Research On Simulation And Optimization Of Solar Seasonal Thermal Storage Heating System

Solar energy heating with seasonal thermal storage is one of the hot topics in the field of building energy saving.Seasonal thermal energy storage heating technology can store excess solar energy in summer for winter use,which can solve the problem of mismatch between supply and demand of solar energy,also improve the stability of solar system and increase the utilization rate of renewable energy.Therefore,how to design the operation mode and improve the economy of the small-scale solar seasonal heat storage heating system with high performance is the key problem to develop the solar seasonal heating technology.In this subject,a combined long-term and short-term storage heating system with water to water heat pump and its operation mode are proposed.The research is carried out by combining theoretical analysis with numerical simulation,and an evaluation index is proposed according to the energy balance among the subsystems.A numerical simulation platform of the system is established and verified by modular modeling.The system operation characteristics throughout the year are analyzed by dynamic simulation.The system design parameters are further optimized.The main content and achievements of this research include:(1)A solar seasonal thermal storage system suitable for small-scale distributed heating and its annual operation regulation scheme are proposed.In order to solve the problem of low energy utilization of traditional solar seasonal storage heating technology,the form of long-term and shortterm heat storage tank combined heating system integrated with water to water heat pump is proposed,and the annual operation regulation mode based on the dynamic matching of heat supply and demand is set.Compared with the seasonal thermal enregy storage heating system with a single storage device,the advantage of the long-term and short-term heat storage coupling scheme is that the short-term heat storage tank can buffer the high-temperature hot water at the outlet of the collector during non heating period,and provide a stable heat source temperature for the buried seasonal heat storage tank at the same time;In the later stage of heating,the heat can be replenished in time through the shortterm heat storage tank,so as to reduce the demand for auxiliary heating.(2)Based on the dynamic energy balance of source-storage-load,the system numerical simulation platform is established.Taking a single residential building in Nanjing as the research object,the initial equipment parameters are determined according to the building heat load.Taking the energy flow transfer relationship of various components as the core,the whole system mathematical model including solar collector,seasonalal heat storage water body,short-term heat storage water tank,buffer water tank,circulating water pump,building load and other main unit modules is built based on TRNSYS software.Then the accuracy of the model is verified according to relevant literature and engineering data.(3)The simulation platform is built based on the dynamic characteristics of the whole year.The temperature variation trend and energy transfer of the system under the source-storage-load unsteady boundary condition are analyzed in different time dimensions.Taking the electric auxiliary heating as a reference,the effect of the coupling of water to water heat pump on the energy efficiency of solar seasonal heat storage heating system is explored;Taking the heat storage form of a single storage device as a reference,the effectiveness of the combined scheme of long-term and short-term storage tanks is verified.(4)The main influencing factors of system energy efficiency are analyzed and optimized.The main influencing factors of the system: the inclination angle of the solar collector,the heat collection area and the volume of the long-term and short-term heat storage tank are quantitatively analyzed,so as to reveal the influence mechanism of these parameters on the system performance.The multi factor orthogonal simulation test is carried out for the multi heat source coupling system in this study.It is found that the increase of the volume of the short-term storage tank has a greater impact on the solar assurance rate than the seasonal storage tank.It is suggested that for the design of small distributed heat storage heating system,the overall efficiency cost ratio can be improved by increasing the heat storage capacity of short-term heat storage body.Furthermore,the double effects of the flow of the hot water pump on the thermal stratification degree of the water tank and the performance of the heat pump are analyzed and optimized.(5)The system is evaluated from three aspects of energy efficiency,cost and environment.The results show that the solar fraction of the optimized system is 87.6%,the annual energy consumption is 1608 k Wh,and the carbon dioxide emission is 3557.51 kg.The energy-saving effect is remarkable and there is long-term development space.The annual cost of the system is 15747 yuan,but the average annual cost per household can be reduced by 11200 yuan on the premise of reaching the same system energy efficiency after expanding the building volume by 15 times,indicating that increasing the scale of the system can effectively improve the economy.In practical engineering,it can be considered to supply heating and domestic hot water for multiple villas or single high-rise buildings.