A COMPARATIVE-STUDY OF OPTICAL DESIGNS AND SOLAR FLUX CONCENTRATING CHARACTERISTICS OF A LINEAR FRESNEL REFLECTOR SOLAR CONCENTRATOR WITH TUBULAR ABSORBER

This paper presents a comparative study of the optical designs and sol ar flux concentrating characteristics of two designs of the linear Fre snel reflector solar concentrator (LFRSC) derived using two different approaches for the tubular absorber configuration. The concentrator us es long plane mirror elements suitably positioned on a flat base so th at each mirror element reflects solar radiation on to an absorber plac ed in the focal zone along the length of the concentrator. In one appr oach the concentrator is generated from the prespecified diameter of t he absorber, while in the second approach, using a prespecified equal width of the mirror elements, an appropriate diameter of the tubular a bsorber is determined for the desired size of the concentrator. For ea ch concentrator design, the distribution of the local concentration ra tio (LCR) on the surface of the tubular absorber has been determined u sing the ray trace technique, taking into consideration both the unifo rm intensity on the solar disc and the solar limb darkening effect (no n-uniform intensity). The surface area factor aspect of each concentra tor design, a measure of the cost of reflective surface used in the co ncentrator, has also been studied. Results of some numerical calculati ons carried out to illustrate the performance of the concentrators are graphically presented and compared.