Electromotive Vehicles... 5

[gknerr]

I am not an automotive engineer by any stretch of the imagination, but I have a business idea and I would like an engineer, in the industry, with whom to bounce the idea...
I am smart enough to know there is a hell of a lot I don't know, so please forgive the naivety.
Current electric/hybrid vehicles rely heavily on a heavy battery system to store energy, correct? What would the possibility be in this: A current ICE automobile retro-fitted with an "electromotive" propulsion. In my head the idea entails removal of the complete drive train, engine, etc. And replaced with an electric motor powered by a much smaller high-efficiency ICE engine. The electric motor powers 2-4 electric drive motors (in or near the wheels) and the car's electrical systems.

I know there are A LOT of variables here, but the concept is: NO BATTERIES (except as required to start the car, of course), power similar to today's ICE cars, the comfort and luxury of today's cars, and "mpg's" in the range of 50 - 100 miles.

I know this is probably a stupid idea, lets hope one of you can confirm this for me and I can stop trying to build this potential business idea... because if it worked - it would be very successful. Thank you, one and all, for your input.

 

[GregLocock]

Basically you are proposing an electrical transmission for an ICE car. They work, but don't really give much of an efficiency boost compared with a standard transmission.

For example a GM Volt gets around 50 mpg in charge sustaining mode (which is effectively an electric transmission plus a large battery), as against a GM Cruze which probably gets around 40 mpg(conventional trans). The Volt still has the substantial benefit of a battery, allowing stop/start and eliminating the need to run the engine at very low power where it is less efficient.

I haven't seen any studies that suggest that your proposed architecture really has any advantages.

Cheers

Greg Locock


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[gknerr]

Thanks for the response!!!
If I understand your response correctly, you are referring to a transmission transferring power to the wheels, yes? What could be said about putting drive motors directly at the wheel similar to the "Hi-Pa" in wheel motor? Removing the necessity for a transmission altogether.

Again, thanks for humoring me and I agree I haven't been able to find any kind of work or study on this concept.

Gary Knerr

 

[BrianPetersen]

There isn't an appreciable advantage in efficiency, with having the motors in the hubs as opposed to having them in a fixed location with halfshafts and CV joints. There isn't much power loss through the halfshafts. Putting the motors in the hubs makes them share space with the conventional brakes (which you still need!), spindles, ball joints, etc. and adds a bunch of unsprung weight. Can it be done, YES, but in most applications there's no benefit or not much benefit.

What you are proposing is essentially an "electric CVT". It will have lower efficiency than a conventional gear-to-gear transmission because of the multiple energy conversions. Yeah, you can match engine RPM to exactly match the load, but so can mechanical CVT's and they don't have fantastic fuel consumption.

The real benefit with the hybrid powertrains is the ability to shut the combustion engine down completely when there is low power demand, and to some extent the ability to use regenerative braking. Assuming we are talking about an electric powertrain here, you need batteries in order to be able to do that. In straight highway driving, where hybrid systems can't use regen braking nor engine shutdown, the hybridization provides no direct benefits ... except for the ability to downsize the engine while maintaining acceleration using the electric powertrain, and you still need those pesky batteries in order to be able to do that.

 

[gknerr]

Great Stuff, thank you very much. This helps reel my ideas back to down to more solid ground. Thanks!

Gary Knerr

 

[tbuelna]

gknerr,

There's nothing wrong with asking questions about something you don't understand.

First, the hybrid drivetrain you describe has been used on locomotives and some ships for many years. That is a diesel-electric generator powering an AC traction motor at each axle or propellor.

http://en.wikipedia.org/wiki/Diesel-electric_transmission

It is not really suitable for most automotive applications for many reasons. The chief reason is production cost- an electrical drivetrain costs much more than a mechanical transmission. But it also has to do with the way most cars are driven (as GregLocock points out). With locomotives and large ships that operate at fairly constant speeds and loads it can work well. But with automobiles that operate at various speeds and loads it doesn't really help with fuel economy.

Good luck and hang onto your money!
Terry

 

[patprimmer]

From a book titled

Timeless Machines
By Pedr Davis
isbn 0-947079-16-5

A colour plate contains 4 photos of a mostly restored Lohner-Porsche.

It is FWD, has a Mercedes IC engine which drives a generator and has an electric hub motor in each wheel.

The caption says

"This exceedingly rare Lhoner-Porsche has a Mercedes engine driving a generator feeding power directly to electric motors in the front wheel hubs It was successfully raced in 1901 by Ferdinand Porsche who also built a four wheel drive version. These shots were taken during a rebuild in New Zealand by Wallace McNair on behalf of Gerhard von Raffay, a German Porsch dealer."

Sorry, but not such a new idea.

Regards
Pat
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[pontiacjack]

How about if I "hijack" this thread to ask a related question?

Although I'm retired from a career in electronics, I was surprised to learn about the development of "super capacitors" and their use in large materials-handling equipment (e.g., Caterpillar D12E I think?), reducing the battery-size requirements considerably. Yet I've heard no talk of applying super capacitors to passenger vehicle storage of electrical energy. Why not?

 

[GregLocock]

Supercaps have very low energy density, and very high power density. Their main use is for smoothing the peaks of current that you get into and out of a battery, increasing the efficiency and life of the battery, so allowing a smaller battery to handle bigger surge currents.

What you'll see is hybrid battery/supercap powerpacks, rather than a large bank of supercaps instead of a battery.

Lots of people are working on this stuff, I sail with one of them. FWIW in our solar car we had supercaps for the above reason in 1996.





Cheers

Greg Locock


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[ivymike]

From Cat.com

http://safety.cat.com/cda/files/2086599/7/D7e FAQS.pdf

Is the D7E a “hybrid” machine? The D7E has an advanced Electric Drive power train that is designed specifically to meet demanding dozer applications, while enabling significant improvements in productivity, efficiency and sustainability. It can be considered a hybrid in that it combines a diesel engine with an electric generator to provide propulsion. However, unlike automotive hybrids, it does not use a battery or capacitor to collect, store or release energy during operation. The D7E does capture mechanical energy in the flywheel that is generated during braking, providing more efficient directional shifts and contributing to the overall efficiency of the machine. This technology is often referred to as a diesel-electric hybrid power train.

 

[LionelHutz]

A diesel-electric powertrain had the added capability of providing electric power for the humans riding on the trains or ships.

Throwing a bunch of electronics into a vehicle does not equate a higher mileage. That vehicle still needs to be accelerated and decelerated and it's power plant also has to have enough power to cruise down the highway to overcome the drag losses while providing power for the various equipment in the vehicle.

Your proposal doesn't make much sense because you are proposing a vehicle which has everything a typical hybrid has except for the batteries. A hybrid has the advantage that the ICE only has to produce the "average" power required, while the batteries are used as a buffer/storage to supply the peak power required. In such a hybrid, you could run the ICE at a constant power output to charge batteries or have it off. In the vehicle you propose, the ICE has to still be run to match the vehicle load.

One thing I do find odd is that, at least in North America, there seem to be no "bare bones" hybrid vehicles. Even the flagship of hybrids Prius now comes with extra baggage like the parking assist and most seem to have lots of extra accessories. In other words, where is the equivalent hybrid version of a Smart car?

 

[ivymike]

One thing I do find odd is that, at least in North America, there seem to be no "bare bones" hybrid vehicles.

it doesn't seem odd to me. If people pay for a compact car that costs 33% more than its closest cousin, they want to see some premium-level options in it. (sound, nav, etc)

 

[LionelHutz]

Ya, I guess it's smoke and mirrors or maybe poser enviromentalists, but spending extra to buy a hybrid which is worse for the enviroment from is it called dust to dust than the normal counterpart just doesn't seem to be very green to me.