Feasibility of high efficient solar hydrogen generation system integrating photovoltaic cell/photon-enhanced thermionic emission and high-temperature electrolysis cell

The integration of solar photovoltaic (PV) cell and high-temperature electrolysis cell to produce hydrogen is a promising means of solar energy storage and hydrogen harvesting. In this paper, a novel hydrogen production system is proposed by combining PV cell and photon-enhanced thermionic emission cell (PETE) with the solid oxide electrolysis cell (SOEC). The inlet steam of SOEC could be heated to a high temperature ranging from 800 degrees C to 1000 degrees C by the waste heat recovery of the PV cell and PETE module. The high-temperature steam and the electricity produced by PV cell and PETE module are fed into the SOEC together for H-2 generation. High temperature electrolysis could decrease the Gibbs free energy required in water splitting, leading to less electricity cost at the expense of consuming more heat. PV cells can also be more efficient in a relatively low operation temperature by the waste heat recovery, and more electricity would be generated for hydrogen production. The first-law thermodynamic efficiency, solar exergy efficiency and solar-to-hydrogen efficiency (STH efficiency) of this proposed system could reach 77.05%, 55.99%, and 29.61%, respectively, which are expected to provide a theoretic basis for the research and application of convenient and efficient solar hydrogen generation.