Energy and economic comparison of three optical systems adopted in a point-focus CPV system

Abstract

The concentrating photovoltaic (CPV) systems allow good results for generation of clean energy at competitive costs, but a careful selection of the optical system is essential to obtain energy and economic advantages. Hence, three different point-focus optics (parabolic mirror, spherical mirror and a commonly used Fresnel lens) characterized by same dimensions are compared in this paper from energy and economic point of view in order to identify the most convenient in terms of unit cost of electrical power. The optical concentration factor, the maximum values of triple-junction (TJ) cell electrical power and temperature are experimentally measured for each optical system, and successively, the unit cost of electrical power is calculated. The parabolic mirror results the least convenient because it guarantees almost the same performances of a spherical optics but with costs of about 2.7 times higher than it. The Fresnel lens presents a value of the unit cost of electrical power near to the spherical mirror, but its much lower optical efficiency implies a necessary area for the CPV plant about three times larger. Moreover, a forecast of the increase in the CPV plant power capacity in Italy and the consequent decrease in the unit cost of electrical power in two possible scenarios, optimistic and pessimistic, is realized. A reduction of the unit cost of electrical power, between 13 and 30%, is expected for the CPV systems.