Wind-Powered Offshore Charging Station With Integrated Liquid Carbon Dioxide Energy Storage for Green Electrification of Maritime Vessels

This study proposes a renewable-powered offshore fast-charging station for electric vessels. It enables charging operations independent of onshore port infrastructure. The system is powered by 20 offshore wind turbines, each with a rotor diameter of 120 m, operating 12 h/day at a mean wind speed of 8 m/s. Surplus wind energy is stored in a liquid carbon dioxide (CO₂) energy storage system. CO₂ is compressed to high pressures, condensed into a dense-phase liquid at ambient temperature, and stored in high-pressure tanks. During periods of low wind availability, the stored liquid CO₂ is vaporized, superheated using recovered heat from compressors, and expanded through turboexpanders to regenerate electricity. The station features a 10 MW fast charger capable of fully charging an electric vessel with a 4 MWh battery capacity within an hour. A comprehensive thermodynamic analysis conducted in this study demonstrates that the offshore wind turbines operate with an aerodynamic-to-electric energy conversion efficiency of 36.15% while the liquid CO₂ energy storage system achieves a roundtrip energy efficiency of 70.14%. Further, the power electronics and delivery system of the fast-charging unit exhibit an electrical efficiency of 95% and the overall system efficiency considering wind turbines, CO₂ energy storage, and charger is 24.09%.