Demonstration of a Solar Reactor for Carbon Dioxide Splitting via the Isothermal Ceria Redox Cycle and Practical Implications

Abstract

The performance of a 4.4 kW solar receiver/reactor to split carbon dioxide via the isothermal cerium dioxide thermochemical redox cycle is characterized during steady-state operation in a high-flux solar simulator. The solar reactor is the first to implement the isothermal redox cycle. Design innovations for continuous fuel production and gas-phase heat recuperation distinguish it from prior works. During steady-periodic operation at 1750 K, 360 mL min–1 of CO is produced continuously over 45 redox cycles, and up to 95% of the sensible heat of the process gases is recovered. The solar-to-fuel efficiency is 1.64% without consideration of the energy costs of producing nitrogen used as a sweep gas during reduction. With inclusion of the solar energy required to produce N2 via cryogenic separation, the efficiency is 0.72%. On the basis of the thermodynamic limitations of the cycle and the limited opportunity for increasing reactor efficiency beyond 2%, we conclude that the isothermal approach to split CO2 or ...