Research status and development trend of compressed air energy storage in abandoned coal mines

Compressed air energy storage (CAES) has the advantages of low construction cost, small equipment footprint, long storage cycle and environmental protection. Exploring the development of CAES technology in underground space is one of the innovative approaches to achieve China’s “dual-carbon” goal. Underground energy storage reservoirs can be classified into salt caverns, aquifers, depleted oil and gas fields, abandoned coal mines, and caverns. With the increasing number of abandoned coal mines in China, the direct closure of resource-depleted coal mines not only cause a significant waste of underground space resources, but also induce a series of safety, environmental and other issues. Therefore, utilizing the underground space of abandoned coal mines as CAES reservoirs holds great application prospects. The analysis shows that, ① There is a large amount of usable space in abandoned coal mines, and eight reuse modes of underground space in abandoned coal mines have been summarized: agricultural and forestry land, construction land, site greening, watershed utilization, water-heat combination, wetland park, mine park, and space reuse. ② The research on CAES in abandoned coal mines in China started late, the basic theoretical research is weak, the key technologies is immature, and geological conditions in coal mines are complex, the relevant applications of basic research is insufficient, and the commercialization, large-scale promotion and application have not yet been achieved. ③ Three key technologies are summarized and proposed to cope with the CAES in abandoned coal mines, i.e., the evaluation method of site selection for the construction of abandoned coal mine energy storage reservoirs, the key technology for the sealing of abandoned coal mine energy storage reservoirs, and the stability and safety evaluation of abandoned coal mine energy storage reservoirs. A flowchart for siting the construction of CAES reservoirs in abandoned coal mines has been established.