Feasibility Study on Large Scale SMES for Daily Load Leveling Using Force-Balanced Helical Coils

The authors examine the design options of a 360-MWh superconducting magnetic energy storage (SMES) for daily load leveling using YBCO coated conductors. The 360-MWh SMES is composed of 4000 superconducting coils with the force-balanced coil (FBC) helical windings. Because the FBC can significantly reduce the required mass of the structure, the induced electromagnetic forces are mainly supported by the tensile stress in the Hastelloy substrate of the YBCO conductors. By the effect of the FBC windings, 12 kJ/kg of the higher stored energy density per unit weight of the coil can be achieved. From the thyristor converter losses and the cooling power requirements, the energy cycle efficiency of the 360-MWh SMES is at least 70% with the cooling temperature of 20 K. Especially, if the cooling temperature is selected as 50 K, the energy cycle efficiency can be expected to be at least 79%. This efficiency is higher than that of pumped hydro storage. Therefore, large-scale SMES is one of the feasible options for daily load leveling by selecting an optimal cooling temperature.