Experimental investigation on thermodynamic and energy performance improvement of variable‑speed pumped hydro compressed air storage system

This study proposes a synergistic enhancement strategy that integrates built-in metal tube bundles with the coordinated regulation of operating modes and valve openings to improve the thermodynamic and energy performance of water-air co-container tanks. Through comparative experiments under single-tank, dual-tank, and multiple valve-opening conditions, the synergistic enhancement of this structure, combined with valve control, on the thermodynamic and energy characteristics was systematically analyzed. Experiments demonstrated that metal tube bundles could significantly suppress air temperature fluctuations in the tank, reducing the temperature amplitude by 26.9% in single-tank operation mode. In the dual-tank configuration, temperature variations in both tanks diminished by over 10%, indicating a progression towards isothermal behavior. Compared to Case C80, Case C40 saw reductions in air temperature rise of 21.7% and 21.6% in Tanks 1 and 2, respectively, and in pressure loss of 53.3% and 48.8%. In Case C40, the round-trip efficiency of the tanks reached 0.838, an increase of 16.2% over Case 1. This study provides a highly adaptable and easily controlled thermal management solution for water-air co-container tanks.