Why would liquid air storage require no fossil fuel?

The interpretation of compressed air energy storage concept of Shuangliang Energy Saving(CAES) refers to the use of electrical energy for compressed air during the low valley of the grid load, and the sealing of air pressure in scrapped mines and subsidence. Submarine storage tanks, caves, expired oil and gas wells or new gas storage wells, Energy storage method for steam turbine power generation due to the release of compressed air during peak load of power grid. Since Stal Laval proposed the use of compressed air storage in 1949, scholars at home and abroad have conducted a lot of research. At present, there are two large traditional compressed air storage power stations in the world. In 1978, the first commercially operated compressed air storage unit was born in Hengtuofu, Germany. [ 1] In May 1991, the second power station was put into operation in Maijintuofu, Alabama, United States. At present, there are many forms of compressed air energy storage systems. According to the working medium, storage medium, and heat source, they can be divided into: traditional compressed air energy storage systems(requiring fossil fuel combustion), compressed air energy storage systems with heat storage devices, and liquid gas compression energy storage systems. system. The application prospect of compressed air energy storage is wider, such as it can greatly increase efficiency; Use more flexible, even can be used for car power; Embrace renewable energy, provide a share of renewable energy in the grid, and even take advantage of industrial heat. The main technical obstacles to the large-scale development of compressed air energy storage systems are twofold: the need for large gas storage devices and the reliance on burning fossil fuels. In order to solve these two problems, heat storage compressed air energy storage systems, micro-small compressed air energy storage systems, liquid air energy storage systems, supercritical compressed air energy storage systems, and compressed air energy storage systems coupled with renewable energy are used. Compressed air energy storage system with heat storage is also called advanced adiabatic compressed air energy storage system. The compression process of air in the system is close to the adiabatic process, and there is a lot of compression heat. For example, under ideal conditions, when compressed air is 100 bar, it can produce a high temperature of 650 °C. The compressed heat energy is stored in a heat storage device and heated to compress air during the energy release process to drive the turbine to do work. Compared with the traditional compressed air energy storage system that burns fuel, the energy storage efficiency of the system is greatly improved, and theoretically it can reach more than 70 %; At the same time, due to the use of compressed heat instead of fuel combustion, the combustion chamber was removed and the requirement of zero emission was achieved. The main disadvantage of the system is that initial investment costs will increase by 20 % to 30 %. The size of a small compressed air energy storage system is generally at the 10MW level. It uses above-ground high-pressure containers to store compressed air, thereby breaking through the dependence on gas storage caves and having greater flexibility. It is more suitable for urban energy supply systems-distributed energy supply, mini-grid, etc., for power demand side management, uninterruptible power supply, etc.; At the same time, it can also be built near renewable energy systems such as wind farms to regulate the supply of stable renewable energy power. The size of the miniature compressed air energy storage system is generally in the thousands of Watts to dozens of kilowatts. It also uses above-ground high-pressure containers to store compressed air. It is mainly used for backup power supplies in special areas(such as control, communications, and military fields), micro-mini-grids in remote and isolated areas, and compressed air vehicle power. Foreign scholars have developed a vehicle compressed aerodynamic system. The vehicle storage tank is 300 liters, 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. Liquid air and supercritical compressed air energy storage system is a new type of compressed air energy storage system. The former was jointly developed and developed by the Institute of Engineering Thermophysics of the Chinese Academy of Sciences and the British Gaozhan Company and obtained patents. Since the density of liquid air is much greater than the density of gaseous air, the system does not require large gas storage chambers. However, the system is less efficient. In order to solve the problem of inefficient liquid air energy storage systems, the Chinese Academy of Sciences Engineering Thermophysics first proposed and independently developed a supercritical compressed air energy storage system in 2009, which utilizes the special properties of air under supercritical conditions. The advantages of conventional compressed air energy storage system and liquid air energy storage system are combined. It has the advantages of large scale, high efficiency, low investment cost, high energy density, no need for large storage devices, unlimited energy storage cycle, application of various types of power stations, safety of operation and environmental friendliness. Compressed air energy storage and renewable energy coupling systems can "splice" intermittent renewable energy sources and steadily output. Compressed air energy storage systems with heat storage can store solar thermal energy, heat compressed air when needed, and then drive turbine power generation. In addition to solar thermal energy, waste heat from power, chemical, cement and other industries can be used as external heat sources. Therefore, the compressed air energy storage system with heat storage has a wide range of applications. In addition, it can also be coupled with wind power generation systems. At the bottom of the electricity consumption, the excess power of the wind power plant compresses and stores compressed air; At peak power, compressed air Burns and enters the gas turbine to generate electricity. A system coupled with compressed air energy storage and wind energy can increase the proportion of wind power supply in the grid to 80 %, which is much higher than the traditional maximum of 40 %. It can also use biomass as synthetic gas to replace natural gas in compressed air systems and reduce the dependence of compressed air energy storage systems on natural gas.

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