Coupled effects of parameters on thermodynamic performance of a pumped hydro compressed air energy storage

The growing integration of renewable energy into power systems has heightened concerns regarding their intermittent nature and associated fluctuations. Pumped hydro compressed air energy storage represents an innovative energy storage technology designed to mitigate renewable energy variability. This research systematically examines the coupling effects of operational parameters on pumped hydro compressed air energy storage performance, with particular emphasis on six critical parameters. Quantitative results indicate that the round-trip efficiency reaches an optimum of approximately 36.0% under near-adiabatic or near-isothermal conditions with low compression-to-storage time ratios. Energy storage density demonstrates a positive correlation with heat transfer coefficients, exceeding 0.20 kW h/m3 under near-isothermal operations. The configuration of pressure parameters exerts a substantial influence; for instance, varying the preset and storage pressures shifts the round-trip efficiency significantly between 27.0% and 34.0%. Although the height-to-diameter ratio and water-to-air ratio indirectly affect system efficiency through their impact on heat transfer coefficients, their overall contribution remains relatively minor. Notably, the pump-turbine unit emerges as the primary source of energy loss (operating at approximately 60%-62% efficiency), whereas the accumulator maintains a remarkably high thermal efficiency ranging from 85.3% to 92.6%.