Swept open moving particle reactor including heat recovery for solar thermochemical fuel production

Abstract

Green hydrogen can be produced by thermochemical redox cycles utilizing concentrated solar energy. A high solar-to-fuel efficiency, as well as a robust system design, is crucial. As lacking heat recovery and ineffective use of the redox material significantly reduce the efficiency, the authors developed a particle based concept incorporating these requirements. A central component is a solid–fluid direct contact heat exchanger in which the sweep gas reduces the countercurrent moving particles. Besides that, a key feature is the continuous production of hydrogen due to a locally separated reduction and oxidation step. The amount of technical challenging reactor parts is reduced, since the concept does not require a window and high temperature vacuum. A steady state modeling approach leads to an evaluation of the whole concept. The reduction reaction, a simplified oxidation process and several parasitic losses are included. By this means, the energy share and the solar-to-fuel efficiency is calculated. Depending on the heat exchanger effectiveness, the results indicate solar-to-fuel efficiencies in the range of 4.2 to 18.7% for the non-optimized base case design.