Development of an Efficient Compressor for Ocean Compressed Air Energy Storage

Utilization of intermittent ocean energy resources can be improved by integrating them with an energy storage system. Ocean compressed air energy storage (OCAES) is a promising large-scale energy storage system in the proximity of ocean energy resources. Efficient compressors and expanders are needed to achieve a high roundtrip efficiency of OCAES systems. In this paper, the development of an efficient liquid piston compressor is discussed. Heat transfer enhancement techniques such as aqueous foam and spray cooling are tested in a liquid piston compressor to achieve a highly efficient near-isothermal compression. It is observed that both aqueous foam and spray cooling are highly effective in abating the rise of air temperature during compression and improve the isothermal efficiency of compression. The use of aqueous foam in a liquid piston compressor shows an isothermal efficiency up to 91% whereas spray cooling results in an isothermal efficiency up to 96%. Efficiency analysis of liquid piston based OCAES systems with aqueous foam and spray cooling indicate the potential improvement of 4-14% in roundtrip efficiency of OCAES with the use of aqueous foam and 10-20% improvement with the spray cooling.