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General: The British "summer" vs PV output?

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    •  
      CommentAuthorDamonHD
    • CommentTimeJul 22nd 2012
     
    That's how I manage to get so much PV on such a small house! B^>

    Rgds

    Damon
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 1st 2012
     
    1st August, and guess what, it is raining.
    Down here we call it the 'Monsoon Season', everyone else calls it 'Summer Holiday in Cornwall'.

    Nearly 3mm of rain and a solar peak of 200W/m^2.

    Now who invented the term 'Happy Campers' :bigsmile:
    • CommentAuthorJoiner
    • CommentTimeAug 1st 2012
     
    Billy Butlin. :cool:
    • CommentAuthorJeff B
    • CommentTimeAug 6th 2012
     
    PV data for April to July:

    April 314 kWh (down 19% on last April)
    May 459 kWh (up 3% on last May)
    June 344 kWh (down 30% on last June)
    July 404 kWh (down 2% on last July)

    Location: west Pembs. 3.9 kWp system.
    • CommentAuthorSteveZ
    • CommentTimeAug 6th 2012
     
    PV output figures April to July from inland North Cornwall.
    Solar Edge system with 3kWp East, 1kWp South

    April 360 kWh first year of operation, so nothing to compare with
    May 492 kWh
    June 399 kWh
    July 461 kWh July had a day minimum of 5kWh and a Max of 26.8 kWh - variable weather or what!
    • CommentAuthorJeff B
    • CommentTimeAug 6th 2012
     
    SteveZ - those are very good figures for a system that is predominantly east facing (IMO)! My system is facing SSE and not that far from you as the crow flies, as they say. The total for those 4 months for your system was 1712 kWh and for mine 1521 kWh (a 12.5% difference). I am beginning to wonder if my panels are underperforming for some reason, as folk who live only about 4 miles from here get consistently higher outputs than me. N.B. just from random comments at the moment - no hard data.

    The highest output for our system during April - July this year was 26.4 kWh (June 9th) and the lowest was 1.3 (April 29th). Highest in July was 24.9 and the lowest 1.8. Variable .... you bet!
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 6th 2012
     
    Where are you in the country Jeff?
    • CommentAuthorJeff B
    • CommentTimeAug 7th 2012
     
    <blockquote><cite>Posted By: SteamyTea</cite>Where are you in the country Jeff?</blockquote>

    West Pembs, near St. Davids.
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 7th 2012
     
    Yes, I remember, so should be a bit lower than Steve's then, but not much.
    Have you checked the obvious, shading, both strings connected (if on two strings), inverter the correct size for system and correctly set up.
    • CommentAuthorJeff B
    • CommentTimeAug 7th 2012
     
    <blockquote><cite>Posted By: SteamyTea</cite>Yes, I remember, so should be a bit lower than Steve's then, but not much.
    Have you checked the obvious, shading, both strings connected (if on two strings), inverter the correct size for system and correctly set up.</blockquote>

    SteamyTea - we have no shading problem. Our system uses Enecsys microinverters (one per panel) so I can tell instantly if any particular panel has significantly different output to the others. I Can only presume the system is correctly set up.

    I notice that SteveZ's location is inland Cornwall whereas we are quite close to the coast (about 2 - 3 miles) and on a hill, which means often we tend to get cloudy conditions whereas at the same time on the coast itself it can be sunny e.g. at St.Davids. I am no meterologist, but my sister who is, tells me that our location is just the type for encouraging clouds to form. This would explain why people who live on the coast get higher PV outputs than us on any given day but not those living in/around our village. I need to contact those closer to us really and see if they are agreeable to comparing PV data with one another.
    • CommentAuthorMikel
    • CommentTimeAug 25th 2012
     
    I've joined this forum because I've been following this topic and wanted to ask a question.

    I have a 3.84kwp system, south facing, Fronius inverter and datalogger. I've noticed that my generation meter gives a reading of approx 96% of the data logger reading for the day/month.

    Are people quoting figures here for their generation meter or from an installed datalogger? I'll happily add my figures and state whether they are from the datalogger or generation meter.
    • CommentAuthorSteveZ
    • CommentTimeAug 25th 2012
     
    Hi Mikel My figures quoted above are those taken from my results page on the Solar Edge website, as SE log all the output figures at around 5 minute intervals, so I can get the daily, monthly and annual figures instantly. My generation meter, interestingly, logs a higher figure by a small percentage. This is the figure on which the FIT payments are based.

    Jeff B We are just off the edge of Bodmin Moor, so if there is any mist, fog, rain,snow around, we tend to get it :-)

    If Enecsys had been able to deliver the goods in time, I would have had their system too. I was waiting for the dual inverter to become available, but I ran out of time and patience! I suppose the losses in both our systems must be higher than those of a more conventional 1 or 2 string and inverter system, but the gains from each panel performing at its best might overcome that disadvantage. I like the way you can easily check that all the panels are working properly.
  13.  
    <blockquote><cite>Posted By: Mikel</cite>
    I have a 3.84kwp system, south facing, Fronius inverter and datalogger. I've noticed that my generation meter gives a reading of approx 96% of the data logger reading for the day/month.</blockquote>

    With my 1.72kWp and a Fronius IG-15, my generation readings for the last few months as % of the inverter readings are 90.7, 93.1, 91.3, 92.9, 89.4, 91.6 -- so you're doing well (at least compared with me :-) Though I'm sure they have been higher -- I only started keeping the inverter readings this year.

    I've been assuming a/ a fixed inverter overhead with a small system, b/ possibly an undersized cable between inverter and generation meter!

    I use the generation meter as the "true" value: that's the meter that's been calibrated (I hope!).

    -- Chris
    • CommentAuthorJeff B
    • CommentTimeAug 25th 2012
     
    <blockquote><cite>Posted By: SteveZ</cite>Hi Mikel My figures quoted above are those taken from my results page on the Solar Edge website, as SE log all the output figures at around 5 minute intervals, so I can get the daily, monthly and annual figures instantly. My generation meter, interestingly, logs a higher figure by a small percentage. This is the figure on which the FIT payments are based.

    Jeff B We are just off the edge of Bodmin Moor, so if there is any mist, fog, rain,snow around, we tend to get it :-)

    If Enecsys had been able to deliver the goods in time, I would have had their system too. I was waiting for the dual inverter to become available, but I ran out of time and patience! I suppose the losses in both our systems must be higher than those of a more conventional 1 or 2 string and inverter system, but the gains from each panel performing at its best might overcome that disadvantage. I like the way you can easily check that all the panels are working properly.</blockquote>

    SteveZ: my system does the opposite i.e. my generation meter consistently gives readings which are, on average, about 3% lower than the Enecsys system indicates. Enecsys were very slow with the single microinverters too! I could have had my system installed months earlier than I did but I hung on. I hope they have improved the supply situation by now. From what I was told whilst they were brilliant academics, their understanding of sales and marketing (at least in the UK) was somewhat less! I believe they switched production from Poland to China which caused additional delays. The microinverter system is supposed to increase the energy "harvest" so heaven knows what my panels would be generating using a conventional single inverter.

    Yes, the ability to monitor the performance of each panel in real-time is a very useful feature. The only snag was that I had to buy a wireless router (which I don't need for anything else). Then for some reason the system used by my ISP at the time was incompatible with the Enecsys gateway device so I had to change ISP as well which was all a bit of a hassle really. An unexpected bonus was that the Broadband speed with the new ISP was considerably faster than that from the old one!
    • CommentAuthorJeff B
    • CommentTimeAug 25th 2012 edited
     
    Last August we generated 333 kWh and the total for this August I predict will be 307, unless we get wall-to-wall susnhine for the next 7 days of course. So not too bad considering the weather we've been having. But then last August was pretty bad too, with much lower output than any one of the preceding months April, May, June or July!

    Regarding Enecsys, I should have added that their technical people were very helpful in trying to sort out the compatibility issue with my original ISP (the ISP was not that helpful!) but we just could not get around the problem, hence I had to change ISP in the end.
    • CommentAuthorSeret
    • CommentTimeAug 26th 2012
     
    Posted By: Mikel
    I have a 3.84kwp system, south facing, Fronius inverter and datalogger. I've noticed that my generation meter gives a reading of approx 96% of the data logger reading for the day/month.


    I've got a Fronius inverter, and there's a fair old difference between what it logs and what the generation meter says. I go off the generation meter.

    Incidentally, have you ever managed to get your datalogger to download to a PC using their software? Mine just won't play ball, even asked the installer to have a look at it and they came away stumped. It seems to connect over USB but won't actually download the logs.
    • CommentAuthorMikel
    • CommentTimeAug 26th 2012
     
    Thanks for the feedback.

    I too considered using the Enecsys micro inverters but there was a problem last year with Western Power not permitting grid connection for a time. Since Fronius offered a relatively cheap upgrade to 20 year warranty, I went with that. I also went for Sanyo HIT panels. Much more expensive but I took the view that they would be likely to be better performers over the 20-25 year period.

    I log the daily microgeneration meter reading into a spreadsheet and those are the figures below for the Jan-July period. I also calculate the percentage of the PVGIS estimate and record the monthly sun hours for Camborne from the Met Office (I live a few miles from Camborne). I calculate the percentage of the sun hours compared with the average of the 30 year Met Office data. Not the same direct comparison with PVGIS as the total insolation is used for the PVGIS estimate but direct sunshine is the major factor in PV output. We would appear to be down about 180 hours of sun over the Jan-July period, with June being especially poor.

    (Fingers-crossed this format displays OK)

    month production(kWh) %PVGIS %camborne sun avg

    January 93.1 84.6% 87.5%
    February 168.9 97.1% 91.1%
    March 373.6 127.5% 129.6%
    April 399.8 94.3% 81.8%
    May 496.5 103.0% 81.9%
    June 387 85.4% 51.2%
    July 466.1 96.5% 87.0%

    PS. The datalogger uploads to Fronius solar web. I use Macs at home and wouldn't even try to directly download any data from the datalogger.
    • CommentAuthorJeff B
    • CommentTimeAug 26th 2012
     
    Mike1 - your total output for Jan to July is 423 kWh more than mine for the same period. The largest difference for a single month is March where you generated 373 kWh and we managed 282 kWh.
    • CommentAuthorMikel
    • CommentTimeAug 26th 2012
     
    Jeff,

    Are you able to get some local sunshine data for this year and past years?

    Mike
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 26th 2012 edited
     
    I have loads for your area MikeL, what resolution does your data go to and which side of Carn Brea are you
    • CommentAuthorMikel
    • CommentTimeAug 26th 2012
     
    SteamyTea. I get the sunshine data from the Met Office but I would be interested in insolation data so I can compare directly with the PVGIS estimated output. I don't think a high degree of precision in the data is required as I suspect that there are likely to be local weather variances between our location and the data source.

    I live west of Camborne and inland from Hayle, always seems to be sunnier.
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 27th 2012 edited
     
    Month,kWh/m^2 (Horizontal Plane),Temp °C
    1,240,8.6
    2,270,6.5
    3,327,9.8
    4,390,8.5
    5,417,12.2
    6,439,13.8
    7,444,15.4

    This is horizontal plane so gets more hours of daylight and is less affected by cloud/scatter/direction
      Cam Solar Production.jpg
    • CommentAuthorMikel
    • CommentTimeAug 27th 2012
     
    SteamyTea. Thank you.

    these are the figures from the PVGIS-classic estimate (kWh/ sq/m):

    Jan 35
    Feb 56
    Mar 96
    Apr 143
    May 165
    Jun 158
    Jul 169

    Smaller by a factor of approx. 0.37. Any idea why the difference?
    • CommentAuthorJeff B
    • CommentTimeAug 27th 2012
     
    Posted By: MikelJeff,

    Are you able to get some local sunshine data for this year and past years?

    Mike


    Yes I can. The Met Office have sunshine data (plus temperature etc.) for Aberporth (which is not too far from here) going back to 1942. I have transposed the raw data into Excel and therefore can calculate min, max and average with ease. I have used the data to try and cheer myself up from time to time by reading that there have been much worse months in the last 70 years, although I did find that Dec 2011 had the lowest number of sunshine hours since records began in 1942!

    The monthly variation is, in fact huge, year on year, so hopefully over the next 24 years it should be a case of swings and roundabouts as far as our solar PV generation is concerned.
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 27th 2012 edited
     
    Posted By: MikelSmaller by a factor of approx. 0.37. Any idea why the difference?

    Just variance and mine are for a horizontal plane, panels tend to be fixed away from the sun a lot of the time, so loose out in the summer a bit when the sun rises in the NE and sets in the NW. PV GIS takes this into account to a certain extent but only for a large geographic area, i.e. most of the West Country is treated the same. Why I asked which side of Carn Brea (though you are west of that ridge) you are on as that makes a huge difference (Week before last I was climbing near Pendeen in a T-Shirt, went off to Rinsey and it was chucking it down, 1 hour, 5 miles South and 13 miles East different. Penwith (most of Cornwall) has to be treated as a small island and is more effected by the wind direction and ocean temperature than anything else.
    • CommentAuthorMikel
    • CommentTimeAug 27th 2012
     
    SteamyTea. Sorry that I may be missing the point but I still don't see how your figures are almost three times the PVGIS figures.

    See, for example, http://contemporaryenergy.co.uk/solarmap.htm
    • CommentAuthorJeff B
    • CommentTimeAug 27th 2012
     
    Mike1: I've just had a look at the sunshine figures for my area (using data from the nearest Met Office weather station to me, at Aberporth):

    April - 113.3 hours (lowest since records began in 1942). Average for April = 171.
    May - 214 hours (about average)*. Average for May = 212.
    June - 143.9 hours (well below average - 70%). Average for June = 206.
    July - 139.4 hours (well below average - 74%). Average for July = 189.

    Now I've depressed myself again, but, still looking forward to a stunning autumn though!

    *Interesting how we all thought May was fantastic, yet apparently we had only the average amount of sunshine!
    • CommentAuthorMikel
    • CommentTimeAug 27th 2012
     
    Jeff, I checked the total sunshine figures for the year to date. 908 for Camborne and 902 for Aberporth. The average for Camborne is about 1080 for Jan-Jul.

    Definitely not going to make the PVGIS estimate this year.
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 28th 2012
     
    Mikel
    My figures are for sunlight power, not for PV output, they are then multiplied by the duration of daylight to arrive at the kWh/m^2 figure. A PV system will not convert 100% of the light to electricity, more likely around 15%, then there are inverter and thermal losses.
    • CommentAuthorMikel
    • CommentTimeAug 28th 2012
     
    SteamyTea

    This illustrates one of the difficulties with message board communication that a phone call or face-to-face meeting sorts out.

    The PVGIS figures I quoted are for an average from a 10-year database made up from measured and calculated figures. For example, the figure for the July average solar insolation for my area is 169 kWh/sq.m. You quote 444 kWh/sq.m for July.

    Since, it is very unlikely that we have had such an increase in solar irradiation this July, I suspect we are comparing different things.

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