The Study Of Solar Fraction Of Solar Assisted Ground-source Heat Pump System

With the development of economy, energy is gradually towards run out. In order to achieve sustainable development, energy strategies are imperative, such as fulfill energy-saving and emission-reduction, develop new energy and renewable energy. Solar energy and shallow geothermal energy are clean energy so that solar assisted ground-source heat pump sysytem has more potential in building energy efficiency field. Solar fraction reflects the utilization of solar thermal in such a system. It is an important design parameter. Solar energy is easily affected by geography, climate, load characteristics and other factors, the issues involved are complicated, so that it is difficult to study the best solar fraction for a system. Observe the present-day world, study for this problem is relatively deficient at home and abroad. Therefore, this article gave advices on how to determine solar fraction.Firstly, this article designed and established solar assisted ground-source heat pump sysytem. The experimental system can achieve three running modes, including cooling, heating and energy storage.The system can entirely meet the demand of experimental study.Secondly, for further system analysis, this article established a mathematical model in TRNSYS software platform which is corresponding to the experimental system. Once completed, three groups of experimental study started. Analysis showed that the mathematical model in this article was relatively accurate and can be used in system research which is more comprehensive.Finally, useing the model which had been validated, this article worked for analysing solar fraction for such a system. One office building in Dalian city which met specification requirements was selected for example to analysis the best solar fraction concretely.Using DeST software to calculate building load and TRNSYS software to analyze system performance. Choosing collector area, tank volume, storage temperature, depth of ground heat exchanger, quantity of ground heat exchanger as factors, using orthogonal test method to analyse the sensitivity of system solar fraction. Based on operation energy consumption, soil temperature balance, economical efficiency and other factors, reasonable proposals were given. Combining analysing the best solar fraction in different regions, different building types and different building energy saving rates, this article gave suggestions synthetically. On the basis of the above analysis, this paper concludes:collector area is the highly significant influencing factor of solar fraction when heating, when designing, choosing collector area should make the system has high economic behavior and low operation energy consumption furthest, in addition, soil temperature should be balanced furthest. This is the way to determine the best solar fraction, it is closely related to solar energy resource reserve, shape coefficient of building, building load characteristic, building energy saving rate.