Enhanced Solar-to-Fuel Efficiency of Ceria-Based Thermochemical Cycles via Integrated Electrochemical Oxygen Pumping

Abstract

The solar thermochemical cycle based on ceria is a promising route for renewable fuel production. The solar-to-fuel efficiency of a thermochemical reactor is highly dependent on the oxygen removal during the reduction step. Conventional nitrogen sweeping (NS) requires high heating load and additional gas separation work, which limit the reactor efficiency. We propose the integration of a high-temperature electrochemical oxygen pump (EOP) for in situ oxygen removal to minimize the heating load and to allow for effective oxygen pumping. A transient model was developed to quantify the reactor performance using EOP or NS schemes. The model predicted that the ceria nonstoichiometric coefficient at the end of the reduction was enhanced by 56.8% when using the EOP scheme compared to the NS scheme. Correspondingly, the solar-to-fuel efficiency enhancement factor was 1.64 at reference conditions. In addition, the EOP scheme showed more uniform temperature and species concentration distributions, leading to a more favorable thermo-mechanical stability.

Solar-driven thermochemical conversion of H2O and CO2 into sustainable fuels

“…Similar with the last reactor design, Bai et al. 238 designed a novel solar thermochemical reactor integrated with electrochemical oxygen pump (EOP) which is employed for in situ oxygen removal with a low heating load. The design idea is shown in Figure 16 .…”

Recent Developments in Ceria-Driven Solar Thermochemical Water and Carbon Dioxide Splitting Redox Cycle

“…To improve the rate of CO production, which directly enhanced the solar-to-fuel energy conversion efficiency, Chen et al As the solar-to-fuel energy conversion efficiency heavily depends upon the TR of the metal oxide, Bai et al [103] examined the application of a high-temperature electrochemical O 2 pump (EOP) capable of supporting the O 2 removal during the TR of ceria-based redox thermochemical cycle. EOP was considered a replacement for inert gas sweeping as the later procedure requires extra heating and gas separation energy.…”