Created by E.Ö., SUPSI, on 27.11.2025
Photovoltaic modules installed in cold climates or at high altitudes are exposed to extreme mechanical and thermo-mechanical stresses. Low temperatures and rapid temperature fluctuations influence solar cells, polymeric materials – encapsulant and backsheet – and also electrical interconnections, cable insulation, and connectors. While low ambient temperatures generally slow chemical ageing processes [1], they significantly increase the risk of physical and mechanical failure modes.
Microcracking and Damage to Silicon Cells and Interconnections
At low temperatures, polymeric components such as encapsulants and backsheets enter a glassy, rigid state where molecular mobility is largely frozen [2]. EVA begins to lose its elasticity when approaching its glass-transition range around −20 °C and becomes significantly more brittle as temperatures approach −30 °C. EPE, which combines layers of EVA and POE, shows two transition behaviors, changing mechanical properties beginning around −20 °C and again near −40 °C. POE remains flexible to considerably lower temperatures, with transitions beginning near −40 °C and mechanical stability retained even below this point (Figure 1) [3]. Once the encapsulant stiffens, the laminate loses its ability to distribute strain, resulting in localized stress concentration in the brittle silicon cells [2]. Under these conditions, microcracks form more easily (Figure 1), particularly during uneven snow load events or when sudden temperature swings (thermal cycling) occur. These microcracks may not be visible immediately but can propagate over time, reducing active cell area, increasing series resistance, and potentially leading to hotspots and measurable performance losses.
Figure 1: (left) Curves resulting from tensile stress tests: Stress at 10% elongation of encapsulants at varying temperatures. (right) EL images of full-size Glass/EVA/Backsheet modules after the Mechanical Load (ML) test sequences at -40C and +25C. Difference in severeness of cell cracking is visible [3].
Backsheet Damages
Backsheets, especially polypropylene-based structures, also show pronounced ductile–brittle transitions. At temperatures near or below the glass-transition region (around −10 °C to 0 °C for PP), the material becomes brittle and prone to cracking [4]. Mechanical stresses, snow shedding, or thermal cycling can easily initiate tears or cracks that compromise electrical insulation and allow moisture-ingress. Over time, these cracks can propagate, leading to insulation failure or catastrophic module breakdown.
Delamination
Delamination is another key risk under low-temperature and thermal-cycling conditions. Differential thermal expansion between polymeric layers and stiffer materials such as glass, copper, or aluminum induces shear stress at interfaces [5]. As adhesion weakens and cracks form, moisture ingress becomes more likely, which further accelerates degradation and may initiate corrosion or cell metallization damage.
Mitigation Strategies
- Use encapsulant materials designed for cold climates, favouring those with lower glass-transition temperatures (e.g., POE, EPE) that retain flexibility at sub-zero conditions.
- Select backsheets and polymer components rated for sub-zero and high-altitude operation to avoid brittle-ductile transitions and cracking during thermal cycling.
- Verify material specifications (Tg, modulus–temperature curves, low-temperature tensile behavior) instead of relying solely on module certification labels.
- Choose modules with high mechanical load ratings, including those tested under IEC 62938 non-uniform snow load conditions, which better represent real-world high-latitude stresses.
- Prefer multi-wire cell interconnections, which distribute mechanical loads more evenly and reduce ribbon fatigue under thermal cycling compared to wide busbars [1].
- Use low-temperature-rated and UV-resistant cables, junction boxes, and connectors to prevent cracking, embrittlement, or seal failures.
- Follow cold-weather installation practices, avoiding bending or stressing cables.
- Design systems to avoid thermal shock, minimizing conditions that cause rapid cooling or heating (e.g., avoid sudden shading, exposed module corners, or configurations prone to cold-air pooling).
- Ensure proper mechanical support and mounting design, reducing stress on the laminate during snow loads and thermal expansion/contraction cycles.
References
[1] E. Ozkalay, H. Quest, and A. Gassner, et al., “Three decades, three climates: environmental and material impacts on the long-term reliability of photovoltaic modules,” EES Sol., vol. 1, pp. 580–599, 2025. doi: 10.1039/d4el00040d.
[2] G. Friesen, L. Micheli, and G. C. Eder, et al., Optimisation of Photovoltaic Systems for Different Climates. IEA PVPS Task 13 Report, 2024. doi: 10.69766/QSYC8858.
[3] A. Gassner, G. C. Eder, E. Özkalay, G. Friesen, M. Feichtner and V.‑M. Archodoulaki, “Enhanced mechanical load testing of photovoltaic modules for cold and snowy climates,” EES Solar, vol. Advance Article, 2025. doi:10.1039/D5EL00125K.
[4] G. Oreski, G. C. Eder, Y. Voronko, A. Omazic, L. Neumaier, W. Mühleisen, G. Ujvari, R. Ebner, and M. Edler, “Performance of PV modules using co-extruded backsheets based on polypropylene,” Solar Energy Materials and Solar Cells, vol. 223, 2021, Art. no. 110976. doi: 10.1016/j.solmat.2021.110976.
[5] M. Aghaei et al., “Review of degradation and failure phenomena in photovoltaic modules,” Renew. Sustain. Energy Rev., vol. 159, 2022, Art. no. 112160. doi: 10.1016/j.rser.2022.112160.
