| Energy consumption is an inevitable problem in the agricultural production process.In order to meet the energy demand,the global photovoltaic power generation is growing exponentially.Greenhouse planting can increase crop yield to solve the food shortage caused by population growth;combining photovoltaic modules with greenhouse can realize sufficient supply of new energy and reduce the consumption of traditional energy.Photovoltaic modules laid on the roof of the greenhouse not only provide electricity for the greenhouse load,but the layout of the photovoltaic modules changes the distribution of light,temperature and humidity in the greenhouse,changing the parameters required for the growth of the greenhouse crops.In this dissertation,the 26.25 m2strawberry photovoltaic greenhouse was taken as the research object.The irradiance,temperature and humidity distribution in the greenhouse were studied to investigate the effect of changes in greenhouse environmental factors on the photosynthetic rate of strawberries,and to obtain a range of light,temperature and humidity environmental parameters suitable for strawberry growth.Combined with the correlation of strawberry growth and environmental factors,based on the maximum net photosynthetic rate requirement of strawberry,the energy supply of photovoltaic greenhouse was analyzed,and the fruit quality of strawberry was compared before and after energy supply was compared.The main research work in this dissertation includes the following aspects:（1）This dissertation constructs an indoor irradiation model for photovoltaic greenhouses and investigates the effect of PV module layout on the distribution of photosynthetically active radiation inside the greenhouse under typical day conditions.According to the long-wave limit of absorption of radiation wavelengths by photovoltaic cell materials,this dissertation obtains the pattern of changes in photosynthetically effective radiation in greenhouse rooms after shading by photovoltaic modules.The results of the study showed that the greenhouse with PV modules reduced irradiation by 41%on the summer solstice compared to the winter solstice.When the PV modules cover 20%of the roof area,the photosynthetically active radiation inside the greenhouse is below 550μmol·m-2·s-1throughout the year;when the coverage area reaches 40%,the photosynthetically active radiation inside is below 300μmol·m-2·s-1.（2）This dissertation uses the energy balance equation to model the indoor temperature and humidity in a greenhouse and to analyse the effect of PV module shading on the indoor temperature and humidity environment in four typical days.The results show that the difference in greenhouse temperature is not significant when the greenhouse is not shaded by PV modules.The difference in indoor temperature between 0.4 m and 0.8 m above the ground is approximately 0-1℃;At 0.8 m above the ground,the difference in indoor temperature with and without PV module shading is approximately 0-2℃.Compared to the greenhouse humidity on the other three typical days,the humidity on the vernal equinox was more suitable for strawberry growth,with values between 45%and 65%.（3）In this dissertation,strawberry net photosynthesis rate model was established,and the influence of indoor environmental factors on strawberry net photosynthetic rate was analyzed.The changes in photosynthetic rate of strawberry at different heights in the greenhouse during four typical days were investigated under the shading of PV modules.The results show that the optimal photosynthetic rate is about300μmol·m-2·s-1and the photosaturation point is about 550μmol·m-2·s-1;the optimal temperature and humidity range are 22-25℃and 55%±5%respectively.After the greenhouse was shaded by the PV module,the average photosynthetic rate of strawberries at 0.8 m above the ground was higher than that at 0.4 m above the ground in the spring equinox and winter solstice,at 4.71μmol·m-2·s-1and 5.53μmol·m-2·s-1,respectively;in the summer solstice and autumn equinox,the average photosynthetic rate of strawberries at 0.4 m above the ground was higher than that at0.8 m above the ground,at 4.8μmol·m-2·s-1and 4.83μmol·m-2·s-1,respectively.（4）This dissertation addresses the problem of mismatch between PV power generation and electricity demand in winter in PV greenhouses based on crop growth requirements,and improves system economy and Self-consumption rate by adjusting the relationship between PV capacity,battery capacity and heat storage;At the same time,this dissertation studied three cooling methods of photovoltaic greenhouse in summer,and obtained the system cooling load and energy supply characteristics at the target temperature of 22℃and 25℃,respectively.The results show that in order to meet the system heat storage capacity exceeding 52.5 k Wh,the battery capacity should exceed 4 k Wh;when the heat storage capacity is 35 k Wh and the photovoltaic capacity is 2.19 k W,the battery capacity is at least 14 k Wh before the system meets the requirements of greenhouse heating and the self-consumption rate is higher than0.8.After increasing the target temperature from 22℃to 25℃,the system energy consumption decreases and the cooling load decreases by at least 44%.Finally,the fruit quality of strawberries before and after energy supply was analysed.Summer and winter energy supply increased strawberry fruit weight,soluble solids by a maximum of 10 g and 18 g,76%and 84.21%,respectively.In conclusion,the research content of this dissertation can provide a reference and basis for the environmental regulation of photovoltaic greenhouse. |
