Influences of Solar Incident Angle on Power Generation Efficiency of PV Modules under Field Conditions

Abstract

In this report, we examined influences of solar incident angle on the power generation efficiency of photovoltaic (PV) modules based on a measurement, during winter, at Kagoshima in Japan (31.570°N, 130.545°E). It was indicated that the power generation efficiency of PV modules deteriorates with time depending on the solar incident angle, and that there are cases where the power generation efficiency sharply drops if the incident angle exceeds 60° and the reflectance of cover glass exceeds 0.2. Such drop of power generation efficiency dependent on incident angle clearly appears at clear time when the proportion of direct components of solar radiation increases. Furthermore, it was pointed out that the average value of power generating efficiency during winter including all weather conditions produces differences of 10% or so, depending on the difference of average value during the period of incident angle.