| Solar air source heat pump composite heating system can overcome the problem of unstable and volatile heating performance of a single solar heating device,while improving the operating conditions of air source heat pumps,and improving the efficiency of system operation.Therefore,the system is used for heating in northern rural areas,which is of great significance to help the national"carbon peak"and"rural revitalization"strategies.In this paper,based on summarizing the advantages and disadvantages of different forms of solar air source heat pump composite heating system,combining the characteristics of end-use heat demand in northern rural areas,a multi-mode operation composite heating system combining solar air collectors and air source heat pumps is proposed.By setting up heat storage modules and using straight-through tube collectors to heat air and then send it directly to the load room,we reduce energy loss and improve the rationalization of solar resource utilization efficiency of the system.Typical rural buildings in the Jinan area are selected for the study,and combined with the building envelope and function,the modeling and time-by-time heat load calculation of the building using Trnsys yielded a typical building thermal index of 72 W/m~2.A simulation model of the solar heat pump composite heating system was built.Calling the Java-based language optimization algorithm module,multi-objective optimization of the system with heat collection and integrated cost as the objective function,and collector inclination irradiance for optimal inclination and azimuth parameters were obtained.The optimal area of the air collector under the objective function is 21 m~2and the optimal volume of the heat storage tank is 0.16 m~3.The characteristics of the system operation under four operation modes are simulated,and the influence law of the change of switching parameters on the change of energy efficiency of the system under different modes is studied.A multivariate optimization-seeking calculation of the system with annual operating energy consumption as the objective function is performed by Genopt.The results show that the lowest system heating season energy consumption is3139k Wh/a with the optimized strategy,and the combined system COP before and after optimization is improved from 3.5 to 3.8.An experimental bench was built based on the optimized system,and the operational performance of the system on a typical day was studied.The experimental data such as room temperature,tank temperature,mode running time,collector temperature,heat collection,energy consumption,and comprehensive COP of the system were compared with the simulated data.The results show that the average combined energy efficiency of a typical daytime composite system is 5.47 during the daytime,2.59 during the nighttime hours,and 3.0 throughout the day.The relative error of the mean value of the integrated COP of the system between the experimental test and the theoretical simulation is around 4%,and the deviation is within a reasonable range,which also verifies the accuracy of the theoretical model.Finally,the system was analyzed and evaluated in terms of its performance,economy and eco-efficiency,and the composite heating system was compared with conventional single heat pump system,gas wall-hung stove system,and coal-fired stove system using the annual value of cost method.The overall system performance COP is 3.7 for the whole heating season under intermittent operation with partial load(A),and 3.2 for the whole heating season under full load(B).The lowest annual value of solar air source heat pump combined heating system cost in two load forms,intermittent operation and continuous all-day operation,at 1931 RMB/d and 2807RMB/d,respectively.Comparing the composite heating system with the air source heat pump system and coal-fired furnace system,the composite heating system has lower pollutant emissions and significant environmental benefits.The solar air source heat pump composite heating system established in this paper is energy efficient,with high economic and ecological benefits,and has good promotion value for promoting clean heating projects in northern areas. |
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