Current-voltage characteristics of high-concentration, photovoltaic arrays

The current-voltage (I-V) characteristics of photovoltaic (PV) systems have always been a good indicator of the overall performance of a system. The aim of this paper is to give an overview and elucidate the use of the I-V characteristics of concentrator PV (CPV) modules and arrays as an important diagnostic tool to identify factors that lower a system's performance and the types of mismatch that exist between series-connected single-junction cells within a module. Possible causes for mismatch between cells include factors such as; misalignment of optical elements and cells, nonuniform cell material parameters, uneven cell illumination due to dew, dust or degradation of the secondary and main optical elements. The different types of mismatch typically found in CPV are categorized and their effects on the resultant module I-V curves are discussed and shown. The effect of bypass diodes on the module's I-V curves is also illustrated. This paper also reports on, and interprets I-V measurements that were recorded for a commercially available point-focus concentrator module under various real outdoor conditions. Copyright (C) 2004 John Wiley Sons, Ltd.