A recent report published by the U.S. Energy Information Administration (EIA) on the status of utility-scale energy storage illustrates that battery storage is a proven technology for the shifting of electrical loads and improving grid stability. It also makes it clear that storage systems must continue to grow along with renewable energy projects in order to make the transition to clean power achievable.
Utility-scale battery storage is an essential enabler for the growth of reliable renewable energy systems. Without extensive energy storage capacity, fossil-fuel-fired plants will continue to be needed to supply power to the electrical grid when renewable energy is unavailable. Although dam controlled hydroelectric power and pumped hydroelectric power are deployed for peak power production, and pilot projects exist for flywheel storage, batteries are the technology widely recognized as the solution for “smoothing” the supply and demand curves on electrical grids.
According to the EIA report, as of December 2021, 4,605 megawatts (MW) of utility-scale battery storage capacity is deployed and operational in the United States. For comparison, most natural gas power plants in the U.S. are rated between 1,500 and 2,500 MWs of power.
The term “duration” is used as a measurement of the length of time a battery can deliver its rated power. Utility-scale batteries currently in use have a duration that averages approximately 3 hours, meaning that they can deliver full rated power for 3 hours. Of course, full power is not always required, so a portion of their rated power is available over a longer time period.
Utility-scale batteries are used for two general purposes. The first is grid service applications where batteries discharge power for very short periods of time to help stabilize the delivery of consistent power. The second application is load shifting where batteries allow some of the electrical supply to be shifted from off-peak to peak demand periods. Batteries used for load shifting are required to have longer durations than those used for grid service.
Historically, grid service has been the predominant use for battery storage. But, driven by the increasing deployment of renewable energy systems, the recent growth in utility-scale storage has been in systems that have the capability to perform both load shifting and grid service duties.