Types of Energy Storage  

Part 1

Batteries

There are various forms of batteries, including: lithium-ion, flow, lead acid, sodium, and others designed to meet specific power and duration requirements.

Initially used for consumer products, lithium-ion batteries now have a range of applications including smaller residential systems and larger systems that can store multiple megawatt hours (MWh) and can support the entire electric grid. These systems typically house a large number of batteries together on a rack, combined with monitoring and management units. These systems have a small footprint for the amount of energy they store. For example, a system the size of a small refrigerator could power an average home for several days. A utility-scale system of 100 MWh could fit on less than 0.5 acres.

Lithium-ion batteries have received a lot of press for their rapidly declining costs, due to the growing popularity of electric vehicles.

A different type of battery is a flow battery in which energy is stored and provided by two chemicals that are dissolved in liquids and stored in tanks. These are well suited for longer duration storage.

Thermal

Thermal systems use heating and cooling methods to store and release energy. For example, molten salt stores solar-generated heat for use when there is no sunlight. Ice storage in buildings reduces the need to run compressors while still providing air conditioning over a period of several hours. Other systems use chilled water and dispatchable hot water heaters. In all cases, excess energy charges the storage system (heat the molten salts, freeze the water, etc.) and is later released as needed.