A system for capturing and converting and/or storing wind energy includes a vessel adapted to receive at least one wind machine for capturing wind and a device for converting wind energy to storable energy. A method of adapting a vessel, such as a surplus cargo ship or an oil tanker, for use as a offshore power generating system comprises equipping a vessel with devices for capturing a renewable energy source, positioning the vessel at sea to capture the renewable energy source, converting the renewable energy to a storable energy source, and storing the converted energy, and repositioning the vessel to capture further renewable energy or transport the stored, converted energy.