Study On Energy Saving Operation Of Solar-ground Source Heat Pump Composite System

Ground source heat pump(GSHP)is good one of the heating methods in northern China.Since the annual heating load of buildings in northern China is much larger than cooling load,long-term operation for GSHP will cause temperature of soil to drop,which could be solved by using solar energy.The research of the solar-ground source heat pump composite system(SGSHPCS)is about operation efficiency of SGSHPCS based on maintaining soil thermal balance mostly.However,an energy saving operation method that increase the solar collectors of the composite system on the basis of soil thermal balance is proposed in this article,and the impact of the method on energy consumption and cost of the system is discussed.Firstly,the air-conditioning load of buildings in Harbin,Shenyang and Dalian are simulated using TRNSYS software.Combined with the simulation results,the method is used to guide the design of the operation mode and parameters of the key equipment of SGSHPCS in the three regions.Secondly,the simulation models of SGSHPCS in the three regions are built,and the 15years operation of SGSHPCS are performed by using TRNSYS.The results show that the soil temperature in Harbin,Shenyang and Dalian increased by 107.50%,81.09%,58%,respectively.The whole year operation efficiency of the system has increased year by year in Harbin and Shenyang,while it has slightly decreased in Dalian.Compared with the first year,the whole year system COP in the 15th year has increased by 6.6%,3.75%,-0.71%in the three regions,respectively.Therefore,the applicability of the method to different regions is ranked as:Harbin>Shenyang>Dalian.Thirdly,the method of matching optimization for the area of solar collectors and the number of buried pipes is proposed to reduce the initial investment of SGSHPCS.When the cost of solar collectors and buried pipes is 700 yuan/m~2,60 yuan/m respectively,the initial investment of the system after optimization in Harbin,Shenyang and Dalian has dropped by2.5%,2.8%,6.6%,respectively.Following the orthogonal experimental design using simulation is used to optimize some parameters of the system.The whole year system COP of the three regions increased by 4.64%,11.96%,6.63%respectively.Then,the optimized SGSHPCS2 that using the method is compared with the SGSHPCS1 maintaining soil thermal balance on the aspects of energy saving and economy.The results show that SGSHPCS2 has significant energy-saving advantages in Harbin and Shenyang,and lesser energy-saving advantages in Dalian.And economic advantage is closely related to the cost of solar collectors and buried pipes.Finally,aiming at the problems of frequent shutdown when the heat pump unit operating and unreasonable distribution of heating load among different heating modes,and the demand for variable flow operation of GSHP,a heating strategy based on BP neural network and fuzzy-PID control based on genetic algorithm have been proposed.The on/off numbers of the unit has been reduced effectively by the heating strategy,which increases the operation efficiency of heat pump.The PID control performance under step response has been improved by fuzzy-PID after genetic algorithm optimization,which also has better control effect when the gain of the object transfer function increases.Then,the two control methods have been written as PLC programs,which enhance the practical applicability of these methods.