Abstract:

To investigate the performance variation of piston gravity energy storage systems (PGESSs) under different design parameters, a modular modeling approach was adopted to develop submodels for piston motion, confined pipe chamber pressure, and pump-turbine power. These submodels were used to simulate the dynamic motion and energy transfer characteristics of the PGESS. The charging and discharging processes were analyzed to derive expressions for total storage energy, charge-discharge efficiency, and energy density. The influence of key parameters namely, the height of the confined pipeline, the piston height, and the piston diameter was examined individually and in terms of their ratios. Results indicate that increasing the height of the confined pipe enhances both total storage energy and energy density; increasing piston height improves charge-discharge efficiency; and increasing piston diameter significantly boosts total storage energy. When the piston height-to-pipe height ratio increases, charge-discharge efficiency improves notably, while energy density and total storage energy initially rise and then decline. As the piston diameter-to-height ratio increases, both charge-discharge efficiency and energy density first increase and then stabilize. A similar trend is observed when both piston diameter and height increase. These findings provide a theoretical basis for optimal design parameter selection in PGESSs, supporting their further development and application.

Key words: gravity energy storage, modeling, performance analysis, charge-discharge efficiency, energy density