Study of a new receiver-reactor cavity system with multiple mobile redox units for solar thermochemical water splitting

Abstract

Solar thermochemical redox cycles could be a path to efficient, large-scale renewable hydrogen production. A new receiver-reactor concept is presented that combines characteristics of the most successful receiver-reactor systems to date, with features of concepts showing the highest efficiency potential. The key features of the system are movable reactive structures in combination with linear transportation systems and dedicated oxidation reactors. The application of several of these units allows the continuous operation of the receiver-reactor and permits the implementation of a solid–solid heat recovery system. Both of these characteristics are important to increase the system efficiency beyond the current state of technology. A numerical model is developed to simulate a basic cubic design version of the new concept and to analyse its performance. Parameter variations are studied amongst others for different cavity sizes, solar concentration factors and numbers of movable reactive structures. By avoiding the cyclic heating of the inert reactor vessel, the model predicts high efficiency values above 14% even for non-optimized designs. Furthermore, the basic concept of the heat recovery system is modelled with heat recovery rates of up to 20% in its most simple implementation. The new concept has the features required for highly performant systems and opens up a large parameter space for reactor design and operation optimization.