynamic process analysis shows that a molybdenum-based solar thermochemical NH 3 production cycle, conducted at or below 1500 K, combined with solar thermochemical H 2 production from water may operate at a net-efficiency ranging from 23 to 30% (lower heating value of NH 3 relative to the total energy input). Net present value optimization indicates ecologically and economically sustainable NH 3 synthesis at above about 160 tons NH 3 per day, dependent primarily on heliostat costs (varied between 90 and 164 dollars/m 2 ), NH 3 yields (ranging from 13.9 mol% to stoichiometric conversion of fixed and reduced nitrogen to NH 3 ), and the NH 3 sales price. Economically feasible production at an optimum plant capacity near 900 tons NH 3 per day is shown at relative conservative technical assumptions and at a reasonable NH 3 sales price of about 534 ± 28 dollars per ton NH 3 . -- Highlights: ► Conceptual reactant and process improvements of solar-driven NH 3 synthesis at 1 bar. ► Thermodynamic underpinnings of a Molybdenum reactant. ► Process analysis determining energy and materials requirements and the net-efficiency. ► Net present value analysis accounting for yield, investment, and sales price variations.

Anisotropic diamond etching through thermochemical reaction between Ni and diamond in high-temperature water vapour.

Science.gov (United States)

Nagai, Masatsugu; Nakanishi, Kazuhiro; Takahashi, Hiraku; Kato, Hiromitsu; Makino, Toshiharu; Yamasaki, Satoshi; Matsumoto, Tsubasa; Inokuma, Takao; Tokuda, Norio

2018-04-27

Diamond possesses excellent physical and electronic properties, and thus various applications that use diamond are under development. Additionally, the control of diamond geometry by etching technique is essential for such applications. However, conventional wet processes used for etching other materials are ineffective for diamond. Moreover, plasma processes currently employed for diamond etching are not selective, and plasma-induced damage to diamond deteriorates the device-performances. Here, we report a non-plasma etching process for single crystal diamond using thermochemical reaction between Ni and diamond in high-temperature water vapour. Diamond under Ni films was selectively etched, with no etching at other locations. A diamond-etching rate of approximately 8.7 μm/min (1000 °C) was successfully achieved. To the best of our knowledge, this rate is considerably greater than those reported so far for other diamond-etching processes, including plasma processes. The anisotropy observed for this diamond etching was considerably similar to that observed for Si etching using KOH.

Thermochemical Surface Engineering: A Playground for Science and Innovation

DEFF Research Database (Denmark)

Christiansen, Thomas Lundin; Dahl, Kristian Vinter; Jellesen, Morten Stendahl

2017-01-01

Surface engineering by thermochemical processing is the intentional change of the composition of a material at elevated temperature with the purpose to improve materials performance. In thermochemical processing components from the starting material are essential in the development of the phases...... at the surface. Current research and innovation activities are used to exemplify thermochemical surface engineering and the interplay of science and innovation. The examples given encompass aspects of the synthesis of extremely porous materials, low temperature surface hardening of stainless steel, surface...

Photoelectrochemical devices for solar water splitting - materials and challenges.

Science.gov (United States)

Jiang, Chaoran; Moniz, Savio J A; Wang, Aiqin; Zhang, Tao; Tang, Junwang

2017-07-31

It is widely accepted within the community that to achieve a sustainable society with an energy mix primarily based on solar energy we need an efficient strategy to convert and store sunlight into chemical fuels. A photoelectrochemical (PEC) device would therefore play a key role in offering the possibility of carbon-neutral solar fuel production through artificial photosynthesis. The past five years have seen a surge in the development of promising semiconductor materials. In addition, low-cost earth-abundant co-catalysts are ubiquitous in their employment in water splitting cells due to the sluggish kinetics of the oxygen evolution reaction (OER). This review commences with a fundamental understanding of semiconductor properties and charge transfer processes in a PEC device. We then describe various configurations of PEC devices, including single light-absorber cells and multi light-absorber devices (PEC, PV-PEC and PV/electrolyser tandem cell). Recent progress on both photoelectrode materials (light absorbers) and electrocatalysts is summarized, and important factors which dominate photoelectrode performance, including light absorption, charge separation and transport, surface chemical reaction rate and the stability of the photoanode, are discussed. Controlling semiconductor properties is the primary concern in developing materials for solar water splitting. Accordingly, strategies to address the challenges for materials development in this area, such as the adoption of smart architectures, innovative device configuration design, co-catalyst loading, and surface protection layer deposition, are outlined throughout the text, to deliver a highly efficient and stable PEC device for water splitting.

Development of Efficient Flowsheet and Transient Modeling for Nuclear Heat Coupled Sulfur Iodine Cyclefor Hydrogen Production

Energy Technology Data Exchange (ETDEWEB)

Shripad T. Revankar; Nicholas R. Brown; Cheikhou Kane; Seungmin Oh

2010-05-01

The realization of the hydrogen as an energy carrier for future power sources relies on a practical method of producing hydrogen in large scale with no emission of green house gases. Hydrogen is an energy carrier which can be produced by a thermochemical water splitting process. The Sulfur-Iodine (SI) process is an example of a water splitting method using iodine and sulfur as recycling agents.

Biomass thermochemical conversion program. 1985 annual report

Energy Technology Data Exchange (ETDEWEB)

Schiefelbein, G.F.; Stevens, D.J.; Gerber, M.A.

1986-01-01

Wood and crop residues constitute a vast majority of the biomass feedstocks available for conversion, and thermochemical processes are well suited for conversion of these materials. The US Department of Energy (DOE) is sponsoring research on this conversion technology for renewable energy through its Biomass Thermochemical Conversion Program. The Program is part of DOE's Biofuels and Municipal Waste Technology Division, Office of Renewable Technologies. This report briefly describes the Thermochemical Conversion Program structure and summarizes the activities and major accomplishments during fiscal year 1985. 32 figs., 4 tabs.

Recent Advances in Bismuth-Based Nanomaterials for Photoelectrochemical Water Splitting.

Science.gov (United States)

Bhat, Swetha S M; Jang, Ho Won

2017-08-10

In recent years, bismuth-based nanomaterials have drawn considerable interest as potential candidates for photoelectrochemical (PEC) water splitting owing to their narrow band gaps, nontoxicity, and low costs. The unique electronic structure of bismuth-based materials with a well-dispersed valence band comprising Bi 6s and O 2p orbitals offers a suitable band gap to harvest visible light. This Review presents significant advancements in exploiting bismuth-based nanomaterials for solar water splitting. An overview of the different strategies employed and the new ideas adopted to improve the PEC performance of bismuth-based nanomaterials are discussed. Morphology control, the construction of heterojunctions, doping, and co-catalyst loading are several approaches that are implemented to improve the efficiency of solar water splitting. Key issues are identified and guidelines are suggested to rationalize the design of efficient bismuth-based materials for sunlight-driven water splitting. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photophysics and electrochemistry relevant to photocatalytic water splitting involved at solid–electrolyte interfaces

KAUST Repository

Shinagawa, Tatsuya

2016-08-04

Direct photon to chemical energy conversion using semiconductor-electrocatalyst-electrolyte interfaces has been extensively investigated for more than a half century. Many studies have focused on screening materials for efficient photocatalysis. Photocatalytic efficiency has been improved during this period but is not sufficient for industrial commercialization. Detailed elucidation on the photocatalytic water splitting process leads to consecutive six reaction steps with the fundamental parameters involved: The photocatalysis is initiated involving photophysics derived from various semiconductor properties (1: photon absorption, 2: exciton separation). The generated charge carriers need to be transferred to surfaces effectively utilizing the interfaces (3: carrier diffusion, 4: carrier transport). Consequently, electrocatalysis finishes the process by producing products on the surface (5: catalytic efficiency, 6: mass transfer of reactants and products). Successful photocatalytic water splitting requires the enhancement of efficiency at each stage. Most critically, a fundamental understanding of the interfacial phenomena is highly desired for establishing "photocatalysis by design" concepts, where the kinetic bottleneck within a process is identified by further improving the specific properties of photocatalytic materials as opposed to blind material screening. Theoretical modeling using the identified quantitative parameters can effectively predict the theoretically attainable photon-conversion yields. This article provides an overview of the state-of-the-art theoretical understanding of interfacial problems mainly developed in our laboratory. Photocatalytic water splitting (especially hydrogen evolution on metal surfaces) was selected as a topic, and the photophysical and electrochemical processes that occur at semiconductor-metal, semiconductor-electrolyte and metal-electrolyte interfaces are discussed.

Photocatalytic and Photoelectrochemical Water Splitting by Inorganic Materials

KAUST Repository

Deng, Xiaohui

2012-12-01

Hydrogen has been identified as a potential energy carrier due to its high energy capacity and environmental harmlessness. Compared with hydrogen production from hydrocarbons such as methane and naphtha in a conventional hydrogen energy system, photocatalytic hydrogen evolution from water splitting offers a more economic approach since it utilizes the abundant solar irradiation as energy source and water as initial reactant. Powder photocatalyst, which generates electrons and holes under illumination, is the origin where the overall reaction happens. High solar energy conversion efficiency especially from visible range is commonly the target. Besides, cocatalyst for hydrogen and oxygen evolution is also playing an essential role in facilitating the charge separation and enhancing the kinetics. In this thesis, the objective is to achieve high energy conversion efficiency towards water splitting from diverse aspects. The third chapter focuses on a controllable method to fabricate metal pattern, which is candidate for hydrogen evolution cocatalyst while chapter 4 is on the combination of strontium titanium oxide (SrTiO3) with graphene oxide (GO) for a better photocatalytic performance. In the last chapter, photoelectrochemical water splitting by Ta3N5 photoanode and FeOOH as a novel oxygen evolution cocatalyst has been investigated.

Study of the hydrolysis reaction of the copper-chloride hybrid thermochemical cycle using optical spectrometries

International Nuclear Information System (INIS)

Doizi, D.; Borgard, J.M.; Dauvois, V.; Roujou, J.L.; Zanella, Y.; Croize, L.; Cartes, Ph.; Hartmann, J.M.

2010-01-01

The copper-chloride hybrid thermochemical cycle is one of the best potential low temperature thermochemical cycles for the massive production of hydrogen. It could be used with nuclear reactors such as the sodium fast reactor or the supercritical water reactor. Nevertheless, this thermochemical cycle is composed of an electrochemical reaction and two thermal reactions. Its efficiency has to be compared with other hydrogen production processes like alkaline electrolysis for example. The purpose of this article is to study the viability of the copper chloride thermochemical cycle by studying the hydrolysis reaction of CuCl 2 which is not favoured thermodynamically. To better understand the occurrence of possible side reactions, together with a good control of the kinetics of the hydrolysis reaction, the use of optical absorption spectrometries, UV visible spectrometry to detect molecular chlorine which may be formed in side reactions, FTIR spectrometry to follow the concentrations of H 2 O and HCl is proposed. (authors)

Large Bandgap Semiconductors for Solar Water Splitting

DEFF Research Database (Denmark)

Malizia, Mauro

Photoelectrochemical water splitting represents an eco-friendly technology that could enable the production of hydrogen using water as reactant and solar energy as primary energy source. The exploitation of solar energy for the production of hydrogen would help modern society to reduce the reliance...... on fossil fuels as primary feedstock for hydrogen production and diminish the emission of greenhouse gases in the atmosphere, weakening the global warming phenomenon.The dissertation reports the development of GaP (gallium phosphide) photocathodes as a large bandgap semiconductor for photoelectrochemical...... water splitting devices having tandem design. The increase of the photovoltage produced by GaP under illumination was the main goal of this work. GaP has a bandgap of 2.25 eV and could in theory produce a photovoltage of approximately 1.7 V. Instead, the photovoltage produced by the semiconductor...

Thermal integration of SCWR nuclear and thermochemical hydrogen plants

International Nuclear Information System (INIS)

Wang, Z.; Naterer, G.F.; Gabriel, K.S.

2010-01-01

In this paper, the intermediate heat exchange between a Generation IV supercritical water-cooled nuclear reactor (SCWR) and a thermochemical hydrogen production cycle is discussed. It is found that the maximum and range of temperatures of a thermochemical cycle are the dominant parameters that affect the design of its coupling with SCWR. The copper-chlorine (Cu-Cl) thermochemical cycle is a promising cycle that can link with SCWRs. The location of extracting heat from a SCWR to a thermochemical cycle is investigated in this paper. Steam bypass lines downstream of the SCWR core are suggested for supplying heat to the Cu-Cl hydrogen production cycle. The stream extraction location is strongly dependent on the temperature requirements of the chemical steps of the thermochemical cycle. The available quantity of heat exchange at different hours of a day is also studied. It is found that the available heat at most hours of power demand in a day can support an industrial scale steam methane reforming plant if the SCWR power station is operating at full design capacity. (author)

LARGE-SCALE PRODUCTION OF HYDROGEN BY NUCLEAR ENERGY FOR THE HYDROGEN ECONOMY

International Nuclear Information System (INIS)

SCHULTZ, K.R.; BROWN, L.C.; BESENBRUCH, G.E.; HAMILTON, C.J.

2003-01-01

OAK B202 LARGE-SCALE PRODUCTION OF HYDROGEN BY NUCLEAR ENERGY FOR THE HYDROGEN ECONOMY. The ''Hydrogen Economy'' will reduce petroleum imports and greenhouse gas emissions. However, current commercial hydrogen production processes use fossil fuels and releases carbon dioxide. Hydrogen produced from nuclear energy could avoid these concerns. The authors have recently completed a three-year project for the US Department of Energy whose objective was to ''define an economically feasible concept for production of hydrogen, by nuclear means, using an advanced high-temperature nuclear reactor as the energy source''. Thermochemical water-splitting, a chemical process that accomplishes the decomposition of water into hydrogen and oxygen, met this objective. The goal of the first phase of this study was to evaluate thermochemical processes which offer the potential for efficient, cost-effective, large-scale production of hydrogen and to select one for further detailed consideration. The authors selected the Sulfur-Iodine cycle, In the second phase, they reviewed all the basic reactor types for suitability to provide the high temperature heat needed by the selected thermochemical water splitting cycle and chose the helium gas-cooled reactor. In the third phase they designed the chemical flowsheet for the thermochemical process and estimated the efficiency and cost of the process and the projected cost of producing hydrogen. These results are summarized in this paper

Enhanced Intermediate-Temperature CO2 Splitting Using Nonstoichiometric Ceria and Ceria-Zirconia

KAUST Repository

Zhao, Zhenlong; Uddi, Mruthunjaya; Tsvetkov, Nikolai; Yildiz, Bilge; Ghoniem, Ahmed F.

2017-01-01

CO2 splitting via thermo-chemical or reactive redox has emerged as a novel and promising carbon-neutral energy solution. Its performance depends critically on the properties of the oxygen carriers (OC). Ceria is recognized as one of the most

Kinetics of the hydrogen production reaction in a copper-chlorine water splitting plant

International Nuclear Information System (INIS)

Zamfirescu, C.; Naterer, G.F.; Dincer, I.

2009-01-01

The exothermic reaction of HCl with particulate Cu occurs during hydrogen production step in the thermochemical copper-chlorine (Cu-Cl) water splitting cycle. In this paper, this chemical reaction is modeled kinetically, and a parametric study is performed to determine the influences of particle size, temperature and molar ratios on the reaction kinetics. It is determined that the residence time of copper particles varies between 10 and 100 s, depending on the operating conditions. The hydrogen conversion at equilibrium varies between 55 and 85%, depending on the reaction temperature. The heat flux at the particle surface, caused by the exothermic enthalpy of reaction, reaches about 3,000 W/m 2 when the particle shrinks to 0.1% from its initial size. A numerical algorithm is developed to solve the moving boundary Stefan problem with a chemical reaction. It predicts the shrinking of copper particles based on the hypothesis that the chemical reaction and heat transfer are decoupled. The model allows for estimation of the temperature of the copper particle, assumed spherical, in the radial direction. The maximum temperature at the interface is higher than the melting point of CuCl by 10-50 o C, depending on the assumed operating conditions. (author)

Assessment of a closed thermochemical energy storage using energy and exergy methods

International Nuclear Information System (INIS)

Abedin, Ali Haji; Rosen, Marc A.

2012-01-01

Highlights: ► Thermodynamics assessments are reported for a general closed thermochemical thermal energy storage system. ► Energy and exergy efficiencies of various processes in a closed thermochemical TES are evaluated and compared. ► Understanding is enhanced of thermochemical TES technologies and their potential implementations. ► Exergy analysis is observed to be useful when applied to thermochemical TES, with or in place of energy analysis. - Abstract: Thermal energy storage (TES) is an important technology for achieving more efficient and environmentally benign energy systems. Thermochemical TES is a type of TES with the potential for high energy density and is only recently being considered intensively. To improve understanding of thermochemical TES systems and their implementation, energy and exergy analyses are beneficial. Here, thermodynamics assessments are presented for a general closed thermochemical TES system, including assessments and comparisons of the efficiencies of the overall thermochemical TES cycle and its charging, storing and discharging processes. Locations and causes of thermodynamic losses in thermochemical TES systems are being specified using exergy analysis. The analytical methodology applied in this study identifies that energy and exergy efficiencies differ for thermochemical TESs, e.g. the energy efficiency for a case study is approximately 50% while the exergy efficiency is about 10%. Although the focus is to evaluate thermodynamic efficiencies, other design parameters such as cost, and environmental impact also need to be examined in assessing thermochemical storage. The efficiencies for thermochemical TES provided here should be helpful for designing these energy systems and enhancing their future prospects.

Regularities of thermochemical characteristics of 1-1, 2-1, 3-1 electrolyte solutions in dimethyl sulfoxide-water and propylene carbonate water mixtures

International Nuclear Information System (INIS)

Vorob'ev, A.F.; Monaenkova, A.S.; AlekseeV, G.I.

1987-01-01

In an air-tight tilting calorimeter with an isothermal casing enthalpies of praseodymium chloride solution in water, dimethyl sulfoxide (DMSO) - water mixtures, contaning 3.86 and 18.53 mol.% DMSO, and propylene carbonate (PC) - water mixtures, containing 1.85 and 3.23 mol.% PC are measured. The enthalpies of praseodymium chloride solution in the given mixtures in case of infinite solution dilution are determined. Solvation enthalpies of praseodymium and neodymium chlorides, as well as alkali earth metal and magnesium chlorides in water and DMSO - water and PC - water mixtures are calculated. Regularities in thermochemical characteristics of solutions of the given salts in DMSO - water and PC - water mixtures are discussed

Thermal tests of a multi-tubular reactor for hydrogen production by using mixed ferrites thermochemical cycle

Science.gov (United States)

Gonzalez-Pardo, Aurelio; Denk, Thorsten; Vidal, Alfonso

2017-06-01

The SolH2 project is an INNPACTO initiative of the Spanish Ministry of Economy and Competitiveness, with the main goal to demonstrate the technological feasibility of solar thermochemical water splitting cycles as one of the most promising options to produce H2 from renewable sources in an emission-free way. A multi-tubular solar reactor was designed and build to evaluate a ferrite thermochemical cycle. At the end of this project, the ownership of this plant was transferred to CIEMAT. This paper reviews some additional tests with this pilot plant performed in the Plataforma Solar de Almería with the main goal to assess the thermal behavior of the reactor, evaluating the evolution of the temperatures inside the cavity and the relation between supplied power and reached temperatures. Previous experience with alumina tubes showed that they are very sensitive to temperature and flux gradients, what leads to elaborate an aiming strategy for the heliostat field to achieve a uniform distribution of the radiation inside the cavity. Additionally, the passing of clouds is a phenomenon that importantly affects all the CSP facilities by reducing their efficiency. The behavior of the reactor under these conditions has been studied.

Improvement in Performance of a Thermochemical Heat Storage System by Implementing an Internal Heat Recovery System

NARCIS (Netherlands)

Gaeini, M.; Saris, L.; Zondag, H.A.; Rindt, C.C.M.

A lab-scale prototype of a thermochemical heat storage system, employing a water-zeolite 13X as the working pair, is designed and optimized for providing hot tap water. During the hydration process, humid air is introduced to the packed bed reactor filled with dehydrated zeolite 13X, and the

Efficient Overall Water-Splitting Electrocatalysis Using Lepidocrocite VOOH Hollow Nanospheres

KAUST Repository

Shi, Huanhuan

2016-11-29

Herein we report the control synthesis of lepidocrocite VOOH hollow nanospheres and further their applications in electrocatalytic water splitting for the first time. By tuning the surface area of the nanospheres, the optimal performance can be achieved with low overpotentials of 270 mV for the oxygen evolution reaction (OER) and 164 mV for the hydrogen evolution reaction (HER) at 10 mA cm-2 in 1 m KOH, respectively. Furthermore, when used as both the anode and cathode for overall water splitting, a low cell voltage of 1.62 V is required to reach the current density of 10 mA cm-2 , making the VOOH hollow nanospheres an efficient alternative to water splitting.

Thermochemical performance analysis of solar driven CO_2 methane reforming

International Nuclear Information System (INIS)

Fuqiang, Wang; Jianyu, Tan; Huijian, Jin; Yu, Leng

2015-01-01

Increasing CO_2 emission problems create urgent challenges for alleviating global warming, and the capture of CO_2 has become an essential field of scientific research. In this study, a finite volume method (FVM) coupled with thermochemical kinetics was developed to analyze the solar driven CO_2 methane reforming process in a metallic foam reactor. The local thermal non-equilibrium (LTNE) model coupled with radiative heat transfer was developed to provide more temperature information. A joint inversion method based on chemical process software and the FVM coupled with thermochemical kinetics was developed to obtain the thermochemical reaction parameters and guarantee the calculation accuracy. The detailed thermal and thermochemical performance in the metal foam reactor was analyzed. In addition, the effects of heat flux distribution and porosity on the solar driven CO_2 methane reforming process were analyzed. The numerical results can serve as theoretical guidance for the solar driven CO_2 methane reforming application. - Highlights: • Solar driven CO_2 methane reforming process in metal foam reactor is analyzed. • FVM with chemical reactions was developed to analyze solar CO_2 methane reforming. • A joint inversion method was developed to obtain thermochemical reaction parameters. • Results can be a guidance for the solar driven CO_2 methane reforming application.

Electrochemical Water-Splitting Based on Hypochlorite Oxidation

Czech Academy of Sciences Publication Activity Database

Minhová Macounová, Kateřina; Simic, N.; Ahlberg, E.; Krtil, Petr

2015-01-01

Roč. 137, č. 23 (2015), s. 7262-7265 ISSN 0002-7863 Institutional support: RVO:61388955 Keywords : electrochemistry * hypochlorite oxidation * water-splitting Subject RIV: CG - Electrochemistry Impact factor: 13.038, year: 2015

Nanocrystals and Nanoclusters as Cocatalysts for Photocatalytic Water Splitting

KAUST Repository

Sinatra, Lutfan

2016-12-04

The energy consumptions worldwide have increased simultaneously with the growth of the population and of the economy. Nowadays, finding an alternative way to satisfy the energy demand is one of the great challenges for the future of humanity, especially due to the limitation of fossil fuels and their effect on global warming. Hydrogen, as an alternative fuel for the future, is very attractive. Compared to traditional methods, such as the steam reforming of natural gas or coal gasification, photocatalytic water splitting (PWS) is considered to be the most sustainable alternative for producing hydrogen as a future fuel. PWS usually relies on semiconductor material that can transform the absorbed solar photon into photogenerated electrons and holes, creating a photopotential which can drive the electrochemical production of molecular hydrogen from the reduction of water. Despite its promising application, semiconductor-based PWS usually suffers from low carrier mobility and short diffusion length. Furthermore, the recombination of photogenerated electrons and holes might occur, especially if there are no suitable reaction sites available on the surface of the semiconductor. In order to facilitate the catalytic reactions on the surface of the semiconductor, the presence of a cocatalyst is necessary in order to obtain more efficient PWS processes. To this day, noble metals such as Pt, Pd, RuO2 and IrO2 are still the benchmark cocatalysts for PWS. Nevertheless, due to their high cost and limited supply, it is mandatory to develop a suitable strategy and to identify more efficient materials. Therefore, within the framework of this dissertation, novel cocatalysts and strategies that can improve the efficiency of the photocatalytic water splitting processes have been developed. Firstly, we developed a cocatalyst combining noble metals and semiconductors by means of partial galvanic replacement of the Cu2O nanocrystal with Au. The deposition of this cocatalyst on TiO2 was

Investigation of Iron Oxide Morphology in a Cyclic Redox Water Splitting Process for Hydrogen Generation

Directory of Open Access Journals (Sweden)

Michael M. Bobek

2012-10-01

Full Text Available A solar fuels generation research program is focused on hydrogen production by means of reactive metal water splitting in a cyclic iron-based redox process. Iron-based oxides are explored as an intermediary reactive material to dissociate water molecules at significantly reduced thermal energies. With a goal of studying the resulting oxide chemistry and morphology, chemical assistance via CO is used to complete the redox cycle. In order to exploit the unique characteristics of highly reactive materials at the solar reactor scale, a monolithic laboratory scale reactor has been designed to explore the redox cycle at temperatures ranging from 675 to 875 K. Using high resolution scanning electron microscope (SEM and electron dispersive X-ray spectroscopy (EDS, the oxide morphology and the oxide state are quantified, including spatial distributions. These images show the change of the oxide layers directly after oxidation and after reduction. The findings show a significant non-stoichiometric O/Fe gradient in the atomic ratio following oxidation, which is consistent with a previous kinetics model, and a relatively constant, non-stoichiometric O/Fe atomic ratio following reduction.

Characterisation of agroindustrial solid residues as biofuels and potential application in thermochemical processes.

Science.gov (United States)

Virmond, Elaine; De Sena, Rennio F; Albrecht, Waldir; Althoff, Christine A; Moreira, Regina F P M; José, Humberto J

2012-10-01

In the present work, selected agroindustrial solid residues from Brazil - biosolids from meat processing wastewater treatment and mixture of sawdust with these biosolids; residues from apple and orange juice industries; sugarcane bagasse; açaí kernels (Euterpe oleracea) and rice husk - were characterised as solid fuels and an evaluation of their properties, including proximate and ultimate composition, energy content, thermal behaviour, composition and fusibility of the ashes was performed. The lower heating value of the biomasses ranged from 14.31 MJkg(-1) to 29.14 MJkg(-1), on a dry and ash free basis (daf), all presenting high volatile matter content, varying between 70.57 wt.% and 85.36 wt.% (daf) what improves the thermochemical conversion of the solids. The fouling and slagging tendency of the ashes was predicted based on the fuel ash composition and on the ash fusibility correlations proposed in the literature, which is important to the project and operation of biomass conversion systems. The potential for application of the Brazilian agroindustrial solid residues studied as alternative energy sources in thermochemical processes has been identified, especially concerning direct combustion for steam generation. Copyright © 2012 Elsevier Ltd. All rights reserved.

Investigation of innovative thermochemical energy storage processes and materials for building applications

OpenAIRE

Aydin, Devrim

2016-01-01

In this study, it is aimed to develop an innovative thermochemical energy storage system through material, reactor and process based investigations for building space heating applications. The developed system could be integrated with solar thermal collectors, photovoltaic panels or heat pumps to store any excess energy in the form of heat for later use. Thereby, it is proposed to address the problem of high operational costs and CO2 emissions released by currently used fossil fuel based heat...

Hydrogen production by water-splitting and HTGR

International Nuclear Information System (INIS)

Courvoisier, P.; Rastouin, J.; Tilliette, Z.C.

1976-01-01

Some aspects of the use of heat of nuclear origin for the production of hydrogen by water-splitting are considered. General notions pertaining to the yield of chemical cycles are discussed and the heat balance corresponding to two specific processes is evaluated. The possibilities of high temperature reactors, with respect to the coolant temperature levels, are examined from the standpoint of core design and technology of some components. Furthermore these reactors can lead to excellent use of nuclear fuel. The coupling of the nuclear reactor with the chemical plant by means of a secondary helium circuit gives rise to the design of an intermediate heat exchanger, which is an important component of the overall installation [fr

Design and reliability assessment of control systems for a nuclear-based hydrogen production plant with copper-chlorine thermochemical cycle

Energy Technology Data Exchange (ETDEWEB)

Al-Dabbagh, Ahmad W. [Faculty of Engineering and Applied Science, University of Ontario Institute of Technology, 2000 Simcoe Street North, Oshawa, Ontario, L1H 7K4 (Canada); Lu, Lixuan [Faculty of Energy Systems and Nuclear Science, Faculty of Engineering and Applied Science, University of Ontario Institute of Technology, 2000 Simcoe Street North, Oshawa, Ontario, L1H 7K4 (Canada)

2010-02-15

The thermochemical Copper-Chlorine (Cu-Cl) cycle is an emerging new method of nuclear-based hydrogen production. In the process, water is decomposed into hydrogen and oxygen through several physical and chemical processes. In this paper, a Distributed Control System (DCS) is designed for the thermochemical Cu-Cl cycle. The architecture and the communication networks of the DCS are discussed. Reliability of the DCS is assessed using fault trees. In the assessment, the impact of the malfunction of the actuators, sensors, controllers and communication networks on the overall system reliability is investigated. This provides key information for the selection of control system components, and determination of their inspection frequency and maintenance strategy. The hydrogen reactor unit, which is one of the major components in the thermochemical Cu-Cl cycle, is used to demonstrate the detailed design and analysis. (author)

Test fabrication of sulfuric acid decomposer applied for thermochemical hydrogen production IS process

International Nuclear Information System (INIS)

Noguchi, Hiroki; Terada, Atsuhiko; Kubo, Shinji; Onuki, Kaoru; Hino, Ryutaro; Ota, Hiroyuki

2007-07-01

Thermo-chemical Iodine-Sulfur (IS) process produces large amount of hydrogen effectively without carbon dioxide emission. Since the IS process uses strong acids such as sulfuric acid and hydriodic acid, it is necessary to develop large-scale chemical reactors featuring materials that exhibit excellent heat and corrosion resistance. A sulfuric acid decomposer is one of the key components of the IS process plant, in which sulfuric acid is evaporated and decomposed into water and sulfur trioxide under temperature range from 300degC to 500degC using the heat supplied by high temperature helium gas. The decomposer is exposed to severe corrosion condition of sulfuric acid boiling flow, where only the SiC ceramics shows good corrosion resistance. However, at the current status, it is very difficult to manufacture the large-scale SiC ceramics structure required in the commercial plant. Therefore, we devised a new concept of the decomposer, which featured a counter flow type heat exchanger consisting of cylindrical blocks made of SiC ceramics. Scale up can be realized by connecting the blocks in parallel and/or in series. This paper describes results of the design work and the test-fabrication study of the sulfuric acid decomposer, which was carried out in order to confirm its feasibility. (author)

High-temperature gas-cooled reactors and process heat

International Nuclear Information System (INIS)

Kasten, P.R.

1980-01-01

High-Temperature Gas-Cooled Reactors (HTGRs) are fueled with ceramic-coated microspheres of uranium and thorium oxides/carbides embedded in graphite blocks which are cooled with helium. Promising areas of HTGR application are in cogeneration, energy transport using Heat Transfer Salt, recovery of oils from oil shale, steam reforming of methane for chemical production, coal gasification, and in energy transfer using chemical heat jpipes in the long term. Further, HTGRs could be used as the energy source for hydrogen production through thermochemical water splitting in the long term. The potential market for Process Heat HTGRs is 100-200 large units by about the year 2020

Photochemical water splitting mediated by a C1 shuttle

KAUST Repository

Alderman, N. P.

2016-10-31

The possibility of performing photochemical water splitting in a two-stage system, separately releasing the H and O components, has been probed with two separate catalysts and in combination with a formaldehyde/formate shuttling redox couple. In the first stage, formaldehyde releases hydrogen vigorously in the presence of an Na[Fe(CN)]·10HO catalyst, selectively affording the formate anion. In the second stage, the formate anion is hydro-genated back to formaldehyde by water and in the presence of a BiWO photocatalyst whilst releasing oxygen. Both stages operate at room temperature and under visible light irradiation. The two separate photocatalysts are compatible since water splitting can also be obtained in one-pot experiments with simultaneous H/O evolution.

Photochemical water splitting mediated by a C1 shuttle

KAUST Repository

Alderman, N. P.; Sommers, J. M.; Viasus, C. J.; Wang, C. H T; Peneau, V.; Gambarotta, S.; Vidjayacoumar, B.; Al-Bahily, K. A.

2016-01-01

The possibility of performing photochemical water splitting in a two-stage system, separately releasing the H and O components, has been probed with two separate catalysts and in combination with a formaldehyde/formate shuttling redox couple. In the first stage, formaldehyde releases hydrogen vigorously in the presence of an Na[Fe(CN)]·10HO catalyst, selectively affording the formate anion. In the second stage, the formate anion is hydro-genated back to formaldehyde by water and in the presence of a BiWO photocatalyst whilst releasing oxygen. Both stages operate at room temperature and under visible light irradiation. The two separate photocatalysts are compatible since water splitting can also be obtained in one-pot experiments with simultaneous H/O evolution.

First-Principles View on Photoelectrochemistry: Water-Splitting as Case Study

Directory of Open Access Journals (Sweden)

Anders Hellman

2017-06-01

Full Text Available Photoelectrochemistry is truly an interdisciplinary field; a natural nexus between chemistry and physics. In short, photoelectrochemistry can be divided into three sub-processes, namely (i the creation of electron-hole pairs by light absorption; (ii separation/transport on the charge carriers and finally (iii the water splitting reaction. The challenge is to understand all three processes on a microscopic scale and, perhaps even more importantly, how to combine the processes in an optimal way. This review will highlight some first-principles insights to the above sub-processes, in~particular as they occur using metal oxides. Based on these insights, challenges and future directions of first-principles methods in the field of photoelectrochemistry will be discussed.

SolarSyngas: Results from a virtual institute developing materials and key components for solar thermochemical fuel production

Science.gov (United States)

Roeb, Martin; Steinfeld, Aldo; Borchardt, Günter; Feldmann, Claus; Schmücker, Martin; Sattler, Christian; Pitz-Paal, Robert

2016-05-01

The Helmholtz Virtual Institute (VI) SolarSynGas brings together expertise from solar energy research and materials science to develop metal oxide based redox materials and to integrate them in a suitable way into related process technologies for two-step thermochemical production of hydrogen and carbon monoxide from water and CO2. One of the foci of experimental investigation was exploring the impact of doping on the feasibility of ceria-based materials - mainly by Zr-doping. The results indicate that a certain Zr-content enhances the reducibility and therefore the splitting performance. Increasing the Zr-content to x = 0.15 improved the specific CO2-splitting performance by 50% compared to pure ceria. This finding agrees with theoretical studies attributing the improvements to lattice modification caused by the introduction of Zr4+. Thermogravimetric relaxation experiments and equilibrium oxygen isotope exchange experiments with subsequent depth profiling analysis were carried out on ceria. As a result the reduction reaction of even dense samples of pure ceria with a grain size of about 20 µm is surface reaction controlled. The structure of the derived expression for the apparent activation energy suggests that the chemical surface exchange coefficient should show only a very weak dependence on temperature for ceria doped with lower valence cations. A solar receiver reactor exhibiting a foam-type reticulated porous ceramics made of ceria was tested. It could be shown that applying dual-scale porosity to those foams with mm-size pores for effective radiative heat transfer during reduction and μm-size pores within its struts for enhanced kinetics during oxidation allows enhancing the performance of the reactor significantly. Also a particle process concept applying solid-solid heat recovery from redox particles in a high temperature solar thermochemical process was analysed that uses ceramic spheres as solid heat transfer medium. This concept can be implemented

Synfuels from fusion: producing hydrogen with the tandem mirror reactor and thermochemical cycles

International Nuclear Information System (INIS)

Ribe, F.L.; Werner, R.W.

1981-01-01

This report examines, for technical merit, the combination of a fusion reactor driver and a thermochemical plant as a means for producing synthetic fuel in the basic form of hydrogen. We studied: (1) one reactor type - the Tandem Mirror Reactor - wishing to use to advantage its simple central cell geometry and its direct electrical output; (2) two reactor blanket module types - a liquid metal cauldron design and a flowing Li 2 O solid microsphere pellet design so as to compare the technology, the thermal-hydraulics, neutronics and tritium control in a high-temperature operating mode (approx. 1200 K); (3) three thermochemical cycles - processes in which water is used as a feedstock along with a high-temperature heat source to produce H 2 and O 2

Assessment of thermochemical hydrogen production. Project 8994 mid-contract progress report, July 1--November 1, 1977. [Iron chloride and copper sulfate cycles

Energy Technology Data Exchange (ETDEWEB)

Dafler, J.R.; Foh, S.E.; Schreiber, J.D.

1977-12-01

We have completed the base-case (first-cut) flowsheet analysis for two thermochemical water-splitting cycles that have been under study at the Institute of Gas Technology: a four-step iron chloride cycle (denoted B-1) and a four-step copper sulfate cycle (denoted H-5). In the case of Cycle B-1, an energy balance has located the worst problem areas in the cycle, and flowsheet modifications have begun. Calculations of equilibrium effects due to the hydrolysis of ferrous chloride at pressures high enough to interface with projected hydrogen transmission systems will, apparently, necessitate higher temperature process heat input for this step. Higher pressure operation of some critical separation processes yields more favorable heat balances. For Cycle H-5, the unmodified (base-case) flowsheet indicates that reaction product separations will be relatively simple with respect to Cycle B-1. Work of Schuetz and others dealing with the electrolysis and thermodynamics of HBr/H/sub 2/O/SO/sub 2/ systems is being extensively reviewed. Work plans for this part of the contract are currently being reviewed.

Coupling the modular helium reactor to hydrogen production processes

International Nuclear Information System (INIS)

Richards, M.B.; Shenoy, A.S.; Schultz, K.R.

2004-01-01

Steam reforming of natural gas (methane) currently produces the bulk of hydrogen gas used in the world today. Because this process depletes natural gas resources and generates the greenhouse gas carbon dioxide as a by-product, there is a growing interest in using process heat and/or electricity generated by nuclear reactors to generate hydrogen by splitting water. Process heat from a high temperature nuclear reactor can be used directly to drive a set of chemical reactions, with the net result of splitting water into hydrogen and oxygen. For example, process heat at temperatures in the range 850 deg C to 950 deg C can drive the sulphur-iodine (S-I) thermochemical process to produce hydrogen with high efficiency. The S-I process produces highly pure hydrogen and oxygen, with formation, decomposition, regeneration, and recycle of the intermediate chemical reagents. Electricity can also 1)e used directly to split water, using conventional, low-temperature electrolysis (LTE). Hydrogen can also be produced with hybrid processes that use both process heat and electricity to generate hydrogen. An example of a hybrid process is high-temperature electrolysis (HTE), in which process heat is used to generate steam, which is then supplied to an electrolyzer to generate hydrogen. This process is of interest because the efficiency of electrolysis increases with temperature. Because of its high temperature capability, advanced stage of development relative to other high-temperature reactor concepts, and passive-safety features, the modular helium reactor (MHR) is well suited for producing hydrogen using nuclear energy. In this paper we investigate the coupling of the MHR to the S-I process, LTE, and HTE. These concepts are referred to as the H2-MHR. (author)

Heat transfer with a split water channel

International Nuclear Information System (INIS)

Krinsky, S.

1978-01-01

The heat transfer problem associated with the incidence of synchrotron radiation upon a vacuum chamber wall cooled by a single water channel was previously studied, and a numerical solution to the potential problem was found using the two-dimensional magnet program POISSON. Calculations were extended to consider the case of a split water channel using POISSON to solve the potential problem for a given choice of parameters. By optimizing the dimensions, boiling of the water can be avoided. A copper chamber is a viable solution to the heat transfer problem at a beam port

Pultrusion of a vertical axis wind turbine blade part-I: 3D thermo-chemical process simulation

NARCIS (Netherlands)

Baran, Ismet; Tutum, Cem C.; Hattel, Jesper H.; Akkerman, Remko

2015-01-01

A novel three dimensional thermo-chemical simulation of the pultrusion process is presented. A simulation is performed for the pultrusion of a NACA0018 blade profile having a curved geometry, as a part of the DeepWind project. The finite element/nodal control volume (FE/NCV) technique is used.

Pultrusion of a vertical axis wind turbine blade part-I: 3D thermo-chemical process simulation

DEFF Research Database (Denmark)

Baran, Ismet; Tutum, Cem Celal; Hattel, Jesper Henri

2015-01-01

novel three dimensional thermo-chemical simulation of the pultrusion process is presented. A simulation is performed for the pultrusion of a NACA0018 blade profile having a curved geometry, as a part of the DeepWind project. The finite element/nodal control volume (FE/NCV) technique is used. First...

Thermodynamic comparison of two processes of hydrogen production: steam methane reforming-A solar thermochemical process

International Nuclear Information System (INIS)

Gomri, Rabah; Boumaza, Mourad

2006-01-01

Hydrogen is mainly employed like primary product, for the synthesis of ammonia. The ammonia is synthesized by chemically combining hydrogen and nitrogen under pressure, in the presence of a catalyst. This ammonia is used, for the production of the nitrate fertilizers. Nowadays hydrogen gains more attention mainly because, it is regarded as a future significant fuel by much of experts. The widespread use of hydrogen as source of energy could help to reduce the concern concerning the safety of energy, the total change of climate and the quality of air. Hydrogen is presented then as an excellent alternate initially and as substitute thereafter. It can play a role even more significant than conventional energies. Indeed, it has the advantage of being nonpolluting and it can use the same means of transport as conventional energies. For Algeria, it proves of importance capital. It not only makes it possible to increase and diversify its energy reserves and its exports but also to provide for its energy needs which become increasingly significant. Although hydrogen can be produced starting from a large variety of resources using a range of various technologies, the natural gas is generally preferred and will remain in the near future the principal primary product for the manufacture of hydrogen. Currently the most effective means of production of hydrogen is the Steam Reforming of Natural Gas (SMR). This process is seen as a one of principal technologies for the production of hydrogen. The disadvantages of this process it's that it consumes a great quantity of primary energy and that it releases in the atmosphere the gases that contribute to the warming of the plane. Among the alternatives processes of hydrogen production one can quote solar thermochemical processes. In this study, an exergetic analysis of the process of hydrogen production based on Zn/ZnO redox reactions is presented. In the first part of this study, an exergetic analysis is made for a temperature of the

Design consideration on hydrogen production demonstration plant of thermochemical IS process

International Nuclear Information System (INIS)

Iwatsuki, Jin; Noguchi, Hiroki; Terada, Atsuhiko; Kubo, Shinji; Sakaba, Nariaki; Onuki, Kaoru; Hino, Ryutaro

2009-03-01

Preliminary design study was carried out on the hydrogen production demonstration plant of thermochemical IS process. In the pilot test, hydrogen production will be examined under prototypical condition using an apparatus made of industrial materials, which is driven by the sensible heat of helium gas heated by an electric heater that simulates the High Temperature Engineering Test Reactor (HTTR). Tentative system condition was defined considering the HTTR specification and the experience on the construction and the operation of the mock-up test facility using methane reforming for hydrogen production. The process condition and the system flow diagram were discussed to meet the system condition. Based on the defined process condition, types of the main components were discussed taking the corrosion resistance of the structural materials into consideration. Applicable rules and regulations were also surveyed regarding the plant construction and operation. (author)

Using Protection Layers for a 2-Photon Water Splitting Device

DEFF Research Database (Denmark)

Seger, Brian; Mei, Bastian Timo; Frydendal, Rasmus

2015-01-01

The 2-photon tandem device for photocatalytic water splitting has been theoretically shown to provide a higher efficiency than a single photon device(1). This increased efficiency can be achieved by having one material optimized to absorb high energy photons (large bandgap) and another material...... optimized to absorb low energy photons (small bandgap). To a large degree this approach has been hindered by corrosion issues. In this talk I will first discuss how our computational screening of 2,400 materials showed that very few materials can efficiently absorb light without corroding in water splitting...

Crystal Sinking Modeling for Designing Iodine Crystallizer in Thermochemical Sulfur-Iodine Hydrogen Production Process

Energy Technology Data Exchange (ETDEWEB)

Park, Byung Heung [Korea National University of Transportation, Chungju (Korea, Republic of); Jeong, Seong-Uk [Korea Institute of Energy Research, Daejeon (Korea, Republic of); Kang, Jeong Won [Korea University, Seoul (Korea, Republic of)

2014-12-15

SI process is a thermochemical process producing hydrogen by decomposing water while recycling sulfur and iodine. Various technologies have been developed to improve the efficiency on Section III of SI process, where iodine is separated and recycled. EED(electro-electrodialysis) could increase the efficiency of Section III without additional chemical compounds but a substantial amount of I{sub 2} from a process stream is loaded on EED. In order to reduce the load, a crystallization technology prior to EED is considered as an I{sub 2} removal process. In this work, I{sub 2} particle sinking behavior was modeled to secure basic data for designing an I{sub 2} crystallizer applied to I{sub 2}-saturated HI{sub x} solutions. The composition of HI{sub x} solution was determined by thermodynamic UVa model and correlation equations and pure properties were used to evaluate the solution properties. A multiphysics computational tool was utilized to calculate particle sinking velocity changes with respect to I{sub 2} particle radius and temperature. The terminal velocity of an I{sub 2} particle was estimated around 0.5 m/s under considered radius (1.0 to 2.5 mm) and temperature (10 to 50 .deg. C) ranges and it was analyzed that the velocity is more dependent on the solution density than the solution viscosity.

Particulate Photocatalyst Sheets Based on Carbon Conductor Layer for Efficient Z-Scheme Pure-Water Splitting at Ambient Pressure.

Science.gov (United States)

Wang, Qian; Hisatomi, Takashi; Suzuki, Yohichi; Pan, Zhenhua; Seo, Jeongsuk; Katayama, Masao; Minegishi, Tsutomu; Nishiyama, Hiroshi; Takata, Tsuyoshi; Seki, Kazuhiko; Kudo, Akihiko; Yamada, Taro; Domen, Kazunari

2017-02-01

Development of sunlight-driven water splitting systems with high efficiency, scalability, and cost-competitiveness is a central issue for mass production of solar hydrogen as a renewable and storable energy carrier. Photocatalyst sheets comprising a particulate hydrogen evolution photocatalyst (HEP) and an oxygen evolution photocatalyst (OEP) embedded in a conductive thin film can realize efficient and scalable solar hydrogen production using Z-scheme water splitting. However, the use of expensive precious metal thin films that also promote reverse reactions is a major obstacle to developing a cost-effective process at ambient pressure. In this study, we present a standalone particulate photocatalyst sheet based on an earth-abundant, relatively inert, and conductive carbon film for efficient Z-scheme water splitting at ambient pressure. A SrTiO 3 :La,Rh/C/BiVO 4 :Mo sheet is shown to achieve unassisted pure-water (pH 6.8) splitting with a solar-to-hydrogen energy conversion efficiency (STH) of 1.2% at 331 K and 10 kPa, while retaining 80% of this efficiency at 91 kPa. The STH value of 1.0% is the highest among Z-scheme pure water splitting operating at ambient pressure. The working mechanism of the photocatalyst sheet is discussed on the basis of band diagram simulation. In addition, the photocatalyst sheet split pure water more efficiently than conventional powder suspension systems and photoelectrochemical parallel cells because H + and OH - concentration overpotentials and an IR drop between the HEP and OEP were effectively suppressed. The proposed carbon-based photocatalyst sheet, which can be used at ambient pressure, is an important alternative to (photo)electrochemical systems for practical solar hydrogen production.

Manganese-based Materials Inspired by Photosynthesis for Water-Splitting

Directory of Open Access Journals (Sweden)

Harvey J.M. Hou

2011-09-01

Full Text Available In nature, the water-splitting reaction via photosynthesis driven by sunlight in plants, algae, and cyanobacteria stores the vast solar energy and provides vital oxygen to life on earth. The recent advances in elucidating the structures and functions of natural photosynthesis has provided firm framework and solid foundation in applying the knowledge to transform the carbon-based energy to renewable solar energy into our energy systems. In this review, inspired by photosynthesis robust photo water-splitting systems using manganese-containing materials including Mn-terpy dimer/titanium oxide, Mn-oxo tetramer/Nafion, and Mn-terpy oligomer/tungsten oxide, in solar fuel production are summarized and evaluated. Potential problems and future endeavors are also discussed.

The application of condensate water as an additional cooling media intermittently in condenser of a split air conditioning

Science.gov (United States)

Ardita, I. N.; Subagia, I. W. A.

2018-01-01

The condensate water produced by indoor a split air conditioning is usually not utilized and thrown away into the environment. The result of measurement shows that the temperature of condensate water produced by split air conditioning is quite low, that is 19-22 °C at the rate of 16-20 mL / min and it has PH balance. Under such conditions, Air Condensate produced by split air conditioning should still be recovered as an additional cooling medium on the condenser. This research will re-investigate the use of condensate water as an intermittent additional cooling of the condenser to increase the cooling capacity and performance of the air conditioning system. This research is done by experimental method whose implementation includes; designing and manufacturing of experimental equipment, mounting measuring tools, experimental data retrieval, data processing and yield analysis. The experimental results show that the use of condensate water as an intermittent additional cooling medium on split air conditioning condenser can increase the refrigeration effect about 2%, cooling capacity about 4% and 7% of COP system. Experimental results also show a decrease in power consumption in the system compressor about 3%

Computational Screening of Materials for Water Splitting Applications

DEFF Research Database (Denmark)

Castelli, Ivano Eligio

Design new materials for energy production in a photoelectrochemical cell, where water is split into hydrogen and oxygen by solar light, is one possible solution to the problem of increasing energy demand and storage. A screening procedure based on ab-initio density functional theory calculations...... Project database, which is based on the experimental ICSD database, and the bandgaps were calculated with focus on finding materials with potential as light harvesters. 24 materials have been proposed for the one-photon water splitting and 23 for the two-photon mechanism. Another method to obtain energy...... from Sun is using a photovoltaic cell that converts solar light into electricity. The absorption spectra of 70 experimentally known compounds, that are expected to be useful for light-to-electricity generation, have been calculated. 17 materials have been predicted to be promising for a single...

Solar energy conversion by photocatalytic overall water splitting

KAUST Repository

Takanabe, Kazuhiro

2015-01-01

to reduce capital cost. Overall water splitting (OWS) by powder-form photocatalysts directly produces H2 as a chemical energy in a single reactor, which does not require any complicated parabolic mirrors and electronic devices. Because of its simplicity

Photocatalytic Water-Splitting Reaction from Catalytic and Kinetic Perspectives

KAUST Repository

Hisatomi, Takashi; Takanabe, Kazuhiro; Domen, Kazunari

2014-01-01

Abstract: Some particulate semiconductors loaded with nanoparticulate catalysts exhibit photocatalytic activity for the water-splitting reaction. The photocatalysis is distinct from the thermal catalysis because photocatalysis involves photophysical

Silicon nanostructures-induced photoelectrochemical solar water splitting for energy applications

Energy Technology Data Exchange (ETDEWEB)

Dadwal, U.; Singh, R. [Nanoscale Research Facility (NRF), Indian Institute of Technology Delhi, Hauz Khas, New Delhi-110016 (India); Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi-110016 (India); Ranjan, Neha [Centre for Nanoscience and Nanotechnology, Jamia Millia Islamia, New Delhi-110025 (India)

2016-05-23

We study the photoelectrochemical (PEC) solar water splitting assisted with synthesized nanostructures. Si nanowires decorated with silver dendrite nanostructures have been synthesized using metal assisted wet chemical etching of (100) Si wafer. Etching has been carried out in an aqueous solution consisting of 5M HF and 0.02M AgNO{sub 3}. Investigations showed that such type of semiconductor nanostructures act as efficient working electrodes for the splitting of normal water in PEC method. An enhancement in the photon-to-current conversion efficiency and solar-to-hydrogen evolution was observed for obtaining a practical source of clean and renewable fuel.

Towards versatile and sustainable hydrogen production via electrocatalytic water splitting: Electrolyte engineering

KAUST Repository

Shinagawa, Tatsuya

2016-12-17

Recent advances in power generation from renewable resources necessitate conversion of electricity to chemicals and fuels in an efficient manner. The electrocatalytic water splitting is one of the most powerful and widespread technologies. The development of highly efficient, inexpensive, flexible and versatile water electrolysis devices is desired. This review discusses the significance and impact of the electrolyte on electrocatalytic performance. Depending on the circumstances where water splitting reaction is conducted, required solution conditions such as the identity and molarity of ions may significantly differ. Quantitative understanding of such electrolyte properties on electrolysis performance is effective to facilitate developing efficient electrocatalytic systems. The electrolyte can directly participate in reaction schemes (kinetics), electrode stability, and/or indirectly impacts the performance by influencing concentration overpotential (mass transport). This review aims to guide fine-tuning of the electrolyte properties, or electrolyte engineering, for (photo)electrochemical water splitting reactions.

Towards versatile and sustainable hydrogen production via electrocatalytic water splitting: Electrolyte engineering

KAUST Repository

Shinagawa, Tatsuya; Takanabe, Kazuhiro

2016-01-01

Recent advances in power generation from renewable resources necessitate conversion of electricity to chemicals and fuels in an efficient manner. The electrocatalytic water splitting is one of the most powerful and widespread technologies. The development of highly efficient, inexpensive, flexible and versatile water electrolysis devices is desired. This review discusses the significance and impact of the electrolyte on electrocatalytic performance. Depending on the circumstances where water splitting reaction is conducted, required solution conditions such as the identity and molarity of ions may significantly differ. Quantitative understanding of such electrolyte properties on electrolysis performance is effective to facilitate developing efficient electrocatalytic systems. The electrolyte can directly participate in reaction schemes (kinetics), electrode stability, and/or indirectly impacts the performance by influencing concentration overpotential (mass transport). This review aims to guide fine-tuning of the electrolyte properties, or electrolyte engineering, for (photo)electrochemical water splitting reactions.

Density-functional study of photoinduced water splitting

International Nuclear Information System (INIS)

Martínez Mesa, Aliezer; Rodríguez Hernández, Fermín; Seifert, Gotthard; Tranca, Diana

2015-01-01

We investigate the dynamics of water splitting on dye-sensitized metal (Ti, Cu) oxide surfaces, induced by direct sunlight excitation. In this study, we will consider the typical photoexcitation-followed-by-injection scheme, treating electron-injection and water splitting dynamics as independent events. The simultaneous modeling of the molecular motion and the quantum nonadiabatic transitions is achieved via the computation of the low-lying electronic states along several alternative reaction paths. Electronic structure calculations are based on a B3LYP-DFT Hamiltonian. The proposed approach combines an atomistic description of the reactants and of the immediate region of the surface, while the vibrational dynamics of the substrate is modeled as an effective bath leading to dissipation effects. The use of density-functional theory to solve the many- body electronic problem allows investigating the atomic motion of the water molecules and of a representative part of the substrate, thereby providing a theoretical and computational model capable to account simultaneously for the molecular character of the dye molecule and for the bulk properties of the surface. Furthermore, the insight emerging from this fundamental modeling can be used to optimize the chemical composition of the system to attain high incident-photon-flux-to-hydrogen-yield ratios. (full text)

Photoelectrochemical water splitting standards, experimental methods, and protocols

CERN Document Server

Chen, Zhebo; Miller, Eric

2014-01-01

This book outlines many of the techniques involved in materials development and characterization for photoelectrochemical (PEC) - for example, proper metrics for describing material performance, how to assemble testing cells and prepare materials for assessment of their properties, and how to perform the experimental measurements needed to achieve reliable results towards better scientific understanding. For each technique, proper procedure, benefits, limitations, and data interpretation are discussed. Consolidating this information in a short, accessible, and easy to read reference guide will allow researchers to more rapidly immerse themselves into PEC research and also better compare their results against those of other researchers to better advance materials development. This book serves as a "how-to" guide for researchers engaged in or interested in engaging in the field of photoelectrochemical (PEC) water splitting. PEC water splitting is a rapidly growing field of research in which the goal is to deve...

Experimental study of a thermochemical compressor for an absorption/compression hybrid cycle

International Nuclear Information System (INIS)

Ventas, R.; Vereda, C.; Lecuona, A.; Venegas, M.

2012-01-01

Highlights: ► Experimental study of a thermochemical compressor for absorption/compression cycle. ► Spray adiabatic absorber using NH 3 –LiNO 3 solution working fluid. ► It is able to operate between 57 and 110 °C varying concentration between 0.46 and 0.59. ► The increase of absorber pressure decreases the circulation ratio. ► The numerical model performed agrees with the experimental results. -- Abstract: An experimental study of a thermochemical compressor with ammonia–lithium nitrate solution as working fluid has been carried out. This compressor incorporates a single-pass adiabatic absorber and all the heat exchangers are of the plate type: absorber subcooler, generator and solution heat exchanger. The thermochemical compressor has been studied as part of a single-effect absorption chiller hybridized with an in-series low-pressure compression booster. The adiabatic absorber uses fog jet injectors. The generator hot water temperatures for the external driving flow are in the range of 57–110 °C and the absorber pressures range between 429 and 945 kPa. Experimental results are compared with a numerical model showing a high agreement. The performance of the thermochemical compressor, evaluated through the circulation ratio, improves for higher absorber pressures, indicating the potential of pressure boosting. For the same circulation ratio, the driving hot water inlet temperature decreases with the rise of the absorber pressure. The thermochemical compressor, based on an adiabatic absorber, can produce refrigerant with very low driving temperatures, between 57 and 70 °C, what is interesting for solar cooling applications and very low temperature residual heat recovery. Efficiencies and cooling power are offered when this hybrid thermochemical compressor is implemented in a chiller, showing the effect of different operating parameters.

Towards Versatile and Sustainable Hydrogen Production through Electrocatalytic Water Splitting: Electrolyte Engineering.

Science.gov (United States)

Shinagawa, Tatsuya; Takanabe, Kazuhiro

2017-04-10

Recent advances in power generation from renewable resources necessitate conversion of electricity to chemicals and fuels in an efficient manner. Electrocatalytic water splitting is one of the most powerful and widespread technologies. The development of highly efficient, inexpensive, flexible, and versatile water electrolysis devices is desired. This review discusses the significance and impact of the electrolyte on electrocatalytic performance. Depending on the circumstances under which the water splitting reaction is conducted, the required solution conditions, such as the identity and molarity of ions, may significantly differ. Quantitative understanding of such electrolyte properties on electrolysis performance is effective to facilitate the development of efficient electrocatalytic systems. The electrolyte can directly participate in reaction schemes (kinetics), affect electrode stability, and/or indirectly impact the performance by influencing the concentration overpotential (mass transport). This review aims to guide fine-tuning of the electrolyte properties, or electrolyte engineering, for (photo)electrochemical water splitting reactions. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Effects of inorganic substances on water splitting in ion-exchange membranes; II. Optimal contents of inorganic substances in preparing bipolar membranes.

Science.gov (United States)

Kang, Moon-Sung; Choi, Yong-Jin; Moon, Seung-Hyeon

2004-05-15

An approach to enhancing the water-splitting performance of bipolar membranes (BPMs) is introducing an inorganic substance at the bipolar (BP) junction. In this study, the immobilization of inorganic matters (i.e., iron hydroxides and silicon compounds) at the BP junction and the optimum concentration have been investigated. To immobilize these inorganic matters, novel methods (i.e., electrodeposition of the iron hydroxide and processing of the sol-gel to introduce silicon groups at the BP junction) were suggested. At optimal concentrations, the immobilized inorganic matters significantly enhanced the water-splitting fluxes, indicating that they provide alternative paths for water dissociation, but on the other hand possibly reduce the polarization of water molecules between the sulfonic acid and quaternary ammonium groups at high contents. Consequently, the amount of inorganic substances introduced should be optimized to obtain the maximum water splitting in the BPM.

Solar processing of CO2 and H2O, routes for solar fuels

International Nuclear Information System (INIS)

Flammant, G.; Abanades, St.

2008-01-01

Complete text of publication follows: Concentrated solar energy provides heat in the temperature range 200 C - 3000 C for concentration ratio variation from 10 to 10 000 (three orders of magnitude). Consequently, solar-driven thermochemical processes may be proposed to produce hydrogen from water decomposition and to reduce carbon dioxide. This lecture gives an overview of such processes. High temperature thermochemical cycles for hydrogen production by water splitting are currently studied at PROMES lab, particularly 2-step and 3-step cycles based on the following reaction scheme, MOox → MOred + 1/2 O 2 (high temperature solar step), MOred + H 2 O → MOox + H 2 (low temperature non solar step). Volatile and non-volatile oxide cycles are developed from the chemical and the engineering points of view. A similar reaction scheme may be proposed to reduce carbon dioxide with concentrated solar energy (Fig. 1), it comes, MOox → MOred + 1/2 O 2 (high temperature solar step), MOred + CO 2 → MOox + CO (low temperature non solar step). As a result gas mixtures such as CO 2 /H 2 and CO/H 2 may be produced by solar energy. Such mixtures are the reactants for liquid fuels production (solar fuels)

Flow splitting in numerical simulations of oceanic dense-water outflows

Science.gov (United States)

Marques, Gustavo M.; Wells, Mathew G.; Padman, Laurie; Özgökmen, Tamay M.

2017-05-01

Flow splitting occurs when part of a gravity current becomes neutrally buoyant and separates from the bottom-trapped plume as an interflow. This phenomenon has been previously observed in laboratory experiments, small-scale water bodies (e.g., lakes) and numerical studies of small-scale systems. Here, the potential for flow splitting in oceanic gravity currents is investigated using high-resolution (Δx = Δz = 5 m) two-dimensional numerical simulations of gravity flows into linearly stratified environments. The model is configured to solve the non-hydrostatic Boussinesq equations without rotation. A set of experiments is conducted by varying the initial buoyancy number B0 =Q0N3 /g‧2 (where Q0 is the volume flux of the dense water flow per unit width, N is the ambient stratification and g‧ is the reduced gravity), the bottom slope (α) and the turbulent Prandtl number (Pr). Regardless of α or Pr, when B0 ≤ 0.002 the outflow always reaches the deep ocean forming an underflow. Similarly, when B0 ≥ 0.13 the outflow always equilibrates at intermediate depths, forming an interflow. However, when B0 ∼ 0.016, flow splitting always occurs when Pr ≥ 10, while interflows always occur for Pr = 1. An important characteristic of simulations that result in flow splitting is the development of Holmboe-like interfacial instabilities and flow transition from a supercritical condition, where the Froude number (Fr) is greater than one, to a slower and more uniform subcritical condition (Fr internal hydraulic jump and consequent mixing enhancement. Although our experiments do not take into account three-dimensionality and rotation, which are likely to influence mixing and the transition between flow regimes, a comparison between our results and oceanic observations suggests that flow splitting may occur in dense-water outflows with weak ambient stratification, such as Antarctic outflows.

Photoelectrochemical water splitting in separate oxygen and hydrogen cells

Science.gov (United States)

Landman, Avigail; Dotan, Hen; Shter, Gennady E.; Wullenkord, Michael; Houaijia, Anis; Maljusch, Artjom; Grader, Gideon S.; Rothschild, Avner

2017-06-01

Solar water splitting provides a promising path for sustainable hydrogen production and solar energy storage. One of the greatest challenges towards large-scale utilization of this technology is reducing the hydrogen production cost. The conventional electrolyser architecture, where hydrogen and oxygen are co-produced in the same cell, gives rise to critical challenges in photoelectrochemical water splitting cells that directly convert solar energy and water to hydrogen. Here we overcome these challenges by separating the hydrogen and oxygen cells. The ion exchange in our cells is mediated by auxiliary electrodes, and the cells are connected to each other only by metal wires, enabling centralized hydrogen production. We demonstrate hydrogen generation in separate cells with solar-to-hydrogen conversion efficiency of 7.5%, which can readily surpass 10% using standard commercial components. A basic cost comparison shows that our approach is competitive with conventional photoelectrochemical systems, enabling safe and potentially affordable solar hydrogen production.

Analysis of sulfur-iodine thermochemical cycle for solar hydrogen production. Part 1: decomposition of sulfuric acid

Energy Technology Data Exchange (ETDEWEB)

Huang, Cunping; T-Raissi, Ali [Central Florida Univ., Florida Solar Energy Center, Cocoa, FL (United States)

2005-05-01

The sulfur-iodine (S-I) thermochemical water splitting cycle is one of the most studied cycles for hydrogen (H{sub 2}) production. S-I cycle consists of four sections: (I) acid production and separation and oxygen purification, (II) sulfuric acid concentration and decomposition, (III) hydroiodic acid (HI) concentration, and (IV) HI decomposition and H{sub 2} purification. Section II of the cycle is an endothermic reaction driven by the heat input from a high temperature source. Analysis of the S-I cycle in the past thirty years have been focused mostly on the utilization of nuclear power as the high temperature heat source for the sulfuric acid decomposition step. Thermodynamic as well as kinetic considerations indicate that both the extent and rate of sulfuric acid decomposition can be improved at very high temperatures (in excess of 1000 deg C) available only from solar concentrators. The beneficial effect of high temperature solar heat for decomposition of sulfuric acid in the S-I cycle is described in this paper. We used Aspen Technologies' HYSYS chemical process simulator (CPS) to develop flowsheets for sulfuric acid (H{sub 2}SO{sub 4}) decomposition that include all mass and heat balances. Based on the HYSYS analyses, two new process flowsheets were developed. These new sulfuric acid decomposition processes are simpler and more stable than previous processes and yield higher conversion efficiencies for the sulfuric acid decomposition and sulfur dioxide and oxygen formation. (Author)

Review of the direct thermochemical conversion of lignocellulosic biomass for liquid fuels

Directory of Open Access Journals (Sweden)

Jianchun JIANG,Junming XU,Zhanqian SONG

2015-03-01

Full Text Available Increased demand for liquid transportation fuels, environmental concerns and depletion of petroleum resources requires the development of efficient conversion technologies for production of second-generation biofuels from non-food resources. Thermochemical approaches hold great potential for conversion of lignocellulosic biomass into liquid fuels. Direct thermochemical processes convert biomass into liquid fuels in one step using heat and catalysts and have many advantages over indirect and biological processes, such as greater feedstock flexibility, integrated conversion of whole biomass, and lower operation costs. Several direct thermochemical processes are employed in the production of liquid biofuels depending on the nature of the feedstock properties: such as fast pyrolysis/liquefaction of lignocellulosic biomass for bio-oil, including upgrading methods, such as catalytic cracking and hydrogenation. Owing to the substantial amount of liquid fuels consumed by vehicular transport, converting biomass into drop-in liquid fuels may reduce the dependence of the fuel market on petroleum-based fuel products. In this review, we also summarize recent progress in technologies for large-scale equipment for direct thermochemical conversion. We focus on the technical aspects critical to commercialization of the technologies for production of liquid fuels from biomass, including feedstock type, cracking catalysts, catalytic cracking mechanisms, catalytic reactors, and biofuel properties. We also discuss future prospects for direct thermochemical conversion in biorefineries for the production of high grade biofuels.

Thermochemical cycles based on metal oxides for solar hydrogen production; Ciclos termoquimicos basados en oxidos metalicos para produccion de hidrogeno solar

Energy Technology Data Exchange (ETDEWEB)

Fernandez Saavedra, R.; Quejido Cabezas, J.

2012-11-01

The growing demand for energy requires the development and optimization of alternative energy sources. One of the options currently being investigated is solar hydrogen production with thermochemical cycles. This process involves the use of concentrated solar radiation as an energy source to dissociate water through a series of endothermic and exothermic chemical reactions, for the purpose of obtaining hydrogen on a sustainable basis. Of all the thermochemical cycles that have been evaluated, the most suitable ones for implementation with solar energy are those based on metal oxides. (Author) 20 refs.

Strategies for stable water splitting via protected photoelectrodes

DEFF Research Database (Denmark)

Bae, Dowon; Seger, Brian; Vesborg, Peter Christian Kjærgaard

2017-01-01

Photoelectrochemical (PEC) solar-fuel conversion is a promising approach to provide clean and storable fuel (e.g., hydrogen and methanol) directly from sunlight, water and CO2. However, major challenges still have to be overcome before commercialization can be achieved. One of the largest barriers...... photocathodes. In addition, we review protection layer approaches and their stabilities for a wide variety of experimental photoelectrodes for water reduction. Finally, we discuss key aspects which should be addressed in continued work on realizing stable and practical PEC solar water splitting systems....

Recent developments in solar H 2 generation from water splitting

Indian Academy of Sciences (India)

Hydrogen production from water and sunlight through photocatalysis could become one of the channels, in the not-so-distant future, to meet a part of ever growing energy demands. However, accomplishing solar water splitting through semiconductor particulate photocatalysis seems to be the 'Holy Grail' problem of science.

Enhanced Electrocatalytic Activity for Water Splitting on NiO/Ni/Carbon Fiber Paper

Directory of Open Access Journals (Sweden)

Ruoyu Zhang

2016-12-01

Full Text Available Large-scale growth of low-cost, efficient, and durable non-noble metal-based electrocatalysts for water splitting is crucial for future renewable energy systems. Atomic layer deposition (ALD provides a promising route for depositing uniform thin coatings of electrocatalysts, which are useful in many technologies, including the splitting of water. In this communication, we report the growth of a NiO/Ni catalyst directly on carbon fiber paper by atomic layer deposition and report subsequent reduction and oxidation annealing treatments. The 10–20 nm NiO/Ni nanoparticle catalysts can reach a current density of 10 mA·cm−2 at an overpotential of 189 mV for hydrogen evolution reactions and 257 mV for oxygen evolution reactions with high stability. We further successfully achieved a water splitting current density of 10 mA·cm−2 at 1.78 V using a typical NiO/Ni coated carbon fiber paper two-electrode setup. The results suggest that nanoparticulate NiO/Ni is an active, stable, and noble-metal-free electrocatalyst, which facilitates a method for future water splitting applications.

Light Modulation and Water Splitting Enhancement Using a Composite Porous GaN Structure.

Science.gov (United States)

Yang, Chao; Xi, Xin; Yu, Zhiguo; Cao, Haicheng; Li, Jing; Lin, Shan; Ma, Zhanhong; Zhao, Lixia

2018-02-14

On the basis of the laterally porous GaN, we designed and fabricated a composite porous GaN structure with both well-ordered lateral and vertical holes. Compared to the plane GaN, the composite porous GaN structure with the combination of the vertical holes can help to reduce UV reflectance and increase the saturation photocurrent during water splitting by a factor of ∼4.5. Furthermore, we investigated the underlying mechanism for the enhancement of the water splitting performance using a finite-difference time-domain method. The results show that the well-ordered vertical holes can not only help to open the embedded pore channels to the electrolyte at both sides and reduce the migration distance of the gas bubbles during the water splitting reactions but also help to modulate the light field. Using this composite porous GaN structure, most of the incident light can be modulated and trapped into the nanoholes, and thus the electric fields localized in the lateral pores can increase dramatically as a result of the strong optical coupling. Our findings pave a new way to develop GaN photoelectrodes for highly efficient solar water splitting.

A Procedure for Splitting Processes and its Application to Coordination (Technical Report)

NARCIS (Netherlands)

S.-S.T.Q. Jongmans (Sung-Shik); D.G. Clarke (David); J.M.P. Proença (Jose)

2012-01-01

textabstractWe present a procedure for splitting processes in a process algebra with multi-actions (a subset of the specification language mCRL2). This splitting procedure cuts a process into two processes along a set of actions A: roughly, one of these processes contains no actions from A, while

Ir4+-Doped NiFe LDH to expedite hydrogen evolution kinetics as a Pt-like electrocatalyst for water splitting.

Science.gov (United States)

Chen, Qian-Qian; Hou, Chun-Chao; Wang, Chuan-Jun; Yang, Xiao; Shi, Rui; Chen, Yong

2018-06-06

NiFe-layered double hydroxide (NiFe LDH) is a state-of-the-art oxygen evolution reaction (OER) electrocatalyst, yet it suffers from rather poor catalytic activity for the hydrogen evolution reaction (HER) due to its extremely sluggish water dissociation kinetics, severely restricting its application in overall water splitting. Herein, we report a novel strategy to expedite the HER kinetics of NiFe LDH by an Ir4+-doping strategy to accelerate the water dissociation process (Volmer step), and thus this catalyst exhibits superior and robust catalytic activity for finally oriented overall water splitting in 1 M KOH requiring only a low initial voltage of 1.41 V delivering at 20 mA cm-2 for more than 50 h.

Quantitative Thermochemical Measurements in High-Pressure Gaseous Combustion

Science.gov (United States)

Kojima, Jun J.; Fischer, David G.

2012-01-01

We present our strategic experiment and thermochemical analyses on combustion flow using a subframe burst gating (SBG) Raman spectroscopy. This unconventional laser diagnostic technique has promising ability to enhance accuracy of the quantitative scalar measurements in a point-wise single-shot fashion. In the presentation, we briefly describe an experimental methodology that generates transferable calibration standard for the routine implementation of the diagnostics in hydrocarbon flames. The diagnostic technology was applied to simultaneous measurements of temperature and chemical species in a swirl-stabilized turbulent flame with gaseous methane fuel at elevated pressure (17 atm). Statistical analyses of the space-/time-resolved thermochemical data provide insights into the nature of the mixing process and it impact on the subsequent combustion process in the model combustor.

Efficient solar-to-fuels production from a hybrid microbial-water-splitting catalyst system.

Science.gov (United States)

Torella, Joseph P; Gagliardi, Christopher J; Chen, Janice S; Bediako, D Kwabena; Colón, Brendan; Way, Jeffery C; Silver, Pamela A; Nocera, Daniel G

2015-02-24

Photovoltaic cells have considerable potential to satisfy future renewable-energy needs, but efficient and scalable methods of storing the intermittent electricity they produce are required for the large-scale implementation of solar energy. Current solar-to-fuels storage cycles based on water splitting produce hydrogen and oxygen, which are attractive fuels in principle but confront practical limitations from the current energy infrastructure that is based on liquid fuels. In this work, we report the development of a scalable, integrated bioelectrochemical system in which the bacterium Ralstonia eutropha is used to efficiently convert CO2, along with H2 and O2 produced from water splitting, into biomass and fusel alcohols. Water-splitting catalysis was performed using catalysts that are made of earth-abundant metals and enable low overpotential water splitting. In this integrated setup, equivalent solar-to-biomass yields of up to 3.2% of the thermodynamic maximum exceed that of most terrestrial plants. Moreover, engineering of R. eutropha enabled production of the fusel alcohol isopropanol at up to 216 mg/L, the highest bioelectrochemical fuel yield yet reported by >300%. This work demonstrates that catalysts of biotic and abiotic origin can be interfaced to achieve challenging chemical energy-to-fuels transformations.

Efficient solar-to-fuels production from a hybrid microbial–water-splitting catalyst system

Science.gov (United States)

Torella, Joseph P.; Gagliardi, Christopher J.; Chen, Janice S.; Bediako, D. Kwabena; Colón, Brendan; Way, Jeffery C.; Silver, Pamela A.; Nocera, Daniel G.

2015-01-01

Photovoltaic cells have considerable potential to satisfy future renewable-energy needs, but efficient and scalable methods of storing the intermittent electricity they produce are required for the large-scale implementation of solar energy. Current solar-to-fuels storage cycles based on water splitting produce hydrogen and oxygen, which are attractive fuels in principle but confront practical limitations from the current energy infrastructure that is based on liquid fuels. In this work, we report the development of a scalable, integrated bioelectrochemical system in which the bacterium Ralstonia eutropha is used to efficiently convert CO2, along with H2 and O2 produced from water splitting, into biomass and fusel alcohols. Water-splitting catalysis was performed using catalysts that are made of earth-abundant metals and enable low overpotential water splitting. In this integrated setup, equivalent solar-to-biomass yields of up to 3.2% of the thermodynamic maximum exceed that of most terrestrial plants. Moreover, engineering of R. eutropha enabled production of the fusel alcohol isopropanol at up to 216 mg/L, the highest bioelectrochemical fuel yield yet reported by >300%. This work demonstrates that catalysts of biotic and abiotic origin can be interfaced to achieve challenging chemical energy-to-fuels transformations. PMID:25675518

Colloidal nanocrystals for photoelectrochemical and photocatalytic water splitting

Science.gov (United States)

Gadiyar, Chethana; Loiudice, Anna; Buonsanti, Raffaella

2017-02-01

Colloidal nanocrystals (NCs) are among the most modular and versatile nanomaterial platforms for studying emerging phenomena in different fields thanks to their superb compositional and morphological tunability. A promising, yet challenging, application involves the use of colloidal NCs as light absorbers and electrocatalysts for water splitting. In this review we discuss how the tunability of these materials is ideal to understand the complex phenomena behind storing energy in chemical bonds and to optimize performance through structural and compositional modification. First, we describe the colloidal synthesis method as a means to achieve a high degree of control over single material NCs and NC heterostructures, including examples of the role of the ligands in modulating size and shape. Next, we focus on the use of NCs as light absorbers and catalysts to drive both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), together with some of the challenges related to the use of colloidal NCs as model systems and/or technological solution in water splitting. We conclude with a broader prospective on the use of colloidal chemistry for new material discovery.

Plasma-Assisted Synthesis of NiCoP for Efficient Overall Water Splitting

KAUST Repository

Liang, Hanfeng

2016-11-09

Efficient water splitting requires highly active, earth-abundant, and robust catalysts. Monometallic phosphides such as NiP have been shown to be active toward water splitting. Our theoretical analysis has suggested that their performance can be further enhanced by substitution with extrinsic metals, though very little work has been conducted in this area. Here we present for the first time a novel PH plasma-assisted approach to convert NiCo hydroxides into ternary NiCoP. The obtained NiCoP nanostructure supported on Ni foam shows superior catalytic activity toward the hydrogen evolution reaction (HER) with a low overpotential of 32 mV at 10 mA cm in alkaline media. Moreover, it is also capable of catalyzing the oxygen evolution reaction (OER) with high efficiency though the real active sites are surface oxides in situ formed during the catalysis. Specifically, a current density of 10 mA cm is achieved at overpotential of 280 mV. These overpotentials are among the best reported values for non-noble metal catalysts. Most importantly, when used as both the cathode and anode for overall water splitting, a current density of 10 mA cm is achieved at a cell voltage as low as 1.58 V, making NiCoP among the most efficient earth-abundant catalysts for water splitting. Moreover, our new synthetic approach can serve as a versatile route to synthesize various bimetallic or even more complex phosphides for various applications.

Visible-light driven nitrogen-doped petal-morphological ceria nanosheets for water splitting

Science.gov (United States)

Qian, Junchao; Zhang, Wenya; Wang, Yaping; Chen, Zhigang; Chen, Feng; Liu, Chengbao; Lu, Xiaowang; Li, Ping; Wang, Kaiyuan; Chen, Ailian

2018-06-01

Water splitting is a promising sustainable technology for solar-to-chemical energy conversion. Herein, we successfully fabricated nitrogen-doped ultrathin CeO2 nanosheets by using field poppy petals as templates, which exhibit an efficiently catalytic activity for water splitting. Abundant oxygen vacancies and substitutional N atoms were experimentally observed in the film due to its unique biomorphic texture. In view of high efficiency and long durability of the as-prepared photocatalyst, this biotemplate method may provide an alternative technique for using biomolecules to assemble 2D nanomaterials.

Thermochemical nitrate reduction

International Nuclear Information System (INIS)

Cox, J.L.; Lilga, M.A.; Hallen, R.T.

1992-09-01

A series of preliminary experiments was conducted directed at thermochemically converting nitrate to nitrogen and water. Nitrates are a major constituent of the waste stored in the underground tanks on the Hanford Site, and the characteristics and effects of nitrate compounds on stabilization techniques must be considered before permanent disposal operations begin. For the thermochemical reduction experiments, six reducing agents (ammonia, formate, urea, glucose, methane, and hydrogen) were mixed separately with ∼3 wt% NO 3 - solutions in a buffered aqueous solution at high pH (13); ammonia and formate were also mixed at low pH (4). Reactions were conducted in an aqueous solution in a batch reactor at temperatures of 200 degrees C to 350 degrees C and pressures of 600 to 2800 psig. Both gas and liquid samples were analyzed. The specific components analyzed were nitrate, nitrite, nitrous oxide, nitrogen, and ammonia. Results of experimental runs showed the following order of nitrate reduction of the six reducing agents in basic solution: formate > glucose > urea > hydrogen > ammonia ∼ methane. Airnmonia was more effective under acidic conditions than basic conditions. Formate was also effective under acidic conditions. A more thorough, fundamental study appears warranted to provide additional data on the mechanism of nitrate reduction. Furthermore, an expanded data base and engineering feasibility study could be used to evaluate conversion conditions for promising reducing agents in more detail and identify new reducing agents with improved performance characteristics

Dye-Sensitized Photocatalytic Water Splitting and Sacrificial Hydrogen Generation: Current Status and Future Prospects

Directory of Open Access Journals (Sweden)

Pankaj Chowdhury

2017-05-01

Full Text Available Today, global warming and green energy are important topics of discussion for every intellectual gathering all over the world. The only sustainable solution to these problems is the use of solar energy and storing it as hydrogen fuel. Photocatalytic and photo-electrochemical water splitting and sacrificial hydrogen generation show a promise for future energy generation from renewable water and sunlight. This article mainly reviews the current research progress on photocatalytic and photo-electrochemical systems focusing on dye-sensitized overall water splitting and sacrificial hydrogen generation. An overview of significant parameters including dyes, sacrificial agents, modified photocatalysts and co-catalysts are provided. Also, the significance of statistical analysis as an effective tool for a systematic investigation of the effects of different factors and their interactions are explained. Finally, different photocatalytic reactor configurations that are currently in use for water splitting application in laboratory and large scale are discussed.

A Study on the Performance of the Split Reaction Water Turbine with Guide Ribs

Science.gov (United States)

Allen, Deuel H.; Villanueva, Eliseo P.

2015-09-01

The development of technologies that make use of renewable energy is of great significance presently. A new kind of turbine called Split Reaction Water Turbine (SRWT) using PVC pipes as material is a major contribution towards harnessing the energy potentials of small stream low head water resources. SRWTs of diameter to height ratio (D/H = 110 cm/160 cm) were tested at the MSU-IIT College of Engineering Fluid Engineering Laboratory. Data on volumetric flow and pressure head at the turbine inlet of the SRWT were recorded using National Instrument Data Processing System using LabView software. In later experiments, guide ribs were installed at the vane of the exit nozzles in order to determine the difference in the performance of the ribbed and the non-ribbed SRWT. Simulations of the running SRWT were conducted using SOLIDWORKS software. Results of the simulations aided in the thorough analyses of the data from the experimental runs. A comparison of data from the ribbed and non-ribbed SRWT shows that guide ribs were effective in directing the momentum of the exiting water to improve the speed of rotation. In this study, the increase in the speed of the Split Reaction Water Turbine was as much as 46%.

US work on technical and economic aspects of electrolytic, thermochemical, and hybrid processes for hydrogen production at temperatures below 550 deg. C

International Nuclear Information System (INIS)

Petri, M.C.; Yyldyz, B.; Klickman, A.E.

2006-01-01

Hydrogen demand is increasing, but there are few options for affordable hydrogen production free of greenhouse gas emissions. Nuclear power is one of the most promising options. Most research is focused on high-temperature electrolytic and thermochemical processes for nuclear-generated hydrogen, but it will be many years before very high temperature reactors become commercially available. For light water reactors or supercritical reactors, low-temperature water electrolysis is a currently available technology for hydrogen production. Higher efficiencies may be gained through thermo-electrochemical hydrogen production cycles, but there are only a limited number that have heat requirements consistent with the lower temperatures of light-water reactor technology. Indeed, active research is ongoing for only three such cycles in the USA. Reductions in electricity and system costs would be needed (or the imposition of a carbon tax) for low-temperature water electrolysis to compete with today's costs for steam methane reformation. The interactions between hydrogen and electricity markets and hydrogen and electricity producers are complex and will evolve as the markets evolve. (author)

Polarized triple-collinear splitting functions at NLO for processes with photons

International Nuclear Information System (INIS)

Sborlini, Germán F.R.; Florian, Daniel de; Rodrigo, Germán

2015-01-01

We compute the polarized splitting functions in the triple collinear limit at next-to-leading order accuracy (NLO) in the strong coupling α_S, for the splitting processes γ→qq-barγ, γ→qq-barg and g→qq-barγ. The divergent structure of each splitting function was compared to the predicted behaviour according to Catani’s formula. The results obtained in this paper are compatible with the unpolarized splitting functions computed in a previous article. Explicit results for NLO corrections are presented in the context of conventional dimensional regularization (CDR).

Polarized triple-collinear splitting functions at NLO for processes with photons

Energy Technology Data Exchange (ETDEWEB)

Sborlini, Germán F.R. [Departamento de Física and IFIBA, FCEyN, Universidad de Buenos Aires (1428) Pabellón 1 Ciudad Universitaria, Capital Federal (Argentina); Instituto de Física Corpuscular, Universitat de València,Consejo Superior de Investigaciones Científicas,Parc Científic, E-46980 Paterna, Valencia (Spain); Florian, Daniel de [Departamento de Física and IFIBA, FCEyN, Universidad de Buenos Aires (1428) Pabellón 1 Ciudad Universitaria, Capital Federal (Argentina); Rodrigo, Germán [Instituto de Física Corpuscular, Universitat de València,Consejo Superior de Investigaciones Científicas,Parc Científic, E-46980 Paterna, Valencia (Spain)

2015-03-04

We compute the polarized splitting functions in the triple collinear limit at next-to-leading order accuracy (NLO) in the strong coupling α{sub S}, for the splitting processes γ→qq-barγ, γ→qq-barg and g→qq-barγ. The divergent structure of each splitting function was compared to the predicted behaviour according to Catani’s formula. The results obtained in this paper are compatible with the unpolarized splitting functions computed in a previous article. Explicit results for NLO corrections are presented in the context of conventional dimensional regularization (CDR).

10-fold enhancement in light-driven water splitting using niobium oxynitride microcone array films

KAUST Repository

Shaheen, Basamat

2016-03-26

We demonstrate, for the first time, the synthesis of highly ordered niobium oxynitride microcones as an attractive class of materials for visible-light-driven water splitting. As revealed by the ultraviolet photoelectron spectroscopy (UPS), photoelectrochemical and transient photocurrent measurements, the microcones showed enhanced performance (~1000% compared to mesoporous niobium oxide) as photoanodes for water splitting with remarkable stability and visible light activity. © 2016 Elsevier B.V. All rights reserved.

Toward visible light response: Overall water splitting using heterogeneous photocatalysts

KAUST Repository

Takanabe, Kazuhiro; Domen, Kazunari

2011-01-01

Extensive energy conversion of solar energy can only be achieved by large-scale collection of solar flux. The technology that satisfies this requirement must be as simple as possible to reduce capital cost. Overall water splitting by powder

Transferring Knowledge of Electrocatalysis to Photocatalysis: Photocatalytic Water Splitting

KAUST Repository

Takanabe, Kazuhiro

2017-06-24

One of the most attractive features of photocatalytic reactions is the ability to achieve energetically uphill (photosynthetic) reactions. In many photocatalytic reactions, the reactions involve multielectron transfers with the adsorbed intermediates. In this case, photocatalysis is nothing but electrocatalysis initiated and driven by the electron potential shift caused by the photocatalyst (photon absorber). This condition is indeed true for photocatalysts for water splitting, which are also electrocatalysts because both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) require multiple electron transfers at the active surfaces. This chapter deals with the product-side in the six-gear concept. It shows the electrocatalytic performance when using an electrocatalyst on the surface. The chapter further shows the current-potential curve for an electrocatalytic process isolated from the photocatalyst process. For an electrocatalyst to achieve electrochemical reactions, the potential of the catalyst must be shifted at the interface of the semiconductor, providing electromotive force or overpotential for redox reactions.

Transferring Knowledge of Electrocatalysis to Photocatalysis: Photocatalytic Water Splitting

KAUST Repository

Takanabe, Kazuhiro

2017-01-01

One of the most attractive features of photocatalytic reactions is the ability to achieve energetically uphill (photosynthetic) reactions. In many photocatalytic reactions, the reactions involve multielectron transfers with the adsorbed intermediates. In this case, photocatalysis is nothing but electrocatalysis initiated and driven by the electron potential shift caused by the photocatalyst (photon absorber). This condition is indeed true for photocatalysts for water splitting, which are also electrocatalysts because both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) require multiple electron transfers at the active surfaces. This chapter deals with the product-side in the six-gear concept. It shows the electrocatalytic performance when using an electrocatalyst on the surface. The chapter further shows the current-potential curve for an electrocatalytic process isolated from the photocatalyst process. For an electrocatalyst to achieve electrochemical reactions, the potential of the catalyst must be shifted at the interface of the semiconductor, providing electromotive force or overpotential for redox reactions.

Redox Kinetics and Nonstoichiometry of Ce0.5Zr0.5O2−δ for Water Splitting and Hydrogen Production

KAUST Repository

Zhao, Zhenlong

2017-04-25

Water splitting and chemical fuel production as a promising carbon-neutral energy solution relies critically on an efficient electrochemical process over catalyst surfaces. The fundamentals within the surface redox pathways, including the complex interactions of mobile ions and electrons between the bulk and the surface, along with the role of adsorbates and electrostatic fields remain yet to be understood quantitatively. This work presents a detailed kinetics study and nonstoichiometry characterization of Ce0.5Zr0.5O2−δ (CZO), one of the most recognized catalysts for water splitting. The use of CZO leads to >60% improvement in the kinetic rates as compared with undoped ceria with twice the total yield at 700 °C, resulting from the improved reducibility. The peak H2 production rate is 95 μmol g–1 s–1 at 700 °C, and the total production is 750 μmol g–1. A threshold temperature of 650 °C is required to achieve significant H2 production at fast rates. The redox kinetics is modeled using two-step surface chemistry with bulk-to-surface transport equilibrium. Kinetics and equilibrium parameters are extracted, and the model predictions show good agreement with the measurements. The enthalpy of bulk defect formation for CZO is found to be 262 kJ/mol, >40% lower than that of undoped ceria. As oxygen vacancy is gradually filled up, the surface H2O splitting chemistry undergoes a transition from exothermic to endothermic, with the crossover around δ = 0.04 to 0.05, which constrains the further ion incorporation process. Our kinetics study reveals that the H2O splitting process with CZO is kinetics limited at low temperature and transitions to partial-equilibrium with significantly enhanced backward reaction at high temperature. The charge-transfer step is found to be the rate-limiting step for H2O splitting. The detailed kinetics and nonstoichiometric equilibria should be helpful in guiding the design and optimization of CZO as a catalyst, oxygen storage

Modeling and Simulation of the Sulfur-Iodine Process Coupled to a Very High-Temperature Gas-Cooled Nuclear Reactor

International Nuclear Information System (INIS)

Shin, Youngjoon; Lee, Taehoon; Lee, Kiyoung; Kim, Minhwan

2015-01-01

Hydrogen produced from water using nuclear energy will avoid both the use of fossil fuel and CO 2 emission presumed to be the dominant reason for global warming. A thermo-chemical sulfur-iodine (SI) process coupled to a Very High Temperature Gas-Cooled Reactor(VHTR) is one of the most prospective hydrogen production methods that split water using nuclear energy because the SI process is suitable for large-scale hydrogen production without CO 2 emission. The dynamic simulation code to evaluate the start-up behavior of the chemical reactors placed on the secondary helium loop of the SI process has been developed and partially verified using the steady state values obtained from the Aspen Plus TM Code simulation. As the start-up dynamic simulation results of the SI process coupled to the IHX, which is one of components in the VHTR system, it is expected that the integrated secondary helium loop of the SI process can be successfully and safely approach the steady state condition

Nanosized TiO[subscript 2] for Photocatalytic Water Splitting Studied by Oxygen Sensor and Data Logger

Science.gov (United States)

Zhang, Ruinan; Liu, Song; Yuan, Hongyan; Xiao, Dan; Choi, Martin M. F.

2012-01-01

Photocatalytic water splitting by semiconductor photocatalysts has attracted considerable attention in the past few decades. In this experiment, nanosized titanium dioxide (nano-TiO[subscript 2]) particles are used to photocatalytically split water, which is then monitored by an oxygen sensor. Sacrificial reagents such as organics (EDTA) and metal…

Triple junction polymer solar cells for photoelectrochemical water splitting

NARCIS (Netherlands)

Esiner, S.; Eersel, van H.; Wienk, M.M.; Janssen, R.A.J.

2013-01-01

A triple junction polymer solar cell in a novel 1 + 2 type configuration provides photoelectrochemical water splitting in its maximum power point at V ˜ 1.70 V with an estimated solar to hydrogen energy conversion efficiency of 3.1%. The triple junction cell consists of a wide bandgap front cell and

ENERGY EFFICIENCY LIMITS FOR A RECUPERATIVE BAYONET SULFURIC ACID DECOMPOSITION REACTOR FOR SULFUR CYCLE THERMOCHEMICAL HYDROGEN PRODUCTION

Energy Technology Data Exchange (ETDEWEB)

Gorensek, M.; Edwards, T.

2009-06-11

A recuperative bayonet reactor design for the high-temperature sulfuric acid decomposition step in sulfur-based thermochemical hydrogen cycles was evaluated using pinch analysis in conjunction with statistical methods. The objective was to establish the minimum energy requirement. Taking hydrogen production via alkaline electrolysis with nuclear power as the benchmark, the acid decomposition step can consume no more than 450 kJ/mol SO{sub 2} for sulfur cycles to be competitive. The lowest value of the minimum heating target, 320.9 kJ/mol SO{sub 2}, was found at the highest pressure (90 bar) and peak process temperature (900 C) considered, and at a feed concentration of 42.5 mol% H{sub 2}SO{sub 4}. This should be low enough for a practical water-splitting process, even including the additional energy required to concentrate the acid feed. Lower temperatures consistently gave higher minimum heating targets. The lowest peak process temperature that could meet the 450-kJ/mol SO{sub 2} benchmark was 750 C. If the decomposition reactor were to be heated indirectly by an advanced gas-cooled reactor heat source (50 C temperature difference between primary and secondary coolants, 25 C minimum temperature difference between the secondary coolant and the process), then sulfur cycles using this concept could be competitive with alkaline electrolysis provided the primary heat source temperature is at least 825 C. The bayonet design will not be practical if the (primary heat source) reactor outlet temperature is below 825 C.

Thermochemical biorefinery based on dimethyl ether as intermediate: Technoeconomic assessment

International Nuclear Information System (INIS)

Haro, P.; Ollero, P.; Villanueva Perales, A.L.; Gómez-Barea, A.

2013-01-01

Highlights: ► A thermochemical biorefinery based on bio-DME as intermediate is studied. ► The assessed concepts (12) lead to multi-product generation (polygeneration). ► In all concepts DME is converted by carbonylation or hydrocarbonylation. ► Rates of return are similar to or higher than plants producing a single product. -- Abstract: Thermochemical biorefinery based on dimethyl ether (DME) as an intermediate is studied. DME is converted into methyl acetate, which can either be hydrogenated to ethanol or sold as a co-product. Considering this option together with a variety of technologies for syngas upgrading, 12 different process concepts are analyzed. The considered products are ethanol, methyl acetate, H 2 , DME and electricity. The assessment of each alternative includes biomass pretreatment, gasification, syngas clean-up and conditioning, DME synthesis and conversion, product separation, and heat and power integration. A plant size of 500 MW th processing poplar chips is taken as a basis. The resulting energy efficiency to products ranges from 34.9% to 50.2%. The largest internal rate of return (28.74%) corresponds to a concept which produces methyl acetate, DME and electricity (exported to grid). A sensitivity analysis with respect to total plant investment (TPI), total operation costs (TOC) and market price of products was carried out. The overall conclusion is that, despite its greater complexity, this kind of thermochemical biorefinery is more profitable than thermochemical bioprocesses oriented to a single product.

Black tungsten nitride as a metallic photocatalyst for overall water splitting operable at up to 765 nm

Energy Technology Data Exchange (ETDEWEB)

Wang, Yu Lei; Li, Yu Hang; Wang, Xue Lu; Chen, Ai Ping; Yang, Hua Gui [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai (China); Nie, Ting; Gong, Xue Qing [Key Laboratory for Advanced Materials, Centre for Computational Chemistry and Research Institute of Industrial Catalysis, East China University of Science and Technology, Shanghai (China); Zheng, Li Rong [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences (China)

2017-06-19

Semiconductor photocatalysts are hardly employed for overall water splitting beyond 700 nm, which is due to both thermodynamic aspects and activation barriers. Metallic materials as photocatalysts are known to overcome this limitation through interband transitions for creating electron-hole pairs; however, the application of metallic photocatalysts for overall water splitting has never been fulfilled. Black tungsten nitride is now employed as a metallic photocatalyst for overall water splitting at wavelengths of up to 765 nm. Experimental and theoretical results together confirm that metallic properties play a substantial role in exhibiting photocatalytic activity under red-light irradiation for tungsten nitride. This work represents the first red-light responsive photocatalyst for overall water splitting, and may open a promising venue in searching of metallic materials as efficient photocatalysts for solar energy utilization. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Modelling of uranium/plutonium splitting in purex process

International Nuclear Information System (INIS)

Boullis, B.; Baron, P.

1987-06-01

A mathematical model simulating the highly complex uranium/plutonium splitting operation in PUREX process has been achieved by the french ''Commissariat a l'Energie Atomique''. The development of such a model, which includes transfer and redox reactions kinetics for all the species involved, required an important experimental work in the field of basis chemical data acquisition. The model has been successfully validated by comparison of its results with those of specific trials achieved (at laboratory scale), and with the available results of the french reprocessing units operation. It has then been used for the design of french new plants splitting operations

Hydrogen generation due to water splitting on Si - terminated 4H-Sic(0001) surfaces

Science.gov (United States)

Li, Qingfang; Li, Qiqi; Yang, Cuihong; Rao, Weifeng

2018-02-01

The chemical reactions of hydrogen gas generation via water splitting on Si-terminated 4H-SiC surfaces with or without C/Si vacancies were studied by using first-principles. We studied the reaction mechanisms of hydrogen generation on the 4H-SiC(0001) surface. Our calculations demonstrate that there are major rearrangements in surface when H2O approaches the SiC(0001) surface. The first H splitting from water can occur with ground-state electronic structures. The second H splitting involves an energy barrier of 0.65 eV. However, the energy barrier for two H atoms desorbing from the Si-face and forming H2 gas is 3.04 eV. In addition, it is found that C and Si vacancies can form easier in SiC(0001)surfaces than in SiC bulk and nanoribbons. The C/Si vacancies introduced can enhance photocatalytic activities. It is easier to split OH on SiC(0001) surface with vacancies compared to the case of clean SiC surface. H2 can form on the 4H-SiC(0001) surface with C and Si vacancies if the energy barriers of 1.02 and 2.28 eV are surmounted, respectively. Therefore, SiC(0001) surface with C vacancy has potential applications in photocatalytic water-splitting.

High performance nanostructured Silicon heterojunction for water splitting on large scales

KAUST Repository

Bonifazi, Marcella

2017-11-02

In past years the global demand for energy has been increasing steeply, as well as the awareness that new sources of clean energy are essential. Photo-electrochemical devices (PEC) for water splitting applications have stirred great interest, and different approach has been explored to improve the efficiency of these devices and to avoid optical losses at the interfaces with water. These include engineering materials and nanostructuring the device\\'s surfaces [1]-[2]. Despite the promising initial results, there are still many drawbacks that needs to be overcome to reach large scale production with optimized performances [3]. We present a new device that relies on the optimization of the nanostructuring process that exploits suitably disordered surfaces. Additionally, this device could harvest light on both sides to efficiently gain and store the energy to keep the photocatalytic reaction active.

High performance nanostructured Silicon heterojunction for water splitting on large scales

KAUST Repository

Bonifazi, Marcella; Fu, Hui-chun; He, Jr-Hau; Fratalocchi, Andrea

2017-01-01

In past years the global demand for energy has been increasing steeply, as well as the awareness that new sources of clean energy are essential. Photo-electrochemical devices (PEC) for water splitting applications have stirred great interest, and different approach has been explored to improve the efficiency of these devices and to avoid optical losses at the interfaces with water. These include engineering materials and nanostructuring the device's surfaces [1]-[2]. Despite the promising initial results, there are still many drawbacks that needs to be overcome to reach large scale production with optimized performances [3]. We present a new device that relies on the optimization of the nanostructuring process that exploits suitably disordered surfaces. Additionally, this device could harvest light on both sides to efficiently gain and store the energy to keep the photocatalytic reaction active.

Synthesis of Porous Europium Oxide Particles for Photoelectrochemical Water Splitting

International Nuclear Information System (INIS)

Zeng, Cheng-Hui; Zheng, Kai; Lou, Kai-Li; Meng, Xiao-Ting; Yan, Zi-Qiao; Ye, Zhen-Ni; Su, Rui-Rui; Zhong, Shengliang

2015-01-01

Graphical abstract: Display Omitted - Highlights: • Porous Eu 2 O 3 particles were synthesized by a facile electrochemical method. • Porous Eu 2 O 3 NPs were firstly implemented as photoanode for PEC water splitting. • The Eu 2 O 3 NPs exhibited good PEC performance and stability. - Abstract: In this paper, we report the facile electrochemical synthesis of porous Eu 2 O 3 particles (NPs) and their implementation as photoanode for photoelectrochemical (PEC) water splitting for the first time. These porous Eu 2 O 3 NPs exhibit a significant photocurrent density of 40 μA cm −2 at 0.6 V vs. Ag/AgCl in 1 M KOH electrolyte under white light irradiation (Xe lamp, 100 mW cm −2 ). Moreover, the as-synthesized Eu 2 O 3 NPs have an excellent PEC stability with no obvious decay in its photocurrent after 100 min irradiation

Water splitting-biosynthetic system with CO₂ reduction efficiencies exceeding photosynthesis.

Science.gov (United States)

Liu, Chong; Colón, Brendan C; Ziesack, Marika; Silver, Pamela A; Nocera, Daniel G

2016-06-03

Artificial photosynthetic systems can store solar energy and chemically reduce CO2 We developed a hybrid water splitting-biosynthetic system based on a biocompatible Earth-abundant inorganic catalyst system to split water into molecular hydrogen and oxygen (H2 and O2) at low driving voltages. When grown in contact with these catalysts, Ralstonia eutropha consumed the produced H2 to synthesize biomass and fuels or chemical products from low CO2 concentration in the presence of O2 This scalable system has a CO2 reduction energy efficiency of ~50% when producing bacterial biomass and liquid fusel alcohols, scrubbing 180 grams of CO2 per kilowatt-hour of electricity. Coupling this hybrid device to existing photovoltaic systems would yield a CO2 reduction energy efficiency of ~10%, exceeding that of natural photosynthetic systems. Copyright © 2016, American Association for the Advancement of Science.

Toward visible light response: Overall water splitting using heterogeneous photocatalysts

KAUST Repository

Takanabe, Kazuhiro

2011-01-01

Extensive energy conversion of solar energy can only be achieved by large-scale collection of solar flux. The technology that satisfies this requirement must be as simple as possible to reduce capital cost. Overall water splitting by powder-form photocatalysts directly produces a mixture of H 2 and O2 (chemical energy) in a single reactor, which does not require any complicated parabolic mirrors and electronic devices. Because of its simplicity and low capital cost, it has tremendous potential to become the major technology of solar energy conversion. Development of highly efficient photocatalysts is desired. This review addresses why visible light responsive photocatalysts are essential to be developed. The state of the art for the photocatalysts for overall water splitting is briefly described. Moreover, various fundamental aspects for developing efficient photocatalysts, such as particle size of photocatalysts, cocatalysts, and reaction kinetics are discussed. Copyright © 2011 De Gruyter.

SUNgas: Thermochemical Approaches to Solar Fuels

Science.gov (United States)

Davidson, Jane

2013-04-01

Solar energy offers an intelligent solution to reduce anthropogenic emissions of greenhouse gases and to meet an expanding global demand for energy. A transformative change from fossil to solar energy requires collection, storage, and transport of the earth's most abundant but diffuse and intermittent source of energy. One intriguing approach for harvest and storage of solar energy is production of clean fuels via high temperature thermochemical processes. Concentrated solar energy is the heat source and biomass or water and carbon dioxide are the feedstocks. Two routes to produce fuels using concentrated solar energy and a renewable feed stock will be discussed: gasification of biomass or other carbonaceous materials and metal oxide cycles to produce synthesis gas. The first and most near term route to solar fuels is to gasify biomass. With conventional gasification, air or oxygen is supplied at fuel-rich levels to combust some of the feedstock and in this manner generate the energy required for conversion to H2 and CO. The partial-combustion consumes up to 40% of the energetic value of the feedstock. With air combustion, the product gas is diluted by high levels of CO2 and N2. Using oxygen reduces the product dilution, but at the expense of adding an oxygen plant. Supplying the required heat with concentrated solar radiation eliminates the need for partial combustion of the biomass feedstock. As a result, the product gas has an energetic value greater than that of the feedstock and it is not contaminated by the byproducts of combustion. The second promising route to solar fuels splits water and carbon dioxide. Two-step metal-oxide redox cycles hold out great potential because they the temperature required to achieve a reasonable degree of dissociation is lower than direct thermal dissociation and O2 and the fuel are produced in separate steps. The 1^st step is the endothermic thermal dissociation of the metal oxide to the metal or lower-valence metal oxide. The 2

Photocatalytic and Photoelectrochemical Water Splitting on TiO2 via Photosensitization

Directory of Open Access Journals (Sweden)

Saji Thomas Kochuveedu

2016-01-01

Full Text Available The search for an alternative to replace conventional fuel has been going on for years due to the limited storage of fossil fuel and excess CO2 emission from the fuel. Using H2 as fuel has gained wide attention recently, as well as consequently splitting of water into hydrogen and oxygen. Seminal semiconductors such as TiO2 and ZnO have their position of CB and VB in alignment with water reduction and oxidation potential, respectively, but their wide bandgap allows them to absorb only UV light of the solar spectrum. Combining narrow bandgap semiconductors or other visible light active sensitizers with TiO2/ZnO is a facile route to exploit the visible light region of the solar spectrum. In this review, I make an attempt to summarize the various photosensitizers used in combination with TiO2 for water splitting with recent reports as examples.

Heterogeneous Bimetallic Phosphide/Sulfide Nanocomposite for Efficient Solar-Energy-Driven Overall Water Splitting.

Science.gov (United States)

Xin, Yanmei; Kan, Xiang; Gan, Li-Yong; Zhang, Zhonghai

2017-10-24

Solar-driven overall water splitting is highly desirable for hydrogen generation with sustainable energy sources, which need efficient, earth-abundant, robust, and bifunctional electrocatalysts for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, we propose a heterogeneous bimetallic phosphide/sulfide nanocomposite electrocatalyst of NiFeSP on nickel foam (NiFeSP/NF), which shows superior electrocatalytic activity of low overpotentials of 91 mV at -10 mA cm -2 for HER and of 240 mV at 50 mA cm -2 for OER in 1 M KOH solution. In addition, the NiFeSP/NF presents excellent overall water splitting performance with a cell voltage as low as 1.58 V at a current density of 10 mA cm -2 . Combining with a photovoltaic device of a Si solar cell or integrating into photoelectrochemical (PEC) systems, the bifunctional NiFeSP/NF electrocatalyst implements unassisted solar-driven water splitting with a solar-to-hydrogen conversion efficiency of ∼9.2% and significantly enhanced PEC performance, respectively.

Facile formation of 2D Co2P@Co3O4 microsheets through in-situ toptactic conversion and surface corrosion: Bifunctional electrocatalysts towards overall water splitting

Science.gov (United States)

Yao, Lihua; Zhang, Nan; Wang, Yin; Ni, Yuanman; Yan, Dongpeng; Hu, Changwen

2018-01-01

Exploring efficient non-precious electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is crucial for many renewable energy conversion processes. In this work, we report that 2D Co2P@Co3O4 microsheets can be prepared through an in-situ toptactic conversion from single-crystal β-Co(OH)2 microplatelets, associated with a surface phosphatization and corrosion process. The resultant Co2P@Co3O4 2D hybrid materials can further serve as self-supported bifunctional catalytic electrodes to drive the overall water splitting for HER and OER simultaneously, with low overpotentials and high long-term stability. Furthermore, a water electrolyzer based on Co2P@Co3O4 hybrid as both anode and cathode is fabricated, which achieves 10 mA cm-2 current at only 1.57 V during water splitting process. Therefore, this work provides a facile strategy to obtain 2D Co2P-based micro/nanostructures, which act as low-cost and highly active electrocatalysts towards overall water splitting application.

Redox Kinetics and Nonstoichiometry of Ce0.5Zr0.5O2−δ for Water Splitting and Hydrogen Production

KAUST Repository

Zhao, Zhenlong; Uddi, Mruthunjaya; Tsvetkov, Nikolai; Yildiz, Bilge; Ghoniem, Ahmed F.

2017-01-01

Water splitting and chemical fuel production as a promising carbon-neutral energy solution relies critically on an efficient electrochemical process over catalyst surfaces. The fundamentals within the surface redox pathways, including the complex

Electrodeposition of Ni-Mo alloy coatings for water splitting reaction

Science.gov (United States)

Shetty, Akshatha R.; Hegde, Ampar Chitharanjan

2018-04-01

The present study reports the development of Ni-Mo alloy coatings for water splitting applications, using a citrate bath the inducing effect of Mo (reluctant metal) on electrodeposition, its relationship with their electrocatalytic efficiency were studied. The alkaline water splitting efficiency of Ni-Mo alloy coatings, for both hydrogen evolution reaction (HER) and oxygen evolution reaction were tested using cyclic voltammetry (CV) and chronopotentiometry (CP) techniques. Moreover, the practical utility of these electrode materials were evaluated by measuring the amount of H2 and O2 gas evolved. The variation in electrocatalytic activity with composition, structure, and morphology of the coatings were examined using XRD, SEM, and EDS analyses. The experimental results showed that Ni-Mo alloy coating is the best electrode material for alkaline HER and OER reactions, at lower and higher deposition current densities (c. d.'s) respectively. This behavior is attributed by decreased Mo and increased Ni content of the alloy coating and the number of electroactive centers.

Thermochemical treatment of radioactive waste by using powder metal fuels

International Nuclear Information System (INIS)

Dmitriev, S.A.; Ojovan, M.I.; Karlina, O.K.

2001-01-01

Full text: A thermochemical approach was suggested for treating and conditioning specific streams of radioactive wastes for example spent ion exchange resins, mixed, organic or chlorine-containing radioactive waste as well as in order to decontaminate heavily contaminated surfaces. Conventional treatment methods of such waste encounters serious problems concerning complete destruction of organic molecules and possible emissions of radionuclides, heavy metals and chemically hazardous species or in case of contaminated materials - complete removal of contamination from surface. The thermochemical treatment of radioactive waste uses powdered metal fuels (PMF) that are specifically formulated for the waste composition and react chemically with the waste components. Thermochemical treatment technologies use the energy of chemical reactions in the mixture of waste with PMF to sustain both decomposition and synthesis processes as well as processes of isomorphic substitutions of hazardous elements into stable mineral forms. The composition of the PMF is designed in such a way as to minimise the release of hazardous components and radionuclides in the off gas and to confine the contaminants in the mineral or glass like final products. The thermochemical procedures allow decomposition of organic matter and capturing hazardous radionuclides and chemical species simultaneously. Thermochemical treatment technologies are very efficient, easy to apply, they have low capital investment and can be used both at large and small facilities. An advantage of thermochemical technologies is their autonomy. Thus these technologies can be successfully applied in order to treat small amount of waste without usage of complex and expensive equipment. They can be used also in emergency situations. Currently the thermochemical treatment technologies were developed and demonstrated to be feasible as follows: 1. Decontamination of surfaces; 2. Processing of organic waste; 3. Vitrification of dusty

Solar water splitting by photovoltaic-electrolysis with a solar-to-hydrogen efficiency over 30%

Science.gov (United States)

Jia, Jieyang; Seitz, Linsey C.; Benck, Jesse D.; Huo, Yijie; Chen, Yusi; Ng, Jia Wei Desmond; Bilir, Taner; Harris, James S.; Jaramillo, Thomas F.

2016-01-01

Hydrogen production via electrochemical water splitting is a promising approach for storing solar energy. For this technology to be economically competitive, it is critical to develop water splitting systems with high solar-to-hydrogen (STH) efficiencies. Here we report a photovoltaic-electrolysis system with the highest STH efficiency for any water splitting technology to date, to the best of our knowledge. Our system consists of two polymer electrolyte membrane electrolysers in series with one InGaP/GaAs/GaInNAsSb triple-junction solar cell, which produces a large-enough voltage to drive both electrolysers with no additional energy input. The solar concentration is adjusted such that the maximum power point of the photovoltaic is well matched to the operating capacity of the electrolysers to optimize the system efficiency. The system achieves a 48-h average STH efficiency of 30%. These results demonstrate the potential of photovoltaic-electrolysis systems for cost-effective solar energy storage. PMID:27796309

USE OF THE MODULAR HELIUM REACTOR FOR HYDROGEN PRODUCTION

International Nuclear Information System (INIS)

SCHULTZ, K.R.

2003-01-01

OAK-B135 A significant ''Hydrogen Economy'' is predicted that will reduce our dependence on petroleum imports and reduce pollution and greenhouse gas emissions. Hydrogen is an environmentally attractive fuel that has the potential to displace fossil fuels, but contemporary hydrogen production is primarily based on fossil fuels. The author has recently completed a three-year project for the US Department of Energy (DOE) whose objective was to ''define an economically feasible concept for production of hydrogen, using an advanced high-temperature nuclear reactor as the energy source''. Thermochemical water-slitting, a chemical process that accomplishes the decomposition of water into hydrogen and oxygen, met this objective. The goal of the first phase of this study was to evaluate thermochemical processes which offer the potential for efficient, cost-effective, large-scale production of hydrogen, and to select one for further detailed consideration. They selected the Sulfur-Iodine cycle. In the second phase, they reviewed all the basic reactor types for suitability to provide the high temperature heat needed by the selected thermochemical water splitting cycle and chose the helium gas-cooled reactor. In the third phase they designed the chemical flowsheet for the thermochemical process and estimated the efficiency and cost of the process and the projected cost of producing hydrogen. These results are summarized in this report

Study of water nature in some crystallohydrates of pentasubstituted alkali metal salts of borotungstic acid using thermochemical method

International Nuclear Information System (INIS)

Kosmodem'yanskaya, G.V.; Sadykova, M.M.; Spitsyn, V.I.

1977-01-01

Kinetics of the dehydration process has been studied and heat of dehydration has been determined for salts 2.5Li 2 O x 0.5B 2 O 3 x 12.0WO 3 x 28.5H 2 O; 2.5Na 2 Ox0.5B 2 O 3 x 12.0WO 3 x 17.5H 2 O; 2.5K 2 O x 0.5B 2 O 3 x12.0WO 3 x 16.5H 2 O; 2.5Cs 2 O x 0.5B 2 O 3 x 12.0WO 3 x6.7H 2 O. Dehydration has been conducted in vacuum at 25-50 deg C. The study of the dehydration process has been performed thermochemically in a differential calorimeter. It has been shown that heat of dehydration depends on the nature of the cation. Lithium salt with a cation of a small radius has the highest heat of dehydration (6.4+-0.2 kcal/mol H 2 O). Cesium salt is dehydrated almost completely. A considerable part of water in crystallohydrates has a salting character. Kinetics of the dehydration process is described by the equation of the monomolecular reaction

Effects of key factors on solar aided methane steam reforming in porous medium thermochemical reactor

International Nuclear Information System (INIS)

Wang, Fuqiang; Tan, Jianyu; Ma, Lanxin; Leng, Yu

2015-01-01

Highlights: • Effects of key factors on chemical reaction for solar methane reforming are studied. • MCRT and FVM method coupled with UDFs is used to establish numerical model. • Heat and mass transfer model coupled with thermochemical reaction is established. • LTNE model coupled with P1 approximation is used for porous matrix solar reactor. • A formula between H 2 production and conductivity of porous matrix is put forward. - Abstract: With the aid of solar energy, methane reforming process can save up to 20% of the total methane consumption. Monte Carlo Ray Tracing (MCRT) method and Finite Volume Method (FVM) combined method are developed to establish the heat and mass transfer model coupled with thermochemical reaction kinetics for porous medium solar thermochemical reactor. In order to provide more temperature information, local thermal non-equilibrium (LTNE) model coupled with P1 approximation is established to investigate the thermal performance of porous medium solar thermochemical reaction. Effects of radiative heat loss and thermal conductivity of porous matrix on temperature distribution and thermochemical reaction for solar driven steam methane reforming process are numerically studied. Besides, the relationship between hydrogen production and thermal conductivity of porous matrix are analyzed. The results illustrate that hydrogen production shows a 3 order polynomial relation with thermal conductivity of porous matrix

Confinement dependence of electro-catalysts for hydrogen evolution from water splitting

Directory of Open Access Journals (Sweden)

Mikaela Lindgren

2014-02-01

Full Text Available Density functional theory is utilized to articulate a particular generic deconstruction of the electrode/electro-catalyst assembly for the cathode process during water splitting. A computational model was designed to determine how alloying elements control the fraction of H2 released during zirconium oxidation by water relative to the amount of hydrogen picked up by the corroding alloy. This model is utilized to determine the efficiencies of transition metals decorated with hydroxide interfaces in facilitating the electro-catalytic hydrogen evolution reaction. A computational strategy is developed to select an electro-catalyst for hydrogen evolution (HE, where the choice of a transition metal catalyst is guided by the confining environment. The latter may be recast into a nominal pressure experienced by the evolving H2 molecule. We arrived at a novel perspective on the uniqueness of oxide supported atomic Pt as a HE catalyst under ambient conditions.

Value added transformation of ubiquitous substrates into highly efficient and flexible electrodes for water splitting.

Science.gov (United States)

Sahasrabudhe, Atharva; Dixit, Harsha; Majee, Rahul; Bhattacharyya, Sayan

2018-05-22

Herein, we present an innovative approach for transforming commonly available cellulose paper into a flexible and catalytic current collector for overall water splitting. A solution processed soak-and-coat method of electroless plating was used to render a piece of paper conducting by conformably depositing metallic nickel nanoparticles, while still retaining the open macroporous framework. Proof-of-concept paper-electrodes are realized by modifying nickel-paper current collector with model electrocatalysts nickel-iron oxyhydroxide and nickel-molybdenum bimetallic alloy through electrodeposition route. The paper-electrodes demonstrate exceptional activities towards oxygen evolution reaction and hydrogen evolution reaction, requiring overpotentials of 240 and 32 mV at 50 and -10 mA cm -2 , respectively, even as they endure extreme mechanical stress. The generality of this approach is demonstrated by fabricating similar electrodes on cotton fabric, which also show high activity. Finally, a two-electrode paper-electrolyzer is constructed which can split water with an efficiency of 98.01%, and exhibits robust stability for more than 200 h.

Oriented epitaxial TiO2 nanowires for water splitting

Science.gov (United States)

Hou, Wenting; Cortez, Pablo; Wuhrer, Richard; Macartney, Sam; Bozhilov, Krassimir N.; Liu, Rong; Sheppard, Leigh R.; Kisailus, David

2017-06-01

Highly oriented epitaxial rutile titanium dioxide (TiO2) nanowire arrays have been hydrothermally grown on polycrystalline TiO2 templates with their orientation dependent on the underlying TiO2 grain. Both the diameter and areal density of the nanowires were tuned by controlling the precursor concentration, and the template surface energy and roughness. Nanowire tip sharpness was influenced by precursor solubility and diffusivity. A new secondary ion mass spectrometer technique has been developed to install additional nucleation sites in single crystal TiO2 templates and the effect on nanowire growth was probed. Using the acquired TiO2 nanowire synthesis knowhow, an assortment of nanowire arrays were installed upon the surface of undoped TiO2 photo-electrodes and assessed for their photo-electrochemical water splitting performance. The key result obtained was that the presence of short and dispersed nanowire arrays significantly improved the photocurrent when the illumination intensity was increased from 100 to 200 mW cm-2. This is attributed to the alignment of the homoepitaxially grown nanowires to the [001] direction, which provides the fastest charge transport in TiO2 and an improved pathway for photo-holes to find water molecules and undertake oxidation. This result lays a foundation for achieving efficient water splitting under conditions of concentrated solar illumination.

Contribution to the study of new hydrogen production, purification and storage processes

International Nuclear Information System (INIS)

Manaud, Jean-Pierre

1984-01-01

This research thesis addresses the various aspects of hydrogen production, purification and process within the scope of hydrogen-based energy production. Hydrogen production is achieved by water decomposition through a thermo-chemical process. The author reports the thermodynamic assessment of a water decomposition thermo-chemical cycle for chlorine and sulphur-related cycles. He reports the experimental investigation of hydrogen purification by selective diffusion, the study of contamination of a CeMg12 alloy by nitrogen, oxygen and water vapour with application to hydrogen storage under the form of hydrides [fr

Molecular concepts of water splitting. Nature's approach

International Nuclear Information System (INIS)

Cox, Nicholas; Lubitz, Wolfgang

2013-01-01

Based on studies of natural systems, much has also been learned concerning the design principles required for biomimetic catalysis of water splitting and hydrogen evolution. In summary, these include use of abundant and inexpensive metals, the effective protection of the active sites in functional environments, repair/replacement of active components in case of damage, and the optimization of reaction rates. Biomimetic chemistry aims to mimic all these features; many labs are working toward this goal by developing new approaches in the design and synthesis of such systems, encompassing not only the catalytic center, but also smart matrices and assembly via self-organization. More stable catalysts that do not require self-repair may be obtained from fully artificial (inorganic) catalytic systems that are totally different from the biological ones and only apply some basic principles learned from nature. Metals other than Mn/Ca, Fe, and Ni could be used (e.g. Co) in new ligand spheres and other matrices. For light harvesting, charge separation/stabilization, and the effective coupling of the oxidizing/reducing equivalents to the redox catalysts, different methods have been proposed - for example, covalently linked molecular donor-acceptor systems, photo-voltaic devices, semiconductor-based systems, and photoactive metal complexes. The aim of all these approaches is to develop catalytic systems that split water with sunlight into hydrogen and oxygen while displaying high efficiency and long-term stability. Such a system - either biological, biomimetic, or bioinspired - has the potential to be used on a large scale to produce 'solar fuels' (e.g. hydrogen or secondary products thereof). (orig.)

Hydrogen production by thermal water splitting using a thermal plasma

International Nuclear Information System (INIS)

Boudesocque, N.; Lafon, C.; Girold, C.; Vandensteendam, C.; Baronnet, J.M.

2006-01-01

CEA has been working for more than 10 years in plasma technologies devoted to waste treatment: incineration, vitrification, gases and liquid treatment. Based on this experience, CEA experiments since several years an innovative route for hydrogen production by thermal water splitting, using a plasma as heat source. This new approach could be considered as an alternative to electrolysis for massive hydrogen production from water and electricity. This paper presents a brief state of the art of water thermal plasmas, showing the temperatures and quench velocity ranges technologically achievable today. Thermodynamic properties of a water plasma are presented and discussed. A kinetic computational model is presented, describing the behavior of splitted products during the quench in a plasma plume for various parameters, such as the quench rate. The model results are compared to gas analysis in the plasma plume obtained with in-situ sampling probe. The plasma composition measurements are issued from an Optical Emission Spectroscopic method (OES). The prediction of 30 % H 2 recovery with a 108 K.s -1 quench rate has been verified. A second experimentation has been performed: mass gas analysis, flowrate measurement and OES to study the 'behavior' and species in underwater electrical arc stricken between graphite electrodes. With this quench, a synthesis gas was produced with a content 55 % of hydrogen. (authors)

An Oxygen-Insensitive Hydrogen Evolution Catalyst Coated by a Molybdenum-Based Layer for Overall Water Splitting

KAUST Repository

Garcia Esparza, Angel T.; Shinagawa, Tatsuya; Ould-Chikh, Samy; Qureshi, Muhammad; Peng, Xuyuan; Wei, Nini; Anjum, Dalaver H.; Clo, Alain M.; Weng, Tsu-Chien; Nordlund, Dennis; Sokaras, Dimosthenis; Kubota, Jun; Domen, Kazunari; Takanabe, Kazuhiro

2017-01-01

For overall water-splitting systems, it is essential to establish O2 -insensitive cathodes that allow cogeneration of H2 and O2 . An acid-tolerant electrocatalyst is described, which employs a Mo-coating on a metal surface to achieve selective H2 evolution in the presence of O2 . In operando X-ray absorption spectroscopy identified reduced Pt covered with an amorphous molybdenum oxyhydroxide hydrate with a local structural order composed of polyanionic trimeric units of molybdenum(IV). The Mo layer likely hinders O2 gas permeation, impeding contact with active Pt. Photocatalytic overall water splitting proceeded using MoOx /Pt/SrTiO3 with inhibited water formation from H2 and O2 , which is the prevailing back reaction on the bare Pt/SrTiO3 photocatalyst. The Mo coating was stable in acidic media for multiple hours of overall water splitting by membraneless electrolysis and photocatalysis.

An Oxygen-Insensitive Hydrogen Evolution Catalyst Coated by a Molybdenum-Based Layer for Overall Water Splitting

KAUST Repository

Garcia Esparza, Angel T.

2017-04-13

For overall water-splitting systems, it is essential to establish O2 -insensitive cathodes that allow cogeneration of H2 and O2 . An acid-tolerant electrocatalyst is described, which employs a Mo-coating on a metal surface to achieve selective H2 evolution in the presence of O2 . In operando X-ray absorption spectroscopy identified reduced Pt covered with an amorphous molybdenum oxyhydroxide hydrate with a local structural order composed of polyanionic trimeric units of molybdenum(IV). The Mo layer likely hinders O2 gas permeation, impeding contact with active Pt. Photocatalytic overall water splitting proceeded using MoOx /Pt/SrTiO3 with inhibited water formation from H2 and O2 , which is the prevailing back reaction on the bare Pt/SrTiO3 photocatalyst. The Mo coating was stable in acidic media for multiple hours of overall water splitting by membraneless electrolysis and photocatalysis.

Efficient Overall Water-Splitting Electrocatalysis Using Lepidocrocite VOOH Hollow Nanospheres

KAUST Repository

Shi, Huanhuan; Liang, Hanfeng; Ming, Fangwang; Wang, Zhoucheng

2016-01-01

be achieved with low overpotentials of 270 mV for the oxygen evolution reaction (OER) and 164 mV for the hydrogen evolution reaction (HER) at 10 mA cm-2 in 1 m KOH, respectively. Furthermore, when used as both the anode and cathode for overall water splitting

Thermochemical structure of the Earth's mantle and continental crust

DEFF Research Database (Denmark)

Guerri, Mattia

A detailed knowledge of the Earth's thermal structure and chemical composition is fundamental in order to understand the processes driving the planet ormation and evolution. The inaccessibility of most of the Earth's interior makes the determination of its thermo-chemical conditions a challenging...

Thermochemical evaluation and preparation of cesium uranates

International Nuclear Information System (INIS)

Takano, Masahide; Minato, Kazuo; Fukuda, Kousaku; Sato, Seichi; Ohashi, Hiroshi.

1997-03-01

Two kinds of cesium uranates, Cs 2 UO 4 and Cs 2 U 2 O 7 , which are predicted by thermochemical estimation to be formed in irradiated oxide fuels, were prepared from U 3 O 8 and Cs 2 CO 3 for measurements of the thermal expansions and thermal conductivities. In advance of the preparation, thermochemical calculations for the formation and decomposition of these cesium uranates were performed by Gibbs free energy minimizer. The preparation temperatures for Cs 2 UO 4 and Cs 2 U 2 O 7 were determined from the results of the thermochemical calculations. The prepared samples were analyzed by X-ray diffraction, which showed that the single phases of Cs 2 UO 4 and Cs 2 U 2 O 7 were formed. Thermogravimetry and differential thermal analysis were also performed on these samples, and the decomposition temperatures were evaluated. The experimental results were in good agreement with those of the thermochemical calculations. (author)

Exergy analysis of thermochemical ethanol production via biomass gasification and catalytic synthesis

NARCIS (Netherlands)

van der Heijden, H.H.J.L.; Ptasinski, K.J.

2012-01-01

In this paper an exergy analysis of thermochemical ethanol production from biomass is presented. This process combines a steam-blown indirect biomass gasification of woody feedstock, with a subsequent conversion of produced syngas into ethanol. The production process involves several process

Thermochemical study of MoS2 oxidation

International Nuclear Information System (INIS)

Filimonov, D.S.; Topor, N.D.; Kesler, Ya.A.

1990-01-01

Thermochemical studies of oxidation processes of metallic molybdenum, sulfur, molybdenum disulfide under different conditions in microcalorimeter are conducted. Values of thermal effects which are used to calculate standard formation enthalpy of MoS 2 and which correlate well are obtained. Δ f H 0 (MoS 2 ,298.15 K) recommended value constitutes (-223.0±16.7) kJ/mol

HYBRID SULFUR PROCESS REFERENCE DESIGN AND COST ANALYSIS

Energy Technology Data Exchange (ETDEWEB)

Gorensek, M.; Summers, W.; Boltrunis, C.; Lahoda, E.; Allen, D.; Greyvenstein, R.

2009-05-12

PBMR (Pty.) Ltd. in the RSA, with the Hybrid Sulfur (HyS) Process, under development by the Savannah River National Laboratory (SRNL) in the US as part of the NHI. This work was performed by SRNL, Westinghouse Electric Company, Shaw, PBMR (Pty) Ltd., and Technology Insights under a Technical Consulting Agreement (TCA). Westinghouse Electric, serving as the lead for the PBMR process heat application team, established a cost-shared TCA with SRNL to prepare an updated HyS thermochemical water-splitting process flowsheet, a nuclear hydrogen plant preconceptual design and a cost estimate, including the cost of hydrogen production. SRNL was funded by DOE under the NHI program, and the Westinghouse team was self-funded. The results of this work are presented in this Final Report. Appendices have been attached to provide a detailed source of information in order to document the work under the TCA contract.

Thermochemical equilibrium in a kernel of a UN TRISO coated fuel particle

International Nuclear Information System (INIS)

Kim, Young Min; Jo, C. K.; Lim, H. S.; Cho, M. S.; Lee, W. J.

2012-01-01

A coated fuel particle (CFP) with a uranium mononitride (UN) kernel has been recently considered as an advanced fuel option, such as in fully ceramic micro encapsulated (FCM) replacement fuel for light water reactors (LWRs). In FCM fuel, a large number of tri isotropic coated fuel particles (TRISOs) are embedded in a silicon carbide (SiC) matrix. Thermochemical equilibrium calculations can predict the chemical behaviors of a kernel in a TRISO of FCM fuel during irradiation. They give information on the kind and quantity of gases generated in a kernel during irradiation. This study treats the quantitative analysis of thermochemical equilibrium in a UN TRISO of FCM LWR fuel using HSC software

Experimental study on split air conditioner with new hybrid equipment of energy storage and water heater all year round

International Nuclear Information System (INIS)

Wang Shaowei; Liu Zhenyan; Li Yuan; Zhao Keke; Wang Zhigang

2005-01-01

This paper presents a split air conditioner with a new hybrid equipment of energy storage and water heater all year round (ACWES). The authors made a special design on the storage tank to adjust the refrigerant capacity in the storage coils under different functions, instead of adding an accumulator to the system. An ACWES prototype, rebuilt from an original split air conditioner, has been finished, and experimental study of the operation processes of the prototype was done from which some important conclusions and suggestions have been made, which were helpful in the primary design and improvement of an ACWES system for potential users

Nickel-based anodic electrocatalysts for fuel cells and water splitting

Science.gov (United States)

Chen, Dayi

Our world is facing an energy crisis, so people are trying to harvest and utilize energy more efficiently. One of the promising ways to harvest energy is via solar water splitting to convert solar energy to chemical energy stored in hydrogen. Another of the options to utilize energy more efficiently is to use fuel cells as power sources instead of combustion engines. Catalysts are needed to reduce the energy barriers of the reactions happening at the electrode surfaces of the water-splitting cells and fuel cells. Nickel-based catalysts happen to be important nonprecious electrocatalysts for both of the anodic reactions in alkaline media. In alcohol fuel cells, nickel-based catalysts catalyze alcohol oxidation. In water splitting cells, they catalyze water oxidation, i.e., oxygen evolution. The two reactions occur in a similar potential range when catalyzed by nickel-based catalysts. Higher output current density, lower oxidation potential, and complete substrate oxidation are preferred for the anode in the applications. In this dissertation, the catalytic properties of nickel-based electrocatalysts in alkaline medium for fuel oxidation and oxygen evolution are explored. By changing the nickel precursor solubility, nickel complex nanoparticles with tunable sizes on electrode surfaces were synthesized. Higher methanol oxidation current density is achieved with smaller nickel complex nanoparticles. DNA aggregates were used as a polymer scaffold to load nickel ion centers and thus can oxidize methanol completely at a potential about 0.1 V lower than simple nickel electrodes, and the methanol oxidation pathway is changed. Nickel-based catalysts also have electrocatalytic activity towards a wide range of substrates. Experiments show that methanol, ethanol, glycerol and glucose can be deeply oxidized and carbon-carbon bonds can be broken during the oxidation. However, when comparing methanol oxidation reaction to oxygen evolution reaction catalyzed by current nickel

Thermodynamic limits on the performance of a solar thermochemical energy storage system

Energy Technology Data Exchange (ETDEWEB)

Lovegrove, K [Australian National Univ., Canberra (Australia). Energy Research Centre

1993-12-01

General expressions for the exergetic and work recovery efficiencies of thermochemical storage systems have been developed by assuming that the reaction process is the only source irreversibility within the closed-loop system. These have been used to plot contours of constant efficiency for the ammonia-based thermochemical system. The effect of spontaneous separation of mixtures due to the preferential condensation of ammonia has been examined analytically and graphically. The analysis presented represents a necessary prerequisite for the optimization of system efficiencies by reactor design. (author)

Promoting Photocatalytic Overall Water Splitting by Controlled Magnesium Incorporation in SrTiO3 Photocatalysts.

Science.gov (United States)

Han, Kai; Lin, Yen-Chun; Yang, Chia-Min; Jong, Ronald; Mul, Guido; Mei, Bastian

2017-11-23

SrTiO 3 is a well-known photocatalyst inducing overall water splitting when exposed to UV irradiation of wavelengths water-splitting efficiency of the Mg:SrTiO x composites is up to 20 times higher compared to SrTiO 3 containing similar catalytic nanoparticles, and an apparent quantum yield (AQY) of 10 % can be obtained in the wavelength range of 300-400 nm. Detailed characterization of the Mg:SrTiO x composites revealed that Mg is likely substituting the tetravalent Ti ion, leading to a favorable surface-space-charge layer. This originates from tuning of the donor density in the cubic SrTiO 3 structure by Mg incorporation and enables high oxygen-evolution rates. Nevertheless, interfacing with an appropriate hydrogen evolution catalyst is mandatory and non-trivial to obtain high-performance in water splitting. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

3D structured Mo-doped Ni3S2 nanosheets as efficient dual-electrocatalyst for overall water splitting

Science.gov (United States)

Wu, Chengrong; Liu, Bitao; Wang, Jun; Su, Yongyao; Yan, Hengqing; Ng, Chuntan; Li, Cheng; Wei, Jumeng

2018-05-01

Searching for a cost-effective, high efficient and stable bifunctional electrocatalyst for overall water-splitting is critical to renewable energy systems. In this study, three-dimensional (3D) curved nanosheets of Mo-doped Ni3S2 grown on nickel foam were successfully synthesized via a one-step hydrothermal process. The hydrogen-evolution reaction (HER) and the oxygen-evolution reaction (OER) in alkaline environment of this 3D catalyst are investigated in detail. The results show that it possesses lower overpotential, high current densities and small Tafel slopes both in OER and HER. For HER, the catalysts show excellent electrochemical performance, demonstrating a low over-potential of 212 mV at 10 mA cm-2 with a large decrease of 127 mV compared to the undoped Ni3S2. And it also shows a lower overpotential of 260 mV at 10 mA cm-2 which decreases 30 mV for OER. In addition, it is only need 1.67 V for the overall water splitting at 10 mA cm-2 which is 70 mV. It found that the Mo element would change the morphology of Ni3S2 and induce much more active sites for HER and OER. The as-prepared Mo-doped Ni3S2 bi-functional electrocatalyst could act as the promising electrode materials for water splitting.

Prussian Blue Analogues Derived Penroseite (Ni,Co)Se2 Nanocages Anchored on 3D Graphene Aerogel for Efficient Water Splitting

KAUST Repository

Xu, Xun; Liang, Hanfeng; Ming, Fangwang; Qi, Zhengbing; Xie, Yaqiang; Wang, Zhoucheng

2017-01-01

Efficient water splitting demands highly active, low cost, and robust electrocatalysts. In this study, we report the synthesis of penroseite (Ni,Co)Se2 nanocages anchored on 3D graphene aerogel using Prussian blue analogues as precursor and further their applications in overall water splitting electrolysis. The synergy between the high activity of (Ni,Co)Se2 and the good conductivity of graphene leads to superior performance of the hybrid toward the water splitting in basic solutions. The (Ni,Co)Se2-GA only requires a low cell voltage of 1.60 V to reach the current density of 10 mA cm-2, making the (Ni,Co)Se2-GA hybrid a competitive alternative to noble metal based catalysts for water splitting.

Prussian Blue Analogues Derived Penroseite (Ni,Co)Se2 Nanocages Anchored on 3D Graphene Aerogel for Efficient Water Splitting

KAUST Repository

Xu, Xun

2017-08-14

Efficient water splitting demands highly active, low cost, and robust electrocatalysts. In this study, we report the synthesis of penroseite (Ni,Co)Se2 nanocages anchored on 3D graphene aerogel using Prussian blue analogues as precursor and further their applications in overall water splitting electrolysis. The synergy between the high activity of (Ni,Co)Se2 and the good conductivity of graphene leads to superior performance of the hybrid toward the water splitting in basic solutions. The (Ni,Co)Se2-GA only requires a low cell voltage of 1.60 V to reach the current density of 10 mA cm-2, making the (Ni,Co)Se2-GA hybrid a competitive alternative to noble metal based catalysts for water splitting.

Defect-engineered GaN:Mg nanowire arrays for overall water splitting under violet light

International Nuclear Information System (INIS)

Kibria, M. G.; Chowdhury, F. A.; Zhao, S.; Mi, Z.; Trudeau, M. L.; Guo, H.

2015-01-01

We report that by engineering the intra-gap defect related energy states in GaN nanowire arrays using Mg dopants, efficient and stable overall neutral water splitting can be achieved under violet light. Overall neutral water splitting on Rh/Cr 2 O 3 co-catalyst decorated Mg doped GaN nanowires is demonstrated with intra-gap excitation up to 450 nm. Through optimized Mg doping, the absorbed photon conversion efficiency of GaN nanowires reaches ∼43% at 375–450 nm, providing a viable approach to extend the solar absorption of oxide and non-oxide photocatalysts

Safety Assessments for the IS Process in a Hydrogen Production Facility

International Nuclear Information System (INIS)

Jung, Gun Hyo; Cho, Nam Chul; Jae, Moo Sung

2006-01-01

The thermochemical water decomposition cycle is one of the methods for the hydrogen production process from water. The successful continuous operation of the IS-process was demonstrated and this process is one of the thermochemical processes, which is the closest to be industrialized. Currently, Korea has also started a research about the IS process and the construction of the IS process system is planned. In this study, for risk analysis of the IS process, initiating events of the IS process are identified by using the Master Logic Diagram (MLD) which is the method for initiating the event identification. Also, 6 events were identified among 9 initiating events above and performed quantification of events using event tree analysis

Modeling and Simulation of the Sulfur-Iodine Process Coupled to a Very High-Temperature Gas-Cooled Nuclear Reactor

Energy Technology Data Exchange (ETDEWEB)

Shin, Youngjoon; Lee, Taehoon; Lee, Kiyoung; Kim, Minhwan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-10-15

Hydrogen produced from water using nuclear energy will avoid both the use of fossil fuel and CO{sub 2} emission presumed to be the dominant reason for global warming. A thermo-chemical sulfur-iodine (SI) process coupled to a Very High Temperature Gas-Cooled Reactor(VHTR) is one of the most prospective hydrogen production methods that split water using nuclear energy because the SI process is suitable for large-scale hydrogen production without CO{sub 2} emission. The dynamic simulation code to evaluate the start-up behavior of the chemical reactors placed on the secondary helium loop of the SI process has been developed and partially verified using the steady state values obtained from the Aspen Plus{sup TM} Code simulation. As the start-up dynamic simulation results of the SI process coupled to the IHX, which is one of components in the VHTR system, it is expected that the integrated secondary helium loop of the SI process can be successfully and safely approach the steady state condition.

Photocatalytic water splitting with acridine dyes: Guidelines from computational chemistry

Energy Technology Data Exchange (ETDEWEB)

Liu, Xiaojun [Department of Chemistry, Technical University of Munich, D-85747 Garching (Germany); Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044 (China); Karsili, Tolga N.V. [Department of Chemistry, Technical University of Munich, D-85747 Garching (Germany); Sobolewski, Andrzej L. [Institute of Physics, Polish Academy of Sciences, PL-02668 Warsaw (Poland); Domcke, Wolfgang, E-mail: domcke@ch.tum.de [Department of Chemistry, Technical University of Munich, D-85747 Garching (Germany)

2016-01-13

Highlights: • Photoexcited acridine dyes are able to abstract a hydrogen atom from water. • Photodetachment of the hydrogen atom from the radicals regenerates the catalyzer. • The reaction mechanisms were characterized with ab initio electronic-structure calculations. • The chromophores and radicals absorb within the range of the solar spectrum. - Abstract: The photocatalytic splitting of water into H{sup ·} and OH{sup ·} radicals in hydrogen-bonded chromophore-water complexes has been explored with computational methods for the chromophores acridine orange (AO) and benzacridine (BA). These dyes are strong absorbers within the range of the solar spectrum. It is shown that low-lying charge-transfer excited states exist in the hydrogen-bonded AO−H{sub 2}O and BA−H{sub 2}O complexes which drive the transfer of a proton from water to the chromophore, which results in AOH{sup ·}−OH{sup ·} or BAH{sup ·}−OH{sup ·} biradicals. The AOH{sup ·} and BAH{sup ·} radicals possess bright ππ{sup ∗} excited states with vertical excitation energies near 3.0 eV which are predissociated by a low-lying repulsive πσ{sup ∗} state. The conical intersections of the πσ{sup ∗} state with the ππ{sup ∗} excited states and the ground state provide a mechanism for the photodetachment of the H-atom by a second photon. Our results indicate that AO and BA are promising chromophores for water splitting with visible light.

Efficient solar-driven water splitting by nanocone BiVO4-perovskite tandem cells

Science.gov (United States)

Qiu, Yongcai; Liu, Wei; Chen, Wei; Chen, Wei; Zhou, Guangmin; Hsu, Po-Chun; Zhang, Rufan; Liang, Zheng; Fan, Shoushan; Zhang, Yuegang; Cui, Yi

2016-01-01

Bismuth vanadate (BiVO4) has been widely regarded as a promising photoanode material for photoelectrochemical (PEC) water splitting because of its low cost, its high stability against photocorrosion, and its relatively narrow band gap of 2.4 eV. However, the achieved performance of the BiVO4 photoanode remains unsatisfactory to date because its short carrier diffusion length restricts the total thickness of the BiVO4 film required for sufficient light absorption. We addressed the issue by deposition of nanoporous Mo-doped BiVO4 (Mo:BiVO4) on an engineered cone-shaped nanostructure, in which the Mo:BiVO4 layer with a larger effective thickness maintains highly efficient charge separation and high light absorption capability, which can be further enhanced by multiple light scattering in the nanocone structure. As a result, the nanocone/Mo:BiVO4/Fe(Ni)OOH photoanode exhibits a high water-splitting photocurrent of 5.82 ± 0.36 mA cm−2 at 1.23 V versus the reversible hydrogen electrode under 1-sun illumination. We also demonstrate that the PEC cell in tandem with a single perovskite solar cell exhibits unassisted water splitting with a solar-to-hydrogen conversion efficiency of up to 6.2%. PMID:27386565

Holistic analysis of thermochemical processes by using solid biomass for fuel production in Germany; Ganzheitliche Analyse thermochemischer Verfahren bei der Nutzung fester Biomasse zur Kraftstoffproduktion in Deutschland

Energy Technology Data Exchange (ETDEWEB)

Henssler, Martin

2015-04-28

According to the German act ''Biokraftstoff-Nachhaltigkeitsverordnung'', biofuels must show a CO{sub 2eq}-reduction compared to the fossil reference fuel (83.8 g CO{sub 2eq}/MJ{sub fuel} /Richtlinie 98/70/EG/) of 35 % beginning with 2011. In new plants, which go into operation after the 31.12.2016 the CO{sub 2eq}-savings must be higher than 50 % in 2017 and higher than 60 % in 2018 /Biokraft-NachV/. The biofuels (methyl ester of rapeseed, bioethanol and biomethane) considered in this study do not meet these requirements for new plants. To comply with these rules new processes must be deployed. Alternative thermochemical generated fuels could be an option. The aim of this work is to evaluate through a technical, ecological and economic analysis (Well-to-Wheel) whether and under what conditions the thermochemical production of Fischer-Tropsch-diesel or -gasoline, hydrogen (H{sub 2}) and Substitute Natural Gas (SNG) complies with the targets. Four different processes are considered (fast pyrolysis and torrefaction with entrained flow gasifier, CHOREN Carbo-V {sup registered} -gasifier, Absorption Enhanced Reforming (AER-) gasifier). Beside residues such as winter wheat straw and residual forest wood, wood from short-rotation plantations is taken into account. The technical analysis showed that at present status (2010) two and in 2050 six plants can be operated energy-self-sufficient. The overall efficiency of the processes is in the range of 41.5 (Fischer-Tropsch-diesel or -gasoline) and 59.4 % (H{sub 2}). Furthermore, it was found that for 2010, all thermochemical produced fuels except the H{sub 2}-production from wood from short-rotation plantations in decentralised or central fast pyrolysis and in decentralised torrefactions with entrained flow gasifier keep the required CO{sub 2eq}-saving of 60 %. In 2050, all thermochemical produced fuels will reach these limits. The CO{sub 2eq}-saving is between 72 (H{sub 2}) and 95 % (Fischer

Water splitting and the band edge positions of TiO2

Czech Academy of Sciences Publication Activity Database

Deák, P.; Kullgren, J.; Aradi, B.; Frauenheim, T.; Kavan, Ladislav

2016-01-01

Roč. 199, MAY 2016 (2016), s. 27-34 ISSN 0013-4686 R&D Projects: GA ČR GA13-07724S Grant - others:COST(XE) CM1104 Institutional support: RVO:61388955 Keywords : water splitting * rutile * anatase Subject RIV: CG - Electrochemistry Impact factor: 4.798, year: 2016

Research and development on process components for hydrogen production. (1) Test-fabrication of sulfuric acid transfer pump

International Nuclear Information System (INIS)

Iwatsuki, Jin; Terada, Atsuhiko; Hino, Ryutaro; Kubo, Shinji; Onuki, Kaoru; Watanabe, Yutaka

2009-01-01

Japan Atomic Energy Agency has been conducting a research and development on hydrogen production system using High Temperature Gas-Cooled Reactor. As a part of this effort, thermochemical water-splitting cycle featuring iodine- and sulfur-compounds (IS process) is under development considering its potential of large-scale economical hydrogen production. The IS process constitutes very severe environments to the materials of construction because of the corrosive nature of process chemicals, especially of the high temperature acidic solutions of sulfuric acid and hydriodic acid dissolving iodine. Therefore, selection of the corrosion-resistant materials and development of the components have been the crucial subjects of process development. This paper concerns the sulfuric acid transfer pump. The development has been implemented of a pump for transporting concentrated sulfuric acid at temperatures of higher than 300degC and at elevated pressure. Recent progress of these activities will be reported. (author)

Thermochemical conversion of microalgal biomass into biofuels: a review.

Science.gov (United States)

Chen, Wei-Hsin; Lin, Bo-Jhih; Huang, Ming-Yueh; Chang, Jo-Shu

2015-05-01

Following first-generation and second-generation biofuels produced from food and non-food crops, respectively, algal biomass has become an important feedstock for the production of third-generation biofuels. Microalgal biomass is characterized by rapid growth and high carbon fixing efficiency when they grow. On account of potential of mass production and greenhouse gas uptake, microalgae are promising feedstocks for biofuels development. Thermochemical conversion is an effective process for biofuel production from biomass. The technology mainly includes torrefaction, liquefaction, pyrolysis, and gasification. Through these conversion technologies, solid, liquid, and gaseous biofuels are produced from microalgae for heat and power generation. The liquid bio-oils can further be upgraded for chemicals, while the synthesis gas can be synthesized into liquid fuels. This paper aims to provide a state-of-the-art review of the thermochemical conversion technologies of microalgal biomass into fuels. Detailed conversion processes and their outcome are also addressed. Copyright © 2014 Elsevier Ltd. All rights reserved.

New applications with time-dependent thermochemical simulation

Energy Technology Data Exchange (ETDEWEB)

Koukkari, P. [VTT Chemical Technology, Espoo (Finland); Laukkanen, L. [VTT Automation, Espoo (Finland); Penttilae, K. [Kemira Engineering Oy, Helsinki (Finland)

1996-12-31

A new method (RATEMIX) to calculate multicomponent chemical reaction mixtures as a series of sequential thermochemical states was recently introduced. The procedure combines multicomponent thermodynamics with chemical kinetics and may be used to simulate the multicomponent reactors as a thermochemical natural process. The method combines the desired reaction rates sequentially with constrained Gibbs energy minimization. The reactant concentrations are determined by the experimental (Arrhenius) rate laws. During the course of the given reaction the subsequent side reactions are supposed to occur reversibly. At every sequential stage of the given reaction the temperature and composition of the reaction mixture are calculated by a thermodynamic subroutine, which minimizes the Gibbs energy of the system and takes into account the heat transfer between the system and its surroundings. The extents of reaction are included as algorithmic constraints in the Gibbs energy minimization procedure. Initially, the reactants are introduced to the system as inert copies to match both the mass and energy balance of the reactive system. During the calculation the copies are sequentially interchanged to the actual reactants which allows one to simulate the time-dependent reaction route by using the thermochemical procedure. For each intermediate stage, the temperature and composition are calculated and as well numerical estimates of the thermodynamic functions are obtained. The method is applicable in processes where the core thermodynamic and kinetic data of the system are known and the time-dependent heat transfer data can either be measured or estimated by calculation. The method has been used to simulate e.g. high temperature flame reactions, zinc vapour oxidation and a counter-current rotary drum with chemical reactions. The procedure has today been tested with SOLGASMIX, CHEMSAGE and HSC programs. (author)

New applications with time-dependent thermochemical simulation

Energy Technology Data Exchange (ETDEWEB)

Koukkari, P [VTT Chemical Technology, Espoo (Finland); Laukkanen, L [VTT Automation, Espoo (Finland); Penttilae, K [Kemira Engineering Oy, Helsinki (Finland)

1997-12-31

A new method (RATEMIX) to calculate multicomponent chemical reaction mixtures as a series of sequential thermochemical states was recently introduced. The procedure combines multicomponent thermodynamics with chemical kinetics and may be used to simulate the multicomponent reactors as a thermochemical natural process. The method combines the desired reaction rates sequentially with constrained Gibbs energy minimization. The reactant concentrations are determined by the experimental (Arrhenius) rate laws. During the course of the given reaction the subsequent side reactions are supposed to occur reversibly. At every sequential stage of the given reaction the temperature and composition of the reaction mixture are calculated by a thermodynamic subroutine, which minimizes the Gibbs energy of the system and takes into account the heat transfer between the system and its surroundings. The extents of reaction are included as algorithmic constraints in the Gibbs energy minimization procedure. Initially, the reactants are introduced to the system as inert copies to match both the mass and energy balance of the reactive system. During the calculation the copies are sequentially interchanged to the actual reactants which allows one to simulate the time-dependent reaction route by using the thermochemical procedure. For each intermediate stage, the temperature and composition are calculated and as well numerical estimates of the thermodynamic functions are obtained. The method is applicable in processes where the core thermodynamic and kinetic data of the system are known and the time-dependent heat transfer data can either be measured or estimated by calculation. The method has been used to simulate e.g. high temperature flame reactions, zinc vapour oxidation and a counter-current rotary drum with chemical reactions. The procedure has today been tested with SOLGASMIX, CHEMSAGE and HSC programs. (author)

Thermochemical evaluation and preparation of cesium uranates

Energy Technology Data Exchange (ETDEWEB)

Takano, Masahide; Minato, Kazuo; Fukuda, Kousaku [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Sato, Seichi; Ohashi, Hiroshi

1997-03-01

Two kinds of cesium uranates, Cs{sub 2}UO{sub 4} and Cs{sub 2}U{sub 2}O{sub 7}, which are predicted by thermochemical estimation to be formed in irradiated oxide fuels, were prepared from U{sub 3}O{sub 8} and Cs{sub 2}CO{sub 3} for measurements of the thermal expansions and thermal conductivities. In advance of the preparation, thermochemical calculations for the formation and decomposition of these cesium uranates were performed by Gibbs free energy minimizer. The preparation temperatures for Cs{sub 2}UO{sub 4} and Cs{sub 2}U{sub 2}O{sub 7} were determined from the results of the thermochemical calculations. The prepared samples were analyzed by X-ray diffraction, which showed that the single phases of Cs{sub 2}UO{sub 4} and Cs{sub 2}U{sub 2}O{sub 7} were formed. Thermogravimetry and differential thermal analysis were also performed on these samples, and the decomposition temperatures were evaluated. The experimental results were in good agreement with those of the thermochemical calculations. (author)

Ni3S2 nanowires grown on nickel foam as an efficient bifunctional electrocatalyst for water splitting with greatly practical prospects

Science.gov (United States)

Zhang, Dawei; Li, Jingwei; Luo, Jiaxian; Xu, Peiman; Wei, Licheng; Zhou, Dan; Xu, Weiming; Yuan, Dingsheng

2018-06-01

It is essential to synthesize low-cost, earth-abundant bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reactions (OER) for water electrolysis. Herein, we present a one-step sulfurization method to fabricate Ni3S2 nanowires directly grown on Ni foam (Ni3S2 NWs/Ni) as such an electrocatalyst. This synthetic strategy has several advantages including facile preparation, low cost and can even be expanded to large-scale preparation for practical applications. The as-synthesized Ni3S2 NWs/Ni exhibits a low overpotential of 81 and 317 mV to render a current density of 10 mA cm‑2 for the HER and OER, respectively, in 1.0 mol l‑1 KOH solution. The Ni3S2 NWs/Ni was integrated to be the cathode and the anode in the alkaline electrolyzer for overall water splitting with a current density of 10 mA cm‑2 afforded at a cell voltage of 1.63 V. More importantly, this electrolyzer maintained its electrocatalytic activity even after continual water splitting for 30 h. Owing to its simple synthesis process, the earth-abundant electrocatalyst and high performance, this versatile Ni3S2 NWs/Ni electrode will become a promising electrocatalyst for water splitting.

Photocatalytic water splitting: Materials design and high-throughput screening of molecular compositions

Science.gov (United States)

Khnayzer, Rony S.

Due to the expected increases on energy demand in the near future, the development of new catalytic molecular compositions and materials capable of directly converting water, with the aid of solar photons, into hydrogen becomes obviated. Hydrogen is a combustible fuel and precious high-energy feedstock chemical. However, for the water-splitting reaction to proceed efficiently and economically enough for large-scale application, efficient light-absorbing sensitizers and water splitting catalysts are required. To study the kinetics of the water reduction reaction, we have used titania (TiO2) nanoparticles as a robust scaffold to photochemically grow platinum (Pt) nanoparticles from a unique surface-anchored molecular precursor Pt(dcbpy)Cl2 [dcbpy = 4,4'-dicarboxylic acid-2,2'-bipyridine]. The hybrid Pt/TiO 2 nanomaterials obtained were shown to be a superior water reduction catalyst (WRC) in aqueous suspensions when compared with the benchmark platinized TiO2. In addition, cobalt phosphate (CoPi) water oxidation catalyst (WOC) was photochemically assembled on the surface of TiO2, and its structure and mechanism of activity showed resemblance to the established electrochemically grown CoPi material. Both WRC and WOC described above possessed near unity Faradaic efficiency for hydrogen and oxygen production respectively, and were fully characterized by electron microscopy, x-ray absorption spectroscopy, electrochemistry and photochemistry. While there are established materials and molecules that are able to drive water splitting catalysis, some of these efficient semiconductors, including titanium dioxide (TiO2) and tungsten trioxide (WO3), are only able to absorb high-energy (ultraviolet or blue) photons. This high-energy light represents merely a fraction of the solar spectrum that strikes the earth and the energy content of those remaining photons is simply wasted. A strategy to mitigate this problem has been developed over the years in our laboratory. Briefly

Preconceptual design of a salt splitting process using ceramic membranes

Energy Technology Data Exchange (ETDEWEB)

Kurath, D.E.; Brooks, K.P.; Hollenberg, G.W.; Clemmer, R. [Pacific Northwest National Lab., Richland, WA (United States); Balagopal, S.; Landro, T.; Sutija, D.P. [Ceramatec, Inc., Salt Lake City, UT (United States)

1997-01-01

Inorganic ceramic membranes for salt splitting of radioactively contaminated sodium salt solutions are being developed for treating U. S. Department of Energy tank wastes. The process consists of electrochemical separation of sodium ions from the salt solution using sodium (Na) Super Ion Conductors (NaSICON) membranes. The primary NaSICON compositions being investigated are based on rare- earth ions (RE-NaSICON). Potential applications include: caustic recycling for sludge leaching, regenerating ion exchange resins, inhibiting corrosion in carbon-steel tanks, or retrieving tank wastes; reducing the volume of low-level wastes volume to be disposed of; adjusting pH and reducing competing cations to enhance cesium ion exchange processes; reducing sodium in high-level-waste sludges; and removing sodium from acidic wastes to facilitate calcining. These applications encompass wastes stored at the Hanford, Savannah River, and Idaho National Engineering Laboratory sites. The overall project objective is to supply a salt splitting process unit that impacts the waste treatment and disposal flowsheets and meets user requirements. The potential flowsheet impacts include improving the efficiency of the waste pretreatment processes, reducing volume, and increasing the quality of the final waste disposal forms. Meeting user requirements implies developing the technology to the point where it is available as standard equipment with predictable and reliable performance. This report presents two preconceptual designs for a full-scale salt splitting process based on the RE-NaSICON membranes to distinguish critical items for testing and to provide a vision that site users can evaluate.

Preconceptual design of a salt splitting process using ceramic membranes

International Nuclear Information System (INIS)

Kurath, D.E.; Brooks, K.P.; Hollenberg, G.W.; Clemmer, R.; Balagopal, S.; Landro, T.; Sutija, D.P.

1997-01-01

Inorganic ceramic membranes for salt splitting of radioactively contaminated sodium salt solutions are being developed for treating U. S. Department of Energy tank wastes. The process consists of electrochemical separation of sodium ions from the salt solution using sodium (Na) Super Ion Conductors (NaSICON) membranes. The primary NaSICON compositions being investigated are based on rare- earth ions (RE-NaSICON). Potential applications include: caustic recycling for sludge leaching, regenerating ion exchange resins, inhibiting corrosion in carbon-steel tanks, or retrieving tank wastes; reducing the volume of low-level wastes volume to be disposed of; adjusting pH and reducing competing cations to enhance cesium ion exchange processes; reducing sodium in high-level-waste sludges; and removing sodium from acidic wastes to facilitate calcining. These applications encompass wastes stored at the Hanford, Savannah River, and Idaho National Engineering Laboratory sites. The overall project objective is to supply a salt splitting process unit that impacts the waste treatment and disposal flowsheets and meets user requirements. The potential flowsheet impacts include improving the efficiency of the waste pretreatment processes, reducing volume, and increasing the quality of the final waste disposal forms. Meeting user requirements implies developing the technology to the point where it is available as standard equipment with predictable and reliable performance. This report presents two preconceptual designs for a full-scale salt splitting process based on the RE-NaSICON membranes to distinguish critical items for testing and to provide a vision that site users can evaluate

Photoelectrochemical water splitting using a Cu(In,Ga)Se{sub 2} thin film

Energy Technology Data Exchange (ETDEWEB)

Yokoyama, Daisuke; Minegishi, Tsutomu; Maeda, Kazuhiko; Katayama, Masao; Kubota, Jun; Domen, Kazunari [Department of Chemical System Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Yamada, Akira; Konagai, Makoto [Department of Physical Electronics, Graduate School of Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan)

2010-06-15

The effects of surface modification and reaction conditions on the photoelectrochemical properties of polycrystalline Cu(In,Ga)Se{sub 2} (CIGS) thin films for water splitting were studied. CIGS modified with platinum particles (Pt/CIGS) generated a cathodic photocurrent at potentials up to + 0.4 V vs. RHE at pH = 9.5. The photocurrent was stable for 16 h, which resulted in a turnover number of over 500. A CdS-inserted film (Pt/CdS/CIGS) had significantly improved properties compared to Pt/CIGS: a 0.3 V higher onset potential of cathodic photocurrent and a three-fold increase in the quantum efficiency. Our results suggest the feasibility of CIGS as a photocathode for biphotoelectrochemical water splitting. (author)

An oxygen-insensitive hydrogen evolution catalyst coated by a molybdenum-based layer for overall water splitting

Energy Technology Data Exchange (ETDEWEB)

Garcia-Esparza, Angel T.; Shinagawa, Tatsuya; Ould-Chikh, Samy; Qureshi, Muhammad; Peng, Xuyuan; Takanabe, Kazuhiro [KAUST Catalysis Center (KCC) and Physical Science and Engineering Division - PSE, King Abdullah University of Science and Technology (KAUST), Thuwal (Saudi Arabia); Wei, Nini; Anjum, Dalaver H. [Advanced Nanofabrication, Imaging and Characterization Core Lab, King Abdullah University of Science and Technology (KAUST), Thuwal (Saudi Arabia); Clo, Alain [Research Computing, King Abdullah University of Science and Technology (KAUST), Thuwal (Saudi Arabia); Weng, Tsu-Chien [Center for High Pressure Science and Technology Advanced Research, Shanghai (China); Nordlund, Dennis; Sokaras, Dimosthenis [Stanford Synchrotron Radiation Lightsource, Menlo Park, CA (United States); Kubota, Jun [Department of Chemical Engineering, Fukuoka University (Japan); Domen, Kazunari [Department of Chemical System Engineering, School of Engineering, The University of Tokyo (Japan)

2017-05-15

For overall water-splitting systems, it is essential to establish O{sub 2}-insensitive cathodes that allow cogeneration of H{sub 2} and O{sub 2}. An acid-tolerant electrocatalyst is described, which employs a Mo-coating on a metal surface to achieve selective H{sub 2} evolution in the presence of O{sub 2}. In operando X-ray absorption spectroscopy identified reduced Pt covered with an amorphous molybdenum oxyhydroxide hydrate with a local structural order composed of polyanionic trimeric units of molybdenum(IV). The Mo layer likely hinders O{sub 2} gas permeation, impeding contact with active Pt. Photocatalytic overall water splitting proceeded using MoO{sub x}/Pt/SrTiO{sub 3} with inhibited water formation from H{sub 2} and O{sub 2}, which is the prevailing back reaction on the bare Pt/SrTiO{sub 3} photocatalyst. The Mo coating was stable in acidic media for multiple hours of overall water splitting by membraneless electrolysis and photocatalysis. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Thermochemical production of liquid fuels from biomass: Thermo-economic modeling, process design and process integration analysis

International Nuclear Information System (INIS)

Tock, Laurence; Gassner, Martin; Marechal, Francois

2010-01-01

A detailed thermo-economic model combining thermodynamics with economic analysis and considering different technological alternatives for the thermochemical production of liquid fuels from lignocellulosic biomass is presented. Energetic and economic models for the production of Fischer-Tropsch fuel (FT), methanol (MeOH) and dimethyl ether (DME) by means of biomass drying with steam or flue gas, directly or indirectly heated fluidized bed or entrained flow gasification, hot or cold gas cleaning, fuel synthesis and upgrading are reviewed and developed. The process is integrated and the optimal utility system is computed. The competitiveness of the different process options is compared systematically with regard to energetic, economic and environmental considerations. At several examples, it is highlighted that process integration is a key element that allows for considerably increasing the performance by optimal utility integration and energy conversion. The performance computations of some exemplary technology scenarios of integrated plants yield overall energy efficiencies of 59.8% (crude FT-fuel), 52.5% (MeOH) and 53.5% (DME), and production costs of 89, 128 and 113 Euro MWh -1 on fuel basis. The applied process design approach allows to evaluate the economic competitiveness compared to fossil fuels, to study the influence of the biomass and electricity price and to project for different plant capacities. Process integration reveals in particular potential energy savings and waste heat valorization. Based on this work, the most promising options for the polygeneration of fuel, power and heat will be determined in a future thermo-economic optimization.

Solar Thermochemical Hydrogen Production Research (STCH)

Energy Technology Data Exchange (ETDEWEB)

Perret, Robert [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

2011-05-01

Eight cycles in a coordinated set of projects for Solar Thermochemical Cycles for Hydrogen production (STCH) were self-evaluated for the DOE-EERE Fuel Cell Technologies Program at a Working Group Meeting on October 8 and 9, 2008. This document reports the initial selection process for development investment in STCH projects, the evaluation process meant to reduce the number of projects as a means to focus resources on development of a few most-likely-to-succeed efforts, the obstacles encountered in project inventory reduction and the outcomes of the evaluation process. Summary technical status of the projects under evaluation is reported and recommendations identified to improve future project planning and selection activities.

Improvement of Surface Properties of CP-Titanium by Thermo-Chemical Treatment (TCT) Process

International Nuclear Information System (INIS)

Jeong, Hyeon-Gyeong; Hur, Bo-Young; Lee, Dong-Geun; Lee, Yong-Tai; Yaskiv, O.

2011-01-01

The thermo-chemical treatment (TCT) process was applied to achieve surface hardening of CP titanium. The following three different surface modification conditions were tested so that the best surface hardening process could be selected:(a) PVD, (b) TCT+PVD, and (c) TCT+Aging+PVD. These specimens were tested and analyzed in terms of surface roughness, wear, friction coefficient, and the gradient of hardening from the surface of the matrix. The three test conditions were all beneficial to improve the surface hardness of CP titanium. Moreover, the TCT treated specimens, that is, (b) and (c), showed significantly improved surface hardness and low friction coefficients through the thickness up to 100um. This is due to the functionally gradient hardened surface improvement by the diffused interstitial elements. The hardened surface also showed improvement in bonding between the PVD and TCT surface, and this leads to improvement in wear resistance. However, TCT after aging treatment did not show much improvement in surface properties compared to TCT only. For the best surface hardening on CP titanium, TCT+PVD has advantages in surface durability and economics.

Calculated Pourbaix Diagrams of Cubic Perovskites for Water Splitting: Stability Against Corrosion

DEFF Research Database (Denmark)

Castelli, Ivano Eligio; Thygesen, Kristian Sommer; Jacobsen, Karsten Wedel

2014-01-01

We use density functional theory calculations to investigate the stability of cubic perovskites for photo-electrochemical water splitting taking both materials in their bulk crystal structure and dissolved phases into account. The method is validated through a detailed comparison of the calculated...

Thermochemical properties of the alkali hydroxides: A review

International Nuclear Information System (INIS)

Konings, R.J.M.; Cordfunke, E.H.P.

1989-01-01

The formation of volatile alkali hydroxides as a result of high-temperature steam corrosion plays an important role in nuclear technology. For the modeling of the volatilization processes, reliable thermodynamic data are required. In the present paper recent physico-chemical experiments by the authors will be discussed and the thermochemical properties of the alkali hydroxide series will be evaluated. (orig.)

Novel Fabrication of Biodegradable Superabsorbent Microspheres with Diffusion Barrier through Thermo-Chemical Modification and Their Potential Agriculture Applications for Water Holding and Sustained Release of Fertilizer.

Science.gov (United States)

Feng, Diejing; Bai, Bo; Wang, Honglun; Suo, Yourui

2017-07-26

Synergistic utilization of water and fertilizer has vital contribution to the modern production of agriculture. This work reports on a simple and facile strategy to prepare biodegradable yeast/sodium alginate/poly(vinyl alcohol) superabsorbent microspheres with a diffusion barrier merit by thermo-chemical modification route. The integrated performances, including water absorbency, water retention, water evaporation ratio, leaching loss control, sustained-release behaviors, and degradation in soil, were systematically investigated. The results revealed that the modified microspheres were a triumphant water and fertilizer manager to effectively hold water and control the unexpected leakage of fertilizer for sustained release. Therefore, this work provides a promising approach to ameliorate the utilization efficiency of water and fertilizer in potential agriculture applications.

Effective Heat and Mass Transport Properties of Anisotropic Porous Ceria for Solar Thermochemical Fuel Generation

Directory of Open Access Journals (Sweden)

Sophia Haussener

2012-01-01

Full Text Available High-resolution X-ray computed tomography is employed to obtain the exact 3D geometrical configuration of porous anisotropic ceria applied in solar-driven thermochemical cycles for splitting H2O and CO2. The tomography data are, in turn, used in direct pore-level numerical simulations for determining the morphological and effective heat/mass transport properties of porous ceria, namely: porosity, specific surface area, pore size distribution, extinction coefficient, thermal conductivity, convective heat transfer coefficient, permeability, Dupuit-Forchheimer coefficient, and tortuosity and residence time distributions. Tailored foam designs for enhanced transport properties are examined by means of adjusting morphologies of artificial ceria samples composed of bimodal distributed overlapping transparent spheres in an opaque medium.

Natural gas usage as a heat source for integrated SMR and thermochemical hydrogen production technologies

International Nuclear Information System (INIS)

Jaber, O.; Naterer, G.F.; Dincer, I.

2010-01-01

This paper investigates various usages of natural gas (NG) as an energy source for different hydrogen production technologies. A comparison is made between the different methods of hydrogen production, based on the total amount of natural gas needed to produce a specific quantity of hydrogen, carbon dioxide emissions per mole of hydrogen produced, water requirements per mole of hydrogen produced, and a cost sensitivity analysis that takes into account the fuel cost, carbon dioxide capture cost and a carbon tax. The methods examined are the copper-chlorine (Cu-Cl) thermochemical cycle, steam methane reforming (SMR) and a modified sulfur-iodine (S-I) thermochemical cycle. Also, an integrated Cu-Cl/SMR plant is examined to show the unique advantages of modifying existing SMR plants with new hydrogen production technology. The analysis shows that the thermochemical Cu-Cl cycle out-performs the other conventional methods with respect to fuel requirements, carbon dioxide emissions and total cost of production. (author)

Synfuels from fusion: producing hydrogen with the Tandem Mirror Reactor and thermochemical cycles

International Nuclear Information System (INIS)

Werner, R.W.; Ribe, F.L.

1981-01-01

This volume contains the following sections: (1) the Tandem Mirror fusion driver, (2) the Cauldron blanket module, (3) the flowing microsphere, (4) coupling the reactor to the process, (5) the thermochemical cycles, and (6) chemical reactors and process units

Enhanced Intermediate-Temperature CO2 Splitting Using Nonstoichiometric Ceria and Ceria-Zirconia

KAUST Repository

Zhao, Zhenlong

2017-08-24

CO2 splitting via thermo-chemical or reactive redox has emerged as a novel and promising carbon-neutral energy solution. Its performance depends critically on the properties of the oxygen carriers (OC). Ceria is recognized as one of the most promising OC candidates, because of its fast chemistry, high ionic diffusivity, and large oxygen storage capacity. The fundamental surface ion-incorporation pathways, along with the role of surface defects and the adsorbates remains largely unknown. This study presents a detailed kinetics study of CO2 splitting using CeO2 and Ce0.5Zr0.5O2 (CZO) in the temperature range 600-900℃. Given our interest in fuel-assisted reduction, we limit our study to relatively lower temperatures to avoid excessive sintering and the need for high temperature heat. Compared to what has been reported previously, we observe higher splitting kinetics, resulting from the utilization of fine particles and well-controlled experiments which ensure a surface-limited-process. The peak rates with CZO are 85.9 μmole g–1s–1 at 900℃ and 61.2 μmole g–1s–1 at 700℃, and those of CeO2 are 70.6 μmole g–1s–1 and 28.9 μmole g–1s–1. Kinetics models are developed to describe the ion incorporation dynamics, with consideration of CO2 activation and the charge transfer reactions. CO2 activation energy is found to be – 120 kJ mole-1 for CZO, half of that for CeO2, while CO desorption energetics is analogous among the two samples with the value of ~160 kJ mole-1. The charge-transfer process is found to be the rate-limiting step for CO2 splitting. The evolution of CO32- with surface Ce3+ is examined based on the modeled kinetics. We show that the concentration of CO32- varies with Ce3+ in a linear-flattened-decay pattern, resulting from a mismatch between the kinetics of the two reactions. Our study provides new insights into the significant role of the surface defects and adsorbates in determining the splitting kinetics.

TiO2 Nanotubes on Transparent Substrates: Control of Film Microstructure and Photoelectrochemical Water Splitting Performance

Directory of Open Access Journals (Sweden)

Matus Zelny

2018-01-01

Full Text Available Transfer of semiconductor thin films on transparent and or flexible substrates is a highly desirable process to enable photonic, catalytic, and sensing technologies. A promising approach to fabricate nanostructured TiO2 films on transparent substrates is self-ordering by anodizing of thin metal films on fluorine-doped tin oxide (FTO. Here, we report pulsed direct current (DC magnetron sputtering for the deposition of titanium thin films on conductive glass substrates at temperatures ranging from room temperature to 450 °C. We describe in detail the influence that deposition temperature has on mechanical, adhesion and microstructural properties of titanium film, as well as on the corresponding TiO2 nanotube array obtained after anodization and annealing. Finally, we measure the photoelectrochemical water splitting activity of different TiO2 nanotube samples showing that the film deposited at 150 °C has much higher activity correlating well with the lower crystallite size and the higher degree of self-organization observed in comparison with the nanotubes obtained at different temperatures. Importantly, the film showing higher water splitting activity does not have the best adhesion on glass substrate, highlighting an important trade-off for future optimization.

Nanocrystalline diamond on Si solar cells for direct photoelectrochemical water splitting

Czech Academy of Sciences Publication Activity Database

Ashcheulov, Petr; Kusko, M.; Fendrych, František; Poruba, A.; Taylor, Andrew; Jäger, Aleš; Fekete, Ladislav; Kraus, I.; Kratochvílová, Irena

2014-01-01

Roč. 211, č. 10 (2014), s. 2347-2352 ISSN 1862-6300 R&D Projects: GA ČR GA13-31783S; GA MŠk(CZ) LM2011026 EU Projects: European Commission(XE) 238201 - MATCON Institutional support: RVO:68378271 Keywords : boron-doped diamond * solar cell * heterostructure * water splitting Subject RIV: JI - Composite Materials Impact factor: 1.616, year: 2014

Synfuels from fusion: producing hydrogen with the Tandem Mirror Reactor and thermochemical cycles

Energy Technology Data Exchange (ETDEWEB)

Werner, R.W.; Ribe, F.L.

1981-01-21

This volume contains the following sections: (1) the Tandem Mirror fusion driver, (2) the Cauldron blanket module, (3) the flowing microsphere, (4) coupling the reactor to the process, (5) the thermochemical cycles, and (6) chemical reactors and process units. (MOW)

High-Efficiency Photochemical Water Splitting of CdZnS/CdZnSe Nanostructures

Directory of Open Access Journals (Sweden)

Chen-I Wang

2013-01-01

Full Text Available We have prepared and employed TiO2/CdZnS/CdZnSe electrodes for photochemical water splitting. The TiO2/CdZnS/CdZnSe electrodes consisting of sheet-like CdZnS/CdZnSe nanostructures (8–10 μm in length and 5–8 nm in width were prepared through chemical bath deposition on TiO2 substrates. The TiO2/CdZnS/CdZnSe electrodes have light absorption over the wavelength 400–700 nm and a band gap of 1.87 eV. Upon one sun illumination of 100 mW cm−2, the TiO2/CdZnS/CdZnSe electrodes provide a significant photocurrent density of 9.7 mA cm−2 at −0.9 V versus a saturated calomel electrode (SCE. Incident photon-to-current conversion efficiency (IPCE spectrum of the electrodes displays a maximum IPCE value of 80% at 500 nm. Moreover, the TiO2/CdZnS/CdZnSe electrodes prepared from three different batches provide a remarkable photon-to-hydrogen efficiency of 7.3 ± 0.1% (the rate of the photocatalytically produced H2 by water splitting is about 172.8 mmol·h−1·g−1, which is the most efficient quantum-dots-based photocatalysts used in solar water splitting.

Capabilities to Support Thermochemical Hydrogen Production Technology Development

Energy Technology Data Exchange (ETDEWEB)

Daniel M. Ginosar

2009-05-01

This report presents the results of a study to determine if Idaho National Laboratory (INL) has the skilled staff, instrumentation, specialized equipment, and facilities required to take on work in thermochemical research, development, and demonstration currently being performed by the Nuclear Hydrogen Initiative (NHI). This study outlines the beneficial collaborations between INL and other national laboratories, universities, and industries to strengthen INL's thermochemical efforts, which should be developed to achieve the goals of the NHI in the most expeditious, cost effective manner. Taking on this work supports INL's long-term strategy to maintain leadership in thermochemical cycle development. This report suggests a logical path forward to accomplish this transition.

Assessment of very high-temperature reactors in process applications. Appendix II. VHTR process heat application studies

International Nuclear Information System (INIS)

Jones, J.E.; Gambill, W.R.; Cooper, R.H.; Fox, E.C.; Fuller, L.C.; Littlefield, C.C.; Silverman, M.D.

1977-06-01

A critical review is presented of the technology and economics for coupling a very high-temperature gas-cooled reactor to a variety of process applications. It is concluded that nuclear steam reforming of light hydrocarbons for coal conversion could be a near-term alternative and that direct nuclear coal gasification could be a future consideration. Thermochemical water splitting appears to be more costly and its availability farther in the future than the coal-conversion systems. Nuclear steelmaking is competitive with the direct reduction of iron ore from conventional coal-conversion processes but not competitive with the reforming of natural gas at present gas prices. Nuclear process heat for petroleum refining, even with the necessary backup systems, is competitive with fossil energy sources. The processing with nuclear heat of oil shale and tar sands is of marginal economic importance. An analysis of peaking power applications using nuclear heat was also made. It is concluded that steam reforming methane for energy storage and production of peaking power is not a viable economic alternative, but that energy storage with a high-temperature heat transfer salt (HTS) is competitive with conventional peaking systems. An examination of the materials required in process heat exchangers is made

Field-Assisted Splitting of Pure Water Based on Deep-Sub-Debye-Length Nanogap Electrochemical Cells.

Science.gov (United States)

Wang, Yifei; Narayanan, S R; Wu, Wei

2017-08-22

Owing to the low conductivity of pure water, using an electrolyte is common for achieving efficient water electrolysis. In this paper, we have fundamentally broken through this common sense by using deep-sub-Debye-length nanogap electrochemical cells to achieve efficient electrolysis of pure water (without any added electrolyte) at room temperature. A field-assisted effect resulted from overlapped electrical double layers can greatly enhance water molecules ionization and mass transport, leading to electron-transfer limited reactions. We have named this process "virtual breakdown mechanism" (which is completely different from traditional mechanisms) that couples the two half-reactions together, greatly reducing the energy losses arising from ion transport. This fundamental discovery has been theoretically discussed in this paper and experimentally demonstrated in a group of electrochemical cells with nanogaps between two electrodes down to 37 nm. On the basis of our nanogap electrochemical cells, the electrolysis current density from pure water can be significantly larger than that from 1 mol/L sodium hydroxide solution, indicating the much better performance of pure water splitting as a potential for on-demand clean hydrogen production.

Biomass thermochemical gasification: Experimental studies and modeling

Science.gov (United States)

Kumar, Ajay

The overall goals of this research were to study the biomass thermochemical gasification using experimental and modeling techniques, and to evaluate the cost of industrial gas production and combined heat and power generation. This dissertation includes an extensive review of progresses in biomass thermochemical gasification. Product gases from biomass gasification can be converted to biopower, biofuels and chemicals. However, for its viable commercial applications, the study summarizes the technical challenges in the gasification and downstream processing of product gas. Corn stover and dried distillers grains with solubles (DDGS), a non-fermentable byproduct of ethanol production, were used as the biomass feedstocks. One of the objectives was to determine selected physical and chemical properties of corn stover related to thermochemical conversion. The parameters of the reaction kinetics for weight loss were obtained. The next objective was to investigate the effects of temperature, steam to biomass ratio and equivalence ratio on gas composition and efficiencies. DDGS gasification was performed on a lab-scale fluidized-bed gasifier with steam and air as fluidizing and oxidizing agents. Increasing the temperature resulted in increases in hydrogen and methane contents and efficiencies. A model was developed to simulate the performance of a lab-scale gasifier using Aspen Plus(TM) software. Mass balance, energy balance and minimization of Gibbs free energy were applied for the gasification to determine the product gas composition. The final objective was to optimize the process by maximizing the net energy efficiency, and to estimate the cost of industrial gas, and combined heat and power (CHP) at a biomass feedrate of 2000 kg/h. The selling price of gas was estimated to be 11.49/GJ for corn stover, and 13.08/GJ for DDGS. For CHP generation, the electrical and net efficiencies were 37 and 86%, respectively for corn stover, and 34 and 78%, respectively for DDGS. For

Ceria-based electrospun fibers for renewable fuel production via two-step thermal redox cycles for carbon dioxide splitting.

Science.gov (United States)

Gibbons, William T; Venstrom, Luke J; De Smith, Robert M; Davidson, Jane H; Jackson, Gregory S

2014-07-21

Zirconium-doped ceria (Ce(1-x)Zr(x)O2) was synthesized through a controlled electrospinning process as a promising approach to cost-effective, sinter-resistant material structures for high-temperature, solar-driven thermochemical redox cycles. To approximate a two-step redox cycle for solar fuel production, fibrous Ce(1-x)Zr(x)O2 with relatively low levels of Zr-doping (0 rates of O2 release during reduction and CO production during reoxidation and by assessing post-cycling fiber crystallite sizes and surface areas. Sintering increases with reduction temperature but occurs primarily along the fiber axes. Even after 108 redox cycles with reduction at 1400 °C and oxidation with CO2 at 800 °C, the fibers maintain their structure with surface areas of ∼0.3 m(2) g(-1), higher than those observed in the literature for other ceria-based structures operating at similarly high temperature conditions. Total CO production and peak production rate stabilize above 3.0 mL g(-1) and 13.0 mL min(-1) g(-1), respectively. The results show the potential for electrospun oxides as sinter-resistant material structures with adequate surface area to support rapid CO2 splitting in solar thermochemical redox cycles.

Red-Light-Driven Water Splitting by Au(Core)-CdS(Shell) Half-Cut Nanoegg with Heteroepitaxial Junction.

Science.gov (United States)

Naya, Shin-Ichi; Kume, Takahiro; Akashi, Ryo; Fujishima, Musashi; Tada, Hiroaki

2018-01-31

A key material for artificial photosynthesis including water splitting is heteronanostructured (HNS) photocatalysts. The photocatalytic activity depends on the geometry and dimension, and the quality of junctions between the components. Here we present a half-cut Au(core)-CdS(shell) (HC-Au@CdS) nanoegg as a new HNS plasmonic photocatalyst for water splitting. UV-light irradiation of Au nanoparticle (NP)-loaded ZnO (Au/ZnO) at 50 °C induces the selective deposition of hexagonal CdS on the Au surface of Au/ZnO with an epitaxial (EPI) relation of CdS{0001}/Au{111}. The subsequent selective dissolution of the ZnO support at room temperature yields HC-Au@CdS with the Au NP size and EPI junction (#) retained. Red-light irradiation (λ ex = 640 nm) of HC-Au@#CdS gives rise to continuous stoichiometric water splitting with an unprecedentedly high external quantum yield of 0.24%.

Iron-doped nickel oxide nanocrystals as highly efficient electrocatalysts for alkaline water splitting.

Science.gov (United States)

Fominykh, Ksenia; Chernev, Petko; Zaharieva, Ivelina; Sicklinger, Johannes; Stefanic, Goran; Döblinger, Markus; Müller, Alexander; Pokharel, Aneil; Böcklein, Sebastian; Scheu, Christina; Bein, Thomas; Fattakhova-Rohlfing, Dina

2015-05-26

Efficient electrochemical water splitting to hydrogen and oxygen is considered a promising technology to overcome our dependency on fossil fuels. Searching for novel catalytic materials for electrochemical oxygen generation is essential for improving the total efficiency of water splitting processes. We report the synthesis, structural characterization, and electrochemical performance in the oxygen evolution reaction of Fe-doped NiO nanocrystals. The facile solvothermal synthesis in tert-butanol leads to the formation of ultrasmall crystalline and highly dispersible FexNi1-xO nanoparticles with dopant concentrations of up to 20%. The increase in Fe content is accompanied by a decrease in particle size, resulting in nonagglomerated nanocrystals of 1.5-3.8 nm in size. The Fe content and composition of the nanoparticles are determined by X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy measurements, while Mössbauer and extended X-ray absorption fine structure analyses reveal a substitutional incorporation of Fe(III) into the NiO rock salt structure. The excellent dispersibility of the nanoparticles in ethanol allows for the preparation of homogeneous ca. 8 nm thin films with a smooth surface on various substrates. The turnover frequencies (TOF) of these films could be precisely calculated using a quartz crystal microbalance. Fe0.1Ni0.9O was found to have the highest electrocatalytic water oxidation activity in basic media with a TOF of 1.9 s(-1) at the overpotential of 300 mV. The current density of 10 mA cm(-2) is reached at an overpotential of 297 mV with a Tafel slope of 37 mV dec(-1). The extremely high catalytic activity, facile preparation, and low cost of the single crystalline FexNi1-xO nanoparticles make them very promising catalysts for the oxygen evolution reaction.

Nanosheet Supported Single-Metal Atom Bifunctional Catalyst for Overall Water Splitting.

Science.gov (United States)

Ling, Chongyi; Shi, Li; Ouyang, Yixin; Zeng, Xiao Cheng; Wang, Jinlan

2017-08-09

Nanosheet supported single-atom catalysts (SACs) can make full use of metal atoms and yet entail high selectivity and activity, and bifunctional catalysts can enable higher performance while lowering the cost than two separate unifunctional catalysts. Supported single-atom bifunctional catalysts are therefore of great economic interest and scientific importance. Here, on the basis of first-principles computations, we report a design of the first single-atom bifunctional eletrocatalyst, namely, isolated nickel atom supported on β 12 boron monolayer (Ni 1 /β 12 -BM), to achieve overall water splitting. This nanosheet supported SAC exhibits remarkable electrocatalytic performance with the computed overpotential for oxygen/hydrogen evolution reaction being just 0.40/0.06 V. The ab initio molecular dynamics simulation shows that the SAC can survive up to 800 K elevated temperature, while enacting a high energy barrier of 1.68 eV to prevent isolated Ni atoms from clustering. A viable experimental route for the synthesis of Ni 1 /β 12 -BM SAC is demonstrated from computer simulation. The desired nanosheet supported single-atom bifunctional catalysts not only show great potential for achieving overall water splitting but also offer cost-effective opportunities for advancing clean energy technology.

Efficient tungsten oxide/bismuth oxyiodide core/shell photoanode for photoelectrochemical water splitting

Science.gov (United States)

Ma, Haipeng; Zhang, Jing; Liu, Zhifeng

2017-11-01

The novel WO3 nanorods (NRs)/BiOI core/shell structure composite is used as an efficient photoanode applied in photoelectrochemical (PEC) water splitting for the first time. It is synthesized via facile hydrothermal method and, successive ionic layer adsorption and reaction (SILAR) process. This facile synthesis route can achieve uniform WO3/BiOI core/shell composite nanostructures and obtain varied BiOI morphologies simultaneously. The WO3 NRs/BiOI-20 composite exhibits enhanced PEC activity compared to pristine WO3 with a photocurrent density of 0.79 mA cm-2 measured at 0.8 V vs. RHE under AM 1.5G. This excellent performance benefits from the broader absorption spectrum and suppressed electron-hole recombination. This novel core/shell composite may provide insight in developing more efficient solar driven photoelectrodes.

TiO2/Cu2O composite based on TiO2 NTPC photoanode for photoelectrochemical (PEC) water splitting under visible light

KAUST Repository

Shi, Le

2015-01-01

in practice of water splitting with pure TiO2 material, one of the most popular semiconductor material used for photoelectrochemical water splitting, is still challenging. One dimensional TiO2 nanotubes is highly desired with its less recombination

Thermo-Chemical Conversion of Microwave Activated Biomass Mixtures

Science.gov (United States)

Barmina, I.; Kolmickovs, A.; Valdmanis, R.; Vostrikovs, S.; Zake, M.

2018-05-01

Thermo-chemical conversion of microwave activated wheat straw mixtures with wood or peat pellets is studied experimentally with the aim to provide more effective application of wheat straw for heat energy production. Microwave pre-processing of straw pellets is used to provide a partial decomposition of the main constituents of straw and to activate the thermo-chemical conversion of wheat straw mixtures with wood or peat pellets. The experimental study includes complex measurements of the elemental composition of biomass pellets (wheat straw, wood, peat), DTG analysis of their thermal degradation, FTIR analysis of the composition of combustible volatiles entering the combustor, the flame temperature, the heat output of the device and composition of the products by comparing these characteristics for mixtures with unprocessed and mw pre-treated straw pellets. The results of experimental study confirm that mw pre-processing of straw activates the thermal decomposition of mixtures providing enhanced formation of combustible volatiles. This leads to improvement of the combustion conditions in the flame reaction zone, completing thus the combustion of volatiles, increasing the flame temperature, the heat output from the device, the produced heat energy per mass of burned mixture and decreasing at the same time the mass fraction of unburned volatiles in the products.

Hydrogen production by water-splitting using heat supplied by a high-temperature reactor

International Nuclear Information System (INIS)

Courvoisier, P.; Rastoin, J.; Titiliette, Z.

1976-01-01

Some aspects of the use of heat of nuclear origin for the production of hydrogen by water-splitting are considered. General notions pertaining to the yield of chemical cycles are discussed and the heat balance corresponding to two specific processes is evaluated. The possibilities of high temperature reactors, with respect to the coolant temperature levels, are examined from the standpoint of core design and technology of some components. Furthermore, subject to a judicious selection of their characteristics, these reactors can lead to excellent use of nuclear fuel. The coupling of the nuclear reactor with the chemical plant by means of a secondary helium circuit gives rise to the design of an intermediate heat exchanger, which is an important component of the overall installation. (orig.) [de

Molecular concepts of water splitting. Nature's approach

Energy Technology Data Exchange (ETDEWEB)

Cox, Nicholas; Lubitz, Wolfgang [Max-Planck-Institut fuer Chemische Energiekonversion, Muelheim an der Ruhr (Germany)

2013-07-01

Based on studies of natural systems, much has also been learned concerning the design principles required for biomimetic catalysis of water splitting and hydrogen evolution. In summary, these include use of abundant and inexpensive metals, the effective protection of the active sites in functional environments, repair/replacement of active components in case of damage, and the optimization of reaction rates. Biomimetic chemistry aims to mimic all these features; many labs are working toward this goal by developing new approaches in the design and synthesis of such systems, encompassing not only the catalytic center, but also smart matrices and assembly via self-organization. More stable catalysts that do not require self-repair may be obtained from fully artificial (inorganic) catalytic systems that are totally different from the biological ones and only apply some basic principles learned from nature. Metals other than Mn/Ca, Fe, and Ni could be used (e.g. Co) in new ligand spheres and other matrices. For light harvesting, charge separation/stabilization, and the effective coupling of the oxidizing/reducing equivalents to the redox catalysts, different methods have been proposed - for example, covalently linked molecular donor-acceptor systems, photo-voltaic devices, semiconductor-based systems, and photoactive metal complexes. The aim of all these approaches is to develop catalytic systems that split water with sunlight into hydrogen and oxygen while displaying high efficiency and long-term stability. Such a system - either biological, biomimetic, or bioinspired - has the potential to be used on a large scale to produce 'solar fuels' (e.g. hydrogen or secondary products thereof). (orig.)

High-power pulsed plasma deposition of hematite photoanode for PEC water splitting

Czech Academy of Sciences Publication Activity Database

Kment, Š.; Hubička, Zdeněk; Krysa, J.; Olejníček, Jiří; Čada, Martin; Gregora, Ivan; Zlámal, M.; Brunclíková, Michaela; Remeš, Zdeněk; Liu, N.; Wang, L.; Kirchgeorg, R.; Lee, Ch.Y.; Schmuki, P.

2014-01-01

Roč. 230, Jul (2014), 8-14 ISSN 0920-5861 R&D Projects: GA ČR GAP108/12/2104; GA MŠk LH12043 Institutional support: RVO:68378271 Keywords : electrical properties * hematite * HiPIMS * hollow cathode plasma jet * photoelectrochemical water splitting * thin films Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.893, year: 2014

Thermochemical hydrogen production studies at LLNL: a status report

International Nuclear Information System (INIS)

Krikorian, O.H.

1982-01-01

Currently, studies are underway at the Lawrence Livermore National Laboratory (LLNL) on thermochemical hydrogen production based on magnetic fusion energy (MFE) and solar central receivers as heat sources. These areas of study were described earlier at the previous IEA Annex I Hydrogen Workshop (Juelich, West Germany, September 23-25, 1981), and a brief update will be given here. Some basic research has also been underway at LLNL on the electrolysis of water from fused phosphate salts, but there are no current results in that area, and the work is being terminated

An improved flux-split algorithm applied to hypersonic flows in chemical equilibrium

Science.gov (United States)

Palmer, Grant

1988-01-01

An explicit, finite-difference, shock-capturing numerical algorithm is presented and applied to hypersonic flows assumed to be in thermochemical equilibrium. Real-gas chemistry is either loosely coupled to the gasdynamics by way of a Gibbs free energy minimization package or fully coupled using species mass conservation equations with finite-rate chemical reactions. A scheme is developed that maintains stability in the explicit, finite-rate formulation while allowing relatively high time steps. The codes use flux vector splitting to difference the inviscid fluxes and employ real-gas corrections to viscosity and thermal conductivity. Numerical results are compared against existing ballistic range and flight data. Flows about complex geometries are also computed.

Thermochemical data for reactor materials

International Nuclear Information System (INIS)

Ronchi, C.; Turrini, F.

1990-01-01

This report describes a computer database of thermochemical properties of nuclear reactor materials to be used for source term calculations in reactor accident codes. In the first part, the structure and the content of the computer file is described. In the second part a set of thermochemical data is presented pertaining to chemical reactions occurring during severe nuclear reactor accidents and involving fuel (uranium dioxide), fission products and structural materials. These data are complementary to those collected in the databook recently published by Cordfunke and Potter after a study supported by the Commission of the European Communities. The present data were collected from review articles and databanks and follow a discussion on the uncertainties and errors involved in the calculation of complex chemical equilibria in the extrapolated temperature range

Ceramic carbon electrode-based anodes for use in the copper-chlorine thermochemical cycle

Energy Technology Data Exchange (ETDEWEB)

Ranganathan, S.; Easton, E.B. [Univ. of Ontario Inst. of Technology, Oshawa, ON (Canada). Faculty of Science

2009-07-01

A thermochemical cycle is a process by which water is decomposed into hydrogen and oxygen through a series of chemical reactions. The chemicals that are used in these reactions are regenerated and recycled during the process. Sol-gel chemistry is becoming more common for the synthesis of electrode materials. The sol-gel reaction can be conducted in the presence of a carbon black to form a ceramic carbon electrode (CCE). The resultant CCE structure contains electronically conductive carbon particle pathways that are bound together through the ceramic binder, which can also promote ion transport. The CCE structure also has a high active surface area and is chemically and thermally robust. This paper presented an investigation of CCE materials prepared using 3-aminopropyl trimethoxysilane. Several electrochemical experiments including cyclic voltammetry and electrochemical impedance spectroscopy were performed to characterize their suitability as anode electrode materials for use in the electrochemical step of the copper-chlorine thermochemical cycle. Subsequent experiments included the manipulation of the relative ratio of organosilane carbon precursors to gauge its impact on electrode properties and performance. An overview of the materials characterization and electrochemical measurements were also presented. Specifically, the paper presented the experiment with particular reference to the CCE preparation; electrochemical experiments; thermal analysis; and scanning electron microscopy. Results were also provided. These included TGA analysis; scanning electron microscopy analysis; electrochemical characterization; and anodic polarization. Characterization of these CCE material demonstrated that they had good thermal stability, could be used at high temperatures, and were therefore, very promising anode materials. 15 refs., 7 figs.

Lab-scale experiment of a closed thermochemical heat storage system including honeycomb heat exchanger

International Nuclear Information System (INIS)

Fopah-Lele, Armand; Rohde, Christian; Neumann, Karsten; Tietjen, Theo; Rönnebeck, Thomas; N'Tsoukpoe, Kokouvi Edem; Osterland, Thomas; Opel, Oliver

2016-01-01

A lab-scale thermochemical heat storage reactor was developed in the European project “thermal battery” to obtain information on the characteristics of a closed heat storage system, based on thermochemical reactions. The present type of storage is capable of re-using waste heat from cogeneration system to produce useful heat for space heating. The storage material used was SrBr 2 ·6H 2 O. Due to agglomeration or gel-like problems, a structural element was introduced to enhance vapour and heat transfer. Honeycomb heat exchanger was designed and tested. 13 dehydration-hydration cycles were studied under low-temperature conditions (material temperatures < 100 °C) for storage. Discharging was realized at water vapour pressure of about 42 mbar. Temperature evolution inside the reactor at different times and positions, chemical conversion, thermal power and overall efficiency were analysed for the selected cycles. Experimental system thermal capacity and efficiency of 65 kWh and 0.77 are respectively obtained with about 1 kg of SrBr 2 ·6H 2 O. Heat transfer fluid recovers heat at a short span of about 43 °C with an average of 22 °C during about 4 h, acceptable temperature for the human comfort (20 °C on day and 16 °C at night). System performances were obtained for a salt bed energy density of 213 kWh·m 3 . The overall heat transfer coefficient of the honeycomb heat exchanger has an average value of 147 W m −2  K −1 . Though promising results have been obtained, ameliorations need to be made, in order to make the closed thermochemical heat storage system competitive for space heating. - Highlights: • Lab-scale thermochemical heat storage is designed, constructed and tested. • The use of honeycomb heat exchanger as a heat and vapour process enhancement. • Closed system (1 kg SrBr 2 ·6H 2 O) able to give back 3/4 of initial thermal waste energy. • System storage capacity and thermal efficiency are respectively 65 kWh and 0.77. �

Study of thermochemical nonequilibrium flow in the radiative shock layer of the simulated atmosphere of Titan

International Nuclear Information System (INIS)

Koffi-Kpante, Kossi

1996-01-01

Inviscid flow of the N 2 -CH 4 -Ar gas mixture in thermochemical nonequilibrium has been studied. We have specially modelled the thermal and the chemical processes, such as vibrational excitation, dissociation, ionization and radiation which can occur in the hypersonic flows. Different vibrational models are tested and the effects of kinetic-vibration coupling modeling are studied on the flow-field properties. Therefore, the intensity of spontaneous emission of CN molecule from B 2 Σ + → X 2 Σ + electronic transition of the violet band, where Δν = 0 is computed. So, comparison is made between experimental and numerical results on: 1) The spontaneous emission of CN, 2) the rotational temperature of CN B state and 3) the vibrational temperature of CN B state. Because of the profiles of the measured intensity and the disagreement between numerical results and measurements, especially on the spontaneous emission and in the thermodynamic size, the inviscid flow and the unsteady boundary layer interaction study is made. Last, the thermal and the chemical processes models described in the first part of this thesis are used to compute the inviscid nonequilibrium flow around the Huygens probe. The equations system has been solved with a finite volume method, in with the fluxes have been split with Van-Leer methods. (author) [fr

Surface Passivation of GaN Nanowires for Enhanced Photoelectrochemical Water-Splitting.

Science.gov (United States)

Varadhan, Purushothaman; Fu, Hui-Chun; Priante, Davide; Retamal, Jose Ramon Duran; Zhao, Chao; Ebaid, Mohamed; Ng, Tien Khee; Ajia, Idirs; Mitra, Somak; Roqan, Iman S; Ooi, Boon S; He, Jr-Hau

2017-03-08

Hydrogen production via photoelectrochemical water-splitting is a key source of clean and sustainable energy. The use of one-dimensional nanostructures as photoelectrodes is desirable for photoelectrochemical water-splitting applications due to the ultralarge surface areas, lateral carrier extraction schemes, and superior light-harvesting capabilities. However, the unavoidable surface states of nanostructured materials create additional charge carrier trapping centers and energy barriers at the semiconductor-electrolyte interface, which severely reduce the solar-to-hydrogen conversion efficiency. In this work, we address the issue of surface states in GaN nanowire photoelectrodes by employing a simple and low-cost surface treatment method, which utilizes an organic thiol compound (i.e., 1,2-ethanedithiol). The surface-treated photocathode showed an enhanced photocurrent density of -31 mA/cm 2 at -0.2 V versus RHE with an incident photon-to-current conversion efficiency of 18.3%, whereas untreated nanowires yielded only 8.1% efficiency. Furthermore, the surface passivation provides enhanced photoelectrochemical stability as surface-treated nanowires retained ∼80% of their initial photocurrent value and produced 8000 μmol of gas molecules over 55 h at acidic conditions (pH ∼ 0), whereas the untreated nanowires demonstrated only passivation of nanostructured photoelectrodes for photoelectrochemical applications.

Salt splitting using ceramic membranes

Energy Technology Data Exchange (ETDEWEB)

Kurath, D.E. [Pacific Northwest National Lab., Richland, WA (United States)

1997-10-01

Many radioactive aqueous wastes in the DOE complex have high concentrations of sodium that can negatively affect waste treatment and disposal operations. Sodium can decrease the durability of waste forms such as glass and is the primary contributor to large disposal volumes. Waste treatment processes such as cesium ion exchange, sludge washing, and calcination are made less efficient and more expensive because of the high sodium concentrations. Pacific Northwest National Laboratory (PNNL) and Ceramatec Inc. (Salt Lake City UT) are developing an electrochemical salt splitting process based on inorganic ceramic sodium (Na), super-ionic conductor (NaSICON) membranes that shows promise for mitigating the impact of sodium. In this process, the waste is added to the anode compartment, and an electrical potential is applied to the cell. This drives sodium ions through the membrane, but the membrane rejects most other cations (e.g., Sr{sup +2}, Cs{sup +}). The charge balance in the anode compartment is maintained by generating H{sup +} from the electrolysis of water. The charge balance in the cathode is maintained by generating OH{sup {minus}}, either from the electrolysis of water or from oxygen and water using an oxygen cathode. The normal gaseous products of the electrolysis of water are oxygen at the anode and hydrogen at the cathode. Potentially flammable gas mixtures can be prevented by providing adequate volumes of a sweep gas, using an alternative reductant or destruction of the hydrogen as it is generated. As H{sup +} is generated in the anode compartment, the pH drops. The process may be operated with either an alkaline (pH>12) or an acidic anolyte (pH <1). The benefits of salt splitting using ceramic membranes are (1) waste volume reduction and reduced chemical procurement costs by recycling of NaOH; and (2) direct reduction of sodium in process streams, which enhances subsequent operations such as cesium ion exchange, calcination, and vitrification.

Environmental impacts of thermochemical biomass conversion. Final report

Energy Technology Data Exchange (ETDEWEB)

Elliott, D.C.; Hart, T.R.; Neuenschwander, G.G.; McKinney, M.D.; Norton, M.V.; Abrams, C.W. [Pacific Northwest Lab., Richland, WA (United States)

1995-06-01

Thermochemical conversion in this study is limited to fast pyrolysis, upgrading of fast pyrolysis oils, and gasification. Environmental impacts of all types were considered within the project, but primary emphasis was on discharges to the land, air, and water during and after the conversion processes. The project discussed here is divided into five task areas: (1) pyrolysis oil analysis; (2) hydrotreating of pyrolysis oil; (3) gas treatment systems for effluent minimization; (4) strategic analysis of regulatory requirements; and (5) support of the IEA Environmental Systems Activity. The pyrolysis oil task was aimed at understanding the oil contaminants and potential means for their removal. The hydrotreating task was undertaken to better define one potential means for both improving the quality of the oil but also removing contaminants from the oil. Within Task 3, analyses were done to evaluate the results of gasification product treatment systems. Task 4 was a review and collection of regulatory requirements which would be applicable to the subject processes. The IEA support task included input to and participation in the IEA Bioenergy activity which directly relates to the project subject. Each of these tasks is described along with the results. Conclusions and recommendations from the overall project are given.

Environmental impacts of thermochemical biomass conversion. Final report

International Nuclear Information System (INIS)

Elliott, D.C.; Hart, T.R.; Neuenschwander, G.G.; McKinney, M.D.; Norton, M.V.; Abrams, C.W.

1995-06-01

Thermochemical conversion in this study is limited to fast pyrolysis, upgrading of fast pyrolysis oils, and gasification. Environmental impacts of all types were considered within the project, but primary emphasis was on discharges to the land, air, and water during and after the conversion processes. The project discussed here is divided into five task areas: (1) pyrolysis oil analysis; (2) hydrotreating of pyrolysis oil; (3) gas treatment systems for effluent minimization; (4) strategic analysis of regulatory requirements; and (5) support of the IEA Environmental Systems Activity. The pyrolysis oil task was aimed at understanding the oil contaminants and potential means for their removal. The hydrotreating task was undertaken to better define one potential means for both improving the quality of the oil but also removing contaminants from the oil. Within Task 3, analyses were done to evaluate the results of gasification product treatment systems. Task 4 was a review and collection of regulatory requirements which would be applicable to the subject processes. The IEA support task included input to and participation in the IEA Bioenergy activity which directly relates to the project subject. Each of these tasks is described along with the results. Conclusions and recommendations from the overall project are given

Thermo-chemical simulation of a composite offshore vertical axis wind turbine blade

DEFF Research Database (Denmark)

Baran, Ismet; Tutum, Cem Celal; Hattel, Jesper Henri

2012-01-01

In the present study three dimensional steady state thermo-chemical simulation of a pultrusion process is investigated by using the finite element/nodal control volume (FE/NCV) technique. Pultrusion simulation of a composite having a C-shaped cross section is performed as a validation case. The o...

Thermo-chemical simultion of a composite offshore vertical axis wind turbine blade

NARCIS (Netherlands)

Baran, Ismet; Tutum, Cem Celal; Hattel, Jesper Henri

2012-01-01

In the present study three dimensional steady state thermo-chemical simulation of a pultrusion process is investigated by using the finite element/nodal control volume (FE/NCV) technique. Pultrusion simulation of a composite having a C-shaped cross section is performed as a validation case. The

Investigation into the cause of leak in the pipe of the corrosion test apparatus of IS process

International Nuclear Information System (INIS)

Tanaka, Nobuyuki; Furukawa, Tomohiro; Inagaki, Yoshiyuki; Suwa, Hirokazu

2008-12-01

The thermochemical water-splitting hydrogen production IS process utilizes corrosive chemicals such as sulfuric acid and hydriodic acid. Corrosion tests in IS process environments have been carried out to get the corrosion data of materials. In the corrosion test in 90wt% sulfuric acid at 400degC, the leak of sulfuric acid was observed in a pipe connected with a reflux condenser. The cause of the leakage is a significant knowledge for the operation of the test apparatus. Therefore the cause was investigated. A 1mm wide through hole was detected in the pipe around the welding bead. By visual observation after cutting the pipe, the wall thickness of the pipe became thin at the inside welding bead around the through hole. In addition, EMPA showed that the inhomogeneous distribution of the constituent elements of the pipe was observed around the through hole. For these reasons, it is estimated that the lowering of the corrosion resistance by the sensitization at the welding caused the leakage. (author)

Hydrogenated TiO2 nanotube photonic crystals for enhanced photoelectrochemical water splitting.

Science.gov (United States)

Meng, Ming; Zhou, Sihua; Yang, Lun; Gan, Zhixing; Liu, Kuili; Tian, Fengshou; Zhu, Yu; Li, ChunYang; Liu, Weifeng; Yuan, Honglei; Zhang, Yan

2018-04-02

We report the design, fabrication and characterization of novel TiO 2 nanotube photonic crystals with a crystalline core/disordered shell structure as well as substantial oxygen vacancies for photoelectrochemical (PEC) water splitting. The novel TiO 2 nanotube photonic crystals are fabricated by annealing of anodized TiO 2 nanotube photonic crystals in hydrogen atmosphere at various temperatures. The optimized novel TiO 2 nanotube photonic crystals produce a maximal photocurrent density of 2.2 mA cm -2 at 0.22 V versus Ag/AgCl, which is two times higher that of the TiO 2 nanotube photonic crystals annealed in air. Such significant PEC performance improvement can be ascribed to synergistic effects of the disordered surface layer and oxygen vacancies. The reduced band gap owing to the disordered surface layer and localized states induced by oxygen vacancies can enhance the efficient utilization of visible light. In addition, the disordered surface layer and substantial oxygen vacancies can promote the efficiency for separation and transport of the photogenerated carriers. This work may open up new opportunities for the design and construction of the high efficient and low-cost PEC water splitting system.

Solar energy conversion by photocatalytic overall water splitting

KAUST Repository

Takanabe, Kazuhiro

2015-07-04

Summary: Solar energy is abundant and renewable energy: however, extensive conversion of the solar energy can only be achieved by large-scale collection of solar flux. The technology that satisfies this requirement must be as simple as possible to reduce capital cost. Overall water splitting (OWS) by powder-form photocatalysts directly produces H2 as a chemical energy in a single reactor, which does not require any complicated parabolic mirrors and electronic devices. Because of its simplicity and low capital cost, it has tremendous potential to become the major technology of solar energy conversion. To achieve the OWS efficiently, the development of efficient photocatalysts is mandatory. The OWS hotocatalysis involves the electrocatalys is for both water reduction and oxidation on the surafce of photocatalysts, which is driven by particular semiconductors that absorb photons to generate excited carriers. Such photocatalysts must be designed to maximize the charge separation efficiency at the catalyst-semiconductor and semiconductor-electrolyte interface. In addition the low-overpotential electrocatalyts towards water redox reactions should be insensitive to the back-reaction of the produced H2 and O2 that produces H2O. In this presentation, some recent progress on the topic of the OWS in our group will be discussed.

Thermal energy storage using thermo-chemical heat pump

International Nuclear Information System (INIS)

Hamdan, M.A.; Rossides, S.D.; Haj Khalil, R.

2013-01-01

Highlights: ► Understanding of the performance of thermo chemical heat pump. ► Tool for storing thermal energy. ► Parameters that affect the amount of thermal stored energy. ► Lithium chloride has better effect on storing thermal energy. - Abstract: A theoretical study was performed to investigate the potential of storing thermal energy using a heat pump which is a thermo-chemical storage system consisting of water as sorbet, and sodium chloride as the sorbent. The effect of different parameters namely; the amount of vaporized water from the evaporator, the system initial temperature and the type of salt on the increase in temperature of the salt was investigated and hence on the performance of the thermo chemical heat pump. It was found that the performance of the heat pump improves with the initial system temperature, with the amount of water vaporized and with the water remaining in the system. Finally it was also found that lithium chloride salt has higher effect on the performance of the heat pump that of sodium chloride.

Performance analysis of an integrated energy storage and energy upgrade thermochemical solid–gas sorption system for seasonal storage of solar thermal energy

International Nuclear Information System (INIS)

Li, Tingxian; Wang, Ruzhu; Kiplagat, Jeremiah K.; Kang, YongTae

2013-01-01

An innovative dual-mode thermochemical sorption energy storage method is proposed for seasonal storage of solar thermal energy with little heat losses. During the charging phase in summer, solar thermal energy is stored in form of chemical bonds resulting from thermochemical decomposition process, which enables the stored energy to be kept several months at ambient temperature. During the discharging phase in winter, the stored thermal energy is released in the form of chemical reaction heat resulting from thermochemical synthesis process. Thermodynamic analysis showed that the advanced dual-mode thermochemical sorption energy storage is an effective method for the long-term seasonal storage of solar energy. A coefficient of performance (COP h ) of 0.6 and energy density higher than 1000 kJ/kg of salt can be attained from the proposed system. During the discharging phase at low ambient temperatures, the stored thermal energy can be upgraded by use of a solid–gas thermochemical sorption heat transformer cycle. The proposed thermochemical sorption energy storage has distinct advantages over the conventional sensible heat and latent heat storage, such as higher energy storage density, little heat losses, integrated energy storage and energy upgrade, and thus it can contribute to improve the seasonal utilization of solar thermal energy. - Highlights: ► A dual-mode solid thermochemical sorption is proposed for seasonal solar thermal energy storage. ► Energy upgrade techniques into the energy storage system are integrated. ► Performance of the proposed seasonal energy storage system is evaluated. ► Energy density and COP h from the proposed system are as high as 1043 kJ/kg of salt and 0.60, respectively

Experimental results of a 3 k Wh thermochemical heat storage module for space heating application

NARCIS (Netherlands)

Finck, C.J.; Henquet, E.M.R.; Soest, C.F.L. van; Oversloot, H.P.; Jong, A.J. de; Cuypers, R.; Spijker, J.C. van 't

2014-01-01

A 3 kWh thermochemical heat storage (TCS) module was built as part of an all-in house system implementation focusing on space heating application at a temperature level of 40 ºC and a temperature lift of 20 K. It has been tested and measurements showed a maximum water circuit temperature span

Charge Transfer Mechanism in Titanium-Doped Microporous Silica for Photocatalytic Water-Splitting Applications

Directory of Open Access Journals (Sweden)

Wendi Sapp

2016-02-01

Full Text Available Solar energy conversion into chemical form is possible using artificial means. One example of a highly-efficient fuel is solar energy used to split water into oxygen and hydrogen. Efficient photocatalytic water-splitting remains an open challenge for researchers across the globe. Despite significant progress, several aspects of the reaction, including the charge transfer mechanism, are not fully clear. Density functional theory combined with density matrix equations of motion were used to identify and characterize the charge transfer mechanism involved in the dissociation of water. A simulated porous silica substrate, using periodic boundary conditions, with Ti4+ ions embedded on the inner pore wall was found to contain electron and hole trap states that could facilitate a chemical reaction. A trap state was located within the silica substrate that lengthened relaxation time, which may favor a chemical reaction. A chemical reaction would have to occur within the window of photoexcitation; therefore, the existence of a trapping state may encourage a chemical reaction. This provides evidence that the silica substrate plays an integral part in the electron/hole dynamics of the system, leading to the conclusion that both components (photoactive materials and support of heterogeneous catalytic systems are important in optimization of catalytic efficiency.

DETECTION OF FLUX EMERGENCE, SPLITTING, MERGING, AND CANCELLATION OF NETWORK FIELD. I. SPLITTING AND MERGING

Energy Technology Data Exchange (ETDEWEB)

Iida, Y.; Yokoyama, T. [Department of Earth and Planetary Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Hagenaar, H. J. [Lockheed Martin Advanced Technology Center, Org. ADBS, Building 252, 3251 Hanover Street, Palo Alto, CA 94304 (United States)

2012-06-20

Frequencies of magnetic patch processes on the supergranule boundary, namely, flux emergence, splitting, merging, and cancellation, are investigated through automatic detection. We use a set of line-of-sight magnetograms taken by the Solar Optical Telescope (SOT) on board the Hinode satellite. We found 1636 positive patches and 1637 negative patches in the data set, whose time duration is 3.5 hr and field of view is 112'' Multiplication-Sign 112''. The total numbers of magnetic processes are as follows: 493 positive and 482 negative splittings, 536 positive and 535 negative mergings, 86 cancellations, and 3 emergences. The total numbers of emergence and cancellation are significantly smaller than those of splitting and merging. Further, the frequency dependence of the merging and splitting processes on the flux content are investigated. Merging has a weak dependence on the flux content with a power-law index of only 0.28. The timescale for splitting is found to be independent of the parent flux content before splitting, which corresponds to {approx}33 minutes. It is also found that patches split into any flux contents with the same probability. This splitting has a power-law distribution of the flux content with an index of -2 as a time-independent solution. These results support that the frequency distribution of the flux content in the analyzed flux range is rapidly maintained by merging and splitting, namely, surface processes. We suggest a model for frequency distributions of cancellation and emergence based on this idea.

Surface Passivation of GaN Nanowires for Enhanced Photoelectrochemical Water-Splitting

KAUST Repository

Varadhan, Purushothaman; Fu, Hui-chun; Priante, Davide; Duran Retamal, Jose Ramon; Zhao, Chao; Ebaid, Mohamed; Ng, Tien Khee; Ajia, Idris A.; Mitra, Somak; Roqan, Iman S.; Ooi, Boon S.; He, Jr-Hau

2017-01-01

Hydrogen production via photoelectrochemical water-splitting is a key source of clean and sustainable energy. The use of one-dimensional nanostructures as photoelectrodes is desirable for photoelectrochemical water-splitting applications due to the ultralarge surface areas, lateral carrier extraction schemes, and superior light-harvesting capabilities. However, the unavoidable surface states of nanostructured materials create additional charge carrier trapping centers and energy barriers at the semiconductor-electrolyte interface, which severely reduce the solar-to-hydrogen conversion efficiency. In this work, we address the issue of surface states in GaN nanowire photoelectrodes by employing a simple and low-cost surface treatment method, which utilizes an organic thiol compound (i.e., 1,2-ethanedithiol). The surface-treated photocathode showed an enhanced photocurrent density of −31 mA/cm at −0.2 V versus RHE with an incident photon-to-current conversion efficiency of 18.3%, whereas untreated nanowires yielded only 8.1% efficiency. Furthermore, the surface passivation provides enhanced photoelectrochemical stability as surface-treated nanowires retained ∼80% of their initial photocurrent value and produced 8000 μmol of gas molecules over 55 h at acidic conditions (pH ∼ 0), whereas the untreated nanowires demonstrated only <4 h of photoelectrochemical stability. These findings shed new light on the importance of surface passivation of nanostructured photoelectrodes for photoelectrochemical applications.

Surface Passivation of GaN Nanowires for Enhanced Photoelectrochemical Water-Splitting

KAUST Repository

Varadhan, Purushothaman

2017-02-08

Hydrogen production via photoelectrochemical water-splitting is a key source of clean and sustainable energy. The use of one-dimensional nanostructures as photoelectrodes is desirable for photoelectrochemical water-splitting applications due to the ultralarge surface areas, lateral carrier extraction schemes, and superior light-harvesting capabilities. However, the unavoidable surface states of nanostructured materials create additional charge carrier trapping centers and energy barriers at the semiconductor-electrolyte interface, which severely reduce the solar-to-hydrogen conversion efficiency. In this work, we address the issue of surface states in GaN nanowire photoelectrodes by employing a simple and low-cost surface treatment method, which utilizes an organic thiol compound (i.e., 1,2-ethanedithiol). The surface-treated photocathode showed an enhanced photocurrent density of −31 mA/cm at −0.2 V versus RHE with an incident photon-to-current conversion efficiency of 18.3%, whereas untreated nanowires yielded only 8.1% efficiency. Furthermore, the surface passivation provides enhanced photoelectrochemical stability as surface-treated nanowires retained ∼80% of their initial photocurrent value and produced 8000 μmol of gas molecules over 55 h at acidic conditions (pH ∼ 0), whereas the untreated nanowires demonstrated only <4 h of photoelectrochemical stability. These findings shed new light on the importance of surface passivation of nanostructured photoelectrodes for photoelectrochemical applications.

OPTIMIZED WTE CONVERSION OF MUNICIPAL SOLID WASTE IN SHANGHAI APPLYING THERMOCHEMICAL TECHNOLOGIES

OpenAIRE

Dai, Siyang

2016-01-01

Thermochemical technologies have been proven effective in treating municipal solid waste (MSW) for many years. China, with a rapid increase of MSW, plans to implement more environmental friendly ways to treat MSW than landfill, which treats about 79 % of total MSW currently. The aim of this master thesis was to find out a suitable thermochemical technology to treat MSW in Shanghai, China. Several different thermochemical technologies are compared in this thesis and plasma gasification was sel...

A general survey of the potential and the main issues associated with the sulfur-iodine thermochemical cycle for hydrogen production using nuclear heat

International Nuclear Information System (INIS)

Vitart, Xavier; Carles, Philippe; Anzieu, Pascal

2008-01-01

The thermochemical sulfur-iodine cycle is studied by CEA with the objective of massive hydrogen production using nuclear heat at high temperature. The challenge is to acquire by the end of 2008 the necessary decision elements, based on a scientific and validated approach, to choose the most promising way to produce hydrogen using a generation IV nuclear reactor. Amongst the thermochemical cycles, the sulfur-iodine process remains a very promising solution in matter of efficiency and cost, versus its main competitor, conventional electrolysis. The sulfur-iodine cycle is a very versatile process, which allows lot of variants for each section which can be adjusted in synergy in order to optimise the whole process. The main part of CEA's program is devoted to the study of the basic processes: new thermodynamics data acquisition, optimisation of water and iodine quantity, optimisation of temperature and pressure in each unit of the flow-sheet and survey of innovative solutions (membrane separations for instance). This program also includes optimisation of a detailed flow-sheet and studies for a hydrogen production plant (design, scale, first evaluations of safety issues and technico-economic questions). This program interacts strongly with other teams, in the framework of international collaborations (Europe, USA for instance). (author)

A general survey of the potential and the main issues associated with the sulfur-iodine thermochemical cycle for hydrogen production using nuclear heat

International Nuclear Information System (INIS)

Vitart, X.; Carles, P.; Anzieu, P.

2008-01-01

The thermochemical sulfur-iodine cycle is studied by CEA with the objective of massive hydrogen production using nuclear heat at high temperature. The challenge is to acquire by the end of 2008 the necessary decision elements, based on a scientific and validated approach, to choose the most promising way to produce hydrogen using a generation IV nuclear reactor. Amongst the thermochemical cycles, the sulfur-iodine process remains a very promising solution in matter of efficiency and cost, versus its main competitor, conventional electrolysis. The sulfur-iodine cycle is a very versatile process, which allows lot of variants for each section which can be adjusted in synergy in order to optimise the whole process. The main part of CEA's program is devoted to the study of the basic processes: new thermodynamics data acquisition, optimisation of water and iodine quantity, optimisation of temperature and pressure in each unit of the flow-sheet and survey of innovative solutions (membrane separations for instance). This program also includes optimisation of a detailed flow-sheet and studies for a hydrogen production plant (design, scale, first evaluations of safety issues and technico-economic questions). This program interacts strongly with other teams, in the framework of international collaborations (Europe, USA for instance). (authors)

Modeling of a split type air conditioner with integrated water heater

International Nuclear Information System (INIS)

Techarungpaisan, P.; Theerakulpisut, S.; Priprem, S.

2007-01-01

This paper presents a steady state simulation model to predict the performance of a small split type air conditioner with integrated water heater. The mathematical model consists of submodels of system components such as evaporator, condenser, compressor, capillary tube, receiver and water heater. These submodels were built based on fundamental principles of heat transfer, thermodynamics, fluid mechanics, empirical relationships and manufacturer's data as necessary. The model was coded into a simulation program and used to predict system parameters of interest such as hot water temperature, condenser exit air temperature, evaporator exit air temperature, mass flow rate of refrigerant, heat rejection in the condenser and cooling capacity of the system. The simulation results were compared with experimental data obtained from an experimental rig built for validating the mathematical model. It was found that the experimental and simulation results are in good agreement

Thermochemical Heat Storage: from Reaction Storage Density to System Storage Density

NARCIS (Netherlands)

Jong, A.J. de; Vliet, L.D. van; Hoegaerts, C.L.G.; Roelands, C.P.M.; Cuypers, R.

2016-01-01

Long-term and compact storage of solar energy is crucial for the eventual transition to a 100% renewable energy economy. For this, thermochemical materials provide a promising solution. The compactness of a long-term storage system is determined by the thermochemical reaction, operating conditions,

Thermochemically active iron titanium oxide materials

Energy Technology Data Exchange (ETDEWEB)

Coker, Eric Nicholas; Miller, James E.

2018-01-16

A thermal oxidation-reduction cycle is disclosed that uses iron titanium oxide as the reactive material. The cycle may be used for the thermal splitting of water and/or carbon dioxide to form hydrogen and/or carbon monoxide. The formed compounds may be used as syngas precursors to form fuels.

Regional Quasi-Three-Dimensional Unsaturated-Saturated Water Flow Model Based on a Vertical-Horizontal Splitting Concept

Directory of Open Access Journals (Sweden)

Yan Zhu

2016-05-01

Full Text Available Due to the high nonlinearity of the three-dimensional (3-D unsaturated-saturated water flow equation, using a fully 3-D numerical model is computationally expensive for large scale applications. A new unsaturated-saturated water flow model is developed in this paper based on the vertical/horizontal splitting (VHS concept to split the 3-D unsaturated-saturated Richards’ equation into a two-dimensional (2-D horizontal equation and a one-dimensional (1-D vertical equation. The horizontal plane of average head gradient in the triangular prism element is derived to split the 3-D equation into the 2-D equation. The lateral flow in the horizontal plane of average head gradient represented by the 2-D equation is then calculated by the water balance method. The 1-D vertical equation is discretized by the finite difference method. The two equations are solved simultaneously by coupling them into a unified nonlinear system with a single matrix. Three synthetic cases are used to evaluate the developed model code by comparing the modeling results with those of Hydrus1D, SWMS2D and FEFLOW. We further apply the model to regional-scale modeling to simulate groundwater table fluctuations for assessing the model applicability in complex conditions. The proposed modeling method is found to be accurate with respect to measurements.

Oxygen permeation and thermo-chemical stability of oxygen separation membrane materials for the oxyfuel process

Energy Technology Data Exchange (ETDEWEB)

Ellett, Anna Judith

2009-07-01

The reduction of CO{sub 2} emissions, generally held to be one of the most significant contributors to global warming, is a major technological issue. CO{sub 2} Capture and Storage (CCS) techniques applied to large stationary sources such as coal-fired power plants could efficiently contribute to the global carbon mitigation effort. The oxyfuel process, which consists in the burning of coal in an oxygen-rich atmosphere to produce a flue gas highly concentrated in CO{sub 2}, is a technology considered for zero CO{sub 2} emission coal-fired power plants. The production of this O{sub 2}-rich combustion gas from air can be carried out using high purity oxygen separation membranes. Some of the most promising materials for this application are mixed ionic-electronic conducting (MIEC) materials with perovskite and K{sub 2}NiF{sub 4} perovskite-related structures. The present work examines the selection of La{sub 0.58}Sr{sub 0.4}Co{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}} (LSCF58), La{sub 2}NiO{sub 4+{delta}}, Pr{sub 0.58}Sr{sub 0.4}Co{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}} (PSCF58) and Ba{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 0.2}O{sub 3-{delta}} (BSCF50) as membrane materials for the separation of O{sub 2} and N{sub 2} in the framework of the oxyfuel process with flue gas recycling. Annealing experiments were carried out on pellets exposed to CO{sub 2}, water vapour, O{sub 2} and Cr{sub 2}O{sub 3} in order to determine the thermo-chemical resistance to the atmospheres and the high temperature conditions present during membrane operation in a coal-fired power plant. The degradation of their microstructure was investigated using Scanning Electron Microscopy (SEM) in combination with electron dispersive spectroscopy (EDS) as well as X-Ray Diffraction (XRD). Also, the oxygen permeation fluxes of selected membranes were investigated as a function of temperature. The membrane materials selected were characterised using thermo-analytical techniques such as precision thermogravimetric

Balance and saving of GHG emissions in thermochemical biorefineries

International Nuclear Information System (INIS)

Haro, Pedro; Aracil, Cristina; Vidal-Barrero, Fernando; Ollero, Pedro

2015-01-01

Highlights: • A simplified methodology for the balance and saving of GHG emissions is provided. • The GHG balance has a physical meaning and does not depend on the fossil reference. • The GHG saving depends on regulation of energy carriers. • The impact of Bio-CCS incorporation and multiproduction is analyzed. • The co-production of chemicals needs to be included in future regulation. - Abstract: In this study, a simplified methodology for the calculation of the balance of greenhouse gas (GHG) emissions and corresponding saving compared with the fossil reference is presented. The proposed methodology allows the estimation of the anthropogenic GHG emissions of thermochemical biorefineries (net emitted to the atmosphere). In the calculation of the GHG balance, all relevant factors have been identified and analyzed including multiproduction, emissions from biogenic carbon capture and storage (Bio-CCS), co-feeding of fossil fuels (secondary feedstock) and possible carbon storage in biomass-derived products (chemicals). Therefore, it is possible to calculate the balance of GHG emissions of a hypothetical thermochemical biorefinery considering different alternatives of land-use, biomass feedstock, co-feeding of fossil fuels, Bio-CCS incorporation and final use of the products. The comparison of the estimated GHG balance with the corresponding fossil reference for each product is of special relevance in the methodology since it is the parameter used in European regulation for the fulfillment of sustainability criteria in biomass-derived fuels and liquids. The proposed methodology is tested using a previously assessed set of different process concepts of thermochemical biorefineries (techno-economic analysis). The resulting GHG balance and saving are analyzed to identify uncertainties and provide recommendations for future regulation. In all process concepts, the GHG savings are above the minimum requirement of GHG emissions for 2018. In the case of incorporating

Analysis of mobile fronthaul bandwidth and wireless transmission performance in split-PHY processing architecture.

Science.gov (United States)

Miyamoto, Kenji; Kuwano, Shigeru; Terada, Jun; Otaka, Akihiro

2016-01-25

We analyze the mobile fronthaul (MFH) bandwidth and the wireless transmission performance in the split-PHY processing (SPP) architecture, which redefines the functional split of centralized/cloud RAN (C-RAN) while preserving high wireless coordinated multi-point (CoMP) transmission/reception performance. The SPP architecture splits the base stations (BS) functions between wireless channel coding/decoding and wireless modulation/demodulation, and employs its own CoMP joint transmission and reception schemes. Simulation results show that the SPP architecture reduces the MFH bandwidth by up to 97% from conventional C-RAN while matching the wireless bit error rate (BER) performance of conventional C-RAN in uplink joint reception with only 2-dB signal to noise ratio (SNR) penalty.

Overall Water Splitting with Room-Temperature Synthesized NiFe Oxyfluoride Nanoporous Films

Energy Technology Data Exchange (ETDEWEB)

Liang, Kun; Guo, Limin; Marcus, Kyle; Zhang, Shoufeng [Laboratory; Yang, Zhenzhong; Perea, Daniel E.; Zhou, Le; Du, Yingge; Yang, Yang

2017-11-07

Freestanding and lightweight thin-films were rationally designed to serve as robust electrodes for renewable energy applications. A facile and scalable nanomanufacturing process was developed to fabricate these transformative thin-film electrodes (iron group mixed oxides) that exhibit a nanoporous structure and controllable composition. More specifically, electrodeposition and anodic treatments were employed to produce freestanding and lightweight metal oxides nanoporous layers (NPL). These NPL can be directly used as flexible and additive-free electrodes for renewable energy generation (water splitting) and storage (supercapacitor) applications without requiring binders and current collector and other additives. Significantly enhanced electrochemical performance was achieved due to the unique merits of the NPL: i) highly porous structure considerably increases the electrode/electrolyte interface, which facilitate electrochemical reactions; ii) NPL substantially increase the number of active sites that are favorable in electrochemical reactions; iii) residual metal network within the NPL forms a conductive framework, drastically improving electrode strength, flexibility and conductivity.

New cubic perovskites for one- and two-photon water splitting using the computational materials repository

DEFF Research Database (Denmark)

Castelli, Ivano Eligio; Landis, David; Thygesen, Kristian Sommer

2012-01-01

screening of around 19 000 oxides, oxynitrides, oxysulfides, oxyfluorides, and oxyfluoronitrides in the cubic perovskite structure with PEC applications in mind. We address three main applications: light absorbers for one- and two-photon water splitting and high-stability transparent shields to protect...

High-efficiency p-n junction oxide photoelectrodes for photoelectrochemical water splitting.

Science.gov (United States)

Liu, Zhifeng; Yan, Lu

2016-11-16

Development of all oxide p-n junctions makes a significant advancement in photoelectrode catalysis functional materials. In this article, we report the preparation of TiO 2 nanorod (NR)/Cu 2 O photoanodes via a simple hydrothermal method followed by an electrochemical deposition process. This facile synthesis route can simultaneously achieve uniform TiO 2 NR/Cu 2 O composite nanostructures and obtain varied amounts of Cu 2 O by controlling the deposition time. The photocurrent density of TiO 2 NR/Cu 2 O heterojunction photoanodes enhanced the photocatalytic activity with a photocurrent density of 5.25 mA cm -2 at 1.23 V versus RHE compared to pristine TiO 2 NR photoanodes under the same conditions. It is demonstrated that the presence of Cu 2 O has played an important role in expanding the spectral response region and reducing the photogenerated charge recombination rate. More importantly, the results provide new insights into the performance of all oxide p-n junctions as photoanodes for PEC water splitting.

Thermochemical hydrolysis of macroalgae Ulva for biorefinery: Taguchi robust design method

Science.gov (United States)

Jiang, Rui; Linzon, Yoav; Vitkin, Edward; Yakhini, Zohar; Chudnovsky, Alexandra; Golberg, Alexander

2016-06-01

Understanding the impact of all process parameters on the efficiency of biomass hydrolysis and on the final yield of products is critical to biorefinery design. Using Taguchi orthogonal arrays experimental design and Partial Least Square Regression, we investigated the impact of change and the comparative significance of thermochemical process temperature, treatment time, %Acid and %Solid load on carbohydrates release from green macroalgae from Ulva genus, a promising biorefinery feedstock. The average density of hydrolysate was determined using a new microelectromechanical optical resonator mass sensor. In addition, using Flux Balance Analysis techniques, we compared the potential fermentation yields of these hydrolysate products using metabolic models of Escherichia coli, Saccharomyces cerevisiae wild type, Saccharomyces cerevisiae RN1016 with xylose isomerase and Clostridium acetobutylicum. We found that %Acid plays the most significant role and treatment time the least significant role in affecting the monosaccharaides released from Ulva biomass. We also found that within the tested range of parameters, hydrolysis with 121 °C, 30 min 2% Acid, 15% Solids could lead to the highest yields of conversion: 54.134-57.500 gr ethanol kg-1 Ulva dry weight by S. cerevisiae RN1016 with xylose isomerase. Our results support optimized marine algae utilization process design and will enable smart energy harvesting by thermochemical hydrolysis.

Thermochemical hydrolysis of macroalgae Ulva for biorefinery: Taguchi robust design method.

Science.gov (United States)

Jiang, Rui; Linzon, Yoav; Vitkin, Edward; Yakhini, Zohar; Chudnovsky, Alexandra; Golberg, Alexander

2016-06-13

Understanding the impact of all process parameters on the efficiency of biomass hydrolysis and on the final yield of products is critical to biorefinery design. Using Taguchi orthogonal arrays experimental design and Partial Least Square Regression, we investigated the impact of change and the comparative significance of thermochemical process temperature, treatment time, %Acid and %Solid load on carbohydrates release from green macroalgae from Ulva genus, a promising biorefinery feedstock. The average density of hydrolysate was determined using a new microelectromechanical optical resonator mass sensor. In addition, using Flux Balance Analysis techniques, we compared the potential fermentation yields of these hydrolysate products using metabolic models of Escherichia coli, Saccharomyces cerevisiae wild type, Saccharomyces cerevisiae RN1016 with xylose isomerase and Clostridium acetobutylicum. We found that %Acid plays the most significant role and treatment time the least significant role in affecting the monosaccharaides released from Ulva biomass. We also found that within the tested range of parameters, hydrolysis with 121 °C, 30 min 2% Acid, 15% Solids could lead to the highest yields of conversion: 54.134-57.500 gr ethanol kg(-1) Ulva dry weight by S. cerevisiae RN1016 with xylose isomerase. Our results support optimized marine algae utilization process design and will enable smart energy harvesting by thermochemical hydrolysis.

Supercritical Fluids Processing of Biomass to Chemicals and Fuels

Energy Technology Data Exchange (ETDEWEB)

Olson, Norman K. [Iowa State Univ., Ames, IA (United States)

2011-09-28

The main objective of this project is to develop and/or enhance cost-effective methodologies for converting biomass into a wide variety of chemicals, fuels, and products using supercritical fluids. Supercritical fluids will be used both to perform reactions of biomass to chemicals and products as well as to perform extractions/separations of bio-based chemicals from non-homogeneous mixtures. This work supports the Biomass Program’s Thermochemical Platform Goals. Supercritical fluids are a thermochemical approach to processing biomass that, while aligned with the Biomass Program’s interests in gasification and pyrolysis, offer the potential for more precise and controllable reactions. Indeed, the literature with respect to the use of water as a supercritical fluid frequently refers to “supercritical water gasification” or “supercritical water pyrolysis.”

Static Thermochemical Model of COREX Melter Gasifier

Science.gov (United States)

Srishilan, C.; Shukla, Ajay Kumar

2018-02-01

COREX is one of the commercial smelting reduction processes. It uses the finer size ore and semi-soft coal instead of metallurgical coke to produce hot metal from iron ore. The use of top gas with high calorific value as a by-product export gas makes the process economical and green. The predictive thermochemical model of the COREX process presented here enables rapid computation of process parameters such as (1) required amount of ore, coal, and flux; (2) amount of slag and gas generated; and (3) gas compositions (based on the raw material and desired hot metal quality). The model helps in predicting the variations in process parameters with respect to the (1) degree of metallization and (2) post-combustion ratio for given raw material conditions. In general reduction in coal, flux, and oxygen, the requirement is concomitant with an increase in the degree of metallization and post-combustion ratio. The model reported here has been benchmarked using industrial data obtained from the JSW Steel Plant, India.

Nanostructured hematite thin films for photoelectrochemical water splitting

Science.gov (United States)

Maabong, Kelebogile; Machatine, Augusto G. J.; Mwankemwa, Benard S.; Braun, Artur; Bora, Debajeet K.; Toth, Rita; Diale, Mmantsae

2018-04-01

Nanostructured hematite thin films prepared by dip coating technique were investigated for their photoelectrochemical activity for generation of hydrogen from water splitting. Structural, morphological and optical analyses of the doped/undoped films were performed by X-ray diffraction, high resolution field emission-scanning electron microscopy, UV-vis spectrophotometry and Raman spectroscopy. The photoelectrochemical measurements of the films showed enhanced photoresponse and cathodic shift of the onset potential upon Ti doping indicating improved transfer of photoholes at the semiconductor-electrolyte interface. Films doped with 1 at% Ti produced 0.72 mA/cm2 at 1.23 V vs RHE which is 2 times higher than current density for the pure film (0.30 mA/cm2, at 1.23 V vs RHE). Gas chromatography analysis of the films also showed enhanced hydrogen evolution at 1 at% Ti with respect to pure film.

Estimation of thermochemical behavior of spallation products in mercury target

International Nuclear Information System (INIS)

Kobayashi, Kaoru; Kaminaga, Masanori; Haga, Katsuhiro; Kinoshita, Hidetaka; Aso, Tomokazu; Teshigawara, Makoto; Hino, Ryutaro

2002-02-01

In order to examine the radiation safety of a spallation mercury target system, especially source term evaluation, it is necessary to clarify the chemical forms of spallation products generated by spallation reaction with proton beam. As for the chemical forms of spallation products in mercury that involves large amounts of spallation products, these forms were estimated by using the binary phase diagrams and the thermochemical equilibrium calculation based on the amounts of spallation product. Calculation results showed that the mercury would dissolve Al, As, B, Be, Bi, C, Co, Cr, Fe, Ga, Ge, Ir, Mo, Nb, Os, Re, Ru, Sb, Si, Ta, Tc, V and W in the element state, and Ag, Au, Ba, Br, Ca, Cd, Ce, Cl, Cs, Cu, Dy, Er, Eu, F, Gd, Hf, Ho, I, In, K, La, Li, Lu, Mg, Mn, Na, Nd, Ni, O, Pb, Pd, Pr, Pt, Rb, Rh, S, Sc, Se, Sm, Sn, Sr, Tb, Te, Ti, Tl, Tm, Y, Yb, Zn and Zr in the form of inorganic mercury compounds. As for As, Be, Co, Cr, Fe, Ge, Ir, Mo, Nb, Os, Pt, Re, Ru, Se, Ta, V, W and Zr, precipitation could be occurred when increasing the amounts of spallation products with operation time of the spallation target system. On the other hand, beryllium-7 (Be-7), which is produced by spallation reaction of oxygen in the cooling water of a safety hull, becomes the main factor of the external exposure to maintain the cooling loop. Based on the thermochemical equilibrium calculation to Be-H 2 O binary system, the chemical forms of Be in the cooling water were estimated. Then the Be could exist in the form of cations such as BeOH + , BeO + and Be 2+ under the condition of less than 10 -8 of the Be mole fraction in the cooling water. (author)

New method for the determination of metolachlor and buprofezin in natural water using orthophthalaldehyde by thermochemically-induced fluorescence derivatization (TIFD).

Science.gov (United States)

Mendy, Alphonse; Thiaré, Diène Diégane; Sambou, Souleymane; Khonté, Abdourahmane; Coly, Atanasse; Gaye-Seye, Mame Diabou; Delattre, François; Tine, Alphonse

2016-05-01

Herbicide metolachlor (MET) and insecticide buprofezin (BUP) were determined in natural waters by means of a newly-developed, simple and sensitive thermochemically-induced fluorescence derivatization (TIFD) method. The TIFD approach is based on the thermolysis transformation of naturally non-fluorescent pesticides into fluorescent complex O-phthalaldehyde-thermoproduct(s) in water at 70°C for MET and at 80°C for BUP. The TIFD method was optimized with respect to the temperature, pH, complex formation kinetic and pesticides concentrations. The limit of detection (LOD=0.8ngmL(-1) for MET and 3.0ngmL(-1) for BUP) and quantification (LOQ=2.6ngmL(-1) for MET and 9.5 ngmL(-1) for BUP) values were low, and the relative standard deviation (RSD) values were small (between 1.2% and 1.8%), which indicates a good analytical sensitivity and a great repeatability of TIFD method. Recovery studies were performed on spiked well, sea and draining waters samples collected in the Niayes area by using the solid phase extraction (SPE) procedure. Satisfactory recovery results (84-118%) were obtained for the determination of MET and BUP in these natural waters. Copyright © 2016 Elsevier B.V. All rights reserved.

Initiating events identification of the IS process using the master logic diagram

International Nuclear Information System (INIS)

Cho, Nam Chul; Jae, Moo Sung; Yang, Joon Eon

2005-01-01

Hydrogen is very attractive as a future secondary energy carrier considering environmental problems. It is important to produce hydrogen from water by use of carbon free primary energy source. The thermochemical water decomposition cycle is one of the methods for the hydrogen production process from water. Japan Atomic Energy Research Institute (JAERI) has been carrying out an R and D on the IS (iodine.sulfur) process that was first proposed by GA (General Atomic Co.) focusing on demonstration the 'closed-cycle' continuous hydrogen production on developing a feasible and efficient scheme for the HI processing, and on screening and/or developing materials of construction to be used in the corrosive process environment. The successful continuous operation of the IS-process was demonstrated and this process is one of the thermochemical processes, which is the closest to being industrialized. Currently, Korea has also started a research about the IS process and the construction of the IS process system is planned. In this study, for risk analysis of the IS process, initiating events of the IS process are identified by using the Master Logic Diagram (MLD) that is method for initiating event identification

Plasmon enhanced water splitting mediated by hybrid bimetallic Au-Ag core-shell nanostructures.

Science.gov (United States)

Erwin, William R; Coppola, Andrew; Zarick, Holly F; Arora, Poorva; Miller, Kevin J; Bardhan, Rizia

2014-11-07

In this work, we employed wet chemically synthesized bimetallic Au-Ag core-shell nanostructures (Au-AgNSs) to enhance the photocurrent density of mesoporous TiO2 for water splitting and we compared the results with monometallic Au nanoparticles (AuNPs). While Au-AgNSs incorporated photoanodes give rise to 14× enhancement in incident photon to charge carrier efficiency, AuNPs embedded photoanodes result in 6× enhancement. By varying nanoparticle concentration in the photoanodes, we observed ∼245× less Au-AgNSs are required relative to AuNPs to generate similar photocurrent enhancement for solar fuel conversion. Power-dependent measurements of Au-AgNSs and AuNPs showed a first order dependence to incident light intensity, relative to half-order dependence for TiO2 only photoanodes. This indicated that plasmonic nanostructures enhance charge carriers formed on the surface of the TiO2 which effectively participate in photochemical reactions. Our experiments and simulations suggest the enhanced near-field, far-field, and multipolar resonances of Au-AgNSs facilitating broadband absorption of solar radiation collectively gives rise to their superior performance in water splitting.

Evaluation of the Relative Merits of Herbaceous and Woody Crops for Use in Tunable Thermochemical Processing

Energy Technology Data Exchange (ETDEWEB)

Park, Joon-Hyun [Ceres, Inc., Thousand Oaks, CA (United States); Martinalbo, Ilya [Choren USA, LLC, Houston, TX (United States)

2011-12-01

This report summarizes the work and findings of the grant work conducted from January 2009 until September 2011 under the collaboration between Ceres, Inc. and Choren USA, LLC. This DOE-funded project involves a head-to-head comparison of two types of dedicated energy crops in the context of a commercial gasification conversion process. The main goal of the project was to gain a better understanding of the differences in feedstock composition between herbaceous and woody species, and how these differences may impact a commercial gasification process. In this work, switchgrass was employed as a model herbaceous energy crop, and willow as a model short-rotation woody crop. Both crops are species native to the U.S. with significant potential to contribute to U.S. goals for renewable liquid fuel production, as outlined in the DOE Billion Ton Update (http://www1.eere.energy.gov/biomass/billion_ton_update.html, 2011). In some areas of the U.S., switching between woody and herbaceous feedstocks or blending of the two may be necessary to keep a large-scale gasifier operating near capacity year round. Based on laboratory tests and process simulations it has been successfully shown that suitable high yielding switchgrass and willow varieties exist that meet the feedstock specifications for large scale entrained flow biomass gasification. This data provides the foundation for better understanding how to use both materials in thermochemical processes. It has been shown that both switchgrass and willow varieties have comparable ranges of higher heating value, BTU content and indistinguishable hydrogen/carbon ratios. Benefits of switchgrass, and other herbaceous feedstocks, include its low moisture content, which reduce energy inputs and costs for drying feedstock. Compared to the typical feedstock currently being used in the Carbo-V® process, switchgrass has a higher ash content, combined with a lower ash melting temperature. Whether or not this may cause inefficiencies in the

Simple nonempirical calculations of the zero-field splitting in transition metal systems: I. The Ni(II)-water complexes

International Nuclear Information System (INIS)

Ribbing, C.; Odelius, M.; Laaksonen, A.; Kowalewski, J.; Roos, B.

1990-01-01

A simple nonempirical scheme is presented for calculating the splittings of ground state multiplets (the zero-field splitting) is transition metal complexes. The method employs single reference, single excitation CI calculations based on open-shell RHF. The spin-orbit coupling is described using an effective one-electron, one-center operators. The method is applied to the triplet state Ni(II) complexes with one to six water molecules. the validity of the second-order perturbation theory approach and of the spin-Hamiltonian formalism is found to be limited to slightly distorted octahedral systems. Generally, small changes in the geometries of the complexes are found to cause substantial variations of the splitting pattern

A hybrid HTGR system producing electricity, hydrogen and such other products as water demanded in the Middle East

Energy Technology Data Exchange (ETDEWEB)

Yan, X., E-mail: yan.xing@jaea.go.jp; Noguchi, H.; Sato, H.; Tachibana, Y.; Kunitomi, K.; Hino, R.

2014-05-01

Alternative energy products are being considered by the Middle East countries for both consumption and export. Electricity, water, and hydrogen produced not from oil and gas are amongst those desirable. A hybrid nuclear production system, GTHTR300C, under development in JAEA can achieve this regional strategic goal. The system is based on a 600 MWt HTGR and equipped to cogenerate electricity by gas turbine and seawater desalination by using only the nuclear plant waste heat. Hydrogen is produced via a thermochemical water-splitting process driven by the reactor's 950 °C heat. Additionally process steam may be produced for industrial uses. An example is shown of manufacturing soda ash, an internationally traded commodity, from using the steam produced and the brine discharged from desalination. The nuclear reactor satisfies nearly all energy requirements for the hybrid generations without emitting CO{sub 2}. The passive safety of the reactor as described in the paper permits proximity of siting the reactor with the production facilities to enhance energy transmission. Production flowsheet of the GTHTR300C is given for up to 300 MWe electricity, 58 t/day hydrogen, 56,000 m{sup 3}/day potable water, 3500 t/day steam, and 1000 t/day soda ash. The production thermal efficiency reaches 88%.

WEATHERING PROCESS IN EOCENE FLYSCH IN REGION OF SPLIT (CROATIA

Directory of Open Access Journals (Sweden)

Predrag Miščević

2001-12-01

Full Text Available The Eocene flysh in the region of Split (Dalmatia, Croatia is char¬acterized by the presence of layers with different characteristics. It mainly includes thin-layered marls, clayey marls, calcareous marls, clastic lay¬ered limestones, calcarenites and breccias. Those parts that can be de¬scribed as the soft rocks or hard clays by the mechanical means, exposed to weathering reduce the durability within "an engineering time scale". The paper deals with the factors that influence the weathering process. The analyzed weathering is a combination of processes acting simulta¬neously. Most of these processes depend on the change of the water con¬tent, thus the weathering process mainly develops when a material is subjected to the wetting-drying process, On the base of these results form of degradation process is modeled. The weathering process can be main¬ly described as physical weathering combined with chemical weathering on the free surfaces and on the cracks walls. Erosion as a result of weath¬ering, is the dominant geomorphic process on analyzed flysch terrain. According to the analysis, as the most appropriate due to the characteris¬tics the tests are chosen as index properties. Some of these tests are modified in order to adapt them to the determined characteristics of ma¬terials from flysch layers. The correlations between the measured values are used as the basis for the classification proposal of the analyzed mate¬rial, according to its resistance to weathering processes. Roughly, three main groups of samples are recognizable: the first one with carbonate content more then 90% is not weathered at the engineers time scale; the second group with carbonate content from 75% to 90% include samples susceptible to weathering in engineers time scale; the third group with carbonate content less then 75% include samples in which the weather¬ing occurs immediately after the exposition to the weathering factors.

Thickness control in electrophoretic deposition of WO3 nanofiber thin films for solar water splitting

International Nuclear Information System (INIS)

Fang, Yuanxing; Lee, Wei Cheat; Canciani, Giacomo E.; Draper, Thomas C.; Al-Bawi, Zainab F.; Bedi, Jasbir S.; Perry, Christopher C.; Chen, Qiao

2015-01-01

Graphical abstract: - Highlights: • A novel method combining electrospinning and electrophoretic deposition was established for the creation of nanostructured semiconductor thin films. • The created thin films displayed a high chemical stability with a controllable thickness. • The PEC water splitting performance of the thin films was optimized by fine-tuning the thickness of the films. • A maximum photoconversion efficiency was achieved by 18 μm nanofibrous thin films. - Abstract: Electrophoretic deposition (EPD) of ground electrospun WO 3 nanofibers was applied to create photoanodes with controlled morphology for the application of photoelectrochemical (PEC) water splitting. The correlations between deposition parameters and film thicknesses were investigated with theoretical models to precisely control the morphology of the nanostructured porous thin film. The photoconversion efficiency was further optimized as a function of film thickness. A maximum photoconversion efficiency of 0.924% from electrospun WO 3 nanofibers that EPD deposited on a substrate was achieved at a film thickness of 18 μm.

Photo-catalysis water splitting by platinum-loaded zeolite A

Science.gov (United States)

Cheng, Jing; Gao, Changda; Jing, Ming; Lu, Jian; Lin, Hui; Han, Zhaoxia; Ni, Zhengji; Zhang, Dawei

2018-05-01

Under the λ≥420 nm visible light illumination, the Pt4+ ions exchanged LTA zeolite powders without further heat-treatment presented H2 evolution at a rate of 5 μl/(15 mg·h) via photocatalysis water splitting. It was shown that the efficiency of H2 generation by the Pt4+ exchanged LTA zeolite powders without further heat-treatment was higher than the counterpart of the samples with heat treatment. In addition, the samples with lower Pt loading concentration showed higher H2 evolution rate than those of higher Pt loading did. The higher H2 evolution efficiency can be attributed to the effective isolation of water molecules and Pt at the atomic or the few atom ‘cluster’ scale by LTA zeolite’s periodical porous structure, which ensures a more efficient electron transfer efficiency for H2 evolution. However, after extra heat treatment, the Pt atoms reduced from Pt4+ in LTA zeolite’s cavities may tend to migrate to the surface and then form nano-particles, which led to the lower H2 evolution efficiency.

Thermochemical data for reactor materials and fission products: The ECN database

International Nuclear Information System (INIS)

Cordfunke, E.H.P.; Konings, R.J.M.

1993-02-01

The activities of the authors regarding the compilation of a database of thermochemical properties for reactor materials and fission products is reviewed. The evaluation procedures and techniques are outlined and examples are given. In addition, examples of the use of thermochemical data for the application in the field of Nuclear Technology are given. (orig.)

Direct selenylation of mixed Ni/Fe metal-organic frameworks to NiFe-Se/C nanorods for overall water splitting

Science.gov (United States)

Xu, Bo; Yang, He; Yuan, Lincheng; Sun, Yiqiang; Chen, Zhiming; Li, Cuncheng

2017-10-01

Development of low-cost, highly active bifunctional catalyst for efficient overall water splitting based on earth-abundant metals is still a great challenging task. In this work, we report a NiFe-Se/C composite nanorod as efficient non-precious-metal electrochemical catalyst derived from direct selenylation of a mixed Ni/Fe metal-organic framework. The as-obtained catalyst requires low overpotential to drive 10 mA cm-2 for HER (160 mV) and OER (240 mV) in 1.0 M KOH, respectively, and its catalytic activity is maintained for at least 20 h. Moreover, water electrolysis using this catalyst achieves high water splitting current density of 10 mA cm-2 at cell voltage of 1.68 V.

Technical and economic aspects of thermo-chemical decomposition of biomass in the processes of transformation of it in power-consuming energy/carriers by the use of the concentrated gel of sun radiation, has been considered

International Nuclear Information System (INIS)

Sultanova, K.D.; Mustafayeva, R.M.; Rzayev, P.F.

2007-01-01

Full text: The technical and economic assessment of process of thermo-chemical decomposition of biomass in the processes of transformation of it in power-consuming energy/carriers by the use of the concentrated gel of sun radiation, has been considered

NANOSTRUCTURED TiO2 SENSITIZED WITH PORPHYRINS FOR SOLAR WATER-SPLITTING

Directory of Open Access Journals (Sweden)

MARCELA-CORINA ROŞU

2011-03-01

Full Text Available Nanostructured TiO2 sensitized with porphyrins for Solar water-splitting.The production of hydrogen from water using solar light is very promising for generations of an ecologically pure carrier contributing to a clean, sustainable and renewable energy system. The selection of specific photocatalyst material for hydrogen production in photoelectrochemical cells (PECs is based on some important characteristics of semiconductor, such as photo-corrosion and chemical corrosion stability, photocatalytic potential, high sensitivity for UV-visible light. In the present paper, different nanocrystalline TiO2 photoanodes have been prepared via wet-chemical techniques followed by annealing treatment and sensitized with porphyrins and supramolecular complexes of porphyrins. The so obtained photocatalysts were characterized with UV-VIS absorption spectroscopy and spectrofluorimetry. The purpose of these experiments is to show if the prepared materials possess the necessary photocatalytic characteristics and if they can be used with success in H2 production from water decomposition in PECs.

Solution deposited and modified iron oxide for enhanced solar water splitting

Science.gov (United States)

Abel, Anthony J.

Growing worldwide energy demand coupled with an increasing awareness of anthropogenic climate change has driven research into carbon-neutral and solar-derived energy sources. One attractive strategy is the storage of solar energy in the bonds of H2 formed by photoelectrochemical (PEC) water splitting. Hematite, an iron oxide, has been widely investigated as a candidate material for PEC water splitting due to its stability, non-toxicity, earth abundance and consequent low cost, and a theoretical 15% solar-to-hydrogen conversion efficiency. However, poor electrical properties and slow rates of the water oxidation reaction have limited its potential as an economical water splitting catalyst. Additionally, the most efficient hematite-based devices are fabricated via expensive, vacuum-phase techniques, limiting scalability to broad integration into the energy supply. In this thesis, I develop a new, solution-based deposition method for high quality, planar hematite thin films using successive ionic layer adsorption and reaction (SILAR). The constant geometry and tight control over layer thickness possible with SILAR makes these films ideal model systems to understand the two key steps of PEC water oxidation: charge separation and interfacial hole transfer. In Chapter 3, I report on facile annealing treatments to dope hematite with Ti and Sn, and I show that these impurity atoms at the hematite/electrolyte interface increase hole transfer efficiency from nearly 0 to above 60%. However, charge separation remains below 15% with these dopants incorporated via solid state diffusion, mainly due to low hole mobility. To overcome this associated small transport length, extremely thin hematite coatings were deposited on Sb:SnO2 monolayer inverse opal scaffolds. With this modified substrate, photocurrent increased proportionately to the surface area of the scaffold. While Chapter 3 discusses incorporation of dopants via solid state diffusion, Chapter 4 examines methods to

Nanoscale Optimization and Statistical Modeling of Photoelectrochemical Water Splitting Efficiency of N-Doped TiO2 Nanotubes

KAUST Repository

Isimjan, Tayirjan T.; Trifkovic, Milana; Abdullahi, Inusa; Rohani, Sohrab M F; Ray, Ajay

2014-01-01

Highly ordered nitrogen-doped titanium dioxide (N-doped TiO2) nanotube array films with enhanced photo-electrochemical water splitting efficiency (PCE) for hydrogen generation were fabricated by electrochemical anodization, followed by annealing

A miniature solar device for overall water splitting consisting of series-connected spherical silicon solar cells

KAUST Repository

Kageshima, Yosuke

2016-04-18

A novel “photovoltaics (PV) + electrolyzer” concept is presented using a simple, small, and completely stand-alone non-biased device for solar-driven overall water splitting. Three or four spherical-shaped p-n junction silicon balls were successfully connected in series, named “SPHELAR.” SPHELAR possessed small projected areas of 0.20 (3PVs) and 0.26 cm2 (4PVs) and exhibited working voltages sufficient for water electrolysis. Impacts of the configuration on the PV module performance were carefully analyzed, revealing that a drastic increase in the photocurrent (≈20%) was attained by the effective utilization of a reflective sheet. Separate investigations on the electrocatalyst performance showed that non-noble metal based materials with reasonably small sizes (<0.80 cm2) exhibited substantial currents at the PV working voltage. By combining the observations of the PV characteristics, light management and electrocatalyst performance, solar-driven overall water splitting was readily achieved, reaching solar-to-hydrogen efficiencies of 7.4% (3PVs) and 6.4% (4PVs).

A miniature solar device for overall water splitting consisting of series-connected spherical silicon solar cells

KAUST Repository

Kageshima, Yosuke; Shinagawa, Tatsuya; Kuwata, Takaaki; Nakata, Josuke; Minegishi, Tsutomu; Takanabe, Kazuhiro; Domen, Kazunari

2016-01-01

A novel “photovoltaics (PV) + electrolyzer” concept is presented using a simple, small, and completely stand-alone non-biased device for solar-driven overall water splitting. Three or four spherical-shaped p-n junction silicon balls were successfully connected in series, named “SPHELAR.” SPHELAR possessed small projected areas of 0.20 (3PVs) and 0.26 cm2 (4PVs) and exhibited working voltages sufficient for water electrolysis. Impacts of the configuration on the PV module performance were carefully analyzed, revealing that a drastic increase in the photocurrent (≈20%) was attained by the effective utilization of a reflective sheet. Separate investigations on the electrocatalyst performance showed that non-noble metal based materials with reasonably small sizes (<0.80 cm2) exhibited substantial currents at the PV working voltage. By combining the observations of the PV characteristics, light management and electrocatalyst performance, solar-driven overall water splitting was readily achieved, reaching solar-to-hydrogen efficiencies of 7.4% (3PVs) and 6.4% (4PVs).

2009 Thermochemical Conversion Platform Review Report

Energy Technology Data Exchange (ETDEWEB)

Ferrell, John [Office of Energy Efficiency and Renewable Energy (EERE), Washington, DC (United States)

2009-12-01

This document summarizes the recommendations and evaluations provided by an independent external panel of experts at the U.S. Department of Energy Biomass Program’s Thermochemical Conversion platform review meeting, held on April 14-16, 2009, at the Sheraton Denver Downtown, Denver, Colorado.

Hydrogen generation using the modular helium reactor

International Nuclear Information System (INIS)

Richards, M.; Shenoy, A.

2004-01-01

Process heat from a high-temperature nuclear reactor can be used to drive a set of chemical reactions, with the net result of splitting water into hydrogen and oxygen. For example, process heat at temperatures in the range 850 deg.C to 950 deg.C can drive the sulfur-iodine (SI) thermochemical process to produce hydrogen with high efficiency. Electricity can also be used to split water, using conventional, low-temperature electrolysis. An example of a hybrid process is high-temperature electrolysis (HTE), in which process heat is used to generate steam, which is then supplied to an electrolyser to generate hydrogen. In this paper we investigate the coupling of the Modular Helium Reactor (MHR) to the SI process and HTE. These concepts are referred to as the H2-MHR. Optimization of the MHR core design to produce higher coolant outlet temperatures is also discussed. The use of fixed orifices to control the flow distribution is a promising design solution for increasing the coolant outlet temperature without increasing peak fuel temperatures significantly

Non-equilibrium thermochemical heat storage in porous media: Part 1 – Conceptual model

International Nuclear Information System (INIS)

Nagel, T.; Shao, H.; Singh, A.K.; Watanabe, N.; Roßkopf, C.; Linder, M.; Wörner, A.; Kolditz, O.

2013-01-01

Thermochemical energy storage can play an important role in the establishment of a reliable renewable energy supply and can increase the efficiency of industrial processes. The application of directly permeated reactive beds leads to strongly coupled mass and heat transport processes that also determine reaction kinetics. To advance this technology beyond the laboratory stage requires a thorough theoretical understanding of the multiphysics phenomena and their quantification on a scale relevant to engineering analyses. Here, the theoretical derivation of a macroscopic model for multicomponent compressible gas flow through a porous solid is presented along with its finite element implementation where solid–gas reactions occur and both phases have individual temperature fields. The model is embedded in the Theory of Porous Media and the derivation is based on the evaluation of the Clausius–Duhem inequality. Special emphasis is placed on the interphase coupling via mass, momentum and energy interaction terms and their effects are partially illustrated using numerical examples. Novel features of the implementation of the described model are verified via comparisons to analytical solutions. The specification, validation and application of the full model to a calcium hydroxide/calcium oxide based thermochemical storage system are the subject of part 2 of this study. - Highlights: • Rigorous application of the Theory of Porous Media and the 2nd law of thermodynamics. • Thermodynamically consistent model for thermochemical heat storage systems. • Multicomponent gas; modified Fick's and Darcy's law; thermal non-equilibrium; solid–gas reactions. • Clear distinction between source and production terms. • Open source finite element implementation and benchmarks

Water Splitting over Epitaxially Grown InGaN Nanowires on-Metallic Titanium/Silicon Template: Reduced Interfacial Transfer Resistance and Improved Stability

KAUST Repository

Ebaid, Mohamed

2018-03-09

Water splitting using InGaN-based photocatalysts may have a great contribution in future renewable energy production systems. Among the most important parameters to solve are those related to substrate lattice-matching compatibility. Here, we directly grow InGaN nanowires (NWs) on a metallic Ti/Si template, for improving water splitting performance compared to a bare Si substrate. The open circuit potential of the epitaxially grown InGaN NWs on metallic Ti was almost two times that of those grown on Si substrate. The interfacial transfer resistance was also reduced significantly after introducing the metallic Ti interlayer. An applied-bias-photon-to-current conversion efficiency of 2.2% and almost unity Faradic efficiency for hydrogen generation were achieved using this approach. The InGaN NWs grown on Ti showed improved stability of hydrogen generation under continuous operation conditions, when compared to those grown on Si, emphasizing the role of the semiconductor-on-metal approach in enhancing the overall efficiency of water splitting catalysts.

Stochastic split determinant algorithms

International Nuclear Information System (INIS)

Horvatha, Ivan

2000-01-01

I propose a large class of stochastic Markov processes associated with probability distributions analogous to that of lattice gauge theory with dynamical fermions. The construction incorporates the idea of approximate spectral split of the determinant through local loop action, and the idea of treating the infrared part of the split through explicit diagonalizations. I suggest that exact algorithms of practical relevance might be based on Markov processes so constructed

NiCo2S4 nanowires array as an efficient bifunctional electrocatalyst for full water splitting with superior activity

Science.gov (United States)

Liu, Danni; Lu, Qun; Luo, Yonglan; Sun, Xuping; Asiri, Abdullah M.

2015-09-01

The present communication reports the topotactic conversion of NiCo2O4 nanowires array on carbon cloth (NiCo2O4 NA/CC) into NiCo2S4 NA/CC, which is used as an efficient bifunctional electrocatalyst for water splitting with good durability and superior activity in 1.0 M KOH. This NiCo2S4 NA/CC electrode produces 100 mA cm-2 at an overpotential of 305 mV for hydrogen evolution and 100 mA cm-2 at an overpotential of 340 mV for oxygen evolution. To afford a 10 mA cm-2 water-splitting current, the alkaline water electrolyzer made from NiCo2S4 NA/CC needs a cell voltage of 1.68 V, which is 300 mV less than that for NiCo2O4 NA/CC, and has good stability.The present communication reports the topotactic conversion of NiCo2O4 nanowires array on carbon cloth (NiCo2O4 NA/CC) into NiCo2S4 NA/CC, which is used as an efficient bifunctional electrocatalyst for water splitting with good durability and superior activity in 1.0 M KOH. This NiCo2S4 NA/CC electrode produces 100 mA cm-2 at an overpotential of 305 mV for hydrogen evolution and 100 mA cm-2 at an overpotential of 340 mV for oxygen evolution. To afford a 10 mA cm-2 water-splitting current, the alkaline water electrolyzer made from NiCo2S4 NA/CC needs a cell voltage of 1.68 V, which is 300 mV less than that for NiCo2O4 NA/CC, and has good stability. Electronic supplementary information (ESI) available: Experimental section and ESI Figures. See DOI: 10.1039/c5nr04064g

Efficient photoelectrochemical water splitting by a doping-controlled GaN photoanode coated with NiO cocatalyst

International Nuclear Information System (INIS)

Kang, Jin-Ho; Kim, Soo Hee; Ebaid, Mohamed; Lee, June Key; Ryu, Sang-Wan

2014-01-01

Efficient photoelectrochemical (PEC) water splitting was demonstrated by a doping-controlled GaN photoanode coated with NiO cocatalyst. Highly doped n-GaN was sandwiched between undoped GaN layers to effectively collect electrons through ohmic contact. With zero external bias, the photocurrent density of the optimized doping profile was ∼3.5 times higher than that of the undoped GaN reference. However, the increased doping concentration degraded the photoanode stability, which was attributed to crystalline defects generated in the highly doped n-GaN. NiO cocatalyst improved the long-term stability of the photoanode because of GaN/NiO band alignment, enhancing hole transport into NiO and suppressing PEC corrosion mediated by hole crowding in GaN. This work established a design strategy for increasing the photocurrent as well as improving stability during water splitting with a GaN-based photoanode

Influence of material choice on cost estimation of some key components of the Sulfur Iodine thermochemical process

International Nuclear Information System (INIS)

Gilardi, T.; Rodriguez, G.; Gomez, A.; Leybros, J.; Borgard, J.M.; Carles, P.; Anzieu, P.

2006-01-01

In the frame of the preliminary design of an sulfur/iodine thermochemical plant coupled with a 600 MWth Helium cooled High Temperature Reactor, CEA has pre-designed all the components of the I/S plant and has started to the cost estimation of all the key components with some industrial cost evaluation methods proposed by CHAUVEL or PETER and TIMMERHAUS. The purpose of the paper is to present the strong influence of material choice on final cost estimation of these key components by comparing price with standard material (steel) and the most appropriate material selected to support the strong corrosion involved by several chemical reactions of the I/S process. These results reinforce the fact that material selection must be done with the best accuracy and that it will be a key factor in the global economy of these plant investment. (authors)

WO3 nanoflakes decorated with CuO clusters for enhanced photoelectrochemical water splitting

Directory of Open Access Journals (Sweden)

Chongwu Wang

2018-04-01

Full Text Available The low quantum efficiency arising from poor charges transfer and insufficient light absorption is one of the critical challenges toward achieving highly efficient water splitting in photoelectrochemical cells. Three dimensions (3D structures and heterojunctions have received intensive research interests recent years due to their excellent ability to separate photo-generated charges as well as the enhanced light harvesting property. Herein, 3D CuO/WO3 structure was fabricated through a facile solvothermal method followed by chemical bath deposition. The loading of CuO clusters on WO3 nanoflake arrays results in a much improved photocurrent density compared with that of pristine WO3 nanoflake arrays, which reaches 1.8 mA/cm2 at 1.23 V vs. the reversible hydrogen electrode. The electrochemical impedance spectroscopy measurement demonstrates that the improved performance of CuO/WO3 electrode is attributed to the accelerated charge transfer kinetics as a result of the desirable band alignment in CuO/WO3 heterojunction. This work demonstrates a facile strategy to construct superior WO3 electrode, which will ultimately allow for efficient storage of solar energy into hydrogen. Keywords: Photoelectrochemistry, Water splitting, Tungsten trioxide photoanode, CuO clusters, Heterojunction

Promoting Photocatalytic Overall Water Splitting by Controlled Magnesium Incorporation in SrTiO3 Photocatalysts

NARCIS (Netherlands)

Han, Kai; Lin, Yen Chun; Yang, Chia Min; Jong, Ronald; Mul, Guido; Mei, Bastian

2017-01-01

SrTiO3 is a well-known photocatalyst inducing overall water splitting when exposed to UV irradiation of wavelengths <370 nm. However, the apparent quantum efficiency of SrTiO3 is typically low, even when functionalized with nanoparticles of Pt or Ni@NiO. Here, we introduce a simple solid-state

Stability of Ag@SiO2 core–shell particles in conditions of photocatalytic overall water-splitting

NARCIS (Netherlands)

Park, Sun Young; Han, Kai; O'Neill, Devin B.; Mul, Guido

2017-01-01

Core–shell nanoparticles containing plasmonic metals (Ag or Au) have been frequently reported to enhance performance of photo-electrochemical (PEC) devices. However, the stability of these particles in water-splitting conditions is usually not addressed. In this study we demonstrate that Ag@SiO2

Electrolysis of water on (oxidized) metal surfaces

DEFF Research Database (Denmark)

Rossmeisl, Jan; Logadottir, Ashildur; Nørskov, Jens Kehlet

2005-01-01

Density functional theory calculations are used as the basis for an analysis of the electrochemical process, where by water is split to form molecular oxygen and hydrogen. We develop a method for obtaining the thermochemistry of the electrochemical water splitting process as a function of the bias...... directly from the electronic structure calculations. We consider electrodes of Pt(111) and Au(111) in detail and then discuss trends for a series of different metals. We show that the difficult step in the water splitting process is the formation of superoxy-type (OOH) species on the surface...... by the splitting of a water molecule on top an adsorbed oxygen atom. One conclusion is that this is only possible on metal surfaces that are (partly) oxidized. We show that the binding energies of the different intermediates are linearly correlated for a number of metals. In a simple analysis, where the linear...

Systematic validation of non-equilibrium thermochemical models using Bayesian inference

KAUST Repository

Miki, Kenji

2015-10-01

© 2015 Elsevier Inc. The validation process proposed by Babuška et al. [1] is applied to thermochemical models describing post-shock flow conditions. In this validation approach, experimental data is involved only in the calibration of the models, and the decision process is based on quantities of interest (QoIs) predicted on scenarios that are not necessarily amenable experimentally. Moreover, uncertainties present in the experimental data, as well as those resulting from an incomplete physical model description, are propagated to the QoIs. We investigate four commonly used thermochemical models: a one-temperature model (which assumes thermal equilibrium among all inner modes), and two-temperature models developed by Macheret et al. [2], Marrone and Treanor [3], and Park [4]. Up to 16 uncertain parameters are estimated using Bayesian updating based on the latest absolute volumetric radiance data collected at the Electric Arc Shock Tube (EAST) installed inside the NASA Ames Research Center. Following the solution of the inverse problems, the forward problems are solved in order to predict the radiative heat flux, QoI, and examine the validity of these models. Our results show that all four models are invalid, but for different reasons: the one-temperature model simply fails to reproduce the data while the two-temperature models exhibit unacceptably large uncertainties in the QoI predictions.

Beneficial effects of substituting trivalent ions in the B-site of La0.5Sr0.5Mn1-xAxO3 (A = Al, Ga, Sc) on the thermochemical generation of CO and H2 from CO2 and H2O.

Science.gov (United States)

Dey, Sunita; Naidu, B S; Rao, C N R

2016-02-14

The effect of substitution of Al(3+), Ga(3+) and Sc(3+) ions in the Mn(3+) site of La0.5Sr0.5MnO3 on the thermochemical splitting of CO2 to generate CO has been studied in detail. Both La0.5Sr0.5Mn1-xGaxO3 and La0.5Sr0.5Mn1-xScxO3 give high yields of O2 and generate CO more efficiently than La0.5Sr0.5Mn1-xAlxO3 or the parent La0.5Sr0.5MnO3. Substitution of even 5% Sc(3+) (x = 0.05) results in a remarkable improvement in performance. Thus La0.5Sr0.5Mn0.95Sc0.05O3 produces 417 μmol g(-1) of O2 and 545 μmol g(-1) of CO, respectively, i.e. 2 and 1.7 times more O2 and CO than La0.5Sr0.5MnO3. This manganite also generates H2 satisfactorily by the thermochemical splitting of H2O.

Performance analysis of a photovoltaic-thermochemical hybrid system prototype

International Nuclear Information System (INIS)

Li, Wenjia; Ling, Yunyi; Liu, Xiangxin; Hao, Yong

2017-01-01

Highlights: •A modular photovoltaic-thermochemical hybrid system prototype is proposed. •Net solar-electric efficiency up to 41% is achievable. •Stable solar power supply is achievable via convenient energy storage. •The modular design facilitates the scalability of the hybrid system. -- Abstract: A solar photovoltaic (PV) thermochemical hybrid system consisting of a point-focus Fresnel concentrator, a PV cell and a methanol thermochemical reactor is proposed. In particular, a reactor capable of operating under high solar concentration is designed, manufactured and tested. Studies on both kinetic and thermodynamic characteristics of the reactor and the system are performed. Analysis of numerical and experimental results shows that with cascaded solar energy utilization and synergy among different forms of energy, the hybrid system has the advantages of high net solar-electric efficiency (up to 41%), stable solar energy power supply, solar energy storage (via syngas) and flexibility in application scale. The hybrid system proposed in this work provides a potential solution to some key challenges of current solar energy utilization technologies.

Thickness control in electrophoretic deposition of WO{sub 3} nanofiber thin films for solar water splitting

Energy Technology Data Exchange (ETDEWEB)

Fang, Yuanxing; Lee, Wei Cheat; Canciani, Giacomo E.; Draper, Thomas C.; Al-Bawi, Zainab F. [Department of Chemistry, School of Life Sciences, University of Sussex, Brighton BN1 9QJ (United Kingdom); Bedi, Jasbir S. [School of Public Health & Zoonoses, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana 141004 Punjab (India); Perry, Christopher C. [Division of Biochemistry, School of Medicine, Loma Linda University, Loma Linda, CA 92350 (United States); Chen, Qiao, E-mail: qiao.chen@sussex.ac.uk [Department of Chemistry, School of Life Sciences, University of Sussex, Brighton BN1 9QJ (United Kingdom)

2015-12-15

Graphical abstract: - Highlights: • A novel method combining electrospinning and electrophoretic deposition was established for the creation of nanostructured semiconductor thin films. • The created thin films displayed a high chemical stability with a controllable thickness. • The PEC water splitting performance of the thin films was optimized by fine-tuning the thickness of the films. • A maximum photoconversion efficiency was achieved by 18 μm nanofibrous thin films. - Abstract: Electrophoretic deposition (EPD) of ground electrospun WO{sub 3} nanofibers was applied to create photoanodes with controlled morphology for the application of photoelectrochemical (PEC) water splitting. The correlations between deposition parameters and film thicknesses were investigated with theoretical models to precisely control the morphology of the nanostructured porous thin film. The photoconversion efficiency was further optimized as a function of film thickness. A maximum photoconversion efficiency of 0.924% from electrospun WO{sub 3} nanofibers that EPD deposited on a substrate was achieved at a film thickness of 18 μm.

Efficient carbon dots/NiFe-layered double hydroxide/BiVO4 photoanodes for photoelectrochemical water splitting

Science.gov (United States)

Lv, Xiaowei; Xiao, Xin; Cao, Minglei; Bu, Yi; Wang, Chuanqing; Wang, Mingkui; Shen, Yan

2018-05-01

Modification of semiconductor photoanodes with oxygen evolution catalyst (OEC) is an effective approach for improving photoelectrochemical (PEC) water splitting efficiency. In the configuration, how to increase the activity of OEC is crucial to further improve PEC performance. Herein, a ternary photoanode system was designed to enhance PEC efficiency of photoelectrodes through introducing carbon dots (CDs), NiFe-layered double hydroxide (NiFe-LDH) nanosheets on BiVO4 particles. Systematic research shows that NiFe-LDH serves as an OEC which accelerates oxygen evolution kinetics, while the introduction of CDs can further reduce charge transfer resistance and overpotential for oxygen evolution. Under the synergistic effect of NiFe-LDH and CDs, the photocurrent and incident photon to current conversion efficiency (IPCE) of the resulting CDs/NiFe-LDH/BiVO4 photoanode is improved significantly than those of the NiFe-LDH/BiVO4 electrode. Consequently, such a ternary heterostructure could be an alternative way to further enhance PEC water splitting performance.

Integrating a Semitransparent, Fullerene-Free Organic Solar Cell in Tandem with a BiVO4 Photoanode for Unassisted Solar Water Splitting.

Science.gov (United States)

Peng, Yuelin; Govindaraju, Gokul V; Lee, Dong Ki; Choi, Kyoung-Shin; Andrew, Trisha L

2017-07-12

We report an unassisted solar water splitting system powered by a diketopyrrolopyrrole (DPP)-containing semitransparent organic solar cell. Two major merits of this fullerene-free solar cell enable its integration with a BiVO 4 photoanode. First is the high open circuit voltage and high fill factor displayed by this single junction solar cell, which yields sufficient power to effect water splitting when serially connected to an appropriate electrode/catalyst. Second, the wavelength-resolved photoaction spectrum of the DPP-based solar cell has minimal overlap with that of the BiVO 4 photoanode, thus ensuring that light collection across these two components can be optimized. The latter feature enables a new water splitting device configuration wherein the solar cell is placed first in the path of incident light, before the BiVO 4 photoanode, although BiVO 4 has a wider bandgap. This configuration is accessed by replacing the reflective top electrode of the standard DPP-based solar cell with a thin metal film and an antireflection layer, thus rendering the solar cell semitransparent. In this configuration, incident light does not travel through the aqueous electrolyte to reach the solar cell or photoanode, and therefore, photon losses due to the scattering of water are reduced. Moreover, this new configuration allows the BiVO 4 photoanode to be back-illuminated, i.e., through the BiVO 4 /back contact interface, which leads to higher photocurrents compared to front illumination. The combination of a semitransparent single-junction solar cell and a BiVO 4 photoanode coated with oxygen evolution catalysts in a new device configuration yielded an unassisted solar water splitting system with a solar-to-hydrogen conversion efficiency of 2.2% in water.

Thermochemical nonequilibrium analysis of O2+Ar based on state-resolved kinetics

International Nuclear Information System (INIS)

Kim, Jae Gang; Boyd, Iain D.

2015-01-01

Highlights: • Thermochemical nonequilibrium studies for three lowest lying electronic states of O 2 . • The complete sets of the rovibrational state-to-state transition rates of O 2 +Ar. • Rovibrational relaxations and coupled chemical reactions of O 2 . • Nonequilibrium reaction rates of O 2 derived from the quasi-steady state assumption. - Abstract: The thermochemical nonequilibrium of the three lowest lying electronic states of molecular oxygen, O 2 (X 3 Σ g - ,a 1 Δ g ,b 1 Σ g + ), through interactions with argon is studied in the present work. The multi-body potential energy surfaces of O 2 +Ar are evaluated from the semi-classical RKR potential of O 2 in each electronic state. The rovibrational states and energies of each electronic state are calculated by the quantum mechanical method based on the present inter-nuclear potential of O 2 . Then, the complete sets of the rovibrational state-to-state transition rate coefficients of O 2 +Ar are calculated by the quasi-classical trajectory method including the quasi-bound states. The system of master equations constructed by the present state-to-state transition rate coefficients are solved to analyze the thermochemical nonequilibrium of O 2 +Ar in various heat bath conditions. From these studies, it is concluded that the vibrational relaxation and coupled chemical reactions of each electronic state needs to be treated as a separate nonequilibrium process, and rotational nonequilibrium needs to be considered at translational temperatures above 10,000 K

Revisiting the BaO2/BaO redox cycle for solar thermochemical energy storage.

Science.gov (United States)

Carrillo, A J; Sastre, D; Serrano, D P; Pizarro, P; Coronado, J M

2016-03-21

The barium peroxide-based redox cycle was proposed in the late 1970s as a thermochemical energy storage system. Since then, very little attention has been paid to such redox couples. In this paper, we have revisited the use of reduction-oxidation reactions of the BaO2/BaO system for thermochemical heat storage at high temperatures. Using thermogravimetric analysis, reduction and oxidation reactions were studied in order to find the main limitations associated with each process. Furthermore, the system was evaluated through several charge-discharge stages in order to analyse its possible degradation after repeated cycling. Through differential scanning calorimetry the heat stored and released were also determined. Oxidation reaction, which was found to be slower than reduction, was studied in more detail using isothermal tests. It was observed that the rate-controlling step of BaO oxidation follows zero-order kinetics, although at high temperatures a deviation from Arrhenius behaviour was observed probably due to hindrances to anionic oxygen diffusion caused by the formation of an external layer of BaO2. This redox couple was able to withstand several redox cycles without deactivation, showing reaction conversions close to 100% provided that impurities are previously eliminated through thermal pre-treatment, demonstrating the feasibility of this system for solar thermochemical heat storage.

Split Scheduling with Uniform Setup Times

NARCIS (Netherlands)

Schalekamp, F.; Sitters, R.A.; van der Ster, S.L.; Stougie, L.; Verdugo, V.; van Zuylen, A.

2015-01-01

We study a scheduling problem in which jobs may be split into parts, where the parts of a split job may be processed simultaneously on more than one machine. Each part of a job requires a setup time, however, on the machine where the job part is processed. During setup, a machine cannot process or

Performance evaluation of four different methods for circulating water in commercial-scale, split-pond aquaculture systems

Science.gov (United States)

The split-pond consists of a fish-culture basin that is connected to a waste-treatment lagoon by two conveyance structures. Water is circulated between the two basins with high-volume pumps and many different pumping systems are being used on commercial farms. Pump performance was evaluated with fou...

Tungsten carbide nanoparticles as efficient cocatalysts for photocatalytic overall water splitting

KAUST Repository

Garcia Esparza, Angel T.

2012-12-17

Tungsten carbide exhibits platinum-like behavior, which makes it an interesting potential substitute for noble metals in catalytic applications. Tungsten carbide nanocrystals (≈5 nm) are directly synthesized through the reaction of tungsten precursors with mesoporous graphitic C3N 4 (mpg-C3N4) as the reactive template in a flow of inert gas at high temperatures. Systematic experiments that vary the precursor compositions and temperatures used in the synthesis selectively generate different compositions and structures for the final nanocarbide (W 2C or WC) products. Electrochemical measurements demonstrate that the WC phase with a high surface area exhibits both high activity and stability in hydrogen evolution over a wide pH range. The WC sample also shows excellent hydrogen oxidation activity, whereas its activity in oxygen reduction is poor. These tungsten carbides are successful cocatalysts for overall water splitting and give H2 and O2 in a stoichiometric ratio from H 2O decomposition when supported on a Na-doped SrTiO3 photocatalyst. Herein, we present tungsten carbide (on a small scale) as a promising and durable catalyst substitute for platinum and other scarce noble-metal catalysts in catalytic reaction systems used for renewable energy generation. Platinum replacement: The phase-controlled synthesis of tungsten carbide nanoparticles from the nanoconfinement of a mesoporous graphite C 3N4 (mpg-C3N4) reactive template is shown. The nanomaterials catalyze hydrogen evolution/oxidation reactions, but are inactive in the oxygen reduction reaction. Tungsten carbide is an effective cocatalyst for photocatalytic overall water splitting (see picture). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tungsten carbide nanoparticles as efficient cocatalysts for photocatalytic overall water splitting

KAUST Repository

Garcia Esparza, Angel T.; Cha, Dong Kyu; Ou, Yiwei; Kubota, Jun; Domen, Kazunari; Takanabe, Kazuhiro

2012-01-01

Tungsten carbide exhibits platinum-like behavior, which makes it an interesting potential substitute for noble metals in catalytic applications. Tungsten carbide nanocrystals (≈5 nm) are directly synthesized through the reaction of tungsten precursors with mesoporous graphitic C3N 4 (mpg-C3N4) as the reactive template in a flow of inert gas at high temperatures. Systematic experiments that vary the precursor compositions and temperatures used in the synthesis selectively generate different compositions and structures for the final nanocarbide (W 2C or WC) products. Electrochemical measurements demonstrate that the WC phase with a high surface area exhibits both high activity and stability in hydrogen evolution over a wide pH range. The WC sample also shows excellent hydrogen oxidation activity, whereas its activity in oxygen reduction is poor. These tungsten carbides are successful cocatalysts for overall water splitting and give H2 and O2 in a stoichiometric ratio from H 2O decomposition when supported on a Na-doped SrTiO3 photocatalyst. Herein, we present tungsten carbide (on a small scale) as a promising and durable catalyst substitute for platinum and other scarce noble-metal catalysts in catalytic reaction systems used for renewable energy generation. Platinum replacement: The phase-controlled synthesis of tungsten carbide nanoparticles from the nanoconfinement of a mesoporous graphite C 3N4 (mpg-C3N4) reactive template is shown. The nanomaterials catalyze hydrogen evolution/oxidation reactions, but are inactive in the oxygen reduction reaction. Tungsten carbide is an effective cocatalyst for photocatalytic overall water splitting (see picture). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Splitting methods for split feasibility problems with application to Dantzig selectors

International Nuclear Information System (INIS)

He, Hongjin; Xu, Hong-Kun

2017-01-01

The split feasibility problem (SFP), which refers to the task of finding a point that belongs to a given nonempty, closed and convex set, and whose image under a bounded linear operator belongs to another given nonempty, closed and convex set, has promising applicability in modeling a wide range of inverse problems. Motivated by the increasingly data-driven regularization in the areas of signal/image processing and statistical learning, in this paper, we study the regularized split feasibility problem (RSFP), which provides a unified model for treating many real-world problems. By exploiting the split nature of the RSFP, we shall gainfully employ several efficient splitting methods to solve the model under consideration. A remarkable advantage of our methods lies in their easier subproblems in the sense that the resulting subproblems have closed-form representations or can be efficiently solved up to a high precision. As an interesting application, we apply the proposed algorithms for finding Dantzig selectors, in addition to demonstrating the effectiveness of the splitting methods through some computational results on synthetic and real medical data sets. (paper)

ADI splitting schemes for a fourth-order nonlinear partial differential equation from image processing

KAUST Repository

Calatroni, Luca

2013-08-01

We present directional operator splitting schemes for the numerical solution of a fourth-order, nonlinear partial differential evolution equation which arises in image processing. This equation constitutes the H -1-gradient flow of the total variation and represents a prototype of higher-order equations of similar type which are popular in imaging for denoising, deblurring and inpainting problems. The efficient numerical solution of this equation is very challenging due to the stiffness of most numerical schemes. We show that the combination of directional splitting schemes with implicit time-stepping provides a stable and computationally cheap numerical realisation of the equation.

ADI splitting schemes for a fourth-order nonlinear partial differential equation from image processing

KAUST Repository

Calatroni, Luca; Dü ring, Bertram; Schö nlieb, Carola-Bibiane

2013-01-01

We present directional operator splitting schemes for the numerical solution of a fourth-order, nonlinear partial differential evolution equation which arises in image processing. This equation constitutes the H -1-gradient flow of the total variation and represents a prototype of higher-order equations of similar type which are popular in imaging for denoising, deblurring and inpainting problems. The efficient numerical solution of this equation is very challenging due to the stiffness of most numerical schemes. We show that the combination of directional splitting schemes with implicit time-stepping provides a stable and computationally cheap numerical realisation of the equation.

WATER- AND COAL GASIFICATION

Directory of Open Access Journals (Sweden)

N. S. Nazarov

2006-01-01

Full Text Available According to the results of gas analysis it has been established that water- and coal gasification is rather satisfactorily described by three thermo-chemical equations. One of these equations is basic and independent and the other two equations depend on the first one.The proposed process scheme makes it possible to explain the known data and also permits to carry out the gasification process and obtain high-quality hydrogen carbon-monoxide which is applicable for practical use.

Estimation of thermochemical behavior of spallation products in mercury target

Energy Technology Data Exchange (ETDEWEB)

Kobayashi, Kaoru; Kaminaga, Masanori; Haga, Katsuhiro; Kinoshita, Hidetaka; Aso, Tomokazu; Teshigawara, Makoto; Hino, Ryutaro [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

2002-02-01

In order to examine the radiation safety of a spallation mercury target system, especially source term evaluation, it is necessary to clarify the chemical forms of spallation products generated by spallation reaction with proton beam. As for the chemical forms of spallation products in mercury that involves large amounts of spallation products, these forms were estimated by using the binary phase diagrams and the thermochemical equilibrium calculation based on the amounts of spallation product. Calculation results showed that the mercury would dissolve Al, As, B, Be, Bi, C, Co, Cr, Fe, Ga, Ge, Ir, Mo, Nb, Os, Re, Ru, Sb, Si, Ta, Tc, V and W in the element state, and Ag, Au, Ba, Br, Ca, Cd, Ce, Cl, Cs, Cu, Dy, Er, Eu, F, Gd, Hf, Ho, I, In, K, La, Li, Lu, Mg, Mn, Na, Nd, Ni, O, Pb, Pd, Pr, Pt, Rb, Rh, S, Sc, Se, Sm, Sn, Sr, Tb, Te, Ti, Tl, Tm, Y, Yb, Zn and Zr in the form of inorganic mercury compounds. As for As, Be, Co, Cr, Fe, Ge, Ir, Mo, Nb, Os, Pt, Re, Ru, Se, Ta, V, W and Zr, precipitation could be occurred when increasing the amounts of spallation products with operation time of the spallation target system. On the other hand, beryllium-7 (Be-7), which is produced by spallation reaction of oxygen in the cooling water of a safety hull, becomes the main factor of the external exposure to maintain the cooling loop. Based on the thermochemical equilibrium calculation to Be-H{sub 2}O binary system, the chemical forms of Be in the cooling water were estimated. Then the Be could exist in the form of cations such as BeOH{sup +}, BeO{sup +} and Be{sup 2+} under the condition of less than 10{sup -8} of the Be mole fraction in the cooling water. (author)

OECD/NEA thermochemical database

Energy Technology Data Exchange (ETDEWEB)

Byeon, Kee Hoh; Song, Dae Yong; Shin, Hyun Kyoo; Park, Seong Won; Ro, Seung Gy

1998-03-01

This state of the art report is to introduce the contents of the Chemical Data-Service, OECD/NEA, and the results of survey by OECD/NEA for the thermodynamic and kinetic database currently in use. It is also to summarize the results of Thermochemical Database Projects of OECD/NEA. This report will be a guide book for the researchers easily to get the validate thermodynamic and kinetic data of all substances from the available OECD/NEA database. (author). 75 refs.

Electrodialysis-based separation process for salt recovery and recycling from waste water

Science.gov (United States)

Tsai, Shih-Perng

1997-01-01

A method for recovering salt from a process stream containing organic contaminants is provided, comprising directing the waste stream to a desalting electrodialysis unit so as to create a concentrated and purified salt permeate and an organic contaminants containing stream, and contacting said concentrated salt permeate to a water-splitting electrodialysis unit so as to convert the salt to its corresponding base and acid.

Static analysis of the thermochemical hydrogen production IS process for assessment of the operation parameters and the chemical properties

International Nuclear Information System (INIS)

Kasahara, Seiji; Onuki, Kaoru; Nomura, Mikihiro; Nakao, Shin-ichi

2006-01-01

A sensitivity analysis of the operation parameters and the chemical properties in the thermochemical hydrogen production IS process (iodine-sulfur process) was carried out for a static flow sheet. These parameters were evaluated by hydrogen production thermal efficiency, the mass flow rate or heat exchange based on the heat/mass balance. The most important parameters were the concentration of HI after electro-electrodialysis (EED) and the apparent transport number of protons of the cation exchange membrane in the EED cell. HI concentration operation should be operated carefully because the parameters for optimum thermal efficiency and for the optimum flow rate and heat exchange were different. For the chemical properties, composition at the inlet of the HI decomposition procedure and HI x pseudo-azeotropic composition had great effects. The HI concentration after the EED should be optimized for each composition. The order of priority for the assessment of the operation parameters and chemical properties was determined by the evaluation. (author)

CuO-Functionalized Silicon Photoanodes for Photoelectrochemical Water Splitting Devices.

Science.gov (United States)

Shi, Yuanyuan; Gimbert-Suriñach, Carolina; Han, Tingting; Berardi, Serena; Lanza, Mario; Llobet, Antoni

2016-01-13

One main difficulty for the technological development of photoelectrochemical (PEC) water splitting (WS) devices is the fabrication of active, stable and cost-effective photoelectrodes that ensure high performance. Here, we report the development of a CuO/Silicon based photoanode, which shows an onset potential for the water oxidation of 0.53 V vs SCE at pH 9, that is, an overpotential of 75 mV, and high stability above 10 h. These values account for a photovoltage of 420 mV due to the absorbed photons by silicon, as proven by comparing with analogous CuO/FTO electrodes that are not photoactive. The photoanodes have been fabricated by sputtering a thin film of Cu(0) on commercially available n-type Si wafers, followed by a photoelectrochemical treatment in basic pH conditions. The resulting CuO/Cu layer acts as (1) protective layer to avoid the corrosion of nSi, (2) p-type hole conducting layer for efficient charge separation and transportation, and (3) electrocatalyst to reduce the overpotential of the water oxidation reaction. The low cost, low toxicity, and good performance of CuO-based coatings can be an attractive solution to functionalize unstable materials for solar energy conversion.

Thermochemical stability of Soviet macroporous sulfonated cation-exchangers

Energy Technology Data Exchange (ETDEWEB)

Rukhlyada, N.N.; Plotnikova, V.P.; Roginskaya, B.S.; Znamenskii, Yu.P.; Zavodovskaya, A.S.; Dobrova, E.I.

1988-10-20

The purpose of this work was to study the influence of macroporosity on the thermochemical stability of sulfonated cation-exchangers. The investigations were carried out on commercial macroporous sulfonated cation-exchangers based on styrene-divinylbenzene copolymers. Study of the thermochemical stability of macroporous sulfonated cation-exchangers in dilute hydrogen peroxide solutions showed that the type of macroporosity has virtually no influence on their stability. The determining factor in thermal stability of macroporous cation-exchangers, as of the gel type, is the degree of cross-linking of the polymer matrix. The capacity loss of macroporous cation-exchangers during oxidative thermolysis is caused by destruction of the macromolecular skeleton and elution of fragments of polar chains containing sulfo groups into the solution.

Research and development on chemical reactors made of industrial structural materials and hydriodic acid concentration technique for thermochemical hydrogen production IS process

International Nuclear Information System (INIS)

Kubo, Shinji; Iwatsuki, Jin; Takegami, Hiroaki; Kasahara, Seiji; Tanaka, Nobuyuki; Noguchi, Hiroki; Kamiji, Yu; Onuki, Kaoru

2015-10-01

Japan Atomic Energy Agency has been conducting a study on IS process for thermochemical hydrogen production in order to develop massive hydrogen production technology for hydrogen society. Integrity of the chemical reactors and concentration technology of hydrogen iodide in HIx solution were studied. In the former study, the chemical reactors were trial-fabricated using industrial materials. A test of 30 times of thermal cycle test under circulating condition of the Bunsen reaction solution showed integrity of the Bunsen reactor made of fluororesin lined steel. Also, 100 hours of reaction tests showed integrity of the sulfuric acid decomposer made of silicon carbide and of the hydrogen iodide decomposer made of Hastelloy C-276. In the latter study, concerning electro-electrodialysis using cation-exchange membrane, sulfuric acid in the anolyte had little influence on the concentration performance. These results suggest the purification system of HIx solution can be simplified. Based on the Nernst-Planck equation and the Smoluchowski equation, proton transport number, water permeance, and IR drop of the cation exchange membrane were formulated. The derived equations enable quantitative estimation for the performance indexes of Nafion ® membrane and, also, of ETFE-St membranes made by radiation-induced graft polymerization method. (author)

Effects of thermo-chemical pre-treatment on anaerobic biodegradability and hydrolysis of lignocellulosic biomass

NARCIS (Netherlands)

Fernandes, T.; Klaasse Bos, G.J.; Zeeman, G.; Sanders, J.P.M.; Lier, van J.B.

2009-01-01

The effects of different thermo-chemical pre-treatment methods were determined on the biodegradability and hydrolysis rate of lignocellulosic biomass. Three plant species, hay, straw and bracken were thermo-chemically pre-treated with calcium hydroxide, ammonium carbonate and maleic acid. After

2011 Biomass Program Platform Peer Review. Thermochemical Conversion

Energy Technology Data Exchange (ETDEWEB)

Grabowski, Paul E. [Office of Energy Efficiency and Renewable Energy (EERE), Washington, DC (United States)

2012-02-01

This document summarizes the recommendations and evaluations provided by an independent external panel of experts at the 2011 U.S. Department of Energy Biomass Program’s Thermochemical Conversion Platform Review meeting.

Thermochemical Biomass Gasification: A Review of the Current Status of the Technology

Directory of Open Access Journals (Sweden)

Ajay Kumar

2009-07-01

Full Text Available A review was conducted on the use of thermochemical biomass gasification for producing biofuels, biopower and chemicals. The upstream processes for gasification are similar to other biomass processing methods. However, challenges remain in the gasification and downstream processing for viable commercial applications. The challenges with gasification are to understand the effects of operating conditions on gasification reactions for reliably predicting and optimizing the product compositions, and for obtaining maximal efficiencies. Product gases can be converted to biofuels and chemicals such as Fischer-Tropsch fuels, green gasoline, hydrogen, dimethyl ether, ethanol, methanol, and higher alcohols. Processes and challenges for these conversions are also summarized.

Sustainable energy with thermochemical storage; Duurzame energie met thermochemische opslag

Energy Technology Data Exchange (ETDEWEB)

Bakker, M. [ECN Efficiency and Infrastructure, Petten (Netherlands)

2010-03-15

The Energy research Centre of the Netherlands ECN) foresees an important role for heat in sustainable construction of buildings. Using salt hydrates the surplus of heat can be stored in the summer which then can be used in the winter. By means of thermochemical storage natural gas for heating tap water or houses is no longer necessary. [Dutch] Energieonderzoek Centrum Nederland (ECN) ziet voor warmteopslag een belangrijke rol weggelegd in het duurzaam bouwen. Met behulp van zouthydraten kan de overtollige warmte in de zomer opgeslagen worden om deze in de winter weer vrij te maken. Met deze thermochemische opslag is in de nabije toekomst aardgas overbodig voor de verwarming van kraanwater of woonhuis.

Splitting Functions at High Transverse Momentum

CERN Document Server

Moutafis, Rhea Penelope; CERN. Geneva. TH Department

2017-01-01

Among the production channels of the Higgs boson one contribution could become significant at high transverse momentum which is the radiation of a Higgs boson from another particle. This note focuses on the calculation of splitting functions and cross sections of such processes. The calculation is first carried out on the example $e\\rightarrow e\\gamma$ to illustrate the way splitting functions are calculated. Then the splitting function of $e\\rightarrow eh$ is calculated in similar fashion. This procedure can easily be generalized to processes such as $q\\rightarrow qh$ or $g\\rightarrow gh$.

Life cycle assessment of hydrogen production from S-I thermochemical process coupled to a high temperature gas reactor

Energy Technology Data Exchange (ETDEWEB)

Giraldi, M. R.; Francois, J. L.; Castro-Uriegas, D. [Departamento de Sistemas Energeticos, Facultad de Ingenieria, Universidad Nacional Autonoma de Mexico, Paseo Cuauhnahuac No. 8532, Col. Progreso, C.P. 62550, Jiutepec, Morelos (Mexico)

2012-07-01

The purpose of this paper is to quantify the greenhouse gas (GHG) emissions associated to the hydrogen produced by the sulfur-iodine thermochemical process, coupled to a high temperature nuclear reactor, and to compare the results with other life cycle analysis (LCA) studies on hydrogen production technologies, both conventional and emerging. The LCA tool was used to quantify the impacts associated with climate change. The product system was defined by the following steps: (i) extraction and manufacturing of raw materials (upstream flows), (U) external energy supplied to the system, (iii) nuclear power plant, and (iv) hydrogen production plant. Particular attention was focused to those processes where there was limited information from literature about inventory data, as the TRISO fuel manufacture, and the production of iodine. The results show that the electric power, supplied to the hydrogen plant, is a sensitive parameter for GHG emissions. When the nuclear power plant supplied the electrical power, low GHG emissions were obtained. These results improve those reported by conventional hydrogen production methods, such as steam reforming. (authors)

Consequences of poly(vinyl chloride) presence on the thermochemical process of lignocellulosic biomass in CO₂ by thermogravimetric analysis.

Science.gov (United States)

He, Yao; Ma, Xiaoqian; Zeng, Guangbo

2015-02-01

The thermochemical processes of lignocellulosic biomass and its mixtures with poly(vinyl chloride) (PVC) fractions were investigated by thermogravimetric analysis in CO2 atmosphere. Superposition property was assumed to examine whether and/or to what extent interactions occurred during the mixture decomposition. Results showed that interactions existed, of which the intensities changed with reaction stage, heating rate and PVC quantity, and they actively behaved toward the decomposition in most cases. With PVC presence, lignocellulosic biomass turned from three-stage to four-stage decomposition process where the reactions occurred at lower temperatures with heightened intensity, especially in the first stage. The measured activation energies calculated by Ozawa-Flynn-Wall and Vyazovkin methods were of minor difference <5 kJ/mol, and comparing them between materials in each stage confirmed the results of interaction impact. This work provides a theoretical basis bringing about the possibilities of recycling CO2 into a reaction medium of thermo-treatment of lignocellulosic material with PVC contaminants. Copyright © 2014 Elsevier Ltd. All rights reserved.

Split scheduling with uniform setup times.

NARCIS (Netherlands)

F. Schalekamp; R.A. Sitters (René); S.L. van der Ster; L. Stougie (Leen); V. Verdugo; A. van Zuylen

2015-01-01

htmlabstractWe study a scheduling problem in which jobs may be split into parts, where the parts of a split job may be processed simultaneously on more than one machine. Each part of a job requires a setup time, however, on the machine where the job part is processed. During setup, a

3D WO3 /BiVO4 /Cobalt Phosphate Composites Inverse Opal Photoanode for Efficient Photoelectrochemical Water Splitting.

Science.gov (United States)

Zhang, Haifeng; Zhou, Weiwei; Yang, Yaping; Cheng, Chuanwei

2017-04-01

A novel 3D WO 3 /BiVO 4 /cobalt phosphate composite inverse opal is designed for photoeletrochemical (PEC) water splitting, yielding a significantly improved PEC performance. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Analysis and modeling of wafer-level process variability in 28 nm FD-SOI using split C-V measurements

Science.gov (United States)

Pradeep, Krishna; Poiroux, Thierry; Scheer, Patrick; Juge, André; Gouget, Gilles; Ghibaudo, Gérard

2018-07-01

This work details the analysis of wafer level global process variability in 28 nm FD-SOI using split C-V measurements. The proposed approach initially evaluates the native on wafer process variability using efficient extraction methods on split C-V measurements. The on-wafer threshold voltage (VT) variability is first studied and modeled using a simple analytical model. Then, a statistical model based on the Leti-UTSOI compact model is proposed to describe the total C-V variability in different bias conditions. This statistical model is finally used to study the contribution of each process parameter to the total C-V variability.

Mechanisms of mineral membrane fouling growth modulated by pulsed modes of current during electrodialysis: evidences of water splitting implications in the appearance of the amorphous phases of magnesium hydroxide and calcium carbonate.

Science.gov (United States)

Cifuentes-Araya, Nicolás; Astudillo-Castro, Carolina; Bazinet, Laurent

2014-07-15

Experiments revealed the fouling nature evolutions along different electrodialysis (ED) trials, and how it disappears when current pulsation acts repetitively on the interfaces of ion-exchange membranes (IEMs). Fouling was totally controlled on the diluate side of cation-exchange membrane (CEM) by the repetitive pulsation frequency of the higher on-duty ratios applied. They created steady water splitting proton-barriers that neutralized OH(-) leakage through the membrane, decreasing the interfacial pH, and fouling of the concentrate side. The anion-exchange membrane (AEM) on the diluate side was similarly protected, but it was fouled once water splitting OH(-) generation became either intense enough or excessively weak. Interestingly, amorphous magnesium hydroxide (AMH) stemmed on the CEM-diluate side from brucite under intense water splitting OH(-) generation, and/or strong OH(-) leakage electromigration through the membrane. Water dissociation and overlimiting current regimes triggered drastic water molecule removal from crystal lattices through an accelerated cascade water splitting reaction. Also, amorphous calcium carbonate (ACC) appeared on CEM under intense water splitting reaction, and disappeared once intense OH(-) leakage was allowed by the water splitting proton-barrier dissipation. Our findings have implications for membrane fouling control, as well as for the understanding of the growth behavior of CaCO3 and Mg(OH)2 species on electromembrane interfaces. Copyright © 2014 Elsevier Inc. All rights reserved.

Prospect of HTGRs for hydrogen production in Indonesia

International Nuclear Information System (INIS)

Rusli, A.; Dasuki, A.S.; Rahman, M.; Nuriman; Sudarto

1997-01-01

Hydrogen energy system is interesting to many people of the world that because of hydrogen promised to save our planet earth from destroying of burning of fossil fuels. The selected development of hydrogen production from water such as electrolysis and thermochemical cycles are evaluated. These processes are allowed to split the water at lower temperature, still in the range of HTGRs' working temperature. An overview of related studies in recent years enables the development of research to be followed, studied and evaluated are mentioned. The prospect of hydrogen market in Indonesia and economic consideration based on previous studied are also analyzed and evaluated. (author). 11 refs, 5 figs, 13 tabs

Third millenium ideal gas and condensed phase thermochemical database for combustion (with update from active thermochemical tables).

Energy Technology Data Exchange (ETDEWEB)

Burcat, A.; Ruscic, B.; Chemistry; Technion - Israel Inst. of Tech.

2005-07-29

The thermochemical database of species involved in combustion processes is and has been available for free use for over 25 years. It was first published in print in 1984, approximately 8 years after it was first assembled, and contained 215 species at the time. This is the 7th printed edition and most likely will be the last one in print in the present format, which involves substantial manual labor. The database currently contains more than 1300 species, specifically organic molecules and radicals, but also inorganic species connected to combustion and air pollution. Since 1991 this database is freely available on the internet, at the Technion-IIT ftp server, and it is continuously expanded and corrected. The database is mirrored daily at an official mirror site, and at random at about a dozen unofficial mirror and 'finger' sites. The present edition contains numerous corrections and many recalculations of data of provisory type by the G3//B3LYP method, a high-accuracy composite ab initio calculation. About 300 species are newly calculated and are not yet published elsewhere. In anticipation of the full coupling, which is under development, the database started incorporating the available (as yet unpublished) values from Active Thermochemical Tables. The electronic version now also contains an XML file of the main database to allow transfer to other formats and ease finding specific information of interest. The database is used by scientists, educators, engineers and students at all levels, dealing primarily with combustion and air pollution, jet engines, rocket propulsion, fireworks, but also by researchers involved in upper atmosphere kinetics, astrophysics, abrasion metallurgy, etc. This introductory article contains explanations of the database and the means to use it, its sources, ways of calculation, and assessments of the accuracy of data.

Selected laboratory evaluations of the whole-water sample-splitting capabilities of a prototype fourteen-liter Teflon churn splitter

Science.gov (United States)

Horowitz, A.J.; Smith, J.J.; Elrick, K.A.

2001-01-01

A prototype 14-L Teflon? churn splitter was evaluated for whole-water sample-splitting capabilities over a range of sediment concentratons and grain sizes as well as for potential chemical contamination from both organic and inorganic constituents. These evaluations represent a 'best-case' scenario because they were performed in the controlled environment of a laboratory, and used monomineralic silica sand slurries of known concentration made up in deionized water. Further, all splitting was performed by a single operator, and all the requisite concentration analyses were performed by a single laboratory. The prototype Teflon? churn splitter did not appear to supply significant concentrations of either organic or inorganic contaminants at current U.S. Geological Survey (USGS) National Water Quality Laboratory detection and reporting limits when test samples were prepared using current USGS protocols. As with the polyethylene equivalent of the prototype Teflon? churn, the maximum usable whole-water suspended sediment concentration for the prototype churn appears to lie between 1,000 and 10,000 milligrams per liter (mg/L). Further, the maximum grain-size limit appears to lie between 125- and 250-microns (m). Tests to determine the efficacy of the valve baffle indicate that it must be retained to facilitate representative whole-water subsampling.

Printed assemblies of GaAs photoelectrodes with decoupled optical and reactive interfaces for unassisted solar water splitting

Science.gov (United States)

Kang, Dongseok; Young, James L.; Lim, Haneol; Klein, Walter E.; Chen, Huandong; Xi, Yuzhou; Gai, Boju; Deutsch, Todd G.; Yoon, Jongseung

2017-03-01

Despite their excellent photophysical properties and record-high solar-to-hydrogen conversion efficiency, the high cost and limited stability of III-V compound semiconductors prohibit their practical application in solar-driven photoelectrochemical water splitting. Here we present a strategy for III-V photocatalysis that can circumvent these difficulties via printed assemblies of epitaxially grown compound semiconductors. A thin film stack of GaAs-based epitaxial materials is released from the growth wafer and printed onto a non-native transparent substrate to form an integrated photocatalytic electrode for solar hydrogen generation. The heterogeneously integrated electrode configuration together with specialized epitaxial design serve to decouple the material interfaces for illumination and electrocatalysis. Subsequently, this allows independent control and optimization of light absorption, carrier transport, charge transfer, and material stability. Using this approach, we construct a series-connected wireless tandem system of GaAs photoelectrodes and demonstrate 13.1% solar-to-hydrogen conversion efficiency of unassisted-mode water splitting.

Black Phosphorus: Critical Review and Potential for Water Splitting Photocatalyst

Directory of Open Access Journals (Sweden)

Tae Hyung Lee

2016-10-01

Full Text Available A century after its first synthesis in 1914, black phosphorus has been attracting significant attention as a promising two-dimensional material in recent years due to its unique properties. Nowadays, with the development of its exfoliation method, there are extensive applications of black phosphorus in transistors, batteries and optoelectronics. Though, because of its hardship in mass production and stability problems, the potential of the black phosphorus in various fields is left unexplored. Here, we provide a comprehensive review of crystal structure, electronic, optical properties and synthesis of black phosphorus. Recent research works about the applications of black phosphorus is summarized. Among them, the possibility of black phosphorous as a solar water splitting photocatalyst is mainly discussed and the feasible novel structure of photocatalysts based on black phosphorous is proposed.

Mimicking Natural Photosynthesis: Solar to Renewable H2 Fuel Synthesis by Z-Scheme Water Splitting Systems.

Science.gov (United States)

Wang, Yiou; Suzuki, Hajime; Xie, Jijia; Tomita, Osamu; Martin, David James; Higashi, Masanobu; Kong, Dan; Abe, Ryu; Tang, Junwang

2018-05-23

Visible light-driven water splitting using cheap and robust photocatalysts is one of the most exciting ways to produce clean and renewable energy for future generations. Cutting edge research within the field focuses on so-called "Z-scheme" systems, which are inspired by the photosystem II-photosystem I (PSII/PSI) coupling from natural photosynthesis. A Z-scheme system comprises two photocatalysts and generates two sets of charge carriers, splitting water into its constituent parts, hydrogen and oxygen, at separate locations. This is not only more efficient than using a single photocatalyst, but practically it could also be safer. Researchers within the field are constantly aiming to bring systems toward industrial level efficiencies by maximizing light absorption of the materials, engineering more stable redox couples, and also searching for new hydrogen and oxygen evolution cocatalysts. This review provides an in-depth survey of relevant Z-schemes from past to present, with particular focus on mechanistic breakthroughs, and highlights current state of the art systems which are at the forefront of the field.

MOF-derived Co-doped nickel selenide/C electrocatalysts supported on Ni foam for overall water splitting

KAUST Repository

Ming, Fangwang; Liang, Hanfeng; Shi, Huanhuan; Xu, Xun; Mei, Gui; Wang, Zhoucheng

2016-01-01

It is of prime importance to develop dual-functional electrocatalysts with good activity for overall water splitting, which remains a great challenge. Herein, we report the synthesis of a Co-doped nickel selenide (a mixture of NiSe and NiSe)/C hybrid nanostructure supported on Ni foam using a metal-organic framework as the precursor. The resulting catalyst exhibits excellent catalytic activity toward the oxygen evolution reaction (OER), which only requires an overpotential of 275 mV to drive a current density of 30 mA cm. This overpotential is much lower than those reported for precious metal free OER catalysts. The hybrid is also capable of catalyzing the hydrogen evolution reaction (HER) efficiently. A current density of -10 mA cm can be achieved at 90 mV. In addition, such a hybrid nanostructure can achieve 10 and 30 mA cm at potentials of 1.6 and 1.71 V, respectively, along with good durability when functioning as both the cathode and the anode for overall water splitting in basic media.

MOF-derived Co-doped nickel selenide/C electrocatalysts supported on Ni foam for overall water splitting

KAUST Repository

Ming, Fangwang

2016-09-01

It is of prime importance to develop dual-functional electrocatalysts with good activity for overall water splitting, which remains a great challenge. Herein, we report the synthesis of a Co-doped nickel selenide (a mixture of NiSe and NiSe)/C hybrid nanostructure supported on Ni foam using a metal-organic framework as the precursor. The resulting catalyst exhibits excellent catalytic activity toward the oxygen evolution reaction (OER), which only requires an overpotential of 275 mV to drive a current density of 30 mA cm. This overpotential is much lower than those reported for precious metal free OER catalysts. The hybrid is also capable of catalyzing the hydrogen evolution reaction (HER) efficiently. A current density of -10 mA cm can be achieved at 90 mV. In addition, such a hybrid nanostructure can achieve 10 and 30 mA cm at potentials of 1.6 and 1.71 V, respectively, along with good durability when functioning as both the cathode and the anode for overall water splitting in basic media.

Thermodynamic evaluation of the Kalina split-cycle concepts for waste heat recovery applications

International Nuclear Information System (INIS)

Nguyen, Tuong-Van; Knudsen, Thomas; Larsen, Ulrik; Haglind, Fredrik

2014-01-01

The Kalina split-cycle is a thermodynamic process for converting thermal energy into electrical power. It uses an ammonia–water mixture as a working fluid (like a conventional Kalina cycle) and has a varying ammonia concentration during the pre-heating and evaporation steps. This second feature results in an improved match between the heat source and working fluid temperature profiles, decreasing the entropy generation in the heat recovery system. The present work compares the thermodynamic performance of this power cycle with the conventional Kalina process, and investigates the impact of varying boundary conditions by conducting an exergy analysis. The design parameters of each configuration were determined by performing a multi-variable optimisation. The results indicate that the Kalina split-cycle with reheat presents an exergetic efficiency by 2.8% points higher than a reference Kalina cycle with reheat, and by 4.3% points without reheat. The cycle efficiency varies by 14% points for a variation of the exhaust gas temperature of 100 °C, and by 1% point for a cold water temperature variation of 30 °C. This analysis also pinpoints the large irreversibilities in the low-pressure turbine and condenser, and indicates a reduction of the exergy destruction by about 23% in the heat recovery system compared to the baseline cycle. - Highlights: • The thermodynamic performance of the Kalina split-cycle is assessed. • The Kalina split-cycle is compared to the Kalina cycle, with and without reheat. • An exergy analysis is performed to evaluate its thermodynamic performance. • The impact of varying boundary conditions is investigated. • The Kalina split-cycle displays high exergetic efficiency for low- and medium-temperature applications

Review of WO3 thin film preparation for photoelectrochemical water splitting

International Nuclear Information System (INIS)

Ehsan Eftekhari; Mohammad Kassim

2009-01-01

Full text: Tungsten trioxide (WO 3 ), which is one of the most essential materials in our daily life has appeared as an excellent photo electrode material for environmental purification. The nano-size of WO 3 thin film water-splitting technology has great potential for environmentally friendly solar-hydrogen production for the future hydrogen economy. There are several methods for producing tungsten oxide film. In this review, we outlined several WO 3 thin film preparation methods such as doctor Bladding, sputtering, layer-by-layer brush painting, spray pyrolysis deposition, sol-gel and other methods. Here we compare the maximum photocurrent obtained, different condition for preparation of WO 3 thin film and characterization outcome. (author)

Water And Waste Water Processing

International Nuclear Information System (INIS)

Yang, Byeong Ju

1988-04-01

This book shows US the distribution diagram of water and waste water processing with device of water processing, and device of waste water processing, property of water quality like measurement of pollution of waste water, theoretical Oxygen demand, and chemical Oxygen demand, processing speed like zero-order reactions and enzyme reactions, physical processing of water and waste water, chemical processing of water and waste water like neutralization and buffering effect, biological processing of waste water, ammonia removal, and sludges processing.

Use of carbon dioxide as a reaction medium in the thermo-chemical process for the enhanced generation of syngas and tuning adsorption ability of biochar

International Nuclear Information System (INIS)

Cho, Dong-Wan; Kwon, Eilhann E.; Song, Hocheol

2016-01-01

Highlights: • Utilizing CO_2 as a reaction medium in thermo-chemical conversion of aquatic biomass. • Enhanced generation of syngas in the presence of CO_2. • Considerable reduction of pyrolytic oil in CO_2-assisted pyrolysis. • Generation of biochar with high surface area and more porous structure by CO_2. - Abstract: This study mechanistically investigated the influences of CO_2 on syngas (H_2 and CO) production during thermo-chemical conversion of red seaweed, and further explored the possible utility of the produced biochar as a medium for adsorption of inorganic/organic contaminants in aqueous phase. In order to elucidate the key roles of CO_2 in the thermo-chemical process, the composition analysis of syngas and the qualitative analysis of pyrolytic oil were conducted and compared with those in pyrolysis in N_2 condition. Pyrolysis of red seaweed in the presence of CO_2 led to the enhanced generation of syngas at the entire experimental temperatures. For example, the ratio of CO to H_2 in the presence of CO_2 at 620 °C was enhanced by ∼400%, as compared to the case in N_2. This enhanced generation of syngas resulted in significant pyrolytic oil reduction by ∼70% at 620 °C via the unknown reactions between VOCs and CO_2. In addition, biochar generated in the CO_2 environment exhibited comparatively higher surface area (61 m"2 g"−"1) and more porous structure. The morphological modification induced by CO_2 provided the favorable condition for removal of methylene blue from the aqueous phase. Thus, this study experimentally demonstrated that exploiting CO_2 as a reaction medium would provide an attractive option for the enhanced generation of syngas and the tuned adsorption capability of biochar.

About one discrete model of splitting by the physical processes of a piezoconductive medium with gas hydrate inclusions

Science.gov (United States)

Poveshchenko, Yu A.; Podryga, V. O.; Rahimly, P. I.; Sharova, Yu S.

2018-01-01

The thermodynamically equilibrium model for splitting by the physical processes of a two-component three-phase filtration fluid dynamics with gas hydrate inclusions is considered in the paper, for which a family of two-layer completely conservative difference schemes of the support operators method with time weights profiled in space is constructed. On the irregular grids of the theory of the support-operators method applied to the specifics of the processes of transfer of saturations and internal energies of water and gas in a medium with gas hydrate inclusions, methods of directwind approximation of these processes are considered. These approximations preserve the continual properties of divergence-gradient operations in their difference form and are related to the velocity field providing saturations transfer and internal energies of fluids. Fluid dynamics with gas hydrate inclusions are also calculated on the basis of the proposed approach, in particular, in areas of severe pressure depression in the collector space.

Photoelectrochemical water splitting with mesoporous hematite prepared by a solution-based colloidal approach.

Science.gov (United States)

Sivula, Kevin; Zboril, Radek; Le Formal, Florian; Robert, Rosa; Weidenkaff, Anke; Tucek, Jiri; Frydrych, Jiri; Grätzel, Michael

2010-06-02

Sustainable hydrogen production through photoelectrochemical water splitting using hematite (alpha-Fe(2)O(3)) is a promising approach for the chemical storage of solar energy, but is complicated by the material's nonoptimal optoelectronic properties. Nanostructuring approaches have been shown to increase the performance of hematite, but the ideal nanostructure giving high efficiencies for all absorbed light wavelengths remains elusive. Here, we report for the first time mesoporous hematite photoelectodes prepared by a solution-based colloidal method which yield water-splitting photocurrents of 0.56 mA cm(-2) under standard conditions (AM 1.5G 100 mW cm(-2), 1.23 V vs reversible hydrogen electrode, RHE) and over 1.0 mA cm(-2) before the dark current onset (1.55 V vs RHE). The sintering temperature is found to increase the average particle size, and have a drastic effect on the photoactivity. X-ray photoelectron spectroscopy and magnetic measurements using a SQUID magnetometer link this effect to the diffusion and incorporation of dopant atoms from the transparent conducting substrate. In addition, examining the optical properties of the films reveals a considerable change in the absorption coefficient and onset properties, critical aspects for hematite as a solar energy converter, as a function of the sintering temperature. A detailed investigation into hematite's crystal structure using powder X-ray diffraction with Rietveld refinement to account for these effects correlates an increase in a C(3v)-type crystal lattice distortion to the improved optical properties.

TEA: A CODE CALCULATING THERMOCHEMICAL EQUILIBRIUM ABUNDANCES

Energy Technology Data Exchange (ETDEWEB)

Blecic, Jasmina; Harrington, Joseph; Bowman, M. Oliver, E-mail: jasmina@physics.ucf.edu [Planetary Sciences Group, Department of Physics, University of Central Florida, Orlando, FL 32816-2385 (United States)

2016-07-01

We present an open-source Thermochemical Equilibrium Abundances (TEA) code that calculates the abundances of gaseous molecular species. The code is based on the methodology of White et al. and Eriksson. It applies Gibbs free-energy minimization using an iterative, Lagrangian optimization scheme. Given elemental abundances, TEA calculates molecular abundances for a particular temperature and pressure or a list of temperature–pressure pairs. We tested the code against the method of Burrows and Sharp, the free thermochemical equilibrium code Chemical Equilibrium with Applications (CEA), and the example given by Burrows and Sharp. Using their thermodynamic data, TEA reproduces their final abundances, but with higher precision. We also applied the TEA abundance calculations to models of several hot-Jupiter exoplanets, producing expected results. TEA is written in Python in a modular format. There is a start guide, a user manual, and a code document in addition to this theory paper. TEA is available under a reproducible-research, open-source license via https://github.com/dzesmin/TEA.

TEA: A CODE CALCULATING THERMOCHEMICAL EQUILIBRIUM ABUNDANCES

International Nuclear Information System (INIS)

Blecic, Jasmina; Harrington, Joseph; Bowman, M. Oliver

2016-01-01

We present an open-source Thermochemical Equilibrium Abundances (TEA) code that calculates the abundances of gaseous molecular species. The code is based on the methodology of White et al. and Eriksson. It applies Gibbs free-energy minimization using an iterative, Lagrangian optimization scheme. Given elemental abundances, TEA calculates molecular abundances for a particular temperature and pressure or a list of temperature–pressure pairs. We tested the code against the method of Burrows and Sharp, the free thermochemical equilibrium code Chemical Equilibrium with Applications (CEA), and the example given by Burrows and Sharp. Using their thermodynamic data, TEA reproduces their final abundances, but with higher precision. We also applied the TEA abundance calculations to models of several hot-Jupiter exoplanets, producing expected results. TEA is written in Python in a modular format. There is a start guide, a user manual, and a code document in addition to this theory paper. TEA is available under a reproducible-research, open-source license via https://github.com/dzesmin/TEA.

A Simulation Study of Inter Heat Exchanger Process in SI Cycle Process for Hydrogen Production

International Nuclear Information System (INIS)

Shin, Jae Sun; Cho, Sung Jin; Choi, Suk Hoon; Qasim, Faraz; Lee, Euy Soo; Park, Sang Jin; Lee, Heung N.; Park, Jae Ho; Lee, Won Jae

2014-01-01

SI Cyclic process is one of the thermochemical hydrogen production processes using iodine and sulfur for producing hydrogen molecules from water. VHTR (Very High Temperature Reactor) can be used to supply heat to hydrogen production process, which is a high temperature nuclear reactor. IHX (Intermediate Heat Exchanger) is necessary to transfer heat to hydrogen production process safely without radioactivity. In this study, the strategy for the optimum design of IHX between SI hydrogen process and VHTR is proposed for various operating pressures of the reactor, and the different cooling fluids. Most economical efficiency of IHX is also proposed along with process conditions

Novel microwave-assisted synthesis of porous g-C3N4/SnO2 nanocomposite for solar water-splitting

Science.gov (United States)

Seza, A.; Soleimani, F.; Naseri, N.; Soltaninejad, M.; Montazeri, S. M.; Sadrnezhaad, S. K.; Mohammadi, M. R.; Moghadam, H. Asgari; Forouzandeh, M.; Amin, M. H.

2018-05-01

Highly porous nanocomposites of graphitic-carbon nitride and tin oxide (g-C3N4/SnO2) were prepared through simple pyrolysis of urea molecules under microwave irradiation. The initial amount of tin was varied in order to investigate the effect of SnO2 content on preparation and properties of the composites. The synthesized nanocomposites were well-characterized by XRD, FE-SEM, HR-TEM, BET, FTIR, XPS, DRS, and PL. A homogeneous distribution of SnO2 nanoparticles with the size of less than 10 nm on the porous C3N4 sheets could be obtained, suggesting that in-situ synthesis of SnO2 nanoparticles was responsible for the formation of g-C3N4. The process likely occurred by the aid of the large amounts of OH groups formed on the surfaces of SnO2 nanoparticles during the polycondensation reactions of tin derivatives which could facilitate the pyrolysis of urea to carbon nitride. The porous nanocomposite prepared with initial tin amount of 0.175 g had high specific surface area of 195 m2 g-1 which showed high efficiency photoelectrochemical water-splitting ability. A maximum photocurrent density of 33 μA cm-2 was achieved at an applied potential of 0.5 V when testing this nanocomposite as photo-anode in water-splitting reactions under simulated visible light irradiation, introducing it as a promising visible light photoactive material.

Embryo splitting

Directory of Open Access Journals (Sweden)

Karl Illmensee

2010-04-01

Full Text Available Mammalian embryo splitting has successfully been established in farm animals. Embryo splitting is safely and efficiently used for assisted reproduction in several livestock species. In the mouse, efficient embryo splitting as well as single blastomere cloning have been developed in this animal system. In nonhuman primates embryo splitting has resulted in several pregnancies. Human embryo splitting has been reported recently. Microsurgical embryo splitting under Institutional Review Board approval has been carried out to determine its efficiency for blastocyst development. Embryo splitting at the 6–8 cell stage provided a much higher developmental efficiency compared to splitting at the 2–5 cell stage. Embryo splitting may be advantageous for providing additional embryos to be cryopreserved and for patients with low response to hormonal stimulation in assisted reproduction programs. Social and ethical issues concerning embryo splitting are included regarding ethics committee guidelines. Prognostic perspectives are presented for human embryo splitting in reproductive medicine.

Synfuels from fusion: using the tandem mirror reactor and a thermochemical cycle to produce hydrogen

International Nuclear Information System (INIS)

Werner, R.W.

1982-01-01

This study is concerned with the following area: (1) the tandem mirror reactor and its physics; (2) energy balance; (3) the lithium oxide canister blanket system; (4) high-temperature blanket; (5) energy transport system-reactor to process; (6) thermochemical hydrogen processes; (7) interfacing the GA cycle; (8) matching power and temperature demands; (9) preliminary cost estimates; (10) synfuels beyond hydrogen; and (11) thermodynamics of the H 2 SO 4 -H 2 O system

Thermochemical ablation therapy of VX2 tumor using a permeable oil-packed liquid alkali metal.

Directory of Open Access Journals (Sweden)

Ziyi Guo

Full Text Available Alkali metal appears to be a promising tool in thermochemical ablation, but, it requires additional data on safety is required. The objective of this study was to explore the effectiveness of permeable oil-packed liquid alkali metal in the thermochemical ablation of tumors.Permeable oil-packed sodium-potassium (NaK was prepared using ultrasonic mixing of different ratios of metal to oil. The thermal effect of the mixture during ablation of muscle tissue ex vivo was evaluated using the Fluke Ti400 Thermal Imager. The thermochemical effect of the NaK-oil mixture on VX2 tumors was evaluated by performing perfusion CT scans both before and after treatment in 10 VX2 rabbit model tumors. VX2 tumors were harvested from two rabbits immediately after treatment to assess their viability using trypan blue and hematoxylin and eosin (H.E. staining.The injection of the NaK-oil mixture resulted in significantly higher heat in the ablation areas. The permeable oil controlled the rate of heat released during the NaK reaction with water in the living tissue. Perfusion computed tomography and its parameter map confirmed that the NaK-oil mixture had curative effects on VX2 tumors. Both trypan blue and H.E. staining showed partial necrosis of the VX2 tumors.The NaK-oil mixture may be used successfully to ablate tumor tissue in vivo. With reference to the controlled thermal and chemical lethal injury to tumors, using a liquid alkali in ablation is potentially an effective and safe method to treat malignant tumors.

Analysis of Efficiency of the Ship Propulsion System with Thermochemical Recuperation of Waste Heat

Science.gov (United States)

Cherednichenko, Oleksandr; Serbin, Serhiy

2018-03-01

One of the basic ways to reduce polluting emissions of ship power plants is application of innovative devices for on-board energy generation by means of secondary energy resources. The combined gas turbine and diesel engine plant with thermochemical recuperation of the heat of secondary energy resources has been considered. It is suggested to conduct the study with the help of mathematical modeling methods. The model takes into account basic physical correlations, material and thermal balances, phase equilibrium, and heat and mass transfer processes. The paper provides the results of mathematical modeling of the processes in a gas turbine and diesel engine power plant with thermochemical recuperation of the gas turbine exhaust gas heat by converting a hydrocarbon fuel. In such a plant, it is possible to reduce the specific fuel consumption of the diesel engine by 20%. The waste heat potential in a gas turbine can provide efficient hydrocarbon fuel conversion at the ratio of powers of the diesel and gas turbine engines being up to 6. When the diesel engine and gas turbine operate simultaneously with the use of the LNG vapor conversion products, the efficiency coefficient of the plant increases by 4-5%.

Environmental requirements in thermochemical and biochemical conversion of biomass

International Nuclear Information System (INIS)

Frings, R.M.; Mackie, K.L.; Hunter, I.R.

1992-01-01

Many biological and thermochemical processing options exist for the conversion of biomass to fuels. Commercially, these options are assessed in terms of fuel product yield and quality. However, attention must also be paid to the environmental aspects of each technology so that any commercial plant can meet the increasingly stringent environmental legislation in the world today. The environmental aspects of biological conversion (biogasification and bioliquefaction) and thermal conversion (high pressure liquefaction, flash pyrolysis, and gasification) are reviewed. Biological conversion processes are likely to generate waste streams which are more treatable than those from thermal conversion processes but the available data for thermal liquefaction are very limited. Close attention to waste minimisation is recommended and processing options that greatly reduce or eliminate waste streams have been identified. Product upgrading and its effect on wastewater quality also requires attention. Emphasis in further research studies needs to be placed on providing authentic waste streams for environmental assessment. (author)

South Africa's opportunity to maximise the role of nuclear power in a global hydrogen economy

Energy Technology Data Exchange (ETDEWEB)

Greyvenstein, R. [Pebble Bed Modular Reactor (PBMR) (Pty) Ltd. (South Africa)], E-mail: renee.greyvenstein@pbmr.co.za; Correia, M. [Pebble Bed Modular Reactor (PBMR) (Pty) Ltd. (South Africa)], E-mail: michael.correia@pbmr.co.za; Kriel, W. [Pebble Bed Modular Reactor (PBMR) (Pty) Ltd. (South Africa)], E-mail: willem.kriel@pbmr.us

2008-11-15

Global concern for increased energy demand, increased cost of natural gas and petroleum, energy security and environmental degradation are leading to heightened interest in using nuclear energy and hydrogen to leverage existing hydrocarbon reserves. The wasteful use of hydrocarbons can be minimised by using nuclear as a source of energy and water as a source of hydrogen. Virtually all hydrogen today is produced from fossil fuels, which give rise to CO{sub 2} emissions. Hydrogen can be cleanly produced from water (without CO{sub 2} pollution) by using nuclear energy to generate the required electricity and/or process heat to split the water molecule. Once the clean hydrogen has been produced, it can be used as feedstock to fuel cell technologies, or in the nearer term as feedstock to a coal-to-liquids process to produce cleaner synthetic liquid fuels. Clean liquid fuels from coal - using hydrogen generated from nuclear energy - is an intermediate step for using hydrogen to reduce pollution in the transport sector; simultaneously addressing energy security concerns. Several promising water-splitting technologies have been identified. Thermo-chemical water-splitting and high-temperature steam electrolysis technologies require process temperatures in the range of 850 deg. C and higher for the efficient production of hydrogen. The pebble bed modular reactor (PBMR), under development in South Africa, is ideally suited to generate both high-temperature process heat and electricity for the production of hydrogen. This paper will discuss South Africa's opportunity to maximise the use of its nuclear technology and national resources in a global hydrogen economy.

Radioisotope methods of investigations of phenomenons at phases border of steel - atmosphere in gaseous processes of thermochemical treatment of steel

International Nuclear Information System (INIS)

L'utse-Birk, A.; Bel'ski, V.; Vez'ranovski, Eh.; Valis', L.

1979-01-01

Radioisotope methods of investigations of the processes of thermochemical treatment of steels are valuable, and in some cases, the only means for analysis of complicated mechanisms of diffusion, absorption and chemical reactions, going on in some technological processes. New specific methods are stated for investigation of processes on the border between steel and gaseous atmosphere. Quantative method nas been developed for investigation of the kinetics of carbon transfere (labelled by carbon-14) from steel into gases. Hydrocarbons and their derivatives are adsorbed selectivelly and beta-activity of the compound is measured in the presence of liquid scintillators. Limiting detectable amount of carbon equals to 0.5μg. Application of labelled (by radioisotope iron-59) iron in steel has ensured a possibility to determine its participation in reactions with chromium and titanum coating atmospheres. Application of hydrocarbons labelled by carbon-14 in the composition of titanum coating atmosphere has permitted to determine, in comparison with investigation of carbon diffusion in steel, participation of two different carbon sources in the forming of the TiC layer on steel and has led to the optimization of processes, especially for low-carbon steels [ru

Process Design and Economics for Conversion of Lignocellulosic Biomass to Ethanol: Thermochemical Pathway by Indirect Gasification and Mixed Alcohol Synthesis

Energy Technology Data Exchange (ETDEWEB)

Dutta, A.; Talmadge, M.; Hensley, J.; Worley, M.; Dudgeon, D.; Barton, D.; Groendijk, P.; Ferrari, D.; Stears, B.; Searcy, E. M.; Wright, C. T.; Hess, J. R.

2011-05-01

This design report describes an up-to-date benchmark thermochemical conversion process that incorporates the latest research from NREL and other sources. Building on a design report published in 2007, NREL and its subcontractor Harris Group Inc. performed a complete review of the process design and economic model for a biomass-to-ethanol process via indirect gasification. The conceptual design presented herein considers the economics of ethanol production, assuming the achievement of internal research targets for 2012 and nth-plant costs and financing. The design features a processing capacity of 2,205 U.S. tons (2,000 metric tonnes) of dry biomass per day and an ethanol yield of 83.8 gallons per dry U.S. ton of feedstock. The ethanol selling price corresponding to this design is $2.05 per gallon in 2007 dollars, assuming a 30-year plant life and 40% equity financing with a 10% internal rate of return and the remaining 60% debt financed at 8% interest. This ethanol selling price corresponds to a gasoline equivalent price of $3.11 per gallon based on the relative volumetric energy contents of ethanol and gasoline.

Thermochemical treatment of the pay zone in the well RK-3

Energy Technology Data Exchange (ETDEWEB)

Labudovic, V

1970-02-01

The elements are given for the calculation of the thermochemical treatment of the Well RK-3. From the diagram, the Mg and HCl reaction velocity vs. pressure and the temperature vs. the quantity of the reacted CaCO/sub 3/ can be read out. These are important elements for the calculation of a thermochemical treatment. A comparison of calculated and measured temperatures and the factors influencing the heat conductivity of the formation rock is given. The heating range at formation depths is calculated. The relation quantity of warm acid vs. injection pressure also is given.

TiO2/Cu2O composite based on TiO2 NTPC photoanode for photoelectrochemical (PEC) water splitting under visible light

KAUST Repository

Shi, Le

2015-05-01

Water splitting through photoelectrochemical reaction is widely regarded as a major method to generate H2 , a promising source of renewable energy to deal with the energy crisis faced up to human being. Efficient exploitation of visible light in practice of water splitting with pure TiO2 material, one of the most popular semiconductor material used for photoelectrochemical water splitting, is still challenging. One dimensional TiO2 nanotubes is highly desired with its less recombination with the short distance for charge carrier diffusion and light-scattering properties. This work is based on TiO2 NTPC electrode by the optimized two-step anodization method from our group. A highly crystalized p-type Cu2O layer was deposited by optimized pulse potentiostatic electrochemical deposition onto TiO2 nanotubes to enhance the visible light absorption of a pure p-type TiO2 substrate and to build a p-n junction at the interface to improve the PEC performance. However, because of the real photocurrent of Cu2O is far away from its theoretical limit and also poor stability in the aqueous environment, a design of rGO medium layer was added between TiO2 nanotube and Cu2O layer to enhance the photogenerated electrons and holes separation, extend charge carrier diffusion length (in comparison with those of conventional pure TiO2 or Cu2O materials) which could significantly increase photocurrent to 0.65 mA/cm2 under visible light illumination (>420 nm) and also largely improve the stability of Cu2O layer, finally lead to an enhancement of water splitting performance.

Hierarchical (Ni,Co)Se 2 /Carbon Hollow Rhombic Dodecahedra Derived from Metal-Organic Frameworks for Efficient Water-Splitting Electrocatalysis

KAUST Repository

Ming, Fangwang

2017-08-12

In this work, we demonstrate that the electrocatalytic activity of transition metal chalcogenides can be greatly enhanced by simultaneously engineering the active sites, surface area, and conductivity. Using metal-organic frameworks-derived (Ni,Co)Se2/C hollow rhombic dodecahedra (HRD) as a demonstration, we show that the incorporation of Ni into CoSe2 could generates additional active sites, the hierarchical hollow structure promotes the electrolyte diffusion, the in-situ hybridization with C improves the conductivity. As a result, the (Ni,Co)Se2/C HRD exhibit superior performance toward the overall water-splitting electrocatalysis in 1M KOH with a cell voltage as low as 1.58V at the current density of 10mAcm−2, making the (Ni,Co)Se2/C HRD as a promising alternative to noble metal catalysts for water splitting.

Hierarchical (Ni,Co)Se 2 /Carbon Hollow Rhombic Dodecahedra Derived from Metal-Organic Frameworks for Efficient Water-Splitting Electrocatalysis

KAUST Repository

Ming, Fangwang; Liang, Hanfeng; Shi, Huanhuan; Mei, Gui; Xu, Xun; Wang, Zhoucheng

2017-01-01

In this work, we demonstrate that the electrocatalytic activity of transition metal chalcogenides can be greatly enhanced by simultaneously engineering the active sites, surface area, and conductivity. Using metal-organic frameworks-derived (Ni,Co)Se2/C hollow rhombic dodecahedra (HRD) as a demonstration, we show that the incorporation of Ni into CoSe2 could generates additional active sites, the hierarchical hollow structure promotes the electrolyte diffusion, the in-situ hybridization with C improves the conductivity. As a result, the (Ni,Co)Se2/C HRD exhibit superior performance toward the overall water-splitting electrocatalysis in 1M KOH with a cell voltage as low as 1.58V at the current density of 10mAcm−2, making the (Ni,Co)Se2/C HRD as a promising alternative to noble metal catalysts for water splitting.

Effects of Zn2+ and Pb2+ dopants on the activity of Ga2O3-based photocatalysts for water splitting.

Science.gov (United States)

Wang, Xiang; Shen, Shuai; Jin, Shaoqing; Yang, Jingxiu; Li, Mingrun; Wang, Xiuli; Han, Hongxian; Li, Can

2013-11-28

Zn-doped and Pb-doped β-Ga2O3-based photocatalysts were prepared by an impregnation method. The photocatalyst based on the Zn-doped β-Ga2O3 shows a greatly enhanced activity in water splitting while the Pb-doped β-Ga2O3 one shows a dramatic decrease in activity. The effects of Zn(2+) and Pb(2+) dopants on the activity of Ga2O3-based photocatalysts for water splitting were investigated by HRTEM, XPS and time-resolved IR spectroscopy. A ZnGa2O4-β-Ga2O3 heterojunction is formed in the surface region of the Zn-doped β-Ga2O3 and a slower decay of photogenerated electrons is observed. The ZnGa2O4-β-Ga2O3 heterojunction exhibits type-II band alignment and facilitates charge separation, thus leading to an enhanced photocatalytic activity for water splitting. Unlike Zn(2+) ions, Pb(2+) ions are coordinated by oxygen atoms to form polyhedra as dopants, resulting in distorted surface structure and fast decay of photogenerated electrons of β-Ga2O3. These results suggest that the Pb dopants act as charge recombination centers expediting the recombination of photogenerated electrons and holes, thus decreasing the photocatalytic activity.

Ni nanotube array-based electrodes by electrochemical alloying and de-alloying for efficient water splitting.

Science.gov (United States)

Teng, Xue; Wang, Jianying; Ji, Lvlv; Lv, Yaokang; Chen, Zuofeng

2018-05-17

The design of cost-efficient earth-abundant catalysts with superior performance for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is extremely important for future renewable energy production. Herein, we report a facile strategy for constructing Ni nanotube arrays (NTAs) on a Ni foam (NF) substrate through cathodic deposition of NiCu alloy followed by anodic stripping of metallic Cu. Based on Ni NTAs, the as-prepared NiSe2 NTA electrode by NiSe2 electrodeposition and the NiFeOx NTA electrode by dipping in Fe3+ solution exhibit excellent HER and OER performance in alkaline conditions. In these systems, Ni NTAs act as a binder-free multifunctional inner layer to support the electrocatalysts, offer a large specific surface area and serve as a fast electron transport pathway. Moreover, an alkaline electrolyzer has been constructed using NiFeOx NTAs as the anode and NiSe2 NTAs as the cathode, which only demands a cell voltage of 1.78 V to deliver a water-splitting current density of 500 mA cm-2, and demonstrates remarkable stability during long-term electrolysis. This work provides an attractive method for the design and fabrication of nanotube array-based catalyst electrodes for highly efficient water-splitting.

A Split-Attention Effect in Multimedia Learning: Evidence for Dual Processing Systems in Working Memory.

Science.gov (United States)

Mayer, Richard E.; Moreno, Roxana

1998-01-01

Multimedia learners (n=146 college students) were able to integrate words and computer-presented pictures more easily when the words were presented aurally rather than visually. This split-attention effect is consistent with a dual-processing model of working memory. (SLD)

Understanding river dune splitting through flume experiments and analysis of a dune evolution model

NARCIS (Netherlands)

Warmink, Jord Jurriaan; Dohmen-Janssen, Catarine M.; Lansink, Jord; Naqshband, Suleyman; van Duin, Olav; Paarlberg, Andries; Termes, A.P.P.; Hulscher, Suzanne J.M.H.

2014-01-01

Forecasts of water level during river floods require accurate predictions of the evolution of river dune dimensions, because the hydraulic roughness of the main channel is largely determined by the bed morphology. River dune dimensions are controlled by processes like merging and splitting of dunes.

Cool covered sky-splitting spectrum-splitting FK

Energy Technology Data Exchange (ETDEWEB)

Mohedano, Rubén; Chaves, Julio; Falicoff, Waqidi; Hernandez, Maikel; Sorgato, Simone [LPI, Altadena, CA, USA and Madrid (Spain); Miñano, Juan C.; Benitez, Pablo [LPI, Altadena, CA, USA and Madrid, Spain and Universidad Politécnica de Madrid (UPM), Madrid (Spain); Buljan, Marina [Universidad Politécnica de Madrid (UPM), Madrid (Spain)

2014-09-26

Placing a plane mirror between the primary lens and the receiver in a Fresnel Köhler (FK) concentrator gives birth to a quite different CPV system where all the high-tech components sit on a common plane, that of the primary lens panels. The idea enables not only a thinner device (a half of the original) but also a low cost 1-step manufacturing process for the optics, automatic alignment of primary and secondary lenses, and cell/wiring protection. The concept is also compatible with two different techniques to increase the module efficiency: spectrum splitting between a 3J and a BPC Silicon cell for better usage of Direct Normal Irradiance DNI, and sky splitting to harvest the energy of the diffuse radiation and higher energy production throughout the year. Simple calculations forecast the module would convert 45% of the DNI into electricity.

Synfuels from fusion: using the tandem mirror reactor and a thermochemical cycle to produce hydrogen

Energy Technology Data Exchange (ETDEWEB)

Werner, R.W. (ed.)

1982-11-01

This study is concerned with the following area: (1) the tandem mirror reactor and its physics; (2) energy balance; (3) the lithium oxide canister blanket system; (4) high-temperature blanket; (5) energy transport system-reactor to process; (6) thermochemical hydrogen processes; (7) interfacing the GA cycle; (8) matching power and temperature demands; (9) preliminary cost estimates; (10) synfuels beyond hydrogen; and (11) thermodynamics of the H/sub 2/SO/sub 4/-H/sub 2/O system. (MOW)

Effect of sodium carbonate catalyst weight on production of bio-oil via thermochemical liquefaction of corncobs in ethanol-water solution

Science.gov (United States)

Sembodo, Bregas Siswahjono Tatag; Sulistyo, Hary; Sediawan, Wahyudi Budi; Fahrurrozi, Mohammad

2018-02-01

Lignocellulosic biomass has recently received serious attention as an energy source that can replace fossil fuels. Corncob is one of lignocellulosic biomass wastes, which can be further processed into bio-oil through thermochemical liquefaction process. Bio-oil is expected to be further processed into fuel oil. In this research the effect of Na2CO3 catalyst weight on the yield of bio-oil was investigated. The composition of bio-oil produced in this process was analyzed by GC-MS. Bio-oil formation rate were analyzed through mathematical model development. First model aasumed as an isothermal process, while second model was not. It is found that both models were able to provide a good approach to experimental data. The average reaction rate constants was obtained from isothermal model, while the activation energy level and collision factors were obtained from non-isothermal model. The reaction rate will increase by addition of Na2CO3 (0 - 0.5 g) as catalyst to 250 mL system solution, then the activation energy will decrease from 1964.265 joules/mole to 1029.994 joules/mole. The GC-MS analysis results showed that the bio-oil were contained of ester compounds, phenolic compounds, cyclic compunds, heterocyclic compounds, and poly-alcohols compounds.