China has begun building the world’s largest compressed air energy storage facility in caves.

In China, the success of the first stage of a system to store excess renewable energy in compressed air in a cave inspired a 10-fold increase in the plant’s capacity. The Jintan project in Changzhou (Jiangsu province) will receive two 350-MW generators that can generate 2.8 GWh of electricity per year. The energy will be stored in a 1.2 million m² salt cave, making this project the world’s largest solution in this area

Image Source: CNSIG

The world’s first installation for storing excess energy in compressed air underground was created in Germany in 1978 (Huntorf power plant). It is capable of generating 290 MW for two hours daily. In 1991, a similar station was built in the USA – McIntosh Power Plant, its capacity is 110 MW. In China today there are nine to ten such plants with a total capacity of about 700 MW, where compressed air is mainly stored in containers.

The Jintan project, launched jointly with China National Salt Industry Group (CNSIG), Huaneng International Power Jiangsu Energy Development (a subsidiary of Huaneng Group, the main investor in the project), and scientists from Tsinghua University, is based on the use of a decommissioned salt mine. The first phase of the project included the commissioning of a 60 MW power generation plant. The successful implementation of the project confirmed its effectiveness, and now the site will be complemented by two turbines with a capacity of 350 MW each.

The system is designed for 330 charge and discharge cycles per year. During the day, it will accumulate excess solar energy by pumping air into the cave, and at night it will generate electricity using compressed air to rotate turbines. To increase efficiency, the air will be preheated. The energy for heating will be taken from the previous cycle: the heat generated when air is compressed by the compressor will be stored for use in the generation process.

These technologies made it possible to increase the efficiency of the installation to 60%. For comparison: the efficiency of a similar installation in the USA reaches 54%, and in Germany – 40%. After modernization, the automation system makes it possible to start energy generation in five minutes by pressing one button, whereas previously this required 20 minutes and sequential execution of operations by specially trained personnel.