Xiao Ding, Wang Chengmin, Yi Tao, Xie Ning, Shi Weiwei (School of Electronic Information and Electrical Engineering, Shanghai Jiaotong University, Shanghai 200240, China) smallCAESJmicroCAES: Introduced a new type of large-scale energy storage technology - compressed air energy storage (CompressedAirEnergyStorage, CAE9, CAES The system has the fastest response, large capacity, low cost and long life, and has gradually become the second largest energy storage technology in the world.
According to the capacity of the CAES system, the CAES system is divided into three types: large CAES, small CAES and micro CAES. The composition and current status of the CAES are described in detail for three different capacity levels. The technical characteristics, difficulties and application areas are The scene was analyzed and outlined. The research direction and development prospect of CAES system are prospected.
With the development of China's economy, the demand for electricity is increasing, and the access of large-scale renewable energy puts forward new requirements for the planning, construction, dispatching and operation of the power system and the operation of the control mode. In the context of this fund project: National High Technology Research and Development Program (863 Program), the application of large-scale energy storage technology breaks the limitation of real-time balance of power supply and demand. Energy storage technology can generate electricity at peak load and store at low load. Electrical energy not only improves the flexibility of the system, but also effectively reduces the difference between day and night, and improves the stability, reliability and power quality of the grid. M. The combination of energy storage technology and renewable energy, significantly improving the utilization of renewable energy. At the same time, under the mechanism of time-of-use electricity prices, energy storage technology will also bring obvious economic benefits.
Different energy storage technologies have different characteristics and characteristics, making their application scenarios different. The existing energy storage technologies mainly include: battery energy storage, pumped storage, flywheel energy storage, CAES, and the like. Table 1 shows the performance comparison of various energy storage methods. Among them, the battery energy storage technology is simple and easy to grasp, but the life is short, it is not easy to recycle, and has a great impact on the environment; the pumped storage capacity is large, and can reach GW level. The operating cost is low, but the construction period is long, the initial investment is high, and the environment is greatly damaged. The flywheel energy storage construction period is short and the efficiency is high, but the investment is high, the continuous power supply capacity is weak, and the technology is not mature. CAES has low investment, low operation and maintenance costs, fast start-up, low environmental pollution, wide capacity range and rapid response. It can be applied to a variety of environments and is the second largest energy storage technology with the exception of pumped storage capacity. Bright prospects for development.
This paper mainly introduces the development and classification of CAES. It summarizes and summarizes the composition, technical characteristics, difficulties, application fields and scenarios of CAES systems with different capacities. The research direction and development prospects of CAES system are prospected.
In 1949, Germany first proposed the concept of CAES, which uses excess electric energy to drive compressor compressed air, convert electrical energy into mechanical energy, and finally convert it into internal energy storage of air. When needed, release the empty 76 Xiaoding, etc.: Compressed Air Storage (CAES) System Overview V1.30No.l Energy Conversion Efficiency / Storage Capacity / (MW-h) Response Time / Power / MW Battery Storage Pumped Storage The internal energy of the flywheel accumulating gas converts it into electrical energy and supplies power to the user.
Cheng, with a total capacity of 290 MW. In 1991, Alabama Electric Cooperative of the United States built the world's second CAES power station in McIntosh, Alabama, with a total capacity of 110 000 households for 26 hours of continuous power supply. In the construction of 35MW CAES power station, Israel A 100 MW CAES power station using aquifer caves is also being built. Other CAES power plants under planning or construction include: 25MW CAES power generation facilities for research on aquifer rock formations in Italy; 3x100MW CAES power generation facilities for hard rock aquifers in Israel.
The core technology of the CAES power station is the CAES system. So far, according to the technology used in the CAES system, the CAES system can be divided into three generations.
The first generation: compressed air and fuel mixed combustion, improve fuel combustion efficiency. The Htmtorf power station in Germany uses the first generation C AES system.
The second generation: Similar to the first generation CAES system, the technology has improved, the efficiency is higher, and the economic benefits are better. The McIntosh power station in the United States uses a second-generation CAES system.
The third generation: the compression or expansion process is adiabatic, the power generation process does not use fuel, no exhaust emissions. The CAES system stores heat during compressed air and heats the gas as it expands. The third generation CAES system is still in the research and development stage.
According to the storage capacity of the CAES system, the CAES system can be divided into three types of large CAES, with a single unit capacity of 100 MW; no small CAES, with a single unit capacity of 10 MW; multi-micro CAES, with a single unit capacity of 10 large CAES storage scales of 100 MW. It is commonly used in CAES power plants. The main components include compressors, expanders, combustion chambers, gas storage chambers, motor/generators, and control systems and auxiliary equipment. For the third generation of large CAES, the AA-CAES system, a heat storage device was used instead of the combustion chamber to avoid waste pollution. )compressor. The compressor is a core component of the CAES system and its performance has an impact on the energy storage efficiency of the CAES system. Although the compressed air storage cycle is similar to that of a gas turbine, the gas turbine compressor pressure ratio is generally less than 20, while the compressed air energy storage system has a compressor pressure ratio of 40 to 80 or even higher. Therefore, the compressors of large-scale CAES power stations use axial flow and centrifugal compressors to form multi-stage compression, interstage and post-stage cooling. M. Dynamic simulation of the vortex-based CAES system, simulation results show vortex The pressure difference between the compressor chambers is small, the leakage loss is small, and the overall efficiency is high, which is suitable for application in the CAES system.
The expansion machine M. Similar to the compressor, the expansion ratio of the compressed air energy storage system expander is also much higher than that of the conventional gas turbine turbine, so it is generally in the form of multi-stage expansion plus intermediate reheat. For example, the expander of the Huntorf power station consists of two stages, the first stage is expanded from 4.6 MPa to 1.1 MPa, and the second stage is fully expanded. Due to the high pressure, the first stage turbine cannot directly apply the ordinary gas turbine turbine, and the Htmtorf power station uses the modified steam turbine as the first stage turbine.
The multi-combustion chamber J enters the combustion chamber, combusts the fuel, generates steam and high-pressure air to enter the expander to perform work. The pressure and temperature inside the combustion chamber are large, and the pollutants generated by combustion will also increase. Therefore, the combustion temperature needs to be controlled during the combustion process, usually set at 500T: or less. The combustion chamber temperature before the first stage turbine of the Huntorf power station is 500T:.
4) Gas storage room. A cave or pressure vessel for storing high pressure air. In general, a 200MW CAES power station requires about 1Mm3 of storage space for storing high-pressure air. The storage chamber pressure of a large CAES system is usually 4.0~8.0MPaM. For example, the McIntosh power station pressure is 7.5MPa. Large-scale energy storage, usually using artificial excavation of salt-bearing rocks or hard rock formations, or naturally formed porous underground storage rock formations for storage of compressed air. Salt caverns, hard rock cavities and underground aquifers can be used as high-pressure storage CAES power stations can be divided into two phases: compressed phase and power generation phase.
In the compressed phase, the air in the atmosphere is sucked into the compressor for compression, and the obtained high-pressure air is stored in the air storage chamber. In the power generation phase, the compressed high-pressure air enters the combustion chamber from the gas storage chamber, mixes with the high-temperature and high-pressure gas generated by the combustion of the fuel, and enters the expander to drive the generator to generate electricity. The conversion efficiency of large CAES systems is around 75%, and the service life is above 30a. The construction cost of CAES mainly depends on the cost of the gas storage room, and the construction cost per kilowatt is usually 500 to 600 US dollars.
Gas storage, large capacity, low cost. The Htmtorf and Mclntosli power stations that have been put into operation use underground salt caves.
3 motor / generator. The motor is connected to the compressor and the generator is connected to the expander without special requirements.
6 control system and auxiliary equipment. Fuel tanks, piping and fittings ensure safe and efficient operation of the system.
Force heat storage. In terms of cost and efficiency, AA-CAES heat storage materials should have a large specific heat capacity, a wide temperature range, environmental friendliness, and easy access. Tl6 compares the heat storage properties of various materials, and Li-CaF2 is an ideal material for high temperature heat storage. The heat storage technology of AA-CAES is based on thermal storage technology. It needs to ensure good airtightness, small heat dissipation, and can adapt to the working range of turbomachinery. At the same time, the cost is suitable to use solid materials to store heat, and compare various schemes. The use of solid materials increases the contact area with the gas, reduces heat loss, and achieves heat storage. Tl9 uses water as a heat storage material to spray water vapor when compressing or expanding air, and achieves a large amount of energy storage in the case of increasing the contact area.
A schematic of the CAES power plant can be as shown.
To achieve high-pressure air storage, breaking through the location constraints of large CAES, the layout flexibility is stronger, and can adapt to various environments. In the range of output, small CAES combustion costs are lower in temperature and cost. The small CAES was evaluated in t24, which proved its feasibility and economy.
Small CAES can be used as an uninterruptible power supply or power demand side management, and can also be coupled with new energy sources. The role of small CAES system in demand side management of Korean power grid was studied, and the future application prospect of CAES system in Korea was prospected. P6-27 shows that the small CAES system can be combined with wind farms to improve the operation of wind farms and achieve good economic benefits. Modeling and simulating the application of small CAES system in photovoltaic cells, and indicating that the coupling method has a bright future.
The technical difficulty of small CAES is in gas storage tanks. Small CAES systems store air in a pressure vessel due to volume limitations, and at the same time, in order to increase the total amount of energy stored, the air is compressed to a greater pressure for storage. The t29 has designed a ground storage device that can withstand pressures above 8.3 MPa and can meet the requirements of small CAES systems for gas storage equipment. At present, the allowable pressure of high-pressure gas storage tanks on the market can reach more than 30 MPa.
Alliso's gas turbines for small CAES systems can provide 8~12MW of power. The pressure on the above-ground storage chamber is higher, about 10~14MPa, and the energy supply time is 3~5h. The investment cost of this small CAES power station is about 550/kW. Micro CAES has a storage scale of 10kW, similar to small CAES, with smaller capacity and size. Micro CAES is typically used in special areas such as control, communications, and military as a backup power source. Or for micro-miniature power grids in remote isolated areas, as well as compressed air vehicle power.
The static benefits such as energy conversion benefit were modeled and evaluated. Taking the distributed micro-system with installed capacity of 800kW as an example, the total static benefit was calculated to be 679.53 million yuan/a, and the static benefit was obvious.
The selection, thermal calculations and comprehensive benefits of the micro CAES system are described and evaluated in detail.
Small CAES has a storage scale of 10 MW and its composition is similar to that of large CAES. Small CAES utilizes high-pressure gas storage tanks on the ground At present, CAES has shown its bright prospects. In addition to its obvious advantages in static benefits such as capacity and clean energy efficiency, environmental protection benefits and energy conversion benefits, it also has FM efficiency and adjustment. Dynamic benefits of six aspects: phase benefit, fast load tracking benefit, rotating reserve benefit, improved power supply reliability benefit and black start benefit. CAES has a high comprehensive efficiency, a wide range of applications, and strong research.
In the future, the research of CAES system will focus on the following aspects. ) Modular research. The gas storage room of a large CAES system is generally a cave, which makes the location of CAES more demanding. Modular research splits the CAES system into small CAES systems, combined with distributed energy systems, which can be spliced ​​into CAES systems of various capacities as needed. Currently, there are CAES modules with a stand-alone capacity of 2MW.
Do not new H is the source of Artemisia. In the future, the CAES system will be combined with more new energy sources to improve the operation of new energy sources and ease the contradiction between new energy access and traditional power grids. The coupling of CAES systems with other energy systems will also become a research hotspot for CAES systems.
More combined heat and power. The combined cycle of CAES and other systems, as well as the combination of heat, electricity and cold, can greatly improve energy efficiency, which is the development trend of future research.
4) Heat storage. The heat storage of the AA-CAES system is very important. How to collect and store heat in an adiabatic environment is a major issue. At present, in the case where the adiabatic conditions reach the target, water can be a good heat storage medium in consideration of economy and practicability. The United States and Russia are conducting research in this area.
3 gas storage tanks. There are two kinds of storage methods: constant pressure and constant volume. The efficiency of the constant pressure gas storage tank is much higher than that of the constant pressure gas storage tank, but the storage volume of the constant pressure gas storage tank is larger than that of the constant pressure gas storage tank. Therefore, in the future, it is of great significance to overcome the technology of constant pressure gas storage tanks.
3 optimized cooperation. CAES system has many components and complex coordination. In the future work, the optimal cooperation of various components and the improvement of system efficiency are particularly important. In the new working mode design, it is more necessary to put the optimization cooperation in the first place.
1) The CAES system is characterized by its clean and efficient investment, long life and fast response. It can work with new energy sources such as solar energy and wind energy to improve the utilization rate and efficiency of renewable energy. It can also be integrated into microgrids and electric vehicles, resulting in obvious social, economic and environmental benefits.
The difficulty of the CAES system is the contradiction between the energy storage capacity and cost of the gas storage tank of the small and medium-sized CAES system, and the efficiency of different gas storage modes and operation modes.
Multi-CAES systems are becoming more modular, large-scale, efficient, and clean. With the continuous development and improvement of CAES system technology, CAES system will occupy a higher proportion in the future application of energy storage technology, becoming an economically viable Energy storage technology.
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