Studies on Measurement and Estimation of Solar Radiation : 1st Report, Process and Analysis of Measurements of Solar Radiation at Kitami Institute of Technology

概要

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Measurements of solar radiation in the past five years from 1978 to 1982 at Kitami Institute of Technology were processed and analyzed, and it was then proved that there was a high correlation between the total solar radiation on a horizontal surface and the direct solar radiation on a normal surface to incidence which were both normalized by dividing by extraterrestrial solar radiation. From the frequency distribution of a number of days which was obtained by grading the daily total radiation on a horizontal surface every 2 MJ/m^2d of intensity, a limit value of the direct solar radiation on a normal was introduced in order to define a clear day on which it was possible to use solar energy and a cloudy day on which it was impossible to use solar energy. According to the results of data analysis, the limit value of the direct radiation on a normal, H^^-*_<ND'> on the borderline between such clear and cloudy days as above was about 3 MJ/m^2d, and the limit value of the total radiation on a horizontal, H*_<HT>, which corresponded to H^^-*_<ND> and the ratio of clear days to total days could be obtained as a monthly average over five years.