ABSTRACT
Energy storage is classified as primary or secondary. When energy is extracted from a primary source, the source is used up and cannot be reused. By contrast, secondary methods allow many cycles of storing and withdrawing energy. Most methods do not store electric energy but convert it to some other form for storage. Energy storage systems can be large or small. Large systems are useful to the rate payer for load leveling and consuming electricity at favorable rates. On a national scale, large energy storage systems are needed to accept renewable energy when available and supply it when needed. Smaller storage systems are useful for protecting equipment from anomalies on the electric grid.
