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PV, smart meters, batteries, hot water heaters and feeding the grid

  • 08-10-2020 9:40pm
    #1
    Registered Users Posts: 198 ✭✭ Caspero


    I have room for a PV installation at the back of my garden that will at times produce more power than my house uses. I have an EV so excess production will go into that whenever possible, but it won't be there during the day for the most part. I'm wondering what to do with excess PV production when the car's not at the house in the system I'm planning.

    I read that smart meters are coming next year along with better scope for selling back into the grid.

    Does that mean that hot water heaters (and batteries) are not a good option for a PV system being installed today - particularly one with an EV in the house where there is scope for capturing some of the excess production into the EV battery?

    Batteries look quite expensive vs their size. I'm guessing heating hot water isn't a super efficient use of excess power although the hardware is cheaper.

    Also, what happens with excess PV production today if there is no hot water heater or battery? Goes back into the grid but you don't get paid for it? Is any special planning or hardware required to plan ahead for feeding into the grid?


Comments

  • Registered Users Posts: 2,685 ✭✭✭ graememk


    Caspero wrote: »
    I have room for a PV installation at the back of my garden that will at times produce more power than my house uses. I have an EV so excess production will go into that whenever possible, but it won't be there during the day for the most part. I'm wondering what to do with excess PV production when the car's not at the house in the system I'm planning.

    I read that smart meters are coming next year along with better scope for selling back into the grid.

    Yep a FIT is "coming" nothing properly announced yet, will need a smart meter to use it
    Caspero wrote: »
    Does that mean that hot water heaters (and batteries) are not a good option for a PV system being installed today - particularly one with an EV in the house where there is scope for capturing some of the excess production into the EV battery?

    Yes, its often cheaper to heat water via oil or gas which is around 5c/kwh, but if you have a lot of hot water use, it might be viable, if it can be picked up cheap. OR you have another reason i.e., your hot water comes from solid fuel, and you don't want to be putting fires on in the summer because its too hot.
    Caspero wrote: »
    Batteries look quite expensive vs their size. I'm guessing heating hot water isn't a super efficient use of excess power although the hardware is cheaper.

    Yes, they are included in a lot of solar projects as they allow for a higher grant 3000 vs 1800 for a straight solar system, there is only 600 euro for the actual battery system, the rest is for extra panels.
    Caspero wrote: »
    Also, what happens with excess PV production today if there is no hot water heater or battery? Goes back into the grid but you don't get paid for it? Is any special planning or hardware required to plan ahead for feeding into the grid?

    Just flows back out to the grid, No special equipment needed, inverters are designed to be grid tied. No payment for it. (the old spinning disc meters do turn backwards i hear, sometimes the ESB are slow in changing them)

    The water analogy still works quite well, think of the grid and your inverter as pumps and if your generating more than you can use, it flows out, and if your inverter cant generate enough it lets the grid make up the difference.

    you can be a bit more pro active too, think its going to be a good day, set the dishwasher/washing machine to run around midday

    The solar system I be chatting about is on my fathers house. Im currently planning mine, which will be on a shed(Farmyard) and thinking of going for the full 6kw inverter as really its not much more than a 4kw one.

    Also to put a few extra panels on a low pitch steel roof isnt that hard, If im up there anyway whats another few panels, thinking of going for 24 in total.


  • Registered Users Posts: 125 ✭✭ Ballylad


    I was looking at a fronius 8.2kw single phase inverter, that have a system that can limit the inverter to prevent export to grid at a specified level, would this satisfy esb 6.0kw export limit rule , obviously the idea will be to use all energy produced. Thnks


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