Tunisia Air Compressed Energy Storage Project

Among the different ES technologies, compressed air energy storage (CAES) can store tens to hundreds of MW of power capacity for long-term applications and utility-scale. The increasing need for large-scale ES has led to the rising interest and development of CAES projects.

Current long-term energy storage is mainly provided by Pumped-Storage Hydroelectricity (PSH). Compressed Air Energy Storage (CAES) has appeared for decades as a credible alternative but its poor energy efficiency, the need of fossil fuels and the use of existing underground cavities as storage reservoirs have limited its development.

2. Storage: The compressed air is stored, typically in large underground caverns such as salt domes, abandoned mines, or depleted natural gas reservoirs. Above-ground alternatives include high-pressure tanks or specially designed vessels, though these are generally more expensive and limited in capacity.

When charged using renewable energy sources, adiabatic CAES can be virtually emission-free. Unlike pumped hydro storage, which can require large reservoirs and potentially disrupt local ecosystems, CAES primarily uses underground geological formations, limiting surface land footprint.

CAES systems are categorized into large-scale compressed air ES systems and small-scale CAES. Large-scale systems are capable of producing >100 MW, while the small-scale systems only produce 10 MW or less . Moreover, the reservoirs for large-scale CAES are underground geological formations such as salt formations, host rocks and porous media.