In the tropical regions represented by Hainan,there are abundant solar and thermal resources,and it is relatively suitable for the construction of photovoltaic greenhouse(PVG).However,the construction of PVG still rel...In the tropical regions represented by Hainan,there are abundant solar and thermal resources,and it is relatively suitable for the construction of photovoltaic greenhouse(PVG).However,the construction of PVG still relies mainly on experience and is incapable of quantifying the balance between the photovoltaic(PV)generation and the light requirements for agricultural production.As a result,actual PVGs are primarily PV-based,without carefully considering the needs of agricultural daylighting.To quantify the influence of the design parameters of PVGs and the layout of PV panels on the internal daylighting of serrated PVGs,and to optimize the daylighting design of the roof,this paper utilizes the Design Builder software to establish gradient models for a multi-span serrated-type PVG in tropical regions.Gradient models were established in terms of aspects,namely span,width of longitudinal/transverse daylighting strip,height,roof angle,and photovoltaic panel coverage rate(PCR).Daylighting in the greenhouse of each gradient model was simulated,and with the annual average daily light integral(A_(DLI))and distribution uniformity(DU)as evaluation indicators,the influence of various design parameters on the daylighting inside the greenhouse was quantified.The result reveals that:(1)PCR is the decisive indicator for daylighting in the PVG,and a function between PCR and the A_(DLI) is derived as A_(DLI)=-15.5 PCR+16.841;(2)Increasing the width of longitudinal daylighting strip significantly improves the A_(DLI) and enhances DU while increasing the span has a noticeable effect on improving A_(DLI) but does not significantly enhance DU;(3)Increasing the eave height without changing PCR does not enhance A_(DLI) but effectively improves DU;increasing the transverse daylighting strip and adjusting the roof angle hardly improves A_(DLI).In summary,it is recommended that the optimal span for PVGs in tropical regions be set within the range of 6.5-8.0m,and the eave height be set within the range of 2.5-3.5m.Preferably,the longitudinal daylighting strip with a width ranging from 0.5-0.8m should be installed.Based on the above relationship function,the PCR can be calculated according to the appropriate light demand for the cultivated crops.The daylighting design theory proposed in this paper can provide a theoretical basis and reference for the healthy development of the PV industry in tropical regions.展开更多
Increasing the temperature of photovoltaic systems reduces electrical efficiency,output power,as well as results in permanent damages in the long-term run.A new hybrid PV/PCM-Rib system with three different rib pitch ...Increasing the temperature of photovoltaic systems reduces electrical efficiency,output power,as well as results in permanent damages in the long-term run.A new hybrid PV/PCM-Rib system with three different rib pitch ratios of Λ =4,Λ =2 and Λ =1 is investigated to reduce PV temperature and achieve uniform temperature distribution.A comprehensive two-dimensional model of the systems is developed and simulated with a fixed inclination angle of 30°.A parametric study is carried out to investigate the impact of ribs on different melting temperatures(50,40 and 30 ℃).According to the numerical results and the parametric analysis,using ribs shows better performance in temperature reduction for PCM with a lower melting temperature.By lowering the melting temperature of PCM from 50 to 30 ℃,the average temperature reduction of PV/PCM-Rib in the case of Λ =1 increases from 1.39% to 5.16% while the average melted PCM decreases from 20.5% to 7.59% after 240 min.It means that using ribs provides more solid PCM.It is also obtained that the electrical efficiency and output power show more increments at lower melting temperatures.展开更多
基金2024 Science and Technology Commissioner Service Group's Emergency Science and Technology Research Project for Wind Disaster Relief in Hainan Province(ZDYF2024YJGG002-8)China Huaneng Group Co.,Ltd.Headquarters Technology Project,Optimization of Photovoltaic Vegetable Greenhouse Structure and Research on Planting Agronomy in Tropical Regions(HNKJ22-HF77)。
文摘In the tropical regions represented by Hainan,there are abundant solar and thermal resources,and it is relatively suitable for the construction of photovoltaic greenhouse(PVG).However,the construction of PVG still relies mainly on experience and is incapable of quantifying the balance between the photovoltaic(PV)generation and the light requirements for agricultural production.As a result,actual PVGs are primarily PV-based,without carefully considering the needs of agricultural daylighting.To quantify the influence of the design parameters of PVGs and the layout of PV panels on the internal daylighting of serrated PVGs,and to optimize the daylighting design of the roof,this paper utilizes the Design Builder software to establish gradient models for a multi-span serrated-type PVG in tropical regions.Gradient models were established in terms of aspects,namely span,width of longitudinal/transverse daylighting strip,height,roof angle,and photovoltaic panel coverage rate(PCR).Daylighting in the greenhouse of each gradient model was simulated,and with the annual average daily light integral(A_(DLI))and distribution uniformity(DU)as evaluation indicators,the influence of various design parameters on the daylighting inside the greenhouse was quantified.The result reveals that:(1)PCR is the decisive indicator for daylighting in the PVG,and a function between PCR and the A_(DLI) is derived as A_(DLI)=-15.5 PCR+16.841;(2)Increasing the width of longitudinal daylighting strip significantly improves the A_(DLI) and enhances DU while increasing the span has a noticeable effect on improving A_(DLI) but does not significantly enhance DU;(3)Increasing the eave height without changing PCR does not enhance A_(DLI) but effectively improves DU;increasing the transverse daylighting strip and adjusting the roof angle hardly improves A_(DLI).In summary,it is recommended that the optimal span for PVGs in tropical regions be set within the range of 6.5-8.0m,and the eave height be set within the range of 2.5-3.5m.Preferably,the longitudinal daylighting strip with a width ranging from 0.5-0.8m should be installed.Based on the above relationship function,the PCR can be calculated according to the appropriate light demand for the cultivated crops.The daylighting design theory proposed in this paper can provide a theoretical basis and reference for the healthy development of the PV industry in tropical regions.
基金Project(G13971192) supported by the Semnan University Office of Vice President for Research and Technologysupported by Niroo Research Institute (NRI)。
文摘Increasing the temperature of photovoltaic systems reduces electrical efficiency,output power,as well as results in permanent damages in the long-term run.A new hybrid PV/PCM-Rib system with three different rib pitch ratios of Λ =4,Λ =2 and Λ =1 is investigated to reduce PV temperature and achieve uniform temperature distribution.A comprehensive two-dimensional model of the systems is developed and simulated with a fixed inclination angle of 30°.A parametric study is carried out to investigate the impact of ribs on different melting temperatures(50,40 and 30 ℃).According to the numerical results and the parametric analysis,using ribs shows better performance in temperature reduction for PCM with a lower melting temperature.By lowering the melting temperature of PCM from 50 to 30 ℃,the average temperature reduction of PV/PCM-Rib in the case of Λ =1 increases from 1.39% to 5.16% while the average melted PCM decreases from 20.5% to 7.59% after 240 min.It means that using ribs provides more solid PCM.It is also obtained that the electrical efficiency and output power show more increments at lower melting temperatures.
