Surface efficiency assessment of the spherical segment solar collector

Abstract

A model is set up in this paper to calculate the surface utilization of a spherical segment solar collector. This study is based on a method derived from a previous analytical model developed under the Crosbyton Solar Power Project by Billy C. Brock as part of his PhD dissertation. His method, however, assumed constant solar radiation throughout the year. As an extension of Brock's work, his model will be modified in this paper by utilizing measured hourly solar insolation data Barstow, CA. Given the solar collector's geometrical parameters and its geographic location, the relative efficiency of a specific portion of collector surface can be computed on an annual basis.

Consideration has been given in this analysis to shading, multiple bounces, spillage, and other factors affecting the efficiency performance of the solar collector. An alternative to the 60° rim angle collector, a shallow collector with a movable iris, has also been analyzed for its collection efficiency.

This analysis has been performed by using computer programs. The assumption is made that all the incoming sun rays that strike the concentrator surface are captured by the receiver. It is also assumed that the concentrator's reflecting surface is a perfect spherical segment and that the receiver is perfectly aligned. In other words, this collector efficiency analysis is for the ideal case and is independent of other system components.