Effects of Irradiance Distribution Unevenness on the Ohmic Losses of CPV Receivers

Concentrating photovoltaic (CPV) systems use solar collectors to focus the incoming solar radiation onto PV receivers equipped with small area solar cells. The irradiance profile at the PV receiver plane is strongly dependent on the concentrator architecture and has deep influence on the performances of the solar cells. In this work we will describe an approach matching ray-tracing simulations and circuit analysis to assess the ohmic losses of the PV receiver operating under uneven illumination. In this investigation we considered three types of solar concentrator optics (Fresnel lens, parabolic mirror and freeform mirror) having different flux distribution in the focal region. The optical simulations have been carried out taking into account the real radial distribution (sunshape) of the incident solar energy. The irradiance profile at the PV cells plane has then been used as a map for the photo-generated current to be collected and drawn from the devices. The cells have been binned into a grid of generators connected between them by a resistive network simulating the metal contacts and the semiconductor layers. The current-voltage characteristics of real solar cells has been measured and modeled by an array of diodes connected in parallel to each generator. The nonlinear circuit has been solved by a simulation program with integrated circuit emphasis (SPICE)