Exploring thermodynamic potential of multiple phase change thermal energy storage for adiabatic compressed air energy storage system

Adiabatic compressed air energy storage provides a promising solution for matching intermittent sources of renewable energy with customer demand during the daily cycle. In this work, a novel thermal energy storage strategy — using multiple phase change materials — are proposed to achieve less thermal energy loss in an adiabatic compressed air energy storage system, and the thermal energy storage performance of this type of thermal accumulators is discussed in detail by constructing the off-design thermodynamic mathematic model. The obtained results indicate that, compared with single-phase change material, a smaller amount of thermal energy loss appears while using multiple phase change materials stores compressed heat. Besides, in the initial cycles, there is still considerable residual heat remaining in the proposed thermal accumulator, however this will gradually fade away after 4 cycles, resulting in the thermal energy storage efficiency increases to 91.5%. It is confirmed that the round-trip efficiency increases by 4.7% if a thermal accumulator with multiple phase change materials was used for a conventional compressed air energy storage plant — Huntorf.