WindStore—Large-Scale Energy Storage Offshore

Abstract

Abstract WindStore is a research project focussed on Compressed Air Energy Storage (CAES) in the UK and Ireland, both onshore and offshore. CAES uses low-cost electricity at off-peak times or from renewable projects to compress air into a subsurface void or reservoir for storage. At peak times or when required, the compressed air and additional fuel drive a turbine to generate electricity. The two existing CAES projects in Germany and the USA are located onshore and use solution-mined salt cavities as storage reservoirs. Offshore the storage options include voids such as steel vessels and salt structures, and porous media such as saline aquifers and depleted gas reservoirs. There are two major applications for CAES offshore. (1) Small projects of some 10 MW capacity could be operated on platforms to store the variable output from nearby wind, wave or tidal current generators and make offshore installations more energy-independent. The fuel usage of CAES is significantly reduced compared to single cycle gas turbines. (2) Large offshore wind farms are planned, for instance, in the southern North Sea where depleted gas reservoirs exist. A large-scale CAES plant of several hundred megawatt capacity could be built on a disused platform using the depleted reservoir for air storage. This paper describes the applications and likely economics of small and large CAES plants located offshore with focus on the North Sea. It is outlined how CAES can allow a more economic use of high-voltage DC transmission links in future offshore networks.