| The energy consumption of domestic hot water system is an important part of the total energy consumption of building.Solar energy combined with air source heat pump hot water system makes full use of renewable energy,which can not only overcome the disadvantage that the temperature of water cannot meet the requirement under climatic condition such as low solar radiation intensity,but also effectively make up the deficiency of performance degradation of heat pump at low outdoor temperature,and it is of positive significance to the promotion of building energy-saving and other development strategies.At present,there are few studies on the dual water tank system which using solar energy preheating combined with air source heat pump heating operation mode,compared with the conventional single water tank system,the water supply of this system is more stable and reliable,and can make better use of solar energy resources,so it is worth further study.In this paper,an existing project of a student dormitory in a university in Tianjin was taken as the research object firstly,and a simulation model of the solar energy and air source heat pump combined heat source domestic hot water system was established by using TRNSYS.The results show that the the annual solar fraction and solar collector thermal efficiency are 28.63%and 43.90%,respectively.COP of the system and COP of the heat pump vary in the range of 2.76～6.26 and 2.62～3.93 throughout the year,respectively.By comparing the simulation results with the measured data of the whole year,it is found that the deviation of useful energy gain of solar collector is less than 5%,and the deviation of power consumption and heating capacity of heat pump are less than 10%,indicating that the model is accurate.Secondly,the simulation models of hot water system with other heat source were established.The results show that the daily water supply temperature of independent solar hot water system fluctuates greatly throughout the year,so it is not appropriate to popularize it in Tianjin.But it is theoretically feasible to use a timing solar hot water system alone in summer.MATLAB was used to fit out the formulas of COP of heat pump changed with outdoor temperature and inlet water temperature in all the four seasons in Tianjin,which have high goodness of fit.Compared with air source heat pump,electric heating element,solar energy and electric heating element combined system,the annual energy-saving,economic and environmental protection benefits of solar energy and air source heat pump combined system are significant.Finally,the orthogonal test was designed by SPSS to analyze different combinations of the system,and the order and significance of the effect of the important parameters in component such as solar collector on the system performance were studied.When the system performance is optimal,the combination is that the collector slope is 40°,the collector area is 400 m~2,the rated heating power of air source heat pump is 20 k W,the volume of preheat tank is 13 m~3,and the optimal matching principle between the collector area and the rated heating power of air source heat pump is 0.05k W/m~2.By integrating TRNSYS with GENOPT,the design scheme when the system economy reached the optimum was obtained by iterative calculation using pattern search method.The collector slope is 42.9°,the collector area is 255 m~2,the rated heating power of air source heat pump is 72000 k J/h(20 k W),the volume of preheat tank is 12.7 m~3.The rated heating power of heat pump per unit collector area is 0.078k W/m~2,and the annual cost is 86979.67 yuan. |
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