Compressed Air Energy Storage for Offshore Wind Turbines

Integrating renewable energy sources, such as offshore wind turbines, into the electric grid is challenging due to the variations between demand and generation and the high cost of transmission cables for transmitting peak power levels. A solution to these issues is a novel highefficiency compressed air energy storage system (CAES), which differs in a transformative way from conventional CAES approaches as it employs nearisothermal compression/expansion and energy storage prior to conversion to electrical power. This approach utilizes seawater as a liquid piston for air compression. The liquid piston creates a positive gas seal, enables a high surface area compression space for increased heat transfer, and utilizes the ocean as a thermal source/sink. The compressed air is stored in an “open accumulator,” where the air volume is modified through displacement of a liquid. The ability to exchange energy in the open accumulator by addition or subtraction of the gas or the liquid provides system control advantages, including storage of high power transients and direct control of air pressure independent of the energy storage level. Following a presentation of the system, the authors present a sizing example and a discussion of future work required for realization of this promising technology.