Numerical evaluation of a novel integrated solar reactor for high-temperature H2O electrolysis with high scalability and solar-to-fuel efficiency

Abstract

Solar-driven high temperature H₂O electrolysis provides a promising path for green H₂ production. In this work, a novel integrated solar-driven high temperature H₂O electrolysis reactor was proposed, and its thermal and energy conversion performance was evaluated based on an optical-thermal-chemical coupling model. The results demonstrated that the temperature difference on the tubular SOEC under highly uneven solar radiation can be lowered by the novel multi-layer structure. A solar-to-fuel (STF) efficiency of 23.0 %, which is higher than those from references, was predicted due to close integration/coupling of the various processes in the reactor, and it may still be improved by increasing the direct normal irradiance (DNI) and operation voltage. The results also emphasize the importance of reaction kinetics to the efficiency of the system. Contrary to the thermodynamic estimation based on equilibrium, the efficiency in exothermic mode is shown to be higher than that in endothermic mode owing to way better kinetics of the former. The reactor provides a simple but effective strategy for addressing the temperature gradient caused by the uneven solar radiation and efficient heat exchange/recovery between the heating and electrolysis processes. Its modular design facilitates scaling, optimization and maintenance. The insights shown can be of guiding significance for designing and practical realization of the integrated reactor concept.