A comparative study of optical designs and solar flux concentrating characteristics of a linear fresnel reflector solar concentrator with tubular absorber

Abstract

This paper presents a comparative study of the optical designs and solar flux concentrating characteristics of two designs of the linear Fresnel reflector solar concentrator (LFRSC) derived using two different approaches for the tubular absorber configuration. The concentrator uses long plane mirror elements suitably positioned on a flat base so that each mirror element reflects solar radiation on to an absorber placed in the focal zone along the length of the concentrator. In one approach the concentrator is generated from the prespecified diameter of the absorber, while in the second approach, using a prespecified equal width of the mirror elements, an appropriate diameter of the tubular absorber is determined for the desired size of the concentrator. For each concentrator design, the distribution of the local concentration ratio (LCR) on the surface of the tubular absorber has been determined using the ray trace technique, taking into consideration both the uniform intensity on the solar disc and the solar limb darkening effect (non-uniform intensity). The surface area factor aspect of each concentrator design, a measure of the cost of reflective surface used in the concentrator, has also been studied. Results of some numerical calculations carried out to illustrate the performance of the concentrators are graphically presented and compared.