光伏组件遮阴对光伏农业系统光环境及无花果产量影响分析

    Effects of photovoltaic module shading on internal light environment and fig (Ficus carica L.) yield in agrivoltaic systems

    • 摘要: 为保证光伏农业项目中的光伏发电效益,通常在农业用地上铺设大量的光伏组件。日间,光伏组件会遮挡太阳光线并在农业用地上产生较大的遮阴面积。为探明光伏组件遮阴对光伏农业系统内部光环境、阴影宽度、作物叶片光合特性和产量的影响,以江苏南京地区光伏组件下沿边缘距离地面垂直高度(以下简称光伏组件铺设高度)为2.5、3.2、3.9 m的光伏农业系统为试验对象,测试了光伏农业系统内部光伏阵列板下和板间种植区域的太阳辐射强度,计算分析了光伏组件遮阴形成的阴影宽度在1 a中的变化规律,研究了光伏阵列板间种植区域无花果的产量和叶片光合特性差异。结果表明,试验期间光伏阵列板间种植区域的采光率保持在55.4%~68.9%,是光伏阵列板下种植区域的2.1~3.3倍。在3种光伏组件铺设高度下,光伏阵列板间种植区域的采光率随着光伏组件铺设高度的增加而降低,光伏阵列板下种植区域相反。无花果全生育期内,光伏组件遮阴宽度随纬度、光伏组件铺设高度增大而增大。光伏组件遮阴导致各处理的无花果平均产量较露天对照减少了19.9%~48.9%,且叶片的光合特性能较好地反映各处理间的产量差异。较低的光伏组件铺设高度能有效提高无花果叶片的净光合速率和气孔导度,从而减轻光伏组件遮阴导致的光合抑制。综上,与光伏组件铺设高度为3.2和3.9 m的光伏农业系统相比,光伏组件铺设高度为2.5 m的光伏农业系统内部光环境更好,遮阴宽度更窄,能较好地降低无花果产量的减产幅度,在各地的光伏农业项目中具有一定的实用价值。

       

      Abstract: An agrivoltaic system has been one of the most promising potential sources of clean energy power in green agriculture. Some guidelines have been released to fully meet the requirement of the photovoltaic (PV) modules in agricultural projects. Particularly, it is the high demand for land utilization and mechanization of agricultural production in agrivoltaic systems, such as in Jiangsu and Yunnan provinces in China. Among them, the minimum installation height of PV modules has been standardized to maintain a specific tilt angle. However, the "prioritizing light over agriculture" can often occur during actual production. A large number of PV panels are typically installed on agricultural land in order to ensure the PV power generation in agrivoltaic projects. Furthermore, these PV panels can block the sunlight to form a considerable shading area on agricultural land during the day. This study aims to investigate the effects of shading from PV modules on the internal light environment, shading width, crop yield, and leaf photosynthetic characteristics in the agrivoltaic system. A series of tests were conducted on the agrivoltaic systems at the module installation heights (the vertical distance from the ground to the lower edge of the PV module) of 2.5, 3.2, and 3.9 m in Nanjing City. A systematic measurement was performed on the solar radiation intensity of the planting area under and between the panels inside the PV agricultural system. A quantitative analysis was implemented to calculate the annual variation patterns of the shading width formed by the PV panels. Additionally, there were significant differences in the yield and leaf photosynthetic characteristics of figs (Ficus carica L.) in the planted areas between the modules. The results indicated that the daylighting rate in the planted areas between the panels ranged from 55.4% to 68.9% during the testing period, which was 2.1 to 3.3 times that of the area under the panels. Specifically, the daylighting rate in the areas between the panels decreased at the three heights of PV module installation as the installation height increased, while the area under the panels showed the opposite trend. The shading width caused by the PV modules also increased with latitude and installation height throughout the entire growth period of the figs. Shading from the PV panels led to a reduction in average yield across treatments compared to the CK control, ranging from 19.9% to 48.9%. Additionally, the photosynthetic characteristics of the leaves effectively reflected the yield differences among treatments. A lower installation height of the PV panels can significantly enhance the net photosynthetic rate and stomatal conductance of fig leaves, thereby alleviating the photosynthetic suppression caused by shading. In summary, compared to agrivoltaic systems with panel heights of 3.2 m and 3.9 m, the system with a panel height of 2.5 m offered a better internal light environment and shorter shading width, effectively reducing the decline in fig yield and demonstrating practical value for photovoltaic agricultural projects in various regions.

       

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