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Title: Solar High Temperature Water-Splitting Cycle with Quantum Boost

Abstract

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 50more » 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 proposed for future activities. Electrolysis membranes that permit higher temperatures and lower voltages are attainable. The oxygen half cycle will need further development and improvement.« less

Authors:
 [1];  [1];  [2];  [2];  [3];  [3];  [4]
+ Show Author Affiliations
  1. SAIC
  2. UCSD
  3. Electrosynthesis Co.
  4. TChemE
Publication Date:
Research Org.:
Science Applications International Corp.
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Fuel Cell Technologies Office (EE-3F)
Contributing Org.:
Florida Solar Energy Center of the University of Central Florida Southern California Gas Company
OSTI Identifier:
1130473
Report Number(s):
DOE-SAIC-17002
DOE Contract Number:
FG36-07GO17002
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; Hydrogen Solar Water-splitting Thermochemical Photocatalytic Electrolytic Heliostats Quantum-boost Electrocatalysts Membranes Electrophoretic deposition Nanoparticles Molten-salt Storage

Citation Formats

Taylor, Robin, Davenport, Roger, Talbot, Jan, Herz, Richard, Genders, David, Symons, Peter, and Brown, Lloyd. Solar High Temperature Water-Splitting Cycle with Quantum Boost. United States: N. p., 2014. Web. doi:10.2172/1130473.
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Taylor, Robin, Davenport, Roger, Talbot, Jan, Herz, Richard, Genders, David, Symons, Peter, & Brown, Lloyd. Solar High Temperature Water-Splitting Cycle with Quantum Boost. United States. doi:10.2172/1130473.
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Taylor, Robin, Davenport, Roger, Talbot, Jan, Herz, Richard, Genders, David, Symons, Peter, and Brown, Lloyd. Fri . "Solar High Temperature Water-Splitting Cycle with Quantum Boost". United States. doi:10.2172/1130473. https://www.osti.gov/servlets/purl/1130473.
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@article{osti_1130473,
title = {Solar High Temperature Water-Splitting Cycle with Quantum Boost},
author = {Taylor, Robin and Davenport, Roger and Talbot, Jan and Herz, Richard and Genders, David and Symons, Peter and Brown, Lloyd},
abstractNote = {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 proposed for future activities. Electrolysis membranes that permit higher temperatures and lower voltages are attainable. The oxygen half cycle will need further development and improvement.},
doi = {10.2172/1130473},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Apr 25 00:00:00 EDT 2014},
month = {Fri Apr 25 00:00:00 EDT 2014}
}
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Technical Report:
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DOI:  10.2172/1130473
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  • ; ;
    A sulfur-sulfuric acid energy storage system is proposed for the General Atomic Company (GA) sulfur-iodine thermochemical water-splitting cycle. In this concept sulfur is burned to sulfur dioxide in air, generating the energy needed for the hydrogen production process at night and during periods of low insolation. The product of the sulfur burning reaction also provides one of the components (SO/sub 2/) of the main water-splitting reaction. Sulfur is produced from SO/sub 2/ and water in a disproportionation reaction which also produces sulfuric acid. The SO/sub 2/ is produced by the solar thermal decomposition of sulfuric acid. The energetics of burningmore » sulfur are a good match to the energy required for running the H/sub 2/ producing plant where 1 mole of S produces 1 mole of SO/sub 2/ which produces one mole of H/sub 2/. During useful insolation periods, the H/sub 2/ producing plant is operated directly from solar energy, H/sub 2/SO/sub 4/ is concentrated, and H/sub 2/SO/sub 4/ is thermally decomposed to SO/sub 2/, O/sub 2/, and H/sub 2/O. This scheme appears to have sufficient economic benefits that it is proposed to use this storage cycle seasonally. It is expected that excess S made during the summer can be used during the winter, allowing the H/sub 2/ production plant to be levelized. It is anticipated from preliminary calculations that the H/sub 2/ production of the solar plant using this chemistry will be accomplished at a thermal efficiency of over 40%. Sizing of the solar thermochemical plant has been addressed. An average 200-MW(th) H/sub 2/ producing plant was selected. The layout of this plant has a mirror field ring surrounding a central plant. Six multipurpose receiver towers are spaced appropriately around the central plant. These features appear to make the sulfur-iodine water-splitting cycle a prime candidate for a hydrogen production process using solar thermal energy.« less

  • ; ; ; ...
    The objective of this work is to identify economically feasible concepts for the production of hydrogen from water using solar energy. The ultimate project objective was to select one or more competitive concepts for pilot-scale demonstration using concentrated solar energy. Results of pilot scale plant performance would be used as foundation for seeking public and private resources for full-scale plant development and testing. Economical success in this venture would afford the public with a renewable and limitless source of energy carrier for use in electric power load-leveling and as a carbon-free transportation fuel. The Solar Hydrogen Generation Research (SHGR) projectmore » embraces technologies relevant to hydrogen research under the Office of Hydrogen Fuel Cells and Infrastructure Technology (HFCIT) as well as concentrated solar power under the Office of Solar Energy Technologies (SET). Although the photoelectrochemical work is aligned with HFCIT, some of the technologies in this effort are also consistent with the skills and technologies found in concentrated solar power and photovoltaic technology under the Office of Solar Energy Technologies (SET). Hydrogen production by thermo-chemical water-splitting is a chemical process that accomplishes the decomposition of water into hydrogen and oxygen using only heat or a combination of heat and electrolysis instead of pure electrolysis and meets the goals for hydrogen production using only water and renewable solar energy as feed-stocks. Photoelectrochemical hydrogen production also meets these goals by implementing photo-electrolysis at the surface of a semiconductor in contact with an electrolyte with bias provided by a photovoltaic source. Here, water splitting is a photo-electrolytic process in which hydrogen is produced using only solar photons and water as feed-stocks. The thermochemical hydrogen task engendered formal collaborations among two universities, three national laboratories and two private sector entities. The photoelectrochemical hydrogen task included formal collaborations with three universities and one national laboratory. The formal participants in these two tasks are listed above. Informal collaborations in both projects included one additional university (the University of Nevada, Reno) and two additional national laboratories (Lawrence Livermore National Laboratory and Lawrence Berkeley National Laboratory).« less

  • The report describes progress made during January to December 1977 of a program to investigate thermochemical water splitting using the high-temperature, gas-cooled reactor (HTGR) as a heat source. Material investigations were directed toward obtaining corrosion test data for metallic and nonmetallic materials in HIx media and establishing weight and surface changes as a function of time. Some metallic, plastic, and elastomeric materials resisted appreciable corrosion in HIx, although many materials screened were rapidly attacked. The refractory metals Ta, Mo, Nb-1 Zr, and Ta-10 W continued to show good resistance to HIx at room and elevated temperatures. Titanium and zirconium lookedmore » promising although titanium was severely attacked in high (82% by weight) 12 content HIx at elevated temperatures. The cast-iron-base alloy Durichlor continued to resist attack at room temperature. The perfluorocarbon elastomer Kalrez swelled only a minor amount and resisted attack at elevated temperature even under boiling condition. Teflon TFE and FEP showed some absorption of HIx with no apparent degradation.« less

  • ; ;
    Solid oxygen passing membranes such as stabilized zirconia were proposed for use as membranes in high temperature water splitting processes. Two-membrane systems, reduced oxygen concentration (ROC), which use a hydrogen passing membrane as well are discussed. An advantage of a two-membrane system is that water may be split in a single passage through the device, thus decreasing substantially thermodynamic losses associated with the heat exchanger and other appurtenances. Some problems such as the stability of hydrogen passing membranes in a water atmosphere are addressed. It is suggested that the ROC process may provide a means of protecting hydrogen passing membranes,more » and that electric ROCs may be unusually well suited for operation at temperatures at which palladium membranes might be used. The thermal efficiencies of two membrane systems with and without electrical enhancement are compared.« less

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