that the LTSC torus maximum diameter is always smaller for a HTSC magnet than LTSC due to higher magnetic field operation. In the case of solenoid coils, the height or length is also smaller for HTSC coils, but still much higher than in a toroidal geometry (due to low external magnetic field). An increase in peak magnetic field yields a reduction in both volume (higher energy density) and cost (reduced conductor length). Smaller volume means higher energy density and cost is reduced due to the decrease of the conductor length. There is an optimum value of the peak magnetic field, about 7 T in this case. If the field is increased past the optimum, further volume reductions are possible with minimal increase in cost. The limit to which the field can be increased is usually not economic but physical and it relates to the impossibility of bringing the inner legs of the toroid any closer together and still leave room for the bucking cylinder. The superconductor material is a key issue for SMES. Superconductor development efforts focus on increasing Jc and strain range and on reducing the wire manufacturing cost. Applications The energy density, efficiency and the high discharge rate make SMES useful systems to incorporate into modern energy grids and green energy initiatives. The SMES system's uses can be categorized into three categories: power supply systems, control systems and emergency/contingency systems. FACTS FACTS (flexible AC transmission system) devices are static devices which can be installed in electricity grids. These devices are used to enhance the controllability and power transfer capability of an electric power grid. The application of SMES in FACTS devices was the first application of SMES systems. The first realization of SMES using FACTS devices were installed by the Bonneville power authority in 1980. This system utilizes SMES systems to damp the low frequencies, which contributes to the stabilization of the power grid. In 2000, SMES based FACTS systems were introduced at key points in the northern Winston power grid to enhance the stability of the grid. Load leveling The use of electric power requires a stable energy supply that delivers a constant power. This stability is dependent on the amount of power used and the amount of power created. The power usage varies throughout the day, and also varies during the seasons. SMES systems can be used to store energy when the generated power is higher