Green Building Forum - Poor performing PV systems, system or weather? Mon, 17 Aug 2026 02:58:59 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 Poor performing PV systems, system or weather? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139379#Comment_139379 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139379#Comment_139379 Tue, 13 Mar 2012 20:09:06 +0000 SteamyTea Thoughts, anecdotes or data welcome.
Thanks]]> Poor performing PV systems, system or weather? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139384#Comment_139384 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139384#Comment_139384 Tue, 13 Mar 2012 20:18:53 +0000 pmusgrove Poor performing PV systems, system or weather? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139385#Comment_139385 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139385#Comment_139385 Tue, 13 Mar 2012 20:19:48 +0000 cbatjesmond http://www.ccandc.org/cgi-bin/pv?START=20120301&END=now
Of course (1) these months are 1/5 and 1/4 of the best months and (2) I rarely get what the PVGIS thinks I oughta.
December 2011 was also my best December but at 30kWh nothing at all to boast about.

ETA: I've just updated this page with monthly production for 2010 and 2011 also courtesy www.bdpv.com.
(And fixed spelling :0)]]> Poor performing PV systems, system or weather? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139388#Comment_139388 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139388#Comment_139388 Tue, 13 Mar 2012 20:26:28 +0000 DamonHD
Rgds

Damon]]> Poor performing PV systems, system or weather? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139390#Comment_139390 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139390#Comment_139390 Tue, 13 Mar 2012 20:31:11 +0000 SteamyTea
Chris, forgotten about your data, I shall book mark it. Have also forgotten the size of your system.]]> Poor performing PV systems, system or weather? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139392#Comment_139392 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139392#Comment_139392 Tue, 13 Mar 2012 20:48:27 +0000 cbatjesmond Posted By: SteamyTeaSomerset may be brighter, nearer the drought, I have only looked at my end so far, slowly working my way up. Come to sunny Tyneside :-)

Have also forgotten the size of your system.
Full details should be on the page linked from the second graph. But it's (only) 1.72kWp.

I do like the BDPV site even though I begrudge having to type the numbers in by hand:

* the PVGIS estimate gives an independent benchmark of sorts.

* they facilitate comparison between users (I think I suffer compared with those nearest me from having a small system, with little economy of scale).

* when you do compare, they automatically scale the values so that you see what the other installations would have achieved at your site.]]> Poor performing PV systems, system or weather? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139394#Comment_139394 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139394#Comment_139394 Tue, 13 Mar 2012 21:32:23 +0000 SteamyTea Shall have a play tomorrow, just sorting out some charts to pop up.
 
These are for Plymouth, the 1983-2005, min and max are from the Nasa/Noaa site.
 
 ]]> Poor performing PV systems, system or weather? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139395#Comment_139395 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139395#Comment_139395 Tue, 13 Mar 2012 21:35:07 +0000 Ed Davies Poor performing PV systems, system or weather? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139396#Comment_139396 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139396#Comment_139396 Tue, 13 Mar 2012 21:36:54 +0000 SteamyTea ]]> Poor performing PV systems, system or weather? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139400#Comment_139400 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139400#Comment_139400 Tue, 13 Mar 2012 22:00:02 +0000 skyewright
Here, insolation has been way down on PVGIS's view of average, both as measured by PV production and by weather station pyranometer. February's PV was 68% of PVGIS's estimate. The pyranometer only managed 60%.

January was not too bad overall, mainly because a few very good days at the end of the month dragged the average PV up. On the 21st it was still down at 64% of "average", by the 26th that had improved to 75%. Given that, finishing at 92% seemed not so bad!

December only managed 62% PV.

So yes, it's been a cloudy few months, and March is continuing in the same vein (though we did have a couple of good days just over a week ago :bigsmile: ).]]> Poor performing PV systems, system or weather? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139408#Comment_139408 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139408#Comment_139408 Tue, 13 Mar 2012 23:55:23 +0000 Jeff B
Our local Met Office weather station (Abersoch) recorded just 25 hours of sunshine in December - the lowest since 1942! January had 59 hours (average for January = 57). February had 68 hours (average = 78).

Our PV system (3.9 kWp) generated 33 kWh in December, 54 kWh in January and 103 kWh in February. The total since April last year is 2758, so the three months December, January and February generated just 7% of the total. And before someone says "what do you expect, it's wintertime" let me say that on the only two blue sky days we've had this month so far (4th and 5th March) we generated 10.1 and 12.8 kWh respectively! Today and yesterday, both overcast days, managed 1.7 kWh each.]]> Poor performing PV systems, system or weather? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139418#Comment_139418 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139418#Comment_139418 Wed, 14 Mar 2012 07:36:22 +0000 Beau
3.76 kW system
We produced 198kWh between installation at the end of October -1st of February this is 52% of PVGIS estimate and by comparison we have produced 162kWh in the last 2 weeks.]]> Poor performing PV systems, system or weather? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139420#Comment_139420 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139420#Comment_139420 Wed, 14 Mar 2012 07:49:42 +0000 SteamyTea My feeling is that it has been dull, but it is easy to forget previous years.]]> Poor performing PV systems, system or weather? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139422#Comment_139422 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139422#Comment_139422 Wed, 14 Mar 2012 08:30:31 +0000 Beau
I think it is weather. I have lived here for 36 years and I have always been able to handle our wet cloudy winters but this year really has got to me like never before. I know this is totally unscientific but it is my view. The other awful year I think was 2000 when we had 100 consecutive days of rain but I think the sun came out between the rain..

I have noticed that my parents PV system that is at 15 degrees has percentage wise out performed our system at 36 degrees in the cloudy weather. I presume the light gets refracted down vertically so in these conditions a 0 degrees system might be best?]]> Poor performing PV systems, system or weather? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139429#Comment_139429 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139429#Comment_139429 Wed, 14 Mar 2012 09:42:01 +0000 skyewright
Month 2011 as % of PVGIS
Jan 109%
Feb 94%
Mar 76%
Apr 91%
May 74%
Jun 94%
Jul 108%
Aug 88%
Sep 91%
Oct 75%
Nov 92%
Dec 67%
Year 89%

Month 2012 as % of PVGIS
Jan 84%
Feb 60%

Looking at the 1m soil temp, the minimum this year has been 6.0C, and the temp was only below 6.5C for about 3 weeks. Minimum last year was 5.5C, and it was at that level for 2 months (and below 6.5C for approx 4 months).

Edit: 1m temp is currently (i.e. 14th March) at 7C. In 2011 that wasn't seen till the start of April.

HDD for Jan & Feb have been about 0.5HDD/day down (i.e. warmer) compared to 2011. The Jan & Feb kWh/HDD/day figures were slightly up :cry:; I think that is probably at least partly down to lack of solar gain - we may not get much sun here in the NW even in a good year, but what there is arrives at a low angle so it penetrates well into the house? Another factor is probably that getting the storage heating charge regime right is always that bit harder when temps are at the warmer end of the "heating on" range.]]> Poor performing PV systems, system or weather? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139433#Comment_139433 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139433#Comment_139433 Wed, 14 Mar 2012 09:57:45 +0000 Jeff B
Month Sun (hrs) Aver* Max* Min*
Dec 2007 74 50 88 25
Dec 2008 74 50 88 25
Dec 2009 69 50 88 25
Dec 2010 79 50 88 25
Dec 2011 25 50 88 25

Month Sun (hrs) Aver* Max* Min*
Jan 2007 58 57 98 24
Jan 2008 55 57 98 24
Jan 2009 91 57 98 24
Jan 2010 86 57 98 24
Jan 2011 81 57 98 24
Jan 2012 60 57 98 24

Month Sun (hrs) Aver* Max* Min*
Feb 2007 88 78 133 44
Feb 2008 133 78 133 44
Feb 2009 56 78 133 44
Feb 2010 101 78 133 44
Feb 2011 68 78 133 44
Feb 2012 68 78 133 44

*1942 – date

[Please excuse variations in column widths - can't seem to copy & paste a table here?].

As can be seen Dec 2011 had the lowest number of sunshine hours since 1942, Jan 2012 was about 5% above average (previous three January’s all well above average) and Feb 2012 was about 11% below average. (Previous February’s show huge variations e.g. Feb 2008 figure was the highest since 1942 at 170% of average and Feb 2009 was only 70% of average).

So, yes I concur with ST and Beau - this winter has been duller indeed.

On the plus side, whilst we haven’t had those cold, crisp sunny days this winter, at least it has been incredibly mild and hence I expect our wood pellet consumption to be significantly down this winter compared to the last two!]]> Poor performing PV systems, system or weather? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139451#Comment_139451 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139451#Comment_139451 Wed, 14 Mar 2012 11:54:32 +0000 SteveZ
Given that 3/4 of the system faces East and 1/4 South, both on a 30° inclination, and the South is shaded late in the day by the ridge, I am pleased so far with the figures. It is a SolarEdge system, so is unlike most of the others reporting, and will be fascinating to see if the extra expense was worth it :confused:]]> Poor performing PV systems, system or weather? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139458#Comment_139458 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139458#Comment_139458 Wed, 14 Mar 2012 13:03:37 +0000 pmusgrove Poor performing PV systems, system or weather? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139475#Comment_139475 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=139475#Comment_139475 Wed, 14 Mar 2012 14:20:54 +0000 SteveZ Poor performing PV systems, system or weather? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=141337#Comment_141337 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=141337#Comment_141337 Sun, 01 Apr 2012 17:41:35 +0100 cbatjesmond Posted By: SteamyTeaSo it seems that it is weather. Shall have to see if I can find more information.
My feeling is that it has been dull, but it is easy to forget previous years.
Following my best ever December, January and February: ta-dah, my best ever March -- http://www.ccandc.org/cgi-bin/pv?START=end-1w&END=now" > even beating the PVGIS estimate.]]> Poor performing PV systems, system or weather? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=141706#Comment_141706 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8794&Focus=141706#Comment_141706 Wed, 04 Apr 2012 22:05:33 +0100 Jeff B
Below please see graph of PV output from our system for the month of March. Spot the sunny days! Nothing wrong with the system me-thinks!]]>