Moisture exposure

Moisture exposure means water or water vapour from the surroundings getting into modules, junction boxes and connectors. It is a key stressor that degrades PV modules. Inside the module, moisture breaks down EVA by hydrolysis, which releases acetic acid. The acid corrodes the silver gridlines and solder bonds, so series resistance rises and current collection drops. This is severe metallization corrosion. Moisture enters through the backsheet, along the module edges and at junction box penetrations. Even glass/glass modules do not keep it out completely. Delamination creates faster paths for water to get in and lets it condense, which speeds up corrosion. Water that gets into damaged or poorly sealed junction boxes corrodes the contacts. This can cause junction box failure, interconnection failure and insulation faults during humid periods. Humidity getting in through a defective or detached junction box also increases corrosion and weakens cell interconnections. This can lead to cell interconnection failure. In potential induced degradation (PID), corrosion caused by moisture getting in is the electrochemical mechanism, and it cannot be reversed. Salt mist in coastal areas has been reported to speed up PID. Exposure is higher on floating plants, in coastal areas and in humid climates. It is reduced by choosing module designs and installation practices that limit moisture, by sealing junction boxes properly and by finding out where the water is getting in.

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• sentence 1: support check: partial - Passages call humidity a key stressor and mention ingress via backsheet, edges and junction box, but give no definition of moisture exposure as such.
• sentence 7: support check: partial - Floating, coastal and humid exposure and mitigation by module design/installation and investigating ingress causes are supported, but sealing junction boxes properly as a mitigation is not stated. -->