High Efficiency Collectors For Solar Energy Applications: Analysis And Preliminary Experimental Results.

ABSTRACT Non metallic concentrators with tapered input sections are carefully investigated for solar energy applications. In addition, preliminary experimental results are compared with the numerical analysis in order to derive the basic criteria for their optimum design. !_._ INTRODUCTION Recently an increasing interest as been devoted to the design and the construction of a number of systems to efficiently collect and direct solar energy on a target for power conversion and illumination. In particular metallic parabolic concentrators have been largely studied [1]. Unfortunately, noticeable collecting properties are accompanied by some disadvantages, among which we can remind that they are bulky, expensive and with a low damage threshold for atmospheric conditions.The technological improvements in the production of optical fibers with a low absorption coefficient in spectral ranges different from the typical transmission windows for communication systems, has led to the use of dielectric collectors. These dielectric structures [2-5] present, when compared to metallic concentrators, the advantages of low cost, low weight, easy handling and high damage threshold with regards to atmospheric agents.In previous papers [6-8] we have reported preliminary results on the calculus of the coupling efficiency of a plane wave with a linearly tapered optical fiber. In particular in ref.7 we have shown that the minimization of the backreflecting losses is very critical in the optimum design of a tapered dielectric fiber with a high collection efficiency.In this communication a quite complete analysis of dielectric collectors with a tapered input section is presented together with some experimental results on the measurement of the collection efficiency.