PERC Solar Panels And LeTID — Cause For Concern But Not Panic

PERC solar panels - Light and elevated Temperature Induced Degradation (LeTID)

Solar panel manufacturers are always on the lookout for low cost improvements they can make to get an edge over the competition.  Or rather, stay in competition, as they are involved in a Red Queen Race1 where they have to run as fast as they can just to stay where they are.

One popular method of improving solar panel output that has been to create PERC panels.  Two years ago I explained (badly) what a PERC solar panel is and I said you don’t need to give a damn whether your panels are PERC or not.  Unfortunately, it turns out you definitely might need to give a damn because many PERC panels have suffered from excessive deterioration called Light and elevated Temperature Induced Degradation; or LeTID for short.

The good news is the manufacturers of quality PERC panels are aware of the problem and are generally working to eliminate it.  In a year LeTID shouldn’t be a concern for new solar power installations as in 2020 PERC solar panels will have to be certified as LeTID resistant to be sold in Australia.

In this article I will briefly go over what LeTID is and what you can do if you have PERC panels installed on your roof and are worried they may deteriorate.

But if you really want to know about LeTID and get up-to-date information on which PERC panels are resistant to it, I highly recommend reading this article on the MC Electrical blog.  It was written by Ben Neville, the Technical Sales Manager of MC Electrical, and in the third part towards the end, it provides current information on how well-known manufacturers are either dealing with the problem or have dealt with it.  If you are at all interested, please check it out.  The main reason I am writing this article is to draw attention to that article.

Light & elevated Temperature Induced Degradation

You probably won’t be surprised to learn Light and elevated Temperature Induced Degradation is caused by light and elevated temperatures.  I don’t understand how it works exactly.  I don’t even understand how it works inexactly.  But it appears to result from impurities in the silicon used to make solar cells, with hydrogen being the main or perhaps only culprit.

It is worse in hot climates and that’s what the climate through most of mainland Australia counts as.  The reason why it is worse in hot climates is because LeTID is caused by a chemical reaction and these occur faster when temperatures are higher.  A rule of thumb used by chemists is a 10 degree increase in temperature will double the rate at which reactions occur.  This commonly true for organic chemistry, but since we are talking about silicon, to be sure you’d have to ask an inorganic chemist.

inorganic chemist

Here we see a picture of an inorganic chemist hard at work. (Image: Chemistry World)

On the off chance you can’t find a robot chemist, you could always ask a human chemist who specializes in inorganic chemistry.  I understand there’s a few of them around.

Manufacturers Are Working On The Problem

Solar panel manufacturers are working on the LeTID problem.  Or at least the ones that care about quality and reputation are.  If you buy cheap no-name PERC solar panels, then major LeTID issues would not be a surprise.

This article written just 5 months ago suggests many PERC module manufacturers were unaware of the problem.  But at least 9 times out of 10 when you raise a potential panel problem with a manufacturer’s representative you’ll get a blank poker face stare while they process the question followed by useful information if it is something they are comfortable taking about, or a denial there is a problem if the topic is out of their comfort zone.  Sometimes they seem so uncomfortable I get the impression their comfort zone must be on another planet.

The good news is many manufacturers are working on the problem and in some cases have LeTID beat.  The reason why they have worked hard on it is because tier one manufacturers sell panels to solar farms where output is monitored carefully and if large numbers of PERC panels fail to meet their performance warranty it will cost the manufacturers a vast amount of money.  It is possible we will see more than one manufacturer suffer major financial distress because they didn’t get onto the problem soon enough and sold large numbers of LeTID affected solar panels.

How To Protect Your Solar System Against LeTID

The easiest way to prevent LeTID affecting your panels is don’t buy PERC panels.  Alternatively, you can check Ben Neville’s article and make sure you only get PERC panels from a manufacturer that have solved the problem.

MC Electrical Has High Standards

MC Electrical won’t install any PERC solar panels they are not confident are LeTID resistant.  Your standards don’t have to be as high as theirs, but I don’t recommend using PERC panels if the manufacturer hasn’t provided good evidence LeTID isn’t a serious problem for them.

Whether or not you can believe what manufacturers say is for you to decide.  I generally believe what tier one manufacturers tell me, but I have been married three times and that might be an indicator of how good a judge of character I am.  But more likely it indicates what poor judges of character my ex-wives were.

A Lower NOCT Is Better

Because temperature is a major factor with LeTID, if you are getting a PERC panel — all else equal — you are better off getting one with a lower NOCT which stands for Nominal Operating Cell Temperature.  The lower this figure, the less hot a solar panel will get in the sun.

What To Do If You Have PERC Panels On Your Roof

If you have PERC panels on your roof you may have a problem, especially if they were installed one to two years ago when PERC solar panels were new.  Fortunately, you are protected by your panel’s performance warranty and by Australian consumer law.  While the fine print in most performance warranties appears to make them pretty shitty, this shit won’t fly under Australian consumer law.  And if a manufacturer tries to make it fly in small claims court or a consumer tribunal, in my opinion, 9 times out of 10 that shit is just going to hit the fan.  You should, at minimum, receive a new solar panel or a refund for each one that fails to meet its performance warranty and you can claim for the labour cost of having them replaced.

How To Monitor Your PERC Panels

If you have PERC solar panels and are concerned about about them declining in output it is important to monitor their performance so you’ll know if you need to make a warranty claim.  If you have monitoring equipment installed this makes it easy, but it’s not necessary.  I suggest keeping a record of your system’s annual output.  While this will vary from year to year according to the weather, if your PERC solar panels are suffering from serious LeTID you should be able to spot a downward trend2

If you don’t have records and are concerned your system may have deteriorated, you can use the Solcast site to get an idea of how well your system is currently performing.

If you find you have a problem it may be wise to wait until it’s bad enough to allow for a considerable margin of error so there can be no question you are entitled to make a warranty claim.3

Cause For Concern — But Not Panic

If you are looking at getting solar power installed and are concerned about PERC solar panels deteriorating, your choices are to either not get PERC panels or check out part 3 of the MC Electrical article to find out which manufacturers produce panels that are resistant to LeTID.  Hopefully, in 2020 every PERC panel sold in Australia will be resistant to it.

Even if you have PERC solar panels on your roof now and you bought them a couple of years ago, I would say that — fingers crossed — there is a good chance the panels will stay within their performance warranty provided they were tier one or from a manufacturer with a good reputation for quality, so there is no need to panic.  Of course, if you have crap PERC panels from a crappy manufacturer, feel free to panic as much as you like.

Footnotes

  1. “Well, in our country,” said Alice, still panting a little, “you’d generally get to somewhere else—if you run very fast for a long time, as we’ve been doing.”

    “A slow sort of country!” said the Queen. “Now, here, you see, it takes all the running you can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that!”

    —  Lewis Carol, Through The Looking-Glass.

  2. Note from Finn: I must be lazier than Ronald. I recommend everyone with a solar power system purchases Solar Analytics; which will proactively alert you if your solar panel performance drops below where it should be.
  3. If your system output is deteriorating it is possible for it to be due to reasons other than panel deterioration, such as dirt on the panels.  If you can’t see your roof you can use a long selfie stick or drone to check for pelican poop and other grime.  Note that a small child tied to the end of a stick is not a suitable substitute for a selfie stick and flinging a child is definitely no substitute for a drone.
About Ronald Brakels

Many years ago now, Ronald Brakels was born in Toowoomba. He first rose to international prominence when his township took up a collection to send him to Japan, which was the furthest they could manage with the money they raised. He became passionately interested in environmental matters upon his return to Australia when the local Mayor met him at the airport and explained it was far too dangerous for him to return to Toowoomba on account of climate change and mutant attack goats. Ronald then moved to a property in the Adelaide Hills where he now lives with his horse, Tonto 23.

Comments

  1. ian hawkins says

    Dear Ronald
    The Arrhenius equation applies to inorganic as well as organic systems – your approximation holds true!

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