China launches the world’s largest compressed-air energy storage facility in salt caverns

China Huaneng has announced the successful commissioning of the entire system at the Jintan project, a large-scale compressed-air energy storage facility. The 700 MW installation, located in Changzhou, Jiangsu province, consists of two 350 MW units and is currently the world’s largest facility of its kind using underground salt caverns. The project is now moving into the pre-grid-connection testing phase and final technical acceptance.

1.2 million m³ of underground space and 2.8 GWh of capacity

The storage facility uses four underground salt caverns located at a depth of around 1,000 metres, with a total gas storage volume of up to 1.2 million cubic metres. During the charging phase, electricity is used to compress air to a pressure exceeding 130 atmospheres, while the resulting heat is captured and stored. During discharge, the compressed air is reheated and directed to turbines without the need to burn natural gas.

A single full charging cycle can store around 2.8 GWh of energy. The facility has been designed for 8 hours of charging and 4 hours of operation at rated power, with a round-trip efficiency of more than 70%. According to the project assumptions, the facility is expected to complete around 330 cycles per year, generating approximately 924 GWh of electricity annually.

Pressurised water instead of oil

The second phase of the Jintan project represents a major leap compared with the first stage, commissioned in 2022, which had a capacity of 60 MW and an energy storage capacity of 300 MWh. The new facility introduces several significant design improvements:

• Innovative thermal energy storage system – medium-temperature pressurised water has been used instead of thermal oil. Heat is stored in 16 spherical tanks, each with a capacity of 3,500 m³, providing a total thermal storage volume of 56,000 m³. The elevated pressure allows the water to operate at a temperature of around 180°C.
• Powerful air turbines – each of the two generating units uses a 350 MW turbine with three reheating stages and four expansion stages. The turbine operates at a main air pressure of 13.5 MPa, achieving a designed efficiency of more than 93%.

China Huaneng and China Salt Group are jointly responsible for the development and implementation of the project, with technological support from Tsinghua University and the Xi’an Thermal Power Research Institute.