In recent years, severe haze has occurred in many parts of China. How to use clean energy to reduce environmental pollution is an important issue that China's economic development needs to face for a long time. The scale application of new energy and the large-scale access of intermittent renewable energy, the growth of traditional power peaks and valleys, various energy application problems will also emerge, and the application of energy storage technology will provide very effective solutions to these problems. way. At present, there are many power storage technologies, and the advantages of compressed air storage are obvious. In the future, it will undoubtedly become the largest potential energy storage in addition to pumped storage.

According to the technical classification, power storage can be divided into mechanical energy storage (pumped storage, compressed air energy storage, flywheel energy storage, etc.), electromagnetic energy storage (supercapacitors, etc.) and electrochemical energy storage (lead acid battery, lithium ion battery). , sodium-sulfur batteries, etc.) (see).

Among the various energy storage technologies, the pumped storage capacity is the largest in scale, reaching the upper GW, and the technology is also the most mature; the compressed air storage energy is second, the single machine scale can reach 1MW level; the chemical storage energy scale is small, and the single machine scale is generally The MW level is smaller or smaller, and the larger the scale, the more prominent the control problem. So far, large-scale energy storage technologies (such as above 1MW) that have been put into commercial use on a large scale have only two types of pumped storage and compressed air storage. The performance characteristics of pumped storage and compressed air energy storage suitable for large-scale energy storage are described in detail below.

Discharge time energy storage technology compressed air supercapacitor flywheel lead acid battery lithium ion battery sodium sulfur battery nickel cadmium battery nickel hydrogen battery pumped storage vanadium flow battery zinc bromide battery energy (MWl power storage technology overview 1.1 pumped storage pumped storage It is necessary to install two high and low reservoirs and install an electric water pump unit that can operate in both directions. It uses the potential energy conversion of electric energy and water to convert uncontrollable electric energy generated by renewable energy such as wind energy and solar energy into stable electric energy or cutting that can be accepted by the power grid. The purpose of Fengping Valley (see).

Pumped storage is one of the most mature and widely used energy storage technologies in power systems. As of 2011, China's total installed capacity of pumped storage capacity exceeds 18 million kW, and it plans to reach 30 million kW in 2015. Pumped storage capacity can be built into different capacities, and the energy release time can be from several hours to several days. The energy storage technology has high conversion efficiency and the comprehensive efficiency can reach 70%-85%. The disadvantage is that it is necessary to build two high and low reservoirs. It is very difficult to locate the site due to special site requirements, and the site is generally far away from the large-scale wind farm. With solar farms, the construction period is also long, and it will bring certain ecological and immigration problems.

Power Generation Compressed air energy storage is another power storage system that can realize large-capacity and long-term energy storage. It refers to the use of low-density, wind power, solar energy and other hard-to-storage power for compressed air, and the compressed high-pressure air is sealed. In a gas storage facility, an energy storage method that releases compressed air to promote turbine power generation when needed.

At present, the underground gas storage station adopts various modes such as abandoned mines, gas storage tanks settled on the seabed, caves, expired oil and gas wells and new gas storage wells. The most ideal one is the water seal constant pressure gas storage station, which can maintain the output constant pressure. gas. The above-ground gas storage station adopts a high-pressure gas storage tank mode.

Compressed air energy storage is a gas turbine based energy storage technology. The technology is very mature and has been applied to large-scale commercial applications. Compressed air energy storage has the advantages of large capacity, long working time, good economic performance, and many charge and discharge cycles. The details are as follows: (1) It is second only to pumped storage in scale, and is suitable for the construction of large power stations.

The compressed air energy storage system can work for several hours or even several days, and the working time is long; (2) the construction cost and operating cost are relatively low, lower than the sodium-sulfur battery or the flow battery, and lower than the pumped storage power station, which has a good economy. Sex.

As the application of thermal insulation materials uses only a small amount of fuel or a fuel such as natural gas or petroleum to heat compressed air, the cost of fuel is gradually reduced; (3) site restrictions are small. Although it is the most economical way to store compressed air in a suitable underground mine or cave under lava, the solution to modern compressed air storage is to replace the cave with a ground storage tank; (4) Long life, maintenance can be achieved 40 to 50 years, close to 50 years of pumping and storage. And its efficiency can reach about 60%, close to pumped storage power station; (5) high safety and reliability. The raw material used for compressed air storage is air, which will not burn, no danger of explosion, and will not produce any toxic or harmful gases. In the event of an air leak in the gas tank, the pressure inside the tank will suddenly drop and the air will neither explode nor burn.

In short, in some areas in China that do not have the natural conditions for constructing pumped storage power stations, especially large-scale wind farms and solar farms far from the consumption centers, there is an urgent need to research and develop another energy storage technology that can be used for a long time on a large scale. Due to the obvious advantages of compressed air storage, it can make up for the congenital shortage of pumped storage, and it will be an important choice to effectively solve the problem of large-scale energy storage in China.

2.1 Working principle Compressed air energy storage is an energy storage system based on gas turbine technology. The working principle is very similar.

The gas turbine unit consists of three main parts: the compressor, the burner (or combustion chamber) and the turbine (see). The working principle of the gas turbine is that the impeller type compressor absorbs air from the outside, is compressed and sent to the burner, and the fuel (gas or liquid fuel) is also injected into the combustion chamber to be mixed with the high-temperature compressed air, and is burned under constant pressure. The generated high-temperature and high-pressure flue gas enters the turbine expansion work, drives the power blade to rotate at a high speed, and drives the compressor to rotate the charge air. About 2/3 of the power in the gas turbine device is used to drive the compressor.

The main structure of a gas turbine Compressed air energy storage generally consists of five main components: compressor, combustion chamber and heat exchanger, turbine, gas storage device (underground or above ground cave or pressure vessel), motor/generator (see). The working principle is slightly different from that of a gas turbine: the compressor and the turbine do not work at the same time, and the motor and the generator share a machine. During energy storage, the electric 70 equipment in the compressed air energy storage consumes electric energy, drives the compressed air of the compressor and stores it in the gas storage device; during the process of venting power generation, the high-pressure air is released from the gas storage device and enters the gas turbine combustion chamber. After burning with the fuel, driving the turbine drives the generator to output electrical energy. Since the compressed air comes from the gas storage device, the turbine does not have to consume power to drive the compressor, and the turbine output is almost entirely used for power generation.

Compressor power clutch I turbine motor / generator half-air compressed air exhaust gas storage device burning half - compressed air energy storage basic principle 2.2 application status compressed air energy storage power generation has mature operating experience, the first commissioned unit It has been safely operated for more than 30 years. Two large-scale compressed air energy storage power plants have been put into commercial operation, located in Germany and the United States.

The first was the German Huntorf power station, which was put into commercial operation in 1978. It is still in operation and is the world's largest capacity compressed air storage power station. 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.Ixl05m3, and the compressed air pressure can reach up to 10MPa. The unit can be continuously inflated. 8li, continuous power generation 2li. The power station started a total of more than 5,000 times from 1979 to 1991, with an average starting reliability of 97.6%. The actual operating efficiency is about 42%. The second is the American Alabama, which was put into commercial operation in 1991. State's McIntosh compressed air energy storage power station (see). The power storage unit of the energy storage power station is 50MW, and the power generation capacity is 110MW. The gas storage cave is 450m underground, the total volume is 5.6xl05m3, and the compressed air storage pressure is 7.5MPa. It can realize continuous 41h air compression and 26h power generation. The full load takes about 9 minutes. The power station is controlled remotely by the energy control center of the Alabama State Power Company. The actual operating efficiency is about 54%. 2700MW large compressed air energy storage commercial power station, which consists of 9 300MW units. The compressed air is stored in a cavern of underground rock salt layer of 670m underground. The volume of the gas storage cave is 9.57xl06m3. 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 2MW. 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. The energy storage system has a power generation capacity of 422 MW, an air pressure of 3.3 MPa, and a system inflation time of 8 hours. The gas storage cave is a hard rock geology with a water seal. 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, mostly concentrated in the theory and small experimental level, and there is no commercial compressed air storage power station. The Institute of Engineering Thermophysics of the Chinese Academy of Sciences is constructing a 1.5MW advanced compressed air energy storage demonstration system.

According to the insulation method of compressed air energy storage, it can be divided into two types: non-adiabatic compressed air energy storage, and adiabatic compressed air energy storage. At the same time, according to the heat source of compressed air storage, non-adiabatic compressed air energy storage can be divided into non-adiabatic compressed air energy storage without heat source, non-adiabatic compressed air energy storage for burning fuel, and adiabatic compressed air energy storage can be divided into external heat source. Adiabatic compressed air storage with adiabatic compressed air storage and compression heat source (see).

Adiabatic compression of non-f-burning fuel without heat source: non-adiabatic compressed gas storage energy l air storage energy-free heat source combustion fuel storage heat storage compressed air energy storage classification 3.1 non-heat source non-adiabatic compressed air energy storage non-heat source compressed air storage The energy system does not use combustion fuel heating, nor does it use other external heat sources and insulation.

During energy storage, the motor drives the compressor to compress the air and store it in the gas storage device. During the venting power generation process, the high-pressure air is released from the gas storage device, and the turbine is driven to drive the generator to output electric energy (see).

The non-adiabatic compressed air energy storage without heat source has the advantages of simple structure, but low energy density and efficiency of the system. Therefore, it is only used in micro-miniature systems, used as backup power, air motor power and vehicle power, etc., and is not suitable for large-scale energy storage.

Non-adiabatic compressed air storage without heat source 3.2 Non-adiabatic compressed air storage for combustion fuel Non-adiabatic air compression storage for combustion fuel is characterized by the need to provide more additional fuel to the system, heating from the gas storage device during deflation Air flowing out.

Typical representatives are the Huntorf compressed air energy storage power station in Germany and the McIntosh compressed air energy storage power station in Alabama, USA. Compared with the basic principle of compressed air storage, the compression process and the expansion process are two-stage, the compression process includes inter-stage and post-stage cooling, and the expansion process includes an intermediate reheat structure.

See the Huntorf compressed air energy storage structure in Germany. During the energy storage process, the motor drives the compressor, and the air is compressed into high-pressure air through two stages. At the same time, the cooling device is used, cooled before entering the gas storage device, and then stored in the gas storage device. During the release process, the high-pressure air is released from the gas storage device, and the turbine is driven to output electric energy through two supplemental combustions.

See the structure of non-adiabatic compressed air for burning fuel (without heat recovery). It differs from Germany's Huntorf compressed air energy storage in that it is a compressed air energy storage system with a waste heat recovery device that preheats compressed air by recovering waste heat from the turbine exhaust, thereby increasing the thermal efficiency of the system. Due to the regenerative structure, the unit power generation fuel consumption of the McIntosh power station saves the non-adiabatic compressed air energy storage (with heat recovery) of the burning fuel compared to the Huntorf power station. 72 Equipment mechanical electric compressor clutch turbine motor/generator air cooling installation S Gas storage device burning semi-remaining heat exchanger exhaust gas electric compressor clutch turbine air motor / generator cooling installed 3 gas storage device compressor electric turbine clutch motor / generator air compressed air exhaust gas storage device with insulation non-adiabatic 3.3 outside Adiabatic Compressed Air Storage of Heat Sources This type of compressed air storage is heated by storing an external heat source instead of fuel. The external heat source may be waste heat and waste heat of solar thermal energy, electric power, chemical industry, cement and the like. At present, the most widely used is solar thermal energy. Solar thermal utilization is one of the most realistic, promising and most promising alternatives to the use of fossil energy. The solar collector can obtain high temperatures above 550 °C, but Due to the intermittent and unstable solar energy, heat storage devices have innate demand in solar thermal utilization systems.

In the energy storage process, the motor drives the compressor, and the compressed air is stored in the gas storage device, and the external heat energy is stored in the heat storage device. In the process of energy release, the stored external heat source heats the compressed air and drives the turbine to drive the generator output energy (see 0).

Compressor Power Turbine Clutches two p motor/generator air compressed air heat storage heat exchanger waste gas storage device external hot suburban temperature, increasing the requirements for compressor heat resistant materials. Although the system removes the combustion chamber, the addition of the heat storage device causes an increase in the number of pipes and valves and an excessive volume of the gas storage device.

Compressor Power Clutch Clutch Turbine Motor/Generator Air Heat Storage Heat Exchanger Exhaust Compressed Air Gas Storage Device 1 Compressed Heat Source with Adiabatic Compressed Air Energy Storage Traditional compressed air energy storage mainly generates electricity directly through the turbine.

In order to improve the flexibility of the system working mode, improve the efficiency of the system and adapt to special purposes, the application method of directly coupling the high-pressure air compressed by the compressed air energy storage with other thermal circulation systems has emerged.

0 Adiabatic compressed air storage with external heat source 3.4 Adiabatic compressed air storage for compressed heat source The compressed air process in compressed air storage system is close to the adiabatic process, producing a large amount of heat of compression. As in the ideal state, compressed air to 10 MPa can produce a high temperature of 650 °C.

In the energy storage process, the adiabatic compressed air storage energy of the compressed heat source stores the heat of compression in the air compression process in the heat storage device, and the high pressure air is stored in the gas storage device. In the process of energy release, the stored compressed heat is used to heat the compressed air and then drive the turbine to do work (see 1).

Compared with non-adiabatic compressed air energy storage, the overall efficiency can reach up to 70%. At the same time, the outlet of the compressor in this system will reach a high of 650 ° C. 4.1 Compressed air energy storage and renewable energy coupled system wind power and solar power output The uncertainty and volatility bring many problems to the real-time power balance and safe and stable operation of the grid. Compressed air energy storage enables stable output of intermittent renewable energy and provides an effective solution for large-scale utilization of renewable energy.

In the electricity valley, the excess electric power of the wind farm drives the compressor, compresses and stores the compressed air, and the solar heat energy is stored in the heat storage device.

In the process of energy release, the heat of the solar energy and the heat in the exhaust gas are used to heat the compressed air, and if necessary, the compressed air is further heated by the combustion, and then enters the turbine to generate electricity. This system can effectively solve the grid-connected problem of renewable energy and further increase the proportion of rest-type renewable energy supply in the grid (see 2).

Wind farm compressor clutch grid turbine motor/generator t. compressed air storage device fuel exhaust heat storage heat exchanger waste heat converter solar thermal energy 2 compressed air energy storage and renewable energy coupling system and other gas storage devices; At the peak of electricity, after the compressed air is heated by the exhaust gas of the gas turbine, it can be directly injected or mixed with the compressed air of the gas turbine to be injected into the combustion chamber to increase the work of the gas turbine, and the exhaust gas is still heated by the residual heat exchanger to compress the compressed air. air.

Compressor Turbine Power Compressor Waste Heat Fuel Converter Exhaust Compressed Air Storage Device 4.2 Compressed Air Energy Storage and Gas Turbine Coupling System Compressed air energy storage is similar to the structure and working principle of gas turbine, and can be combined into a highly efficient coupling system for efficient use. Compressed air storage serves the purpose of cutting peaks and valleys (see 3).

In order to improve energy efficiency, in general, high-power gas turbines need continuous high-load operation, while compressed air energy storage is used as a "force device" for gas turbine power generation. When electricity is used, the excess power is used to compress the air and store it in underground caves or on the ground. High-pressure vessels 3 Compressed air energy storage and gas turbine coupling system The current compressed air energy storage is still in the exploration stage in China, the technology is not yet mature, but the system scale Large and low energy storage costs, especially in the context of China's wind energy, solar energy and other renewable energy and consumer central areas, will be widely used in the future power system.

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