Reflection characteristics at large incident angles with reference to solar bowl

Abstract

A computer code was developed for the Crosbyton Solar Power Project to calculate the optical concentration along the receiver of the Crosbyton Solar Bowl. The predicted values have been in agreement with the observed data during the middle period of the solar day. However, optical flux distributions along the receiver in the mornings and afternoons have been found to be approximately 8 percent below what was predicted for the system. The purpose for this investigation is to identify the cause(s) for this discrepancy.

To account for these discrepancies, a set of simple experiments were performed in the lab using the same kind of mirrors which are mounted on the solar bowl. The data analysis and calculations show that a significant quantity of this discrepancy is due to the focusing defect caused by two properties of back surface reflecting mirrors. They are surface defects introduced during the manufacturing process, and internal reflections between the glass/air interface and the back reflecting surface. These properties have significant effect at large incidence angles.