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Principles of Energy Storage Science and Technology Compressed Air Energy Storage Technology Chen Haisheng\Liu Jinchao U, Guo Huan U, Xu Yujie\Tan Chunqing1 (1 Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190; 2University of Chinese Academy of Sciences, Beijing 100190) Explain, including working principles, work processes, key technologies, development status, and application areas.
Energy storage stores energy (mainly electrical energy) through a certain medium, and releases the stored energy when needed to improve the efficiency, safety and economy of the energy system. Energy storage is one of the most important bottlenecks restricting the large-scale utilization of renewable energy. It is also a key technology to improve the efficiency, safety and economy of conventional power systems, as well as distributed energy systems and smart grids. It has become the current power and energy field. R&D and investment hotspots.
Compressed air energy storage (CAES) and pumped storage are recognized as energy storage systems that are suitable for large capacity and long term electrical energy storage. The compressed air energy storage system stores excess electric energy through compressed air, and releases high-pressure air through the expander to generate electricity when needed. Since StalLaval proposed the use of underground caverns to achieve compressed air energy storage in 1949, the first author and communication contact: Chen Haisheng (1977-), male, researcher, the main research direction is new large-scale power storage systems and materials, micro gas turbines, Small-scale flow and heat transfer, etc. E-mail: Domestic and foreign scholars have carried out a lot of research and practice work, and two large power plants have been put into commercial operation in Germany and the United States. In addition, Sakamoto, Italy, Israel and other countries have compressed air storage power stations in the process of construction. Although China's research and development of compressed air energy storage system started late, it has been highly valued by relevant research institutes, power companies and government departments. It is currently a research and development hotspot of large-scale energy storage technology.
This paper will briefly explain the technical principle and development status of compressed air energy storage.
1Technical principle Compressed air energy storage is an energy storage system based on gas turbine technology. For the working principle diagram of the gas turbine, after the air is compressed by the compressor, the fuel is heated and heated in the combustion chamber, and then the high temperature and high pressure gas enters the turbine to expand work. The compressor of a gas turbine consumes about 2/3 of the turbine output work, so the net output of the gas turbine is much smaller than the output of the turbine. Compressed air Chen Haisheng, etc.: Principle of compressed air energy storage technology Gas turbine system principle The compressor and turbine of the gas storage system do not work at the same time (and). When storing energy, the compressed air energy storage system consumes electric energy to compress and store the air. In the gas storage chamber, when the energy is released, the high-pressure air is released from the gas storage chamber, and the combustion chamber is heated by the fuel combustion to drive the turbine to generate electricity. Due to the energy storage and energy release time-sharing work, there is no output power consumed by the compressor in the process of releasing energy. Therefore, compared with the gas turbine system that consumes the same fuel, the compressed air energy storage system can generate twice as much. More electricity. Compressed air energy storage has the advantages of being suitable for large systems (above 100MW), unrestricted energy storage cycle, low system cost, long life, etc. However, there are problems such as dependence on large gas storage rooms and fossil fuels.
The working process of compressed air energy storage is similar to that of a gas turbine, as shown. Assuming that both the compression and expansion processes are single-stage processes, the working process of the compressed air energy storage system mainly includes the following four.
C1) Compression process 1 - 2 air is compressed by the compressor to a certain high pressure and stored in the gas storage chamber; ideally, the air compression process is adiabatic compression process 1 - 2, the actual process is 1 (2) heating process due to irreversible loss 2—3 High-pressure air is released through the gas storage chamber, and becomes high-temperature and high-pressure air after being burned with the fuel; in general, the process is an isobaric heat absorption process.
The expansion process is 3-4, and the actual process is 3-4' due to irreversible loss. (4) The cooling process is discharged into the atmosphere after being expanded by air, and then inhaled through the atmosphere during the next compression; this process is an isobaric cooling process.
The main difference between the compressed air energy storage system and the working process of the gas turbine system is as follows: (1) The above four processes of the gas turbine system are continuously performed, that is, four processes in (a) complete one circuit, and the compression process in the compressed air energy storage system is one to two. The heating and expansion process (2 - 3 - 4) is not continuous, the middle is the air storage process; 2 the gas turbine system does not have the air storage process, the storage process of the compressed air in the gas storage chamber is not shown in the figure, the general situation The temperature will decrease slightly during the lower compression storage process, but the volume remains the same, which is thermodynamically a constant volume cooling process.
Compressed air energy storage system working principle Energy storage science and technology Compressed air energy storage system is often used in multi-stage compression and interstage/stage post-cooling, multi-stage expansion and interstage/stage post-heating. As shown in (b). In (b), process 2'-1' and process 4'-3' represent the interstage cooling process between the interstage cooling and expansion processes, respectively.
2 key technology compressed air energy storage system generally includes six main components: 1 compressor, generally multi-stage compressor with intermediate cooling device; 2 expander, generally multi-stage turbo expander with inter-stage reheating equipment; Combustion chamber and heat exchanger for fuel combustion and recovery of waste heat; 4 gas storage devices, underground or above-ground caves or pressure vessels; 5 motor/generators, respectively connected to compressors and expanders through clutches; 6 control systems and Auxiliary equipment, including control systems, fuel tanks, mechanical transmission systems, piping and fittings.
Key technologies for compressed air energy storage systems include high efficiency compressor technology, expander (turbine) technology, combustion chamber technology, gas storage technology and system integration and control technology. Compressors and expanders are the core components of compressed air energy storage systems, and their performance has a decisive impact on the performance of the entire system. Although compressed air energy storage systems are similar to gas turbines, compressed air energy storage systems have much higher air pressures than gas turbines. Therefore, the compressors of large-scale compressed air energy storage power stations often adopt the axial flow and centrifugal compressor to form a multi-stage compression, interstage and post-stage cooling structure; the expander often adopts a multi-stage expansion plus intermediate reheat structure. The pressure of the high pressure combustion chamber of the compressed air energy storage system is relatively large compared to conventional gas turbines. Therefore, if the temperature is high during the combustion process, more pollutants may be generated, and thus the temperature of the high-pressure combustion chamber is generally controlled below 500 * C. Compressed air energy storage systems require large compressed air capacity, usually in underground salt mines, hard rock caves or porous caverns. For micro-miniature compressed air energy storage systems, high-pressure gas storage tanks can be used to get rid of gas storage caves. Dependence and so on.
3 Development Status At present, two large compressed air energy storage power stations have been put into commercial operation in the world. The first was the German Huntorf power station (), which was put into commercial operation in 1978 and is still in operation. The unit's compressor power is 60MW and the output energy is 290MW. The system stores compressed air in an abandoned 600m underground mine. The total volume of the mine is 3.1x105m3, and the compressed air pressure can be up to 1bar=105Pa. The unit can be continuously inflated for 8 hours and continuously generate electricity for 2 hours. The second is the McIntosh compressed air energy storage power station (Alabama State, USA) which was put into commercial operation in 1991. The underground gas storage cave is 450m underground, with a total volume of 5.6x105m3, and the compressed air storage pressure is 7.5MPa. The power storage unit has a power of 50MW and a power generation of 110MW, which can achieve continuous 41h air compression and 26h power generation. The power station is remotely controlled by the Energy Control Center of the Alabama State Power Company.
2700MW large compressed air energy storage commercial power station, which consists of 9 300MW units. The compressed air is stored in the underground rock salt cavern of 670m underground. The volume of the gas storage cave is 9.57x106m3. The Shangshachuanxing compressed air energy storage demonstration project put into operation in Japan in 2001 is located in Sokyo-gun, Hokkaido, with an output of 4MW. Development of intermediate units for industrial testing of 400 MW units. It uses abandoned coal mine pits (about 450m underground) as a gas storage cave with a maximum pressure of 8MPa. Swiss ABB (now integrated into Alstom) is developing a combined cycle compressed air energy storage system. At present, in addition to Germany, the United States, Japan, Switzerland, Russia, France, Italy, Luxembourg, South Africa, Israel and South Korea are also actively developing compressed air energy storage power stations.
China's research and development of compressed air energy storage systems began relatively late, but with the rapid increase in power storage requirements, related research has gradually been valued by some universities and research institutions. The Institute of Engineering Thermophysics of the Chinese Academy of Sciences, North China Electric Power University, Xi'an Jiaotong University, Huazhong University of Science and Technology and other units have studied the thermal performance, economic performance and commercial applications of compressed air energy storage power stations, but most of them focus on theory and small experimental level. At present, there is no commercial compressed air storage power station. Institute of Engineering Thermophysics, Chinese Academy of Sciences is carrying out 1.5MW advanced compressed air energy storage demonstration Chen Haisheng, etc.: Principles of compressed air energy storage technology Energy storage science and technology 4 Application areas CAES is initially used for peak shaving and frequency modulation, such as Germany The construction of the Huntorf power station and the McIntosh power station in the United States is used for peaking and frequency modulation. With the development of CAES technology and related technologies and the emergence of micro CAES (1050MW), CAES is becoming more and more widely used in renewable energy, distributed energy, and automobiles. UPS power supply and other aspects have been applied.
Chen Haisheng et al.: Principles of compressed air energy storage technology (1) The most important application of peaking large-scale CAES is power grid peaking and frequency modulation. CAES power stations used for peak shaving can be divided into two categories, independent CAES power stations in the power grid and Power station matching CAES system.
(2) Another important application of FM CAES is grid frequency modulation. CAES power station can be used for frequency modulation like other gas turbine power stations, pumped storage power stations and thermal power stations. Because it uses low trough power, it can be used as the first FM plant in the grid. When combined with other energy storage technologies such as supercapacitors and flywheel energy storage, the frequency modulation is faster.
(3) Renewable energy through CAES, it can store intermittent renewable energy and release it during peak hours, which will promote the large-scale utilization of renewable energy and provide peak power.
It mainly includes CAES combined with wind power, CAES combined with solar/photovoltaic, and CAES combined with biomass.
(4) Distributed energy system The combination of large power grid and distributed energy system is the development trend of efficient, low-carbon and high-security energy systems in the future. As a load balancing device and backup power supply, the energy storage system is the main way to solve the shortcomings of large fluctuations in the distributed energy system and high failure rate. CAES has a good application in distributed energy systems due to its advantages of easy integration with refrigeration/heating/cold cogeneration systems.
There are broad application prospects in other areas.
5 Development trend Compressed air energy storage is similar to pumped storage technology in terms of capacity, power level, discharge time, cost, etc., especially when large-scale (such as hundreds of megawatts) of energy storage is required and there is no condition for pumped storage. In this case, compressed air storage will have broad application prospects. In 2010, the famous American consulting company PikeResearch released their forecasts for compressed air storage in 2010-2020. Because compressed air storage is performed in three main parameters of large-scale energy storage technology: capacity or rated power (hundreds of megawatts), discharge time (number or tens of hours), and energy costs (hundreds of dollars / kWh) Excellent, PikeResearch estimates that the compressed air energy storage system market will increase from 453 MW in 2010 to nearly 7 GW in 2020. At the same time, we must also see the dependence of conventional compressed air storage on large gas storage, fossil fuels, etc. The problem must be applied to large-scale applications under the conditions of terrain and gas supply. The compressed air storage system (AA-CAES) with heat storage removes the combustion chamber and has the characteristics of high efficiency and pollution-free. It can be easily combined with solar thermal power generation system and is an important development direction of compressed air energy storage technology. . The Liquid Air Energy Storage System (LAES) and the Supercritical Air Energy Storage System (SCAES) store air in a liquid state, greatly reducing the volume of the gas storage chamber, thereby freeing the restrictions on large underground gas storage chambers, and also compressing air energy storage. An important development direction of technology. The compact compressed air energy storage system is simple in structure and flexible in function. It uses high-pressure vessels instead of gas storage caves to get rid of the dependence of traditional compressed air energy storage systems on terrain. It can be used for backup power, automobile power and distributed energy supply systems, and has broad application prospects. The coupling system of compressed air energy storage and renewable energy can solve the problem of discontinuity and instability of renewable energy. It is an urgent need to improve the large-scale utilization of renewable energy such as wind energy and solar energy. It will be the recent application of compressed air energy storage technology. The main development direction.
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