Solar Heat and Power for a SOE process

Abstract

High temperature steam electrolysis (HTSE) in a Solid Oxide Electrolyzer (SOE) involves the splitting of steam into hydrogen and oxygen at high temperatures. The Primary advantage of HTE over conventional low temperature electrolysis is that considerably higher hydrogen production efficiencies can be achieved. Performing the electrolysis process at high temperatures and high pressure results in more favorable thermodynamics for electrolysis, more efficient production of electricity, and allows direct use of process heat to generate steam. This paper related to the EU-JCH project SOPHIA presents the results of process analyses performed to evaluate the hydrogen production efficiencies of an HTSE plant coupled to a Solar Tower working with steam as heat transfer fluid that supplies both the electricity and process heat needed to drive the process. Running the process with direct steam has the benefit of using a heat transfer fluid well suited to generate electricity in a Rankine cycle as well as feed steam for the HTE. Moreover, this process scheme permits the use of steam as sweep gas for the anode in order to maintain reducing conditions. The power conversion unit will be a Rankine steam cycle with a power conversion of 35%.The electrolyser operates at 700°C and 15 bar and utilizes steam as sweep fluid to remove the excess oxygen that is evolved on the anode side. The sweeping steam can be easily separated at the outlet of the electrolyzer by condensation, which offers the benefit of producing oxygen as a valuable byproduct. The Flowsheet of the process has been created and analyzed in addition to the development of a solar test receiver for steam generation accompanied by modeling of this receiver. The receiver was testes in DLR’s high flux solar simulator in Cologne. A tube-type test receiver was developed and tested in DLR’s high flux solar simulator in Cologne.