#1 Jan. 30, 2014 17:41:00

SteveRogers
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Up to 35% of PV Systems are underperforming


The latest YouGen newsletter indicates a third of PV systems may be underperforming:


http://tinyurl.com/pxhoo5d


To quote:


“The causes of system losses are commonly down to shading and technical faults with the inverter. However, our research identified a number of additional reasons. These include poor or incorrect wiring during installation, residual current devices (RCD) tripping (which in many cases can go unnoticed for many days or weeks), tenants inadvertently disconnecting the system and pay-as-you-go meters cutting out generation.”


I'm sure that wouldn't happen to us geeks on here
Steve


URN 215 North Yorkshire 3.96 kWp, S facing, 40 deg tilt, minor shading





Edited SteveRogers (Jan. 30, 2014 17:41:00)

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#2 Jan. 31, 2014 09:57:00

Britta
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Up to 35% of PV Systems are underperforming


Steve, this is really interesting information. Although I'm not 100% convinced about the source, I think this kind of confirms what a lot of us already know; that this technology might not be quite as Fit and Forget as first assumed. I think you are right that ‘you geeks’ as you say are probably ok because you will spot things, but a lot of people will not, which I think is actually a real issue.


I was reading some forums on Navitron the other day and noticed this incident where somebody has posted basically an ad for a product, a form of coating as far as I rememeber (the actual post had been removed) claiming to improve efficiency. Somebody who knew their way around numbers spotted that the ‘science’ behind this product was completely flawed. But a lot of people wouldn't have. These are shark infested waters…


So, just thinking aloud here really, but there is obviously a lot of informal expertise out there, on forums like this and others, so what do you think, should knowledge oblige? do you share this critical information with ‘non-geeks’? how?


Britta








Edited Britta (Jan. 31, 2014 09:57:00)

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#3 Feb. 1, 2014 16:34:00

SteveRogers
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Up to 35% of PV Systems are underperforming


Britta,


Could you re-phrase the question ending “should knowledge oblige?”  I think I've got lost in the punctuation


Yes, Navitron is useful but you have to be aware that the forum is sponsored by the parent company and there may be some bias or editing of the discussions.


I've also found the electriciansforum site quite useful for hardware questions/problems.


I hope no-one was insulted by my “geek” labelling of forum users.  If so, I apologise.


Steve


URN 215 North Yorkshire 3.96 kWp, S facing, 40 deg tilt, minor shading





Edited SteveRogers (Feb. 1, 2014 16:34:00)

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#4 Feb. 1, 2014 20:44:00

Britta
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Up to 35% of PV Systems are underperforming


Hi Steve


Sorry, I'll rephrase. (maybe that's a Danish saying then, I'm Danish) what I mean is should people who have a particular form of knowledge (- in this case knowledge that could move your system from underperforming (I wonder by how much?) towards overperforming by 17%), try to find ways of sharing this knowledge for the good of other people, and I suppose in this case the environment? I'm curious because people on this and other forums I look at are exttremely generous with their knowledge and helpful in trying to help people out who have particular issues with their systems. But does that extend to the wider (possibly less informed) population of PV owners?


Britta





Edited Britta (Feb. 1, 2014 20:44:00)

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#5 Feb. 2, 2014 15:48:00

SteveRogers
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Up to 35% of PV Systems are underperforming


I agree, Britta.  But how to achieve that.


It would be good if installers could point their customers at appropriate forums (though I guess some would rather not for fear of their poor methods being found out ).  “Fit and forget” is a dangerous strategy to adopt …


Steve


URN 215 North Yorkshire 3.96 kWp, S facing, 40 deg tilt, minor shading





Edited SteveRogers (Feb. 2, 2014 15:48:00)

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#6 Feb. 5, 2014 17:27:00

rogerhoward
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Up to 35% of PV Systems are underperforming


Whoever said that these systems were ‘Fit Forget’? As Steve says, that is indeed an unrealistic expectation. Is it not up to us owners to take some interest in the performance of our investment?


Agreed that most PV owners do not. Although I did from Day One collect daily generation meter readings (soon augmented by daily consumption readings for comparison too!), I only ever had a cheap ‘n’ cheerful installation without proper monitoring, I still don't have any realtime monitoring, and if I do have to go into the loft it isn't to say ‘hello’ to my inverter. If we're honest, it's not so much the PV systems that are underperforming, as us PV owners who are negligent in our attention.


Appealing to people's wallets about how much they may be missing seems to be the best way of attracting PV owners interest - and the one this YouGen article takes I think. But our issues often highlight lessons for the PV installation trade too.


As regards wider sharing of all this gleaned experience and information, the Sheffield Solar Team publish on here an always-interesting monthly newsletter, that normally mentions any of our discussions that are of more general interest.


With Lisa's trade contacts, I'd have thought that the Sheffield Solar Team are better placed than the likes of any of us to publicise our ‘issues learnt’ to a wider trade audience.







Economy 10 tariff provides 6.9p/kWh off-peak import between 12am-5am, 1pm-4pm and 8pm-10pm; http://www.pvoutput.org/aggregate.jsp?id=21047&sid=18934&v=2&t=m on approx. 63% off-peak usage, 22% solar usage, and 15% peak-rate usage.
1,900kWh annually is exported, mostly in summer, on approx. 3,200kWh generation. Approx. 4,500kWh/year is imported, mostly for (a) winter and springtime off-peak Storage Heaters, and (b) off-peak hot water Immersion heating (which is “dumb”, i.e. not linked to the solar PV).
PV array is split East-West. Income is from Phase II 21p/kWh Feed-in-Tariff plus smart metered 3.2p/kWh Export Tariff.

Edited rogerhoward (Feb. 5, 2014 17:27:00)

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#7 Feb. 5, 2014 20:37:00

SteveRogers
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Up to 35% of PV Systems are underperforming


As luck (fate?) would have it, I had a problem with my inverter yesterday morning.  It seemed to be an earthing fault on one of the array strings, possibly through water ingress or corrosion or maybe a connection working loose in the wind.  It fixed itelf by 11:30 but I lost around 20% of the day's production.


The symptom was a red light + flashing green light on the inverter (SMA 3600TL) with the message “isolation resistance” and “check generator”.  And, of course, no production


I've contacted my installer and they say they will send an engineer out.  We'll see how long that takes


The warrantee on workmanship for the installation runs for 3 years so the cost should be covered as the system is just over 2 years old.  It begs the question what I do after the 3 years is up.


Incidently, earthing connectors should be tin-plated to prevent corrosion.  The tin corrodes preferentially over copper or aluminium to form a very thin, passivated layer of tin oxide that is still conductive.  I don't know what was used on my array.


Steve


URN 215 North Yorkshire 3.96 kWp, S facing, 40 deg tilt, minor shading





Edited SteveRogers (Feb. 5, 2014 20:37:00)

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#8 Feb. 6, 2014 10:13:00

Britta
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Up to 35% of PV Systems are underperforming


I'm sorry to hear about your ‘luck’ there Steve… good job you have your warranty. Do keep us posted though, I'm very curious about what happens next. Also I noticed on the “system Tripping' thread that daved42 had some experience of earth leakage, if you haven't spotted that.


It appears now that you are of course right, that PV does need someone to keep an eye on it. I know for sure that you are right that a lot of people don't. In my research I have spoken to a lot of people who have bought solar panels exactly because they were told that it needed no maintenance ”no moving parts, you won't know its there…" because that is what it said on the tin, at least back in the ‘gold-rush-days’ when the FIT first appeared. These are people who do not know and do not care to know what a csv file is, or how to handle the jargon on the electricians forum. You might think that that they are all sorts of things, but they are nevertheless probably the majority at this point in time. And it is for/because of them I think these ‘little issues’ about PV really do need attention. As Steve said, people on this forum will spot the problems and know where to go for help.


Rogerhoward, I'm glad you thought about the solar farm as a good place to assemble this sort of stuff, I'm thinking along very similar lines…. I'm pretty sure we could come up with something here





Edited Britta (Feb. 6, 2014 10:13:00)

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#9 Dec. 12, 2014 21:03:08

Toberwine
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Up to 35% of PV Systems are underperforming

I thought people might be interested to hear of my situation with regards to my ability to directly compare two sites both within my control.

I now own two sites within about 10 miles of each other.

One is on a roof beside my new house which I hope to move into early next year. It has been grid connected since May and I have been aware of more than one incident when the RCD tripped out during high winds. My installer has now said he will replace it with a (higher?) rated one.

The other is a ground mounted site which is quite remote from habitation at some risk of vandalism, so I have had a Logic Energy GSM enabled data logger installed. If there is any wilful or accidental damage, or a fault, I should know about it pretty quickly as I can check the performance online.

The issue of under-performance had concerned me due to the above issue, ie. that the system might be out of action for a period before it is noticed. Now that I have two sites (with the same make of panels but a different model) I will also be able to see how they compare with each other in terms of outright performance. This is already highlighting large differences.

The caveat to this is that I am not measuring actual solar irradiation at either site so any comparison will be subject to possible differences in weather conditions which may or may not be significant over the long term. The sites are at markedly different elevations and terrains so it is plausible that the solar irradiation is different.

I have already noticed large differences in the specific outputs from the two systems now that the second one to be commissioned has been on stream for one week. Arithmetically I would expect the 50kWp ground mounted system to exceed the output of the roof mounted 20kWp system by about 2.5x. After the first six full days of operation the difference is 33kWh versus 128kWh, a factor of almost 4x. Apart from the vagaries of the weather at the two sites, at the moment the only explanation I have is that the 20kWh array tripped during high winds this week, although it was probably only off for a few hours, and the 50kWh array is comprised of a different model of panel.

I will of course continue to monitor the relative outputs and update the Microgen database, it will be very interesting to see how things pan out over the next few months.

Edited (Dec. 12, 2014 21:03:08)

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