Just a thought, obviously solar, battery storage and heat pumps have been talked about but should we have 3 phase? My reasoning Ali's that if EVs were made to charge at 22kW that would reduce home charging times significantly, easing the use of public network rapids. It would also mean that if the grid needed to be balanced the EVs (and battery storage) could pull more to help. Would also mean that we could supply more power to the grid when needed once we have V2G. Surely the added cost of installing this at the point of construction would be minimal?
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Should new builds come with 3 phase?
- Thread starter m3gt2
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Glan gluaisne
Active Member
It's not a bad idea, but the cost of putting 3 phase in would be pretty high for many developments, both because the capacity isn't available in the local LV grid and because the split out from 3 phase to single phase can be some distance from some houses. The cost of upgrading both the local substations, some of which would need to be changed from pole mounted transformers to ground mounted ones to accommodate the increased size and weight, and the 11kW HV network that supplies them, wouldn't be cheap.
The other point is that few cars can actually charge at 22 kW, either. Not sure about other Tesla models, but the Model 3 can only charge at 16 A per phase, so a nominal 11 kW maximum on three phase (the Model 3 uses two of its chargers in parallel to allow single phase charging at 32 A).
The other point is that few cars can actually charge at 22 kW, either. Not sure about other Tesla models, but the Model 3 can only charge at 16 A per phase, so a nominal 11 kW maximum on three phase (the Model 3 uses two of its chargers in parallel to allow single phase charging at 32 A).
Good points that I hadn't realised. Some older Tesla's charged at 22kW and I think new S and X are 16kW but going forward building new EVs with that ability could happen. Much more to it than you think!
MrBadger
Badger out
I personally don't think 3 phase should be installed as a matter of course.
We need should not be installing anything that encourages excessive use of energy. Granted that EV's and wider use of heat pumps and other electrical heating will put increased demand in some scenarios, but there are ways that these can be utilised to allow existing typical restrictions to cope. 100A single phase is more than enough for most typical domestic abodes if used thoughtfully and efficiently. And it wouldn't cost so much in need to upgrade infrastructure.
We need should not be installing anything that encourages excessive use of energy. Granted that EV's and wider use of heat pumps and other electrical heating will put increased demand in some scenarios, but there are ways that these can be utilised to allow existing typical restrictions to cope. 100A single phase is more than enough for most typical domestic abodes if used thoughtfully and efficiently. And it wouldn't cost so much in need to upgrade infrastructure.
webbah
Active Member
All of Switzerland is 3 phase. Not sure I understand but are you saying that UK spec Model 3's are single phase? I'd find that hard to believe. I think all EU spec Tesla onboard chargers are 3 phase. At any rate, yes max you can get is 11Kw 16A on a 3 phase AC charger.
Sorry, not the car. Most houses in UK are single phase, I was thinking if they had 3 phase it would ease some demand on rapid chargers.
Glan gluaisne
Active Member
One problem is that our local electricity supply grid is sized and rated for a typical household load, although it varies a bit with the age of the local infrastructure. It was common to find the per house demand estimate being as low as 8 kW around 50 or 60 years ago, for example, and although I believe that the current standard for demand planning is a per household demand of ~15kW, in practice there is diversity applied to the LV grid, so the DNO never expect that all houses on any particular phase will draw ~15 kW at the same time.
It's worth noting that the fuse in the company head is usually rated at 60 A, 80 A or 100 A (ignore the fuse holder rating printed on the case, that pretty much always reads 100 A). The fuse is very much a last ditch protection measure for the cabling, not the rating of the supply. having the highest available single phase fuse fitted of 100 A doesn't mean you can draw 100 A from the supply all the time, it just means that the cables are rated such that they will be protected if 100 A is drawn from the supply for short periods. Our supply (put in 7 years ago) is has an 80 A fuse, for example, which isn't untypical. We could have this uprated to 100 A, as the cables are sized for that, but in reality 80 A is more than enough.
In general, household demand has dropped a lot over the past ten years or so, due largely to changes in the stuff we use. Appliances now tend to use far less power than they used to, with everything from washing machines to TVs having been made a lot more efficient. It's also worth looking at how much energy we really need to run an EV. Someone doing a long commute each day (as I used to) of about 50 miles each way, would need to put around 30 kWh back into their car every night, assuming a fairly generous 300 Wh/mile. Assuming they had at least 8 hours charge time overnight would mean that charging at just 3.75 kW would be fine, around half the maximum charge rate we can get from a typical 32 A charge point.
Alternatively, we could look across the whole country, and try and estimate the impact of most cars being EVs. The average mileage driven in the UK is about 10,000 miles a year. If we assume that this is only on weekdays (makes for a worst case example) then that is about 38 miles per day, or about 11.5 kWh. That's barely enough to justify having a 7 kW charge point, really. The effect of drawing another 11.5 kWh per day per household in the UK isn't that great, especially given that domestic electricity demand has dropped a lot.
There are currently about 31 million electricity consumers registered in the UK, up from about 27 million consumers in 2000. Despite that increase, demand per consumer has reduced a fair bit, from ~12.2 MWh/consumer/year in 2000 to 9.52 MWh/consumer/year in 2019, a reduction of around 22% per consumer.
The ~2.68 MWh per consumer that has been saved, due largely to changes in the energy efficiency of appliances, I suspect, is equivalent to about 8,900 miles of EV motoring per consumer, at a fairly generous 300 Wh/mile. I suspect that, in reality, this energy saving alone may well be close to enough to cover the real energy cost of running one EV per consumer, given that many EVs seem to be able to get better than 250 Wh/mile.
Generation capacity is also increasing, as more and more renewable generation sources come on line, and the grid has got much the same diurnal balancing problem that it has had for decades, in that day time peak consumption is massively higher than the night time trough. Decades ago we came up with the idea of night storage heaters and various off peak tariffs to try and redress this balance problem, but now it looks very much as if charging EVs overnight might help with a part of it. Charging an EV overnight, every night, isn't as big a demand on the grid as charging storage heaters used to be (they would typically charge at >10 kW per household for 7 hours every winter night) but it will help.
Hope the above has helped put the energy supply situation into some sort of perspective, as I often hear arguments from the anti-EV brigade that all this "extra" electricity has to come from somewhere, so will need loads more power stations. The reality is that the true impact will be pretty small, as EVs just don't make that much difference, really.
It's worth noting that the fuse in the company head is usually rated at 60 A, 80 A or 100 A (ignore the fuse holder rating printed on the case, that pretty much always reads 100 A). The fuse is very much a last ditch protection measure for the cabling, not the rating of the supply. having the highest available single phase fuse fitted of 100 A doesn't mean you can draw 100 A from the supply all the time, it just means that the cables are rated such that they will be protected if 100 A is drawn from the supply for short periods. Our supply (put in 7 years ago) is has an 80 A fuse, for example, which isn't untypical. We could have this uprated to 100 A, as the cables are sized for that, but in reality 80 A is more than enough.
In general, household demand has dropped a lot over the past ten years or so, due largely to changes in the stuff we use. Appliances now tend to use far less power than they used to, with everything from washing machines to TVs having been made a lot more efficient. It's also worth looking at how much energy we really need to run an EV. Someone doing a long commute each day (as I used to) of about 50 miles each way, would need to put around 30 kWh back into their car every night, assuming a fairly generous 300 Wh/mile. Assuming they had at least 8 hours charge time overnight would mean that charging at just 3.75 kW would be fine, around half the maximum charge rate we can get from a typical 32 A charge point.
Alternatively, we could look across the whole country, and try and estimate the impact of most cars being EVs. The average mileage driven in the UK is about 10,000 miles a year. If we assume that this is only on weekdays (makes for a worst case example) then that is about 38 miles per day, or about 11.5 kWh. That's barely enough to justify having a 7 kW charge point, really. The effect of drawing another 11.5 kWh per day per household in the UK isn't that great, especially given that domestic electricity demand has dropped a lot.
There are currently about 31 million electricity consumers registered in the UK, up from about 27 million consumers in 2000. Despite that increase, demand per consumer has reduced a fair bit, from ~12.2 MWh/consumer/year in 2000 to 9.52 MWh/consumer/year in 2019, a reduction of around 22% per consumer.
The ~2.68 MWh per consumer that has been saved, due largely to changes in the energy efficiency of appliances, I suspect, is equivalent to about 8,900 miles of EV motoring per consumer, at a fairly generous 300 Wh/mile. I suspect that, in reality, this energy saving alone may well be close to enough to cover the real energy cost of running one EV per consumer, given that many EVs seem to be able to get better than 250 Wh/mile.
Generation capacity is also increasing, as more and more renewable generation sources come on line, and the grid has got much the same diurnal balancing problem that it has had for decades, in that day time peak consumption is massively higher than the night time trough. Decades ago we came up with the idea of night storage heaters and various off peak tariffs to try and redress this balance problem, but now it looks very much as if charging EVs overnight might help with a part of it. Charging an EV overnight, every night, isn't as big a demand on the grid as charging storage heaters used to be (they would typically charge at >10 kW per household for 7 hours every winter night) but it will help.
Hope the above has helped put the energy supply situation into some sort of perspective, as I often hear arguments from the anti-EV brigade that all this "extra" electricity has to come from somewhere, so will need loads more power stations. The reality is that the true impact will be pretty small, as EVs just don't make that much difference, really.
I'm not sure that there's an existing issue with people not having time to complete home charging even on 7kW ... open for comments! I also would have thought that most rapid charging use would be away from home on a trip somewhere so there wouldn't really be a strong connection between the two issues.
Glan gluaisne
Active Member
Rare to get a 3 phase domestic supply here. We have a radically different approach to domestic wiring from most of Europe, so don't have the 3 phase, radial circuit, consumer units common in Europe, we have single phase consumer units, almost always with many of the outlets supplied by ring final circuits, rather than radials.
FWIW, I like the European system of using radial circuits and lots of MCBs in the distribution board, but there's no indication that normal practice here will change to such a system any time soon.
I am aware that the generating capacity can cope with the transfer to EV ownership but would be interested in your comments with regard to the impact locally. At the moment a given sub-station that supplies a group of houses may only have one or two EVs wanting to charge on the same evening. What happens when every household has an EV and wants to charge on the same evening? Is the present locally based infrastructure likely to struggle?
Glan gluaisne
Active Member
Just been looking at some numbers, to try and see what impact EVs are having on the grid at the moment, in terms of increased electricity demand. Hard to pin down exact numbers, but it looks as if EVs are accounting for a total of about 0.09% of the total annual electricity consumption in the UK. Not really very significant, given that electricity consumption has been dropping by about 2% per year over the past couple of decades.
Glan gluaisne
Active Member
I suspect that the diurnal demand characteristics we have at the moment will probably cover much of the apparent additional load. As long as EVs aren't charging at the same time that everyone is cooking a meal, or running electric heating, then I doubt there will be a problem. There's often a lot of spare capacity in the local grid, and the national grid, overnight, probably enough to deal with the additional demand of EV charging, especially if most people charge overnight.
I pretty much always charge overnight, unless it's sunny enough to make it worth charging when the solar panels are generating a lot. I just have a simple time switch in my charge points, set to turn on and off at the start and end of the off peak period. Something as simple as that would probably manage the additional load on the grid well enough, although with smart meters and smart charge points there is the option (albeit with more user intervention needed) to do the same. Given that the off peak period has always been roughly at the same time overnight, I've never been convinced that we need the added complexity of smart meters, smart charge points and a plethora of different apps, running on a multitude of devices, to try and coherently balance demand.
It might sound a bit Luddite, but sometimes simple and foolproof solutions, like a time switch, can be the most reliable overall. I've not touched the time switches in my charge points for at least a couple of years, they stay set on GMT (as the E7 off-peak period timing is fixed to GMT) and the charge points just reliably turn on and off without any intervention.
*Adam
Member
Just to put some perspective into generation numbers by using some 'fag packet' analysis. There are some huge assumptions in my numbers but heyho.
If 10% of the current 31.7m passenger vehicle were EVs and inconveniently needed to charge at the same time drawing 7.2kWh per vehicle. We would need 7 Hinckley Point C nuclear reactors worth of capacity.
Puts 2035 fossil fuel ban into prespective.
(3.17m cars * 0.0072 MWh) / 3260MWh generating capacity of Hinckley Point c
If 10% of the current 31.7m passenger vehicle were EVs and inconveniently needed to charge at the same time drawing 7.2kWh per vehicle. We would need 7 Hinckley Point C nuclear reactors worth of capacity.
Puts 2035 fossil fuel ban into prespective.
(3.17m cars * 0.0072 MWh) / 3260MWh generating capacity of Hinckley Point c
Glan gluaisne
Active Member
And, right now (as I am typing this) there is 15.44GW of electricity being generated by renewable energy generators in the UK, with a total UK electricity demand of 26.489 GW, so about 58% of all UK electricity is coming from renewable sources at the moment.
That 15.44 GW of renewable generation (mainly wind and solar) would be enough to charge 2.144 million EVs at 7.2 kW. Realistically, there will be a great deal of diversity (in the load management sense) when it comes to EV charging. Not everyone will charge at the same rate at the same instant. It's a bit like electric cookers. Most houses with electric cookers and hobs will have a maximum load from them of around 5 kW to 9 kW (just checked ours and it's 8 kW total). However, diversity provisions are applied to cooker circuits, because no one is every likely to have their cooker and hob on at the maximum rated load. For a cooker, the diversity rule applied is 10 A plus 30% of the maximum rated current, so for our 8 kW nominal cookers and hob, with a rated load of about 35 A, after allowing for diversity the load used for demand purposes is reduced to 21 A, or 4.8 kW.
Back when economy 7 and storage heaters were popular, there was a policy of making sure that the time clocks that switched them on were all set to slightly different times, as this prevented millions of >10 kW loads all switching on at the same instant, causing potential problems for the grid. Some of this variation was accidental, in that the electrically driven mechanical clock time switches were inherently a bit inaccurate, some was deliberate, by the use of command switching at slightly different times. I suspect that smart meters and smart charge points will have to simulate this inherent variation in some way, to avoid the same potential issue.
As the energy requirement for EVs isn't massive, on a day to day basis, the roll out of distributed battery storage should deal with it. Quite a few wind and solar generating plants are now being built with battery storage that will enable this flattening of demand peaks, and battery storage seems to be being rolled out to existing solar and wind plants now, so by the time we have a large EV fleet in the UK we should have enough short term storage to meet the demand peak from overnight charging, especially as an average overnight charge won't be for a long time. A car driven 10,000 miles a year, and only charged on weekday nights, would only need around an hour and a half of charging per weekday night, so not a lot in the overall scheme of things.
But fortunately the grid has way more than 5 Hinkley point's worth of capacity available ...
6 myths about electric vehicles busted | National Grid Group
Jason71
Well-Known Member
I spoke to someone from my DNO last week. He said a lot of new build estates are now cabled up by third party companies and the DNO just connects them up at the entrance to the estate. He implied they use the minimum spec cables they can get away with which will not support future full electrification of all cars. 
*Adam
Member
I believe In order to transition to majority EV ownership there needs to be a sizable change in generation and balancing to smooth out those demand peaks and add additional capacity. Thats without and regional DNO changes.
You might say the grid in its current state does not deal well with the level of variation as it is; solar and wind is a difficult beast to control. We've seen some pricing, balancing, and blackout events to support that. Add into the mix the current ramp rate of EV ownership and you have a very volatile grid where balancing mechanisms will need to be implemented. Admittedly not overnight....
N.b. One thing not to neglect (as I did) is gross demand over net demand. Line Loss Factors and Transmission Loss Multipliers can be sizable in certain regions.
You might say the grid in its current state does not deal well with the level of variation as it is; solar and wind is a difficult beast to control. We've seen some pricing, balancing, and blackout events to support that. Add into the mix the current ramp rate of EV ownership and you have a very volatile grid where balancing mechanisms will need to be implemented. Admittedly not overnight....
N.b. One thing not to neglect (as I did) is gross demand over net demand. Line Loss Factors and Transmission Loss Multipliers can be sizable in certain regions.
I would like 3 phase, as it allows an instant water heater to surport a full flowrate, shower in winter and full a bath at a good rate. This then removes the need for gas in properties that are not large enough to have space for a hot water tank.
In larger properties a thermal store can be used that is heated with a heat pump as times of cheap power, with the instant water heater being the backup for when the thermal store can't provide enough hot water.
In larger properties a thermal store can be used that is heated with a heat pump as times of cheap power, with the instant water heater being the backup for when the thermal store can't provide enough hot water.
Glan gluaisne
Active Member
I spoke to someone from my DNO last week. He said a lot of new build estates are now cabled up by third party companies and the DNO just connects them up at the entrance to the estate. He implied they use the minimum spec cables they can get away with which will not support future full electrification of all cars.
I've heard this too, and seen some of the pretty shoddy work left behind. Some of the changes to regulations in the past few years have been to compensate for the de-skilling of electrical installation work, IMHO, as well as a general reduction in the quality of some electrical equipment.
We have a phase change thermal store. Very small for its capacity, just 870mm tall, 370mm deep and 580mm wide, that stores ~9.5 kWh to 10 kWh of heat for hot water, roughly the same as a 200 litre hot water cylinder. It's heated by a 3 kW electric heating element, with much of the electricity (~60% or so) coming from excess solar generation. Seems to work very well, and a couple of these could be fitted in the space at the bottom of a typical airing cupboard, giving masses of hot water. The losses are also very low, as the insulation uses vacuum panels, so the phase change storage medium (a form or sodium acetate) stays hot for a long time.
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