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On-grid domestic battery storage

edited 30 November -1 at 1:00AM in Green & Ethical MoneySaving
1.8K replies 199.4K views
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  • orreryorrery Forumite
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    JKenH wrote: »
    Finally, I have the ok to post links so here is an example of the Moixa Dashboard which shows instantaneous energy flows...


    This all seems to show a limitation in that you are both exporting surplus to the grid and then running out of power overnight. Is this because the batteries are undersized or is there a limitation in the ability to recharge fast enough?
    4kWp, Panels: 16 Hyundai HIS250MG, Inverter: SMA Sunny Boy 4000TL, SolarImmersion
    Location: Bedford, Roof: South East facing, 20 degree pitch
    Nissan Leaf, TADO Central Heating control
  • edited 27 July 2018 at 12:33PM
    zeupaterzeupater Forumite
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    edited 27 July 2018 at 12:33PM
    orrery wrote: »
    This all seems to show a limitation in that you are both exporting surplus to the grid and then running out of power overnight. Is this because the batteries are undersized or is there a limitation in the ability to recharge fast enough?
    Hi

    In reality the battery is simply sized to reduce peak evening demand and little else.

    With such small battery storage capacity it's almost impossible for the majority of homes to be powered by stored solar energy throughout the night & I'm pretty sure that anyone operating a DES (Distributed Energy Storage) scheme such as grid-share would be aware that calling on energy at peak times would severely deplete such a small battery, leaving the owner with little for their own overnight requirements ....

    Overall the concept is good, it's the application of that concept & the design capacity that is questionable ... the only way to look at this logically is that someone's marketing & selling packaged batteries to consumers at ~£1500/kWh whilst they can get away with it!

    HTH
    Z
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    B)
  • edited 28 July 2018 at 3:04PM
    JKenHJKenH Forumite
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    edited 28 July 2018 at 3:04PM
    orrery wrote: »
    This all seems to show a limitation in that you are both exporting surplus to the grid and then running out of power overnight. Is this because the batteries are undersized or is there a limitation in the ability to recharge fast enough?

    You are right on both counts. The Moixa battery is only able to charge at about 0.38 kw and discharge at max 0.45 kw. I am not sure why that is but no doubt some electrical engineer might be able to explain the advantages of such low rates. If it could discharge at 3kw and then recharge at the same rate it would be a lot more useful but presumably this would impact on the longevity and cost of the battery. I read that the Tesla Powerwall can in fact discharge at 3kw.

    We are running out of power overnight and this is summertime so it will run out even sooner in the winter. Having said that our consumption is very high at the moment as we have my daughter and family camping out with us for several weeks while they are in the UK and turning TVs, lights off etc is an alien concept. We are currently consuming about 25kwh per day!

    I have noticed on forums that the overriding discussion regarding batteries is how cost ineffective they are. I wonder how many of us do the same sums when considering our next phone upgrade or buying a new premium car or even clothes when the old ones are perfectly serviceable?

    Battery technology as it exists at the moment is not really a great investment for most people who have far better things to spend their money on. We are retired though and see the solar installation as an alternative investment which may provide a rate of return of between 5 and 10 percent depending on which figures you believe and whether you include electricity savings. That return is index linked and I believe better value than an annuity. We have other modest investments that are at the whim of the markets and we consider this a low risk/low return investment suitable for our situation. If I was 30 with 2 young children I would probably see it differently.

    Our investment In solar panels and a battery is focussing our attention on how best to use what we are producing and minimise what we consume from the grid. To some extent getting a battery is, like solar panels, a lifestyle choice.. For us a battery was an integral part of going solar. On the advice of othe forum members we are now looking at other modest lifestyle changes such as switching to an LED TV to replace our plasma one, and smoothing out the peaks of our electricity consumption by using a lower wattage kettle, slow cooker, lower wattage toaster etc as well as timing the use of appliances to maximise our solar output.

    I am not an evangelist for solar panels or batteries. We have made a decision because we felt it was the right thing for us. The sums wont work for everyone.
    Northern Lincolnshire. 7.8 kWp system, (4.2 kw west facing panels , 3.6 kw east facing), Solis inverters, Solar IBoost water heater, Mitsubishi SRK35ZS-S and SRK20ZS-S Wall Mounted Inverter Heat Pumps, Nissan Leaf (plus some ICEs:) )
  • CoastalwatchCoastalwatch Forumite
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    My sentiments too JKenh, as I suspect others would agree also. We all have to find our own path through the maze. But wow, it's makes a refreshing change from working for a living, while also pointing a clean way forward to the following generations!
    East coast, lat 51.97. 8.26kw SSE, 23° pitch + 0.59kw WSW vertical. Nissan Leaf plus one dirty diesel. Still waiting for V2H and home storage to become available at sensible cost.
  • edited 28 July 2018 at 6:05AM
    JKenHJKenH Forumite
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    edited 28 July 2018 at 6:05AM
    Yesterday was a bad day for the battery, only reaching 84% despite 26kwh being generated. Exhausted by 10pm but so was I. Even worse was how we managed to maximise our usage when the sun wasn!!!8217;t shining. Managed to consume 30kwh. The family are going home in 2 weeks time so things might improve.

    I have attached an image of how not to lead a solar life.

    https://www.dropbox.com/s/ay8zfwkm4ubbaju/Photo%2015-07-2018%2C%2022%2027%2057.jpg?dl=0
    Northern Lincolnshire. 7.8 kWp system, (4.2 kw west facing panels , 3.6 kw east facing), Solis inverters, Solar IBoost water heater, Mitsubishi SRK35ZS-S and SRK20ZS-S Wall Mounted Inverter Heat Pumps, Nissan Leaf (plus some ICEs:) )
  • Martyn1981Martyn1981 Forumite
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    JKenH wrote: »
    You are right on both counts. The Moixa!!!8217;s battery is only able to charge at about 0.38 kw and discharge at max 0.45 kw. I am not sure why that is but no doubt some electrical engineer might be able to explain the advantages of such low rates. If it could discharge at 3kw and then recharge at the same rate it would be a lot more useful but presumably this would impact on the longevity and cost of the battery. I read that the Tesla Powerwall can in fact discharge at 3kw.

    Those charge/discharge figures remind me of the 1.2kWh Enphase batts. The good news being that as you stack more batts, each one can take that charge/discharge so the numbers rise proportionally with the amount of batts installed.

    Seems like a good idea catching the first bit of charge/discharge, then building up as you decide to go bigger (or not).

    BTW, the Powerwall II can discharge at 5kW or 7kW briefly. I think that's why they may require clearance from the DNO as technically they could exceed the 3.68kW rule, though I doubt anyone wants to discharge their batt leccy to the grid, unless paid to do so.
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
  • Martyn1981Martyn1981 Forumite
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    This article shows what can be achieved if the local grid works with households and domestic storage:

    Network Of Tesla Powerwall Batteries Saves Green Mountain Power $500,000 During Heat Wave
    Last year, Green Mountain Power started offering 2,000 customers a chance to own a Tesla Powerwall residential storage battery for as little as $1,500 and $15 a month for 10 years. But there was a catch. All those Powerwalls would be accessible by the utility company to help stabilize the grid and supply extra electricity, when needed.

    The program represented a significant cash outlay for Green Mountain Power. The cost of a Powerwall system plus installation is about $5,500, so the company was investing $8 million of its own money up front and betting it would recoup that investment over time. Now the company says its virtual power plant system saved it $500,000 in just one week this month as temperatures soared into the 90s.

    "for as little as $1,500 and $15 a month for 10 years." That's $3,300 ..... I'm in!
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
  • orreryorrery Forumite
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    JKenH wrote: »
    I am not an evangelist for solar panels or batteries. We have made a decision because we felt it was the right thing for us. The sums won!!!8217;t work for everyone.


    I suspect that there is a danger of conflating solar PV with batteries here. Solar PV is a no-brainer. Every roof should be covered in the stuff, in every orientation.


    I too would be willing to invest in a battery system for purely environmental reasons, provided I can see that it will wash its own face financially. I just can't see that we are anywhere near at the moment and I see no pressure to move in order to 'prime the pumps' - electric car production will force the battery prices down rapidly.


    The danger here is that those who can't do the sums will be sucked in to make an investment without understanding the basics - a friend called me whilst she had a salesman at her house and told me that the batteries were "A4 sized" (I assume she meant the paper not the car!), that it would pay back in 5 years and that she was being offered £4k discount to sign now.


    I told her to send him round to me first and convince me with the numbers - if it were true then he'd sell two systems as I'd order a one too, but he chose not to come and so she didn't order.
    4kWp, Panels: 16 Hyundai HIS250MG, Inverter: SMA Sunny Boy 4000TL, SolarImmersion
    Location: Bedford, Roof: South East facing, 20 degree pitch
    Nissan Leaf, TADO Central Heating control
  • edited 28 July 2018 at 4:22PM
    ASavvyBuyerASavvyBuyer Forumite
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    edited 28 July 2018 at 4:22PM
    orrery wrote: »
    I suspect that there is a danger of conflating solar PV with batteries here. Solar PV is a no-brainer. Every roof should be covered in the stuff, in every orientation.

    I too would be willing to invest in a battery system for purely environmental reasons, provided I can see that it will wash its own face financially. I just can't see that we are anywhere near at the moment and I see no pressure to move in order to 'prime the pumps' - electric car production will force the battery prices down rapidly.

    The danger here is that those who can't do the sums will be sucked in to make an investment without understanding the basics - a friend called me whilst she had a salesman at her house and told me that the batteries were "A4 sized" (I assume she meant the paper not the car!), that it would pay back in 5 years and that she was being offered £4k discount to sign now.

    I told her to send him round to me first and convince me with the numbers - if it were true then he'd sell two systems as I'd order a one too, but he chose not to come and so she didn't order.


    I agree; I have recently been looking at the economics of adding a battery to our system, as it is something I would like to do to be even greener.

    However, unlike Solar PV, that has a positive return; as an investment, a battery system is currently impossible to justify as it works out as a negative return.

    Even if it saved a maximum of £200 a year on our electric bill, the depreciation on a £4k battery that will only last 10 years is £400 a year, so a net loss of £200 a year.

    So it is not even a low risk investment, as it is guaranteed to make a loss.

    Just leaving the £4k in a 1% fixed interest account would earn more.

    IMO, there are currently greener ways to spend that money, like opting for a supplier that only pays for it supplies from renewal energy sources, investing in an ASHP to help minimise gas use, saving up to get an electric vehicle, etc.

    Also, when something like this becomes available in the UK, it could be worthwhile.
    4kWp, W roof, 30° pitch, Solar Edge Inverter + Optimisers. South Wales Valleys, Installed Aug 2015. Octopus Agile Electric Tariff.
    Solic 200 Diverter, Toshiba Ultra High Efficiency Air Conditioner/Heat Pump, Kia Soul & Renault Zoe EV's.
  • Martyn1981Martyn1981 Forumite
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    orrery wrote: »
    I too would be willing to invest in a battery system for purely environmental reasons, provided I can see that it will wash its own face financially. I just can't see that we are anywhere near at the moment and I see no pressure to move in order to 'prime the pumps' - electric car production will force the battery prices down rapidly.

    I think you've summed it up perfectly. Playing Devil's advocate I can point to PV + storage reducing FF leccy generation in the evening when the grid has the highest CO2 levels, but Savvy has nailed that issue by pointing out that other green investments are possible.

    I commend anyone getting a battery for environmental reasons and helping to prime the pump, but unlike my steadfast support for PV, I'm not as concerned about batts as EV's will now, without any doubt whatsoever, drive up demand and supply massively, so we don't need to tinker.

    That said, I can see how a joint venture between the DNO's and pro-sumers (producer/consumers) like us could have financial benefits for everyone, so keep my fingers crossed for more (and better) offerings.

    But ...... I really want a battery to play with!
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
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