| Compressed air energy storage system has the advantages of large capacity,long energy storage cycle,long life,easy to adjust,etc.It can flexibly realize the complementary integration with other energy systems.In order to improve the adjustment flexibility of cogeneration units in thermal power plants,and increase the peak-regulating capacity of the system and the proportion of renewable energy into the network,a new coupling scheme of cogeneration units and compressed air energy storage system is proposed in this paper.In this scheme,the compressed air energy storage system is used to store electric energy and the compressed heat is used to provide heat to increase the heating proportion of the system.In the stage of enhanced power supply,exhaust steam of the cogeneration unit is used to heat the inlet air of the expander of the energy storage system so as to increase the power generation ratio of the system.In this paper,the mathematical model of thermodynamic and off design characteristic analysis of the new integrated system is established.Under the three operation modes of intensified heating mode,intensified power supply mode and independent operation of thermal power plant,the appropriate evaluation indexes(efficiency,thermal efficiency and thermal power ratio)are selected to evaluate the operation performance of the integrated system,The research shows that the new integrated system has advantages in efficiency and thermal power ratio.Compared with the reference system,the efficiency of the new integrated system is significantly improved,and the thermal power ratio is also broadened.According to the parameters of key components such as air flow rate,compressor efficiency,expander efficiency,expander inlet air temperature,intercooler(or reheater)heat transfer pressure loss in the key subsystem compressed air energy storage system,the influence of these parameters on the thermal efficiency,exergy efficiency and thermal electric ratio of the integrated system is analyzed.The results show that the exergy efficiency and exergy efficiency of the new integrated system are relatively affected The larger is the air flow of compressed air energy storage system,and the larger is the inlet air temperature of expander;with the increase of the main steam flow into the turbine,the total process exergy efficiency and thermal efficiency of the system increase about 5%and 8%respectively.The results show that the loss of boiler components is about 20%,which accounts for the largest proportion;then the loss of cold source is about 10%.The compressed-air energy storage subsystem was optimized under variable operating conditions.According to the optimal operating control law of the compressed-air energy storage system,the mathematical model of the coupling system under variable operating conditions was established.As the thermal and electrical loads changed,it revealed the influence rules of the key parameters of the integrated system:fuel volume ratio,air flow rate of the compressed air system and air back pressure/inlet pressure on the exergy efficiency and thermoelectric ratio of the integrated system.The study shows that air flow has the greatest influence on exergic efficiency and thermoelectric ratio of the integrated system during the heating enhancement stage.The influence of fuel ratio on exergic efficiency of the integrated system is the least.In the stage of power supply enhancement,the exergy efficiency and thermoelectricity ratio of the integrated system were most affected by fuel ratio,while the exergy efficiency of the integrated system was least affected by air inlet pressure.When the pressure of the gas storage chamber was constant,exergic efficiency and thermoelectric ratio increased monotonously with the increase of fuel volume ratio. |
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