Unified methodology for determining CTM ratios: Systematic prediction of module power
The power output and efficiency of a crystalline silicon PV module is a highly relevant quantity to evaluate novel cell, material and design technologies. It is therefore necessary to develop a full understanding of the different factors that impact the cell-to-module ratio. The purpose of this work is to demonstrate a unified methodology for predicting module power and efficiency from material and geometry data for several cell, interconnection and module designs. The methodology consists of analyzing photovoltaic inactive module areas, optical effects such as reflection, absorption and electrical losses. For a selection of efficiency impacting factors we show experimental results to demonstrate their influence on module efficiency and module power. The model has been validated by measurements on an H-patterned multi-crystalline 60-cell module showing a deviation in module power of only 1%, a value well within the flasher measurement uncertainty. For a 60-cell-module with pseudo-square monocrystalline solar cells with 19.9% efficiency we calculate absorption losses for different encapsulants in the range of 1.3 to 5.3 W. The power gain for the investigated backside materials is found to be in the range between 4.5 and 6.7 W.