Breaking news! Chevy volt technically driven by gas engine!

[NeilBlanchard]

Hi,

Originally Posted by dcb

why not hook that 5hp motor to a 5th wheel and stick it in your tow hitch with a lever to raise/kill it or lower it?

The Edison2 VLC requires just 3.5HP to go 50mph on flat ground (830 pounds, Cd of 0.161 CdA of 2.96 sq ft), but I think you'd need a 10-15HP motor for most conventional cars. Those single cylinder engines are pretty poor efficiency. The VLC had a 34% (peak) efficient single 250cc and a high efficiency transmission, and it got 102MPGe Combined and >120MPGe at highway speeds (they burned E85 and the actual MPG was lower).

We'll see how the VLC EV goes sometime next year. Electric motors are >90% efficient. And plug-to-wheel good EV's are about 85% efficient.

Edit: Popular Mechanics drove the Volt 900 miles, and averaged 32-36MPG with the ICE running, and 37.5 mpg city and 38.15 mpg highway, when they included the EV miles:

http://www.popularmechanics.com/cars...ty-report-test

Fairly pitiful, I think.

[MN Driver]

Originally Posted by rmay635703

To achieve 50% efficiency you CAN NOT DO THAT, period!
Those motors are designed to work at ONE OUTPUT SPEED AND POWER VALUE.
Motors that vary output tend to all universally be below 30% efficiency, most being below 25% in real world. (and thats modern fuel injected, not a small gas engine).
[clipped from quote]
Thus a generator powering an electric motor decoupled so it could only run at its most efficient range could likely still operate about 65% more efficiently (even with losses) than a classic variable throttle motor running through some sort of gear reduction system.

Let's say this is planned out, One output speed, could be tied to a small range, say 60-65mph. One power level, we could fix the throttle to its most efficient point to provide this. Couldn't we?

This would be for a long ranger EV. I've thrown the thought around of having a 100 mile EV without any additional power sources but driving it to Madison, WI for the Green Drive Expo instead of trailering it behind a tow vehicle. I figure something like this 16HP 6500 watt genset 16 HP, 6500 Rated Watts/7000 Max Watts Portable Generator - EPA would be enough to stretch the range in the most aerodynamically efficient and lightweight vehicle possible to where if driven efficiently enough at a slightly slower speed than the rest of traffic that it would extend the range just enough to make it with a single extended break halfway through the trip. ...but if it could be geared to put the engine speed in its sweet spot and throttle adjusted to a fixed position to only provide the power level to the point of maximum fuel efficiency, could this work well? 16HP at say a 70-80% load connected to the ground is going to be much more powerful than trying to find the maximum the genset can continuously squeeze out comfortably(probably not the full rated 6500 for the full distance).

BTW, I am more electrically capable than mechanically capable so I probably wouldn't figure out how to connect the engine to the ground but more curious than anything. Mostly carrying the thought as a 'I'd try this' sort of one-off hobby try. I'd probably just connect the generator to an isolated amperage adjustable charger and work from there. If I really wanted to do this for a longer trip, I figure I'd need two of these generators (with two isolated chargers) to provide adequate power since one will leave someone in an empty battery hole after not too long of traveling down the highway.

[dcb]

yup, that would be the most efficient scenario, a relatively constant speed and load, engine sized and geared appropriately (or perhaps with multiple gears). The electric motor can pitch in if the optimum speed starts to drops off, or at slow speeds. Smart driver assumed.

[dcb]

note also in that link, the generator itself can receive 16hp from the engine, but puts out 6500 watts, that makes just the conversion of rotary motion to electrical power step 54% efficient and it hasn't even moved the car yet. I figure it is using 1.65 gph at peak hp. The engine could also drive a wheel at around 95% efficiency under the right conditions instead of making electricity. A smart driver can use that to great advantage.

[cfg83]

Neil -

Originally Posted by NeilBlanchard

...

Edit: Popular Mechanics drove the Volt 900 miles, and averaged 32-36MPG with the ICE running, and 37.5 mpg city and 38.15 mpg highway, when they included the EV miles:

Chevy Volt Reliability Report - 2011 Chevrolet Volt Long-Term Test Drive - Popular Mechanics

Fairly pitiful, I think.

Ouch, that's pretty bad. But I wish they had published a table for analysis. That led me to this :

2011 Chevrolet Volt Prototype Test Drive: Smooth-Driving EV Good Enough to Save GM? - Popular Mechanics - May 28, 2009

The Volt will achieve its 40-mile range while using only half the energy contained in its battery pack, or 8 kwh, the equivalent of the energy contained in about 1 quart of gasoline, which speaks to the efficiency of electric-drive technology. GM expects that competitive advantage in the electric-car arena will derive from a combination of battery technology and the control systems that manage the way in which batteries discharge, recharge and perform. GM has opted to produce its battery packs internally, using cells made in Korea by LG Chem. That company's U.S. subsidiary, Compact Power, won out in competition with A123 based largely on Compact Power's chemistry and safety technology.

That makes me happy because it matches my specu-calculation :



8.8 kWh = 0.24 Gallons => 4 quarts = 1 gallon.

CarloSW2

[NeilBlanchard]

Right, the BTU equivalent of a gallon of gasoline listed on Wikipedia is ~33.4kWh of electricity. The X-Prize spreadsheet uses 3,412BTU per kWh and 116,090 BTU per gallon of gasoline; so 34.02kWh/gallon.

[dcb]

I don't think there is consensus here on a straight kwh to mpg conversion. Which should be obvious when the actual test drive gets 37 mpg and you get 150mpg by "figguring" and GM advertises 230mpge.

There was no mention here of power lost during recharging either.

[rmay635703]

Originally Posted by dcb

note also in that link, the generator itself can receive 16hp from the engine, but puts out 6500 watts, that makes just the conversion of rotary motion to electrical power step 54% efficient and it hasn't even moved the car yet.

The conversion of rotary power to electrical power is NORMALLY much more efficient than that, what isn't is that 16hp motor. I would guess that the 16hp doesn't even make it to the shaft and the 16hp is probably never used (or possible to attain) because of the RPM the generator operates at is not at peak HP for the engine. There is much more to this than meets the eye. Yeah I get 16hp at 5000rpm but the genset operates at only 3600rpm. Also a small AC genset usually (not always) is less efficient than a comparable DC genset, I have a feeling the DC units are likely more expensive and likely made a little better.

Which is why a PROPER high efficiency single output turbine RUNNING a high efficiency DC genset would likely improve fuel economy rather than reduce it.
I simply cannot believe that a 40-50% eff. motor running a 90-96% eff genset is going to perform as poorly as a 17% eff. small gas engine running an 85% eff genset. And yes turbine engines show up all the time on the gov liquidation auctions, usually not very expensive either because they are stand alone without much usefullness.

Next

Originally Posted by MN Driver

Let's say this is planned out, One output speed, could be tied to a small range, say 60-65mph. One power level, we could fix the throttle to its most efficient point to provide this. Couldn't we?

This would be for a long ranger EV. I've thrown the thought around of having a 100 mile EV without any additional power sources but driving it to Madison,

I cannot understand what everyone fascination with making a range EXTENDER into a steady state driving apparatus. My feel is that the genset should never be large enough to run the car. I want to extend my range in certain circumstances, not make it unlimited. Even if the genset can only output 1/3 of the power I need that increases the distance I can drive by 33% (50miles wan't uncommon for me,another third is 66miles) if I have a charge controller to maintain constant output (no overload)
Also a genset that can output a fraction of what is needed to run the car will still recharge the batteries when I am coasting, at stop signs or potentially in a parking lot, meaning I still likely can travel a good ways if required. Also a smaller genset is lighter and not going to significantly impact my range in of itself.

And in my case my car is 1200lbs and can't go faster than 55mph anyway, so the amount of power I would need is significantly less.

Cheers
Ryan

[dcb]

Originally Posted by rmay635703

...I cannot understand what everyone fascination with making a range EXTENDER into a steady state driving apparatus.

because that is logically the most efficient mode, even in parallel operation, and a good driver can take advantage of higher peak efficiency parallel provides. Aren't the efficient turboshaft engines like the size of a room?

[tjts1]

Originally Posted by cfg83

Neil -



Ouch, that's pretty bad. But I wish they had published a table for analysis. That led me to this :

2011 Chevrolet Volt Prototype Test Drive: Smooth-Driving EV Good Enough to Save GM? - Popular Mechanics - May 28, 2009

I guess they forgot about the plug.