Daylight Availability Models for Global and Diffuse Horizontal Illuminance in Yongin, South Korea

This paper presents the daylight availability and models of global and diffuse horizontal illuminance in Korea. With 1-min interval, the illuminance data were being measured at the Kyung Hee University, located in the capital region of Korea. Daylight illuminance data were conducted from August 1, 2010 to July 31, 2012 during summer, autumn, winter and spring. Data analysis was carried out using hourly and cumulative frequency distribution of global and diffuse horizontal illuminance. The model of global and diffuse horizontal illuminance for the annual data were then presented for predicting global or diffuse horizontal illuminance for all sky conditions. It was found that the global and diffuse horizontal illuminance model were the lowest mean bias error and root mean square error under clear, partly cloudy and overcast sky. The new model can provide very good accuracy for the estimation of global and diffuse horizontal illuminance under clear, partly cloudy and overcast sky.