Caes

CAES, or Compressed Air Energy Storage, is a method of storing energy by compressing air and keeping it under high pressure in underground caverns or other large containers. The stored air can be released later to generate electricity when demand rises or when intermittent energy sources, such as wind or solar, are supplying power.

In operation, excess electrical power drives a compressor to pressurize air, which is then stored in a suitable reservoir typically a salt cavern, depleted reservoir, or large tank. The compression raises the air’s temperature, and in conventional systems this heat is often captured and stored for later use. When electricity is needed, the compressed air is released, heated (by recovered heat or by burning a fuel to reheat the air), and expanded in a turbine to drive a generator. Heat recovery and staged processes influence overall efficiency and emissions.

CAES systems are categorized by how they handle heat. Conventional or diabatic CAES stores the compressed air with limited heat reuse, relying on external heat sources during power generation, which can limit efficiency. Adiabatic CAES designs aim to capture and store the compression heat so it can be returned to the air during expansion, reducing or eliminating the need for supplemental fuel. Advanced concepts also explore more complete thermal management, including near-isothermal approaches.

CAES is well suited to grid-scale, long-duration energy storage, providing services such as peak shaving, balancing, and renewable integration. Storage capacity can be large, and response times are suitable for rapid grid needs, though performance is site-dependent. Notable early commercial plants were built in Europe and North America, with ongoing development aimed at improving efficiency, cost, and environmental impact.