Optical Design of a 500 x PV Solar Concentrator with 1 Degree Field of View

In this paper we present our first results regarding the development of a Concentrating Photovoltaic (CPV) systems based on a classical Cassegrain optical design and a beam homogenizer. The system is characterized by a geometrical concentration factor (Cgeo) of around 500X. The optical design has been developed in order to obtain a 10 mm wide square image. Particular attention has been devoted to the homogenizer and to its building materials in order to reduce the cost and the thermal effects caused by concentrated radiation. Moreover the optical design has been specifically chosen to produce a Sun square image that optimizes the pv cell coupling. The field of view (FOV) of the designed concentrator is of +/- 0.5 degrees. The primary mirror has a 220 mm wide square aperture and a focal length of 80 mm (f/0.4). The secondary mirror is hyperbolic with a magnification of 6X that lead to a 4 mm diameter Sun image. In order to obtain a 10 mm wide square image, we used a total internal reflection (TIR) homogenizer. In this way the focal plane may host a typical commercial triple junction PV receiver assembly with a 10 mm squared active area. Cells of different sizes may be easily fitted by changing the exit side dimension of the homogenizer. The optical design has been optimized and it is ready for the test and optical characterization