Advertisement
If you have a new account but are having problems posting or verifying your account, please email Niamh on [email protected] for help. Thanks :)
New AMA with a US police officer (he's back!). You can ask your questions here

New PV instal advise please?

  • 16-04-2021 9:32pm
    #1
    Registered Users Posts: 8 welshchris77


    Hey folks,

    Looking for a bit of advise on what I may need for a PV instal, I will try to provide as much information as possible.

    Bassically myself, my wife and our 3 children live in a granny annex, my parents live in the old cottage next to us, our combined electricity usage can be very high so we would like to bring our bill down, also we are all very environmentally aware and want to reduce our carbon footprint.

    At the moment we don't have any central heating systems in place in any of the buildings aside from a stove in the cottage (no back boiler and rarely used), everything is being run off electric radiators, not great I know but all we have at the moment.

    After looking through these forums it looks to me like the cheapest option would be a self instal as the grants seem to be waste of time for us with the cost of labour, BER, etc.
    I did contact a few installers, many did not get back to me and a few who did gave the whole sales pitch thing/consultations, all I wanted was a ballpark figure and breakdown of costs.
    Time is not a factor, if it takes me a month or more I am good with that.

    I have a few disabilities but am confident that myself and my father can do this. I build our annex, re-roofed (warm roof) the old cottage and built a cabin and shed a few years ago along with my father and also did all the electrics, floors, windows etc.

    The one side of our roof is facing south 3.750m High x 8.430m Long, we can fit two rows of 7 panels (14 total) (5kwh system).

    The bit I am unsure of is what inverter to use and whether to add a hw diverter, I am leaning away from a battery for now as I don't think we would get the use out of it but may add it in the future as well as a EV if we can sell our car and get an old leaf or something similar.

    The only issue I see with the roof is a esb pole casting a shadow, I checked it today and the shadow does not touch our roof but my dad checked it in the winter and said it will cast a shadow over the bottom half of the roof throughout the day, my thinking is to split the array into two or more sections, so micro inverters could be an option right?

    Any excess power we produce can be used by my parents in the cottage, I am not sure about a water diverter as we have a very small (but factory insulated) 60L cylinder, it is only used for showers, usually once a week, the occasional bath and washing dishes, that is it, I can't see there being any excess power at all for the diverter, maybe it is not worth?, still not sure about that but can always add in latter.

    I may install some type of wind turbine in the future to produce energy when the panels are not generating, there is a wind farm nearby so makes sense but this may not be for a few years yet, I had looked at a hybrid inverter for this but they are very expensive and it may not be utilised for a few years, other inverter options could become available in the future.

    If this works out I do plan on installing (when funds are available) a similar system on the cottage for my parents.

    I also plan on insulating the properties more when I can afford it.

    We have looked at a company for the panels but am not sure I can name them here due to forum rules?
    The cheapest panels they have are these:- Longi 375W Black Frame White Backsheet price ex.vat € 116.51

    Also in the future I plan on adding another array to our shed next to us so not sure if I should go for a bigger inverter 'now' or just get another one for when I do the shed?

    There was probably more I needed to add to this thread but I have most of it down.

    In the meantime I will continue to read through as many things as I can, including threads on here.

    This is one of the best forums I have come across, thank you to the people who set it up and moderate it.


Comments

  • Moderators, Sports Moderators Posts: 16,066 Mod ✭✭✭✭ slave1


    You could fit 12 410w panels in three rows landscape on that S facing roof, two strings with optimisers on shaded panels but in all honesty there is poor PV production in winter so think hard on that optimiser investment, you do not need micro inverters with this setup.
    Match with 5kW dual MPPT inverter.
    You should manage this for around €4k after grant.

    Diverter to that size hot cylinder makes zero sense.

    Really you should insulate first.


  • Registered Users Posts: 1,835 ✭✭✭ garo


    +1 to what slave1 said.


    A few additional things to keep in mind:
    1) If doing a self-install battery does not make sense. If going the grant route - it may make sense depending on the quotes you get.
    2) Without a battery for the self-install you can get an ordinary i.e. non-hybrid inverter. Something like: https://midsummer.ie/buy/clearancestock/sofar-5ktlm-g2 or https://midsummer.ie/buy/solis-inverters/solis-dual-5000-4g-DC or https://solartricity.ie/product-solis-single-4-6kw/ A hybrid inverter - which you NEED for a battery - will costs twice as much.
    3) Get a dual string MPPT inverter and put your top row on one string and bottom on another. That way the winter shadow will only affect half your output. Note even a single panel in the shadow will pull down production for all panels on that string. Optimizers or micro-inverters often don't make economic sense because production is so low in the winterthat what you gain is not worth much. There are exceptions to this: e.g. when your panels have a good (35-50 degree) angle to horizontal, are south facing and you only get shading on a couple of panels.
    4) You will produce 10x as much in May as in December. So don't look at Solar PV to reduce your heating bills. Some basic DIY insulation - insulation boards along the outside walls, loads of insulation in the roof/attic will have a much higher return. As will converting all light fixtures to LED.
    5) You said electricity usage is high but do you have approximate numbers?
    6) If you use an immersion exclusively to heat your water then a diverter makes sense. But you are right 60l is way too small. Do you have the immersion on constantly? You should be able to get a decent copper factory insulated cylinder of 250l capacity for < 400 installed. That will really improve the pay off for the diverter in addition to the convenience of having HW available at all times. For example see this: https://www.plumbingproducts.ie/indirect-insulated-ireland/2190-copper-cylinder-insulated-36x18-1-coil.html Of course you can get a better and larger steel cylinder if you spend more money but this is a bargain basement solution that will be much better than your current one. And yes if doing a self-install a diverter can be added later. Just make sure to run a cat6 cable from the fusebox where the CT clamp of the diverter goes to where the diverter would be.


  • Registered Users Posts: 8 welshchris77


    slave1 wrote: »
    You could fit 12 410w panels in three rows landscape on that S facing roof, two strings with optimisers on shaded panels but in all honesty there is poor PV production in winter so think hard on that optimiser investment, you do not need micro inverters with this setup.
    Match with 5kW dual MPPT inverter.
    You should manage this for around €4k after grant.

    Diverter to that size hot cylinder makes zero sense.

    Really you should insulate first.

    Thanks Slave1,

    Would installing the larger size panels be worth it?, ie x12 x 410w = 4920w (landscape) as opposed to say 14 x 370w = 5180w (Portrait).

    I only ask as if I go the self instal 420's would need to be installed in 3 rows of four panels equaling six rails so 6 rows of roof hooks rather than the 370's in two rows equaling 4 rows of rails, 4 lines of roof hooks, I have seen a few vids of how to instal the hooks, they look a pain the butt, just thinking about the labour &#55357;&#56883;

    Note:- My roof rafters are 600mm spacing.


  • Moderators, Sports Moderators Posts: 16,066 Mod ✭✭✭✭ slave1


    I'm only thinking of getting the max wattage from the available roof space is all, being honest I didn't do the maths, your existing plan of 14 370's give a better wattage so ignore my comment, apols for misleading you.
    The more wattage, the more PV


  • Registered Users Posts: 8 welshchris77


    slave1 wrote: »
    I'm only thinking of getting the max wattage from the available roof space is all, being honest I didn't do the maths, your existing plan of 14 370's give a better wattage so ignore my comment, apols for misleading you.
    The more wattage, the more PV

    No no, all good Slave1, not misleading, I could see what you were getting at for max wattage, I really appreciate your input, little more wattage with the amount of the 370's I can fit on alright but I had actually forgot about the larger wattage on the 410's, if the 410's optimised better into the space I would use those for sure! 👍


  • Advertisement
  • Registered Users Posts: 8 welshchris77


    garo wrote: »
    +1 to what slave1 said.


    A few additional things to keep in mind:
    1) If doing a self-install battery does not make sense. If going the grant route - it may make sense depending on the quotes you get.
    2) Without a battery for the self-install you can get an ordinary i.e. non-hybrid inverter. Something like: https://midsummer.ie/buy/clearancestock/sofar-5ktlm-g2 or https://midsummer.ie/buy/solis-inverters/solis-dual-5000-4g-DC or https://solartricity.ie/product-solis-single-4-6kw/ A hybrid inverter - which you NEED for a battery - will costs twice as much.
    3) Get a dual string MPPT inverter and put your top row on one string and bottom on another. That way the winter shadow will only affect half your output. Note even a single panel in the shadow will pull down production for all panels on that string. Optimizers or micro-inverters often don't make economic sense because production is so low in the winterthat what you gain is not worth much. There are exceptions to this: e.g. when your panels have a good (35-50 degree) angle to horizontal, are south facing and you only get shading on a couple of panels.
    4) You will produce 10x as much in May as in December. So don't look at Solar PV to reduce your heating bills. Some basic DIY insulation - insulation boards along the outside walls, loads of insulation in the roof/attic will have a much higher return. As will converting all light fixtures to LED.
    5) You said electricity usage is high but do you have approximate numbers?
    6) If you use an immersion exclusively to heat your water then a diverter makes sense. But you are right 60l is way too small. Do you have the immersion on constantly? You should be able to get a decent copper factory insulated cylinder of 250l capacity for < 400 installed. That will really improve the pay off for the diverter in addition to the convenience of having HW available at all times. For example see this: https://www.plumbingproducts.ie/indirect-insulated-ireland/2190-copper-cylinder-insulated-36x18-1-coil.html Of course you can get a better and larger steel cylinder if you spend more money but this is a bargain basement solution that will be much better than your current one. And yes if doing a self-install a diverter can be added later. Just make sure to run a cat6 cable from the fusebox where the CT clamp of the diverter goes to where the diverter would be.

    Thanks garo👍,

    1) I think I am done with quotes (with grant) and will just be looking for quotes on best price for materials now and going the self build route, I may go for the grant if I instal a second array on the old cottage as that is the main residence anyhow and where I would most likely have to get the BER cert for, I have dealt with BER inspectors in the past and got frustrated, it was maybe 10 year ago and I wasn't impressed, I wanted to avail of a grant to get the walls pumped on the extension on the old cottage and ended up with something like an F or G, the person marked me down as I had hardwood windows instead of PVC, they were new and super chunky and also had double glazed units, from what I had read at the time they are better U-Value than PVC and last longer🤔.

    Also I had re-roofed the entire building and did a 'Warm roof configuration', 4" foil backed poly between the rafters with 2" over the top covering the cold bridges.
    The inspector had never heard of it!🙄
    We had to get two things done to qualify for the grant so had to get attic pumped which was pointless, the cottage only has a tiny attic, literally a 3 foot high crawl space.
    Rant over!, sorry, lol.

    2) Yes was looking at the non-hybrid inverter for now as they are half the price👍

    3) Am assuming 'dual' on a MPPT refers to the 'two strings' (circuits), so cannot add a further string in the future?. At a latter date I may add a few more panels to the extension we have on our annex, it is single story 'lean to' type roof, low angled metal panels, it is facing North unfortunately but could put panels at the highest point with brackets to raise them up to face South, if that makes sense?, wind could be an issue or storms though.
    Another option is to just add an additional system on my shed/studio, both sides 2 strings, low angle east /west roof.

    4) Affirmative to that, will be also adding as much insulation where we can, I was a bit shocked at how much insulated plaster boards had gone up since I last bought some a few years ago!😯, all our lights are LED 👍

    5) In the coldest months we were into the thousands in terms of units for our 2 month bill!🙁 we are using elec, but also my parents are in the old cottage too right now we are all clubbing together to pay the bills.
    I am getting a small Single Phase Energy Meter as they are quite cheap so we can see exactly how much elec we are using.
    Right now we are blaming my parents for using too much elec and they are blaming us, we are most likely using much the same! lol.

    6) The immersion is on during the day 7am until about 9pm, the timer in analog and I did try to set it to come on at like 3 times or so during the day but it often would trip out, I suspect it maybe full of lime as our water wasn't the best for a few years so probably tripping the thermostat on the emersion (will get back to that).

    My parents rarely turn theirs on, only for a bath, they boil a kettle to do the dishes, they do however have an electric shower (due to be changed like we did to run off the HW cylinder).

    We have very little room for a larger size cylinder right now, the airing cupboard is tiny, we are not too bothered though, to cut down on power usage we may just turn off the immersion altogether and only use it when we all need a shower, we can boil the kettle when needed for the dishes (until we can think of another solution).

    I am actually not sure of the capacity of the cylinder but it is small 36"x15" insulated 'indirect' (we did plan on heating it with an additional source some day) so I guessed it must be around 60L, would only be enough HW to quarter fill a bath, does not cover me so I just have a shower (fine for the kids) I don't mind, could possibly go to a taller cylinder, we do not have the cupboard depth to go wider/deeper.


  • Registered Users Posts: 1,835 ✭✭✭ garo


    Yeah battery definitely doesn't make sense in your use case. But you should definitely get a diverter since you use the immersion primarily for hot water.


    Electricity (or rather resistive heating) is a pretty expensive way to heat the house or water. I think that explains your big energy bills more than anything else. 36x15 is a 120l cylinder and should be enough for at least one bath. You could go 42x15 or 48x15 but I'm not sure if it is worth it. Maybe your immersion element is not long enough to reach the bottom so can only heat up the top 2/3rd or even half of the tank. Do you have a bath/sink switch? Check the length of the immersion and see if you can get a longer one. A new longer immersion would only set you bac 30-40 EUR max and would also solve the limescale/tripping problem maybe? Having the immersion on constantly really tests quality of the factory insulation on your cylinder so anything thin would lose heat.



    Overall I do think that sorting out your hot water situation will both save money and make life more convenient. I assume you cannot or do not want to get gas or oil boiler. And your BER rating isn't good enough for a heat pump.



    Looking at the steps you have taken to insulate and get a warm roof I find it hard to believe you ae F or G BER. Either the house has a small floor area - which works against you - or the BER assessor had no idea what he was doing. They can be a bit hit/miss to be honest. In order to get the grant you would need to be C rated anyway so even if you were interested its quite possible you wouldn't be able to avail of the grant.


    Yes dual means dual string. The way MPPT works it adjusts voltage and current to maxmise power output from a string. Hence all panels on a string need to be oriented the same way (and not be shaded) or overall output suffers. If you want to add a third string - you need another inverter. I would go with the low angles E/W and another inverter when you get to that point. N will give about half the production of a south facing panel but I would not raise it the way you describe. A bad storm might take your whole roof off.


    You should definitely invest in an electricity monitor. If at all tech-minded look at the emon pi. You would be surprised at how much you could learn and then be able to direct your investment so you get the best bang from your buck.


  • Registered Users Posts: 8 welshchris77


    So an update, it has been 16 months since I last posted, since then I concentrated my efforts on retrofitting more insulation and rewiring our bedrooms and living room, 4x rooms altogether, took me a long time due to my health but got there in the end, the difference last winter was huge, we barely needed to heat the bedroom at all most nights.

    Also my parents sold their old car and we all clubbed together to get a second hand leaf, 2015, 11 bars on battery, 25kw, 3.3kw (in hindsight I wish we had sourced a 6.6kw charing car now but live and learn), it is great for local journeys, 98% of our driving, we still have our old family Corolla Verso for long journeys but it sits up in the drive way most of the time, feels great going electric.

    Now I am back to my original plan of installing pv to our place (x14 panels) and/or the shed (x14 panels), probably just do our place first, got the scaffolding up today, sent email off to Solarticity yesterday, anxious to get going on the dreaded brackets asap and that was my biggest concern, in the email I mentioned our intentions and to size the inverter for use with the shed array further down the line, hopefully they reply soon.

    Also been looking at midsummer.ie but their prices seem a lot higher unless a trade account is opened with them but I do not own a company so can't do that unfortunately.

    I might hold off for a short time before buying to see if VAT is to be cut on renewables as the budget should be very soon, I heard it could be released early.



  • Moderators, Sports Moderators Posts: 16,066 Mod ✭✭✭✭ slave1


    I wouldn’t wait on chance of VAT decrease, price of everything is only going one way and we are already hitting supply issues, couple that with rising electric costs…..



Advertisement