Effects of tracking error on solar light concentration by a Fresnel lens

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Daniel, Noel L.
Cosby, Ronald M.
Issue Date
Thesis (M.S.)--Ball State University, 1977.
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The major objective of this study was to analytically determine the effects of small transverse solar tracking errors on the concentrated intensity profile generated by a 22-inch wide, f-number one, linear Fresnel model lens. Transverse tracking error is caused by the misalignment of the lens optic axis and the center of the sun in a direction perpendicular to the lens optic axis. The analytical method consisted of extending an earlier theoretical model developed by Cosby3 in which the solar disk was perfectly tracked; thus the tracking error problem is treated as a perturbation of the basic theory. Data was obtained using extensive computer calculations.Results indicated that in the presence of transverse tracking error, lens serrations (upper half serrations) on the same side of the lens optic axis as the sun differ significantly from the lens serrations (lower half serrations) on the opposite side of the lens optic axis in their concentration characteristics. Incident angles of sunlight are greater for upper half serrations causing greater angles of refraction at the second surface. The peak concentration ratio values are observed to shift in the negative intercept direction in a linear relationship with tracking error angle. It was observed that the 90% target width monotonically increased, e.g., by 100% and 700% for transverse tracking errors of 1/2° and 2-1/2°, respectively. It is concluded that the dominant cause for the 90% target width increase is the intensity profile shift itself. Some lesser influence results from increasing intensity profile skewness and profile broadening for IR wavelengths caused by greater IR refraction with increased transverse tracking error.Ball State UniversityMuncie, IN 47306