Study On Characteristics Of Variable Working Condition Of Coal-fired Unit Coupled CAES System

Energy storage is a strategic emerging industry strongly supported by the state.It is an urgent need to solve large-scale access to renewable energy,improve the efficiency,safety and economy of conventional power systems and regional energy systems.It is the supporting technology of the energy revolution.The low-quality electric energy that fluctuates drastically will be turned into stable-high-quality electrical energy.Compressed air energy storage(CAES)has the advantages of low unit cost,large scale,safety,environmental protection,and long life.As a result,The system of CAES has developed rapidly.This paper establishes a coal-fired unit and compressed air energy storage coupling system to improve the economics and flexibility of the unit.Based on the in-depth analysis of the characteristics of each device in the coupling system,the general law of economic indicators of coal-fired units under different working conditions is studied.The article uses thermodynamic methods to analyze the coupled system from the following aspects:1.The paper briefly describes the thermodynamic characteristics of ideal gas and air,and establishes the mathematical model of each equipment inside the coal-fired unit and CAES coupling system.2.We used Aspen Plus simulation software to build a compression subsystem and expansion subsystem model.The effects of compressor and air turbine stage,speed,air flow and pressure on power and efficiency are analyzed.The effects of gas storage pressure and temperature on the volume and energy density of the gas storage device were investigated.3.The paper determined the main equipment parameters of the coupling system.The number of compressor stages is four,the system uses equal compression mode,the inlet air temperature is 273K,the final pressure is 10MPa,the power is 14.32MW;the air turbine level is four,the equal expansion method is adopted,and the inlet temperature is473K.The pressure is 8.1 MPa,the output power is 10.1 MW,and the volume of the gas storage device is 1600 m~3.4.The Aspen Plus simulation software is used to build the unit simulation model.The static model is validated under different working conditions.The coupled model simulation model is built by Aspen Plus simulation software to analyze the thermal economy of the unit under different working conditions.The results show that the heat loss rate of the coupled system increases,the economy decreases,and the lower the power generation load of the unit,the higher the heat consumption rate.5.The cost and benefits of the coupled system are calculated.Costs include investment costs,operating costs,depreciation and amortization expenses,and maintenance costs.Revenues include coal-saving gains,peaking gains and subsidies.The calculation shows that the total investment is 1.06919 billion yuan,the annual income is1237.2million yuan,and the investment recovery period is 8.64 years.