Power systems around the world are transitioning from fossil fuels to renewable energy sources, such as wind and photovoltaic (PV), increasing from 181.57 GW of worldwide installed capacity in 2009 to 549.24 GW in 2014 and generating 2.7 % of the electrical energy consumed globally. By 2050, wind power and PV are estimated to provide more than half of the electricity demand in China and more than 40% of the electricity demand in the U.S. But these statistics do not unveil the entire story. The enormous growth of variable renewable energy (VRE) like solar power results in a real-time imbalance between the energy consumed and produced . Due to integration of these VRE, intermittency and uncertainty of energy sources have been increased. In countries where electrical energy is traded in a competitive market, the intermittency and variability of renewable energy sources will also increase the volatility of electricity prices.
Energy storage systems are an essential enabling technology that allows the increasing integration of renewable resources into the electric power system. Energy storage systems can also be used to improve grid resiliency and reliability by distribution system operators. Energy storage systems will play an important role in residential and small commercial areas where pricing policy is dynamic. Electric customers can use storage systems in a strategic way to manage their energy use in new and profitable ways. Consumers can avoid paying high rates by storing energy during low-price off-peak periods and releasing that energy when the price is high.
The growth of distributed energy resources (DER) is changing the way electricity is delivered by the grid to end users. Distributed solar PV has evolved to become a valuable part of the global power generation mix and is forecast to grow substantially in the next several years as feed-in tariff and subsidy is provided by the government. In spite of an increase in the demands for distributed energy resources and storage, their development has been hindered due to following reasons: