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PV cells degrade with time?

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LAN_403

Mon Jan 15 2007, 03:51PM

Banned on April 7, 2007
Registered Member #277 Joined: Fri Mar 03 2006, 10:15AM
Location: Florida
Posts: 157

1) Once upon a time I read that Photovoltaic Cells degrade with time/usage and that they must be replaced every 20-25 years. Haven't been able to find that article again. Is this fact or fiction?

2) The same article stated that it requires more energy to produce a PV cell than the PV cell will ever produce in its lifetime. Fact or fiction? CM

stop4stuff

Mon Jan 15 2007, 05:31PM

Registered Member #64 Joined: Thu Feb 09 2006, 06:25AM
Location: Southampton, UK
Posts: 68

1) PV panels degrade with time, modern panels last around 30 years
2) energy payback time is usally less than 3 years... tho afaik no solar panel manufacturer uses all solar energy to produce solar panels

see;

...

Mon Jan 15 2007, 06:02PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

OK, cheep cells may or may not degrade over time; but a real cell will last forever. The reason that panels need to be replaced is that the glass gets dirty/yellowed/etc and reduces power output.

Also, a solar cell will produce considerably more power than it took to produce it; how do you think that solar cell manufactures pay for the bills (and electricity is one of the cheapest ones they pay when you look at the chemicals they use)?

Finally, Aixtron (a solar cell manufacture localed in Aachen) does have a solar panel set up at the plant (I have seen it, on a rainy day it puts out ~100w), but it does not produce even close to the amount of power the plant uses. But than again, that plant can produces a panel that size several times a day

Electroholic

Mon Jan 15 2007, 08:44PM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

yes, cells will last forever if sealed/encapsulated.
and a good encapsulaton and surface finish will actually increase efficiency.(by not reflacting as much light)
gochermann is one of the leading company in this area.
and believe it or not, monocrystalline cells are actually quite flexible with proper backing material to balance/spread out the stress.

Tue Jan 16 2007, 03:24PM

Banned on April 7, 2007
Registered Member #277 Joined: Fri Mar 03 2006, 10:15AM
Location: Florida
Posts: 157

Here's a report titled "Service Lifetime Prediction for Encapsulated Photovoltaic Cells and MiniModules" makes for some interesting reading. Talks about many things including 1%-2.5% power degredation per year of PV systems, but that might be due to the encapsulation as mentioned above. Looks like whenever this report was written they were hoping to someday achieve a usefull lifespan of up to 30 years for PV systems. CM

Carbon_Rod

Tue Jan 16 2007, 10:48PM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

The Si based units as far as I know decay by over 20% in 5 years.

The data related to optics assisted PVs may highlight accelerated decay estimates in elevated operating temperatures.

Actually what I found interesting was how snow tended to melt and slide off the panels even in sub-zero (c') temperatures. Also surprisingly remained active in overcast sky's.

Cheers,

Electroholic

Wed Jan 17 2007, 07:00AM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

For every degree increase in kelvin, output power drops by 0.44-0.5%, this is true for standard silicon terrestrial grade cells, but is reversible as long as you don't go over 85 degree C.

I don't see why a well encapsulated moldule will decay anywhere close to 20%, unless you have broken cells in the moldule, and there is no bypass diodes.

AndrewM

Wed Jan 17 2007, 07:29AM

Registered Member #49 Joined: Thu Feb 09 2006, 04:05AM
Location: Bigass Pile of Penguins
Posts: 362

As an engineer at a satellite company, I'm positive that aerospace-grade PV cells don't degrade 20%/5 years, or anywhere close. A satellite with a 15 year design life would be left at 50% power at EOL by these figures, and that... well I doubt anyone would even buy a satellite with that kind of degradation.

Burrito day is tomorrow and I typically go with a manager from the solar array group: if I remember I'll ask for some numbers.

Bjørn

Wed Jan 17 2007, 07:31AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

Output voltage drops but internal reistance also drops so in some odd cases the total efficiency may rise as temperature rise. It all depends on the design of the regulator.

Devleopment speed has accellerated a lot and papers that are more than a year old may be out of date so googling for information may give very wrong results unless the age of the information is checked.

Steve Conner

Wed Jan 17 2007, 11:03AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I seem to remember the main problem with PVs is that the encapsulation degrades and lets moisture and other yucky stuff in, which messes up the cells. That is why they wear out on Earth, but it wouldn't be a problem in space.

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