My new car can go 410 miles on the energy of one gallon of petrol; unmodified!

[RedDevil]

Originally Posted by Vman455

This thing has a CD probably <0.10, is as large as a coffin, and races at a blistering 25 km/h. When you scale that up to something that seats 4 and isn't the size of a matchbox, has a significantly higher CD and frontal area, and drives on the highway...400 MPGe is a tough goal to meet. Even the VW XL1 was less than 300 MPGe running on electricity. (Keep in mind that power required to overcome aerodynamic drag increases with the cube of velocity).

The Lightyear is an even more extreme design than the XL1, with hub motors and no engine. So yes, I do believe they can make a car that only uses 75% of the energy an XL1 needs.

Let's do the scaling on that thing though. Make it 3 times as big, it then has 9 times the drag - and it would be longer than the Lightyear 1.
Move it 4 times as fast for 100 km/h; the air resistance would increase 16 fold but friction, drive train losses and rolling resistance would not, so averaging that at 8 times more, multiply by the size factor and we have 72 times more energy to move the scaled up racer at 100 km/h.

That's only a fraction more than the 65 from my assumption, but we'd get there if we scale up by 2.8 times or drive at 94 km/h. That's faster than I usually drive anyway.

[oil pan 4]

Has any one made a hub motor for a car that can last as long as a set of tires?
Not very efficient if it has to have 4 hub motors every 10 to 50 thousand miles.

[MeteorGray]

Quote: "For the first half of 2019 Germany generated more electricity from wind and solar than from coal and nuclear, and Germany traditionally burns, or burned, a lot of coal."


This sounds misleading.

Perhaps it would be illuminating to see the whole spectrum of where German electricity is derived from.

I believe I read that Ms. Merkel has committed Germany to significantly increase its use of Russian natural gas in the future. Perhaps that why they are winding-down their nuclear and coal options.

[aerohead]

Originally Posted by Snax

The only way I see it possible to exceed 400 MPGe at this point requires absolutely ideal conditions, very slow speeds, and relying upon the solar panels for full production (which I doubt will ever happen).

Using the specs from their site, the panels provide a maximum of 1.27kW.

So lets just assume that this car can regularly actually sustain 200 MPGe, or 6-ish mi/kWh at 35 MPH. In one hour, the car would obviously travel 35 miles, consuming about 6kWh. Subtract full production of the panels to see about 4.7kWh pack expenditure. Flipping that back to mi/kWh, we get about 7.4. That is still well under 300 MPGe, or most roughly, just under 250 MPGe.

The only ways to get over 400 MPGe with those calcs in mind are to assume one or more things to be true:

1) This car sees significantly over 300 MPGe in typical driving,
2) They are lumping in potential power production from the panels while parked, or
3) It must be driven far slower.

But if we get to add in solar panel production, I am going to take credit for the 5 kW array on my home, the less than 100 miles I typically drive in a week, and always charging at home (when I'm not conducting flawed aerodynamic tests ). The numbers on that cross infinity in all but November and December here in the northern hemisphere.

years ago,I ran some numbers for a 1995 Honda Accord 4-door sedan,with Cd 0.12.At normal 3,100-lb,EPA test weight,normal Honda frontal projected area,and normal 1995-era tire technology,the car would get 100-mpg at 100-km/h.
As an EV,it would get 300-mpge equivalence.You'd be able to squeeze a family of five inside.I used data published by Honda R&D,derived from their series of 'Dream',World Solar Challenge racers,which included all the data for the Accord.
BamZipPow and I are trying to mimic this performance with our pickup trucks,pulling trailers.

[Vman455]

Originally Posted by RedDevil

The Lightyear is an even more extreme design than the XL1, with hub motors and no engine. So yes, I do believe they can make a car that only uses 75% of the energy an XL1 needs.

Let's do the scaling on that thing though. Make it 3 times as big, it then has 9 times the drag - and it would be longer than the Lightyear 1.
Move it 4 times as fast for 100 km/h; the air resistance would increase 16 fold but friction, drive train losses and rolling resistance would not, so averaging that at 8 times more, multiply by the size factor and we have 72 times more energy to move the scaled up racer at 100 km/h.

That's only a fraction more than the 65 from my assumption, but we'd get there if we scale up by 2.8 times or drive at 94 km/h. That's faster than I usually drive anyway.

-Scaling up the body will increase its mass, which will also increase its rolling resistance
-energy required correlates to the cube of velocity for aerodynamic drag force and linearly with velocity for rolling force, since energy is the integral of force. 71 times more drag force (since we're assuming constant rolling resistance between the TUfast and its scaled-up version, even though this would not be true in reality) means an order of magnitude more energy required to overcome that force.
-Then, add in that the Lightyear 1 has a drag coefficient twice that of the TUfast, and more mass (read: rolling resistance) for its size, especially if it's carrying 4 people.

[RedDevil]

Originally Posted by Vman455

-Scaling up the body will increase its mass, which will also increase its rolling resistance

Of course. But not 65 times as much, and not linear to weight. Bigger wheels, relatively less contact area in the moving parts does reduce friction.

Originally Posted by Vman455

-energy required correlates to the cube of velocity for aerodynamic drag force

NO!
We are talking energy efficiency here. To move an object twice as fast the drag quadruples (as it is squared) and the distance covered doubles (as it is linear with speed). So you need 8 times as much power, but you cover twice the distance, hence the economy only suffers to the square.

Call them liars or accept their claim expecting they know their math better than we do. I hinge on the latter.

[aerohead]

Originally Posted by RedDevil

Of course. But not 65 times as much, and not linear to weight. Bigger wheels, relatively less contact area in the moving parts does reduce friction.

NO!
We are talking energy efficiency here. To move an object twice as fast the drag quadruples (as it is squared) and the distance covered doubles (as it is linear with speed). So you need 8 times as much power, but you cover twice the distance, hence the economy only suffers to the square.

Call them liars or accept their claim expecting they know their math better than we do. I hinge on the latter.

*If they're comparing the two vehicles,side-by-side,at the same velocity,and if the R-R coefficient were the same,from the equations I've got,then the rolling resistance would vary arithmetrically (monotonically?) as a function of (mass)weight.For instance,a doubling of weight would see a doubling of power to overcome rolling resistance,at any given velocity,up to the standing-wave velocity.
*If the R-R coefficient is different (and the skinny tires/wheels could certainly do that!),then that must be accounted for.
*At the same velocity,the vehicle's aerodynamic power requirement,should only vary as a function of the percentage difference in drag-factor (CdA),from one car to the other.A doubling of the CdA would double the aero- power requirement.(we've already accounted for velocity-cubed/power function).

[redpoint5]

Wind and solar are growing, perhaps faster in Europe, but in the US, the real growth is natural gas.



As sendler is often pointing out, renewables aren't even keeping up with the growth in demand for electricity, let alone beginning to displace non-renewable generation. You've got to cover the growth before you can even begin to reduce total emissions.

[oil pan 4]

I'm good with waiting and finding out.
They have promised hub motors that don't exist and efficiency no one thinks is possible.
At this point I will be surprised if they build it at all.
I'm expecting a more pedestrian version that doesn't use hub motors and gets the equivalent of less than 300 mpg when a normal person drives it outside in the real world.
The 400mpge number will likely remain a parlor trick that can't be reproduced outside a controlled environment.

[NeilBlanchard]

The hub motors they used in the STELLA were over 98% efficient.