Potential Applications of Concentrated Solar Photons (1991) / Chapter Skim
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Appendix F: Knowledge Base and Status of Technology of Solar Fuels
Appendix F: Knowledge Base and Status of Technology of Solar Fuels
Pages 69-79
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From page 69... ...
This occurs at wavelengths below 200 am, which are absorbed by water but which solar energy cannot supply. A suitable photocatalytic redox system is therefore required to promote water photolysis utilizing solar energy.
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From page 70... ...
presents advantages with respect to solar energy utilization as it embraces both the heat generated in a solar reactor and the high-energy photons available. Vanous multistage hybrid systems for water decomposition by solar energy have been developed by the Yokohama group in Japan [3,7,81.
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From page 71... ...
(b) The Yokohama Mark VII cycle In the improved Yokohama Mark VII hybrid system [8,93, the cycle has been modified to be: 2Fe3(PO432 ~ 3I2 + 2H3PO4 > 6FePO4 + 6HI (photochemical)
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From page 72... ...
The photochemical reaction and the electrolysis are carried out in a photon-assisted electrolyzer that evolves HI and O2. The light beam passing through the photoelectrochemical cell is collected and heats up the thermoelectric generator which supplies electricity to the electrolyzer, and He wasted heat is also used for the HI .
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From page 73... ...
was performed. If the waste heat were recovered within the process to generate additional steam to drive a unipolar electrolyzer, the production rate for H2 could be doubled to give a total yearly capacity of 344 GJ in equivalent hydrogen.
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From page 74... ...
While detailed cost evaluations have not been done, the Ispra people believe that costs from the Mark processes, with thermal efficiencies greater than 35 percent, would be comparable to the costs for advanced water electrolysis.
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From page 75... ...
doubling the electricity costs increases the solar H2 cost by ~ percent; (5) the cost of the solar H2 vanes from $15 to $70 per GJ of hydrogen the typical cost of solar hydrogen for 15 percent capital charge rate, $10 per GJ of solar thermal energy and $0.02 kWh of electrical energy is about $33 per GJ of hydrogen [a recalculation of the Cristina-Mark process in (b)
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From page 76... ...
decomposition of HI 2HI-> H2 + I2 This process was first devised for nuclear energy to be the primary energy source; overall process thermal efficiency is about 46 percent [141. When the GA process is coupled to a solar thermal heat source, the' hydrogen production costs range from $40 to $50 per GJ of hydrogen for 2333 hours of operation per year, a 27 percent capacity factor and a 20 percent return on investment [141.
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From page 77... ...
Solar thermal energy is competitive for electricity production because energy conversion equipment cost reductions are possible with a clean heat source; for hydrogen production via existing water splitting, equipment costs for solar plants are higher than for plants that consume fossil fuels. Also, known water-splitting processes that convert solar energy to stored chemical energy in hydrogen are less efficient than commercial processes that convert stored energy in fossil fuels to energy in hydrogen [171.
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From page 78... ...
"Solar Hydrogen Production: The Sulfurllod~ne Cycle Versus Water Vapor Electrolysis." P 702 in 21st Proceedings of He Intersocie~r Energy Conversion Engineenng Conference, Amencan Chemical Society, Washington D.C., p.
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From page 79... ...
"A Simulation Study of the UT-3 Thermochemical Hydrogen Production Process." Int.
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