Research On Optimization Design Of Integrated Energy System Based On Compressed Air Energy Storage

In order to help achieve the goal of "carbon peaking and carbon neutrality",it is urgent to vigorously develop a distributed energy system with renewable energy as the main body and promote the clean and low-carbon transformation of the energy structure.In the actual application process,the energy output of renewable energy is generally characterized by intermittenity,volatility,mismatch with end-use energy demand and poor controllability.How to improve the consumption ratio of renewable energy and meet the reliable and stable supply demand of end-users for a variety of energy is a big problem to be solved urgently.Compressed air energy storage technology,as the hub of distributed energy and user-side energy interaction,has the characteristics of multienergy fed and multi-energy co-supply,which can well solve the problems faced by multi-energy Fed co-supply in distributed comprehensive energy system,and is an important solution for the collaborative and comprehensive utilization of a variety of clean energy under the dual-carbon target.Aiming at the key scientific problems of the integrated energy system based on compressed air energy storage,such as single heat source,limited temperature,large carbon emission of coupled gas turbine,and lack of integrated optimization methods of parameter design and capacity allocation,this paper proposes an integrated energy system based on zero-carbon energy such as photovoltaic and photothermal energy,supplemented by adiabatic compressed air energy storage.Based on the mass conservation relationship and energy balance relationship,the thermodynamic model of the system is established,the system evaluation index system is constructed,and the calculation method of electro-electrical efficiency and comprehensive energy efficiency considering the difference of energy grade is proposed.A 120 k W distributed compressed air energy storage demonstration system in an agricultural park in northwest China was tested to verify the accuracy of the thermodynamic model.The influences of external factors such as compressor compression ratio,turbine expansion ratio,minimum storage pressure of air reservoir,intake temperature of turbine,ambient temperature and altitude on system performance are deeply analyzed.Finally,with maximum comprehensive energy efficiency and minimum system cost-benefit ratio as optimization objectives,a two-layer optimization model of comprehensive energy system based on compressed air energy storage was established,and an integrated optimization design method for parameter design and capacity allocation was constructed.The optimization design method was applied to a demonstration park to verify the feasibility of the proposed method.The main conclusions are as follows:(1)The comparative analysis between the experimental test results and the simulation results shows that the relative errors between the measured values and the simulated values of the key parameters and the system efficiency indexes in each running stage of the system are all within 5%,and the thermodynamic simulation model established in this paper has a high accuracy.(2)For the multistage compression CAES system,adjust the compression ratio so that the compression ratio of the first or second stage compressor is slightly greater than that of the third or fourth stage compressor,which can improve the system performance,and the electro-electrical efficiency and comprehensive energy efficiency reach the maximum value of 55.15% and 77.36% respectively when the compression ratio is 0.9.(3)For the CAES system with multi-stage expansion,adjusting the expansion ratio of the third or fourth stage turbines to be slightly larger than that of the first or second stage turbines can improve the system performance.The electro-electrical efficiency reaches the maximum value of 55.13% when the expansion ratio is 1.2,and the comprehensive energy efficiency reaches the maximum value of 77.46% when the expansion ratio is 1.4.(4)The minimum air storage pressure of the air storage tank has a great influence on the power generation time of the system.The minimum air storage pressure of the air storage tank is increased,the utilization rate of the air storage tank is reduced,and the power generation time of the system is shortened.When the minimum storage pressure of the air storage tank is increased from 3.5MPa to 8MPa,the generation time is shortened from 8.6h to 2.6h.(5)Increasing the turbine inlet air temperature can effectively improve the electroelectrical efficiency and comprehensive energy efficiency of the system.When the inlet air temperature of the turbine increases from 110℃ to 240℃,the electro-electrical efficiency of the system increases from 50.71% to 64.34%,and the integrated energy efficiency increases from 73.90% to 84.76%.(6)Altitude has a great impact on system performance.The electro-electrical efficiency and comprehensive energy efficiency of the system decrease with the elevation increasing.When the altitude increases from 0m to 3000 m,the electroelectrical efficiency of the system decreases from 55.03% to 22.56%,and the comprehensive energy efficiency decreases from 77.29% to 47.49%.(7)The optimization results of the demonstration park show that the cost-benefit ratio of the system under the three scenarios is 0.110 yuan /k Wh,0.097 yuan /k Wh and0.069 yuan /k Wh respectively,which are all lower than the local conventional energy price of 0.388 yuan /k Wh.For each 1k Wh of energy supplied by the system,the economic benefits can be obtained by 0.278 yuan,0.291 yuan and 0.319 yuan respectively.Compared with the integrated energy system without energy storage,after the introduction of compressed air energy storage system,although the initial investment has increased by 316,000 yuan,it can save 4556 MWh of primary energy every year,reduce 593.6 tons of carbon dioxide,the primary energy saving rate of25.86%,and the carbon dioxide emission reduction rate of 13.7%.