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Evaluation of models to predict insolation on tilted surfacesAn empirical study was performed to evaluate the validity of various insolation models which employ either an isotropic or an anisotropic distribution approximation for sky light when predicting insolation on tilted surfaces. Data sets of measured hourly insolation values were obtained over a 6-month period using pyranometers which received diffuse and total solar radiation on a horizontal plane and total radiation on surfaces tilted toward the equator at 37 degrees and 60 degrees angles above the horizon. Data on the horizontal surfaces were used in the insolation models to predict insolation on the tilted surface; comparisons of measured vs calculated insolation on the tilted surface were examined to test the validity of the sky light approximations. It was found that the Liu-Jordan isotropic distribution model provides a good fit to empirical data under overcast skies but underestimates the amount of solar radiation incident on tilted surfaces under clear and partly cloudy conditions.
Document ID
19790069478
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Klucher, T. M.
(NASA Lewis Research Center Cleveland, Ohio, United States)
Date Acquired
August 9, 2013
Publication Date
January 1, 1979
Publication Information
Publication: Solar Energy
Volume: 23
Issue: 2, 19
Subject Category
Energy Production And Conversion
Accession Number
79A53491
Distribution Limits
Public
Copyright
Other

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