Solid-gas thermochemical energy storage strategies for concentrating solar power: Optimization and system analysis

A system-level analysis is presented for concentrating solar power systems employing various solid-gas thermochemical energy storage strategies, that is, different combinations of chemical reactions and process configurations. Specifically, three representative types (carbonate, hydroxide, redox) of reactions are studied and six different process configurations are proposed. An optimization model is then developed for the design and operation of the plants considering seasonal solar variability. The proposed model is used to obtain the optimal design and system performance of nine thermochemical energy storage strategies. Results show that six out of the nine strategies have the potential to improve both energy efficiency and economic performance over two-tank molten salt storage. In particular, the strategy based on manganese (III) oxide/trimanganese tetraoxide reaction and a configuration with indirect heat transfer in fluidized-bed reactor and open-loop structure achieves about 10% reduction in levelized cost of electricity over the commercially developed concentrated solar power plants. Finally, the impacts of key reaction and process parameters are analyzed and general guidelines for reaction and configuration selections are developed.