Variations in the spectral distribution of daylight at various geographical locations on the Earth's surface
Three locations, Barrow, Alaska at 71/sup 0/N, Rockville, Maryland at 39/sup 0/N and the Pacific end of the Panama Canal at 9/sup 0/N are the sites used for solar radiation data comparisons in this paper. Data collected by precision pyranometers over the years 1968 to 1974 show, with great clarity, that one cannot compute the daily insolation on a horizontal surface with variations of less than 50% from some mean value. The spectral quality of daylight is not the same at all places, nor is the rate of change in the spectral quality the same at all locations. The greatest variations in the spectral quality occur in the peak response region for silicon, 600 to 800 nm. The blue, 400 to 500 nm, also shows large variations, but, like the red bands, most of these variations are due to local atmospheric conditions. Of the three sites, Rockville shows the greatest amount of variation from year to year, as well as during the year. Because of the large variability in daily totals at Rockville, it appears that it will be necessary to monitor daily amounts of solar radiation to evaluate the performance of heating and cooling systems for buildings using solar energy in this area. One other trend has also been noted in Rockville: a small but steady decline in the amount of solar energy falling on a horizontal surface. Between 1971 and 1974 the decline in energy was approximately 4.5%.
- Research Organization:
- Smithsonian Radiation Biology Lab., Rockville, MD
- OSTI ID:
- 7327210
- Journal Information:
- Sol. Energy; (United States), Journal Name: Sol. Energy; (United States) Vol. 19:1; ISSN SRENA
- Country of Publication:
- United States
- Language:
- English
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