STUDIES ON THE MEASUREMENTS OF SOLAR RADIATION
This report presents a preliminary analysis of the data obtained from a comparative study of cosine and tilt effect in a sample of eight Kipp and Zonen CM-5 pyranometers. The study was made using the National Institute of Agricultural Engineering's Spatial Response Goniometer. The results revealed that the effect of tilting pyranometers is less than +- 0.3 % throughout the full range of tilt angles, though these results were obtained for relatively low levels of irradiance (+-150 wm**2) and one would expect error to increase with incidence irradiance (see Gillett, 1981). Errors in the departure from true cosine response are however much greater in magnitude and are thus much more serious. The situation is complicated by the lack of azimuthal symmetry in the detector, which reveals an azimuthal as well as an elevation dependence of departure from true cosine response. Probably even more important however is the variation in the cosine behaviour from instrument to instrument which was revealed by the results and these have important implications for indoor and outdoor calibrations. A brief analysis of these implications is presented here.
Bibliographic Reference: EUR 9259 EN (1984) MF, 108 P., BFR 240, BLOW-UP COPY BFR 540, EUROFFICE, LUXEMBOURG, POB 1003
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Record Number: 1989122099500 / Last updated on: 1987-01-01
Available languages: en