China Huaneng’s 700 MW Jintan salt-cavern compressed air energy storage (CAES) project has completed full-system startup of its two generating units in Changzhou, Jiangsu province.
The milestone was reached on Sept. 12, with both 350 MW units undergoing integrated startup testing under operating conditions. At 700 MW, the second phase of the Jintan project has the largest installed power capacity of any salt-cavern CAES facility currently reported worldwide. The project will now proceed with pre-grid-connection tests and system commissioning.
The plant uses four underground salt caverns at depths of around 1,000 meters, with total gas-storage volume of about 1.2 million cubic meters. Electricity is used to compress air to pressures exceeding 130 atmospheres during charging, while heat generated during compression is captured and stored. During discharge, the stored air is reheated and expanded through turbines without burning natural gas.
A full charging cycle stores about 2.8 GWh of electricity. Project documents describe an approximately eight-hour charging period and four hours of rated power generation, with more than 70% round-trip energy conversion efficiency. The facility is expected to complete around 330 charge-discharge cycles annually and generate about 924 GWh per year.
The second phase represents a major scale-up from the 60 MW/300 MWh first phase commissioned in 2022. Its compression system uses a dual-line, four-stage architecture to handle substantially higher airflow, while each generating unit employs a 350 MW air turbine with three reheating stages and four expansion stages. The turbine operates with a main air pressure of 13.5 MPa and has a design efficiency of more than 93%.
Thermal storage is another major change from the first phase. Jintan Phase II replaces the heat-transfer oil used previously with medium-temperature pressurized water. Sixteen spherical tanks, each holding 3,500 cubic meters, provide 56,000 cubic meters of thermal storage volume. Pressurization raises the water operating temperature to around 180 C, allowing compression heat to be recovered and reused during generation.
China Huaneng and China Salt Group jointly developed the project, with technical support from Tsinghua University and Xi’an Thermal Power Research Institute. Huaneng Jiangsu and China Salt’s salt-cavern business are responsible for project development, construction and operations. PowerChina subsidiary SEPCO1 has undertaken construction and installation work for Unit 2.
The Jintan design differs in several respects from Zhongchu Guoneng’s operating 300 MW/1,800 MWh Feicheng CAES plant in Shandong. Feicheng, based on technology developed by the Chinese Academy of Sciences’ Institute of Engineering Thermophysics, uses multi-stage wide-load compression, high-load turbine expansion and compact regenerative thermal-storage technology. It provides six hours of discharge and has a rated design efficiency of 72.1%. Jintan, by contrast, places greater emphasis on scaling individual turbine capacity to 350 MW, parallel four-stage compression and pressurized-water heat storage, while delivering four hours at rated output.
Both projects illustrate China’s shift from demonstration-scale CAES toward several-hundred-megawatt long-duration storage plants designed to provide peak shifting, renewable energy integration and other grid-balancing services.
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