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Solar PV

Discussion in 'Building Regulations and Planning Permission' started by Click4B, 9 Jan 2020.

  1. IT Minion

    IT Minion

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    There's a long, long, thread on Moneysaving expert about solar panel generation. They use a unit called 'O's where a 4kw system that generated 4kwh would produce 1 'O', a 4kw system that produced 8kwh would be 2 Os etc.

    So far this year very few people seem to have generated 1 or more on any day.

    Your numbers:

    Would be 3.5-4 Os. Which is very over optimistic. What you're likely to find is a massive disparity between winter and summer generation. That's more likely to be spring or autumn performance levels.

    The SolarEdge optimisers are great if you've got shading and pointless if you don't have shading. If you do have shade then that's still going to cut into your generation.

    For using your power then you'll want/need to schedule tasks like charging to happen when there's a surplus of energy. I believe there are some systems that let you selectively charge the car when the sun shines, there definitely is for electric water heating etc, but it isn't routine. Batteries are good for allowing you to use the power another time but they're borderline on cost/reward at the moment.
     
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  3. rssteve

    rssteve

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    Theres no way that system will produce the figures you think they will. I'd look at some graphs from.working systems to get a better idea on what they produce especially on average days and overcast days.
     
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  4. Click4B

    Click4B

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    Thanks,

    that’s the thing I’m still new to this myself and haven’t got first hand figures, only assumptions based on what I’ve seen other people achieving but they aren’t all accurate because 10kw isn’t common, most seem to be around 3-4.5 or thereabouts.

    so all information appreciated.

    still has to be worth it though because in the daylight months it will be generating enough to keep up with demand leading to significant reductions in bills.

    reason I’m going down this route is because overall I’m having a heating dilemma.

    Originally I was going to go down heatpump route, as I don’t want to stick with fossil fuelled heating for a few reasons...with a view that it’s about same cost as gas to run when properly sized and installed... and it could be offset with solar later on making it cheap as chips to run.

    but had a think about it and I keep swaying back and forth... as later on there is a chance that the house will be rented.

    if so, heatpump May pose a few issues, 1) the repair times, 2) the cost to repair, 3) they are best left on with a set temperature on thermostat so it just keeps topping up the heat.. as they run at lower temps and can’t heat a house quickly.

    but if I end up with a tennant who thinks right I’m off to work 9am in the morning, switches it off for 8 hours... comes home in evening, switches it back on and then 2 hours later it’s still heating the house up.. I’m going to get nothing but complaints.

    also spoke to building surveyor, and he recommended against it, said he would insulate and stick with electric boiler so you don’t need to heat as much due to retention.... energy assessor pretty much said same thing given the government are planning on bans for new homes to be heated by fossil fuels in next 5 years... even labour was talking about imposing on gas boilers in the general election.

    so that directed me towards electric boiler, relatively cheap to replace, simple workings with very little to go wrong, heats up to 80 degrees, no issues with carbon emissions, no landlord certificates, no annual servicing, no expensive repair bills.

    Only issue is at 9kw it has the potential to massively increase an electric bill into eye watering costs.

    so I started looking at solar again, and been trying to figure out the numbers.... even if it doesn’t fully offset it, I’m hoping that the extra it costs during the autumn and winter to run... will be offset by the savings in the spring and summer months when solar is powering everything in the house reducing the electric bills down to almost next to nothing.

    with a view to later on expanding it with battery storage to maximise things so rather than exporting to grid it’s charging batteries for use when solar isn’t working and also with the push to electric vehicles this decade going on.. figured if it would go towards charging if I ever got an electric vehicle... then would save further from reduced costs charging it compared to fuelling a combustion engine vehicle.

    but I could be wrong... I don’t know, trying to figure everything out lol Just solar seems to be a way forward with the details in between something to iron out along the way.

    but heatpump, solar, pretty much on par with one another in terms of cost.
     
  5. JohnD

    JohnD

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    Are you thoughts based on guesswork, or have you researched some real-life examples from nearby homeowners?

    Have you got a lot of spare cash lying around, that you need to spend? And no investment ideas that have a positive payback?

    I find the RoI very poor, even though I have a FIT rate of about 18p total. There is good power generation between about 10am and 4pm on sunny days in summer, hardly any at other times. If you do not use the electricity at that time, it is gone, and not available later.

    I looked at storage batteries, but the cost outweighs the benefit.
     
  6. oldbutnotdead

    oldbutnotdead

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    Interesting. From an environmental point of view, good for you. Financially I don't think you'll achieve ROI ever. Not sure what is happening with feed in tarriffs at the moment but unless your kit is installed and commissioned by one of the accredited operators then you won't get any (was my understanding 7 years ago when I looked at this). Without FIT the only way to make the thing pay is to use every drop of energy it creates- which means batteries or thermal store (most of your heat requirements will be when the sun isn't shining). Even then you're assuming the panels, inverters etc won't fall over for 20 years....a long time ago a building I worked in converted from PAR38s to low voltage 50w - look at the energy savings they said. Indeed we saved energy- except we had to heat corridors that had previously been heated by the PAR38s and every transformer failure knocked the ROI back by a year for each fitting.
     
  7. JohnD

    JohnD

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    The sun does not shine on both sides of the roof at the same time.

    Does one side face south? Put them there.
     
  8. Click4B

    Click4B

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    I know that lol, but it means that it will generate maximum it can given weather conditions because it will continue to capture sunlight as the sun moves across the sky, vs if it’s installed on east facing roof only... after midday it will drop off as the sun moves to the west side of the roof.

    unfortunately Don’t have a south facing roof which would capture most of the day :(
     
  9. Click4B

    Click4B

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    not really interested in the return on investment part presently, because if I rent out this house eventually, I won’t be gaining from it anyway... just need something which will give me a solution to try and get away from fossil fuelled heating, and mean electric bills aren’t sky high for whoever rents it so would be more interested in how it averages out over the course of the year... if it means high bills in the autumn winter but next to nothin bills in the spring / summer then it would cost about the same to run electric boiler as a gas one.

    Got a gas boiler here at the moment, but it’s 40 years old roughly this year... it works, but it’s heavy on gas given the pilot light runs 24/7, gas bill this time of the year can be around £100-120 with electric sitting around £30-40 on average. In summer combined bills get as low as £70 but last bill was £150 for December!

    so I am looking to replace it, would of preferred to go down the heat pump route as it will cost about the same as gas to run.

    but if the property becomes rented, it won’t be practical I don’t think due to its low temp and slow heat up times... and if I go gas again it means annual servicing, I can’t touch it if it goes wrong, annual landlord certificates... whereas compared to electric boiler it just sits there maintenance free, no servicing, no red tape involved. just the sky high electric bills at 9kwh to operate. That’s without the government wanting to make a push to reducing co2 emissions and targeting fossil fuelled heating so solar with electric boiler is more sustainable.

    So was hoping that the spring summer electricity reductions from solar would offset the autumn winter high bills so it averaged out.
     
    Last edited: 10 Jan 2020
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  11. JohnD

    JohnD

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    But not the same to install.
     
  12. oldbutnotdead

    oldbutnotdead

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    Somewhere on moneysavingexpert there's a link to a solar pv calculator- supply it your location, panel directions and angles and it'll tell you what those panels will generate when. If you've got the space for a chunky (1000ltr plus) thermal store then you can use that as a battery but at 3kwh/100 litres it won't capture full system output in the summer.
    Personally i think you're overthinking the job, if you can wait til the summer you'll be able to get a gas boiler with 7+ yr warranty supplied and fitted for £1500. Annual service plus annual CP12 costs me £90 per year. Yes there's talk of outlawing domestic gas boilers but right now they're permitted and TCO is low.
     
    Last edited: 10 Jan 2020
  13. Click4B

    Click4B

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    true, but with a monoblock it’s only 1 feed and return which hooks up in place of boiler.
    Would just need an electrical feed put in.

    If anything a mono block is probably easier to install than solar.
     
  14. JohnD

    JohnD

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    Are heat pumps free, then?
     
  15. Click4B

    Click4B

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    No about same as solar to buy, running costs are about same as gas if sized and installed properly
     
  16. JohnD

    JohnD

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    and cost to buy and install?
     
  17. StephenStephen

    StephenStephen

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