The compressed air energy storage project, tested in Germany in the 1970s, has been given a second chance in the era of renewable energy sources. Their intermittent nature of generation requires storage capacity so that the supply of electricity is not interrupted at night and in calm weather. In China, the idea of pumping air into underground caves and then using the compressed gas to generate energy is actively being adopted. However, natural caves are running out, but the demand for them remains.
The lack of caves for storing energy in the form of compressed air has forced the Chinese to drill artificial underground reservoirs, and this requires the development of a whole range of technologies to ensure the reliability of the cyclopean underground structures and prevent leaks. In addition, conditions can be created underground to store air at higher pressures than in natural caves.
This marks the start of the first large-scale compressed air energy storage (CAES) project using a fully artificial underground cave, a major step towards commercializing the technology.
The project is being developed by a state-owned consortium and implemented with the support of local state-owned enterprise Xinyang Construction Investment Group, CAES technology specialist China Energy Storage National Engineering Research Center (China Energy Storage), and two other state-owned investment companies.
The complex is planned to be put into operation in 2026. It will have a capacity of 300 MW and will store 1,200 MWh of energy. The project is estimated at 2.15 billion yuan ($300 million). The underground work includes opening and equipping a cave with a diameter of 15 meters and a length of 1,800 meters. This is a capacity of 318 thousand m³. In a compressed state, much more air will be retained. The declared operating pressure of the artificial cave will be at the level of 14 MPa, which will allow pumping more than 50 million m³ atmosphere into it
To maintain the air underground under pressure and without leaks, technologies have been developed to strengthen the structure, concrete lining and sealed steel layer. As of December 2024, about 400 meters of the transport tunnel have been built, which is almost 80% of the planned volume of work. Excavation work is also already underway at the storage facility.
After commissioning, the electricity conversion efficiency is expected to be 72.1%, and the capacity to be 420 million kWh per year, which is enough to supply electricity to 350,000 households. The system includes multi-stage compressors that can withstand high turbine loads and advanced heat exchangers. The latter made it possible to abandon the use of fossil fuels for air heating, removing heat through the recovery process, which will make the project environmentally friendly. The success of the event will pave the way for the construction of similar facilities everywhere.