Analysis of Hotspots in Half Cell Modules Undetected by Current Test Standards

Abstract

Today, hotspots are a major source of failure for photovoltaic modules in the field. Modules based on half-cut solar cells are an attractive pathway to reduce cell-to-module losses and are projected to have a 40% market share by 2028. However, the current standard for module testing IEC 61215-2 can leave critical hotspots undetected in such a module configuration. In this paper, the hotspot effect of half-cell modules using parallel connected cell substrings is studied in comparison with conventional full-cell modules. Significant hotspots are induced in both half- and full-cell modules, when suffering current mismatch, in this case induced by partial shading. When shaded by the same area, the hotspot temperature of the cell in a half-cell module is 19 °C lower than the full-cell module in this experimental work. Critically, multiple unshaded weak cells are found to dissipate heat when the parallel connected substring is shaded. In an experimental situation with a total shading ratio of only 4%, we measure hotspots of over 90 °C—a situation that can occur in the field due to uncontrolled plant growth and bird droppings.

Reference Link
J. Qian, C. E. Clement, M. Ernst, Y. S. Khoo, A. Thomson, and A. Blakers, “Analysis of Hotspots in Half Cell Modules Undetected by Current Test Standards,” IEEE J. Photovoltaics, 1–7 (2019). https://doi.org/10.1109/JPHOTOV.2019.2898209
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