A Hybrid Thermochemical–electrochemical Cycle for Efficient Solar Fuel Production

Abstract

To produce high-quality solar fuel, this work proposed a novel chemical looping in which a thermochemical cycle was hybridized with an electrochemical process. Specifically, sunlight was concentrated and split, short and medium solar spectrum was utilized for efficient PV-driven solid oxide electrolysis cell (SOEC), the rest spectrum was converted into heat to drive a three-step chemical looping steam reforming of methane (CLRM) cycle. The three-step CLRM consisted of reduction process with syngas production, oxidation process with hydrogen production, and reoxidation process of the oxygen carrier, respectively. By CLRM providing the reaction heat, the reactant of high-temperature steam and the reducing atmosphere required by cathode for SOEC, and simultaneously, SOEC providing high-temperature O2 for reoxidation process of CLRM, the thermochemical cycle can be well coupled with the electrochemical process and decrease the need for energy input. The design solar energy input to the novel cycle was supposed to be 55.6 MW, the solar-to-fuel efficiency can be expected to be 42.1%. This novel cycle allows the generation of a high-quality solar fuel with high efficiency and has a great potential in cost reduction.