MODELING THE SOLAR IRRADIATION ON FLAT-PLATE COLLECTORS AUGMENTED WITH PLANAR REFLECTORS

An analytical model has been developed and used to determine solar irr adiation on flat collectors augmented with planar reflectors. The mode l uses measured insolation data from the NREL National Solar Radiation Data Base. In addition the model accounts for direct and reflected co mponents of beam, diffuse and ground reflected insolation, considers f inite length systems, accounts for shading of the collector by the ref lector, and considers different configurations of the reflector relati ve to the collector. Thus the model represents an extension and refine ment of many previous models. Computer simulations have been carried o ut over different time spans to assess the effects of including these features. In general the addition of reflectors enhances the radiation received by the collector. Reflected beam radiation is the major cont ributor to the enhancement, although reflected sky diffuse and ground reflected radiation can be significant in many instances. To optimize effectively the design of the system with respect to selecting tilt an gles and specifying a reflector-above or below-collector configuration requires proper modeling of the energy received by the collector syst em. Finite length analysis used in the model enables the optimization of reflector size relative to that of the collector. The model present ed can be the basis of an analytical design tool for optimizing the de sign of a variety of reflector-enhanced solar energy collection system s.