Excess solar power

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  • rugbyleaguesmate
    rugbyleaguesmate Posts: 281 Forumite
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    Or maybe a fork lift battery surely there's a way
    6.72kw Pv Ja Solar 280w * 24 panels, Solar Edge inverter, South facing no shading.
    South Lake District, delightful view of Morecambe Bay. Not Saving up for a battery too expensive:j:mad::hello:

    July Solar target 769kw
  • rugbyleaguesmate
    rugbyleaguesmate Posts: 281 Forumite
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    So reading this post with slightly less rum in my body, it sounds like I need something that diverts the excess electricity I produce and puts it into something that I can benefit from.

    That could be water, heating radiators, a battery anything else?
    6.72kw Pv Ja Solar 280w * 24 panels, Solar Edge inverter, South facing no shading.
    South Lake District, delightful view of Morecambe Bay. Not Saving up for a battery too expensive:j:mad::hello:

    July Solar target 769kw
  • ajbell
    ajbell Posts: 1,151 Forumite
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    Yes, you need an iboost or similar to divert excess electricity to some other use.
    I have an iboost and it has given me a couple of tanks of hot water every day from spring until this month when occasionally I have to boost it with the gas boiler.
    I don't like exporting power after the hot water tank is hot so am looking at a second diversion into a radiator of some kind.
    Ideally battery storage would be great but not really practical at the moment.
    Am also open to any other ideas.
    4kWp, South facing, 16 x phono solar panels, Solis inverter, Lincolnshire.
  • ASavvyBuyer
    ASavvyBuyer Posts: 1,737 Forumite
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    rugbyleaguesmate wrote: »
    So reading this post with slightly less rum in my body, it sounds like I need something that diverts the excess electricity I produce and puts it into something that I can benefit from. ..
    Yes, there are various makes of diverter around. The most efficient ones cost the most, but give you more benefit. But it is a case of working out whether it is economical to do so in terms of the equivalent cost of other sources of energy and the payback time. For example; gas is usually about 2-3p per kilowatt (depending on your supplier). So the cost benefit ratio needs to be worked out on that basis (not how much your electricity supplier charges for imported electricity).
    For us, with West facing panels, we worked out that it was more economical to go for a simpler switching diverter from REUK that diverts power to the water tank circuit whenever we are generating more than we are using for over a minute. It does this by monitoring the red LED on the import meter. If the power then used is too high, causing the red LED to go out or start flashing, it switches the diversion off in less than 5 seconds. That is why we put a 2kw dimmer (off ebay) into the circuit, so that on days of poorer generation, we can limit the amount of power being diverted. Also added a socket in the lounge on the water tank circuit, so that we can plug in the electric oil radiator at this time of year.
    As already said, its not the most efficient diverter, but it only cost £30 and was very easy to install into the existing circuit.
  • ajbell
    ajbell Posts: 1,151 Forumite
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    Done it! Wired a 13a fused single socket to the second output and plugged in a 700w oil filled radiator, as soon as the water tank was hot it switched to output 2 and started putting 0.83kw into the radiator.
    Any idea why my 700w radiator draws 0.83kw?.
    4kWp, South facing, 16 x phono solar panels, Solis inverter, Lincolnshire.
  • ASavvyBuyer
    ASavvyBuyer Posts: 1,737 Forumite
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    ajbell wrote: »
    Any idea why my 700w radiator draws 0.83kw?.

    They usually draw a bit more than what it says on the box; especially when first starting up, as the element is cold then and has less resistance. Our oil filled radiator, when on the 500 watt setting, usually takes about 600 watts when it first comes on, but then reduces down to about 550 when hot.
  • silverwhistle
    silverwhistle Posts: 3,791 Forumite
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    ASavvyBuyer wrote: »
    But it is a case of working out whether it is economical to do so in terms of the equivalent cost of other sources of energy and the payback time. For example; gas is usually about 2-3p per kilowatt (depending on your supplier). So the cost benefit ratio needs to be worked out on that basis

    You're right, but my gas costs with VAT over 5p a unit as I'm on a free standing charge tariff. As my total gas bill is still under £40 a year I'm happy enough! Friday was the first day since spring that I've had my boiler on for hot water. I've saved over 3500 units since installation just over three years ago so I reckon my iboost has paid for itself.

    I've had a hot air heater on controlled manually but haven't bothered with the faff of a second diverter. I did turn up the thermostat on the tank though for maximum saving.
  • zeupater
    zeupater Posts: 5,355 Forumite
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    silverwhistle wrote: »
    ... my gas costs with VAT over 5p a unit as I'm on a free standing charge tariff. As my total gas bill is still under £40 a year I'm happy enough! ...
    ... I recognise that approach as well as those costs and even the total annualised bill .... :D

    If you're not freezing cold when you're happy, well done .... :)
    Z
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    B)
  • pinnks
    pinnks Posts: 1,259 Forumite
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    I agree that gas is cheaper per kWh but do forget the system looses when using the GCH to heat only water. Boiler efficiency compared to an immersion heater, losses in pipes between boiler and tank (and back) and so on. I use about 3 times the kWh of gas to heat water in the summer as I do electricity and can see that using a divert saves me between £70 and £80 on gas over the summer months and possibly about £20 over the rest of the year - and this equates to using leccy unit prices for the diverted kWh
  • silverwhistle
    silverwhistle Posts: 3,791 Forumite
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    zeupater wrote: »
    ... I recognise that approach as well as those costs and even the total annualised bill .... :D

    If you're not freezing cold when you're happy, well done .... :)
    Z


    Thank you. I have no intention of getting cold, even if as a skier I'm used to it a bit. Only just seen this as I've been spending my ill-gained FIT and savings on my cheap fuel bills on a short trip away - not a cruise, might I add..

    In terms of payback on my capital it's very difficult to work out the savings overall. I'm pleased with the bottom line results on my bills but how do I cost the gas I save? Annually put 1120 kWh to water but, as pinnks points out, efficiencies and unit rates/standing charges obscure the issue.
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