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Old 08-05-2019, 02:52 PM   #31 (permalink)
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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.

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Last edited by Snax; 08-05-2019 at 03:01 PM.. Reason: (had to review my infinity claim multiple times . . )
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Old 08-05-2019, 05:44 PM   #32 (permalink)
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Don't forget it is designed by the team that built the Stella solar racer, which got maybe over 1000 MPGe at highway speeds - while seating 4 adults.
Extreme aerodynamics, very low (less than a meter IIRC), extreme light weight and bicycle-like tires did that.
While it does run around like a car the Stella is way too vulnerable to be practically viable.

The Lightyear is strong enough to be safe to drive, but it still has very narrow wheels, low height, low weight and low air resistance, so the power to move it is in a completely different league than other roadworthy EVs.

If they claim 400 MPGe then don't just assume they lie. Instead appreciate that an economy race winning team knows quite a lot about calculating MPGe.
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Old 08-05-2019, 05:51 PM   #33 (permalink)
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Quote:
Originally Posted by Snax View Post
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.
We laugh, but Toyota itself has engaged in such foolery. In 2014 they took a Plug-in Prius to the Nürburgring and then claimed to the media it had achieved 698 mpg because the gas engine only turned on for part of the 13-mile loop and the rest was run on battery power. That result is only possible if you don't count the electricity used at all.
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Old 08-06-2019, 05:42 PM   #34 (permalink)
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Quote:
Originally Posted by RedDevil View Post
Don't forget it is designed by the team that built the Stella solar racer . .

If they claim 400 MPGe then don't just assume they lie. Instead appreciate that an economy race winning team knows quite a lot about calculating MPGe.
I don't want to discount their efforts at all. I think they are trying to build a noteworthy car with considerable promise.

I think, as I illustrated however, that the math suggests a lack of credibility on the MPGe claim without fudging other factors. Nobody is going to get 400 MPGe out of one of these cars without that fudge factor (and I will happily admit being wrong if they do). Rolling resistance alone is likely to make that an exceptionally lofty goal.

I will suggest that the Lightyear could potentially be the most stellar production highway performer to ever hit the road. They have certainly devoted plenty of good design to that end.
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Old 08-07-2019, 03:38 AM   #35 (permalink)
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If you think 400 MPGe is out of the question...

https://inhabitat.com/worlds-most-ef...us-26135-mpge/

26.135 MPGe!
Okay, that is an extreme solar racer. But it should not be that hard to build something roadworthy if it is allowed to use 65 times as much power?
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Old 08-07-2019, 11:17 AM   #36 (permalink)
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Dont forget to include the inefficiencies of the coal powered station generating the electricity to run this car.
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Old 08-07-2019, 11:45 AM   #37 (permalink)
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Quote:
Originally Posted by Snax View Post
The best I could do with my i3 on a <40 mph 10 mile round trip to the store was 205.5 MPGe, or 6 mi/kWh.

Considering it is in the top 3 rated for city efficiency with the Ioniq pulling off some sort of magic and the significantly lighter iQ EV being the only ones ahead of it, I am skeptical real world claims will come in much over 200 for the car.

Even at 25 mph, the best I can get is scarcely over 9 mi/kWh or 300 MPGe.
My leaf is driven 75% on the highway.
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Old 08-07-2019, 11:47 AM   #38 (permalink)
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Quote:
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We laugh, but Toyota itself has engaged in such foolery. In 2014 they took a Plug-in Prius to the Nürburgring and then claimed to the media it had achieved 698 mpg because the gas engine only turned on for part of the 13-mile loop and the rest was run on battery power. That result is only possible if you don't count the electricity used at all.
They may be trying to not include the solar power in the overall mpg number and count it was free power.
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Old 08-07-2019, 09:49 PM   #39 (permalink)
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Quote:
Originally Posted by RedDevil View Post
But it should not be that hard to build something roadworthy if it is allowed to use 65 times as much power?


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).
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Old 08-09-2019, 03:17 AM   #40 (permalink)
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Quote:
Originally Posted by arcosine View Post
Dont forget to include the inefficiencies of the coal powered station generating the electricity to run this car.
Don't forget the inefficiencies of producing gasoline.

Coal is on its way out, wind and solar are growing.
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.

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