Optics of solar concentrators Part I: Theoretical models of light collection

A review of the theoretical models of light collection in solar concentrators, developed by the author in the last years, is here reported together with new advancements of the theoretical analysis wh ich have led to the introduction of new optical concepts and to the definition of new optical quantities. For som e of them a match was found with electrical quantities. Solar concentrators are regarded as generic optical elements whose reflectance, absorbance and transmittance properties are exp ressed with respect to different ways of irrad iation. They are studied under collimated or d iffuse light, under local or integral irradiation, including that in which light direction is reversed, that is directed from the exit towards the entrance aperture. All the results have been obtained applying two optical concepts: the reversibility princip le and the efficiency of transmission through the solar concentrator of an elemental beam. This theoretical investigation of solar concentrators improves the knowledge of their optical properties, potentially expands the field of their applications and opens new perspectives to the methods of characterization.