Heat recovery concept for thermochemical processes using a solid heat transfer medium

The solar to fuel efficiency of a thermochemical water or carbon dioxide splitting process based on redox reactions with metal oxides and driven by concentrated solar energy highly depends on the heat recovery of sensible heat from the redox material. Today, no system exists that recovers heat between two redox particles streams at a temperature of about 1400 degrees C without the risk of an undesired reoxidation of the particles. Furthermore, a counter-current principle is essential to reach satisfactorily high heat recovery rates. In this work, we introduce a new concept utilizing a solid heat transfer medium in the form of spheres for heat recovery from particles. The mixing of redox particle and heat transfer spheres leads to a high surface area and enables an improved heat transfer. An appropriate connection of multiple heat transfer stages allows a quasi-counter-current heat transfer principle. A performance model of the system determines the heat recovery rate to be reached by the system. (C) 2014 Elsevier Ltd. All rights reserved.