Design And Thermal Field Analysis Of Single Ridge Venlo Type Photovoltaic Glass Greenhouse

Recent years have witnessed a constant technological innovation in photovoltaic(PV),reduction in the price of PV components and an increasingly extensive application of new energy.Photovoltaic power generation is no longer confined to the power station and has been used in many different fields,ranging from rechargeable arteries to high-rise buildings.Facility agriculture has drawing an increasing attention due to people's pursuit of higher living standard.Greenhouse is a representative of the facility agriculture,which makes agricultural production possible anywhere and anytime,whether in the plateau,high mountains or the deserts.PV greenhouse is the combination of PV and greenhouse.It has the advantages of no land occupation,greenness and pollution free,and energy efficiency.The development and wide application of PV greenhouses are inevitable trend.A reasonable design of PV greenhouse is crucial to reduce the adverse influence of PV components on the internal environment of the greenhouse.Single-ridge Venlo glass greenhouse has found the widest applications so far.Transforming this type of greenhouse into PV greenhouse is considered the most costly and most feasible.Here,we performed simulation experiments using CFD software on single-ridge Venlo glass greenhouse.Firstly,the influence of the area ratio of PV components on the internal temperature field of Venlo glass greenhouse was studied.Eighteen different area ratios of PV components were experimented on the front slope,and the internal temperature fields of the greenhouse were obtained accordingly by simulation.Comparison and simulation indicated that(1)the internal temperature field of the greenhouse showed a gradient increase pattern from the bottom to the top;(2)the temperature decreased linearly with the increasing area ratio of PV components;(3)the relationship between the average temperature inside the greenhouseand the ratio area of PVcomponents was fitted as=-0.0737+312.28.Secondly,thermal field analysis was performed using CFD software,based on which the design of the Venlo PV greenhouse was optimized.Vents for cold and hot air and cooling mechanism were designed.The following conclusions were drawn by simulation:(1)Opening the vents for cold and hot air was conducive to cooling of the greenhouse and the uniform distribution of temperature field;(2)wind velocity at the inlet for cold air had a certain impact on the cooling effect and uniformity of internal temperature field distribution.The relationship between the average temperature inside the greenhouseand the wind velocity at the inlet for cold airwas fitted as=1.2321~2-3.2607+298.67;(3)Wind velocity had only a limited impact on the cooling effect(i.e.,final temperature).Greenhouse temperature was mainly influenced by the temperature of air entering the greenhouse;(4)Wind velocity had a greater impact on the cooling rate of the greenhouse.Thirdly,Panax notoginseng,a medicinal herb indigenous to Yunnan Province,was planted in the specially designed Venlo PV greenhouse as an experiment.In order to meet the requirements of Panax notoginseng on the growth environment,soil cooling design was added to the greenhouse.Simulation results indicated that the temperature inside the greenhouse was reduced to about 296K and the temperature distribution was uniform.This can fully meet the growth requirement of Panax notoginseng.