Design And Optimization Of Solar-ground Source Heat Pump Coupling System In Taiyuan Area

As a kind of clean and renewable energy,geothermal energy has received more and more attention in recent years.As a technology to develop shallow geothermal energy,ground source heat pump technology has been gradually applied to the field of construction.However,in cold regions,the problem of soil cold accumulation caused by ground source heat pump technology has not been well solved.In order to solve the above problem,this paper proposes a solution for the combined application of solar energy and ground source heat pump systems,and conducts related research on this.In this paper,the building load calculation of independent residential buildings in Taiyuan area is carried out by Transient System Simulation Program(TRNSYS)software.On this basis,combined with the engineering specifications,the solar-ground source heat pump coupling system is preliminarily designed,and the equipment is selected.After that,the independent ground source heat pump system is modeled by using TRNSYS software,and the operation variation law of soil,buried pipes and related variables of heat pump unit is studied.At the same time,the influence of the design parameters of the ground source side on the soil cold accumulation is also studied.On this basis,the optimal design of the independent ground source heat pump system is carried out.In addition,according to the principle of the solar-ground source heat pump coupling system,two operating modes of the solar-ground source heat pump coupling system are proposed: auxiliary heating mode and combined heating mode.The control strategies of the two operating modes are designed.At the same time,the numerical model of the coupled system is constructed by using TRNSYS software.On the basis of the model,the variation laws of soil,buried pipes and related variables of the heat pump unit under the two operating modes are respectively studied,and whether the two operating modes can reduce the cold accumulation of soil is evaluated.In addition,the auxiliary heating mode is mainly studied.The influence of the relevant design parameters of the solar collector cycle part on the soil cold accumulation in the auxiliary heating mode is studied,and the system design of the auxiliary heating operation mode is optimized.Finally,the economics of the solar-ground source heat pump coupling system is analyzed by using the annual cost method,and the environmental benefit evaluation of the coupling system is given.The main research results are as follows.(1)The results show that the cumulative heat load of independent residential buildings in Taiyuan in the heating season is much greater than the cumulative cooling load in the cooling season.When an independent ground source heat pump system heats and cools the building year-round,cold accumulation in the soil is bound to occur.(2)Both operating modes of the solar-ground source heat pump coupling system can reduce the degree of soil cold accumulation.Among them,the auxiliary heating mode operation mode can realize the system operation for 10 years,and the average soil temperature drops by only 0.2 °C;although the combined heating mode can reduce the cold accumulation of soil,the high return water after the water supply from the hot water storage tank will affect the normal operation of the heat pump unit.Therefore,attention should be paid to the piping design for combined heating.(3)When optimizing the coupling system,it should focus on optimizing the design parameters such as the distance between the buried pipes,the design flow rate of the buried pipes,the water supply temperature of the hot water storage tank,and the area of the solar collector.(4)In terms of economy,the annual cost of the solar-ground source heat pump coupling system is slightly higher than the annual cost of the municipal pipe network heating + airconditioning cooling,but the difference between the two is not significant.However,the environmental benefits of the coupling system are outstandingTo sum up,the solar-ground source heat pump coupling system can solve the problem of soil cold accumulation in cold regions.For independent residential buildings in rural areas that cannot be heated by municipal pipe network and have domestic hot water demand,the use of solar-ground source heat pump coupling system for heating and cooling is a better choice.The conclusion of this paper has certain reference value for the application of the solar-ground source heat pump coupling system in practical engineering.