#1 Dec. 13, 2013 20:08:00

Roger Lowman
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Hi:  I'm wondering if anyone out there can help me.  I have an array of 10 panels (2.50 total) set out landscape in 4 rows, 1 (at the top), 2, 3, 4.  The estimate performance for the year was given by the supplier as 2108, and this fits in with the sort of figures that calculators on this site provide, so I shall use it.





The installation was 24 July 2012, and for 2 months the performance came in about 9% above the (seasonally adjusted) estimate.  There was then a problem with a leaking roof underneath the panels, and the installers came to do a repair (came 3 times, actually).  From that point, about the end of September 2012, the (seasonally adjusted) performance collapsed to about 70% of prediction, and the figures for the year ending 1 October 2013 were 1617, and for the year ending 1 December 2013 1602:  much the same.





I have made comparison with near neighbours with similar solar panels and making allowance for size of systems and aspect the same poor performance in mine is evident.  There is also an interesting thread in this forum ‘A Record Month’, which gives a number of performance records for July 2013, and these tell the same story of about 70% performance by my system compared with other systems.





When the roof repairs were done in September 2012 the panels were disconnected and physically moved.  Does anyone have the technical knowledge to suggest whether there are sorts of thing that could have happened at that point to reduce the performance of the panels to circa 70% of predicted, AND of actual performance during the months before the repair?  The installers are dragging their feet (in my view), and it would help of I could point to possibilities with some authority!  The system is single string, by the way.





Will be very grateful if anyone can help me, either via this thread, or in personal email or telephone call.





Roger Lowman





Edited Roger Lowman (Dec. 13, 2013 20:08:00)

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#2 Dec. 13, 2013 21:47:00

rogerhoward
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Hi Roger


Have you tried comparison between the monthly Met Office ‘Anomaly’ maps for your location, and your percentage variation from predicted generation? In the previous ‘General Discussion’ thread to this, Steve posted a very enlightening graph for the year showing very close correlation between the two, albeit using variance against PVGIS predicted generation rather than the SAP predicted generation that our installers all had to provide us with.


But even this might not correspond.


Has the 30% performance loss been pretty constant since the end of Sept. 2012?


What is your directional orientation? (Steve's is South.)


Could there be any potential shading issue outside the summer months? (Steve doesn't have any as far as I know.)


Is there no discernable pattern to the variances that comes out from para. 1?


Another Roger







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 (Dec. 13, 2013 21:47:00)

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#3 Dec. 14, 2013 21:37:00

Roger Lowman
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Hi Roger


Thank you for your interest.


Yes, I've used the Met Office ‘Anomaly’ stats, and they are helpful in explaining variations, for example last July, and i think this is good evidence to use.


Tes, the 30% underperformance has been pretty consistent.  in July it was close to target, but then other people were recording performances 50% better than mine.  as are my near neighbours.


My aspect is SSW (very accurate): and my latitude is Winchester.  Yes, there is a little shading from September, but not enough to explain the underperformance: and the shading was taken into account in the 2108 forecast.


At the heart of the problem is the fact that my supplier (to whom I paid money) went out of business (well-known national brand) and I have to deat with the de facto installer who actually did the work and showed up at the house.  He may well have reasons to be pissed off himself: has he been paid?  Apparently, however, he is responsible legally,  But is it a problem with the installation–or the re-installation?  And just what could go wrong with a system previously functioning well because a roof repair was done, involving moving the panels around a bit on the roof and putting them back?  Is it the connections in the system?  Or have some of the panels gone sick?  i'd love a comment from someone who has a bit of technical knowledge here.  Over the underperformance:  I have lots of figures logged, and they all point the same way.


Thank you for your suggestions.





Roger





Edited Roger Lowman (Dec. 14, 2013 21:37:00)

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#4 Dec. 15, 2013 09:44:00

rogerhoward
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Yes you do seem to need some technical input. Sorry that I can't help myself. It's interesting what you've found regarding liability - I expect a lot of our installers have ceased trading since our installations.







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 (Dec. 15, 2013 09:44:00)

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#5 Dec. 16, 2013 13:19:00

morrisok
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Which inverter is attached to the panels?  Some of the inverters allow you to get information directly from them like the Sunnyboy ones via bluetooth.


It sounds to me like you might have a problem with one or more panels and it is causing the whole string of panels to be affected.  Similar to shading issues.  There are lots of websites explaining shading issues, something to do with the “Maximum Power Point”


I'm not technical in the solar industry though but thought it might give you somewhere else to look.


Good luck.





Kevin 3.92KWp 12x 327W E20 SunPower panels Sunnyboy 4000 inverter, facing ~south, no shading issues. Location: Sussex, URN 131 http://pvoutput.org/intraday.jsp?id=12216sid=10156







Kevin

URN 131, 3.92KWp 12x 327W E20 SunPower panels Sunnyboy 4000 inverter, facing ~south, no shading issues. Location: Sussex, http://pvoutput.org/list.jsp?userid=12216

Edited morrisok (Dec. 16, 2013 13:19:00)

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#6 Dec. 16, 2013 14:16:00

SteveRogers
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Hi Roger,


It sounds to me as if the installer has damaged a panel while moving them or a poor connection has been made with the rewiring.  Maybe some dirt got in.


It only takes one panel in a string to be behaving poorly to get this sort of reduction.  And it only takes one or two of the many cells that make up each panel to be faulty - maybe a crack or a scratch.


Can you get a good look at the panels with binoculars or a spotting scope if you can't get up to the roof level?


I think most inverters will tell you the instantaneous DC volts, amps and watts from the whole string.  You can compare the DC string voltage (divided by the number of panels) with the voltage at Pmax (Vmp) from your panel's data sheet.  I assume you know the make and model.  It should be on your MCS certificate.


Vmp is usually in the range of 28-30 volts per panel and is fairly independent of light level once you have reasonable production going on.  However, I don't know how indicative it is of a fault. The amps and watts will vary with light level.


If you are having trouble getting the installer to cooperate you might consider complaining (or threatening to complain) to the Renewable Energy Assurance Ltd (REAL) assuming they belong to this.


Hope something in the above is helpful.


Steve








Edited SteveRogers (Dec. 16, 2013 14:16:00)

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#7 Dec. 17, 2013 10:50:00

SteveRogers
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Just a couple of points from Roger Howard's reply.


I didn't get a monthly breakdown of expected production based on SAP - just an annual figure.  This is a bit lower than my PVGIS predictions.  This year my system has exceeded PVGIS by about 13% (and SAP by 16%).  I don't think there's anything special about my system or location/microclimate so I'd expect most users to be in the same ball park.  Roger Lowman definitely has a faulty system since the roof repairs.


I do have some shading issues. I have two strings either side of a dormer window plus a big tree to the WSW.  Fortunately, during the core production time of 10am to around 3pm there's no shading.


Hope you get it sorted soon Roger L.


Steve





Edited SteveRogers (Dec. 17, 2013 10:50:00)

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#8 Dec. 17, 2013 11:25:00

Roger Lowman
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Steve:  thanks for your input.  I didn't have a monthly breakdown from my supplier, but the bumf included a graph of seasonal variation (expected production for each month per Kwp), and that is what I have applied.  Happy to share it with you.





Roger





Edited Roger Lowman (Dec. 17, 2013 11:25:00)

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#9 Dec. 17, 2013 11:29:00

Roger Lowman
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Hi Steve


Useful stuff here:  I'll work through it.  What is particularly is your observation that a relatively small bit of damage can mess up the whole system.  I nay have to pay for an independent inspection of the array.


Cheers


Roger 





Edited Roger Lowman (Dec. 17, 2013 11:29:00)

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#10 Dec. 17, 2013 11:32:00

Roger Lowman
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Thanks.  My inverter is a Sunnyboy, so I'll follow that up.  Ve ry useful.


Roger





Edited Roger Lowman (Dec. 17, 2013 11:32:00)

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