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

Abstract

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 6.5MWhth 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 7.2GWhth capacity, for a 26MWel round-the-clock concentrated solar power plant during multiple 8h-charging/16h-discharging cycles, yielding 95% overall thermal efficiency.