Research on working characteristics of compressed air energy storage system

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Research on the working characteristics of compressed air energy storage system Yang Qichao, Liu Guangbin, Zhao Yuanyang, Li Liansheng (Hefei General Machinery Research Institute, National Compressor Technology. Compressed air energy storage system is to convert the low-cost electric energy of the power station during peak load to peak load High-priced electric energy, that is, when the system is at a low point, the surplus power in the power grid is used to store energy through the air compressor; in the peak load of the power system, the high-pressure air stored by the compressed air is supplied to the system through the expander to increase the system load rate. To solve the system peak-to-valley difference, it can also be used as a backup power source.

Combustion, burning in the same way as conventional gas turbines. Large compressed air energy storage systems primarily utilize specific underground mines or caverns to store compressed air. A small compressed air energy storage system can store compressed air using a high pressure gas storage tank or pipe network. There are two ways to design the gas storage device: constant volume and constant pressure. Usually, the energy storage system works under constant volume conditions, and the high pressure gas is reduced to a constant pressure through the throttle valve to ensure the relatively stable and efficient operation of the expander, and the pressure in the gas tank changes within a certain range. Commercially operated compressed air energy storage power stations are used in this way. For example, the pressure of the Huntorf power station in Germany is reduced to 4. 6 MPa, and the pressure in the gas storage space is varied from 4.8 to 6.6 MPa. The constant pressure type gas storage device can maintain the high efficiency operation of the power station and reduce the storage volume. At this time, the gas storage tank supplies the high pressure gas under the gas storage pressure to the expander, that is, the pressure of the gas storage tank is constant. 15 introduces the typical design scheme of constant pressure gas storage system. This paper will compare and analyze the system working characteristics of these two gas storage modes.

3 Thermal process analysis assumes that the air is an ideal gas, the ideal gas state equation: Rg - the gas constant T of the air - the temperature is shown as a schematic diagram of the theoretical cycle of the compressed air energy storage system. In the figure, 1-3 is an ideal isothermal compression process, 1-2 is an adiabatic compression process, and 3-4 is an adiabatic expansion process. The shadow area of ​​1-2-3-4 is the energy loss of the cycle process when the expander has no inlet force.

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P——Gas storage pressure Vs—Gas tank volume Rs—Air gas constant Ts—Storage gas temperature 3.3 Expansion process Multi-stage expansion intermediate heating can increase the output power of the expander. The output power of the expander in different working processes can be expressed as follows: the output power of the isothermal expansion is: the output power of the adiabatic expansion is: the relationship between the output power of the expander and the initial temperature of the expansion is shown, and it can be seen that whether it is isothermal expansion The process is also an adiabatic isentropic expansion process. The effect of the initial expansion temperature on the output power of the expander is linear, that is, increasing the initial temperature of expansion will greatly increase the function of the expander. Moreover, the closer the expansion process is to the isothermal process, the more the expansion output power increases with the increase of the intake air temperature. Thus, in many improved compressed air energy storage systems, heat of compression, solar energy, expander heat or fuel combustion may be utilized to preheat the expander inlet gas temperature to increase output work.

Gas storage pressure (MPa) The storage capacity of the energy storage system at constant pressure and constant pressure is shown as the ratio of the effective energy loss due to the pressure drop through the throttle valve to the stored high energy air energy. Under a certain throttle reduction ratio, the effective energy loss in the throttling process decreases with the increase of the gas storage pressure, and the change trend gradually becomes slower. The proportion of effective energy loss during throttling increases with the increase of throttling ratio. Combined and integrated, it can be seen that when the throttling depressurization is relatively large, although the effective energy loss of the throttling process is greater than the inlet air temperature of the expander (K), the influence of the intake air temperature on the output power of the expander. For the variation curve of the energy storage efficiency of the compressed air energy storage system under different working processes, the system does not adopt the inlet air preheating. It can be seen from the figure that the isothermal working process is an ideal working process, and its energy storage efficiency is 100%. The energy storage system of the adiabatic process is the least efficient. The multi-stage process in the middle refers to the expansion process of compression over-temperature and 2-stage expansion intermediate heating using 4-stage compression intermediate cooling. The energy storage efficiency is between the isothermal process and the adiabatic process, reflecting the achievable in practical applications. The working cycle (s/3fi platinum è…± constant capacity mode of throttling effective energy loss is the ratio of the ratio of the gas storage volume required by the constant volume system to the required gas storage volume of the constant pressure system as a function of the gas storage pressure. When the gas storage pressure rises, the ratio gradually decreases. For example, when the gas storage pressure is 9 MPa and the throttling pressure reduction ratio is 1.5 and 2.5, respectively, the volume of the gas storage tank of the constant volume system is constant pressure type. The system storage tank volume is 3.3, .4 and 2.1 times. Therefore, the constant pressure type compressed air energy storage system requires the smallest tank volume, and the design and manufacture of a constant pressure type gas storage system improves the compressed air energy storage system. The overall performance is important.

Large, but at this time, the mass of gas released from the gas storage tank for expansion work is also increased, thus causing a large energy storage density. The magnitude of the energy storage density is determined by the combined effect of the throttling ratio and the air quality.

Gas storage pressure (MPa) constant volume and volume ratio of gas storage tank under constant pressure 5 Conclusion For the micro-miniature compressed air energy storage system, the theoretical analysis model of compression process, gas storage and expansion process is established by thermodynamic theory. The energy storage efficiency and energy storage density are used as evaluation indexes to study the working characteristics of compressed air energy storage system under isothermal, adiabatic and multi-level variable working conditions. The influence of constant pressure and constant volume gas storage methods on system performance is analyzed and compared. . The results show that the gas storage pressure, compression and expansion process and gas storage method have great influence on the efficiency and storage energy density of the compressed air energy storage system. Increasing the gas storage pressure can significantly increase the energy storage density of the system; The compression process of compression intermediate cooling is beneficial to reduce the compression work. The expansion process of multi-stage compression intermediate heating can effectively increase the expansion output work; the higher the intake air temperature of the expander, the greater the expansion output work and the system energy storage efficiency; Compared with the capacitive gas storage system, the constant pressure system has a higher energy storage density, and the required gas tank volume is greatly reduced. The established theoretical analysis model of compressed air energy storage system can reflect the influence of key operating parameters on the operating characteristics of the system, and can provide a basis for designing a highly efficient compressed air energy storage system.

Features: The machine tool mold is integrated, and the base, column and beam are optimized and strengthened to improve the overall rigidity of the machine tool.
Materials: 
stainless steel, copper, aluminum, carbon steel, etc.
Applicable industries: 
molds, hardware, medical equipment, electronic products
Product use: 
mold, metal electrode, metal parts processing


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