Abandoned salt caverns transform into air power banks, providing new ideas for energy storage
Time:2023-09-26
Views:660
The seven things that people do when they open the door are firewood, rice, oil, salt, soy sauce, vinegar, and tea. The importance of salt is evident. Recently, due to the impact of the Fukushima nuclear accident in Japan, people have paid more attention to salt. In fact, the proportion of sea salt consumption in China is not large, and rock salt resources are more worthy of attention. According to data, the rock salt reserves in Ye County, Henan Province alone reach 330 billion tons, which can provide food for the entire country for 33000 years. However, the value of rock salt goes far beyond that. The salt caves left after the salt mines are also a huge green wealth.
Salt caverns are abandoned mines after salt mining, usually located nearly one kilometer underground, with a volume of up to hundreds of thousands of cubic meters. The walls of the caverns are sturdy and can withstand high pressures. Even if cracks occur in the cavity, the natural mineral salt melts and solidifies after encountering water, and the cracks will quickly heal themselves, making the salt cavity have good sealing and self-healing properties. In the past, after salt mines were mined out, the conventional treatment method was to inject water and seal the old wells to prevent accidents such as ground collapse, which failed to achieve comprehensive utilization.
Under the "dual carbon" goal, the rapid growth of new energy installation has significantly increased the demand for energy storage. Among them, compressed air energy storage is a relatively mature technology. The principle of this‘ air power bank ‘is not complex,When there is excess electricity, compressing and storing air into a sufficiently large chamber can convert electrical energy into compressed air potential energy. When electricity is needed, high-pressure air is heated and enters the expander to become atmospheric air. During this process, the generator is driven to generate electricity, and the compressed potential energy of the air can be converted into electrical energy output.
The power cost, capacity cost, and system comprehensive conversion efficiency of compressed air energy storage are comparable to pumped storage.However, the location of compressed air energy storage is more flexible than that of pumped storage, with a construction period much lower than that of pumped storage, and there are no issues such as immigration and ecological impact.Compared with electrochemical energy storage, compressed air energy storage has a lower cost per unit capacity and does not face issues such as resource development bottlenecks, upper limit of cycle life, safety and environmental risks. Large scale compressed air energy storage technology is an effective means to achieve peak shaving and valley filling in the power grid, solve the problem of new energy integration and consumption, and is an important supplement to a diversified energy storage system.
The power cost, capacity cost, and system comprehensive conversion efficiency of compressed air energy storage are comparable to pumped storage.However, the location of compressed air energy storage is more flexible than that of pumped storage, with a construction period much lower than that of pumped storage, and there are no issues such as immigration and ecological impact.Compared with electrochemical energy storage, compressed air energy storage has a lower cost per unit capacity and does not face issues such as resource development bottlenecks, upper limit of cycle life, safety and environmental risks. Large scale compressed air energy storage technology is an effective means to achieve peak shaving and valley filling in the power grid, solve the problem of new energy integration and consumption, and is an important supplement to a diversified energy storage system.
Salt caverns have become the preferred storage chamber for compressed air due to the aforementioned natural advantages.Salt cavern gas storage has the advantages of low construction cost, small footprint, short construction period, mature technology, good sealing performance, long system life, safety and stability, etc. It can meet the gas storage technology requirements of large-scale advanced adiabatic compressed air energy storage.With the construction and operation of demonstration projects such as Feicheng in Tai‘an, Shandong and Jintan compressed air energy storage power station in Changzhou, Jiangsu, abandoned salt caves have become rare treasures. According to statistics, the underground salt mine reserves in China exceed one trillion tons, and salt cave resources are mainly distributed in areas rich in new energy resources or densely loaded areas such as northwest, north, and east China. At present, most of these salt caves are idle, and if effectively utilized, they will become a viable force in building a new type of power system.
In order to promote the development of compressed air energy storage, in March 2022, the National Development and Reform Commission and the National Energy Administration issued the "Implementation Plan for New Energy Storage Development during the 14th Five Year Plan", listing the 100 megawatt level compressed air energy storage technology as one of the key directions for tackling new energy storage core technology equipment during the 14th Five Year Plan period.Under favorable policies, more and more enterprises are entering compressed air energy storage projects. As of the end of 2022, excluding projects that have already been put into operation, the scale of registered projects far exceeds the scale of projects that have already been put into operation. Participating enterprises include China Energy Engineering Corporation, China State Energy Storage Corporation, China Electric Power Construction Corporation, China National Energy Corporation, China National Power Investment Corporation, China Huaneng, etc. Among them, China Energy Construction Corporation plans to install hundreds of compressed air energy storage power stations in multiple regions such as Hubei, Shandong, Liaoning, Gansu, Qinghai, and has a long-term plan of over a thousand. Some institutions predict that compressed air energy storage is expected to form a market scale of hundreds of billions of yuan.
At present, there are still many problems with compressed air energy storage, the most important of which is geographical constraints. The construction of compressed air systems requires special geographical conditions for use as large gas storage chambers, such as salt caverns, high airtightness rock caverns, abandoned mines, etc. However, the geological structure of salt caves is unique and only exists in a few areas. The abandoned or natural underground salt cave resources suitable for compressed air energy storage are limited, making it difficult to meet the actual needs of site selection; Ground high-pressure storage tanks will occupy the ground area and are expensive. These limitations have become important factors affecting the promotion of compressed air energy storage.
Promoting the maturity of artificial chamber gas storage technology will greatly expand the market space for compressed air energy storage.The compressed air energy storage project based on artificial chamber gas storage can break away from the dependence on salt caverns in site selection, and also has advantages such as higher pressure upper limit, wider range of fluctuation utilization, higher system conversion efficiency, shallower burial depth, and easy maintenance. It is conducive to combining China‘s energy endowment and effectively linking large-scale energy storage with wind and solar resources. In December 2022, two 300 MW compressed air energy storage power station demonstration projects, Chaoyang, Liaoning and Jiuquan, Gansu, began construction, solving the global problem of compressed air energy storage constrained by geographical conditions. They have significant demonstration significance in promoting the scale of compressed air energy storage and efficient utilization of underground space.
Economy is the foundation for the commercial development of compressed air energy storage. At present, there is a lack of clearer policy support and relevant standard systems in the research and development and application demonstration of energy storage technology equipment, power market construction, and energy storage pricing mechanism, which restricts the large-scale development and construction of compressed air energy storage in China. In the absence of clear electricity pricing policies for compressed air energy storage power stations, a two part electricity pricing system similar to that for pumped storage power stations can be pursued to achieve profitability through capacity and electricity pricing.
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