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Excess Solar Power Diverter

Discussion in 'General Electronics Discussion' started by jimbo, Nov 17, 2012.

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  1. jimbo

    jimbo

    5
    1
    Nov 15, 2012
    Does any one have a circuit which will compare the ac feed from a solar panel array on a house roof and the incoming mains ac feed to the house and divert any excess solar powered electricity into a heating load in the house. The purpose of this is to allow all the solar powered electricity to be used in the house? The ac current sensing should use clip-on current transformers to avoid interfering with the main house incomer and solar array feed.
     
  2. davenn

    davenn Moderator

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    Sep 5, 2009
    hey jimbo
    welcome to the forums :)

    Solar panels produce DC. Maybe your panel is feeing batteries that then supply a DC to AC inverter ??

    Dave
     
  3. jimbo

    jimbo

    5
    1
    Nov 15, 2012
    Jimbo

    Hi Dave,

    Thanks for the reply.

    Yes the panels do produce DC which is inverted, DC to AC, to provide AC and fed into the house's incoming AC supply from the grid.

    When the power demand in the house is more than the panels can provide, current is drawn into the house from the grid. When the panels provide more power than the house needs, it is exported into the grid, but this extra power could be better used in the house for heating. This system avoids the need for batteries but does result in any excess power leaving the house and consequently I would like to have a system which would automatically divert excess power into a heating load particulalry in the Scottish winter!

    Jim
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
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    Jan 21, 2010
    I can meter the house load and the generation of my solar panels individually.

    In my case it's better to export all the power I can, because it offsets my use, however I understand that might not be the exact case everywhere.

    If you can measure the loads the same way, you can simply read both loads and increase (or decrease) your heating until both are equal.

    The problem with many of these power monitors is that they can't distinguish between 1000W load and 1000W exported.

    If you have a smart power meter (which CAN tell the difference) and you can monitor your load that way, then you would modulate your heating to keep the load as close to zero as possible.
     
  5. jimbo

    jimbo

    5
    1
    Nov 15, 2012
    Steve

    The stuation is as you anticipate.

    I can monitor the house load and the generation of my solar panels individually but the monitors can't distinquish between import and export.

    The value of export power is very low compared to its value when retained within the house for heating as the offset price is so low.

    I have a traditional rotating disk power meter but might be able to get it replaced with a smart meter to allow modulation of the heating load and I will explore this.

    Thanks.
     
  6. martinW

    martinW

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    0
    Mar 17, 2013
    Simple export monitor

    I have a very simple monitor, cost about £5 which works if you have a modern electronic meter with a flashing LED to show power usage. , OK if you are around to make use of it. Simply fix a phototransistor over the LED in the meter box, run two thin wires back into the house (I have a tumble dryer outlet next to my meter box). amplify the PT output (dalington pair sufficient, and run an LED indoors.
    LED on all the time = export
    LED off = balanced
    LED flashing = importing at the rate of 1WH/flash

    I have a Sunnybeam monitor, but in time can judge what load I can put on anyway.

    I was working on a means of converting the LED o/p into a drive for a thyristor via an RF link but the price of commercial power diverters has fallen so mauch since I started that it is no longer worth the hassle and risk associated with a home made device.

    Hope this helps if anyone is just looking for a very cheap monitor.
     
  7. solga

    solga

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    0
    Apr 30, 2014
    Yes trying to find when exporting to grid. Maybe halleffect sensing or trying to read utility metet infer red output port would provide info. Are there any links that might shead light on this subject?maybe timer with trigger on export direction?
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    I had exactly the same situation when a solar system was installed in my house.

    The grid connect inverter already gives excellent reporting of power exported. I had the installers wire up the monitor so that it measured *only* load to the house (essentially they left the wire from the inverter out of the current sensor).

    This allows me to see my house load and my generation separately. Since my grid connect inverter only exports, and the rest of my house is just a load, there is never any confusion as to which way the power is flowing.

    The message above which talks about the flashing LED is great if you have a smart meter. In my case I have 3 phase and one LED that seems to give a result that sumarises total import vs export. That's not great for me because I can be exporting on one phase and importing on another. In my case that's fine because I get paid more to generate than the consume (or at least I will for the next 6 years or so).
     
  9. solga

    solga

    3
    0
    Apr 30, 2014
    My state PSC chose not to provide net metering to the solar customers. This means no credit for excess KWH generated and the utility Co. sells my excess , don't move to Ga. This is why I am trying to come up with a detector and diverter. Current Cost has a monitoring system that can do this wireless, I think. This get expensive, so I haven't done it yet. I am operating on a limited budget.
    I presently have a current cost monitor so I probably get a cc sensor for solar . Detector and wireless switch to expensive at this time; rather purchased panels. But will keep looking for affordable detectors and switch. A DIY system.
     
    Last edited by a moderator: May 29, 2014
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