Solar PV and " snail trail"

[Will 666]

Hi All,

Does anyone have or been able to get any definitive information on the " snail trail " issue affecting some solar panels ?

I currently have 575 modules out of 842 showing this problem to varying degrees They were installed in March 2015.

The modules are Renesola JC255M. I have also recently discovered that there is a 250 kW installation locally that was installed by the same company as mine around the same time.  When I asked to see their installation they had not noticed that their panels are also riddled with " snail trail".

These are also Renesola JC255s

There appears to be little discernible affect on production thus far that I have noticed.

Renesola seem to have commissioned a report on the" cell finger/ snail trail" phenomenon. Despite claiming there is no effect on production they conclude that there is a 1.28 % degradation after 2000 hrs.  It seems that the 2000 hrs is comprised of " extreme" environment conditions that must extrapolate into a longer time period. However it is not at all clear as to what this may or may not be, so the whole thing seems fairly uninformative.
The report implies that " micro cracking" is allowing moisture to penetrate internally and this then leaches the panel components leaving what we see as " snail trails". I cannot interpret this as anything other than a fault with the panel for whatever reason. In addition I also know that moisture and micro circuitry/ electronics do not mix well. Furthermore I am concerned that the problem may eventually affect the inverters i.e. best case scenario- the inverter shuts down or worst case, destroys the inverter. Clearly the inverter issue is me being paranoid at this stage but again with the absence of ANY kind of marking on the other makes of panel ( for info these are 140 Astro energy panels and 16 CSUN panels) I can only conclude that the panels were faulty either on arrival or after installation.

 The installer "does not recognise" there is a problem but the manufacturer does not " warrant" any  modules displaying " snail trail" as they regard it as caused by an " unpacking issue" - in other words an installation issue. Therefore I basically have over two thirds of my 3 year old panels not covered by any sort of warranty. 

Any information or experience of this issue would be most appreciated.  

 

[Sharpend]

@binky ?

 

[binky]

I've fitted shed loads of Renesola, and seen snail trails on other makes of panel and it doesn't seem to affect performance. I've been fitting panels for 6 years, including 100kW / 2 off 30kW 2 off 40kW and lots of domestic systems of Renesola and had no issues relating to this to date. Some say it's due to overheating caused by dirt on the panels, but I find that a little hard to believe as being thin film silicone, I would have thought that section of the panel would have burnt out. If a scetion did fail, or gets dirty, there are by-pass diodes in the junction boxes on each panel that 'by-pass' the faulty section, and also help prevent underperformance caused by dirt, so again I doubt overheating would happen or result in the trails. The glass is  toughened, 3mm thick, I doubt moisture would have penetrated, and the glass used shatters like old car windscreens if damaged - micro-cracking refers to overflexing of the silicone cells. There are no micro-electronics in a panel, just very fine conductive wires - that's the fine lines you can see between the thicker conductors. If you were getting moisture ingress then the inverter would register an earth leakage fault - it checks for this daily on start-up. The panels have a anti-glare / self cleaning coating that you are suppossed to keep your greasy hands off when installing, so the marks could well be from kack-handed installers, or just the manufacturing process. THe panels have a 10 year warranty, I would suggest you keep an eye on performance and the trails and see what happens (if anything). NB all panels degrade over time with an expected reduction of 20% over 25 years, so roughly 1% per year with the first year being slightly higher. 

I wouldn't worry about the inverters, a damaged panel will either register as a fault or just produce less energy, it won't go bang or overload an inverter like short circuiting an electrical system can do. Inverters are designed to self-protect ( or at least the decent ones are). What make of inverter do you have? 

If you want I coud pop over the Tamar bridge and test the system for you - but you have to admit it's better to put cream on scones before jam and the original pasty recipe comes from Devon  :^O .

@binky ?

give me a chance to type! 

 

[binky]

Forgot to say.most solar farms were built by idiots that did things like bury DC cable direct in the ground, so finger marks on the glass is almost a 'given'.

 

[Sharpend]

Sorry Binky, didn't realise you were writing a book!  

 

[binky]

just found this. forget finger marks....

https://www.solarpaneltalk.com/forum/solar/the-pros-and-cons-of-solar-energy/8580-snail-trails

Sorry Binky, didn't realise you were writing a book!  

2 finger typist, it takes a while.... :^O

 

[Sharpend]

 

 

[binky]

OK, a bit more reserach...

Now what is interesting here, is that it states 'brownish discolouration' which sounds like the water ingress stains you get in your house - you don't seem to have this. This paper, and several others I have just scan-read also suggest micro-cracking in direct relation to snail trails. Micro-cracking of the silicone is mostly the direct result of mis-handling, ie the muppets what built the solar system, BUT all the papers also say that were micro-cracking occurs there is a corresponding performance drop - you don't seem to being seeing a notable peformance drop @Will 666, so this would suggest to me minor handling damage is a possibility, or due to the discolouration not being brown, a chemical process issue from the manufacturer. Clearly handling faults are down to the installers, but as per the first article link, if you are not seeing a peformance drop, then it would suggest you have little to worry about. The installation should also have a third party warranty provided by the installer for at least 6 years. 

Now, in my mind this leaves 3 options:-

1/ a full assessment of the system design needs to be done to ascertain if the system is running correctly or within an expected set of peformance parameters - I would suggest modellng the system on PV-Sol or similar comprehensive design package, then comparing this against output on a good sunny day. Ideally you should a 'schematic diagram' of the system provided by the installer, and you will need an irradiance meter.

2/ it's working so don't worry and keep an eye on it.

3/ check the independent warranty and put a claim in before it expires - I am assuming the installer no longer exists.

Now there are so simple checks you could do, namely compare the strings, if you know how to do that. Most solar farms I've worked on have sets of 20 panels per 'rack' . So it's  a case of shutting down the strings and doing stalled test for DC voltage Voc (label on back of panels) eg 36V x no of panels will give a voltage eg 600V which should be even across all the strings with the same number of panels. Depending on the inverter set-up you may be able to just check on the display? 

View attachment EPE_2015081213522107.pdf

 

[Will 666]

 

Hi Binky,

Many thanks for all the info.

In reply to your first post, the Renesola report that I mentioned in my first post claimed that the white coating on the rear of the solar modules is not completely moisture proof anyway although they claim to have the thickest coating of most manufacturers.

This is where the moisture is coming from and it then seeks out the micro cracks and results in the snail trails ( my basic understanding!)

The panels do carry a 10 year warranty and a 25 year production warranty but the issue here is that the new Renesola " terms and conditions " under a section titled " limitations and exclusions" specifically states any modules displaying snail trail are not covered by any warranty.

 The inverters are SMAs, linked via a cluster controller. I can compare total output from each inverter only, not individual strings of which there are six to each inverter. However thus far,  the outputs are always very similar.

Finally I would welcome you casting an eye over my install if you had the time but I can't possibly agree over the " scone " thing !!

My wife makes the best scones going and she's Cornish so you can appreciate my dilemma.!

I'll get her to make some on the day - how's that ?

.

 

[binky]

add a nice brew and you have a deal!  :^O    I engineer my scones, if you put lots of jam on first, the huge dollop of cream can slide off, couldn't give a damn whether or not it's Cornish or Devonian. Where abouts in pasty land are you?

Interesting warranty change by Renesola. Thickness of backsheet is less important than the quality. German and Japanese panels have a very thin sheet, but you can tell it's better quality.  A lot of people don't realise how important the back-sheet is when handling panels - they all worry about breaking the glass. It kind of sounds like rough handling and poor storage of the panels during build of the system might be the issue. Not serious enough to cuase proper micro-fractures, that cause power loss, but enough to cause some damage that doesn't affect performance. Either that or you are in a very windy part of Cornwall and the panels are being flexed a lot! No point asking if they get wet :^O .   It never ceases to surprise me how many broken panels occur in the middle of solar farms like after the last Northerly gales we had early this year. I would dig out all warranty stuff from the time they were fitted, in particular look for an independent third party waranty from Renesola, just in case they go bust.  

Another article for you...if you know anyone with a thermal imaging camera, they are very useful for detecting hotspots caused by power loss causing micro-factures.

https://www.gses.com.au/wp-content/uploads/2016/03/GSES_microfractures.pdf

Did they link you to the SMA portal? Think they have to for the cluster controller. You shoud be able to get a very good idea of any differences from that, plus SMAs have a 'string learning' function so if it thinks an inverter / MPPT is under performing it should flag it up as a potential issue. If you have the inverters with panel display, you can compare the voltages per MPPT on the display - obviously they won't all be indentical because as you walk around the cloud cover can vary quite rapidly, which is a bit annoying when trying to check things. Clear day after raining is a good time to look, as the rain should clean the panels and knock off bird droppings and dust.  If the installer was feeling keen it should also send you an e-mail of any issues as they arise. SMAs are my favourite inverters (apart from the price) they have evry good monitoring functions, and I have found them to be more reliable than other makes like Fronius or anything from China (albeit the Chinese are getting better). 

 

[Will 666]

Hi Binky,

That's a deal ! 

We're just outside Newquay. How do we pass contact details via a forum site ?

The SMAs do seem to be solid gear, I log into the cluster controller to get realtime info as the sunnyportal has a delay for some reason.

However the Sunnyportal is good for comparing annual outputs. I'm not sure if there are other settings and options available through the

" installer" login. I only use the " user" login but I do have the installer password.

The thermal imaging camera idea sounds as though it might be worthwhile. 

 

[binky]

you can send a message via the little envelope at the top right of the page

 

[binky]

@Will 666, well the portal shows a system that looks like it's working well. Click on the bar on the right that says 'visualisation' this drops down a menu. Click on 'devices' and this will show the individual inverters allowing you to make direct output comparisons, and outputs are quiet consistent over the years with the usual weather dependent variations. So I think your best course of action is to watch it all closely, your panel warranty is for 10 years (supply and fit)  with  a further performance warranty up to 25years (supply and fit it yourself), so in theory you have plenty of time to lodge a claim if necessary.

 

[Will 666]

" In theory" is right because Renesola are telling me they will not warrant modules with snail trail because they have

been "mis - handled "and therefore "damaged" in their view. It's a bit of a tricky one really. The installers have stated that they do not "recognised a problem" as they are performing as expected let alone acknowledge that they might have messed up.

I think I read that the module manufacturing side of Renesola has been sold and they are not now supplying Europe. Don't know how much of that is true but either way  it makes the likelihood of a genuine claim being honoured somewhat questionable. 

I think what I need is to find a group of Solar PV owners that are clubbing together to challenge the snail trail question as I firmly believe it is a manufacturing issue.

Anyway see you soon - let me know and I'll get the scones sorted !!

 

[binky]

I would say the installers ae at fault here, I have fitted shed loads of Renesola and not seen snail-trails on any that I have installed, which does suggest mis-handling. The installer should have given you a 3rd party warranty, I think you would be best to make conatct wth the insurer and put a claim in. Trouble is the installer is probably skint and likely to go bust asap. Many have shut down to avoid warranty claims...  Who did the installation?

 

[Will 666]

Still trying to coax a response other than " we don't recognise a problem" out of the installers, Clean Earth Energy at wadebridge.

Can't  find any signs of warranty other than the installers 5 year warranty and the Renesola one.

Does anyone have any sensible contacts in REAL or RECC. The muppets I've spoken to seem to know a combined total of zero, and that's when you can get a response. Most of the time they simply don't call or email you back. Hopeless! And these were in charge of overseeing compliance of installations and codes of practice etc. Explains just about everything.

 

[binky]

RECC can be rather slow! Trouble is they aren't technically minded people. Clean Earth should have regisitered your system with a 3rd party insurer, although that isn't compulsory on commercial systems like yours. I've always done it in case the business folds - bit of extra peace of mind for customers. I doubt Clean Earth will be willing to do anything, with the slash in FiT and subsequent slash in work, there isn't 'spare' cash to replace a set of panels, which might have happened when turnover was far higher. Might be worth talking to this lot, they have a branch near you. https://www.bre.co.uk/nsc/page.jsp?


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