Electric - It shouldn't need my 12 year old to tell you..

[anonymous-user]

bearman68 said:

Some small Co2 benefit.

The best data so far for an EV operated in the UK as a like-for-like replacement for a similar size/performance ICE vehicle is that the EV emits, on average over a calendar year, approximately 4 times less Co2 per mile it is driven (with our current Q4 2016 / Q1 2017 grid generation mix)

I'd not call that a "small" benefit myself.

[Heres Johnny]

Max_Torque said:

Ok, explain to me the physics behind that statement. ("EVs suffer massively due to the cold")

You may need to make reference to the resistance of conductors vs their temperature, the effect of cold temperatures on electron mobility in chemical storage elements, and calculations of sliding friction, oil film shear strength and other parasitic losses for ICEs.


What you'll actually find is that EVs get more efficient, ie use less energy for a given driving distance, as they get cold because most conductors have a positive temperature co-efficient of resistance, but their maximum range is reduced due to a reduction of charge carrier mobility in their energy storage system. However RANGE != CONSUMPTION

Edited by Max_Torque on Wednesday 27th September 19:53

Bo11ocks. You need to tell the cars.

My Tesla uses 20% more wh/m when the temperature is below 10 deg c.

My petrol cars on a cold crisp low humidity day simply fly.

[GT119]

Heres Johnny said:

Bo11ocks. You need to tell the cars.

My Tesla uses 20% more wh/m when the temperature is below 10 deg c.

My petrol cars on a cold crisp low humidity day simply fly.

Denser air into the engine, more fuel to match, more power.

I don't think your mpg will be better.

[GT119]

Gary C said:

Name calling ?

I was trying to get this thread on some direction without personal attacks.

The pressure is environmental and health ? the diesel issue is fairly new and all I've seen so far talks about 'linked to deaths' rather than facts, co2 is an emotive subject that we will only find out the truth it seems when it's happened?
In the bleakest interpretation of these issues, we will have to suffer a reduction in our mobility but it's really hard for most of us to know the truth when there is so much conflicting information.

Bio fuels seem to be bad due to the effect on food chain in poor countries, I do wonder what sort of mpg a car would need to have to allow sustainable bio fuel use ?

Problem I see with euro gov's banning anything but electric, is it suppresses any sort of investigation and investment into any possible better alternatives. However it dos set a marker for change as we humans are very good at the 'a few more years, then we we'll sort it out'

Apologies, the last line wasn't directed at you per se, it was in response to the more vocal anti-EV posters that spout rubbish about milk floats, hundreds of new power stations required, etc.

[Heres Johnny]

GT119 said:

Denser air into the engine, more fuel to match, more power.

I don't think your mpg will be better.

Maybe, but still doesn’t explain the increase consumption in my Tesla. It’s well known consumption in EVs suffers significantly in winter.

[Heres Johnny]

DELETED: Comment made by a member who's account has been deleted.

Shame he doesn’t realise in winter a battery pack needs to be warm to achieve a sensible rate of outflow of electrons and consequently its efficiency drops.

Scroll to the bottom of this page and try changing the temperature and watch the range change

https://www.tesla.com/en_GB/models

[anonymous-user]

Heres Johnny said:

GT119 said:

Denser air into the engine, more fuel to match, more power.

I don't think your mpg will be better.

Maybe, but still doesn’t explain the increase consumption in my Tesla. It’s well known consumption in EVs suffers significantly in winter.

Consumption increases because drag increases! (cold air = higher density = more aero drag)

But your ICE needs to warm up before it can run efficiently. At say zero degC engine and transmission friction is approaching twice that of the same engine at operating temp (90 degC). And to get the catalyst to light off (and reduce pollutant emissions) you engine, when cold will retard spark, and idle faster, again, burning more fuel. And as air density increases with the colder air it is ingesting, for any given part throttle engine output, that engines pumping losses increase, again using more fuel.


Your Tesla uses more energy because it has to push more air out the way, (exactly the same for your ICE, as it's road load increases identically!) but the Tesla's powertrain gets MORE efficient because resistive losses fall as temperature falls!

[anonymous-user]

Heres Johnny said:

DELETED: Comment made by a member who's account has been deleted.

Shame he doesn’t realise in winter a battery pack needs to be warm to achieve a sensible rate of outflow of electrons and consequently its efficiency drops.

Scroll to the bottom of this page and try changing the temperature and watch the range change

https://www.tesla.com/en_GB/models

Range falls in winter, no one is saying it doesn't. But this is because the effective SoC of the battery falls, and the occupants tend to do things like demanding more cabin heating etc. On your ICE, the engine is so wasteful, we can heat our cabins from all the energy we just throw over board ALL THE TIME (approx 70% of the fuel we put in the car is just wasted as heat, or if we include braking too, then it's more like 90%)

But in terms of EFFICIENCY, ie turning stored energy into useful work, and EV is more efficient the colder it gets. In fact, ideally, we would run our EV motors and inverters at absolute zero (-273 degC) and Superconductivity effects would render the inverter and motor pretty much 100% efficient! (unfortunately, it would also render the effective SoC of the battery to be zero as well ;-)

In the real world, where the vast majority of cars do short journeys twice a day, and hence pretty much start from a full cold soak, the losses from operation during the warm up cycle are extremely significant.

[bearman68]

Max_Torque said:

The best data so far for an EV operated in the UK as a like-for-like replacement for a similar size/performance ICE vehicle is that the EV emits, on average over a calendar year, approximately 4 times less Co2 per mile it is driven (with our current Q4 2016 / Q1 2017 grid generation mix)

I'd not call that a "small" benefit myself.

Show me!

But please stop using 4 times less. It has no meaning. If you mean 25% say so.

[Gary C]

GT119 said:

Apologies, the last line wasn't directed at you per se, it was in response to the more vocal anti-EV posters that spout rubbish about milk floats, hundreds of new power stations required, etc.

Ah' sorry, fair enough. It's the problem with forums, it's easy to grab the wrong end of the stick

[Heres Johnny]

Max_Torque said:

Range falls in winter, no one is saying it doesn't. But this is because the effective SoC of the battery falls, and the occupants tend to do things like demanding more cabin heating etc. On your ICE, the engine is so wasteful, we can heat our cabins from all the energy we just throw over board ALL THE TIME (approx 70% of the fuel we put in the car is just wasted as heat, or if we include braking too, then it's more like 90%)

But in terms of EFFICIENCY, ie turning stored energy into useful work, and EV is more efficient the colder it gets. In fact, ideally, we would run our EV motors and inverters at absolute zero (-273 degC) and Superconductivity effects would render the inverter and motor pretty much 100% efficient! (unfortunately, it would also render the effective SoC of the battery to be zero as well ;-)

In the real world, where the vast majority of cars do short journeys twice a day, and hence pretty much start from a full cold soak, the losses from operation during the warm up cycle are extremely significant.

So you agree with me? EV do suffer from the cold

And on longer journeys where an ICE can use waste heat from the engine to warm the cabin and EV has to turn on a 3kw fire

Trying to make an argument that EVs are better for reasons that in the real world they are not seems a self defeating policy.

[GT119]

Gary C said:

GT119 said:

Apologies, the last line wasn't directed at you per se, it was in response to the more vocal anti-EV posters that spout rubbish about milk floats, hundreds of new power stations required, etc.

Ah' sorry, fair enough. It's the problem with forums, it's easy to grab the wrong end of the stick

It was a few days ago, I now recall that I was making a pun about the OP, his posting style and his username

[Evanivitch]

Heres Johnny said:

So you agree with me? EV do suffer from the cold

And on longer journeys where an ICE can use waste heat from the engine to warm the cabin and EV has to turn on a 3kw fire

Trying to make an argument that EVs are better for reasons that in the real world they are not seems a self defeating policy.

I look forward to defrosting my PHEV from the comfort of my living room on frosty mornings.

[InitialDave]

Mm.

How much of my potential motive power is used to heat my car first thing on a winter morning leaving for work? None. It's already done it itself while plugged in, based on the time I told it I wanted to set off.

Yes, it requires the battery power to maintain the cabin at whatever the temperature is set to, but getting it there initially has been done from the plug in supply.

[Evanivitch]

InitialDave said:

Mm.

How much of my potential motive power is used to heat my car first thing on a winter morning leaving for work? None. It's already done it itself while plugged in, based on the time I told it I wanted to set off.

Yes, it requires the battery power to maintain the cabin at whatever the temperature is set to, but getting it there initially has been done from the plug in supply.

It's not just the cabin that is heated on most EVs though, the Ampera for example will use Electricity to precondition the batteries before the journey which limits the impact of cold weather on range.

[InitialDave]

Evanivitch said:

It's not just the cabin that is heated on most EVs though, the Ampera for example will use Electricity to precondition the batteries before the journey which limits the impact of cold weather on range.

True enough, yes.

[anonymous-user]

bearman68 said:

Max_Torque said:

The best data so far for an EV operated in the UK as a like-for-like replacement for a similar size/performance ICE vehicle is that the EV emits, on average over a calendar year, approximately 4 times less Co2 per mile it is driven (with our current Q4 2016 / Q1 2017 grid generation mix)

I'd not call that a "small" benefit myself.

Show me!

Consider a VW golf diesel vs an BMW i3 (similar size, similar performance (i3 is actually quicker) driven over the NEDC cycle (which is best case for an ICE, being a nice warm 25degC start, and having a very gentle road load profile).

The Golf returns 109 g/km and 59mpg, so over that 11.023Km drive cycle the Golf uses 18.89 MJ of energy

The i3, does 12.6 kWh/100km over the same cycle, so uses just 5.0 MJ of energy


That's 3.8 times less energy to drive exactly the same distance and speed



So even if we only charged our EV directly from a coal fired power station that had the same, low, thermal efficiency as your ICE then the tailpipe (chimney) emissions from that powerstation are enormously lower than the local emissions from the tailpipe of an ICE, even including the 7% electrical transmission loses (And we haven't accounted for the emissions produced actually getting the fuel into the fuel tank of your ICE, but we did include charging losses for the EV because the EV economy test measures the electrical energy you put into the car, not what comes out, so considering you have to drive your ICE to the petrol station, and the fuel has to get to the station somehow, we are again weighting the test towards the ICE.


But in reality, even old tech coal fired powerstations are way more efficient (due to thermodynamic scaling (surface area to volume) effects and large scale heat recuperation (waste heat pre-warms inlet air etc)) than the ICE in passenger cars, especially passenger cars driven under variable, non ideal conditions.

Finally, in reality, our Grid is no longer just coal based. Today, low carbon generation assets (wind, solar, nuclear) are contributing something like 25% of our total yearly load (and peaking at up to 50% for short periods). And whilst those assets are not "zero carbon" compared to classical sources they are decades lower in terms of emission per kWhr.


And finally, we have used the official consumption results, which due to no cold start, and a decent distance driven flatter the ICE. In reality, most drivers fail to return anything like the official consumption numbers, due to poor driving techinque, Traffic congestion (stop start, low gears), cold starting, short journeys. I'd suggest that for most people, in the real world achieve between 60 and 70% of the official numbers, meaning real world consumption is commensurately higher.

[Knock_knock]

Max_Torque said:

Finally, in reality, our Grid is no longer just coal based. Today, low carbon generation assets (wind, solar, nuclear) are contributing something like 25% of our total yearly load (and peaking at up to 50% for short periods). And whilst those assets are not "zero carbon" compared to classical sources they are decades lower in terms of emission per kWhr.

According to www.mygridgb.co.uk, over the last twelve months "low carbon" power sources have contributed 45.9% of supply.

http://www.mygridgb.co.uk/last-12-months/

Also, to deal with another point raised a few pages ago about the environmental cost of producing EV's over conventional ICE, the Union of Concerned Scientists put the excess at 16% for a Nissan Leaf type vehicle, and that overall EV's generate half the emissions of the average comparable ICE car, even when pollution from battery manufacturing and disposal is incuded.

http://www.ucsusa.org/clean-vehicles/electric-vehi...

[Heres Johnny]

Evanivitch said:

InitialDave said:

Mm.

How much of my potential motive power is used to heat my car first thing on a winter morning leaving for work? None. It's already done it itself while plugged in, based on the time I told it I wanted to set off.

Yes, it requires the battery power to maintain the cabin at whatever the temperature is set to, but getting it there initially has been done from the plug in supply.

It's not just the cabin that is heated on most EVs though, the Ampera for example will use Electricity to precondition the batteries before the journey which limits the impact of cold weather on range.

But as the heating is coming directly from the mains we can completely ignore it from the efficiency calculations? Thats not the point. You're in danger of sounding like a phev driver who can get 80 mpg out of their car over 15 miles but they've ignored the fact they've also depleted their battery of £1 of charge.

EVs are still way better than ICE, they are just even more efficient in summer than they are in winter.

Edited by Heres Johnny on Thursday 28th September 15:48

[Evanivitch]

Heres Johnny said:

But as the heating is coming directly from the mains we can completely ignore it from the efficiency calculations? Thats not the point. You're in danger of sounding like a phev driver who can get 80 mpg out of their car over 15 miles but they've ignored the fact they've also depleted their battery of £1 of charge.

EVs are still way better than ICE, they are just even more efficient in summer than they are in winter.

Edited by Heres Johnny on Thursday 28th September 15:48

We weren't discussing efficiency, we were discussing cold weather performance of EVs.

Not really sure what you're accusing me of sounding like. Especially as the Ampera isn't a soft hybrid, it operates through its full performance envelope on EV if required.