Does micro-scaling of CPV modules improve efficiency? A cell-to-module performance analysis

The actual trend of Concentrator PhotoVoltaic (CPV) development is going into micro-scaled CPV modules (micro-CPV) to optimize the balance between cost and efficiency. The compactness and high efficiency of modules constitute distinct advantages for solar farms or residential applications but the module efficiency can still be improved. While the cell efficiency is higher than 40%, the module efficiency is still below 35%. Based on a complete analysis of the Cell-To-Module (CTM) loss chain in micro-CPV, this article aims to question if the micro-scaling of CPV modules tends to improve their efficiency. Optical, mechanical and electrical losses are identified and analyzed according to data reported in the literature. It appears that the same loss mechanisms are identified in CPV and micro-CPV CTM but their impact order differs on a few points. The surface reflections and bulk absorption are the most important losses in both cases. Then, the surface shape quality which is quantified by either roughness or slope errors varies a lot as function of the manufacturing processes and module technology. These two losses have to be determined specifically for each concentrator. With the size reduction of modules, the losses due to mechanical misalignment become non-negligible, pushing a micro-CPV assembly into tighter mechanical tolerances. In contrast, the non-uniform light profile which is not yet well known for micro-CPV, seems to be a less impacting loss mechanism. The CTM ratio, which sums every loss mechanisms, goes from 71% to 86% for micro-CPV modules while stays between 65% and 75% for CPV modules. Finally, with an improvement of manufacturing accuracy by the implementation of micro-electronics assembly processes, the micro-scaling of CPV modules could increase the CTM efficiency without added manufacturing costs.