Analysis of a Combined Thermal-Photovoltaic Solar System Based on the Spherical Reflector/Tracking Absorber Concentrator

Abstract

The Stationary Reflector/Tracking Absorber (SRTA) solar system, which has been described and used in the past for heat and steam generation, is analyzed with the aim of combining with it photovoltaic (PV) generation. The light concentration function along a finite size absorber is calculated. The areas of the absorber which may be unilluminated during parts of the day are determined. It is shown that for a system to be useful for PV generation, the absorber must turn one side toward the outside perimeter of the reflector while tracking, and its diameter must increase with the distance from the reflector. A special two-section polygonal cone is shown to give an approximately constant light concentration along most of its length, and can therefore be used with an array of solar cells of one type only. Such a design also contributes to an incidence angle of the reflected light rays on the absorber surface that is closer to normal than with a cylindrical shape. It is also shown that the length of a real absorber is always shorter than that of an ideal line absorber of zero radius, and that only about 50 percent of the area should be covered with cells, with the rest to be used for thermal absorption and heat generation only.