Packed-bed thermal storage for concentrated solar power – Pilot-scale demonstration and industrial-scale design

A thermal energy storage system, consisting of a packed bed of rocks as storing material and air as high-temperature heat transfer fluid, is analyzed for concentrated solar power (CSP) applications. A 6.5 MWhth pilot-scale thermal storage unit immersed in the ground and of truncated conical shape is fabricated and experimentally demonstrated to generate thermoclines. A dynamic numerical heat transfer model is formulated for separate fluid and solid phases and variable thermo-physical properties in the range of 20–650 °C, and validated with experimental results. The validated model is further applied to design and simulate an array of two industrial-scale thermal storage units, each of 7.2 GWhth capacity, for a 26 MWel round-the-clock concentrated solar power plant during multiple 8 h-charging/16 h-discharging cycles, yielding 95% overall thermal efficiency.

► A 6.5 MWhth packed bed of rocks experimentally demonstrated for sensible heat storage.
► High-temperature air, heated by concentrated solar energy, is the heat transfer fluid.
► A dynamic numerical model is developed and validated with experiments.
► The model considers variable fluid and solid thermo-physical properties.
► Scale-up simulations for a 26 MWel power plant yields 95% overall thermal efficiency.