It's Electric, sort of

[Marty McSly]

I don't think that an electric drivetrain is all that much different from any other. It still has a transmission, differential, CV joints, etc. so why do you think that the traditional car would have so much more loss?

Depends whether it's hybrid or full electric. A hybrid with an electric motor yoked to the ICE still has the full drivetrain.

A fully electric car however would generally have electric wheel motors, connected to the battery by cables, so would require no transmission, differential, CV joints, etc.

 

[skibob]

Depends whether it's hybrid or full electric. A hybrid with an electric motor yoked to the ICE still has the full drivetrain.

A fully electric car however would generally have electric wheel motors, connected to the battery by cables, so would require no transmission, differential, CV joints, etc.

Exactly. As for typical efficiency numbers, google will reveal the same numbers for efficiency that I used. I know them from classes and various projects, but I googled them to make sure my memory wasn't lying to me.

 

[cantunamunch]

Electric loses virtually none. So, if you take a diesel generator--its a little more efficient at converting fuel to energy than a gas engine, but lets ignore that. The alternator it turns to generate electricity is 94-96% efficient..

The alternator runs in steady torque state. Don't forget that torque is proportional to rotor slip, i.e. misalignment. The more torque you demand the lower the efficiency. Expect EV drive motors to dip well into the 80s- especially if they are run without clutches or torque converters.

Electric power is conventionally generated using turbines which are completely adapted for waste heat recovery. That, gas capture at the flue, and clear generation upgrade path without need to change rolling stock is what is really being gained with EVs.

 

[TexasStout]

In addition to what others have posted, you are missing something else. An ICE powertrain loses a great deal of energy getting power to the wheels. About 40%. I am ignoring the inefficiency with which any ICE converts fuel into power. This is just power lost getting energy to the road.

Electric loses virtually none. So, if you take a diesel generator--its a little more efficient at converting fuel to energy than a gas engine, but lets ignore that. The alternator it turns to generate electricity is 94-96% efficient.

So, using a diesel generator to charge an EV may not be nearly as efficient as , say using solar panels to charge an EV. But its still a lot more efficient than driving an ICE vehicle.

EVs are not without hidden costs (as @chilehed mentions). But their most important feature (IMHO) is not the lack of tailpipe. Its the efficiency. Oh, and they are a helluva lot of fun to drive.

I think the energy loss % you're attributing to ICE vehicles is on the high end of the spectrum. I believe the range is more like 15%-40+%. There are many variables between models based on transmission and driveline design which affect efficiency. AWD, obviously has more drive components and are typically less efficient than a FWD where there is a direct line and shorter driveshaft.

 

[skibob]

The alternator runs in steady torque state. Don't forget that torque is proportional to rotor slip, i.e. misalignment. The more torque you demand the lower the efficiency. Expect EV drive motors to dip well into the 80s- especially if they are run without clutches or torque converters.

Electric power is conventionally generated using turbines which are completely adapted for waste heat recovery. That, gas capture at the flue, and clear generation upgrade path without need to change rolling stock is what is really being gained with EVs.

I am assuming the engineers who designed the generators have taken that into consideration and sized the alternator to the peak torque of the diesel accordingly.

I don't believe anybody is running clutchless motors on production EV? Could be wrong. I know they still haven't optimized the way they are used for anti-slip acceleration. My 160hp Volt will rip the tread off the tires if you punch it to the floor from a dead stop. Its one of my few complaints about the car. But after a few hundred miles, you get used to it and treat the gas pedal appropriately w/o thinking about it.

 

[skibob]

I think the energy loss % you're attributing to ICE vehicles is on the high end of the spectrum. I believe the range is more like 15%-40+%. There are many variables between models based on transmission and driveline design which affect efficiency. AWD, obviously has more drive components and are typically less efficient than a FWD where there is a direct line and shorter driveshaft.

I may be overattributing the energy loss to drivetrain and underattributing the energy loss due to conversion (ie, combustion) by a little.

This source suggests upper 60s percentile efficiency after you get past the conversion of fossil fuel to energy.

http://www.scuolacascia.it/attivita...tion/consumer_tips/vehicle_energy_losses.html

But if an ICE vehicle with a commercial drivetrain has gotten anywhere near 85% I'd be very surprised.

 

[Eleeski]

In addition to what others have posted, you are missing something else. An ICE powertrain loses a great deal of energy getting power to the wheels. About 40%. I am ignoring the inefficiency with which any ICE converts fuel into power. This is just power lost getting energy to the road.

Electric loses virtually none. So, if you take a diesel generator--its a little more efficient at converting fuel to energy than a gas engine, but lets ignore that. The alternator it turns to generate electricity is 94-96% efficient.

So, using a diesel generator to charge an EV may not be nearly as efficient as , say using solar panels to charge an EV. But its still a lot more efficient than driving an ICE vehicle.

EVs are not without hidden costs (as @chilehed mentions). But their most important feature (IMHO) is not the lack of tailpipe. Its the efficiency. Oh, and they are a helluva lot of fun to drive.

I'm not sure your numbers are even close or I missed what you are saying.

Drivetrain efficiency losses in cars range from 6 to 15 %. Auto makers are pretty good at getting the engine HP to the wheels. Electric engine losses are similar - maybe slightly better. There is no magic in electric drive.

ICE engines are around 40% efficient at converting the fuel energy to usable power. Diesel engines are slightly better, turbines are slightly worse. Utility scale generation is slightly better except coal struggles to get 40% efficiency. No real magic exists converting fuel to energy.

Even the magic of solar cells is not perfect. It takes several years of operation just to generate the power needed to manufacture the solar cells.

Hydroelectric might be magic. But good luck siting a new dam. Or even keeping all the producing dams we already have.

The extra weight and environmental consequences of fancy batteries offset the magic of electric cars somewhat. They are still pretty cool with lots of potential in a very young technology.

Large scale advantages in generation and distribution make electricity much less expensive. There's the magic in electric cars. Unless you have a stand alone diesel generator charging station.

From an energy efficiency standpoint, having a diesel generator to charge your Tesla is absurd. Being able to drive your Tesla to remote locations is magic. It makes good press against electric cars but is brilliant if you want more utility from your electric cars.

Eric

Working on a bolt on electric motor system for my custom Ford Focus truck. Not going for efficiency, just trying to get 4wd to get past chain control!

 

[skibob]

I'm not sure your numbers are even close or I missed what you are saying.

Drivetrain efficiency losses in cars range from 6 to 15 %. Auto makers are pretty good at getting the engine HP to the wheels. Electric engine losses are similar - maybe slightly better. There is no magic in electric drive.

ICE engines are around 40% efficient at converting the fuel energy to usable power. Diesel engines are slightly better, turbines are slightly worse. Utility scale generation is slightly better except coal struggles to get 40% efficiency. No real magic exists converting fuel to energy.

Even the magic of solar cells is not perfect. It takes several years of operation just to generate the power needed to manufacture the solar cells.

Hydroelectric might be magic. But good luck siting a new dam. Or even keeping all the producing dams we already have.

The extra weight and environmental consequences of fancy batteries offset the magic of electric cars somewhat. They are still pretty cool with lots of potential in a very young technology.

Large scale advantages in generation and distribution make electricity much less expensive. There's the magic in electric cars. Unless you have a stand alone diesel generator charging station.

From an energy efficiency standpoint, having a diesel generator to charge your Tesla is absurd. Being able to drive your Tesla to remote locations is magic. It makes good press against electric cars but is brilliant if you want more utility from your electric cars.

Eric

Working on a bolt on electric motor system for my custom Ford Focus truck. Not going for efficiency, just trying to get 4wd to get past chain control!

You are bringing a lot of things beyond efficiency into the equation, so I am going to ignore those.

As for your efficiency numbers, I've backed mine up with evidence. So I am going to stick with those.

 

[James]

If electric cars were 100% efficient, why are the batteries so hot they burst into flames without cooling? Or are we not counting that?

It's pretty moot anyway. No one here heats their house with electricity because it's so "efficient".

The bigger question is why are IC engines stuck in the efficiencies we have? A lot of it could be people subsidize power over energy efficiency because we like that, and gad is relatively cheap. Who would buy a 65hp car these days? Yet millions of bugs were sold.

Now, if we could get 100mpg out of that I think it would sell. In Europe anyway where they're paying roughly $6/gallon.

 

[tball]

My understanding is drivetrain losses are around 10-15% for 2WD and 20-25% for 4WD.


An electric motor can be directly connected to the wheels so it can eliminate drivetrain losses, depending on the vehicle design.

Getting into the energy loss generating power by an ICE vs electric power generation (and transmission) is a whole different deal. Which is the contention about?

 

[Eleeski]

@skibob I definitely don't get your point. Focusing on theoretical maximum electric engine efficiency is a long way from the real world factors that I'm considering.

Google "auto drivetrain efficiency" to get the 6 to 15% number I used. Your 40% number is closer to the fuel extraction efficiency, not drivetrain losses that an 85 to 95% efficient electric would help with.

I worked on a variable transmission design decades ago. We were losing a couple percent to friction and that small loss killed the idea. There's only tiny losses now.

Google "coal plant efficiency" to see that 40% is good for a coal plant. Thermodynamics limit heat cycle efficiency to around 50% with conventional turbine generators (exotic designs may be possible but they aren't adding much to the grid).

Slow charging is around 85% efficient. Fast charge is less efficient. Makes drivetrain losses look good.

There are a lot of good reasons to get an electric car. But electric cars are not the easy answer to all transportation issues. Real solutions will be marginal and incremental. The 90% vs 40% have all been explored. We have an excellent transportation system that is getting better.

The diesel fast charger is an important part of electric vehicle utility - even if it's efficiency is low. That charging station is the title focus of this thread.

Eric

 

[skibob]

@skibob I definitely don't get your point. Focusing on theoretical maximum electric engine efficiency is a long way from the real world factors that I'm considering.

Google "auto drivetrain efficiency" to get the 6 to 15% number I used. Your 40% number is closer to the fuel extraction efficiency, not drivetrain losses that an 85 to 95% efficient electric would help with.

I worked on a variable transmission design decades ago. We were losing a couple percent to friction and that small loss killed the idea. There's only tiny losses now.

Google "coal plant efficiency" to see that 40% is good for a coal plant. Thermodynamics limit heat cycle efficiency to around 50% with conventional turbine generators (exotic designs may be possible but they aren't adding much to the grid).

Slow charging is around 85% efficient. Fast charge is less efficient. Makes drivetrain losses look good.

There are a lot of good reasons to get an electric car. But electric cars are not the easy answer to all transportation issues. Real solutions will be marginal and incremental. The 90% vs 40% have all been explored. We have an excellent transportation system that is getting better.

The diesel fast charger is an important part of electric vehicle utility - even if it's efficiency is low. That charging station is the title focus of this thread.

Eric

Yes, the diesel charging station is the focus. this is why I keep ignoring the conversion of fuel to other forms of energy so that I am only comparing system efficiency. So, I'm still going to ignore that part of your argument.

As for the efficiency with which ICE vehicles transmit the power generated by the motor to the ground in order to move the vehicle: I could provide further sources all day, but I think I would be wasting my time. I never said that they are "the easy answer to all transportation issues". I said they are significantly more efficient at transmitting their energy resource to the ground. Which they are.

BTW, if you really want to want to compare apples to oranges, you should throw regenerative braking into the mix. Depending on design and effective use, and driving conditions this can recapture as little as 10% and as much as 40% of the energy spent.

There are a lot of things that should temper enthusiasm about EV's. A LOT of development remains to be done to get them to point in realizing their potential that ICE vehicles are today. But they are a definitive step in the right direction and a clear improvement over ICE for many (not all, at least not yet) applications.

BTW, my #1 reason for driving an EV continues to be that they are really bloody awesome fun to drive. My #2 reason is they are considerably cheaper to operate. I really don't have any other reasons. If they are good for the environment (and they are a modest improvement over ICE) then that's great. But it wouldn't make me buy one if #1 and #2 were not true.

 

[Eleeski]

@skibob You have something screwed up.

Electric cars cost about half as much to fuel as gas cars. Most of that is from electricity being cheaper than gasoline. Electric cars are twice as good as gas cars - no more than that.

If drivetrains are 40% efficient and ICE engines are 40% efficient then electric cars would be 5 times cheaper to fuel than gas cars - if electricity and fuel cost the same (which they don't). Well, that's just not true. So you have something confused. Touting the virtues of something worthwhile on flawed reasoning really doesn't help.

Your #1 and #2 reasons for your electric car are valid.

If every car was charged by a diesel generator, electric cars would be an environmental disaster. And more expensive to operate. That's not the real world so electric car ownership is still OK. More OK because charging is possible on those rare occasions when it's needed in locations off the grid. The occasional expensive and dirty charges don't offset the overall value of the EV. Unless you are only driving in the outback...

Sorry if I seem harsh. I haven't seen ANY data that supports your efficiency difference claim. EVs don't need bad science to validate their worth.

Eric

 

[skibob]

@skibob You have something screwed up.

Electric cars cost about half as much to fuel as gas cars. Most of that is from electricity being cheaper than gasoline. Electric cars are twice as good as gas cars - no more than that.

If drivetrains are 40% efficient and ICE engines are 40% efficient then electric cars would be 5 times cheaper to fuel than gas cars - if electricity and fuel cost the same (which they don't). Well, that's just not true. So you have something confused. Touting the virtues of something worthwhile on flawed reasoning really doesn't help.

Your #1 and #2 reasons for your electric car are valid.

If every car was charged by a diesel generator, electric cars would be an environmental disaster. And more expensive to operate. That's not the real world so electric car ownership is still OK. More OK because charging is possible on those rare occasions when it's needed in locations off the grid. The occasional expensive and dirty charges don't offset the overall value of the EV. Unless you are only driving in the outback...

Sorry if I seem harsh. I haven't seen ANY data that supports your efficiency difference claim. EVs don't need bad science to validate their worth.

Eric

I think its time to agree to disagree in regard to relative efficiencies. I've linked to my evidence. I can't go beyond that.

I will add that I've calculated the cost/mile to operate my EV at below 2 cents per mile. That is optimal I must admit: I charge at home late at night on a preferential reduced EV rate. I also don't drive on the highway very often and I live in a very mild climate.

Those last two are problems that need to be worked out still (along with lousy traction control and heavy, expensive, short lived batteries). I think HWY travel will eventually result in simple 2 speed gearboxes or perhaps a secondary (higher geared) motor that kicks in at hwy speed. Or something I can't yet imagine. I think the cold weather issue will ultimately be solved by the battery problem--smaller, higher capacity, longer lasting batteries which are badly needed are already on the horizon. There is also the likelihood that simple, economical ways of generating electricity onboard will develop and negate most of the battery issue altogether. These technologies are already starting to develop (in scales not currently fit for automobiles) and there is always the possibility that fuel cells will make a leap. Although on that last one, I know an engineer that has worked on developing them for nearly 30 years, and he believes they are a dead end technology.

When you combine these things with regenerative braking, dramatically reduced maintenance and manufacturing cost, and the fact that EV technology is still in its infancy, it makes, imho, a compelling way forward for most applications (over time). If EV's advance as much in the next 50 years as ICE has in the last 50, that will be amazing. Moore's law says it shouldn't take that long, if in fact Moore's law can be applied here.

 

[tball]

Moore's law says it shouldn't take that long, if in fact Moore's law can be applied here.

Unfortunately, no dice on Moores law and battery technology:
https://blogs.scientificamerican.co...on/moores-law-and-battery-technology-no-dice/

It's going to be a very long time, if ever, that an EV makes sense for a ski road trip around the mountain time zone. Hybrid, yes. EV, unlikely.

 

[skibob]

Unfortunately, no dice on Moores law and battery technology:
https://blogs.scientificamerican.co...on/moores-law-and-battery-technology-no-dice/

It's going to be a very long time, if ever, that an EV makes sense for a ski road trip around the mountain time zone. Hybrid, yes. EV, unlikely.

I have my doubts that Moore's law is even relevant to computing anymore. But I don't agree with your conclusion. Solid state batteries appear to be 5-10 years out. Even if nobody thinks of a better way to heat a car between now and then, the extra capacity will make up for it. Even now, Norway is the #1 market for EVs.

But a techology platform already exists that would be better than a Hybrid for skiing trips (if anybody would put it in an appropriate vehicle). The Chevy Volt and BMW i3 employee it. An EV that carries an onboard generator. (no, this is not a hybrid--quite different in fact) It still gets about 20% better fuel mileage than an ICE vehicle and has most of the EVs benefits (low-maintenance drivetrain, fun, instant acceleration). Manufacturers are moving away from it unfortunately because they want to ditch the complexity of ICE altogether if they are going to get into EV development. But I think it is a great bridge technology if anybody would commit to it.

 

[cantunamunch]

But a techology platform already exists that would be better than a Hybrid for skiing trips (if anybody would put it in an appropriate vehicle). The Chevy Volt and BMW i3 employee it. An EV that carries an onboard generator. (no, this is not a hybrid--quite different in fact) It still gets about 20% better fuel mileage than an ICE vehicle and has most of the EVs benefits (low-maintenance drivetrain, fun, instant acceleration). Manufacturers are moving away from it unfortunately because they want to ditch the complexity of ICE altogether if they are going to get into EV development. But I think it is a great bridge technology if anybody would commit to it.

We should totally have EVs with micro-turbines.

 

[James]

Running on hydrogen?

 

[cantunamunch]

Running on hydrogen?

No: hydrogen is a beeyotch to store, has extremely low energy density, and the primary/portable generation path is from methane.

Running on currently practical fuels with actual energy density. Think of it as an APU for the 4wheeled plane.

 

[skibob]

We should totally have EVs with micro-turbines.

Still has some problems to solve (some of which are public relations) but supposedly Land Rover/Jaguar are working on it.