ABSTRACT
In any practical power system of high power rating, some form of large-scale energy storage is required for various purposes. On ships, this requirement is traditionally met by the electrochemical battery and compressed air. Regardless of how the energy is stored, the process of first storing and then using the stored energy will result in some losses both ways. The goodness of the energy storage device is best measured in terms of the round-trip energy efficiency, which can be taken as the figure of merit in comparing various alternative energy storage technologies. It is defined as
Round tripenergyefficiency= energydelivered toloadsduringdischarge
energyinjected torestoreinitial chargelevel (15.1)
Five alternatives for large-scale energy storage are discussed next: electrochemical battery, supercapacitor, rotating flywheel, superconducting coil, and compressed air.
