Service Life of Solar Panels

Hello elnav

Unfortunately the high-energy photons of light which strike the solar panels do damage the solar cells over time, by damaging the crystalline lattices.

The lifetime of early solar panels, made around the year 1961, when I first purchased the cells and assembled these into panels, lasted some 10 years in New Zealand's clean air, and at that 10 year period, output was down to less than 20% of the original rated output.

Accordingly, I had to replace the panels, but the new cells were better technology, and they lasted for some 15 years, before output was degraded to 20% of the original level.

At that point, we moved house, and I gave up on Solar Power generation, hoping that solar cells could eventually be made, which were not "poisoned" so quickly by photonic bombardment.

So your made in 1993 panels will be damaged by photonic bombardment, output will probably be around 25% to 45% of rated original output, dependent on installation latitude and cleanliness of the air.

Later solar cells, made from Amorphous (Non-crystalline) Silicon, may suffer less from the degradation - we have yet to see.

For further explanation, there is a good technical paper here: http://www.mrc.iastate.edu/research/Biswas.pdf - sorry, link no longer available

At present, all Solar cells suffer degradation, and if the problem can be overcome at a reasonable cost, I shall once again get into the Solar Power generation business, meanwhile I wait the improvements in solar cell design, if they should ever arrive.

Kind Regards....

Thanks. that is what I suspected. So even here at latitude 53.5 North there is going to be some degradation. At this point there is not much point in trying to get these solar panels reconnected and configured to work with a new 48V battery system.

Hello again, elnav

Yes, it would be a waste of your time and effort.

Kind Regards....

Well, nowadays crystalline Si (single or poly) last for more than 20 years with minimum degradation. This has been widely probed.

On the other hand, amorphous Si is quickly degraded when exposed to the sun.

There is no such information of CdTe cells.

So if you are worried about long term degradation, stick to crystalline Si and avoid amorphous Si.

Before you discard these panels perhaps you should test them for output. Expose the module to full sunlight and measure the Open Circuit Voltage (Voc) and Short Circuit Current (Isc). The ratings label on the back will then give you an idea of how degraded these are and if you can use them or not. Even if they are degraded slightly they probably still make some usable power.

Like I said. Even if these panels stil produce full output, when wired in series they will only produce 5 amp @ 48V. Not enough to make any difference to this installation. We may be able to use them somewhere else in a trivial application, but not here.

Most all Solar panels have a warranty that they will produce 80% of rated power at 20 or 25 years. I think most of the degradation is from UV damage to the exposed glass/clear encapsulation layer although there are other contributors.

I think you may still get useful power from your 15 year old modules.

You can short the modules and measure the current under various light conditions to get an idea how well they are operating compared to the rated short circuit current. The Isc is determied at 1 Standard Sun which is 1000w/square meter of sunlight. You may see that much light at noon on a clear day but don't count on it.

Is there a table showing how much degradation compared to a standard sun you get with rising latitude. We are at 53.5 degrees north. Somehow I doubt we get a standard sun on the best of days.

If you go to http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/

you can find the average daily and yearly sun-hours for many international locations.

These are good for predicting annual output. NREL also has hourly sun data but I think it is for U.S. sites only.

I read some where in a forum some one used clear laque and painted over the clouded encapsulation layer on his solar panels increasing output close to what it was when new. May be bull though never tried it.

Hello solarbuster

That story comes from the farmyard

The ageing problem is damaged crystalline lattices.

These may be temporarily "repaired" by careful application of heat, but next time the radiation damage (for that's what it really is) occurs much faster.

Thus the "temporary" repairs are not worth doing.

Kind Regards....

I know I'm splitting hairs, but ix-nay onda anel-pays

The industry prefers MODULES [for some reason]--I had it drummed into me six ways from Saturn...

Hello, there. I just bought a solar panel from this company they gave me this manual for analyzing or how to operate it. Last weekend I paint the lens from inside so it can consume more light as not before. But now the heating is going down as I didn't expected and I also think that there is broken fire line has occurred in my solar lens. Please help me to solve out my problem.