Effect of manufacturing tolerances on Micro-CPV assemblies: A quantitative approach based on statistical modeling

Abstract

In micro-concentrator photovoltaics (micro-CPV) minimized components as cells (<1 × 1 mm²) and lenses are used, promising significant cost reductions through parallel manufacturing and reduced material volumes. However, tolerances, such as deviations from nominal size, geometry or position, impact module performance, especially for non-ideal alignment towards the sun. To study the interplay of different, independent tolerances and their effects on current generation, a comprehensive parameter study is practically not feasible, because of the vast number of possible combinations. In this work, we introduce a novel method for assessing tolerances by employing a Monte-Carlo approach to randomly select and combine tolerances in a cell-lens unit. It allows to identify relevant tolerances and quantitatively assess their influence on module performance, namely optical efficiency, and photocurrent as function of angle of incidence and, thus, acceptance angle. We apply the model to a micro-CPV module developed at Fraunhofer ISE and use tolerance distributions based on measurements. We find that the most crucial parameter is the position of the secondary optical element. Given the measured tolerance distributions, the acceptance angles for 90 % of the cases are above 0.5° for 10 % current loss. The developed approach is a crucial tool for identifying and assessing critical tolerances within a manufacturing line, facilitating techno-economic optimization of design and manufacturing processes.