Hi,
I keep reading that Unisolar triple-junction Amorphous Panels degrade over time.
Has anybody got actual data confirming the level of degradation?
The data I would like to see is:
1. Rate of degradation (with respect to time), and
2. If degradation rate changes relative to solar exposure (eg, more sunshine - higher rate of degradation?)

I currently have Unisolar (Model US-64) panels and they do seem to have been degrading over the 6 years I have had them installed.
Unfortunately, I haven't got sufficient data to prove this, or display a measured result of this observation, as weather variations and loading on the panels have been undergoing change.

I am about to consider additional panels but wonder if Unisolar should be on my shopping list? (obviously they would need to be electrically compatible but I haven't researched the likely compatibility problems).

Currently I run the panels in a '6 series' configuration wired into an Outback MX-60 Controller feeding a 48V nominal battery bank.

I would appreciate any comment which would help me on this matter.
Best regards, Fred

hi fred,
i too have the us64s and i was basically under the impression that most of the degradation was in the first year or two, but like you i have not tracked my pvs with any known standards to see their statis. i may run a current test on mine (about 4 years old) if i get a good opportunity, but i can't say what the irradiance of the sun would be for comparrison. i'm not considering anymore unisolars because for the same money or less i can get more reliable and efficient pvs. the us64s are good for areas that may have kids throwing rocks at it or something, but the glass on other pvs can resist 1 inch hail going at i think 50mph or something like that as i forget.

6ea, 12V (18V typical) in series gives 108V

Do you have any voltage / current/ watt reading from your initial install to compare to ?

The US64's ARE expected to degrade over time, most of which happens in the first couple of years as Niel said. But you have to go off the published specs as your reference, as the panels new, put out about 80W, and then begin their planned degradation. The warranty papers spell out what rate they are to perform to, in which year. (unless exposed to sunlight - just kidding)

"6ea, 12V (18V typical) in series gives 108V"

correction on this as the vmp is 16.5v for us64s and that is 6 x 16.5 = 99v.

the low vmp is another bad point of these pvs.