The world's largest salt-cavern compressed air energy storage project completed full-unit start-up tests on Saturday in Jintan, east China's Jiangsu Province, marking a major breakthrough in key technologies and system integration for large-scale compressed air energy storage in China.

The project has two generating units, with the start-up tests fully verifying the stability of the equipment and systems.

At the heart of the project is a large underground salt cavern used to store compressed air, together with a thermal storage system featuring 16 spherical water tanks. Each tank can hold 3,500 cubic meters of water, giving the system a total capacity of 56,000 cubic meters, equivalent to the volume of about 22 standard swimming pools. It is currently Asia's largest single thermal water storage tank array for a compressed air energy storage project.

The tanks store the heat generated when air is compressed. When electricity is needed, the stored heat is released to heat the compressed air, which is then used to drive turbines and generate electricity.

The salt cavern is formed naturally through underground salt mining. Freshwater is injected into salt deposits to dissolve the salt, with the resulting brine pumped to the surface. Over time, this process creates large underground cavities. Because salt has excellent airtightness, these caverns can safely store high-pressure air with minimal leakage.

The system stores energy when electricity demand is low. Surplus electricity powers compressors, which compress air to more than 130 times atmospheric pressure and inject it into the underground cavern. At peak demand, the compressed air is released to drive the generators.

Unlike conventional fossil-fuel-based power generation, the process requires no fuel combustion, allowing the system to provide large-scale, low-carbon energy storage for the power grid, effectively serving as a giant "power bank" for electricity.