Are we on the brink of an electric car revolution?

PS_RalphW · Post by **PS_RalphW** » 29 Feb 2016, 15:49

Been thinking about electric car numbers.

If a typical car drives 10,000 miles a year, that is about 30 miles a day.
If it does 4M/KWh that is 7.5KWh.

UK electricity demand falls by about 10GW overnight, between 11 pm and
7 am. If the car was charged evenly over that period, it would use about 1KW. That would mean that the existing electricity generating capacity could support 10 million electric cars (about 1/3 of the fleet?) without exceeding the normal daytime demand at all, let alone impacting the evening peak demand.

Of course that is a bit simplistic, as some cars would be charged during daytime and evening peak, but it shows that there is room for a lot of electric cars in the existing infrastructure.

It would be trivial to spread out the overnight demand by simply charging the car with a random delay before the charging period began, whilst still starting soon enough to complete charge by morning. This is a simple software change to the existing hardware.

fuzzy · Post by **fuzzy** » 29 Feb 2016, 17:54

Are you saying an electric car does 4 miles on 1kWhr? As in 1kWhr from the mains through a charger? Sounds low, but I have no idea.

PS_RalphW · Post by **PS_RalphW** » 29 Feb 2016, 21:47

Yep.

Remember a gallon of petrol has about 45 KWh so in energy terms it is about
180 mpg.

cubes · Post by **cubes** » 29 Feb 2016, 23:10

How inefficient is the charging process though?

Also, is the dip in demand used to do light/routine maintenance (of the sort that can be done in a few hours) of power stations while they're not likely to be needed?

PS_RalphW · Post by **PS_RalphW** » 01 Mar 2016, 03:41

Efficiency of charging and of the electric motors are quite high. The motor is of the order of 90%. I'm not sure about the battery, but if it wasn't high, you couldn't fast charge it - it would melt from the waste heat.

The total energy efficiency from fossil fuel at the power station to wheel depends on the efficiency of the power generation and transmission, but is in almost all cases better than the best diesel engines. This is partly down to the design of the car - aerodynamic drag etc. has been reduced to maximise the range. This could be done in all cars, but isn't.

Pepperman · Post by **Pepperman** » 03 Mar 2016, 12:40

Yeah 250Wh/mile or 160Wh/km is about the right ballpark figure to use. This is what the Model S gets so I imagine a carefully driven Leaf should do better than that. I usually assume about 85% charge efficiency.

As you rightly point out we have a lot of off peak generation capacity so assuming that people can be nudged towards the off peak period then I don't expect there to be major impacts that can't be managed in the short term and in the medium term I expect EVs to actively contribute to grid stability.

In reality I would expect your charge cycle max out at nearer to 3kW on a 16A charger and 6kW on a 32A charger.

With vehicle ranges heading in the direction that they are now, in reality most people wouldn't need to bother plugging in every night as they'll have more than enough range for their needs recharging two or three times a week.

And yes you can set the Leaf to start charging at midnight. You can even set it up to pre-warm the cabin so that it warms up just before you leave home and you don't need to use as much heater while driving.

What we should really be doing is ensuring that all EVs are sold with V2G-compatible software that allows grid controllers / demand aggregators to be able to modulate / stagger charge cycles in a way that balances the grid. I have no idea whether this is already included in EV software but it really should be. That way you could set your charge time to be at the cheapest rate for that evening or at the lowest CO2 intensity if you prefer.

PS_RalphW · Post by **PS_RalphW** » 04 Mar 2016, 09:28

Collected my new toy yesterday

Still drowning in paper work -
failed to register with the Nissan web site
Failed to order a charging port
Failed to clarify need for listed building consent
Failed to register car with ecotricity

The car goes... (once I worked out the order of buttons to press

)

emordnilap · Post by **emordnilap** » 04 Mar 2016, 10:11

PS_RalphW wrote:Collected my new toy yesterday

Still drowning in paper work -
failed to register with the Nissan web site
Failed to order a charging port
Failed to clarify need for listed building consent
Failed to register car with ecotricity

The car goes... (once I worked out the order of buttons to press )

Sounds like you're having fun...

biffvernon · Post by **biffvernon** » 04 Mar 2016, 10:57

You need listed building consent for a car?

PS_RalphW · Post by **PS_RalphW** » 04 Mar 2016, 11:54

I would if I tried attach a charging port to the outside wall. That is why it will
be on a fence post.

I might to drill the cable hole through the wall, if the cable is too fat...

Pepperman · Post by **Pepperman** » 04 Mar 2016, 16:18

Even a 32A cable won't be much more than a couple of cm across so you should be ok.

Would be good if you can post up your experience and data on energy consumption.

Post by **adam2** » 04 Mar 2016, 17:06

A modern switched mode battery charger is about 95% efficient, so 1KW into the charger is about 950WH into the battery.

The batteries in electric vehicles are about 90% efficient, so 1KWH into the battery is about 900WH on discharge.

No great accuracy is claimed in these figures since not only do different models vary a bit, but the efficiency figures vary a bit depending on age, temperature, duty cycle and other factors.

The grid has at least 10GW of spare capacity overnight, which would permit of charging huge numbers of EVs without any new generating capacity.
It should however be noted that the marginal fuel for power generation is natural gas and that any extra load is met by increasing gas burning.

If say 1GW of extra EV charging is to be added to the grid, then it would be preferable to add enough renewable generation so as to avoid any increase in gas burnt.

Some local infrastructure upgrades might be needed if EVs become popular.
At present the electricity companies only allow about 1KW per dwelling when sizing infrastructure.
This astonishingly low figure works surprisingly well as an average over a large area. Any individual dwelling can use up to typically 24KW, but 1,000KW of substation capacity is usually sufficient for 1,000 homes. (provided that natural gas is available. In areas without a gas supply 2KW per dwelling is assumed due to the increased likelihood of electric heating.)

If more than about 10% of the homes on one substation use an EV then an upgrade may be needed.

Pepperman · Post by **Pepperman** » 04 Mar 2016, 17:57

adam2 wrote:If more than about 10% of the homes on one substation use an EV then an upgrade may be needed.

In some cases, yes, but in general it's not that bad:

The results, which come at a time when sales of plug-in cars have increased by 716% over the past two years, show that across Britain 32% of low voltage (LV) feeders (312,000 circuits) will require intervention when 40% - 70% of customers have EVs, based on 3.5 kW (16 amp) charging. Susceptible networks are typically characterised by available capacity of less than 1.5 kW per customer.

Traditionally, these findings would mean the replacement of underground cables in the public highway, however My Electric Avenue has been trialling a lower cost solution to this in the form of ‘Esprit’. Esprit is an innovative piece of technology that can control the charging of EVs if the local electricity grid reaches a certain level of demand. By incorporating Esprit into networks, the project is the first real-life trial that has directly controlled domestic EV charging to prevent underground cables, overhead lines and substations being potentially overloaded.

http://myelectricavenue.info/

PS_RalphW · Post by **PS_RalphW** » 04 Mar 2016, 21:35

Just joined the ecotricity charging network. This gives access to 300 fast chargers at motorway services absolutely free- I don't even need to be an ecotricity customer

I have also discovered a fast charger 100M from our local supermarket. This charges 9p KWh and you need to join a national network for £20 year.

Some charging networks are almost free, others charge an arm and a leg.

There is no rhyme or reason the the national distribution of chargers, types of chargers, payment schemes, access methods, anything. It is amazing that it works at all.

I would join the Charge East network - but their website has crashed

Post by **kenneal - lagger** » 05 Mar 2016, 06:05

An environmental group to which I belong is organising another Electric Vehicle show this year in Newbury. we did one last year which was quite successful although we found it difficult to get the smaller cars to the event. This year we have managed to get some of the smaller cars and I was trying to get a bicycle seller to bring some along as well. One of the distributors that I spoke to said that he had given up stocking them as the reliability was abysmal. Can anyone comment on this from experience?