Short-term, long-term, energy storage methods for standby electric power systems

Reliability of electric power supply for all types of industrial, commercial, and institutional customers using computer and electronic loads requires energy-storage means and inverters to transition intervals of electric utility interruption. Requirements for energy storage are divided into short-term for systems with engine-generator or alternate feeder backup, and long-term for systems that await utility restoration, or are part of the utility system. Energy-storage methods are described and compared, including batteries, flywheels, SMES, compressed air, fuel cells, and ultra capacitors. Comparison charts for cost, reliability, and other factors, and references for additional information are included.