PV Panel Moisture Issues

Moisture inside a working panel is its worst enemy. Hence, all panels are designed to keep moisture out. Moisture will not only "fog" the inside surface of the panel obstructing light, decreasing efficiency, it also slowly causes corrosion to electrical contacts. This corrosion increases resistance at the solar cell and reduces current flow. This resistance also causes heating which further reduces the solar cells efficiency. This has a knock-on effect that nearby cells also are affected by the heating and current flow. If the panel has a highly rated power output and resistance is great enough, there is a real potential for shorting and serious damage to the panel, which is another reason water and electricity don't mix.

Never have torn one apart but it seems like a commercial panel must be a solid piece with no air space in the cell assembly?

For solar cells, front surface is hard deposited on glass and the then covered by a protective layer from behind. Moisture can enter back or side ways if panel is not moisture shielded properly. Light sensitive layer can not be easily affected by moisture, but back layer can be as sealant quality matters a lot there. Damage is rather show and perhaps solar cells are built for 20+ year life span..

In control panels to deal with moisture we have an arrangement with Anti-condensation Heater(ACH).More over we have silica crystal to absorb moisture.Cover the crystal in a porous cloth and put it in the panel.When it absorb water the color change from blue to red.To reuse it dry it in sunlight or fry it dry.

ACH