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Renewable Energy: Output from PV panels

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    • CommentAuthorSeret
    • CommentTimeOct 14th 2013 edited
     
    I'm running right on 100% of predicted VH.

    Earlier in the year was a bit sad, but we had a great patch in the middle of summer that's made up for it. Last two weeks have been slightly above average, the three before that were awful (one week was as low as 54% of predicted). But by this time of year it's all over bar the shouting though, so I'm happy.
    • CommentAuthorskyewright
    • CommentTimeOct 14th 2013
     
    Posted By: Viking HouseSo how many kWh are people harvesting from their PV arrays?
    Is this more or less than expected?

    It varies, like the weather - as you might expect. :smile:

    We have 3 years of data now & so far the PVGIS figures that we looked at before we started seem perfectly reasonable. Individual months can vary considerably from the average (especially so in the winter months). So far. overtime. it smooths out to something a bit above the PVGIS figure, but their figures are based on 12 years of data (IIRC), so there is time yet...
    • CommentAuthorbillt
    • CommentTimeOct 14th 2013
     
    Last year was 4.6% above the PVGIS classic estimate, this year looks as if it will be at about the PVGIS estimate. Even if I don't get anymore energy it will only be 6% down.
  4.  
    How many kWhs/m2.annum are being harvested? What the efficiency of the array?
    How much is a 4kWp array fitted costing at the moment in the UK?
    What needs to be considered when fitting an 8kWp array on the roof of a house.
    • CommentAuthorbillt
    • CommentTimeOct 14th 2013
     
    My system generated 3,400 kWhr last year, which works out at about 125 kWhr per sq.m. p.a.

    Panel efficiency is about 15%, so system efficiency should be just over 14%. You can get panels up to about 20% efficiency, but there will be a premium to pay.

    I'd guess £5-6,000 for a simple system installed by MCS registered installers. But you can get the bits for less than that if you don't need to use an accredited installer. I've bought all the bits (except the mountings) for an 11.7kW system for £8,500.

    I've seen one supplier offering a 4kW system for £3,500, although details are a bit sketchy.
  6.  
    Thanks Bill, Are there any issues with fitting an 11.7kWp system to the electricity supply in a normal house?
    Do you need bigger cables for example? Did you fit this on your roof or in the garden? Where will you fit the 11.7kWp system?
    • CommentAuthorjamesingram
    • CommentTimeOct 14th 2013 edited
     
    VH , in UK anything over 4kW need prior permission from DNO ( district network operator) as local transformer may require upgrade , at your expense . heard up to 6kWp generally no problems ,

    12kWp = approx. 76m2 = 48 x 1.6m2 panels at 250W each
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 14th 2013
     
    There has been a few issues with 2 3.68 kWp systems fitted in rural locations that have needed investigation. Quite a tricky calculation as there are two volt drops to take into account and the diversity.

    As for fitting PV into a new roof, look at fitting it flush, there are kits available.
    • CommentAuthorMikel
    • CommentTimeOct 14th 2013
     
    I recently enquired about adding 6kw to our 3.84 kw array. The DNO gave a verbal estimate for an upgrade to 3-phase supply of £10k for transformer upgrade and other items, plus 70m of trenching work to upgrade the cable plus VAT. A very effective discouragement!

    Depending on where you are in the country, you may get a better quote.
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 14th 2013
     
    It was close to you Mike that the DNO questioned what the company I worked for briefly were up to :sad:
    • CommentAuthorbillt
    • CommentTimeOct 14th 2013
     
    This system will be ground mounted to the west of our house and is going to be off-grid. Our supply would need up grading and the main aim is to become electrically self sufficient. Feeding into the grid won't do that. Unfortunately, the Sunny Island and batteries double the cost! The panel surface is 23M x 3.5M, so it's a big eyesore, but it's not visible from outside our property.

    The actual power limit is 16A per phase, which is about 3.6kW and the DNO can still refuse to allow connection if there are already nearby generation systems connected which are close to the local network capacity.
  12.  
    Thanks ST, I'm getting about 140kWh's/m2 of usable energy from large solar arrays designed primarily for Solar heating and costing about £100/m2.
    There's one guy in the South East of Ireland whose 16m2 PV array will delivery about 4200Kwh/annum (262kWh/m2) probably costing about £300/m2. Based on these figures I could probably get a 100m2 Passive House to Zero Energy with just 20m2 of PV-T.
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 14th 2013
     
    Would that 20m^2 of PV-T cope with the winter months, or is the idea just to be energy neutral?
    • CommentAuthorEd Davies
    • CommentTimeOct 14th 2013 edited
     
    Kinve 235 W panels from Navitron are £144.67 (incl VAT) and 1.64 m × 0.99 m.

    Area is therefore 1.62 m², output power 145 W/m² and cost £90/m². Using 850 hours production a year that would give 123 kWh/(m²·a).

    Still, unless you're short of roof space I don't see the point of thinking in terms of m² at all. It's W/£ that matter. Particularly, W/£ during the bits of the year when you most need energy.

    However, I suspect VH's panels are roof integrated so offset the cost of some of the roof cladding. Normal PV panels won't do that. Also they'll need mounting hardware and some sort of control gear if used for heating. Not sure if VH has included the pumps or whatever in his £100/m² for comparison.
    • CommentAuthorEd Davies
    • CommentTimeOct 14th 2013
     
    Posted By: billtThe actual power limit is 16A per phase, which is about 3.6kW and the DNO can still refuse to allow connection if there are already nearby generation systems connected which are close to the local network capacity.
    My understanding is that they can indeed tell you to turn your system off if it's causing problems. However, I think it's the case that the 16 A/phase is a right under the electrical supply quality regulations and that if their system can't cope with it then they have to do the fixes required at their expense so you can switch your system back on eventually. If you want to go over 16 A then they can charge you.
  16.  
    I need 5-6,000kWh to convert 100m2 Passive Houses to Net Zero, what's the cheapest system that looks well on the roof?
  17.  
    It used to be that the best value was buying from Germany not sure if that is currently the best option but from a quick look on ebay.de

    5.76kWp kit including panels, roof mounts, cable and Kostal 3 phase inverter is €7,200 inc. vat (+ del.)

    http://goo.gl/jjr86M

    How does that compare to UK prices? (€7,200 is approx. £6,200)
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 15th 2013
     
    Need a bit more information about the roof, but you are probably looking at a 7 to 8 kWp system. so at 300Wp per panel, that will work out at about 180Wp.m^-2 or up to 45 m^2.
    Then you have to allow for the fitting, so that will be an extra strip around the panels that you cannot use.
    That is purely for PV.
    If you went for some combined PV-T you could save a little bit of area, Trouble with the thermal side is that once your tank is 'full' you can't then export the extra energy.
    • CommentAuthorMikel
    • CommentTimeOct 15th 2013
     
    I estimate with the PV FiT that going for a large PV array is the cheapest option. That would change if the DNO requires a 3-phase upgrade. You could then consider combining PV and solar thermal on the roof and get some money back on the solar thermal from the RHI.

    ST correctly points out that you cannot export on the thermal side. However, if you have a large well insulated tank, you can store about two days of hot water for those dull days when the solar thermal does not give enough heat, and it doesn't take much energy to heat back up to 50C. You only need to boost the temp to 60C once a week to prevent legionella.

    WRT our DNO down here in the South West, it does appear that they are having some difficulty with the amount of renewables installed and that the local grid is nearing capacity. Maybe we will get some encouragement to invest in battery systems to use more of our PV generated supply at home.
    • CommentAuthorMikel
    • CommentTimeOct 15th 2013
     
    Just done a quick check on annual sun hours for our area:

    Oct 2011 - Sept 2013 1385 Electricity generated 3560 kWh
    Oct 2012 - Sept 2013 1502 Electricity generated 3788 kWh

    Thirty year average annual sun hours 1683. Just shows the variation in the weather and its impact on PV generation.
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 15th 2013
     
    There could now be a new normal.
    But the last two winters have been a bit abnormal.
    There is also the problem that sea surface temperature affects us greatly in the SW.
    I shall look at my figures and see how they correlate with yours
  22.  
    Posted By: MikelJust done a quick check on annual sun hours for our area:
    Oct 2011 - Sept 2013 1385 Electricity generated 3560 kWh
    Oct 2012 - Sept 2013 1502 Electricity generated 3788 kWh
    Thirty year average annual sun hours 1683. Just shows the variation in the weather and its impact on PV generation.

    Hi Mike, what size is your array? what do the 1385 and 1502 numbers mean, sun hours?
    Is this the yield/annum from your array? What's the efficiency?
    • CommentAuthorMikel
    • CommentTimeOct 16th 2013
     
    Hi VH,

    Annual sunshine hours, 1385 and 1502, taken from our nearest Met Office station (http://www.metoffice.gov.uk/public/weather/climate-historic/#?tab=climateHistoric)

    kWh figures are the annual generation figures.

    The array size is 3.84kw and is ground mounted. I have Sanyo 240HIT panels (module efficiency specification 19%) but being ground mounted panel efficiency is not really an issue. However, if you are constrained with space you could consider the more efficient panels.
  24.  
    Viking House
    So how many kWh are people harvesting from their PV arrays?
    Is this more or less than expected?

    Less! http://www.ccandc.org/cgi-bin/pv?START=end-7d&END=12:00_sunday#monthly2013

    :-/

    I put it down to
    a/ fixed overheads reducing overall efficiency
    b/ being at 55N
    c/ being ~10km from the (E) coast
    • CommentAuthorskyewright
    • CommentTimeOct 17th 2013
     
    Posted By: cbatjesmond
    Less!

    Judged against which estimate?

    I put it down to
    a/ fixed overheads reducing overall efficiency
    b/ being at 55N
    c/ being ~10km from the (E) coast

    PVGIS is based on quite fine grained analysis of 12 years (?) of satellite imagery & does well here (57N & <=2km from sea in 3 directions, on island off W coast).
    • CommentAuthorskyewright
    • CommentTimeOct 18th 2013
     
    I almost forgot about this...
    If you take a look at:
    http://bdpv.com/fiche_utilisateur_en.php?util=skyewright
    you can see graphs of annual & monthly production since installation in September 2010.
    • CommentAuthorcbatjesmond
    • CommentTimeOct 18th 2013 edited
     
    Posted By: skyewright
    Posted By: cbatjesmond
    Less!

    Judged against which estimate?

    PVGIS -- see the graphs down my page: I've only reached the PVGIS estimate two months in 4 years.
    Though I note http://www.bdpv.fr/fiche_utilisateur.php?util=cbatjesmond says
    ANNUAL LOSS IN COMPARISON TO THE OPTIMUM : 0.5% source PVGIS

    I meant to say above: this is only a 1.72kWp system, so I suspect the fixed overheads (inverter, loss in the 15+m run from inverter to generation meter) will be a larger proportion of mine.

    I also note that my system has much wider variations from year to year than yours shows.
    • CommentAuthorskyewright
    • CommentTimeOct 18th 2013
     
    Posted By: cbatjesmondI meant to say above: this is only a 1.72kWp system, so I suspect the fixed overheads (inverter, loss in the 15+m run from inverter to generation meter) will be a larger proportion of mine.

    Must be something like that. Most people seem to consider PVGIS at least slightly pessimistic.
    • CommentAuthorSeret
    • CommentTimeOct 18th 2013
     
    Posted By: skyewright
    Must be something like that. Most people seem to consider PVGIS at least slightly pessimistic.


    I've only got two years of data, but it's been bang on the money for me. Almost spookily accurate.
    • CommentAuthorJeff B
    • CommentTimeOct 20th 2013
     
    Agree - the PGVIS prediction is quite accurate.

    Our PV system (west Pembs, 3.9 kWp, SSE facing, 40 degree slope on roof) has been installed for 30 months. These are the data to date:

    April 2011 to March 2012: 2969 kWh
    April 2012 to March 2013: 2902 kWh
    April 2013 to Sept 2013: 2426 kWh.

    To forecast what the 12 months from April 2013 to March 2014 might achieve, by interpolating the data for the 6 months from October 2011 to March 2012 means we would achieve 3116 kWh and similarly using the 6 months from October 2012 to March 2013 means we would achieve 3202 kWh.

    Note: PGVIS prediction for our location is 3320 kWh/annum, so not far out! The summers of 2011 and 2012 were pretty grim here, so I was not surprised that we came in at about 90% of predicted. This year looks a lot better. I guess over the next 17 years or so, the average will be pretty close to the predicted output.

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