Thermal Energy Storage for Concentrated Solar Power - State of the Art and Current Developments

Abstract

The integration of thermal energy storage systems enables CSP-plants to provide dispatchable electricity. The adaptation of storage systems both to the solar energy receiver system and the power cycle of the plant are essential for the effective utilization of storage capacity for CSP applications. Three different physical processes can be applied for energy storage: sensible heat storage in solid or liquid media, latent heat storage using phase change material and thermochemical energy storage. Different technical concepts have been developed for the implementation of the different processes, showing different states of maturity. Today's commercial CSP plants apply sensible heat energy storage using either molten salt or pressurized water as storage media. Two tank molten salt technology has reached thermal capacities in the GWh-range and temperatures up to 565 °C. The feasibility of solid media sensible heat energy storage has been proven by using concrete. For CSP-systems using air as heat transfer medium, packed bed storage units using solid storage media represent an attractive solution, allowing operation up to 800 °C. Latent heat storage concepts are preferred for applications using steam as working fluid, since here heat transfer processes occur within a narrow temperature interval. Thermochemical energy storage concepts are in an earlier state of development, various concepts are investigated. The presentation gives an overview of the various concepts developed for thermal energy storage in CSP plants and describes the state of the art and the recent advancements.