Research On The Performance Evaluation And Optimization Design Of Natural Gas Combined Cooling Heating And Power System With Thermal Energy Storage

Natural gas distributed combined cooling heating and power (CCHP) system is ofhigh energy utilization rate, good environmental protection performance, energy supplysafety and reliability, shift peak to valley and good economic benefit. In recent years, itsapplication is getting more and more attention. However, because of the CCHP systemclose to the end user, when the building load is fluctuating, cogeneration systemfluctuates with the building load, which resulting in part load working condition, thusthe equipment efficiency is low. Since energy storage system (TES) helps to eliminatethe mismatch between energy demand and supply in time and intensity, Thecogeneration system with TES can operate efficiently with so high overall energyefficiency.In this paper, the main research contents and contributions are as follows:The CCHP system components models are reviewed, for the micro-gas turbine, asemi-empirical analytical model is proposed combined the first law of thermodynamicsand the catalog of product, and it is used for the establishment of the system analyticalmodel.Based on the analytical model of the system with the ideal TES model, thetraditional working mode (Following the thermal load mode (FTL) and following theelectrical mode(FEL)) are analyzed to evaluate the efficiency improvement of CCHPwith TES.①The building load characteristic parameters based on the efficiency ofCCHP with TES are proposed, including: electric to heating factor, electric (heat)fluctuation factor, electric load phase deviation factor;②In the FTL mode, thefunction of TES is to reduce the fluctuation of micro-gas turbine working condition; Inthe FEL mode, the function of TES is to reduce the mismatch between heat supply anddemand;③The optimal phase change energy storage temperature should begeometric of gas turbine outlet flue gas temperature and environmental temperature forthe gas turbine without heat recovery; the optimal phase change energy storagetemperature should be the temperature of the generator of absorption machine for thegas turbine with heat recovery. Then the conclusion are used to evaluated the functionon TES in CCHP for kinds of building types. It is found that for the office and commercial facilities, the function of adding TES in CCHP are obvious; for the hospital,the function of TES in CCHP is obvious in winter and not obvious in summer; for therestaurant, the function of adding TES in CCHP are not obvious in summer and winter.For energy storage optimization design and operation of CCHP system with theideal TES model, for the constant and variable conditions, the optimization design andoperation principle of system is analyzed. The optimal operation mode for the constantcondition is FTL mode; for the variable condition, the optimal operation model is FTLmode by designed and working follow the thermal load average value.Next, the numerical model of CCHP with TES for the ideal phase change energystorage and real phase change energy storage are established, genetic algorithm anddynamic programming algorithm are used to get the optimal design and operatingstrategy of system. The analytical solution is validated, the optimum design andoperation strategy is gotten with the ideal phase change energy storage model. Besides,for the actual phase change energy storage, the influences of the capacity and heat lossof TES on design and operation of system are analyzed.