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Damp Heat

The damp heat test simulates long-term degradation and failure modes that are typical in high temperatures and high humidity conditions. Moisture and heat can weaken the materials binding the PV module together. When the adhesiveness of these materials weakens due to low-quality components and/or substandard lamination processes, moisture can enter the laminate and corrode internal materials. The result is performance loss and safety issues.

Why Testing Matters

Certification testing doesn’t comprehensively assess the risk of delamination in the field. Asset owners may suffer financial losses when PV modules delaminate – even when they’re under warranty.

A recent class-action lawsuit, Ziccarello v. Sanyo Energy (U.S.A.) Corp., awarded damages to some PV asset owners with Sanyo PV modules susceptible to delamination over time. Asset owners waited more than three years for a settlement to be reached.

Only the most severe cases of delamination were eligible for replacement or financial relief. However, the delamination observed in PV modules not eligible for replacement is still likely to result in significant power loss over time and potential safety risks.

Asset owners with underperforming, delaminated modules will not be reimbursed for system underperformance – and only the most severely affected asset owners will receive any form of financial relief.
Eligible for Replacement

Delamination was so extreme that the module began to severely corrode.

Not Eligible for Replacement

Without publicly available rationale, the PV module was deemed not eligible for replacement despite indications of significant delamination, including the ingress of dirt and moisture between the glass and the frame.

Frame Adhesive
Glass Coating
Front Encapsulant
Back Encapsulant
Cells, Cell Interconnects, Flux
Junction Box, Connectors, Pottant, Adhesive

Materials Assessed

  • Cells
  • Encapsulant
  • Glass Coating
  • Junction Box
  • Cell Interconnects
  • Connectors
  • Backsheet
  • Junction Box Pottant
  • Junction Box Adhesive
  • Flux
  • Frame Adhesive

These materials all play a role in protecting the PV module from environmental elements and ensuring that all components are firmly bonded together and resistant to corrosion.

Explore PVEL’s Test Methodology

Key Takeaways

Click through the key takeaways below.

50% of BOMs tested for Damp Heat achieved top-performing results

There was a wide range of performance in DH: 50% of BOMs achieved top-performing results after the full test sequence. One BOM degraded by 54%, the worst DH result in PVEL history.

67% decrease in BOMs requiring boron-oxygen stabilization

Only 23% of top-performing BOMs required boron-oxygen stabilization to achieve <2% degradation versus 70% in 2021. This reduction in destabilization makes DH test results much easier for buyers to interpret. These improvements were driven by the increased use of gallium dopants during crystalline cell manufacturing.

Components impact module reliability

Several BOMs with concerning results used near-identical materials to Top Performers from the same manufacturers. This proves that small component changes can severely impact reliability.

Test Procedure

DH subjects modules to a constant 85°C and 85% relative humidity in an environmental chamber for two periods of 1,000 hours. This test doubles the duration required for IEC certification to identify additional module failure modes where the combination of high heat and intense moisture stresses the PV module layers.

Environments with high temperatures and no current can lead to a destabilization of PV cell boron-oxygen (BO) complexes. This leads to power loss in some boron-doped PERC cells, a phenomenon that is not yet well-understood in the field. To reverse this effect PVEL conducts a BO stabilization process at the end of the DH test sequence. This stabilization step helps separate BO-induced power loss from traditional DH-induced power loss.

Power Degradation of Each Model Type

Historical DH2000
2022 DH2000
Historical Post-BO Stabilization
2022 Post-BO Stabilization

See Top

See Top Performers

Reading DH Test Results

Modules susceptible to degradation from damp heat suffer from substantial power loss and corrosion, which appear as dark areas around cell perimeters and along cell interconnects in EL images.

Not shown here: a checkerboarding effect is usually apparent in EL images of modules with BO-induced destabilization.

Power Degradation After
1,000 hours: 2.3%
2,000 hours: 12.8%
Deviation from Prestress
PV Module Reliability Test Result Chart: DH100
Deviation from Prestress
PV Module Reliability Test Result Chart: DH200
Power Degradation After
1,000 hours: 2.3%
2,000 hours: 12.8%
Deviation from Prestress
PV Module Reliability Test Result Chart: DH100
Deviation from Prestress
PV Module Reliability Test Result Chart: DH200

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