The investigation of the possibility of low-cost SMES is an indispensable theme if that practical use is to be realized. We optimized the system composition by selecting the most suitable charge/discharge rate. We conducted the optimum design on the structure of superconductor and the coil system under special consideration of the material unit price, the total material amount, the manufacturing efficiency, and so on. The pool-cooling double-row solenoid system using NbTi base conductor is the most suitable one as 15kWh-100MW SMES for the system-stabilizing use and 500kWh-100MW SMES for the load-fluctuation-compensating and frequency-controlling use.
