Thanks to technological advances, China is transforming abandoned underground salt caverns to renewable energy storage facilities amid its green push.

Underground salt caverns, with their natural advantages of large gas storage capacity, favourable sealing effect and high safety, can provide excellent conditions for compressed air energy storage.

Salt cavern compressed air energy storage technology uses electric energy to compress air into the huge cavity formed by salt mining during low electricity demand periods, and releases air to drive an air turbine to generate electricity when needed.

China completed its first salt cavern gas storage base in Jintan district, Changzhou city, Jiangsu province, in 2007.

In 2017, the Jintan Salt Cavern Compressed Air Energy Storage National Pilot Demonstration Project, the world's first non-supplemental combustion compressed air energy storage power plant, was approved by the National Energy Administration.

The project, jointly developed by China National Salt Industry Group, China Huaneng and Tsinghua University, has an installed power generation capacity of 60 MW and a storage capacity of 300 MWh in Phase I.

Aiming to set standards and provide solutions for energy storage in new-type electric power systems, the project's long-term target is to reach 1,000 MW, according to China National Salt Industry Group.

Situated at approximately 1,000 meters deep under the ground, the salt cavern has a storage room of 220,000 m³, equivalent to about 105 swimming pools.

In 2022, the plant was officially put into commercial operation, marking significant progress in the R&D and application of such an advanced technology.

Besides using the peak-to-valley difference to achieve peak regulation, it can also serve as a backup station for the power grid.

Of particular note is that the plant achieved a zero-carbon breakthrough in the commercial operation of compressed air energy storage technology, setting a benchmark for new energy storage.

In two years, the plant has cumulatively generated more than 86 million kWh electricity and completed peak shaving electricity of 250 million kWh.

It epitomizes the significant progress China has made in recent years in salt cavern compressed air energy storage.

In 2022, Sinopec put into use the country's deepest underground natural gas salt cavern storage well, running more than 2,000 meters deep.

Also in 2022, China's first 300 MW compressed air energy storage demonstration project was launched in Yingcheng city, Hubei province, and was successfully connected to the grid this April.

As the technology becomes more mature, the efficiency of salt cavern compressed air energy storage is expected to be further improved, injecting new momentum into its application and the sector's development.