DESIGN PROCEDURE OF V-TROUGH CAVITIES FOR PHOTOVOLTAIC SYSTEMS

The combination of photovoltaic (PV) systems with V-trough cavities ha s been identified as an attractive option to reduce, in the short time scale, the prices of the PV electrical energy. In places of good radi ation level, the output energy of these devices can be almost doubled, compared to PV flat-plate fixed systems. Additionally, V-trough cavit ies are simple to manufacture and can be used with conventional (1-sun ) solar cells. In this work we present a design procedure for V-trough cavities used in combination with PV generators. The main design requ irements are: uniform illumination on the plane of the PV module, with in a finite interval of incidence angles; minimum cost of energy; and heat dissipation by natural, passive means. The V-trough cavities depe nd on two parameters. We obtain a first analytical relation between th e concentration ratio (C) and the V-trough angle (psi) for concentrato rs with uniform illumination at the absorber. The region of minimum co st of the V-trough PV ensemble yields a second relation. Then, a uniqu e pair of cavity parameters, satisfying the above criteria, is found. A design example of a V-trough cavity for the city of Recfie, PE, Braz il, is presented. (C) 1998 John Wiley & Sons, Ltd.