AC losses in the SMES conductor and coil structure

The authors present a methodology for calculating AC losses in the SMES/ETM (Superconducting Magnetic Energy Storage/Engineering Test Model) conductor and coil structure. Coupling and eddy current losses are discussed for a 100-s discharge of a 143-m-diameter ETM with a total stored energy of 21 MWh. The chosen pitch length, filament size, and winding configuration are shown to result in coupling losses that are small during this 400-MW. The total coupling losses are about 0.0048 J/cm³. The structural current losses result in energy deposition of about 0.05 J/cm³ during the same discharge. The energy is being deposited in the structure (away from the conductor) and over a very long time as far as stability is concerned (100/s). In addition, the highest power deposition occurs toward the end of the discharge, when the conductor current is lowest. The AC losses during slow utility discharge, calculated using the proposed methodology, represent part of the steady-state heat load to be removed by the refrigeration system