Innovative concept for thermochemical applications to store high temperature heat for later use
Concentrating solar power (CSP) technology is in principle compatible to thermal/thermochemical energy storage. Excess heat from the Sun is stored during the day to drive a power cycle during evening and night hours for prolonged electricity production. With this in mind, the EU-funded RESTRUCTURE (Redox materials-based structured reactors/heat exchangers for thermo-chemical heat storage systems in concentrated solar power plants) project worked to develop materials and novel reactor designs for the next generation of heat storage for CSP plants, based on thermochemical reduction-oxidation (redox) cycles. To achieve its objectives, the project exploited porous monolithic structures made entirely or partially from the redox materials instead of using packed or fluidised beds. This led to the scaled-up production of honeycomb cobalt oxide-based structures. These structures were used to build a pilot-scale structured reactor/heat exchanger that allows thermochemical storage (TCS) of solar heat based on the two-step cobalt/cobaltous oxide reversible redox cycle. Project partners installed the pilot at an existing solar tower facility in Germany (Solar Tower at Juelich). They successfully demonstrated the technology by determining repeatable and quantifiable heat storage/release capability over a broad range of energy discharge operation modes. It reached satisfactory energy storage density levels and storage capability and further future improvements were proposed. The system showed sufficient robustness and operational flexibility in the course of 28 total redox cycles. The RESTRUCTURE team used the pilot findings to validate a detailed numerical reactor model for designing a scaled-up redox TCS system, integrated into a future commercial high temperature CSP plant. The redox concept, along with monolithic honeycomb reactors/heat exchangers, will enable development of compact and flexible storage modules to facilitate better operating efficiency at a reduced cost. RESTRUCTURE laid the groundwork for further development and commercialisation of a novel and 100 % renewable technology for the CSP industry.
Keywords
Concentrating solar power, RESTRUCTURE, structured reactors, heat exchangers, thermochemical storage, redox
