A novel compressed air energy storage system for wind turbine is proposed. It captures excess power prior to electricity generation so that electrical components can be downsized for demand instead of supply. Energy is stored in a high pressure dual chamber liquid-compressed air storage vessel. It takes advantage of the power density of hydraulics and the energy density of pneumatics in the “open accumulator” architecture. A liquid piston air compressor/expander is utilized to achieve near-isothermal compression/expansion for efficient operation. A dynamic system model as well as control laws for optimizing the turbine power, delivering required electrical power and maintaining system pressure are developed. A set of simulation case studies demonstrate the operation of the system.