End-to-end efficiency of liquid piston based ocean compressed air energy storage

Abstract

Intermittent ocean energy resources need energy storage system for their optimal utilization. Ocean compressed air energy storage (OCAES) is a promising way for a utility scale energy storage. In this paper, a liquid piston based ocean compressed air energy storage is analyzed for end-to-end efficiency. An analytical model for end-to-end efficiency based on efficiencies of individual components in the liquid piston based OCAES is presented. Numerical analysis based on the analytical model and experimental data is done using Monte Carlo simulations. End-To-End efficiency of the liquid piston based OCAES is observed to be highly dependent on the polytropic index of compression and expansion. End-to-End efficiency increases from 24% to 72% with decrease in polytropic index from 1.4 to 1. Experimentally observed polytropic index shows 45% end-to-end efficiency. Comparison of results with end-to-end efficiency of existing compressed air energy storage systems indicates that the isothermal liquid piston based OCAES shows significantly higher end-to-end efficiency.