Abstract
For the application of solar energy to heat engineering, the data of solar radiation measured over five years from 1978 to 1982 at Kitami Institute of Technology were processed and analyzed. Based on all the measured data a correlation equation which could be mployed to estimate the normal-direct solar radiation from the horizontal-total solar radiation was introduced. The daily horizontal total radiation was classified into a scale rank by every 2 MJ/m2d of intensity, and total radiation on a tilted surface with any angle of inclination and direction in every scale rank was calculated by means of a precise calculation method using hourly values of the measurements. At the same time, the total solar radiation on a tilted surface, i.e., the inclined-total radiation, was also calculated from the averaged values of the horizontal-total radiation and normal-direct radiation. Subsequently, it was proved that in comparison with the accurate value obtained by the precise calculation method, the inclined-total radiation could be caluclated correctly enough by both the monthly average horizontal total radiation and the monthly average normal-direct radiation with any distribution weight.
