Study On Operating Performance And Optimizing Strategy Of Natural Gas CCHP And River Water Source Heat Pump Composite System

With the further promotion of the sustainable development strategy of energy in the country and Chongqing area,the application of natural gas CCHP and river water source heat pump system in Chongqing area has attracted widespread attention.On the basis of their respective advantages,the combined energy supply system of CCHP and river water heat pump can also alleviate the gap between heat and power ratios on both sides of the supply and demand,make full use of the advantages of high cooling?heating?efficiency of the heat pump system in the Three Gorges Reservoir Area,and make full use of the surplus generated power by the natural gas CCHP system.Studys on natural gas CCHP and river water source heat pump composite system,especially the studys on large-scale systems is less,and the testing analysis on the operation performance of the actual project is more scarce.In order to study the operation performance of large-scale natural gas CCHP and river water source heat pump composite system under different operation modes,as well as the method and effectiveness of operation optimization,so as to enhance the economic and social benefits of the operation of the composite system,a single-objective and multi-objective operation optimization method for composite system was proposed.Four operation modes of composite system were optimized,and the optimization effect of each optimization objective was evaluated.The main influencing factors of the operation performance of composite system were analyzed.The results of the research were verified by the actual measurement of the case project,and then the measures to improve the performance of the system and their effects were put forward.Finally,the economy of project operation was analyzed,and the pricing scheme of cold?heat?price was given.The main contents and conclusions are as follows:First,the typical internal combustion generator,the flue gas hot water type direct-fired lithium bromide absorption unit and the river water source heat pump unit are taken as an example,and mathematical models is established to characterize the operating performance of the variable operating conditions,and the correlation model between internal combustion generator and the direct-fired lithium bromide absorption unit is established in four operating conditions,which are heating or cooling with waste heat,direct combustion and afterburning.Secondly,according to the principle of meeting the demand of cooling and heating load in building area,the composite system is divided into three subsystems which can operate independently and 28 units combination forms,and the realization path of the composite system optimization is put forward.The operation exergy economic cost,primary energy utilization rate,exergy efficiency,thermal economic cost are selected as the optimization objective,the single-objective operation optimization of the composite system is carried out,the optimal operation strategy of the composite system is determined,and the energy consumption and output of the composite system are calculated.The operation strategy based on different optimization objectives mainly affects the gas consumption and power generation of the system.Thirdly,a systematic description of the compound system?s operation mode is made,which are“download the lack and discard the rest”,“download the lack and sell the rest”,“download the lack and upload the rest”,“download all and upload all”,and the operation performance of the composite system under different modes is analyzed.Compared with the optimization objective,the operation mode has a greater impact on the primary energy utilization,thermal economic cost and efficiency of the composite system in each season.Under each optimization objective,the optimal operation mode of the composite system should be selected according to the season,which can further improve the annual seasonal energy efficiency ratio of the system or reduce the economic cost of operation.Then the queuing scoring method is used to evaluate the optimization effect of each optimization objective.The results show that the optimization effect of the two optimization objectives,thermal economic cost or operational economic cost is better.Based on this,a comprehensive performance parameter CE_f,s is proposed to optimize the operation strategy of the four operation modes,and the operation performance of the composite system is calculated.The results show that CE_f,s as the optimization objective can further improve the performance of the composite system.Then,the operation performances of heat pump system,direct-fired lithium bromide absorber system and composite system were tested,and their operation performances were analyzed.The accuracy of the model was verified.The comprehensive performance parameters and thermal economic costs were taken as optimization objectives respectively,the performance of the composite system under the measured operating conditions?download the lack and discard the rest?and"download the lack and upload the rest"were analyzed,and the optimization effect was verified.Taking the comprehensive performance parameters as the optimization objective,the average thermal economic cost of the system is 17.84%lower than the measured value,and the average comprehensive performance parameters are 42.44%higher than the measured value.Then,from the aspects of operation mode,operation strategy,temperature difference between river water intake and return,temperature of water intake,and temperature difference between air conditioning water supply and return,the improvement measures of the operation performance of the composite system are analyzed.The energy saving and emission reduction situation of the composite system is analyzed comparing with actual working conditions,and the optimal operation scheme is given.Based on this,the improvement effect of the above factors on the operation performance of the whole case project is analyzed.Then,the project life cycle cash flow statements is drawn,and the life cycle economic evaluation of the composite system is made.The break-even point of cooling and heating price and upload power price are analyzed when the price of natural gas,downloaded electricity and water resources changes.The single-factor sensitivity of the main static and dynamic evaluation indicators to the prices of the five sources of energy?independent variables?is analyzed.Finally,the principle of cooling?heating?pricing is put forward,and the influence of download power price and natural gas price on cooling?heating?pricing of composite system is analyzed.And the cost savings of energy station operators and the cooling?heating?consumers are also analyzed compared with conventional air conditioning schemes when the price of natural gas or download power price changes.The analysis methods and conclusions in this paper are also instructive and referential to other distributed energy systems,water source heat pump systems and gas absorption systems.