Electric vehicles miles per KWh

1961Nick

GreatApe wrote: »

Do you think the £3,000 a year less in tax you pay should be made up by firing 1/10th of a teacher or the government taking on £3,000 more debt plus interest for your kids to deal with when the 20 year gilt comes due?

If the teachers drive EVs we won't need to pay them as much.

Haven't government bond yields gone negative? The kids are getting wealthier!:cool:

almillar

A model 3 might get 4.1 miles per KWh according to their regulator and customer feedback
But the car is always using energy while driving or not and there are significant charging losses

You're using a Tesla as an example, which as far as I'm aware has the biggest phantom draw of all EVs (because it does most). Power used whilst car is not on = phantom draw. On an ICE, you're slowly draining the battery keeping the alarm and other systems going. Same on an EV (most still have a 12v battery, which will be charged by the traction (proper, big) battery, when the car is on. No alternator required.

So EVs do have phantom draw, and many have cellular/WiFi connectivity - this is how you can pre-heat the cabin etc.

Teslas, being particularly high spec, can apparantly have quite a high draw. Sentry mode is a CCTV for your car, for example! But compared to the amount of power used to propel a vehicle, and compared to ICE cars, EVs are still very efficient. Certainly this 'standby' power usage needs to be as low as possible - both my EVs request 12v battery changes after 3 years, and the Zoe only just made it to 3 years!

Charging efficiency. Rapid charging is very efficient, slower AC charging may not be as efficient, because of the length of time these small losses last. Still nothing to lose sleep over, IMO, and unless you want to re-invent AC-DC transformers, you're going to have to live with ~90% efficiency!

FWIW, I've done 10k miles in my Kia Soul and the car says 3.8m/kWh, whilst my spreadsheet says 3.9.

Total average m/kWh in the Zoe was 3.51.

Have a look at the shape of those two cars - which one looks more aerodynamic?!! Kia/Hyundai have some efficient motors.

I have an urban commute, and I drive economically when I'm stuck in traffic, but otherwise I'm quite fast. I choose to drive at 60 instead of 70 sometimes in the EVs, which I don't recall doing in an ICE!

Petrol and diesel only cost about 45p per litre in the UK the rest is taxes

This is, of course, true, but unless you can buy it tax-free, you're stuck in the same government manufactured reality as the rest of us.

Yes you can use a 5p night rate but that will last only until about 5-10% of the car stock are BEVs then there won't be a night time rate

I doubt that. Night rate exists to balance supply/demand over 24 hours. Are you saying they'll tip that balance, and obliterate the benefit to the grid?!

GreatApe

Martyn1981 wrote: »

Then you need to do the same for petrol and diesel and include the efficiency losses from source to fuel tank (battery).

1 gallon of diesel in a power station to charge a Tesla Vs using the diesel directly and assuming the average 7,100 miles

A modern diesel might get 65mpg

A gallon of diesel in a CCGT @55% through a grid with 8% loss then charging a Tesla at 85% and the Tesla getting an average 2.8 miles per kWh including dead time and self discharge works out to 59 mpg

Any of the processes to make the diesel are the same


So it seems even though an electric motor is very efficient
Power station losses
Grid losses
Charging losses
Standing losses
All add up to make an EV on typical usage no more primary energy efficient

Using diesel is just for comparison purposes to keep it simple for lay persons
You could put the equivalent thermal energy of natural gas in the power station
Of course if you have a green grid this is fine but most grids are still marginal coal or NG

So a TM3 is worse than an efficient diesel in grids that are marginal coal (Poland & Germany for instance,)
And roughly equal in grids that are marginal NG (UK today) or oil (Japan?/Saudi)
And much better in marginal nuclear or hydro (France & Norway)

GreatApe

almillar wrote: »

I doubt that. Night rate exists to balance supply/demand over 24 hours. Are you saying they'll tip that balance, and obliterate the benefit to the grid?!

More or less

There is only so much demand you can add to the nights before the nights power useage is no longer low cheap rate

You might be able to add 25 GWh to the night 5 hours
That's about 3.6 million EVs worth
Or about 10% of the stock of cars in the UK

Also with the no natural gas in new builds by 2025 fuel you may find many of those homes are fitted with tanks which will all try to draw on a cheaper night time again more competition for night time demand will erode the price advantage

1961Nick

GreatApe wrote: »

1 gallon of diesel in a power station to charge a Tesla Vs using the diesel directly and assuming the average 7,100 miles

A modern diesel might get 65mpg

A gallon of diesel in a CCGT @55% through a grid with 8% loss then charging a Tesla at 85% and the Tesla getting an average 2.8 miles per kWh including dead time and self discharge works out to 59 mpg

Any of the processes to make the diesel are the same


So it seems even though an electric motor is very efficient
Power station losses
Grid losses
Charging losses
Standing losses
All add up to make an EV on typical usage no more primary energy efficient

Using diesel is just for comparison purposes to keep it simple for lay persons
You could put the equivalent thermal energy of natural gas in the power station
Of course if you have a green grid this is fine but most grids are still marginal coal or NG

So a TM3 is worse than an efficient diesel in grids that are marginal coal (Poland & Germany for instance,)
And roughly equal in grids that are marginal NG (UK today) or oil (Japan?/Saudi)
And much better in marginal nuclear or hydro (France & Norway)

You can get 65mpg out of some smaller diesels, but if you're going to use the TM3 as an electric example you need to compare it with a BMW 335d or 340i....40mpg & 32mpg.

Most EV owners in the UK will charge after midnight on a low rate tariff using wind & nuclear power.

Martyn1981

GreatApe wrote: »

1 gallon of diesel in a power station to charge a Tesla Vs using the diesel directly and assuming the average 7,100 miles

A modern diesel might get 65mpg

A gallon of diesel in a CCGT @55% through a grid with 8% loss then charging a Tesla at 85% and the Tesla getting an average 2.8 miles per kWh including dead time and self discharge works out to 59 mpg

Any of the processes to make the diesel are the same


So it seems even though an electric motor is very efficient
Power station losses
Grid losses
Charging losses
Standing losses
All add up to make an EV on typical usage no more primary energy efficient

Using diesel is just for comparison purposes to keep it simple for lay persons
You could put the equivalent thermal energy of natural gas in the power station
Of course if you have a green grid this is fine but most grids are still marginal coal or NG

So a TM3 is worse than an efficient diesel in grids that are marginal coal (Poland & Germany for instance,)
And roughly equal in grids that are marginal NG (UK today) or oil (Japan?/Saudi)
And much better in marginal nuclear or hydro (France & Norway)

We barely use any diesel for leccy generation, so I fail to see the point of your example.

So we have losses in the leccy grid, around 8%, and battery charging, let's say another 15%, or 25% total for arguments sake, so 75% efficient.

V's, petrol and diesel ICE's that waste around 60-80% of the energy in their fuel tanks as heat, noise, exhaust.

But, what about all the losses I mentioned before it gets to the fuel tanks, we're probably down to single digit efficiency then, yes?

So an EV at 75% v's an ICE at 7.5% seems reasonable?

GreatApe

1961Nick wrote: »

You can get 65mpg out of some smaller diesels, but if you're going to use the TM3 as an electric example you need to compare it with a BMW 335d or 340i....40mpg & 32mpg.

Most EV owners in the UK will charge after midnight on a low rate tariff using wind & nuclear power.

I used to have an old diesel Renault that would clock over 60mpg average and even higher on the motorways

UK at night isn't wind and nuclear it depends on the night
When the wind blows strong yes
Other times no

For instance this Monday Tuesday Wednesday was marginal gas while Thursday night was marginal green and the rest of the week remains to be seen


Interestingly do you have a breakdown of how many charge specifically on a night time 12-5 am and how many just plug in when they just home

Martyn1981

GreatApe wrote: »

I used to have an old diesel Renault that would clock over 60mpg average and even higher on the motorways

The older diesels did get higher fuel economy, but they also had far higher pollution too.

All of your posts seem to miss the 'Green & Ethical' issues.

GreatApe

Martyn1981 wrote: »

We barely use any diesel for leccy generation, so I fail to see the point of your example.

So we have losses in the leccy grid, around 8%, and battery charging, let's say another 15%, or 25% total for arguments sake, so 75% efficient.

V's, petrol and diesel ICE's that waste around 60-80% of the energy in their fuel tanks as heat, noise, exhaust.

But, what about all the losses I mentioned before it gets to the fuel tanks, we're probably down to single digit efficiency then, yes?

So an EV at 75% v's an ICE at 7.5% seems reasonable?

An EV is about 25% chemical energy in a power station to motion
An oil car is about 25% chemical energy in a tank to motion

I used diesel so it's a direct comparison and I said you could use the same thermal energy of natural gas if you like (or even coal)

An EV may indeed be about 70% efficient when moving, but the point of this thread is to highlight it's 0% efficient when not moving. The two averaged together drags this headline 70% (or whatever) further down


Going back to the math again
Assume an EV has idle annual energy use of 500KWh to keep it a round figure
Assume an EV does the average 7,100 miles for 1,730KWh (so 4.1 miles per kWh)
The total combined is an annual 2,230KWh
Assume grid loss of 8% and charge of 15% you get 2,850 KWh at the power station

That is to say an EV with a headline figure of 4.1 miles per KWh actually in this example is getting 2.5 miles per KWh (as measured at the power station)

And since most the world is still marginal coal gas or oil these EVs are indirectly powered by coal gas and oil.


If Gas/Oil fired nation at 50% efficiency works out to 1.25 miles per KWH thermal
If Coal powered nation at 40% efficiency works out to 1 mile per KWh thermal

By comparison this telsa model 3 is also roughly 1.25 miles per KWh

That is to say they use about as much primary energy as a good diesel if the nation is gas or oil marignal and more primary energy if coal


Re your point it takes energy to refine crude
Well it takes energy to mine move and crush coal into a power
It takes energy to drill clean pump liquify pipe compress NG

GreatApe

GreatApe wrote: »

That is to say an EV with a headline figure of 4.1 miles per KWh actually in this example is getting 2.5 miles per KWh (as measured at the power station)

Quoting myself...this means there is a 40% loss for a typical UK model 3 owner irrespective of where the energy comes from

Grid loss
Charging loss
Standby loss

If charged by a 50% efficient CCGT fleet (as per the UK) you get an overall efficiency of ~30% chemical energy into useable charge in the battery

There are still further losses in the battery DC to AC and then electricity power to motion
Probably looking at less than 25% chemical (coal gas oil) to kinetic energy

Not too dissimilar to petrol or diesel

Of course the advantages is EVs can be nuclear or solar or wind powered
But for now the world's major grids are not clean so for now EVs probably don't reduce fossil fuel burn much at all they just shift it from oil to coal/gas