Characterization of the spatial distribution of irradiance and spectrum in concentrating photovoltaic systems and their effect on multi‐junction solar cells

Abstract

The irradiance and spectral distribution cast on the cell by a concentrating photovoltaic system, typically made up of a primary Fresnel lens and a secondary stage optical element, is dependent on many factors, and these distributions in turn influence the electrical performance of the cell. In this paper, the effect of spatial and spectral non-uniform irradiance distribution on multi-junction solar cell performance was analyzed using an integrated approach. Irradiance and spectral distributions were obtained by means of ray-tracing simulation and by direct imaging at a range of cell-to-lens distances. At the same positions, I-V curves were measured and compared in order to evaluate non-uniformity effects on cell performance. The procedure was applied to three different optical systems comprised a Fresnel lens with a secondary optical element consisting of either a pyramid, a dome, or a bare cell.

Tuning the current ratio of a CPV system to maximize the energy harvesting in a particular location

“…Changes on the silicone refractive index are, in practice, equivalent to variation on the system focal distance. A detailed experimental analysis of the effects of these variations combined with different spectral distribution can be found in reference [23] where the short-circuit current and the fill factor were reported to be the most sensitive parameters. FIGURE 1.…”

Assessment of the optical efficiency of a primary lens to be used in a CPV system

“…On the other side, we find characteristics that affect the spectral and spatial irradiance distribution at the lens focus: chromatic aberration, the width of the Fresnel grooves, low-angle scattering due to surface quality, lack of flatness or other manufacturing errors, and temperature effects. These characteristics affect where the light goes (that is, how well the lens acts as a concentrator) and therefore their effect on overall system optical efficiency is, to a greater or lesser degree, dependent of the receiver and cell properties, from the simply area of the device (which determines the geometric concentration ratio) to more complex technological parameters such as the distribution of the series resistance throughout the device (Espinet, 2012;Kurtz and O'Neill, 1996;Victoria et al, 2013) (see Fig. 1).…”

Understanding causes and effects of non-uniform light distributions on multi-junction solar cells: Procedures for estimating efficiency losses

“…Experimental analyses were carried out by several authors to determine the influence of non-uniform irradiance distributions on the cell caused at different primary-to-receiver distances by either maintaining spectrum and irradiance conditions constant (5-7) or varying them (8). MJ devices are usually designed to be current matched (i.e., the ratio between subcell currents is 1) under AM1.5D spectrum.…”