In analyzing energy storage processes, the defined area of objects or space used to determine the research object is called the energy storage system. It includes the input and output of energy and matter, energy conversion, and storage devices. Energy storage systems often involve multiple energy sources, devices, materials, and processes, making them complex energy systems that vary over time and require multiple indicators to describe their performance. Commonly used evaluation indicators include energy density, energy storage power, energy storage efficiency, energy storage price, and environmental impact.
Because the energy needed by people is highly time- and space-dependent, in order to rationally utilize energy and improve energy efficiency, a device is needed to collect and store excess energy that is temporarily not needed for a period of time, and then extract it for use during peak demand periods, or transport it to areas with energy shortages for later use. This method is called energy storage.
The basic task of an energy storage system is to overcome the temporal or localized differences between energy supply and demand. These differences arise in two situations: one is due to sudden changes in energy demand, i.e., peak load problems. Energy storage methods can play a regulating or buffering role when the rate of load change increases.