Study Of Multi-Energy Complementary Distributed Energy Heating System Based On Solar Energy Storage

The development of a multi-energy complementary distributed energy system based on renewable energy such as solar energy not only contributes to alleviating the crisis of traditional fossil fuel depletion,but also accelerates the transformation and upgrading process of China’s energy structure,which contributes to achieving the carbon peaking and carbon neutrality goals.However,the intermittent and unstable characteristics of renewable energy such as solar energy,as well as the local consumption and long-distance transmission of renewable energy,have affected the application and promotion of the system.Therefore,utilizing energy storage technology to efficiently store surplus energy becomes the key to ensure the stable operation of the system.In the traditional renewable energy system,using a single thermal storage pit for thermal storage has the problem of poor flexibility in system operation and regulation,which directly leads to low energy efficiency of the system.Therefore,this paper proposed a multienergy complementary distributed energy heating system based on solar energy storage.The system not only uses the seasonal thermal storage pit for long-term thermal storage,but also uses the thermal storage tank for short-term thermal storage,which improves the flexibility of the system operation.At present,the common way of system research is using the TRNSYS simulation platform to build a system model for conducting study,however this method cannot make a profound study on specific components in the system,so this paper built the system on TRNSYS simulation platform and verified it with experimental data,further using ANSYS FLUENT to conduct study on components of the thermal storage pit and the thermal storage tank in the system to improve the thermal storage capacity of the system.A multi-energy complementary distributed energy heating system based on solar energy storage was constructed on TRNSYS simulation platform by combining simulation and experiment.The thermal storage subsystem is composed of seasonal thermal storage pit and thermal storage tank.The thermal storage tank was used to improve the flexibility of the system.The operating data of the model system was compared with the data of the experimental greenhouse,which proved that the model was accurate and effective.On this basis,Particle Swarm Optimization(PSO)was used to obtain the optimal allocation ratio of solar heat collection area and thermal storage volume with the annual operating cost as the objective function.On the basis of the constructed TRNSYS model,ANSYS FLUENT was used for numerical simulation of seasonal thermal storage pit and thermal storage tank.According to the similarity theory,the governing equation in the numerical simulation process was mathematically derived.The result shows that when the model is reduced to n times the size of the prototype,the simulation time needs to be shortened by n times,and the simulation speed needs to be expanded by n times to keep the temperature field in the model consistent with the prototype.Using this method to carry out numerical simulation can significantly reduce the amount of calculation in the calculation process.Under the soil condition of Jinan area,the thermal storage efficiency of the seasonal thermal storage pit was continuously improved with the increase of the buried depth,but the effect of increasing the buried depth on improving the thermal storage efficiency decreased when the buried depth exceeds 1.5 m.By comparing the variation of internal temperature and flow fields between the cylindrical and the quadrangular platform,it was found that the wall structure of the quadrangular platform can reduce the natural convection intensity near the wall,which reduced the heat dissipation efficiency in the process of thermal storage.For the traditional thermal storage tank,the structural optimization design was carried out.By assembling the thermal insulation panel,the thickness of the inclined temperature layer inside the thermal storage tank was reduced and the thermal storage efficiency was improved.The numerical simulation of the thermal storage process of the thermal storage tank before and after the structural optimization showed that the addition of the thermal insulation panel can effectively separate the hot and cold fluids in the thermal storage tank,and significantly reduce the thickness of the inclined temperature layer.Exergy analysis for the thermal storage tank system was carried out based on the numerical simulation results.The exergy analysis results showed that the installation of thermal insulation panel can reduce the exergy loss of the thermal storage tank system and improve the energy utilization rate of the system.Finally,TRNSYS simulation platform and ANSYS FLUNT numerical simulation were combined to optimize the design of the whole system and thermal storage devices.During the research process,PSO algorithm,similarity theory and other research methods were used.The results are contributed to improving the thermal storage performance of the system,and have guiding significance for the construction and development of solar energy based multi-energy complementary distributed energy heating system in northern China.