太阳辐射长期变化对固定式并网光伏电站最佳倾角的影响分析——以北京地区为例
Impacts of the Solar Radiation Variation on the Optimum Tilted Angle for the Fixed Grid Connected Solar PV Array—— A Case Study in Beijing
中文摘要：
最佳倾角是固定式并网光伏发电的关键设计参数之一，不仅与当地经纬度有关，还受气象条件的直接影响。以北京地区为例，在分析地面太阳辐射（总辐射、直接辐射、散射辐射、直射比和散射比）长期变化的基础上，计算分析固定式并网光伏电站最佳倾角的变化。结果表明：北京地区近55a的总辐射呈下降趋势，其中水平面直接辐射的下降是主要的，散射辐射下降不明显，相应地，直射比明显降低，散射比则明显增加；最佳倾角总体亦呈下降趋势，近5a比20世纪60年代下降了2°，从计算方法来看，这种下降趋势主要由直射比的降低所导致，而直射比则受大气环境的影响。因此，在光伏电站的设计和建设过程中，应充分关注大气环境的变化及其对太阳辐射的影响，选择合理的最佳倾角。
中文关键词：
总辐射，直射比，最佳倾角，大气环境
KeyWords：
global radiation, direct irradiation ratio, optimum tilted angle, atmospheric condition
Abstract：
As one of the key design parameters for the fixed grid connected solar PV array, the optimum tilted angle is not only related with the geographic location, but also directly affected by atmospheric conditions. On the basis of long-term variations of the observed solar radiation (global radiation, direct horizontal radiation, diffuse radiation, direct irradiation ratio and diffuse irradiation ratio) in Beijing, the variations of the optimum tilted angle for the fixed grid connected solar PV array are calculated and analyzed in this paper. It is shown that: 1) there was a declining tendency in the global radiation during the recent 55 years, among various radiations, the decrease in the direct horizontal radiation took the main proportion while the decline in the diffuse radiation was not obvious, these lead to the significant decrease in the direct irradiation ratio while the obvious increase in the diffuse irradiation ratio. 2) The long-term optimum tilted angle variation also shows a downtrend. Compared with the optimum tilted angle in the 1960s, it falls by 2 degrees in the recent 5 years. It is presumable based on the calculation that the declining tendency in the optimum tilted angle is mainly caused by the significant decrease in the direct irradiation ratio, which is intensively affected by the atmospheric conditions. Therefore, the variations of atmospheric condition and its impacts on the solar radiation should be paid more attention for determining the optimum tilted angle in design and construction of the photovoltaic power plants.