| There are problems of large energy consumption and large carbon emission for winter heating in cold regions of China.In order to ease the status of increasing shortage of fossil energy and deteriorating ecological environment,the clean heating and“dual carbon”target in China are proposed.In recent year,the proportion of renewable energy applications in clean heating is increasing.Solar energy resources are abundant but it is difficult to stabilize heating alone,although air source heat pump is stable,energy saving and environmental protection,it has high cost and poor performance when heating in cold regions.Aiming at the problem that solar energy is difficult to stabilize heating alone and the high cost of air source heat pump heating,this paper proposes the concept of air source heat pump assisted solar energy stable heating,and achieves the goal of maximum utilization of solar energy for clean heating.Taking a single building with heating area of 120 m~2 in Green Village of Lanzhou City,Gansu Province as the heating object,a large flat plate solar collector-air source heat pump system is built and studied.Firstly,the heating load of the single building was calculated,and the selection of main equipment and system construction were completed.Secondly,the heating performance of the system under four typical working conditions of sunny,windy,overcast and snowy days were studied experimentally,and the experiment investigated the effect of different operation strategies on system performance.Then,a simulation model of the system was established and verified by experimental results,and performance of system during whole heating season was simulated.Finally,the energy,economic and environmental benefits of the system were evaluated.The major results of this paper from the above study are shown as follows:(1).The heating performance of system under different typical operating conditions was investigated.The results of the study showed that:(1)The thermal collection efficiency of the system is 46.2%under sunny conditions,41.1%and 28.1%under cloudy and overcast conditions respectively.However,there was insufficient radiation and heat collection cycle was not turned on under snowy conditions.The solar fraction under the four working conditions is38.4%,29.3%,13.4%and 0 respectively.The large flat plate solar collector has higher solar fraction under different working conditions,which can be applied to cold regions.(2)The average COP of the air source heat pump is 3.5,3.3,3.1 and 3.5 when the system is operated under four typical working conditions of sunny,cloudy,overcast and snowy conditions,respectively.The average COP of the solar heat pump is 4.0 for all three typical operating conditions except snowy conditions is zero.The system average energy efficiency ratio is 3.45,3.16,2.63 and 3.10 respectively.(3)The power consumption of the heat pump under sunny,cloudy and overcast conditions can save 11.14 k W-h,9.35 k W-h and 3.65 k W-h respectively compared to snowy conditions,and the operating duration of the heat pump is shortened by6.54 h,4.93 h and 0.81 h respectively.The power consumption and operating duration of heat pump can be reduced while making full use of solar energy.(4)The indoor temperature of the single building in this test is maintained above 24℃,which verified the feasibility of this system for heating single buildings in cold regions of China.(2).The performance of the system under different operating strategies was studied by experiment.The switching temperature between the solar energy heat pump heating mode and the air source heat pump heating mode was set as 12℃,13℃,14℃,15℃and 16℃.By comparing the average test results of five operating strategies,it is found that the average COP of air source heat pump are 3.4,3.4,3.3,3.3 and 3.2.It can be judged that the operation of air source heat pump is basically stable.The COP of the solar energy heat pump are 4.0,4.1,4.2,4.1 and 4.1 respectively under five operating strategies.When the COP of the solar energy heat pump reaches the maximum,the switching temperature is 14℃.The average COP will decrease if it is less than or greater than 14℃.Therefore,the operation strategy with switching temperature of 14℃is the best,which can maximize the use of solar energy.(3).The heating performance of large flat plate solar collector-air source heat pump system in the enter heating season was simulated for whole heating season.The simulation results show that the average solar fraction is 38.66%.The average COP of the solar heat pump is 3.45 and the average COP of the air source heat pump is 2.60.The average energy efficiency ratio of the system is 3.22.This system has a high solar energy utilization rate throughout the heating season.(4).Through the analysis of economic,energy and environmental benefits of the system,it can find that the system can save 5144.51 kg standard coal in the whole heating season,and the primary energy saving rate is 69.0%.The investment recovery period of the system is only 6.4years.In the heating period,the carbon dioxide emission reduction is 13488.90 kg,the dust emission reduction is 51.45 kg,the sulfur dioxide emission reduction is 102.89 kg,and the nitrogen oxide emission reduction is 7459.54 kg.In this paper,a large flat plate solar collector-air source heat pump system for household in cold regions was constructed,and experimental study of heating performance of system for rural single building.It effectively solves the problems that solar energy is difficult to stabilize heating alone and air source heat pump exits huge consumption and poor performance in cold regions.It not only verifies the feasibility of the system for single building heating,but also helps to promote clean heating in northern and realize the goal of“dual carbon”of China. |
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