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.The first utility scale CAES project has been built in Huntorf, Germany, being still operational. While the Huntorf CAES plant was initially developed as a load balancer for fossil fuel-generated electricity, the global shift towards renewable energy has led to a renewed interest in CAES systems, to help highly intermittent energy sources like photovoltaics and wind satisfy fluctuating electricity demands.One ongoing challenge in large scale CAES 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 CAES architectures lies in thermal engineering. On the other hand, small-scale systems have long been used as propulsion of mine locomotives. Compared to traditional batteries, CAES systems can store energy for longer periods of time and have less upkeep.