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Renewable Energy: The dark side of PV ?

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    • CommentAuthorjamesingram
    • CommentTimeSep 26th 2011 edited
     
    Posted By: jamesingramlooks like this install might be on the dark side , house faces SW


    Tom , no not an appearance judgement , concrete tiles , solar panels, if you like them or not , I beleive it's more a case of what people are used to, currently that's not PV
    ( I like the look of them , and big wind turbines too)

    "It looks worse in reality" was more to do with the proximity of the tree and its over bearing on the house.
    the wide angle len opens up a picture , making things appear to be more spacious.

    SW so 45 deg. , tree approx. WSW
    Guessing now, but no direct sun til it comes round to south mid/late morning then shade by tree mid to late afternoon .
    • CommentAuthorjamesingram
    • CommentTimeSep 26th 2011 edited
     
    back to the hunt for a greener PV manifacturer
    here's more info on REC production methods (those Norwegian lots)
    http://www.recgroup.com/en/sustainability/Environmental-whitepaper/

    any critic ?
    •  
      CommentAuthorfostertom
    • CommentTimeSep 26th 2011
     
    Wd be interesting to guess the horizon and upload it to PVGIS?
  4.  
    I see the option on PVGIS , but how would I create a horizon , what software would I used , some kind of draw , to create bit map ?
    • CommentAuthorGavin_A
    • CommentTimeSep 28th 2011
     
    Posted By: jamesingramback to the hunt for a greener PV manifacturer
    here's more info on REC production methods (those Norwegian lots)
    http://www.recgroup.com/en/sustainability/Environmental-whitepaper/" rel="nofollow" >http://www.recgroup.com/en/sustainability/Environmental-whitepaper/

    any critic ?

    ah good find. We've installed a few of these due to their environmental claims, but I was getting a bit worried about why their latest sustainability report was 4 years old, so I'm glad to see a 2011 update that show's they're still walking the walk.

    Good well built panels too, particularly the black framed ones that look great.
    •  
      CommentAuthorfostertom
    • CommentTimeSep 28th 2011 edited
     
    Posted By: jamesingramhow would I create a horizon
    Doesn't it explain somewhere? Must do. What you do is:

    Divide the 360o full circle into however many segments you want, say 24 @ 15o. Then measure (or estimate) the horizon's angle of elevation at each of those compass bearings, starting from due east as far as I remember. Gives you a column of 24 numbers in Notepad. Save and upload the file to PVGIS and back comes the result with your 360o horizon drawn on, and solar input given as zero when the sun's below that horizon.

    If you want higher definition, e.g. to accurately put in nearby large obstructions like tree, building - say 96 segments @ 3.75o, just upload 96 numbers. PVGIS divides the full circle by however many numbers you upload. You don't have to bother with the horizon at bearings where the sun don't shine - just stick in zeros for those.

    This 'looking outward' system is simple, but suffers from being fixed to one viewpoint. If you want to try a viewpoint a bit sideways or a bit higher, to avoid shade from some nearby obstruction, then you have to do it all over again - laborious.

    The 'looking inward from the sun' alternative, which you'd get by 3D modelling the landscape incl nearby trees, buildings, and running a sunpath on that, means you can total the solar input onto any receiver surface you care to model - and which is easily moved around. However I've so far failed to find s/ware that will do that - well, I've tried Tas and it couldn't cope.

    In principle it's possible within the Tas toolkit, with a bit of ingenuity, but runs into graphic display problems or something, anyway after days of model building and problems, waste of time. Tas supplier EDSL head office suggested couple of things but basically uninterested, never even heard of the idea of including horizon effect - 'not our core business' - which seems to be aiding developers to barely comply with Bldg Regs as cheaply as poss. Which astonished me - horizon is crucial to winter solar collection, whereas EDSL seem only aware of solar as a summer gain problem (well above horizon) that needs to be excluded. What planet are they on?

    In despair, but luckily someone on GBF, or was it AECB.net, pointed me to wonderful PVGIS!
    • CommentAuthorGavin_A
    • CommentTimeSep 28th 2011
     
    creating a new horizon for PV GIS is doable, but pretty time consuming, and I can't off the top of my head remember exactly how we've gone about it when we did it.

    We just do our own shading assessment via the 3d models we produce, then input the losses we've estimated into PVGIS on top of the inverter and cable losses as it's far quicker and probably more accurate in most situations.
    •  
      CommentAuthorfostertom
    • CommentTimeSep 28th 2011
     
    Posted By: Gavin_AWe just do our own shading assessment via the 3d models we produce
    How do you do that? What 3D s/ware? How do you model the terrain?
    • CommentAuthorGavin_A
    • CommentTimeSep 30th 2011
     
    terrain?

    pv gis already models the wider terrain, we just model trees, chimneys etc. We use google sketchup for the 3d model and shading assessment, then compare the shading on an hour by hour grid of relative performance for each month to give us a percentage reduction in output from the shading for the year vs an unshaded system to input into PVGIS. It's a bit long hand, but it allows us to use our judgement about the precise shading impact on the panels including the bypass diode layout, which I don't think stuff like PV SYS does as well. As it's google, there are also thousands of user generated models of trees, chimneys etc that can be used so you don't need to model it all from scratch, just tailor a pre-existing model of the tree species to roughly fit the dimensions of the tree you're wanting to model.

    either that, or we use a hand held fish eye lens shading tool to assess it - this can also be used to create the template for inputting the shading layer into PVGIS as well if you can work out how to translate it into the correct format (manually IIRC)
    •  
      CommentAuthorfostertom
    • CommentTimeOct 3rd 2011
     
    Wow Gavin, can you go a bit slower, sounds like masses of info and experience (if not black art) there - wd love to understand!
    • CommentAuthorDavipon
    • CommentTimeOct 5th 2011
     
    Been using an expensive Californian gadget to assess shade, SAP figures make a mockery of this as any shading up to 20% is considered 0 shading!!:sad:
    •  
      CommentAuthorfostertom
    • CommentTimeOct 6th 2011
     
    What gadget? Please describe?

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