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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    • CommentAuthorphiledge
    • CommentTimeJul 4th 2022
     
    Posted By: renewablejohnPV panels need to be a minimum of 200 mtrs away from the power line.


    Theres a solar farm near us with HV pylons running down the side of it. OS map suggests its 100m or less away from the farm-ref SJ327717.

    I think you said youd got your panels, so you could set a couple up under the pylons and test the output on a sunny day. You could also ask your DNO
    • CommentAuthorneelpeel
    • CommentTimeJul 5th 2022
     
    My box section roofing for my solar shed is coming next week, so time to think about ordering the PV kit. I was thinking...
    PANELS
    - 9 x JA Solar JAM54S30-405/MR 405W (£168 TradeSparky)
    INVERTER
    - Solis S5-GR1P 3.6kW 4G Dual MPPT DC (£433 TradeSparky)
    OR...
    - Solax Power X1 Boost 3.6kW Single Phase Solar Dual MPPT (£270 new from Ebay)

    The dual MPPT will allow me to install a couple of the panels on a different orientation to catch the later sun.

    Any issues with the above? Or better options?

    My only concern is that I end up wanting to add battery storage later on and would then need a Hybrid inverter, but they are extra ££. Although if upgrading later I would probably be adding more panels and need a bigger inverter anyway.
    • CommentAuthorphiledge
    • CommentTimeJul 5th 2022
     
    Posted By: neelpeelAlthough if upgrading later I would probably be adding more panels and need a bigger inverter anyway.


    Check the spec of your inverter as theyll likely be able to take more DC PV input than the rated wattage. A solaredge SE3680H is rated at 3.68kw but can have up to 5.7kw of panel input connected, likely more if theyre facing different directions and not generating at peak output at the same time. Your panel potential output will be restricted to G98 limits but youll run at that limit for longer

    If youre able to collect from N Wales/Wirral area keep your eye on ebay as there may be some 405w JA panels coming up for sale
    • CommentAuthorneelpeel
    • CommentTimeJul 5th 2022
     
    Oh, and I fixed my 22 deg max angle issue...I had a bit of an epiphany that I don't need to stick to the roof angle. I now intend to mount the panels using 3mm x 30mm x 30mm angle iron (L-bracket). Something like the attached...
    I should be able to get any angle I want.
      Screenshot 2022-07-05 105913.jpg
    • CommentAuthorneelpeel
    • CommentTimeJul 8th 2022
     
    Posted By: philedge
    Posted By: neelpeelAlthough if upgrading later I would probably be adding more panels and need a bigger inverter anyway.


    Check the spec of your inverter as theyll likely be able to take more DC PV input than the rated wattage. A solaredge SE3680H is rated at 3.68kw but can have up to 5.7kw of panel input connected, likely more if theyre facing different directions and not generating at peak output at the same time. Your panel potential output will be restricted to G98 limits but youll run at that limit for longer

    If youre able to collect from N Wales/Wirral area keep your eye on ebay as there may be some 405w JA panels coming up for sale


    Indeed..the Solis allows for 5.4kW max input by the look of it. So potentially x4 extra 405W panels!

    On the panels, when adding up the Voltages to ensure I'm within the inverter range (90-520V) is it the Max Power Voltage (Vmp) I should be using?

    I'm still deliberating whether to upsize the inverter to a 6kW and do the full G99 submission. I would then install the 3-4kW of panels to start with and this gives me plenty headroom for the future. There's no downside to that is there? (apart from an extra £150 for the inverter).

    So, my main panels will be S facing, but I would look to add a couple SW and a couple SE later to catch early/late sun. Am I right in saying that these could be connected in parallel to the 2nd MPPT controller?
      Solis S5 GR1P.jpg
    • CommentAuthorphiledge
    • CommentTimeJul 8th 2022
     
    A G99 application would cost you circa £300 on top of the extra for the inverter and panels. Youll only generate at/near peak capacity over the summer and the rest of the year will be below peak. PVGIS will tell you what your different orientated panels will likely produce. Once you know what youll produce you can decide if the extra generation is useable and worth the extra outlay. It maybe that with the max panels that you can install, a G98 inverter running at its capped limit is adequate and save the application fee?

    Remember also that those that connect to the grid sooner may benefit from spare capacity and not have to pay for upgrades. Assuming continued growth in PV install, once spare capacity is used up any newcomers may be export limited or have to pay for grid upgrades! Once youve got consent for over 16amp export, youve likely got it for life and can add to the system as you want, up to your agreed limit.
    • CommentAuthorneelpeel
    • CommentTimeJul 8th 2022
     
    Posted By: philedgeA G99 application would cost you circa £300 on top of the extra for the inverter and panels. Youll only generate at/near peak capacity over the summer and the rest of the year will be below peak. PVGIS will tell you what your different orientated panels will likely produce. Once you know what youll produce you can decide if the extra generation is useable and worth the extra outlay. It maybe that with the max panels that you can install, a G98 inverter running at its capped limit is adequate and save the application fee?

    Remember also that those that connect to the grid sooner may benefit from spare capacity and not have to pay for upgrades. Assuming continued growth in PV install, once spare capacity is used up any newcomers may be export limited or have to pay for grid upgrades! Once youve got consent for over 16amp export, youve likely got it for life and can add to the system as you want, up to your agreed limit.


    When I spoke with the DNO a few weeks ago the lady seemed to suggest a G99 application might be free - depending if any further work or effort was required on their side. I was hoping that keeping it to 6kw or so would mean further work would be unlikely.

    But I agree, if it's going to cost anything then it's unlikely to be worth it.
    • CommentAuthorphiledge
    • CommentTimeJul 8th 2022
     
    SPEN charge £250+vat to process a G99 and lucky you if your DNO doesnt charge
    • CommentAuthorrevor
    • CommentTimeJul 9th 2022
     
    My G99 6kw application cost nothing. I realised that after about 9 months I was loosing extra export when the export limitation cut in so enquired how much it would cost to increase my export limit and had very quick reply after submitting some simple paperwork to say could go to 5kw and if wanted more would cost £750. I settled for 5Kw. From what I can make out depends which area you are in.
    • CommentAuthorneelpeel
    • CommentTime5 days ago
     
    Couple of further queries...
    - Do all the panels need to be mounted at the same angle or would I benefit from increasing the angle on my top row of panels? (see image)
    - Does anyone have any real life feedback on bifacial panels? I'm thinking that I could paint the space behind with reflective paint and maybe getting more early/late generation.
      Screenshot 2022-08-03 102615.jpg
  1.  
    Installing Bifacial panels at the moment. Mounted vertically but capable of rotation to horizontal. Will be next year before any performance details.
    • CommentAuthorphiledge
    • CommentTime5 days ago
     
    Posted By: neelpeelCouple of further queries...
    - Do all the panels need to be mounted at the same angle or would I benefit from increasing the angle on my top row of panels?


    The angle you choose depends on what you want to achieve. Shallow angle for better summer production, steeper angle for better winter production.

    The perfect solution is a full tracking system that keeps the panels square on to the sun whenever theres daylight but thats likely to be prohibitively expensive. A more practical solution if you are making your own support would be to have a manually adjustable frame(s) that you can lift in the autumn and lower in the spring.

    If you run the different angles through PVGIS you can see how generation will alter and decide if its worth the effort.
    •  
      CommentAuthordjh
    • CommentTime5 days ago
     
    Normally the angles of panels on a roof are constrained by the planning laws and by the need to consider wind uplift. If you overcome those issues then as said, more vertical increases winter output at the expense of summer and vice versa to some extent.
  2.  
    Not sure that answers the question which was: whether one row of panels could be made steeper than the other row, on the same roof?

    AIUI one row will generate more than the other (according to the time of day and year as mentioned above) and so that row could pass more amps of current. If the second row is wired in series, it will block some of that current. The same problem occurs if some panels in a string are shaded (eg by a chimney) and others not.

    However the inverter can often accept input from two different strings of panels, so the steep and shallow panels could be wired as two separate strings. Can anyone confirm?

    The colour shaded table here shows that any tilt angle between 20⁰ and 60⁰ produces pretty much the same, over a year, provided it is South facing, with a very slight benefit around 35⁰ https://blog.spiritenergy.co.uk/contractor/best-angle-solar-panels-uk

    AIUI bifacial panels are a different kettle of fish as they like light on the reverse side, so only tilting them a little steeper than the roof slope won't give much advantage. You can mount them vertically like a fence panel, and grow plants inbetween!
    • CommentAuthorneelpeel
    • CommentTime5 days ago
     
    Posted By: WillInAberdeenAIUI one row will generate more than the other (according to the time of day and year as mentioned above) and so that row could pass more amps of current. If the second row is wired in series, it will block some of that current. The same problem occurs if some panels in a string are shaded (eg by a chimney) and others not.

    However the inverter can often accept input from two different strings of panels, so the steep and shallow panels could be wired as two separate strings. Can anyone confirm?

    That's more where I was coming from. The Inverter I have bought (Solis S6-GR1P3.6K-Mini) has 1 MPPT but 2 inputs strings - I'm not exactly sure what that means. I was planning to simply connect in series, but maybe I'm better with the lower bank as one input and the higher bank of panels (at steeper angle) in the other?

    Posted By: WillInAberdeenThe colour shaded table here shows that any tilt angle between 20⁰ and 60⁰ produces pretty much the same, over a year, provided it is South facing, with a very slight benefit around 35⁰

    That's similar to what noticed using PVGIS calculator. It's a law of diminishing returns, but it looks to be worth getting the top bank from 22deg up to at least 35deg.

    Posted By: WillInAberdeenAIUI bifacial panels are a different kettle of fish as they like light on the reverse side, so only tilting them a little steeper than the roof slope won't give much advantage. You can mount them vertically like a fence panel, and grow plants inbetween!

    But in theory, if you have a gap (like, say, 30cm) and you have reflective paint behind the panels, then when the sun is anywhere near SE or SW then you should get a decent % rear gain. The panels at the side will get the most benefit. It should mean that you are maximising the earlier and later sun and balancing the output better.
    The reflective paint I've read about claims 90% of light reflected.
      Screenshot 2022-08-03 221156.jpg
    • CommentAuthorphiledge
    • CommentTime5 days ago
     
    There was talk earlier in the thread of adding panels at different orientations in the future. If youre thinking of separate strings for the 2 rows at different inclinations then you probably want to think about how youd wire any future additions at differing inclinations/orientations?

    Equally, you mentioned the bifacial panels at the side getting the most benefit from reflective paint but as Will mentioned the side panel output will be limited by the output of the lowest performing panel- those in the middle/oppostite end

    Maybe a micro inverter/optimiser solution would be better suited to what you want to do??
    • CommentAuthorneelpeel
    • CommentTime4 days ago
     
    Posted By: philedgeEqually, you mentioned the bifacial panels at the side getting the most benefit from reflective paint but as Will mentioned the side panel output will be limited by the output of the lowest performing panel- those in the middle/oppostite end


    Ah, good point! It's back to the same situation as differing angle / orientation isn't it. So maybe no benefit of bifacial after all (unless I change to microinverters). Bah humbug!
    • CommentAuthorphiledge
    • CommentTime4 days ago
     
    I think youll get a benefit from bifacial but just giving you the heads up not to forget that a conventionally wired string will always drop its output to the lowest performing panel in the string.

    If your array is facing south you should get fair generation off the rear of the panels early and late in the day. Manufacturer should be able to tell you how much??
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