2002 年 67 巻 557 号 p. 33-39
The sky radiance distribution changes in accordance with the sky condition, such as solar position, weather, cloud conditions and so on. This paper proposes a method of dividing the global solar irradiance into the direct diffuse irradiance, and this method is based on the data of the sky radiance distribution measured by Sky Scanner. The proposed solar irradiance model : Δζ-based Sky Irradiance Model, is that irradiance from the high-radiant area around the sun is added to the direct solar irradiance value. Δζ is the angle distance from the center of the sun to the end of direct irradiance area. From the results of study on solar irradiance on tilted surfaces, Δζ value is recommended 50 degree. In this paper, we propose the equations that estimate the Δζ-Based Sky Irradiance from the global solar irradiance, and verified its accuracy.