Photovoltaic Continuous Glass Greenhouse Photothermal Environment Research And Optimization

Photovoltaic continuous glass greenhouse is the product of close combination of modern agricultural facilities and clean and efficient energy.The electricity generated by photovoltaic can be used for watering,lighting and heat preservation,etc.It is an emerging modern agricultural facility with good development prospects.However,the annual environment of photovoltaic glass greenhouse is different,and the indoor temperature is too high or too low will have adverse effects on the growth of flowers.In this thesis,in order to improve the environmental quality of the greenhouse,we take the photovoltaic glass greenhouse in Jianghuai area as the research object,and study the annual change law of each environmental factor of photovoltaic glass greenhouse and the change law of each environmental factor of typical weather in different seasons.The experiment was conducted in two parts:1.Long-term monitoring and comparative analysis of annual environmental factors inside and outside the photovoltaic continuous glass greenhouse and each environmental factor in typical weather in different seasons.In this experiment,the photovoltaic panels of PV continuous glass greenhouse were 50%covered on the roof,and the light intensity,air temperature and humidity,soil temperature,and heat flow density inside and outside the PV continuous glass greenhouse were monitored and analyzed in four seasons of summer,autumn,winter,and spring according to the time sequence of the experiment conducted,to study the change pattern,aiming to provide a decision basis for the production management of PV continuous glass greenhouse.The results showed that:(1)The average outdoor light intensity of photovoltaic continuous glass greenhouse in summer,autumn,winter and spring is 34579.7,28372.5,26708.6,27302.6 lx;the annual light distribution in the greenhouse is even,and the shading net is opened when the outdoor light is strong in the greenhouse,and the average indoor light intensity in summer,autumn,winter and spring is 3787.9,3745.6,3185.8,3623.3 lx respectively,The average outdoor air temperatures in summer,autumn,winter and spring were 32.0,17.1,1.6 and 6.1 ℃,while the average indoor air temperatures in summer,autumn,winter and spring were 26.2,24.4,20.2 and 23.5 ℃,respectively.The indoor temperature was appropriate in summer,autumn and spring,while the indoor temperature was lower in winter.The average air relative humidity outside in the four seasons of summer,autumn,winter and spring was74.1%,71.7%,67.6% and 73.1%;the average air relative humidity inside the greenhouse was 89.3%,79.4%,59.4% and 60.1%,respectively,and the indoor air relative humidity was higher in summer and autumn and slightly lower in winter and spring.(2)The average soil temperatures of PV continuous glass greenhouse in summer,autumn,winter and spring were 24.4,18.5,16.3 and 17.1 ℃ on sunny days and 24.6,19.8,16.8 and 18.4 ℃ on rainy days,respectively,and the soil temperature in the greenhouse on rainy days was higher than that on sunny days.The ground heat flow density of PV continuous glass greenhouse in the four seasons of summer,autumn,winter and spring is higher in heat storage during daytime and lower in heat storage at night,which indicates that PV continuous glass greenhouse has better heat insulation performance and is conducive to maintaining a more stable indoor temperature and humidity environment.2.Combined with CFD to simulate the temperature field of PV continuous glass greenhouse in winter,so as to propose the optimization plan of air supply outlet layout in greenhouse and solve the problem of low indoor temperature of PV continuous glass greenhouse in winter.In this test,the PV continuous glass greenhouse was selected for the study at 07:00 am.on December 23 rd in winter,and the measured data and CFD were used to simulate the indoor temperature field to study its better layout plan for air conditioning supply outlets,and the results of this study are shown as follows:(1)Simulation of the indoor temperature field of the PV continuous glass greenhouse at three times in winter,morning,midday and evening,by CFD,and comparison of the simulated values with the measured values,the results show that the average relative errors of the three times are 3.6%,2.3% and 2.4% respectively,indicating that the measured and simulated values are in good agreement,and the simulated values are more accurate to reflect the temperature field changes in the PV continuous glass greenhouse.(2)The original layout of air conditioning vents in the PV continuous glass greenhouse was asymmetric,and no air conditioning vents were installed in the local area;after optimization,the layout of air conditioning vents in the greenhouse was symmetrically distributed,and all areas of the greenhouse were equipped with air conditioning vents,and the total number of air conditioning vents was two units less than the original model.By optimizing the layout of air conditioning vents in the PV continuous glass greenhouse through CFD,the temperature field in the greenhouse is more uniform than the original model,and the overall air temperature in the greenhouse in winter is increased,and the temperature in the greenhouse is about 23 ℃;the temperature in the local lower temperature area is significantly increased compared with the original model,and the temperature in the local lower area is increased by about 10 ℃,which is a good optimization effect.