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New Build . A Few Questions.

  • 16-02-2020 11:02pm
    #1
    cameramonkey
    Closed Accounts Posts: 3,220 ✭✭✭


    I have have planning to build a house in south Dublin. It will have a flat roof with no overshadowing. The roof area will be 90 sqm . I plan on putting solar pv on the roof and some decorative solar panels on a south facing wall.

    I would like to ask some questions of those who have installed solar particularly in Dublin.


    From looking at your performance monitoring is there less or more sunshine before or after the solar noon in Dublin . I have noticed that there seems to be a lot of good sunny mornings in Dublin with it clouding over later. This of course may not be correct but it is what I have noticed.


    Another sort of related question is, the sun seems hotter in the hours after solar noon than the hours before, is this just a result of ambient air or ground temperature or would panels be more productive after rather than before solar noon?


    Do panels work better when the ambient temperature is higher or lower?


    Would having a reflective surface like foil or mirrors in front and below the panels bouncing light onto them improve their productiveness?


Comments

  • #2
    unkel
    Registered Users Posts: 64,758 ✭✭✭✭unkel


    Panels work better (are more efficient) when the ambient temperature is lower. That's the main reason why Ireland is pretty decent for solar PV. South facing in Dublin (or any of the other areas in Ireland best for PV), we get about half of the PV production compared to the best possible places on earth, where the sun nearly always shines. Not bad.


  • #3
    garo
    Registered Users Posts: 1,874 ✭✭✭garo


    I have looked production numbers quite closely and there is no real difference between before Solar noon and after. Will you face due south or be offset by 5 or 10 degrees? That can have an impact on when production is maximum. As unkel said cooler is better. But ambient temps in Ireland are low enough that it is not a concern except during high summer when you may lose a tiny bit of production in the afternoon due to panels heating up. Also don’t bother with foils and mirrors. I think you are over-optimising the wrong aspect. Try and figure out when your usage is highest and use that to decide the best orientation(s) for your panels. For most people having 25% panels each facing east/west and 50% south would be better than a single orientation. Or 25/35/40. Also go for a 35 to 40 degree tilt for your flat roof panels to maximise production.


  • #4
    cameramonkey
    Closed Accounts Posts: 3,220 ✭✭✭cameramonkey


    garo wrote: »
    I have looked production numbers quite closely and there is no real difference between before Solar noon and after. Will you face due south or be offset by 5 or 10 degrees? That can have an impact on when production is maximum. As unkel said cooler is better. But ambient temps in Ireland are low enough that it is not a concern except during high summer when you may lose a tiny bit of production in the afternoon due to panels heating up. Also don’t bother with foils and mirrors. I think you are over-optimising the wrong aspect. Try and figure out when your usage is highest and use that to decide the best orientation(s) for your panels. For most people having 25% panels each facing east/west and 50% south would be better than a single orientation. Or 25/35/40. Also go for a 35 to 40 degree tilt for your flat roof panels to maximise production.


    Thanks for answering and also to unkel. I plan on putting some on a vertical wall , they will be decorative so they will be facing from the direction of the side of the house, that is about 190 degrees or just past due south.They will be at at a 90 degree angle because they will be attached to a side wall. I can place the others in any direction I like but obviously from the point of view of maximum yield due south at a 35 degree angle would be best. We will not be in the house much in the morning or day. I will have to do a bit of thinking about it and about whether a battery would be essential for my set up.
    Would panels placed at a 90 degrees be more efficient with a lower sun than those at 35 degrees?


  • #5
    garo
    Registered Users Posts: 1,874 ✭✭✭garo


    South facing vertical panels would actually give you decent production during the winter months when the sun is low in the sky.
    For the remaining panels on the flat roof - you need to have a good hard think about when you consume electricity. You could get south facing panels at 35 degree tilt which would maximise overall production but give you most of it between 11 and 3 when no one is at home to use it. West facing panels may give you lower total output but mean that 6 months of the year you are getting some output into the evening when you are home from work and putting the oven or cooker on.
    Batteries are quite expensive still without a grant so an honest assessment of whether you are comfortable with the long payback. Another question: For the new house how will you get space heating, cooking and hot water? Will it be all electric or will you get a gas connection too?


  • #6
    cameramonkey
    Closed Accounts Posts: 3,220 ✭✭✭cameramonkey


    garo wrote: »
    South facing vertical panels would actually give you decent production during the winter months when the sun is low in the sky.
    For the remaining panels on the flat roof - you need to have a good hard think about when you consume electricity. You could get south facing panels at 35 degree tilt which would maximise overall production but give you most of it between 11 and 3 when no one is at home to use it. West facing panels may give you lower total output but mean that 6 months of the year you are getting some output into the evening when you are home from work and putting the oven or cooker on.
    Batteries are quite expensive still without a grant so an honest assessment of whether you are comfortable with the long payback. Another question: For the new house how will you get space heating, cooking and hot water? Will it be all electric or will you get a gas connection too?


    Thanks for that answer, its difficult answer those question, the nature of our lives mean we could be in the house anytime except maybe 10Am to 2PM, maybe I need to start a diary and figure out my main times at home but I think that would be after 5PM till dark. i actually avoid the house I am in at the moment because it can be cold and there is only electric heating that does not really suffice in the main living areas. If I put panels up for evening time it means I have 0 production on those panels for a lot of the year or I could think about moving panels to suit the seasons . i don't know because I have a flat roof whether that is practical or if I could factor that into the build of the house, the ability to shift panel position I mean.


    I will get underfloor heating that will be air to water I think, I will also have a heat exchange, I think the architect is looking to make it A2. I don't think I will be getting gas as hopefully the air to water and PV will be enough for all my needs.


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  • #7
    garo
    Registered Users Posts: 1,874 ✭✭✭garo


    Get one of those electricity monitors. Attach it or ask a electrician to do it for you and analyse the readings after a month or at least two weeks. Also you don’t get zero power from panels facing the wrong direction. There is enough diffuse sunlight that you get some power always. My east facing panels maxed out at 1500W today but we’re still giving about 700W at 2pm before the clouds rolled in. Think of E/W or SE/W in addition to your vertical panels to more evenly spread out your production during the day.

    https://aces.nmsu.edu/pubs/_circulars/CR674/CR674.xlsm
    Look at this sheet to get a sense of what output you can expect from different orientations. I wouldn’t go about getting a tracker system or thinking of changing panel orientation. Not very practical or cheap.


  • #8
    cameramonkey
    Closed Accounts Posts: 3,220 ✭✭✭cameramonkey


    garo wrote: »
    Get one of those electricity monitors. Attach it or ask a electrician to do it for you and analyse the readings after a month or at least two weeks. Also you don’t get zero power from panels facing the wrong direction. There is enough diffuse sunlight that you get some power always. My east facing panels maxed out at 1500W today but we’re still giving about 700W at 2pm before the clouds rolled in. Think of E/W or SE/W in addition to your vertical panels to more evenly spread out your production during the day.

    https://aces.nmsu.edu/pubs/_circulars/CR674/CR674.xlsm
    Look at this sheet to get a sense of what output you can expect from different orientations. I wouldn’t go about getting a tracker system or thinking of changing panel orientation. Not very practical or cheap.


    What angle have you got the east facing panels at?


  • #9
    garo
    Registered Users Posts: 1,874 ✭✭✭garo


    80 degrees or 10 south of due East. At a 25 degree tilt.


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