1. Photovoltaicphotothermal integrated cooling technology
While reducing the temperature of the solar cell, the heat taken away by the fluid is used, and this system can also provide heat energy while improving the efficiency of power generation, which can be called photovoltaic photothermal integration (PV/T) system. Under the same external conditions, the PV/T system can more effectively reduce the operating temperature of the solar cell. In the actual situation, in order to effectively reduce the temperature of the solar cell as much as possible, the inlet cooling water temperature of the PV/T collector is low, and the outlet water temperature of the PV/T collector is also low, and the solar radiation energy collected by the PV/T collector cannot be efficiently utilized. The PV-SAHP system combines the evaporator of a solar cell and a heat pump system to form a PV evaporator. In the solar irradiation received by the PV evaporator, part of the energy is used for photovoltaic power generation, and the other part of the energy is absorbed by the PV evaporator, and the heat can be used after the circulation of the heat pump system. The PV-SAHP system can not only effectively reduce the solar cell temperature, but also improve the efficiency of the heat pump.
2. Experimental principle and device PV-SAHP
The principle of the system experiment is to set a cooling coil on the back of the solar cell, and the cooling coil is also used as the evaporator of the steam compression heat pump system. The refrigerant absorbs the heat emitted by the solar cell through the phase change in the cooling coil, so as to achieve the purpose of cooling the solar cell. At the same time, the heat pump system circulates the heat absorbed by the evaporator and releases it through the condenser, which can be used for domestic heating.
3. Analysis of experimental results
3.1 Changes in the operating temperature of solar cells
It can be seen that in the working stage of the heat pump system, the working temperature of the solar cell decreases significantly. The highest time of 08-29 temperature is 14:00, and the operating temperature of the two groups of solar cells is the highest, the highest temperature of the cooled group is 45℃, and the highest temperature of the uncooled group is 55℃. The temperature difference is also the largest in the day at 14:00, with a temperature difference of 10 ° C. The highest time of 08-30 temperature is 15:00, and the operating temperature of the two groups of solar cells is the highest, the highest temperature of the cooling group is 45℃, and the highest temperature of the non-cooling group is 63℃. The temperature difference is also the largest in the day at 15:00, with a temperature difference of 18 ° C. Through the experimental results, during the working time of the system, the average temperature of the 08-29 solar cell decreased by 8℃, and the average temperature of the 08-30 solar cell decreased by 12℃. This shows that the heat pump evaporator has a good cooling effect on the solar cell, which is very important for solar cell power generation.
3.2 Changes in solar cell power generation
Under the same environmental conditions, it can be seen that in the working stage of the refrigeration device, the power generation of the cooled solar cells is significantly higher than the power generation of the uncooled solar cells. The highest power generation time of 08-29 is 14:00, and the power generation power of the two groups of solar cells is the highest, the highest power generation power of the cooled group is 181.1W, and the highest power generation power of the uncooled group is 172.2W. The power increase is also the largest in a day at 14:00, with a maximum power increase of 8.9W. The highest time of 08-30 temperature is 15:00, and the power generation power of the two groups of solar cells is the highest, the highest power generation power of the cooled group is 176.1W, and the highest power generation power of the uncooled group is 165.5W. The power increase is also the largest in a day at 15:00, and the power increase is up to 11.1W. Through the analysis of the experimental results, it is obtained that the moment when the heat pump evaporator reduces the temperature of the solar cell to the maximum (08-29T14:00, 08-30T15:00) is also the moment when the solar cell power generation is the highest, which once again proves that the heat pump system has a positive effect on the solar cell power generation. During the working time of the system, the average power of 08-29 solar cells is increased by 6.9W, which is about 4%. 08-30 Solar cell power generation increased by an average of 8.2W, an increase of about 5%.
4. Conclusions
The PV-SAHP system can effectively reduce the working temperature of the solar cell, improve the photovoltaic power generation, and efficiently utilize the waste heat of the solar cell, realize the dual use of solar energy, and improve the energy-saving effect of the system. In this paper, the experiment and hybrid prediction of PV-SAHP system are carried out, and the conclusions are as follows: (1) PV-SAHP system combines the evaporator of solar cell and solar heat pump system to form PV evaporator. The PV-SAHP system can not only effectively reduce the temperature of the solar cell, but also improve the efficiency of the heat pump. (2) Set up a photovoltaic solar heat pump system, PV evaporator can effectively reduce the working temperature of solar cells, the maximum temperature can reach 18 ° C, the average decrease of 10 ° C, photovoltaic power generation efficiency increased by about 5% on average.
