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The Future of EV Home Charging and the Grid

Discussion in 'Energy, Environment, and Policy' started by gnuarm, Jan 17, 2019.

  1. gnuarm

    gnuarm Model X 100 with 72 kW chargers

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    The typical home built in the last 40 years has 200 amp service and so can draw up to 40 kW continuously. I've read the distribution grid is designed for an average load of 4 to 6 kW per home. Can anyone confirm this number?

    Depending on the part of the US you live in many homes use a heat pump and in the winter when temperatures are low can draw up to 12 kW pretty much all night. I have seen this on my own home since my utility provided hourly usage data a couple of years ago. So that alone has got to come close to maxing out the local distribution grid. I guess I should contact my utility and ask them to what loads the distribution grid is designed.

    So my question is what will EV charging at night do to stressing the distribution grid? At 32 amps a Tesla mobile cable will add 8 more kW to the above number making it 20 kW for some portion of the night or even all night if a full charge is needed. My car will charge at 72 amps or 17 kW, even more power than my furnace uses to heat the house from straight electricity.

    Widespread adoption of TOU billing for car charging will get people charging at night, but that solves a different problem, daytime peak generation charges to the utility. They are always on a sort of TOU billing and have to pay top dollar for peak generation. But overloading of the local grid is a different matter entirely.

    My concern is that the utilities are looking at the problem and will delay action so they can wait for it to become an "emergency", then get approval to implement plans that will be solely to their benefit and not very useful to EV owners. What seems ideal (but maybe not so practical) is for home EVSE (charging units) to be on the network so the utility can control them. When you want your car charged you get on the web site or use an app to indicate when you need the car and how much charge you want and the utility schedules the charging to keep the distribution grid balanced and meet your objectives.

    This may be an ambitious project. But short of paying a bunch of money to the utility for them to beef up distribution, I don't see how we could even achieve 10% market penetration with home charged EVs without something like this.

    Maybe I don't understand the distribution grid at all and there won't be a problem. But from what I've read, this will be a problem in less than 10 years and utilities aren't noted for being fleet of foot. If we don't do something to force action we may have some very onerous billing or operational changes jammed down our throats.
     
  2. eprosenx

    eprosenx Active Member

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    I am not worried about this in my area for a number of reasons:

    1. My utility Portland General Electric is fantastic and they are constantly monitoring loads and adjusting the distribution system as needed. They have some amazing databases of how everything is hooked up (like what transformer and phase you are hooked to) and so that combined with 15 minute resolution on the smart meters allows them to keep tabs on things. While load in residential has been flat or gone down in recent years due to conservation a good example of capacity upgrades is in the area my Datacenters are in. They are *constantly* upgrading substation transformers, transmission lines, distribution lines, etc... They also swing load between feeders constantly to manage the load. As residential load grows they will do the same as necessary.

    2. The reality is that I think this is going to be solved in the more general case via technology.

    The entire grid is built based on peak loads. AC in the summer and heating in the winter. Different areas have different characteristics (places with natural gas don’t have a solution big of winter peaks). So even in the high load times of year there are many hours of the day where loads are nowhere near peak.

    The solution is going to be to use technology to get the cars to charge during the valleys.

    PGE already pays me to allow them to tweak my Nest thermostat settings by a few degrees on a handful of days out of the year (when the grid is stressed and the spot market power price is high).

    An EV is the definition of a perfect device to time shift. It quite literally is a huge battery that is already internet connected!

    So I personally only use a tiny fraction of my battery power each day to commute. I could (with the right financial incentives) be convinced to let the power company control the time of day my car charges and I could even go as far as to let them skip a day of charging if there just was no good window overnight. I am in a good spot since I installed a 60a circuit for my M3 so that if I needed to, I could fit my charging window into a short time period. People that have very slow charging setups have less flexibility on when they can charge.

    So yeah, while this is an issue, I think it is surmountable.
     
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  3. gnuarm

    gnuarm Model X 100 with 72 kW chargers

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    Yeah, in Portland (Oregon I assume) you may not have the winter consumption we have here. But I don't think you realize the magnitude of the problem. If you don't have the high residential heating loads on cold winter nights which are much greater than the peak days of summer AC, that only means instead of having problems starting at 5 or 10 % EV market penetration, you will see the problem at 20 or 25% penetration (picking numbers from air really). I don't have exact numbers because I don't know the exact average household power number they use for planning distribution. Actually, the difference in existing loads would mean your area might well see the problem earlier than here since your system may be designed with lighter average load numbers.

    While your area may be on top of the daily cycles of use and switch loads around to keep it all even, that does not equate to being able to double the total distribution capacity. Think of it this way. They build new superhighways all the time as areas grow to keep up with traffic. But now instead of adding new housing developments and office buildings on the outskirts of town every couple of months, now they are turning all your homes into duplexes and triplexes doubling and tripling the traffic locally before you get to the highways. Now you will need bigger roads locally and there isn't much to do about it unless you find ways to get people to leave their homes at different times and have ways to schedule that to make sure it happens in a controlled way. Saying they are very good at fixing potholes and broken traffic lights isn't going to solve this problem.

    Is that a better analogy?
     
  4. gnuarm

    gnuarm Model X 100 with 72 kW chargers

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    To follow up, yes, the problem is largely surmountable... which is exactly my point. To do so will require new technology, not that it is terribly advanced other than the controlling software. The issue is that the utilities won't be pushing such advances. They will just say they need lots of money to lay more local power lines. Remember they are regulated and their earnings are based on capital investment, not income. So they would love to justify more distribution at your expense.

    If we don't get the ball rolling on this it will end up driven by the utilities in a "panic" situation since it takes time to upgrade the infrastructure of the distribution grid. If we don't push early to solve the problem by coordinating car charging, we will lose the opportunity.
     
  5. swaltner

    swaltner Active Member

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    You’re lucky that PGE provides a financial incentive to let them adjust your Nest. Here in Kansas, Westar had a program that let them shutdown your air conditioner during peak times with “no” financial incentive provided. You didn’t receive any kind of adjustment when they shut your AC off. The only incentive was that you received a programmable thermostat that they had access to. A programmable thermostat is something like $20 at the local hardware store. I don’t think they got very many takers on this program.

    WattSaver program overview – 24-hour technical support and year-round savings

    Of course, this is also the same utility company that is searching for 1,000 people to try out a TOU plan. Their idea is to lower your night rate by just 2 cents/kWh, but raise the day right by 8 cents. How could you save money at that?
     
  6. BerTX

    BerTX Supporting Member

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    Why is this a Model 3 topic? Interesting discussion, though.
     
  7. StealthP3D

    StealthP3D Active Member

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    If you're drawing that much you have a problem. Either your McMansion is way too big or the "engineer" who designed and spec'ed your system didn't know what they were doing (or it's not working right). Modern heat pumps must be selected for the climate they operate in. If your electricity is $0.12/kWh and you draw 12 kW for 10 hours, that's $14.40 (or $432/month just for nighttime heating).

    I don't think you're going to get a useful answer on that one. It varies and is locally upgraded and added to as demand increases. The advent of LED lighting and the abandonment of wasteful tungsten lighting, coupled with replacement of old energy hogging appliances, etc. is still dropping demand in most areas. EV's will take up the slack.

    In general, it won't stress the grid, it will improve profitability. Which means if the utility regulators are performing the function they were designed for, this will bring down the cost of residential electricity going forward. That's assuming that monied interests have not decapitated the ability of regulators to effectively regulate monopolies by claiming it's now a "free market".

    The typical driver of 32 miles/day will only need to charge for 1 1/2 hour/night at 26kW. A significant portion of that electrical demand will be offset by reduced refining. People forget it takes a lot of electricity to refine oil to gasoline.

    Electrical grid experts who have studied this don't see a problem.

    You have some serious misconceptions and assumptions. The growing fleet of EV's will increase the profitability of electricity providers. Any increase in infrastructure spending will be easily covered by the more profitable metrics and higher volume of sales. Money that was once flowing to oil interests will shift to electrical interests.
     
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  8. gnuarm

    gnuarm Model X 100 with 72 kW chargers

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    That is ridiculous. I suspect the "night" and "day" are actually most of the 24 hour cycle and a few hours respectively, not the entire day. I am on a TOU similar to that where my "night" rate is about half standard and my "peak" rate is five times the standard rate. I think the numbers are so extreme because that is similar to what the utility pays for the marginal peak rates, or even higher! Consider that to supply power during the four hour peak time requires running gas turbines just 4 hours a day and then only five days a week!

    But when you do the math if you shift your highest usage from the peak times, you should come out ahead or at least even.

    To give you an idea of what some utilities do, mine actually started sending emails in the summer asking people to simply cut back on electric usage during a five hour peak time. No compensation, just because we are nice people. I made it into an experiment and programmed my thermostat to cut off the AC during that peak time. The temperature didn't rise so much, I think a max of 4 degrees F, often less. So once I ordered the Tesla I switched to TOU which allows my altruism to pay a few pennies back.
     
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  9. gnuarm

    gnuarm Model X 100 with 72 kW chargers

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    I didn't see an area under the not car specific areas for this. Given the model 3 is the biggest seller, I figured this is the group that would be most interested in long term impacts of EV ownership.
     
  10. electricar

    electricar Member

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    The existing grid definitely can not support a 100% of all cars being BEV and burning fossil fuels to make electricity is self-defeating from a climate change perspective. An extensive upgrade to the grid and acceptance of electricity generated by nuclear energy will be required and I, for one, have seen no evidence of either of these things happening.
     
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  11. M3BlueGeorgia

    M3BlueGeorgia Member

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    I really don't see a problem here. I think you are overthinking this or regurgitating FUD.

    In Georgia, the peak load is summer, noon through early evening, and the grid has to be capable of handling that. And it does, because we don't get brown-outs or black-outs during peak summer usage.

    Electric vehicles mostly charge at night, when load on the grid is light and the electricity is mostly from baseline sources with little carbon impact.

    For example my EMC charges 5c/kWh between midnight and 6am, and throws in 400 kWh free each month.

    So, again, what problem are you trying to solve? I don't see a problem that the revolution of A/C cooling didn't already force the electric utilities to solve. In fact by introducing some overnight electric usage, we might be helping them.
     
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  12. gnuarm

    gnuarm Model X 100 with 72 kW chargers

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    Ok, thanks for the advice. I'll apply that info when I find a suitable use.


    Maybe, maybe not. It largely depends on reaching the right person.


    I don't think you gave enough thought to what I wrote. Charging at night is great for utilizing the excess generation and transmission capacity. However, the distribution for residential areas is not built to handle the potential heavy loads of a significant number of EV charging at the same time. When we do a lot of things at the same time, like cook dinner, we get peaks in demand and the distribution has to be built for that. But evening cooking is potentially a fraction of charging an EV. So the stress will be there at any time significant numbers of EVs are charging. Also consider that many EV owners will start their charging when they get home to make sure it happens or if on TOU they will program it for the end of the peak hours. The point is many will be charging at the same time.


    Reduction of refining is not relevant in the context of residential distribution, that is a generation and transmission issue and perhaps a commercial distribution issue.

    What you are ignoring is that the EV usage is on top of all other usage. I have seen my own usage exceed 12 kW on the coldest nights last year (without an EV). I get that you actually don't understand heat pump operation, but regardless of the system design, when the temperatures fall below 25 °F they switch to straight electric heat. They ALL do this at whatever temperature they are set for which is not a lot different from the temperature mine is set for. If you size a heat pump to handle the few coldest nights without backup heat you are paying for capacity that will only be used a few days a year and wasting money. Adding another X kW for EV charging on top of the existing max usage will require adding distribution capacity if that added load can't be shifted so the many EVs aren't charging at the same time. The fact that EVs don't need to charge all night is what makes it possible to coordinate their charging so as to not require expansion of distribution. But that will require some means of coordination which is what needs to be promoted since the utilities won't be pushing for that.

    The exact numbers of the distribution design may not be right, but the principles are correct. Just as the heat pump is designed to use backup heat for the few coldest nights the distribution grid is not designed with lots of excess capacity. It would be overly expensive. I am confident in what I am saying. Try to understand rather than just resisting.


    I would love to see the papers on this. Where did you read this? Don't confuse generation and transmission vs. distribution. I agree that if we encourage EV charging at off peak times we can actually lower the average cost of electricity. But that is not adequate to assure we don't need to increase distribution capacity.


    You seem to over simplify the details without actually understanding how distribution works. The shifting of automotive power sources is not the issue I am addressing. Now you seem to be saying that EV charging will require spending money on distribution, but that it will be paid for with somehow free money. That's like my local utility increasing their charge for distribution and justifying by saying our bills won't go up so much on average because the cost of generation (not by them, third party) is going down. LOL This is the sort of slight of hand I'd like to get ahead of rather than letting the utility handle things on their own.
     
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  13. gnuarm

    gnuarm Model X 100 with 72 kW chargers

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    You can claim that, but what am I regurgitating exactly??? I believe you are very much *underthinking* the issue. In fact, you don't even seem to understand what the issue is as you show below.


    The issue I am discussing has nothing to do with peak generating load. Fix that firmly in your mind. What you are talking about is the overlap of residential and commercial usage creating the summer late afternoon/early evening peak. Because the residential distribution grid is designed for larger loads this time is not a problem for distribution.


    Yes, perfect! Now you are showing you understand perfectly the wrong problem.


    I don't know what EMC is, so I can't respond to that part. Power cost has nothing to do with this conversation. If you don't understand what I wrote please reread it paying careful attention to the use of the term "distribution". I guess I should have put that in the subject line.
     
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  14. gnuarm

    gnuarm Model X 100 with 72 kW chargers

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    This discussion is not about electricity generation. This is about local distribution. I think you are wrong about not being able to power all cars as BEVs. The numbers are not a problem for generation as long as a large percentage is done off peak times. That part is simple. What is more complicated is the impact of home charging on the residential distribution grid.
     
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  15. mspohr

    mspohr Well-Known Member

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    This has been studied repeatedly and extensively by actual experts and the existing grid can easily handle growing numbers of EVs. (It will take at least 25 years to reach 100% even in the best case scenarios.)
    I see you've dragged out the old canard of EVs charging from fossil fuels. Well, that too has been studied to death and there are two problems with it. The US as a whole only gets 30% of its electricity from fossil fuels and that is dropping rapidly as more renewables come on line. Also, even if an EV is fueled 100% from fossil fuel, it is still less carbon intensive than an ICE vehicle since power plants are much more efficient than ICE engines.
    Nuclear is not necessary. Again, actual experts have studied this issue extensively and it's possible to have an electric grid powered fully by renewables and batteries. Nuclear is just too expensive to have any meaningful role in future energy.
     
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  16. Big Dog

    Big Dog Member

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    Absolutely nothing. The grid is maxed out in summer for a/c. Look up any electric company's max generation/load and it will be the hottest day of the year. Think about it: electric companies build the grid for peak load to avoid blackouts.

    Charging at night, when most of the world is sleeping, is a HUGE benefit to the utility as it helps them average costs.

    btw: most homes in California use gas heat, and formerly oil-burning towns are starting to convert. Heat pumps aren't that efficient in the northeast or west.
     
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  17. nwdiver

    nwdiver Well-Known Member

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    On the contrary. EVs are essentially dispatchable demand, the perfect match for non-dispatchable and super cheap renewables. Of which we are adding a lot of. Also completely destroys the argument for absurdly expensive thermal 'base-load' like nuclear.

    [​IMG]
     
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  18. StealthP3D

    StealthP3D Active Member

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    Exactly! The utility has invested in transmission lines and transformers to handle peak loads. Building and maintaining this infrastructure, especially through storms, is expensive and it's a fixed cost, ie, it doesn't rise when you start charging EV's at night. So their investment in the infrastructure can be costed over more kWh's of sales. When we got 2 EV's last year our electrical bill went up by about 30%. The electric company is making more profit now because we send them more money and yet their infrastructure costs haven't risen (we charge at night when demand is lowest). We pay about $0.10/kWh but it only costs about $0.02-$0.05/kWh to purchase in the wholesale markets or produce it themselves.

    In many areas at many times of the day/year there is excess wind energy that cannot be used - the operators of the wind generators simply turn them off - even though the wind is blowing. EV's will help electrical producers cost their equipment over more kWh/year and keep it running more constantly. All of this will lower the cost of electricity and/or increase profits for the providers.

    If there was a locale where the proliferation of EV's started to stress the grid, electric providers would simply introduce Time of Use pricing which has the wonderful effect of causing people to use more when there is a surplus and less when the commodity is tight. And EV's are ideal for soaking up excess demand because they can charge whenever the are parked at home (assuming they have a EVSE at home (and the majority of EV drivers do). As EV's proliferate, EV chargers will spring up everywhere there is parking (this is already happening in the most progressive areas of the country) which will add further flexibility as to when you charge your EV.
     
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  19. Daniel in SD

    Daniel in SD Active Member

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    Heat pumps are super efficient here (I've got one). The lowest temperatures we ever see are in the 40s. But yeah in CA peak residential load is 4-9pm with all the AC running. I bet there is enough grid capacity for everyone to have an EV.
     
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  20. nwdiver

    nwdiver Well-Known Member

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    There's no question. There absolutely is.
     
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