I know the Monocrystalline solar panels cost more then the Polycrystalline solar panels, but which one of the two will last longer?, and will they leak over time? and will they fade over time?
what I mean by leaking is, moisture underneath the glass.
I don't have them in my home, if no-one else on here can answer then I might be the best you'll get :/ I've done a little research on solar panels (we developed CdTe rather than Silicon but we worked with other lab groups that do use silicon).
Most solar panels will degrade slightly with time (a common cause is because solar cells rely on a junction, and thermal energy jiggles about the atoms and can mix up your dopants so that the junction quality goes down a bit over time). Generally speaking, more grain boundaries between crystals speeds up the rate of degradation so polycrystalline panels should degrade more quickly than monocrystalline ones (although if other decay mechanisms are dominant, or the system is generally stable, then the difference will be tiny).
Generally panels are well sealed against the elements so it shouldn't notably fade. Keeping the glass reasonably clean is good for output.
What do you mean 'leak'? Silicon panels are solid state devices, unless you're planning on heating them to hundreds of degrees C they will remain solid and shouldn't 'leak'!
When I say polycrystalline cells should degrade more quickly than monocrystalline, it's all relative. Most solar panels will be guaranteed for somewhere between 20-30 years and over that period they should not fall below 80% of their rated output (many should degrade even less).
EDIT: Moisture underneath the glass isn't a problem I've heard much about (but my experience is with lab tech devices we've grown specially rather than full scale real world ones!). In principle it shouldn't be much of a problem; typically your cells will be 'sandwiched' between two glass layers which are then hermetically sealed. There's a chance of leakage, in the same way double glazing might leak occasionally. This effect shouldn't be that different between mono- and poly- crystalline cells and it should be accounted for when they give you their 20-30yr guarantees!
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