Investigation on the I-V characteristics of a high concentration, photovoltaic array

The aim of this study was to highlight the effects on the I-V characteristics of concentrator arrays due to mismatch between series-connected high concentration PV modules and between single junction cells within a module. The mismatch between cells was caused by a number of factors including: misalignment of optical elements and cells, uneven shading due to dust or delamination of the cell-secondary lens interface, degradation of the main Fresnel lens and non-uniform cell material parameters. Small amounts of mismatch that would go unnoticed at one-Sun insolation levels are vastly amplified at high concentration ratios. This paper reports on, and interprets the regular I-V measurements that were recorded over a period of two years under various conditions. The effect of bypass diodes on the module I-V curves is also investigated. The general characteristics of the measured resultant I-V curves are explained. The degradation of the PV concentrator modules over a period of two years is also confirmed from the I-V measurements.