Abstract
Long-duration, grid-scale energy storage technologies provide a potential pathway to enable full penetration of renewables on the electricity grid and still maintain grid reliability and security. Among these technologies, pumped thermal energy storage (PTES), which stores energy thermally using a heat pump and discharges the stored thermal energy with a heat engine when needed, is an advantageous solution with high round trip efficiency, no geographical constraints, and modularity for various use cases. To support the technology development, a first-of-a-kind small scale demonstration facility of an air-based PTES has been designed, built, and tested with the objective of better understanding controls strategies and overall system operation. The PTES demonstration facility operates simple-recuperated cycles for charge and discharge mode with separate drivetrains for each mode and shared heat exchangers and storage systems. At a discharge mode rating of 5kW, this facility storages heat in a thermal oil up to 350 °C and cold in a water-glycol mixture down to −10 °C. In this paper, full system performance characterization is described with steady state and transient data from both charge and discharge modes during start-up, shut down, steady state, and system balance. Time series temperature data comparisons of a cold and warm startups are compared. These data highlight the importance of transient control tuning, the influence of ambient effects, and challenges associate with first implementation of a technology, particularly heat loss. This study documents the first of a kind operation of a full air-based PTES system.
