Optimization And Economical Study Of Solar Heating System With Pit And Tank Thermal Storage

In order to solve the contradiction of seasonal mismatch of solar central heating resources,the seasonal solar heating technology of pit heat storage can store the solar energy in the longterm heat storage pit during the heating season and take it away during the heating season.However,the existing problems of the pit thermal storage solar heating system include: under the condition that the water temperature in the storage pool is lower than the heating temperature in the middle and late period of heating,the heat provided by the collector entering the large capacity thermal storage pit cannot effectively raise the water temperature,leading to the reduction of the solar energy utilization rate of the system;At the same time,the investment cost of the system is high,and the technical and economic applicability of the system in different climate zones is not clear.Therefore,in the context of the national development strategy of "carbon peak and carbon neutral",how to improve the energy efficiency and economy of the solar interseasonal storage heating system is the key problem to be solved urgently in the development of solar interseasonal heating technology.Aiming at the problems of low solar energy utilization rate and high cost of the traditional cross-season solar heating technology with single pit heat storage,this research adopts the method of combining theoretical analysis and numerical simulation to carry out the work.The main research work includes: proposing the system form and operation regulation mode of SHS-PTTS;The numerical simulation platform of serial and parallel SHS-PTTS system was established and verified.The operating characteristics of different water storage solar heating systems are analyzed throughout the year.Based on the relatively optimal system form,a multiconstraint optimization equation with the minimum economic cost as the objective function was established,and the optimal design parameters and economic indexes of SHS-PTTS system with different thermal zoning were obtained.The specific content and main results of this study include:(1)Put forward the series and parallel SHS-PTTS system form and the annual operation adjustment mode.In order to solve the problem of low energy efficiency of the traditional seasonal water heat storage solar heating technology,the SHS-PTTS system is proposed.According to the connection mode of short-term heat storage tank(" tank ")and long-term heat storage pit(" pit"),it can be divided into series and parallel forms.A year-round regulation mode based on heat supply and demand matching is set.Compared with the singlepit seasonal heat storage solar heating system,the SHS-PTTS system has the following advantages: the tank in the non-heating period can buffer the high temperature hot water at the outlet of the collector and provide a stable heat source temperature for the pit;Heating period can be directly through the tank heating,in order to reduce the consumption of auxiliary heat source.(2)The numerical simulation platform of serial and parallel SHS-PTTS system was established and verified.In order to provide an experimental platform for SHS-PTTS system performance research,the TRNSYS numerical simulation platform construction method of SHS-PTTS system was proposed,and its accuracy was verified.First,determine the component model,connection mode,edit the control statement of the device operation,and set the global control parameters such as simulation step size,start and stop time.Then,through the relevant literature and engineering data to determine the parameters of each component design basis;Finally,the accuracy of the model is verified according to the experimental data of an seasonal water storage heating house in Shandong.(3)Verify its effectiveness based on the operating parameters of SHS-PTTS system.In order to analyze the operating characteristics of SHS-PTTS system throughout the year and determine the optimal system form,the series and parallel SHS-PTTS system and the conventional single pit thermal storage solar heating system were simulated and analyzed.The results show that the solar guarantee rate of the tandem SHS-PTTS system is 92%,which is3.15% higher than that of the parallel SHS-PTTS system,and 5.17% higher than that of the traditional single-pit seasonal thermal storage solar heating system.It is the best SHS-PTTS system with the best relative performance.(4)Multi-constraint design parameter optimization based on SHS-PTTS system economy.In order to analyze the economic applicability and optimization design parameters of SHS-PTTS system in different regions,a multi-constraint optimization function of PSO-HJ hybrid optimization algorithm was established with the minimum economic cost as the objective parameter and the solar guarantee rate,collector area,tank and pit volume as the constraint conditions.Taking Urumqi in the severe cold region,Lhasa in the cold region and Hefei in the hot summer and cold winter region as the case,the optimization analysis results show that the heating quantity per unit cost of the three typical heating regions is 7.27GJ/ ten thousand yuan,5.52 GJ/ ten thousand yuan and 5.08 GJ/ ten thousand yuan,respectively.The main investment ratio in the life period is 6:1:2;For Lhasa,where SHS-PTTS system is most suitable,the economic cost of the system is the lowest when the volume of pit per unit collector area is 1.66,the volume of tank is 0.18,and the volume ratio of pit to water tank is 9.11.Compared with the life period of SHS-PTTS system before optimization,the main investment in the system is reduced by 27.85%.