Panel Degradation

[SRE]

Can anyone explain the impact of degradation on panel efficiency please? I'm struggling to understand why the Schott panels are better than others with amonia when they are less efficient. Ie Schott 230 13.7% ish and Sharp 245 (when certified) 14.9%.

Surely if the sharp panels are 1.2% more efficient, this makes them 8.7% more efficient than Schott - 1.2 / 13.7 x 100 = 8.7% So if Sharp degrades by 2% then they are still more efficient than Schott??????? Have I lost the plot

 

[edexlab]

what do you mean by amonia ? have'nt heard of this term?

 

[SRE]

The amonia issues related with putting solar panels on cow/chicken sheds - apparently it degardes Schott panels less than other panel manufacturers.

 

[poheZ]

is this less efficient at converting to a dc current?

If so why should this have anhthing to do with amonia

 

[DomB]

As I understand it, the efficiency of a panel is essentially just a measure of how much power it produces for a given irradiance over its area. Doing the measurement at STC, when the irradiance stays the same, boils the 'efficiency' down to just being a measure of the panel's power to size ratio.

The degradation of that efficiency could be down to a number of things inc. the silicon degrading or other panel components degrading due to the environment, e.g. ammonia affecting the glass & therefore the amount of light that gets through.

The Schotts panel efficiency could be low cos they put bigger gaps between cells - the 'cell efficiency' is a better comparator on silicon quality there. The Sharps may have a higher efficiency to start but put them on a chicken shed and the degradation of their components & therefore their overall efficiency would be quicker.

 

[SRE]

Thanks DomB, I guess my query is whether the higher level of degradation on the non Schott panels is outweighed by the higher initial efficiency??

There's no doubt that amonia is going to have an impact, makes my eyes water just doing a survey! At the Segen conference one of the installers reckoned that degradation didn't have anything to do with the efficiency but I can't see that being right can you? I thought that was the whole point about the amonia tests.

My dilemna is cheaper price and greater efficiency now v more expensive panels and less efficiency but a slightly betterchance of staying in one piece.

When you look at the test reports for Schott v other non specified panels there's only about 1.5% difference, they just show it on a bog graph to make it look more.

 

[DomB]

I'd say if you have enough space for the size of array then panel efficiency isn't the main issue..sounds like the environment is tho

Not sure I'd agree with the installer you talked to there - the efficiency is exactly what does degrade and what's effectively quantified in the spec sheets and guarantees (output goes down to 80% but the panel size stays the same = efficiency drop). I suspect its just the cell , i.e. silicon, efficiency changes they measure in the labs but I got the drift that Schott are taking other means of degradation very seriously

 

[RecycleElectron]

There are 2 m's in ammonia. Sorry............Interesting thread though, as are general lifetime issues for this technology I suspect. You have to wonder how often the things will get cleaned in this sort of grubby environment too, as this may have just as large an effect on the efficiency? The job of cleaning them way up on a fibre cement roof may not be attractive to farmers or there may be more farm workers falling off the forks of telehandlers............Ammonia test SCHOTT Solar

 

[edexlab]

Ah ammonia
I've done work on chicken sheds before and ammonia causes an increased rate of corrosion on a lot of materials especially aluminium ,not sure it has an effect on glass though obviously ammonia and lots of other chemicals can be stored in glass containers, but on the anti reflective coating possibly, do Schott protect the aluminium with a coating perhaps ?

 

[SRE]

There are 2 m's in ammonia.

and 24 hours in a day but I seem to be working 26 at least

I read the Schott test reports a few weeks ago but they don't really say much. I remember the University of strathclyde bringing out some research for a heatpump manufacturer in 2004/5 which said they were great, had a cop of 3.5 and were cheaper to run than electric. That was all true if you had a small house which you never opened the doors or windows in and used daytime electric for radiators (not storage heaters). How many people do you know that live in a house and never leave it.

I'm worried that the Schott tests may have had similar restraints - they only tested the panels for a few hundred hours at an increased level of ammonia that was supposed to replicate 25 years of use. I'm no chemist so I don't understand the difference between intense exposure to a chemical for shorter periods of time than lower levels at longer periods.

DomB, the efficiency of the panels does matter 9.9kwp @ 14.9% is more efficient than 9.9kwp @ 13.7% especially over 25 years that's why I'm bothered about putting less efficient panels on. I agree with you about the other installer though - I'm sure that degradation is all about efficiency.

I did hear somewhere that I should be looking for anodized frames - anyone know who's panels have anodized frames???

 

[RecycleElectron]

There's not really any alternative to accelerated tests if you want to bring a product to market in less than 20 years! They will do control tests to "validate" them, like using different concentrations to see if the effect is linear or not. Beyond that the R&D is often done at the customer's expense. On the scale of the coatings (microns), the corrosion of even the glass itself may be significant and some thin film coatings are very susceptible, so different technologies may well be more suitable than others in an alkaline environment. With all of the thermal cycling going on it must be quite difficult to stop ammonia and water vapour getting into the panels eventually to some extent? Aluminium is not happy with alkaline solutions so anodised frames may be helpful, but maybe only if the extrusions are anodised after cutting or the cuts are sealed 100%, (unlikely I think in both cases) and you can always get them up there and maintain them without any scratches or stress cracks..... See (Inorganic coatings) so you might have to paint them too to be on the safe side. Electrolytic corrosion could be worse in a hostile environment, so choice of fixings material could also be critical.