Study On Operation Regulation Of Solar Energy Heating System With Seasonal Water Tank Storage

In recent years,with the implementation of the policy " Clean Energy Instead of Coal ",clean energy heating has been gradually applied in all parts of the country.People pay more and more attention to the development of solar district heating.Energy planning of "13th Five-Year" promotes solar heating as a key policy,and we should grasp the opportunity to deepen the study of the theory and technology of seasonal heat storage solar heating,so as to promote the development and implementation of the engineering application.At present,the solar district heating with seasonal storage technology in China is still in the initial stage.There are still many problems in the project demonstration,design optimization and operation regulation,which leads to the imbalance of heat supply after the solar district heating system is put into operation,resulting in the waste or unqualified of heat supply.The solar district heating technology with seasonal storage in the European countries such as Denmark and Germany is mature,but it is not suitable to be adopted completely because of the large difference between population density,land resources,building form,heating mode and so on.It is necessary to combine the experience of foreign countries and deepen the independent research of relevant technology according to the situation of our country.In this study,a solar district heating system with seasonal water tank and water source heat pump as the auxiliary heat source is proposed.The key parameters affecting the energy efficiency of the system are analyzed by the energy balance and energy transfer model of the components of the system,and the change of the water temperature of the seasonal heat storage tank during the heating period is also analyzed.Providing adjustment plan and control strategy for the system,and a TRNSYS simulation model corresponding to the system is established.Finally,combined with the previous theory,a project in Dalian is taken as the research object to analyze the operating characteristics of the system,and the application value and significance of the theoretical research are proved to provide theoretical support for the development of the large-scale solar district heating with seasonal storage technology in China.First,by analyzing the energy balance mathematical model of each component of the solar heating system and the energy transfer model of the whole system,the natural parameters and design parameters of the key parameters affecting the energy efficiency of the system are determined.Among them,the area of the collector,the installation inclination of the collector and the volume of the heat storage tank are most important.Second,in order to match the heat supply with the heating load,combining the characteristics of the decreasing water supply temperature in the heat storage tank during the heating period,it is clarified that the heating regulation is not suitable for the use of the quality control scheme.Therefore,the isothermal difference quantity regulation under different working conditions is put forward.The regulation scheme is given and the corresponding control strategy is given.Third,building the TRNSYS simulation model of the solar heating system and verifying the correctness of the model through the measured data,provide the simulation platform for the rationality of the research and control method and the analysis of the system operation characteristics.At the same time,the key problems and solutions of the TRNSYS modeling process of the solar heating system are summarized,which will provide reference for the simulation research of the related personnel in the future.Fourth,taking a solar district heating system with seasonal water storage in Dalian as an example,this paper simulates the running characteristics of the heating system according to the TRNSYS simulation model.In order to reduce the heating amount,the Dest software is used to determine the intermittent heating operation mode.The energy saving rate is 8.14%.Also,the solar energy guarantee rate is taken as the target,based on the non interactive orthogonal test method,the collector area of the collector is 8000m2,the collector angle is 45° and the water tank capacity is 13300m3.The operation characteristics of TRNSYS simulation results are analyzed with the isothermal difference quantity regulation and control strategy proposed in this study,including the temperature of the outlet of the collector,heat transfer efficiency,the temperature of the heat storage tank,the heat storage,the heat supply and the heat load,and so on.Under the supply mode,the heating load of SDHS-SS is equal to the heat load,and the indirect heating mode controls the water supply temperature of SDHS-SS at 45~53℃.Under the water source heat pump auxiliary heating mode,the heat supply and temperature can meet the heat load as much as possible.This paper recommends a solar district heating system with seasonal heat storage with a collector area of 8000m2,a collector angle of 45° and a tank volume of 13300m3 in the residential of Dalian area of 2.4×104m2.And the solar energy guarantee rate was 100% in November and December,and the monthly average solar energy between January and April was between 70%~75%.