Cost analysis of two offshore hydro-pneumatic energy storage concepts

Abstract

The present paper compares two different concepts for implementing hydro-pneumatic energy storage at sea. Analytical models for the specific cost of both concepts in terms of Euro per kWh of storage capacity are derived based on the assumption that the thermodynamic processes of the compressed air storage systems are purely isothermal. These models are then used in an analysis to compare the specific cost of the two concepts taking into consideration different design parameters. The most influential parameters affecting the cost of both systems are highlighted. It is shown that the specific cost is very sensitive to the compressed air pressure ratio, reaching a minimum value for both concepts at around 2.5. It could be concluded that the first concept would be a cheaper option for intermediate depth waters while the second one would be a preferred option for very deep waters.