Fast Energy Storage Systems Comparison in Terms of Energy Efficiency for a Specific Application

One of the key parameters to properly and accurately assess an energy storage system is the energy efficiency, which has a direct impact on the system performance and an indirect impact in its cost. In this paper, a methodology for comparing double-layer capacitors (EDLC) and kinetic energy storage systems (KESS) in terms of energy efficiency is proposed. This methodology, based on accurate loss models, takes real operating cycles into account, so a realistic result is obtained for each particular case. An accurate study of the losses of both technologies is accomplished during the paper, getting a complete model for EDLCs and KESSs, and obtaining efficiency maps for the whole range of operation points. Some conclusions about the convenience to use one or the other alternative and the best way to operate them are presented. In addition, a specific study case related to a wave energy power generation plant has been carried out in this paper, defining a methodology to select the energy storage requirements, calculating the round-trip efficiency and getting some recommendations related to the most appropriate operation strategy to take the most advantage of the energy storage system.