ABSTRACT
Resources and the environment are the decisive factor for the sustainable development of the human society. The demand for global energy is climbing rapidly due to population growth and continuing industrialization. The use of renewable energy resources, such as solar and wind, as an energy policy is being planned in larger numbers than ever before owing to concern over the energy crisis that is caused by the increasing international oil price and the exhaustion of the limited supply of fossil fuels.1-5 These sources are, however, intermittent and often unpredictable. In this regard, as a possible route to solving the energy crisis, the development of large-scale energy-storage systems in combination with renewable resources has attracted much attention in recent years. The usage of stored energy is fundamental to the generation of electric power, whether in fuel stockpiles for fossil or nuclear power plants or the seasonal runoff and dammed waterways for hydroelectric power plants. The use of energy-storage technologies provides many advantages to electric power transmission systems, such as effective use of existing plant investment, flexibility in operation, and better response to price changes.6 Storage could be used to defer or eliminate the need for high-cost investments in new or upgraded transmission and distribution facilities (wires, transformers, capacitors or capacitor banks, and substations). In addition, storage could also be a cost-effective option for utilities to improve power quality or service reliability for customers with high-value processes or critical operations.7 Other
benefits of energy-storage systems are use of off-peak power for pumping and/or charging and maximization of operations and flexibility for commercial buying or selling electricity during on-peak or off-peak periods.6 Finally, broad technical, economic, and social factors also suggest a promising future for energy-storage technologies.
