An energy storage system (ESS) is pretty much what its name implies—a system that stores energy for later use. ESSs are available in a variety of forms and sizes. For example, many utility companies use pumped-storage hydropower (PSH) to store energy. With these systems, excess available energy is used to pump water into a reservoir during times of low demand. When energy demands rise, the water is discharged from the reservoir and drives a turbine which produces electricity.
PSH systems, though an efficient method of storing energy, are logistically complex and infrastructure intensive. Therefore, they typically are only used in utility-grade installations. While PSH currently commands a 95% share of energy storage, utility companies are increasingly investing in battery energy storage systems (BESS).
These battery energy storage systems usually incorporate large-scale lithium-ion battery installations to store energy for short periods. The systems are brought online during periods of low energy production and/or high demand. Their purpose is to increase the reliability of the grid and reduce the need for other drastic measures, such as rolling blackouts.
BESSs for both commercial and residential applications represent a small—but rapidly growing—sector of the ESS community. Increasingly, homes and businesses that use renewable energy generators (e.g., solar panels and wind turbines) are also including a lithium-ion BESS in their installation. This allows the storage of power during times of excess energy production and is a better value than selling the power to the grid and then buying it back at a higher price. It also functions as a backup during instances of power outages.
