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3 phase and MIC implications for PV and EV charging

  • 30-09-2020 8:27pm
    #1
    Registered Users Posts: 200 ✭✭ Caspero


    I'm looking at a PV installation and getting an EV charger in.

    I'd like to put a 22kw charger in to future-proof for faster charging. I also think we'll eventually have a second EV with both charging at the same time. Ideally that would be with 2 x 22kw chargers but 2 x 11kw would also be good if that is not possible, with 2 x 7.4kw being my least preferred but still suitable option.

    I know that my total consumption including the car is going to be more than the production from a 6kw system.

    I was hoping to check whether a few facts that I've read are accurate / still current from anyone who might have had a 3-phase system installed and/or increased their supply.

    Am I right in thinking:
    1. 22kw charging is only possible in a house with 3-phase supply
    2. For domestic users, the only cost associated with adding a 3-phase supply is the up-front cost to upgrade the supply lines etc? So there is no change in monthly standing charges after the supply upgrade to 3-phase (with the caveat for MIC noted below)
    3. MIC (Maximum import capacity) is what determines standing charges for domestic users. If you go over a certain threshold you get charged more.
    4. Anything up to and including 29 kVA MIC costs the same. So the threshold where standing charges start to go up is 29 kVA
    5. If I want to future-proof my supply to the greatest possible extent without incurring extra monthly charges (apart from the variable cost of extra power consumed) then requesting three phase with MIC of 29 kVA would be the best choice because it would allow more power to feed to the system when for example both cars are charging at the same time. The only downside here would be the up-front cost of increasing the supply, and of course the tails upgrade and charger installation etc.
    6. At the tails there isn't extra cost for a 20 kVA system vs a 29 kVA system (I could be wrong on that...haven't really researched it at all)
    7. Having 3-phase increases the maximum permitted PV size from 6kwh (to 11kw? I think). I do understand that space would also be a constraint of course.


    One item I haven't really looked at is the relationship between the kVA of supply and the maximum kwh that can be drawn in the house. Any colour on that would be interesting!

    Thanks all, I've learned a ton from reading the threads here. There are some very knowledgeable people in these parts.


Comments

  • Registered Users Posts: 11,205 ✭✭✭✭ KCross


    I think you might be crossing the line from future proofing to overkill.

    Unless you do ridiculous mileage in BOTH cars everyday you are not going to need that level of power to charge two EVs during night rate.

    Have you worked that out?


  • Registered Users Posts: 200 ✭✭ Caspero


    KCross wrote: »
    I think you might be crossing the line from future proofing to overkill.

    Unless you do ridiculous mileage in BOTH cars everyday you are not going to need that level of power to charge two EVs during night rate.

    Have you worked that out?

    Is there any downside to opting for 29 kVa given that I'm upgrading to 3-phase though? I understand 3-phase is needed for either a 22 kwh charger or for charging 2 cars at 7kw at the same time while not tripping the system or slowing the charger down if you have other stuff in use in the house. If I'm getting 3-phase in anyway, is there a reason not to opt for 29 kVA?

    There could well be - this definitely isn't my area so I'm not challenging your assertion but rather trying to understand the logic behind it.


  • Registered Users Posts: 10,926 ✭✭✭✭ Calahonda52


    I don't believe you are right about all the charges that go with 3P


  • Registered Users Posts: 418 ✭✭ _dof_


    I don't believe you are right about all the charges that go with 3P

    The charges for getting a 3 phase connection are included in this document.

    So, 29kVA is about 700 more expensive than 20kVA, and 3P is more expensive than single phase because of the extra MV network charge, which AFAIK will be different on each property, depending on access to 3P lines nearby.

    There shouldn't be any extra standing charge for 3P.

    As has been pointed out though, the OP doesn't necessarily need 3P just to have 2 EV chargers, unless each car has a 3P charger onboard, and both cars do huge distance every day.

    Otherwise, an enhanced 16kVA single phase connection should be enough to allow both cars to charge simultaneously, with some load limiting or load sharing in the chargepoints like Zappi or Tesla or some others.


  • Registered Users Posts: 200 ✭✭ Caspero


    _dof_ wrote: »
    the extra MV network charge

    Edit: Thanks I'll have to read into this

    As has been pointed out though, the OP doesn't necessarily need 3P just to have 2 EV chargers, unless each car has a 3P charger onboard, and both cars do huge distance every day.

    Leaving aside my current demand for a moment, 3-phase does increase the maximum permitted PV installation from 6kw to 11kw. I like the idea of generating more than I'm consuming to contribute in a small way towards more sustainable energy generation.

    A second reason I'm looking for 3-phase with this installation is that I'm looking to future-proof to the greatest extent I can. I'm not just thinking about the vehicle I have today, but those coming 5, 10 and 20 years down the road. I would like to have the ability to have 2 cars charging at the highest rate possible.

    That being said I obviously have to consider the ongoing cost of having a system that can do that. I'm OK with up-front charges (which I don't think would be high because I'm near a line that can supply 3-phase) but I'm trying to avoid heavy recurring charges.


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  • Registered Users Posts: 9,076 ✭✭✭ antoinolachtnai


    Caspero wrote: »
    Edit: Thanks I'll have to read into this




    Leaving aside my current demand for a moment, 3-phase does increase the maximum permitted PV installation from 6kw to 11kw. I like the idea of generating more than I'm consuming to contribute in a small way towards more sustainable energy generation.

    A second reason I'm looking for 3-phase with this installation is that I'm looking to future-proof to the greatest extent I can. I'm not just thinking about the vehicle I have today, but those coming 5, 10 and 20 years down the road. I would like to have the ability to have 2 cars charging at the highest rate possible.

    That being said I obviously have to consider the ongoing cost of having a system that can do that. I'm OK with up-front charges (which I don't think would be high because I'm near a line that can supply 3-phase) but I'm trying to avoid heavy recurring charges.

    As things stand today for domestic customers, network standing charges are not linked to whether you have three-phase, or to your MIC.

    See the table in the document you link for DG1 (Urban domestic) charges.


  • Registered Users Posts: 11,205 ✭✭✭✭ KCross


    Caspero wrote: »
    I'm looking at a PV installation and getting an EV charger in.

    I'd like to put a 22kw charger in to future-proof for faster charging. I also think we'll eventually have a second EV with both charging at the same time. Ideally that would be with 2 x 22kw chargers but 2 x 11kw would also be good if that is not possible, with 2 x 7.4kw being my least preferred but still suitable option.

    I could be wrong but I think you are looking at this from the point of view of a petrol car owner rather than an EV owner and thinking 22kW charging at home is going to be a benefit. There are very few scenarios where charging at 22kW at home is going to be of benefit to you. Unless you are doing very high daily mileage and needing a really fast topup again to go out later that day it will be significant overkill and may not ever actually be used other than your car is finished charging at 2am instead of 5am.

    e.g. lets say in the future you have 2x100kWh cars that can take 22kW charging. At 100kWh starting in the morning you will have 500-700km's available to you. By the time you get home after a 500km journey are you really going to need to topup at 22kW to go out again that night? A quick stop at a rapid during the day would be easier.

    I understand you want it if it doesnt incur extra ongoing costs so better to be looking at it than for it.... so, fair enough on that front.


    Having 11kW does make sense. If you did get 29kVA the best you could do with that supply is 2 EV's at 11kW as you need headroom for the rest of the house to operate or a load sharing charge point that will split a 22kW supply when the second EV connects.... i.e. one car connected gets 22kW, second car connects both get 11kW.

    You can get dual port 3ph chargers that will support that and that might be useful but not absolutely required to charge two EV's together. There are enough hours during night rate to charge two EV's to full everyday without needing more than 16kVA.



    Am I right in thinking:
    1. 22kw charging is only possible in a house with 3-phase supply
      Yes
    2. For domestic users, the only cost associated with adding a 3-phase supply is the up-front cost to upgrade the supply lines etc? So there is no change in monthly standing charges after the supply upgrade to 3-phase (with the caveat for MIC noted below)
    3. If I want to future-proof my supply to the greatest possible extent without incurring extra monthly charges (apart from the variable cost of extra power consumed) then requesting three phase with MIC of 29 kVA would be the best choice because it would allow more power to feed to the system when for example both cars are charging at the same time. The only downside here would be the up-front cost of increasing the supply, and of course the tails upgrade and charger installation etc.

      You would obviously have to upgrade/reconfigure your house wiring to accommodate 3 phase (not just the tails). You dont just get ESB to hook up 3ph to your existing 1ph house and hey presto you now have 29kVA to use everywhere in the house.

      Your charge point and install will be more expensive also, particularly if you go to 22kW

    4. At the tails there isn't extra cost for a 20 kVA system vs a 29 kVA system (I could be wrong on that...haven't really researched it at all)
      Its a higher kVA so there is likely heavier duty tails required but I'd imagine that wouldnt be a sticking point.
    5. Having 3-phase increases the maximum permitted PV size from 6kwh (to 11kw? I think). I do understand that space would also be a constraint of course.
      Yes, 11kW for export with 3ph. That is a real benfit of getting 3ph alright but you dont need 29kVA to get that.
    Caspero wrote: »
    Is there any downside to opting for 29 kVa given that I'm upgrading to 3-phase though? I understand 3-phase is needed for either a 22 kwh charger or for charging 2 cars at 7kw at the same time while not tripping the system or slowing the charger down if you have other stuff in use in the house.

    16kVA will also cover two EV's charging together. You just need a smart charge point to manage it. As said above, there are enough hours in night rate to fully charge two EV's every night.

    Caspero wrote: »
    If I'm getting 3-phase in anyway, is there a reason not to opt for 29 kVA?

    It's all down to the cost really (ESB costs, house (rewiring), charge point upgrade etc) and until you get ESB to give you a quote for their work you wont get a definitive answer.

    NOTE: It might be worth asking your questions on the electrical forum. They will have more knowledge of costs.


  • Moderators, Category Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 58,861 CMod ✭✭✭✭ unkel


    KCross wrote: »
    16kVA will also cover two EV's charging together.

    Sure. Until someone switches on the kettle. Or the dishwasher. Or the washing machine, or the dryer, or the vacuum cleaner, or the iron...... :p

    "Wind is Ireland's oil" - An Taoiseach, 25/05/2022



  • Registered Users Posts: 11,205 ✭✭✭✭ KCross


    unkel wrote: »
    Sure. Until someone switches on the kettle. Or the dishwasher. Or the washing machine, or the dryer, or the vacuum cleaner, or the iron...... :p

    You left out the next part of my sentence... "You just need a smart charge point to manage it."


    All those things draw small enough amounts of energy and for relatively short bursts of time only.... the car is charging for hours so its not an issue over the full night rate window.


  • Registered Users Posts: 3,911 ✭✭✭ mp3guy


    KCross wrote: »
    You left out the next part of my sentence... "You just need a smart charge point to manage it."


    All those things draw small enough amounts of energy and for relatively short bursts of time only.... the car is charging for hours so its not an issue over the full night rate window.

    Heat pump? Dunno why anyone would want to potentially cripple their future expansion capabilities this early on with a half measure like this, the minimal viable solution.

    If it was me I'd future proof away OP, plan to be able to charge two EVs at 11kW and also feed 11kW surplus from your PV array over 3P back to the grid.


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  • Registered Users Posts: 11,205 ✭✭✭✭ KCross


    mp3guy wrote: »
    Heat pump? Dunno why anyone would want to potentially cripple their future expansion capabilities this early on with a half measure like this, the minimal viable solution.

    If it was me I'd future proof away OP, plan to be able to charge two EVs at 11kW and also feed 11kW surplus from your PV array over 3P back to the grid.

    Not sure if you are agreeing or disagreeing with me? :)

    I agree that 3ph is the way to go. It enables more export, which is a tangible benefit along with the 11kW EV charging.

    Only fly in the ointment I spoke about was 2x22kW being unrealistic and not required. That level of power is commercial in nature and way beyond what you need for domestic scenarios.


    And I'm coming from a position of experience here too... I have a heat pump and have charged two EV's overnight and running together and I have only 1ph but I have the enhanced 16kVA supply so I know whats possible.... 3ph would make it better but going to 2x22kW is just way beyond whats required and of course its ultimately down to what it costs him to get it done (ESB, electrician fees etc).


  • Registered Users Posts: 9,076 ✭✭✭ antoinolachtnai


    Well, the concept is that if you have more capacity, it means that you can take greater advantage of periods of time when electricity prices are near zero when there is half-hourly pricing in the future. You could draw a full 11 kWh to your car in half an hour when electricity prices are zero or negative.

    If you drive a lot, being able to charge at 22kW is going to be an advantage in some circumstances. It doesn't happen often for domestic drivers, but every so often you might need to make a 'quick getaway'. It gives you flexibility.


  • Registered Users Posts: 11,205 ✭✭✭✭ KCross


    Well, the concept is that if you have more capacity, it means that you can take greater advantage of periods of time when electricity prices are near zero when there is half-hourly pricing in the future. You could draw a full 11 kWh to your car in half an hour when electricity prices are zero or negative.

    Thats a good point alright. Is that likely to happen?


  • Registered Users Posts: 9,076 ✭✭✭ antoinolachtnai


    Electricity prices frequently go to near zero or below overnight.

    There are a good few steps to go before consumers will be able to get the most benefit out of these low prices.

    Have a look at prices for Saturday (tomorrow)

    https://www.semopx.com

    Also, having a look at the month of September 2020, price went below 10 euros/MWh wholesale (about 1c/kWh) a good few times:

    ┌────────DeliveryHour─┬─day_ahead_price_EUR─┐
    │ 2020-09-02 01:00:00 │ 9.21 │
    │ 2020-09-02 02:00:00 │ 2.1 │
    │ 2020-09-02 03:00:00 │ 1.93 │
    │ 2020-09-02 04:00:00 │ 5.9 │
    │ 2020-09-11 03:00:00 │ 0.66 │
    │ 2020-09-11 04:00:00 │ 1 │
    │ 2020-09-11 05:00:00 │ 5.3 │
    │ 2020-09-12 20:00:00 │ 4.27 │
    │ 2020-09-12 21:00:00 │ 0 │
    │ 2020-09-12 22:00:00 │ -15 │
    │ 2020-09-12 23:00:00 │ -15.03 │
    │ 2020-09-13 00:00:00 │ -15.03 │
    │ 2020-09-13 01:00:00 │ -15.03 │
    │ 2020-09-13 02:00:00 │ -15.63 │
    │ 2020-09-13 03:00:00 │ -15.63 │
    │ 2020-09-13 04:00:00 │ -15.38 │
    │ 2020-09-13 05:00:00 │ -15.03 │
    │ 2020-09-13 06:00:00 │ -10.8 │
    │ 2020-09-13 07:00:00 │ 0 │
    │ 2020-09-29 22:00:00 │ -2.04 │
    │ 2020-09-29 23:00:00 │ -4.82 │
    │ 2020-09-30 00:00:00 │ -4.82 │
    │ 2020-09-30 01:00:00 │ -0.04 │
    └─────────────────────┴─────────────────────┘

    The 'imbalance price' also flies around a good bit. It went as low as minus 198 on 30 September (presumably because there was an excess of wind on the grid).

    https://www.sem-o.com/market-data/dynamic-reports/#BM-026


  • Moderators, Category Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 58,861 CMod ✭✭✭✭ unkel


    If you drive a lot, being able to charge at 22kW is going to be an advantage in some circumstances.

    Or if you don't drive a lot. I'd love a smart charger to automatically stick 66kWh into my car over 3 hours when prices are near zero. The utility company can then buy it back from me during peak hours the next day for 500-1000% of what I paid. Failing that, the car can then power my house for a week. Practically for free.

    "Wind is Ireland's oil" - An Taoiseach, 25/05/2022



  • Registered Users Posts: 200 ✭✭ Caspero


    unkel wrote: »
    Or if you don't drive a lot. I'd love a smart charger to automatically stick 66kWh into my car over 3 hours when prices are near zero. The utility company can then buy it back from me during peak hours the next day for 500-1000% of what I paid. Failing that, the car can then power my house for a week. Practically for free.

    Interesting! Have you currently got the hardware to do that or are you talking about doing that in the future?

    If you have it now, did you buy it from overseas?

    I read about Leaf owners being able to do this in some countries...seems like a very rational way to balance grid supply/demand


  • Moderators, Category Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 58,861 CMod ✭✭✭✭ unkel


    I have the hardware to do all that. But I have to do it manually. And my house only has a 1 phase connection, so my charge point which is not smart, can only supply 7.4kW to the car and it is not bi-directional

    But technically I could drive to a Tesla supercharger every few days, charge the car up for free, drive home and connect a 48V charger to the inverter that I have built into my car, and charge up my powerwall in my house from my car. I also have a large solar PV setup. If I wanted to, I could have a near zero electricity bill.

    "Wind is Ireland's oil" - An Taoiseach, 25/05/2022



  • Moderators, Sports Moderators Posts: 16,061 Mod ✭✭✭✭ slave1


    ...and therein lies the strong advantage of the CHAdeMO system which allows charging in both directions, the Leaf CHAdeMO is already setup for Vehicle 2 Grid charging (V2G), park up any Leaf and away you go with no complications. Wallbox have bi-directional charge points right now!


  • Moderators, Category Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 58,861 CMod ✭✭✭✭ unkel


    slave1 wrote: »
    ...and therein lies the strong advantage of the CHAdeMO system which allows charging in both directions, the Leaf CHAdeMO is already setup for Vehicle 2 Grid charging (V2G), park up any Leaf and away you go with no complications.

    Yeah. The only complication is that you'd have to get a CHAdeMO V2H charger. Last time I looked these cost €3k + shipping costs + VAT + duty from the far east

    System looks nice on paper, but would never ever pay for itself if you'd have to fork out costs like that

    You don't need DC charging to be bi-directional either, not sure why people are focussing on that. AC is much easier and cheaper

    "Wind is Ireland's oil" - An Taoiseach, 25/05/2022



  • Registered Users Posts: 200 ✭✭ Caspero


    unkel wrote: »
    Yeah. The only complication is that you'd have to get a CHAdeMO V2H charger. Last time I looked these cost €3k + shipping costs + VAT + duty from the far east

    System looks nice on paper, but would never ever pay for itself if you'd have to fork out costs like that

    You don't need DC charging to be bi-directional either, not sure why people are focussing on that. AC is much easier and cheaper

    So what's your setup Unkel?


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  • Moderators, Category Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 58,861 CMod ✭✭✭✭ unkel


    See above. Nothing V2H I have is automated, but I have an AC inverter in my car, so I could charge up my power wall from my car with my variable voltage DC charger. The power wall powers the house when the solar PV doesn't generate enough power

    "Wind is Ireland's oil" - An Taoiseach, 25/05/2022



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