Research Of Solar-ground-coupled Heat Pump In Serere Cold Region

Ground-source heat pump system is a new type of energy-efficient andenvironmentally friendly system. It uses shallow geothermal energy as cold and heatsources and is not subject to regional and resource constraints. As a kind of cleanenergy, it has great development potential. However, in cold regions, the hugetemperature difference between winter and summer leads to the phenomenon that alarge amount of energy will be taken out from the ground-source heat pump in winterwhile a small amount of energy will be exhausted from it in summer. With thelong-term operation of the system, a phenomenon of "cold accumulation" will occur,which means that the temperature of the soil surrounding the ground heat exchangerswill be reduced. Thus, the gradual reduction of soil temperature directly causes thedecline in performance coefficient and the breakdown of the system.To solve this problem, this paper focuses on the solar ground-coupled heatpump. The renewable solar energy are used as an auxiliary heat source to assist theoperation of ground-source heat pump. Meanwhile, the solar heat absorbed in thetransitional seasons is stored in the soil to supplement the excessive consumption ofheat in winter.The author first conducts a comprehensive analysis and calculation of the solarenergy, and then introduces the working principle of the solar ground-coupled heatpump system. According to the characteristics of these two kinds of heat sources, theoperating mode suitable for this study is determined; then, the mathematical model ofthe solar ground-coupled heat pump system is simplified and the start relationshipbetween different modes is quantitatively determined; further, a simulationcalculation of the solar ground-coupled heat pump system is carried out.In order to determine the reasonable scopes of solar collectors under differentworking conditions in winter, transitional seasons and summer in cold regions, thedistribution ratio of solar energy to soil energy under different working conditions isfirstly determined. For the quantitative analysis of the two heat source systems, the author establishes the finite volume model of ground heat exchangers. With singleU-shaped ground heat exchanger as the research object, a simulation calculation isconducted on its changes in various soil temperature fields under different workingconditions. The results show that:Based on the simulation calculation, a numerical simulation about the thermalstorage and heating cycle of the system is performed to obtain the law of the changesin soil temperature fields after thermal storage as well as the imbalance ratio ofenergy taken out to energy exhausted.With the law of the changes in underground soil temperature and the imbalanceratio mentioned above as the indicators, the author optimizes the solar collector areaso that it is the most reasonable when the solar energy accounts for30.44%of thetotal heat load.Then, from en economic point of view, the author optimizes the collector andestablishes a mathematical model of the annual cost of solar energy and the area ofthe collector. By calculating the objective function, the author concludes that the bestcollector area for the100-square-meter building in Changchun is253.26squaremeters when the solar ground-coupled heat pump system is adopted.In the heating and cooling systems for buildings in cold regions, how to reducethe cold accumulation in the soil and achieve a constant ground temperature is acommon concern of many scholars. With the solar collector as the auxiliary heatsource, the U-shaped ground heat exchanger for soil heat storage, and the computerfor real-time optimal control, the problems like reduced take-out energy anddegraded system performance caused by the reduction in the underground soiltemperature can be effectively controlled. Solar energy is rich in resources andenvironmentally friendly, so this paper studies the seasonal soil heat storage in thesolar ground-coupled heat pump system.