Science Applications International and the Florida Solar Energy Center (FSEC) of the University of Central Florida have teamed to investigate advanced thermochemical processes for splitting water to produce hydrogen through a $5M, 4 year program funded by the U.S. Department of Energy. The process is unique in that it involves a “quantum boost,” or photocatalytic sub-process that is expected to produce hydrogen from water at greater than 40% efficiency. FSEC has identified a prospective cycle that employs photocatalysis of ammonium sulfite to ammonium sulfate for hydrogen production, and high temperature decomposition of zinc sulfate to zinc oxide for oxygen generation. The photocatalytic process takes place in aqueous media at low temperatures (60-95^oC) and at approximately one sun. The zinc sulfate decomposition occurs with solids at temperatures exceeding 800^oC.
Because the photocatalytic reaction only uses the ultraviolet/visible portion of the solar spectrum it has been proposed to split the solar beam into high-energy photons and thermal radiation using hot or cold mirrors or other approaches. SAIC has been investigating solar field configurations appropriate to supply solar energy to these processes including heliostat/central receiver, dishes and trough configurations. Due to the cost of hot and cold mirrors, the lowest cost system may result by separating the low-temperature, photocatalytic reactor from the high-temperature decomposition reactor.
This paper discusses the collector field requirements for this thermochemical hydrogen production process, reviews potential collector and reactor configurations and presents a preliminary proposal for a collector configuration and chemical reactor design suitable for the process.