Compressed-air energy storage

Compressed-air energy storage (CAES) is a way to store energy for later use using compressed air. At a utility scale, energy generated during periods of low demand can be released during peak load periods.^[1]

The first utility-scale CAES project was in the Huntorf power plant in Elsfleth, Germany, and is still operational^{[as of?]}.^[2] The Huntorf plant was initially developed as a load balancer for fossil-fuel-generated electricity, but the global shift towards renewable energy renewed interest in CAES systems,^[3] to help highly intermittent energy sources like photovoltaics and wind satisfy fluctuating electricity demands.^[3]

One ongoing challenge in large-scale design is the management of thermal energy, since the compression of air leads to an unwanted temperature increase that not only reduces operational efficiency but can also lead to damage. The main difference between various architectures lies in thermal engineering. On the other hand, small-scale systems have long been used for propulsion of mine locomotives. Contrasted with traditional batteries, systems can store energy for longer periods of time and have less upkeep.