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solar panels on a south facing wall?

  • 20-01-2019 7:12pm
    #1
    Closed Accounts Posts: 3,220 ✭✭✭ cameramonkey


    Has anyone placed solar on a south facing wall? Are they much less efficient than having them on a roof? I will have flat roof and a south facing wall, what is the difference in efficiency between the two?


Comments

  • Moderators, Society & Culture Moderators Posts: 31,297 Mod ✭✭✭✭ Gumbo


    Has anyone placed solar on a south facing wall? Are they much less efficient than having them on a roof? I will have flat roof and a south facing wall, what is the difference in efficiency between the two?

    Mount them on the roof with angled sub frames.
    Do not put them on the wall.


  • Registered Users Posts: 1,917 ✭✭✭ bilbot79


    kceire wrote: »
    Mount them on the roof with angled sub frames.
    Do not put them on the wall.

    Not one for the detail?


  • Closed Accounts Posts: 3,364 ✭✭✭ rolion


    Nothign wrong to fit them on the wall,except they will not work as efficient as those fitted properly on the roof.
    So,for same amount of cash and the size of array,the one on the wall will have a more reduces output / generation than the one "adjusted" on the roof.

    Is the angle of the Sun's ray hitting the surface of the panels.
    Then,the PV panels cells has to harvest "the light" at a maxim efficiency angle and coverage to produce a maxim output.

    Some of us will have panels installed so that we can adjust the height of the mounting kit for a corect angle and others,well... will dream of getting a two axis solar tracker.

    more H E R E

    As per astronomical laws, the output of a PV array will look as the graph below.
    The fixed on the roof wil be roundish while of a tracker will have a better output due to a more perfect tracking of Sun's movement up in the sky.
    By having it on the wall,you will have a round output but,if nothing blocks or creates shades,will be small in generated output.

    470905.jpg

    470906.jpg


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


    Thanks for all the answers.

    I will put panels on the roof but the panels on the south facing wall are for aesthetics.

    I have seen panels that you can get in any colours or patterns and I may want to put them on the side of the house depending on price and planning.

    Is it possible to calculate the % difference between roof panels and wall mounted panels on south facing wall?


  • Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 89,776 Mod ✭✭✭✭ Capt'n Midnight


    How far are you from the Equator ?
    What is the priority ?

    Peak power averaged over the year
    The most power possible in the depths of Winter - bias to vertical panels
    Power as late in the evening as possible - bias to the West ( or East if you want morning power)

    all the above will influence battery backup costs too

    for a small system more panels might be cheaper than a tracker
    but note that tilting the panels vertically every two or three months will increase power too so don't get too excited about a 2 axis tracker


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  • Registered Users Posts: 1,627 ✭✭✭ quentingargan


    Here are simulations for roof at 30 degrees facing south and mounted vertically on wall facing south. Both options are for 14x300w panels and otherwise identical.

    4258 kwhrs/yr on the roof and 3167 kwhrs/yr on the wall. Also, there will be more risk of shade on the wall


  • Moderators, Category Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 58,884 CMod ✭✭✭✭ unkel


    For the craic have you any figures from a simulation for those panels on a north facing 30 degree roof in Ireland, Quentin?

    "Wind is Ireland's oil" - An Taoiseach, 25/05/2022



  • Registered Users Posts: 1,627 ✭✭✭ quentingargan


    unkel wrote: »
    For the craic have you any figures from a simulation for those panels on a north facing 30 degree roof in Ireland, Quentin?

    Here you go.


  • Registered Users Posts: 1,627 ✭✭✭ quentingargan


    Some confusion on those simulations. Herewith all three. North roof is worst by quite a chunk.:p


  • Closed Accounts Posts: 3,364 ✭✭✭ rolion


    For the craic.. why will I install PC panels facing North !? Trying to capture the reflection of photons !? Or lost the compass … or some new reflection / refraction technology better than any earth technology and we are not aware of it...hmmm


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  • Moderators, Category Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 58,884 CMod ✭✭✭✭ unkel


    That is far better than I expected. Thanks for sharing, Quentin. I had a thread up here a few weeks ago about it. Not quite sure what the angle of my roof is, perhaps it is steeper than 30 degrees

    For anyone not bothering with your attachments, a 4.2kwp system in Dublin on a 30 degree roof produces:

    4403kWh south facing
    2587kWh north facing

    In other words, north facing is still almost 60% of the production of south facing. I can see myself apply for planning permission in the near enough future and stick 6kwp on my north facing (road facing) roof...

    "Wind is Ireland's oil" - An Taoiseach, 25/05/2022



  • Registered Users Posts: 2,442 ✭✭✭ wexfordman2


    unkel wrote: »
    That is far better than I expected. Thanks for sharing, Quentin. I had a thread up here a few weeks ago about it. Not quite sure what the angle of my roof is, perhaps it is steeper than 30 degrees

    For anyone not bothering with your attachments, a 4.2kwp system in Dublin on a 30 degree roof produces:

    4403kWh south facing
    2587kWh north facing

    In other words, north facing is still almost 60% of the production of south facing. I can see myself apply for planning permission in the near enough future and stick 6kwp on my north facing (road facing) roof...

    Do i recall.your south facing roof being full because you have solar thermal ?

    Woukd there be any merit in relocating the solar thermal, and going for 4kwp on the south facing roof ?

    Ie, would the 4kwp solar saving over 6kwp pay.for.relocsting the solar thermal to the north facing roof ?

    With the hot water diverter in the solar pv you still get hot water.production from.both the pv and the thermal.


  • Moderators, Category Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 58,884 CMod ✭✭✭✭ unkel


    Nope, no merit in that at all. The solar thermal has far, far higher revenue per sq m compared to solar PV

    The good thing now about solar PV is that the panels are cheap, but you need a lot of roof surface.

    Got a good few more panels installed today anyway, electrician to install my new Solis 3.6kW dual MPPT inverter in the next few days hopefully...

    "Wind is Ireland's oil" - An Taoiseach, 25/05/2022



  • Closed Accounts Posts: 3,364 ✭✭✭ rolion


    I as trying to fit extra capacity as well,as you are thinking now.
    When i did my maths regarding the Sun's angle in direct contact with my location AND my house roof angle versus panels fitted fixed to the roof,i gave up.
    The angle of the Sun based on the month of th eyear versus the angle of the roof and the possibility of the photons to hit in the most best possible chance the surface of the panels just didnt convinved me.It looked like only few months i was getting decent returns.

    Can you do your maths, pen and paper and see if that makes sense !?

    I cant remember where i saved the graphs, found only few figures during my homework:
    january - sun @18degrees angle
    february 28
    march 34
    april 47
    may 54
    june 56
    july 52
    august 43
    sep 32
    oct 23
    nov 15
    dec 13


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