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Is north facing solar a complete waste

  • 24-12-2021 9:16pm
    #1
    Registered Users Posts: 1,322 ✭✭✭ Manion


    Hi,

    We've a large roof but it's entirely directly north facing, is solar a complete waste of time?



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Comments

  • Registered Users Posts: 1,615 ✭✭✭ Deagol


    In a word - yes.


    In a few words. Depends on what you want from it. If you put a very large array in (6Kw+) you might do ok with it on sunny days. But you'll never make your money back on the investment. If you take it that on a cloudy day in summer my 6kw array might manage 1.5kw during the peak of the day - you can imagine a north facing array won't do much more I would think on a sunny day.


    Maybe try one of the calculators online and see what it says though? Personally I wouldn't bother.


    https://www.seai.ie/tools/solar-electricity-calculator/



  • Registered Users Posts: 1,621 ✭✭✭ bullit_dodger


    Basically 100% agree with Deagol there - although that Seal calculator is a bit pants. It's a little more complicated to use, but

    https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP%20that's%20the%20calculator%20for%20Europe

    Gives a much better output. Basically plugging in a 5Kwp system, one facing north on a 35 angle roof and one facing south on a 35 angle roof.....gives you.


    So your production if it faced north is nearly half of what you get compared to the south facing. The winter months especially when you compare the two is quite striking. Sadly the equipment and installation cost is the same for both.

    Are you a bungalow or something that you only have 1 roof? The other option to consider is a ground mounted array. Very doable if you have the space (perhaps out the countryside?)



  • Moderators, Sports Moderators Posts: 16,443 Mod ✭✭✭✭ slave1


    What form is this building with only N facing roof?



  • Registered Users Posts: 1,270 ✭✭✭ reboot


    Met office said yesterday Lerwick in Scotland had 49 minutes of daylight.!



  • Registered Users Posts: 1,322 ✭✭✭ Manion


    This is the house type, it's an odd design but we love it as the master bedroom is double height.

    Unfortunately our house faces due south so the roof is directly north. Its massive though at approx 60 square meters of usable space. The seal site estimates 28 year pay back, which is unfeasible as I'd imagine the components has a life expectancy of 10 to 15 years.



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  • Registered Users Posts: 1,270 ✭✭✭ reboot


    Forget it.



  • Registered Users Posts: 24,763 ✭✭✭✭ emmet02


    Have a similar setup - 60sqm of roof - which is 'extremely flat' but pitched slightly (1:80) North.

    Could I get tilted mounts or something which would unlock the potential of the surface area?



  • Registered Users Posts: 1,615 ✭✭✭ Deagol


    Don't think you could tilt it back - you would end up making a giant sail on your roof which would probably lift it off next good storm. Better to look at ground mount options I would suggest.



  • Registered Users Posts: 1,621 ✭✭✭ bullit_dodger


    emmet02 since it's 1:80 it's essentially flat and while pitching the panels would definitely improve your production, roofs which are essentially flat have reasonable production by default, even north facing. If you want a bit of math and a longer explanation.

    How much less efficient are north-facing solar modules? (solarpowerworldonline.com)

    Ideally you would want solar facing south, but in reality the pitch of the roof is a huge determining factor. You can "get away" with low pitched roof facing north much better than say your average 30-40 degrees roof.

    Going back to

    https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP%20that's%20the%20calculator%20for%20Europe

    and plugging in 5Kwp one facing due north with a 5 degrees pitch, and the other due south with 5 degrees roof pitch....they are as you can see pretty close.

    Course the steeper the roof the bigger the difference between the north and the south.



  • Registered Users Posts: 5,855 ✭✭✭ touts


    The sales guys will tell you it will work.


    The engineers will tell you it's pointless.



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  • Registered Users Posts: 1,615 ✭✭✭ Deagol


    Hmmm - maybe the buckets (Renusol) would work on a 1:80 roof?



  • Registered Users Posts: 1,621 ✭✭✭ bullit_dodger


    Well as an engineer myself :-) .... depending on the pitch, it's definitely not pointless. However, the angle of the roof -HAS- to be under 10 degrees for it to be anywhere useful, the higher the slope of the roof, the more useless it'll be of course.

    So if Emmet02 has a 1:80 pitch that equates to an angle of <1 degree away from the horizontal plane, assuming 1:80 is correct. That's a pretty flat roof really.



  • Registered Users Posts: 713 ✭✭✭ Feidhlim


    Is it worthwhile to add some north facing panels to a system which is primarily south facing? I.e. a couple of panels on North side of house to supplement the south?

    30 degree angle.



  • Registered Users Posts: 1,621 ✭✭✭ bullit_dodger


    With a 30 degree slope, its unlikely to ever pay you back the cost of the panels. That said you would get "something" from them esp in the summer months where the sun rises in the north east and sets in the north west, and the sun is high enough in the day to shine on them. However, like most of us, you probably already have an over abundance of generation in the summertime as is?

    In general though, you'd probably be better off using the money elsewhere. No chance in reconfiguring your existing south facing array to squeeze in some more panels? Perhaps with a different orientation? Or maybe ground mounting some on a fence/wall?



  • Registered Users Posts: 713 ✭✭✭ Feidhlim


    I've no idea, to answer your question. I have no system right now. Just all in its planning infancy!



  • Moderators, Category Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 59,697 CMod ✭✭✭✭ unkel


    A lot of the comments here are totally outdated as they are based on the price of panels from many years ago, like that article from 2016 that bullit_dodger linked to. Panels are now dirt cheap (well since COVID a bit less so) and if you do an install DIY, a pure north facing array on a relatively low angle roof makes perfect sense and can be a sound financial investment (on top of helping the planet)

    If I didn't already have almost 8kwp or if we were to get a decent FIT that would be FIT for purpose (pun intended, LOL), I would seriously consider plastering my virgin north facing roof with many panels

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



  • Registered Users Posts: 1,621 ✭✭✭ bullit_dodger


    Yup I'd tend to agree with you there unkel, though the article i linked was more for the math around the production rather than the return on investment aspect....but as you say, panels have come down a lot since then. In 2018 and 2019 alone they came down a ton. That said, I'd still advise caution there with north facing panels.

    If you have an existing array, then it's not so bad. You already have a "sunk cost" for inverter and possibly battery and the extra panels is more likely to give you something useful to add to existing production. However, if all you have is north available to you, and especially if you have more than 15-20 deg slope, I'd think you'd be better off investigating alternative solutions. Ground mounted array or perhaps 4-5 panels on the side of your house? Or spend the money on a ground source heat pump (if applicable for your house - not all houses are a good fit).

    I know, I know I'm a kill joy (LOL).... but sometimes while as much as i like to see Gretta happy, a nod to the fiscal side of things is necessary.



  • Moderators, Category Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 59,697 CMod ✭✭✭✭ unkel


    I'm the biggest kiljoy on this forum, how dare you try steal my title 😂


    But yeah we seem in agreement. I'm all for renewables, it's not just about money, but we need to be aware of costs and returns. Whatever options you have. And we need to be sensible. It is quite likely that a ground mounted south facing array (particularly if you can't do the work yourself) will have a much longer pay back time than a north facing DIY setup

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



  • Registered Users Posts: 309 ✭✭ Snugbugrug28


    On an east-west facing roof is there good value in having arrays on both sides?



  • Registered Users Posts: 2,976 ✭✭✭ graememk


    East/west are well worth it. You don't get the big peak at mid day as you would with a south facing. But it starts earlier and finishes later giving a longer generation period at usually more useful times.

    Although winter isn't their friend! With short days and low sun.



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  • Registered Users Posts: 1,322 ✭✭✭ Manion


    Just using the calculators linked to it seems a poor investment decision, am I miss reading it somehow?. That said there is a part of my that is just worried about Irish energy supply in the future, and I somewhat view having an independent power supply as something of a lifestyle choice, also the Carbon death of the planet is a bit of a downer. Our current yearly power consumption is approx. 8600 kW/h (we've an air to water heat pump) and I could see us toping 10K kW/h when the EV arrives.



  • Registered Users Posts: 1,615 ✭✭✭ Deagol


    If you're expecting to make a return on your investment with North facing - you probably won't. If you're only thinking of monetary considerations then I personally wouldn't bother. But I and a few others here are taking the longer term view that anything we can do to stop burning fossil fuels and using renewables instead has more than just a financial positive.



  • Registered Users Posts: 1,621 ✭✭✭ bullit_dodger



    I'd echo what graememk said above and add some more info as someone who has an exactly east/west split (1.4 Kwp East/3.8 Kwp west). Definitely 100% they are worth it. In fact for some consumers like me, they are better than south facing. I'll explain below. Sure as graememk mentioned above.... in winter, when the sun rises in the south east (very slowly) and then gets to 15 degrees elevation at noon due south and sets in the south west, you don't get much production as the panels are never really facing the sun being orientated east/west. Some real life figures for you.... is that I generated 56kwhr on a 5.3 Kwp system (which was 6% over forecast) for December. Not a lot. If those panels were all south facing I'd have produced 130Kwhr. So you can see the benefit of a south panel in Winter. Nearly 2.6x the generation

    However, from March to Oct the East/West split works out very well. You end up getting 2x peaks during the day. one about 8-9am and the other about 3-4pm. (The times of these peaks do move during the year as the sun changes) That 2nd peak in the afternoon is helpful to charge a battery to get you to ride through the evening until night rate comes on.

    In high Summer of course (May-Aug) the sun is even rising in the North east, so your East facing panels will start to produce from as early as 5-6am - and with the long days your west panels are producing right up to 8-9pm. South facing panels will only come fully on stream much later in the day, and reduce production at 5-6pm (roughly)

    If you consume leccie at breakfast (8am) and again later in the day when you come home from work that split works out very well. Overall an east/west split generates about 85% yearly what a south facing one does, so technically south is "better" but there are some advantages as mentioned above.



  • Moderators, Category Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 59,697 CMod ✭✭✭✭ unkel


    Quentingargan has shown us screenshots from his professional calculator, which shows N facing panels at a typical angle in Ireland have about 50% of the total annual production of S facing panels. With a low angle like the OP has, this figure will be a good bit higher. If you can get the parts cheap, do a DIY install, then for sure this will be a good investment choice. Particularly if you have savings that attract zero interest and with the current fast rising electricity prices. Those panels will work for many decades to come

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



  • Registered Users Posts: 1,322 ✭✭✭ Manion


    Confused, I'm the OP?



  • Registered Users Posts: 43,856 ✭✭✭✭ 6


    If you can get a decent install price or DIY go for it.



  • Registered Users Posts: 1,621 ✭✭✭ bullit_dodger



    I think the general feeling is that south, east and west are "no brainers" for a solar installation. With those orientations, you'll get your money back in approx ~10 years (give/take) depending on what the price you paid for it of course and your consumption. North facing panels requires some further thinking.

    It's workable if the angle on your roof isn't too steep. Ideally you'd want to have a roof which has less than 15 degrees slope. From the previous picture you posted Manion, I think that you angle is way higher than 15 degrees, so for you I think you'd suffer. However, the one option you still have available to you is if you can remove the middle man and install the panels yourself (like some of the regulars here have done) you can "load up" on panels to make up for the lack of (efficient) generation with sheer volume of panels. Panels are reasonably cheap these days (circa €200/panel, sometimes less even).

    You will suffer pretty poor generation in winter, but in summer you'll do ok. Your payback timeline will probably (I'll ballpark) 20+ years, but as unkel says.....it's not all about money and payback. Sure payback is important, but knowing that your doing the right thing for the environment is worth something too.

    If it was me, I'd probably investigate alternatives. For example can you vertically mount some panels on your south facing wall? Angle them 10 deg from the vertical plane. Something like this guy is doing. Maybe 5-6 of these panels with the rest (bulk) facing north then you could be on a real winner.

    Wall Mounted Solar, worth it? - YouTube

    Just a thought.



  • Registered Users Posts: 1,322 ✭✭✭ Manion


    Well the south facing wall in the front of the the house, can't see that going down too well given the policy on Sky dishes being mounted to the front. Anyway, I've just figured out we're not eligible for the grant as the house was built in 2016, so looks like we wont be going any further. I found a crowd willing a crowd https://www.solarstream.ie/products/residential-6-kw-pv-solar-battery-system willing to do the installation of a 6Kw/H system plus batter for 14,695 Euro but their site clarified I wouldn't get the grant. I do agree it's about more than the pure numbers, and we have a heat pump, an A2 rated house and all A+ or better appliances but I think it would be foolish to go solar without the grant at this time looking at those prices, especially as it looks like something is to be done in the 2022 budget.

    As for DIY, fair play, but I'll not be taking that on.



  • Registered Users Posts: 1,621 ✭✭✭ bullit_dodger


    The grant eligibility requirements have changed very recently (Jan1st?) or they will be changing very soon as announced in the last budget. You no longer need a house built pre 2011 to avail of the grant.

    That said, while I think the grant is a great incentive....it's not totally "free money". I've seen people quoting prices to install a system without a grant which were very reasonable. The logic is that the suppliers sort of "up the price" cause they know you are getting the grant, so they build that into the price. Basically you can get fleeced if your not careful.

    Aside: That price of €14,695 is (how shall i put this?) ..... let's go with "a lot" for a 6Kw system! That system should (ballpark) cost €8500-€9000 or there abouts. (this is without grant applied)

    Adding a 5Kwhr battery that would be €10.5-€11k. So the quote you have is probably €3k+ over what you should be paying if you shop around.

    If you can avail of the grant, that would be of course €3k less, so you can expect to pay (ballpark) in about the €8.5-9K mark for a 6kwp system and 5kwhr battery. There's a whole quote thread you should read.

    Domestic Solar PV Quotes 2022 - Page 9 — boards.ie - Now Ye're Talkin'

    If all your panels were north facing, I'd probably add 50% to the panels and look for 9Kwp, as you won't be efficient but this really is down to you and your consumption. I reckon you'll still be in under €12-13K.

    Obtaining the grant is useful, but I've seen people get bigger systems saving themselves €5-6K by shopping around.



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  • Registered Users Posts: 1,322 ✭✭✭ Manion


    Thanks, I've been reading through the quotes thread. Is there a list of vendors people recommend or a way to get a number of quotes. Tbh thinking this morning, we're talking about reducing our yearly energy needs by 2900 units on a 6kw system, that roughly 30% of current usage. The pay back would be a long time but it would feel great to get that drop.



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