The Research On The Performance Of MHP-PV/T And PV Inside And Outside The Solar Greenhouse In Winter

The coordinated development of photovoltaic(PV)energy and modern facility agriculture has great potential for realizing the comprehensive "decarbonization" of the energy system and solving the global climate and environmental crisis.Traditional solar greenhouses will face the problem of crop wilting caused by high temperature at noon;in the process of integrated utilization with PV,they will also face the conflict of light demand between crop photosynthesis and photovoltaic power generation.PV only converts part of solar radiation into electrical energy,and its energy utilization rate is low.At the same time,due to differences in solar cell material types,PV arrangement,PV coverage,and solar greenhouse structure,the power generation performance of the PV system and the environmental climate in the solar greenhouse have certain differences.At present,there are many researches on PV greenhouses at home and abroad,but no one has used MHP-PV/T as a shading device in solar greenhouses.Comparative study of MHP-PV/T(Micro Heat Pipe Photovoltaic/Thermal)in cold winter areas Output performance and shading effect under different environmental conditions inside and outside the solar greenhouse.At the same time,there are few reports on the performance of outdoor MHPPV/T and the performance of MHP-PV/T with or without insulation layer at different inclination angles in winter.This paper takes MHP-PV/T and PV as the research object and the solar greenhouse as the application background.Two sets of experimental devices are designed and built respectively,installed inside and outside the solar greenhouse.The experimental devices change the working inclination angle of MHP-PV/T and PV through the rotation of the motor.Comparatively studied the photovoltaic power,photovoltaic efficiency,thermal power,thermal efficiency,total energy yield and total energy efficiency of MHP-PV/T and PV under different tilt angles inside and outside the solar greenhouse in winter,and clarified the role of MHP-PV/T The influence of the internal shading device on the temperature and humidity in the solar greenhouse at different inclination angles;in order to study the outdoor working performance of the MHPPV/T system at different inclination angles in winter,the two sets of MHP-PV/T were placed at 30°-45.°,30°-60°,30°-75°,30°-90°,45°-60°,45°-75°,45°-90°,60°-75°,60°-90°,Under the inclination angle of 75°-90°,the optoelectronic performance,photothermal performance and comprehensive performance of the two systems were compared and studied,and the optimal inclination angle of the MHP-PV/T system performance under outdoor conditions in cold areas was proved.In order to study the outdoor working performance of the MHP-PV/T system at different inclination angles in winter,the two sets of MHP-PV/T were placed at 30°-45°,30°-60°,30°-75°,30°-90°,45°-60°,45°-75°,45°-90°,60°-75°,60°-90°,75°-90° inclination angles,comparatively studied the electrical performance of the two systems,Thermal performance and comprehensive performance have proved the best inclination angle of MHP-PV/T system performance under outdoor conditions in cold areas.The research shows that the difference in performance of MHP-PV/T inside and outside the solar greenhouse is mainly due to the wind speed,temperature and solar radiation in the indoor and outdoor environment.For this reason,this paper uses 10 mm aerogel felt insulation material to heat the MHP-PV/T and explores Its performance is different from that of uninsulated MHP-PV/T.The main research contents and conclusions are as follows:(1)In winter,comparing the performance of the MHP-PV/T system under five different inclination angles of 30°,45°,60°,75°,90° inside and outside the solar greenhouse,it is found that the power generation performance of OMHP-PV/T is superior OPV system photoelectric performance,IMHP-PV/T power generation performance is better than IPV system but inferior to OPV system;in terms of photothermal performance and comprehensive performance,IMHPPV/T system has better performance than OMHP-PV/T.(2)The surface temperature of PV gradually increases with the increase of solar radiation intensity.As the temperature is higher,the Fermi energy level of PV decreases,gradually approaching the valence band,and the open circuit voltage becomes smaller.At this time,the short-circuit current has a smaller influence factor.Therefore,the output electric power also shows a downward trend.The solar radiation intensity is an important factor affecting the efficiency of PV power generation.The greater the solar radiation intensity,the higher the power generation efficiency.However,when the surface temperature of the PV exceeds 22.8 °C,the voltage generated by the PV will offset its radiation rise due to the increase in temperature.The output voltage will be greatly reduced.Therefore,when the PV surface temperature is lower than 22.8 ℃,the power generation efficiency and surface temperature of the system will increase with the increase of solar radiation;when the surface temperature is higher than 22.8 ℃,the power generation performance of the system is greatly affected by the temperature,showing a V-shaped change Trend,negatively correlated with temperature rise.(3)Under the condition that the coverage ratio is 5.4%(PV occupies the area of the shed film)and the ventilation system is closed,study the MHP-PV/T at the inclination angles of 25°,30°,45°,60°,75°,and 90°.The influence of the system on indoor temperature and humidity,and it was found that MHP-PV/T converts solar radiation into electric and thermal energy while realizing effective shading.In winter,the temperature and humidity of the experimental group are smaller than those of the control group.During the whole experiment,the average temperature of the experimental group was reduced by 1.1 ℃ compared with the control group,and the average humidity of the experimental group was reduced by 10.2% compared with the control group.The indoor temperature and humidity are changed by solar radiation and wind speed.The indoor humidity throughout the day decreases with the increase of solar radiation,and the temperature increases with the increase of solar radiation value.(4)In cold winter areas,the electrical power and electrical efficiency of the MHP-PV/T system are optimal when the inclination angle is 45°,and the electrical performance relationship at the other inclination angles is: 30°> 60°> 75°> 90°,while MHP-The thermal efficiency,thermal power,total energy power and total energy efficiency of the PV/T system are the best at an inclination angle of 30°,and the worst at 90°,followed by: 45°> 60°> 75°.(5)Through a comparative study of whether the MHP-PV/T is equipped with an insulation layer,it is found that the projection of the bracket on the PV surface has a greater impact on the electrical efficiency of the system,about 2.6%-3.2%.Compared with the MHP-PV/T system without heat preservation,the addition of aerosol felt insulation material increases the average thermal efficiency of the system by 16.9%,the average total energy efficiency increases by14.6%,and the electrical efficiency decreases by 0.9%.