Energy storage technologies for smoothing power fluctuations in marine current turbines

With regard to marine renewable energies, significant electrical power can be extracted from marine tidal current. However, the power harnessed by a marine current turbine varies due to the periodicity of the tidal phenomenon and could be highly fluctuant caused by swell effect. To improve the power quality and make the marine current generation system more reliable, energy storage systems will play a crucial role. In this paper, the power fluctuation phenomenon is described and the state of art of energy storage technologies is presented. Characteristics of various energy storage technologies are analyzed and compared for marine application. The comparison shows that high-energy batteries like sodium-sulphur battery and flow battery are favorable for smoothing the long-period power fluctuation due to the tide phenomenon while supercapacitors and flywheels are suitable for eliminating short-period power disturbances due to swell or turbulence phenomena. It means that hybrid storage technologies are needed for achieving optimal performance in marine current energy systems.