Compressed air energy storage (CAES) refers to the energy storage mode that electric energy is used for compressed air during the low load period of power grid, and air is sealed at high pressure in abandoned mines, sunken submarine gasholders, caves, expired oil and gas wells or newly built gas storage wells, and compressed air is released during the peak load period of power grid to promote turbine power generation.
Since 1949 StalLaval proposed to use compressed air to store energy, scholars at home and abroad have done a lot of research. At present, two large-scale traditional compressed air energy storage power stations have been put into operation in the world. 1978, the first commercial compressed air energy storage device was born in Hentoff. [1]1991May, the second power station was put into operation in McIntosh, Alabama, USA.
At present, there are various forms of compressed air energy storage system, which can be divided into traditional compressed air energy storage system (which needs fossil fuel combustion), compressed air energy storage system with heat storage device and liquid-gas compressed energy storage system according to working medium, storage medium and heat source.
The application prospect of compressed air energy storage is broader, such as greatly improving efficiency; It is more flexible to use and can even be used for automobile power; Accept renewable energy, provide the proportion of renewable energy in the power grid, and even use industrial waste heat.
The main technical obstacles to the large-scale development of compressed air energy storage system are two aspects: the demand for large gas storage devices and the dependence on burning fossil fuels. In order to solve these two problems, regenerative compressed air energy storage system, miniature compressed air energy storage system, liquefied air energy storage system, supercritical compressed air energy storage system and compressed air energy storage system coupled with renewable energy came into being.
Compressed air energy storage system with heat storage is also called advanced adiabatic compressed air energy storage system. The air compression process in the system is close to adiabatic process, and there is a lot of compression heat. For example, in an ideal state, when the compressed air is 100bar, a high temperature of 650°C can be generated. The compressed heat energy is stored in the heat storage device, and the compressed air is heated in the process of energy release to drive the turbine to do work. Compared with the traditional compressed air energy storage system burning fuel, the energy storage efficiency of the system is greatly improved, which can reach more than 70% in theory. At the same time, due to the use of compression heat instead of fuel combustion, the system cancels the combustion chamber and realizes the requirement of zero emission. The main disadvantage of the system is that the initial investment cost will increase by 20%~30%.
The scale of small compressed air energy storage system is generally 10MW. It uses high-pressure containers on the ground to store compressed air, thus breaking through the dependence on gas storage caves and having greater flexibility. It is more suitable for urban energy supply system-distributed energy supply, small power grid and so on. Used for power demand side management, uninterrupted power supply, etc. At the same time, it can also be built near renewable energy systems such as wind farms to adjust and stabilize the supply of renewable energy and electricity.
The scale of miniature compressed air energy storage system is generally in the order of several kilowatts to dozens of kilowatts. It also uses high-pressure containers on the ground to store compressed air, which is mainly used for standby power supply in special fields (such as control, communication and military fields), micro-power grids in remote and isolated areas, and compressed air car power supply. Foreign scholars have developed a vehicle compressed air power system, a 300-liter air storage tank, which can drive a 1 ton car to travel 96 kilometers at a speed of 50 kilometers per hour, basically meeting the needs of daily urban traffic.
Liquefied air and supercritical compressed air energy storage systems are newly proposed compressed air energy storage systems. The former was jointly developed and patented by Institute of Engineering Thermophysics, Chinese Academy of Sciences and Gao Zhan Company, UK. Because the density of liquid air is much higher than that of gaseous air, the system does not need a large air storage room. However, the efficiency of this system is low. In order to solve the problem of low efficiency of liquid-air energy storage system, the Institute of Engineering Thermophysics of Chinese Academy of Sciences first proposed and independently developed the supercritical compressed air energy storage system in the world in 2009. This technology takes advantage of the special properties of air in supercritical state and integrates the advantages of conventional compressed air energy storage system and liquefied air energy storage system. It has the advantages of large energy storage scale, high efficiency, low investment cost, high energy density, no need for large energy storage devices, unlimited energy storage period, suitability for various types of power stations, safe operation and environmental protection, etc., and has broad prospects.
The coupling system of compressed air energy storage and renewable energy can "splice" intermittent renewable energy and stabilize the output. The compressed air energy storage system with heat storage can store solar energy, heat the compressed air when necessary, and then drive the turbine to generate electricity. In addition to solar energy, waste heat from electric power, chemical industry, cement and other industries can be used as external heat sources. Therefore, the compressed air energy storage system with heat storage has broad application prospects. In addition, it can also be coupled with a wind power generation system. When the power consumption is low, the residual power of the wind power station compresses and stores compressed air; At the peak of electricity consumption, compressed air burns into the gas turbine to generate electricity. Using compressed air energy storage-wind energy coupling system can increase the power supply ratio of wind power to 80%, which is much higher than the traditional upper limit of 40%. Biomass can also be gasified into synthetic gas to replace natural gas in compressed air system, so as to reduce the dependence of compressed air energy storage system on natural gas.