Superconducting magnetic energy storage (SMES) system is one of the commonly used techniques by the end-users
to mitigate the voltage sag at their premises from the distribution system. The SMES is a superconductor
coil wound on a nonmagnetic core. The paper is aimed at optimizing the dimensions of the coil to achieve
minimum coil loss. The Genetic Algorithm (GA) is utilized to minimize the coil loss as a multi-objective function with indices including AC loss and refrigeration loss. The results show that the optimal total loss of SMES coil at capacity energy of 4 MJ is 85.04 W against 114.5 W in a previous work. The corresponding optimal dimensions of the coil which include the inner diameter, outer diameter and coil length are 0.19, 0.2 and 2.17 m, respectively. Different low-temperature superconductivity coil materials at operating temperature of 4.2 oK are considered to select the best material with minimum coil loss. The results conclude that Nb–Ti material achieves minimum coil loss when compared with MgB2 and YBCO. The effect of the twist pitch and circumferential stress on the total losses in the SMES coil is studied.