BMW: All Models Electric Within Decade
Discussion
turbobloke said:
The average coupled steam turbines fed by burning fossil fuel in a power station have an efficiency of just over 40%. Transmission losses in the grid due to resistance and other losses are about 10% so say 90% efficient, and then there are step-up-step-down transformers each about 95% efficient. End-user charging on top has an efficiency of about 95%. Take electric car efficiency as about 85%, the electric motor itself can be 90% efficient at peak but falls to 70% or below at low speed and there are other losses. This puts the overall effiency from power station fuel burning to end user electric car operation as follows with one step-up-down:
40% x 90% x 95% x 95% x 95% x 85% ~ 25%
Numbers vary slightly from source to source but the overall postition won't be too different from this wherever you look, and it represents an overall efficiecy of about 25%.
Taking the very best modern 'H-System' power generators moves the final figure to over 30% which is less than the best oil burners which are over 40% and about the same as the best petrol engines.
In summary a modern efficient (petrol) car can achieve 30% efficiency and the best diesels are around 42% efficiency. In comparison with electric cars, diesel wins and at best (for electric) it's a tie with petrol.
Except, and there's always an except, efficiency is NOT the be all and end all of mass transport! I.E. What actually matters in the final reckoning is overall consumption.40% x 90% x 95% x 95% x 95% x 85% ~ 25%
Numbers vary slightly from source to source but the overall postition won't be too different from this wherever you look, and it represents an overall efficiecy of about 25%.
Taking the very best modern 'H-System' power generators moves the final figure to over 30% which is less than the best oil burners which are over 40% and about the same as the best petrol engines.
In summary a modern efficient (petrol) car can achieve 30% efficiency and the best diesels are around 42% efficiency. In comparison with electric cars, diesel wins and at best (for electric) it's a tie with petrol.
If you have a car that say has an efficiency of 100%, but has a roadload of 1000kJ to do a mile, it will have a high consumption that a car with just 50% efficiency, but only has a roadload of 450kJ for that mile!
And that's the thing with electric cars, their total road load is significantly lower than for any ICE vehicle. Easy test, go find an electric motor, and spin the shaft with your hand, now try the same for say the piston engine on your lawnmower! The point being that engine friction is enormous on the ICE, and that is an unrecoverable loss. Add in the ability to use virtually no power when not moving, and recover KE from the cars mass when braking, and an EV has a road load that on average (UK average driving speed / distance) is around 3x lower than for a similar ICE powered one!
Further roadload advantages come from the reduction in cooling drag, and overall Cda reductions due to better packaging etc.
So whilst say a current "High efficiency" compression ignition engine might just be able to match, or even slightly exceed the overall efficiency of a pure EV, it can only do so at a single operating condition. In the real world, the advantage is very much with the EV!
(as you should be able to realise from the relatively small battery size vs range. ie
Nissan Leaf: 86.4kJ (24kWHr battery) range ~80 miles = 1080kJ/mile
Nissan Note: 1328400kJ (41 litres) range 550 miles (~60mpg) = 2405kJ/mile
Ie, the Note, not exactly what you would call a "Gas Guzzler" uses 2.2 x more energy per mile it moves, and in fact, it's relatively small fuel tank (41L) is equivalent to a 370 kWHr battery!!!)
Edited by anonymous-user on Monday 31st August 11:40
And as far as I know, there is no car powered directly by internal combustion which can even get close to 40% in practical usage; I doubt there any such car which averages over 20% in anything which could reasonably be considered "mixed road driving". Series hybrids might manage 40% from the ICE component.
Of course you're also conveniently including generation and transmission losses for the EVs but not refinement and transportation costs for the ICE fuels (which are not insignificant). And you've ignored regenerative braking, which can push the efficiency of the motor "over 100%" compared to an ICE in some types of driving.
Of course you're also conveniently including generation and transmission losses for the EVs but not refinement and transportation costs for the ICE fuels (which are not insignificant). And you've ignored regenerative braking, which can push the efficiency of the motor "over 100%" compared to an ICE in some types of driving.
Edited by kambites on Monday 31st August 12:03
goneape said:
Another point is the one Kambites makes about grid power consumption falling as refineries won't be so active in a PHEV-dominant era. Before criticising the guy I'll make the caveat that I don't know what he does for a living, and my knowledge is based on academia rather than practicality; but as I see it there are a couple of problems with this assertion. Firstly, while its true that refineries consume a huge amount of energy to do what they do, most of the thermal energy is provided by steam, which is raised on site by burning coal, oil, or gas. Power - electricity - is a byproduct. While some very high temperatures are required, anything above 380C (as hot as it gets for steam) is provided by burning gas, a byproduct of which is also electricity. I can't say for certain (and maybe kambites can) but I believe an oil refinery is a net producer of electricity, not a consumer - after all, it's in their interests to be so and they have the flexibility and capability to be so.
You may be right that the oil refining business is a net producer (I rather suspect it depends on where you draw the boundaries) but it could be a much bigger (and more efficient) net producer if the sites were modified to solely produce electricity and would obviously give an enormous reduction in fossil fuel consumption if the sites were simply shut down. It's mostly a moot point anyway because grid-powered electric cars are clearly not the solution to all of our transport needs; it's going to be decades before we can realistically power more than about half our private passenger mileage from the grid and there's easily enough spare off-peak capacity for that. Yes, we will need a way to shut off chargers to cope with other spikes in demand but that hardly sounds like it should be impossible.
Of course there's also the small-scale solar industry. Most people I know who have an EV are net contributors to the grid. Obviously that's only currently viable because of huge subsidies from the government but it's another technology which is improving at a fairly impressive rate. Who knows if it'll ever actually be commercially viable but like it or not we're committed to reducing our fossil fuel usage and I suspect it's not much more expensive than nuclear at the moment?
Edited by kambites on Monday 31st August 11:58
Max_Torque said:
And that's the thing with electric cars, their total road load is significantly lower than for any ICE vehicle. Easy test, go find an electric motor, and spin the shaft with your hand, now try the same for say the piston engine on your lawnmower! The point being that engine friction is enormous on the ICE, and that is an unrecoverable loss. Add in the ability to use virtually no power when not moving, and recover KE from the cars mass when braking, and an EV has a road load that on average (UK average driving speed / distance) is around 3x lower than for a similar ICE powered one!
Not a true comparison as the majority of what stops someone turning their crank by hand is the compression, where the compression is almost fully recovered on the expansion stroke (see why cylinder deactivation works as I'm sure you know).Yes, ICEs carry more friction but your analogy isn't fair. Maybe if you removed the plugs and tried it again
Turbobloke - what you are trying to say is Well to Wheel efficiency. The numbers are still in favour of the BEV/PHEV when you take this in to account.
http://www.afdc.energy.gov/vehicles/electric_emiss...
Above is the US Department of Energy calculations of Well to Wheel comparing ICEs, BEVs, PHEVs etc. They show their working too which helps.
Edited by GroundEffect on Monday 31st August 12:04
Max_Torque said:
And that's the thing with electric cars, their total road load is significantly lower than for any ICE vehicle. Easy test, go find an electric motor, and spin the shaft with your hand, now try the same for say the piston engine on your lawnmower! The point being that engine friction is enormous on the ICE, and that is an unrecoverable loss.
I'm not disputing anything you say, but your example above isn't very fair to the ICE engine as the friction drops dramatically once it's running and all the bearings are floating on a bed of oil, which isn't far off being frictionless (maybe a slight exaggeration
). Obviously it's no electric motor, and there's a lot of load involved in driving the camshafts/valves and stopping/starting the pistons twice per revolution, but it's nothing like the level of friction that occurs in an engine that isn't running, simply as there's no oil pressure to keep the bearing surfaces away from each other.
GroundEffect said:
Not a true comparison as the majority of what stops someone turning their crank by hand is the compression, where the compression is almost fully recovered on the expansion stroke (see why cylinder deactivation works as I'm sure you know).
Yes, ICEs carry more friction but (the) analogy isn't fair. Maybe if you removed the plugs and tried it again
Yes, ICEs carry more friction but (the) analogy isn't fair. Maybe if you removed the plugs and tried it again
GroundEffect said:
Turbobloke - what you are trying to say is Well to Wheel efficiency. The numbers are still in favour of the BEV/PHEV when you take this in to account.
CNWM also look at well to wheel, I take it you've read all 400+ pages?GroundEffect said:
Above is the US Department of Energy calculations of Well to Wheel comparing ICEs, BEVs, PHEVs etc. They show their working too which helps.
Sources differ, that's not unusual, I've read as many as I can find. I would expect government dept sources to support gov't policy. There are careers depending on it. Over here, DECC publications suffer from the same effects.CNWM's "Dust to Dust" is specifically titled as a 'Non Technical Report' but it's clear from reading it was the methodology is.
Max_Torque said:
Except, and there's always an except, efficiency is NOT the be all and end all of mass transport! I.E. What actually matters in the final reckoning is overall consumption.
If you have a car that say has an efficiency of 100%, but has a roadload of 1000kJ to do a mile, it will have a high consumption that a car with just 50% efficiency, but only has a roadload of 450kJ for that mile!
Energy consumption per mile in general embodies conversion efficiency and speed considerations - not sure what your point was?If you have a car that say has an efficiency of 100%, but has a roadload of 1000kJ to do a mile, it will have a high consumption that a car with just 50% efficiency, but only has a roadload of 450kJ for that mile!
At any given speed: rate of energy consumption = force required to equal all resistances (including aero) x velocity
You will no doubt have seen publications such as Tenniswood et al (electric cars) and Kadijk & Ligterink on road load determination involving petrol/diesel vehicles.
Max_Torque said:
Easy test, go find an electric motor, and spin the shaft with your hand, now try the same for say the piston engine on your lawnmower! The point being that engine friction is enormous on the ICE, and that is an unrecoverable loss.
Those are efficiency considerations, already taken into account in what I posted earlier. Typical individual petrol/diesel and electric motor efficiencies were quoted and the electric motor was of course more efficient, but there are other factors involved which were also included.Max_Torque said:
Add in the ability to use virtually no power when not moving, and recover KE from the cars mass when braking, and an EV has a road load that on average (UK average driving speed / distance) is around 3x lower than for a similar ICE powered one!
Further roadload advantages come from the reduction in cooling drag, and overall Cda reductions due to better packaging etc.
CdA reductions are available to all types of car.Further roadload advantages come from the reduction in cooling drag, and overall Cda reductions due to better packaging etc.
Edited by turbobloke on Monday 31st August 12:33
Super Slo Mo said:
I'm not disputing anything you say, but your example above isn't very fair to the ICE engine as the friction drops dramatically once it's running and all the bearings are floating on a bed of oil, which isn't far off being frictionless (maybe a slight exaggeration).
Obviously it's no electric motor, and there's a lot of load involved in driving the camshafts/valves and stopping/starting the pistons twice per revolution, but it's nothing like the level of friction that occurs in an engine that isn't running, simply as there's no oil pressure to keep the bearing surfaces away from each other.
A typical 4 cyl ICE has around 40 to 50Nm of friction at idle. ). Obviously it's no electric motor, and there's a lot of load involved in driving the camshafts/valves and stopping/starting the pistons twice per revolution, but it's nothing like the level of friction that occurs in an engine that isn't running, simply as there's no oil pressure to keep the bearing surfaces away from each other.
A typical synchronous PM Emachine has around 0.1Nm of friction at "idle"
Here's an easy test. Accelerate you car to 60mph. Leave it in gear, lift off accelerator, note how car deccelerates. Now repeat in neutral. You'll be able to feel a MASSIVE difference!!
(ok there are some pumping losses involved as well, but the point stands)
turbobloke said:
CdA reductions are available to all types of car.
They maybe, but the packaging efficiency of "high speed" electric traction motors mean you can make a car with lower dragAnd the cooling drag is not to be disregarded. Not for nothing to modern cars close off their cooling apertures at low loads to reduce this form drag!. An 100kW electric powertrain at say 70% efficiency is dumping 30kW overboard, and 100kW ICE is dumping at least double, and more often tripple that heat, requiring massive radiators etc. All of which add drag! (Including the drag from things like the exhaust systems etc)
That was acknowledged earlier "the electric motor itself can be 90% efficient at peak but falls to 70% or below at low speed and there are other losses" but as per the post with that extract, there's more to it than that.
ETA when pointing out that the CNWM report includes Well to Wheel it should be obvious that a Dust to Dust consideration, "Concept to Disposal", covers the entire vehicle life cycle.
ETA when pointing out that the CNWM report includes Well to Wheel it should be obvious that a Dust to Dust consideration, "Concept to Disposal", covers the entire vehicle life cycle.
Edited by turbobloke on Monday 31st August 12:47
It's also worth noting, that as you move away from the legally mandated test schedules and into the real world EVs get better and better!
EG
On the NEDC for example, the brakes are used once (down the final "Hill"). In the real world, most average drivers are on their brakes the whole time. EV's recover a proportion of that energy, ICEs throw it away into heat in the brakes.
On the NEDC, no modern engine will need to go into component protection enrichment because the average road load is low. In the real world, i see drivers of all sorts of cars going to WOT regularly (usually accompanied by that puff of black soot these days....) At this point, ICE engine efficiency takes a massive dive. An EV doesn't "overfuel", and actually gets more efficient at high loads
On the NEDC, the car is always in the perfect gear, and hence operating the powertrain at the most efficient point. In the real world, a lot of drivers i know are hardly ever in the most efficient gear! EV's have such a wide "island" of high efficiency this becomes irrelevant (in fact, to the point where most don't even have gears)
On the NEDC, the car is started at 25degC. In the real world, especially the UK, you pretty much never start your car at 25degC, more like 10, and for a lot of the yeat probably sub 10degC. For an EV, that makes no difference, and in fact it improves efficiency! For an ICE, a cold start is pretty catastrophic to fuel consumption as it has to warm itself up first (high friction & enrichment)
As i said earlier, the fact that EV's can get around in the real world with batteries as small as 25kWHr, equivalent to just 2.6 litres of gasoline shows how good they actually are. Even a Tesla, with it's "massive" battery (85kWHr) is equivalent to just 9.4L of gasoline.
And back on topic, it's worth noting that it's not just BMW who will be highly hybridized within the next two model cycles, all of my OE passenger car customers are currently crashing the development of similar powertrains!
EG
On the NEDC for example, the brakes are used once (down the final "Hill"). In the real world, most average drivers are on their brakes the whole time. EV's recover a proportion of that energy, ICEs throw it away into heat in the brakes.
On the NEDC, no modern engine will need to go into component protection enrichment because the average road load is low. In the real world, i see drivers of all sorts of cars going to WOT regularly (usually accompanied by that puff of black soot these days....) At this point, ICE engine efficiency takes a massive dive. An EV doesn't "overfuel", and actually gets more efficient at high loads
On the NEDC, the car is always in the perfect gear, and hence operating the powertrain at the most efficient point. In the real world, a lot of drivers i know are hardly ever in the most efficient gear! EV's have such a wide "island" of high efficiency this becomes irrelevant (in fact, to the point where most don't even have gears)
On the NEDC, the car is started at 25degC. In the real world, especially the UK, you pretty much never start your car at 25degC, more like 10, and for a lot of the yeat probably sub 10degC. For an EV, that makes no difference, and in fact it improves efficiency! For an ICE, a cold start is pretty catastrophic to fuel consumption as it has to warm itself up first (high friction & enrichment)
As i said earlier, the fact that EV's can get around in the real world with batteries as small as 25kWHr, equivalent to just 2.6 litres of gasoline shows how good they actually are. Even a Tesla, with it's "massive" battery (85kWHr) is equivalent to just 9.4L of gasoline.
And back on topic, it's worth noting that it's not just BMW who will be highly hybridized within the next two model cycles, all of my OE passenger car customers are currently crashing the development of similar powertrains!
Under current EU policy that's hardly surprising but it's political dependency not reflecting any form of absolute superiority. This path is what politicians want for now, it may continue, it may change. Meanwhile the relative merits and demerits exist quite apart from political machinations.
I wont be touching them with a 10ft pole until battery tech improves big time. The 1st gen prius's are all but useless nowadays with the old batteries not functioning or being able to hold a charge. They are also costing a fortune (1.5-2k) to replace. Not to mention the production methods for producing large chemical batteries is not sustainable and trashes local enviroments, not that the western market has ever had a problem with that.
To add to that again using prius's as an example the battery tech is designed to not be user or small garage servicable. Ive heard twice people getting battery errors which have merited a "battery replacement" at a dealer, which however was a somewhat easy fix as all that was causing it was some of the electrical contacts becoming eroded. It all brings up the same OBD error though and requires someone with a background in electrical engineering to service.
To add to that again using prius's as an example the battery tech is designed to not be user or small garage servicable. Ive heard twice people getting battery errors which have merited a "battery replacement" at a dealer, which however was a somewhat easy fix as all that was causing it was some of the electrical contacts becoming eroded. It all brings up the same OBD error though and requires someone with a background in electrical engineering to service.
turbobloke said:
That was acknowledged earlier "the electric motor itself can be 90% efficient at peak but falls to 70% or below at low speed and there are other losses" but as per the post with that extract, there's more to it than that.
Again, efficiency is a somewhat misleading value.At idle, the engine in your car is 0% efficient. The fuel it burns just keeps it spinning round (typically 40Nm @ 650rpm = 2.7kW (the same power required to push a typical family sized car to around 40kph!)).
An electric motor doesn't idle. It stops, drawing practically zero power (the power electronics will be powered but not switching, consuming about 50w).
Peak efficiency is WAY higher than 90% for a modern PM electric machine, in fact, for the motor itself, most modern SPMs/IPMs are over 98% efficient at peak, and that peak covers something like 30% of their operating range. Add in the battery and inverter losses and you are still talking about over 90% efficiency.
In fact, for the GM Volt i have personally benchmarked, the total electric traction system round trip efficiency over the NEDC is approx 72% and that includes 1.5x the power transfer total of an ICE because the system is bi-directional (ie, the system moves energy out to both the roadload (lost) and the cars KE (recovered). An ICE is, in effect, 0% efficient when slowing down!!! (KE -> Roadload + Loses).
Of course you need to include battery charging losses, but again, these are significantly lower than the might first appear as charger & battery tech has moved on (low loss power switches and low Ri battery systems) And for ICE, there is often a "Loss" involved with "recharging" in that you need to drive to a fuel station to do so, and hence consume some fuel to refill the tank.
caelite said:
I wont be touching them with a 10ft pole until battery tech improves big time. The 1st gen prius's are all but useless nowadays with the old batteries not functioning or being able to hold a charge. They are also costing a fortune (1.5-2k) to replace. Not to mention the production methods for producing large chemical batteries is not sustainable and trashes local enviroments, not that the western market has ever had a problem with that.
To add to that again using prius's as an example the battery tech is designed to not be user or small garage servicable. Ive heard twice people getting battery errors which have merited a "battery replacement" at a dealer, which however was a somewhat easy fix as all that was causing it was some of the electrical contacts becoming eroded. It all brings up the same OBD error though and requires someone with a background in electrical engineering to service.
er, a 1st gen Prius minimum of 12 years old now! How many pre 2003 ICE Nissans are still working and not requiring new components?? (in fact, a lot will have simply been scrapped as "worthless")To add to that again using prius's as an example the battery tech is designed to not be user or small garage servicable. Ive heard twice people getting battery errors which have merited a "battery replacement" at a dealer, which however was a somewhat easy fix as all that was causing it was some of the electrical contacts becoming eroded. It all brings up the same OBD error though and requires someone with a background in electrical engineering to service.
Yes, it takes some knowledge to open up an EV battery and clean the bus bar contacts, but i'd also suggest it requires some knowledge to whip the engine out of your micra and replace the main bearings or whatever!
Their hybrid 3 and 5 series are very good already, turbo 3lr petrol straight six with a battery boost which allows most of the features people like (town driving on silent electric power, big boost of torque for overtaking, power regeneration, pre-warm up in winter and extra electric power to charge and run all the toys) with no real disadvantage other than a slight increase in weight and cost. Gives a real world 35mpg compared to 30mpg in the standard car on most journeys, increasing hugely if you drive stop start or motorway cruising. Only downside is they are automatic only but that seems to be the way the market is moving for that kind of car anyway. Batteries will likely get lighter and cheaper so why not add it to all their models.
Max_Torque said:
turbobloke said:
That was acknowledged earlier "the electric motor itself can be 90% efficient at peak but falls to 70% or below at low speed and there are other losses" but as per the post with that extract, there's more to it than that.
Again, efficiency is a somewhat misleading value.At idle, the engine in your car is 0% efficient. The fuel it burns just keeps it spinning round (typically 40Nm @ 650rpm = 2.7kW (the same power required to push a typical family sized car to around 40kph!)).
An electric motor doesn't idle. It stops, drawing practically zero power (the power electronics will be powered but not switching, consuming about 50w).
Efficiency is a key consideration, it's only seen as misleading if people (not you) don't understand it.
caelite said:
I wont be touching them with a 10ft pole until battery tech improves big time. The 1st gen prius's are all but useless nowadays with the old batteries not functioning or being able to hold a charge. They are also costing a fortune (1.5-2k) to replace. Not to mention the production methods for producing large chemical batteries is not sustainable and trashes local enviroments, not that the western market has ever had a problem with that.
To add to that again using prius's as an example the battery tech is designed to not be user or small garage servicable. Ive heard twice people getting battery errors which have merited a "battery replacement" at a dealer, which however was a somewhat easy fix as all that was causing it was some of the electrical contacts becoming eroded. It all brings up the same OBD error though and requires someone with a background in electrical engineering to service.
First gen (2years of production) needs to be replaced. All others can be replaced or defurbed fron about £500 fitted.To add to that again using prius's as an example the battery tech is designed to not be user or small garage servicable. Ive heard twice people getting battery errors which have merited a "battery replacement" at a dealer, which however was a somewhat easy fix as all that was causing it was some of the electrical contacts becoming eroded. It all brings up the same OBD error though and requires someone with a background in electrical engineering to service.
As a comparison my 2002 mondeo needed a clutch replacing recently. Ford quoted me over £1000. Then the fuel pump died, that was £300 to supply, and £100 for a local garage to fit. Then the gearbox went. Thats when I stopped pouring money into the car.
Prius seem to be very reliable. I've asked a cew taxi drivers why thay use them and none have mentioned economy or green reasons.
Edited by 98elise on Monday 31st August 13:23
turbobloke said:
Max_Torque said:
turbobloke said:
That was acknowledged earlier "the electric motor itself can be 90% efficient at peak but falls to 70% or below at low speed and there are other losses" but as per the post with that extract, there's more to it than that.
Again, efficiency is a somewhat misleading value.At idle, the engine in your car is 0% efficient. The fuel it burns just keeps it spinning round (typically 40Nm @ 650rpm = 2.7kW (the same power required to push a typical family sized car to around 40kph!)).
An electric motor doesn't idle. It stops, drawing practically zero power (the power electronics will be powered but not switching, consuming about 50w).
Efficiency is a key consideration, it's only seen as misleading if people (not you) don't understand it.
My point is really that it is the wide spread of high efficiency that makes an electric traction system so good in the real world.
I think it's irrefutable that from the point of the energy being in the vehicle (either by full charge or full tank of gas), a BEVis a more efficient proposition.
And with it, a better vehicle too - the simplicity of getting good NVH is orders of magnitude greater than an ICE. And the chances of getting mechanical issues also tend towards zero as there just aren't any where near the loaded components to fail. And the performance potential! 1000BHP will be a very easy goal for an EV supercar...sports car even.
The issue of if they are more efficient as a life-time proposition is open to opinion and to be honest, I haven't read enough papers on the subject but after driving multiple hybrids and EVs, they are brilliant for every day work.
And with it, a better vehicle too - the simplicity of getting good NVH is orders of magnitude greater than an ICE. And the chances of getting mechanical issues also tend towards zero as there just aren't any where near the loaded components to fail. And the performance potential! 1000BHP will be a very easy goal for an EV supercar...sports car even.
The issue of if they are more efficient as a life-time proposition is open to opinion and to be honest, I haven't read enough papers on the subject but after driving multiple hybrids and EVs, they are brilliant for every day work.
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