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PV cells degrade with time?

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Steve Conner

Mon Jan 22 2007, 05:37PM

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

Of course I do, I know better than to go posting unsubstantiated claims in a nest of fossil and nuke lovers like this.

is a good summary of research on PV payback time.

is a selection of other papers.

Ben

Tue Jan 23 2007, 08:44AM

Vigilatny
Registered Member #17 Joined: Thu Feb 02 2006, 02:47PM
Location: NL
Posts: 158

I'm still skeptical that this includes the clean up or environmental damage associated with semiconductor manufacture:

It isn't mentioned, and it usually takes place in forgettable places like Taiwan or China, especially if it is cheap. I would guess, accounting for using clean sustainable manufacturing processes pushes those pay back times out to 15-30 years. The high efficiency solar cells that might be used for transportation, likely never pay back. Also the specific pdf you linked mentions nothing about degradation. The line is linear out to 30 years(Fig 2). While I'm sure the degradation is not as severe as in space, it must still happen. That sort of sloppiness makes me question there position. Yes I realize it is the DoE. After working with many national gov'ts including many departments in the US gov't, I'm not going to be swayed by their authority(no offense to BC).

Anyhow I haven't got a problem with solar, I just don' t think the current technology is ready for mass use.

Sulaiman

Tue Jan 23 2007, 12:48PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

I would expect all types of silicon solar cell to degrade with time due to slow migration of dopants and metalisations;
but I doubt that would be the main problem;
over the (say) 30 year lifetime of a solar cell how much would be spent on storage batteries and general maintenance?

I was in a (very) remote village in Malaysia where BP Solar and some Government agency had set up solar cells,
mainly for radio communications and lighting.
Of the original 20 systems installed only 3 were working due to lack of maintenance.
So I suspect that the actual lifetime of the (in this case lovely monocrystaline) solar panels is irrelevant compared to batteries and maintenance.
Solar panel powered fixed ATUR (450MHz cellphone from memory) telephones installed and maintained by the Telecom company have been successful in remote villages.

Avalanche

Wed Jan 24 2007, 10:59PM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

As for the 'paying back the amount of energy it takes to make them' thing, it really makes you wonder especially after seeing this. A fairly large looking factory, brightly lit by (probably) several thousand watts of HID lighting, assembling 6 panels per day, using various equipment such as ovens and sunlight simulators.

Hmm...

I think I'd have them using LED headtorches

Bjørn

Thu Jan 25 2007, 04:31AM

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

Solar cells are a lot cheaper to produce than most people believe. The production capacity doubles every year but the demand outstrips supply by far so prices are very high.

This means that at the moment you can produce solar cells anywhere in the world using very inefficient methods and still make money.

Tue Jan 30 2007, 01:57PM

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

Avalanche:

Nice video reference. Thanks. I look forward to the day when a factory like that can produce 500+ panels per day via automation (instead of hand assembly), plus hopefully lowering the cost due to high volume component price breaks. I know from personal experience that early stage production of an evolving technology can be slow, tedious and 'handcrafted' but that proper automation can greatly increase production output and lower costs. In the 80's when I patented the wireless microphone (my version of it anyway, black with no antenna often seen on TV) in the beginning we produced a dozen or so per month... then after installing automation (computer assisted assembly, wave solder machines, etc) produced thousands of them per month sold in over 90 countries. I'm quietly cheering on PV evolution. CM

Bjørn

Wed Jan 31 2007, 04:00PM

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

The latitude does not make a significant difference, you will still get your 1kW on every square meter even at higher latitudes than Scotland.

Just to make it clear, this is true if you tilt the collector towards the sun. If the collector is flat on the ground the effect of latitude will be significant. I assume that people that put up a collector of some sort will tilt it for maximum efficiency.

Steve Conner

Wed Jan 31 2007, 04:56PM

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

It's actually not even true then. At higher latitudes, the sunlight has to pass through more atmosphere, because it goes through the atmosphere at a slant. Water vapour, dust, etc, all absorb some of your light. "Air Mass 1" is your Google search term to find out more, but I seem to remember you get 1.5kW/m2 outside the atmosphere, 1kW/m2 at sea level on the equator, and 0.6kW/m2 at my latitude.

Having said that, I remember that I once logged a remarkably high power from my PV array, that looked as if it would have taken over 1kW/m2 to produce.

I also once did some experiments in a solar simulator chamber that used 100x 150w filament bulbs. Man was it hot in there!

It also had a wall of mercury vapour lamps, but we couldn't use those because the 100Hz flicker caused heavy modulation of the current from the PVs and messed up the results.

Bjørn

Wed Jan 31 2007, 06:03PM

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

You get about 1.3kW/m2 at the top of the atmosphere at the equator. In Norway a bit further north than Scotland it has been measured more than 1kW/m2 at ground level without a tilted collector. So the latitude makes no significant difference to the the peak power.

On the other hand the distribution over a year changes significantly, some places you would have sunlight 24 hours a day for some of the year and no sun at all for some of the year. Since the sun is lower on the horizon for more of the time the weather and type of PV cell becomes a lot more significant.

...

Wed Jan 31 2007, 11:46PM

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

Something that you also need to consider is the efficiency vs wavelength curve of a solar cell. The 'old' single junction silicon cells (I believe that amorphous/polycrystalline are about the same) give out the same amount of energy per photon of light for 1000nm radiation as 100nm. But that photon at 100nm had 10x the energy as the 1um one, so likewise you only get 10% of the efficiency for 100nm as 1um (well, with a few simplifications made, but if you can say that 1.3kw/m is the almost the same as 1kw/m...).

But, with the triple junction cells that have several bandgaps (and incredibly high pricetags) are much more sensitive to having the higher wavelengths filtered out by the atmosphere (and that is why they work great in space)

But I would have to say that there is considerably less solar energy on the poles, something tells me that a 30% difference in light density wouldn't account for a 50C differential temp difference... But I suppose it is possible.

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