100 MPH and 100 MPGe

[aerostealth]

Here is a link to my new blog at EV World posted yesterday. Phil Knox helped me write it.

100 MPH and 100 MPG



This image is of the Aero and Rolling Resistance graph for the 1996 Honda Accord our blog article is based on. The math essentially converts the metrics on this graph to our hypothetical Cd 0.12 Chevy Bolt using the conversions outlined.

[Magajgfha]

How a Cd = 0.12 body form for a Chevy Bolt world result in a 186 MPGe Hwy vehicle that would still be capable of getting over 100 MPGe at 100 MPH with S rated tires and a electric overdrive.

The title is misleading as it's about MPGe and not MPG.

[sendler]

Parking your pick up truck in favor of any other vehicle would be a good step.
.
The Volkswagen XL1 made it to cd.189.
.
http://ecomodder.com/forum/showthrea...ery-25024.html
.

[aerohead]

Originally Posted by Magajgfha

The title is misleading as it's about MPGe and not MPG.

Since we're comparing apples and oranges we tried for simple metrics which consumers have been already given (excepting BSFC ).
Engineers work with Btus and all energy/power relationships can be related to Btus,making the transition between talking about BEVs and ICEs more transparent by the relationship to brake horsepower/road load,which all vehicles share.
The EPA has provided the MPGe already.We're just expanding upon it.
On a Btu-to-Btu basis,the LEAF and BOLT both share a 0.1397 lbs per bhp-hr BSFC.
If your ICE car's engine and drivetrain were as efficient as that of the Bolt's powerplant/powertrain ,you could expect 3-X mpg from what you experience today.
That's all we're saying.All the caveats are mentioned in the preamble to the guts of the article.

[aerohead]

Originally Posted by sendler

Parking your pick up truck in favor of any other vehicle would be a good step.
.
The Volkswagen XL1 made it to cd.189.
.
http://ecomodder.com/forum/showthrea...ery-25024.html
.

Aerostealth has been doing public outreach astronomy programs since the 1980s.The pickup helps with hauling large telescopes plus camping functions at the astronomy venues.He's very mindful of his carbon footprint with the truck and by February hopes to be driving on the solar electricity he produces at his home,parking the truck except for astronomy excursions.
We're interested in going beyond the XL1,aerodynamically.
Volkwagen's Hucho mentions that we can think about automobiles with Cd 0.08.We're being conservative.

[Magajgfha]

Originally Posted by aerohead

If your ICE car's engine and drivetrain were as efficient as that of the Bolt's powerplant/powertrain ,you could expect 3-X mpg from what you experience today.

And that's exactly why I find the title misleading.

[aerohead]

Originally Posted by Magajgfha

And that's exactly why I find the title misleading.

*Mechanical engineering requires the study of thermodynamics.
*Within the study of thermo,engineers,or physicists are introduced to the 2nd Law of thermodynamics,which introduces the concept of 'Entropy'.
*Entropy has to do with how much work can you get out of a system,with respect to how much energy you're putting in.
*Understanding thermal and mechanical efficiency requires that you understand entropy.
*Allowing any high school student to graduate without a knowledge of Entropy is the greatest disservice a public educator could bestow upon a student.
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*If you take the amount of Btus in a gallon of gas (111,836,for Regular Unleaded,10% Ethanol ) this can easily be converted to Kilowatt/hours.
*Your gas tank capacity can be compared to a battery pack,or visa-versa.
*If you compare the range of a BEV,compared to the average ICE vehicle,all else being equal,on a Tank-to-wheels,or Battery-to-wheels Btu basis,you find that the electric powertrain will get you 3-times farther down the road,for an equivalent amount of 'fuel'.
*It's just straight engineering.No voodoo numbers manipulations.

[Magajgfha]

Originally Posted by aerohead

*Mechanical engineering requires the study of thermodynamics.
*Within the study of thermo,engineers,or physicists are introduced to the 2nd Law of thermodynamics,which introduces the concept of 'Entropy'.
*Entropy has to do with how much work can you get out of a system,with respect to how much energy you're putting in.
*Understanding thermal and mechanical efficiency requires that you understand entropy.
*Allowing any high school student to graduate without a knowledge of Entropy is the greatest disservice a public educator could bestow upon a student.
--------------------------------------------------------------------------
*If you take the amount of Btus in a gallon of gas (111,836,for Regular Unleaded,10% Ethanol ) this can easily be converted to Kilowatt/hours.
*Your gas tank capacity can be compared to a battery pack,or visa-versa.
*If you compare the range of a BEV,compared to the average ICE vehicle,all else being equal,on a Tank-to-wheels,or Battery-to-wheels Btu basis,you find that the electric powertrain will get you 3-times farther down the road,for an equivalent amount of 'fuel'.
*It's just straight engineering.No voodoo numbers manipulations.

I understand this. Reading the title, I thought I'd see some radical purpose-built or at least heavily modded vehicle, because that's what you need to get 100 MPG at 100 MPH. It was cool.
But then I saw a pamphlet on how electric is more efficient that ICE. Volt and Bolt? Not so cool.
Yes, they are more efficient (at least if you discount the efficiency of electricity generation, which varies a lot from one place to another).
Yes, it's worthwhile to write about it because there are some who don't know this important fact.
But the headline is wrong, MPG is not MPGe and the article doesn't deliver what it promises.

[aerostealth]

I believe you are wrong about your concerns, which were addressed in the article. For some reason you want to include electrical generating and transmission loses in your calculations but seem to have no similar concerns for the well to wheel cost for fossil fuels at all? Why is that?

In the article I pointed out that for cost analysis charging loses should be included but no more. For the efficiency of the drive train we did not include them anymore then you would factor in the energy cost for delivering the gasoline to the gas station. This is not the way to evaluate a engine from a thermodynamic point of view.

Better still with 5.1 KW of grid tie solar I would have no transmission loses if charging in the daytime. My export tariff is 8 cents per KWh so that would be my effective cost. The best GM could do was 100 MPG at 50 MPH with their 1992 Ultralight 2 cycle 3 cylinder engine. The 2017 Bolt can routinely pull over 100 MPGe at 62 MPH.

Energy in to work out electric engines are a real winner when compared to any IC Engine. The batteries has been the weak link up until recently. It looks like the technology is now poised to take off in the market place and the reason it is doing so are becoming readily apparent.

[Magajgfha]

Originally Posted by aerostealth

I believe you are wrong about your concerns, which were addressed in the article. For some reason you want to include electrical generating and transmission loses in your calculations but seem to have no similar concerns for the well to wheel cost for fossil fuels at all? Why is that?

In the article I pointed out that for cost analysis charging loses should be included but no more. For the efficiency of the drive train we did not include them anymore then you would factor in the energy cost for delivering the gasoline to the gas station. This is not the way to evaluate a engine from a thermodynamic point of view.

Better still with 5.1 KW of grid tie solar I would have no transmission loses if charging in the daytime. My export tariff is 8 cents per KWh so that would be my effective cost. The best GM could do was 100 MPG at 50 MPH with their 1992 Ultralight 2 cycle 3 cylinder engine. The 2017 Bolt can routinely pull over 100 MPGe at 62 MPH.

Energy in to work out electric engines are a real winner when compared to any IC Engine. The batteries has been the weak link up until recently. It looks like the technology is now poised to take off in the market place and the reason it is doing so are becoming readily apparent.

You're trying to invalidate my concerns based on a side remark. I did not factor-in several variables which are more or less important. Yes. There were some studies on the topic that were far more detailed than the basic fact that I noted (quick search: 1, 2) which show the difference to be far smaller than 3x.

But this is still a side note. MPG is used for ICE cars, MPGe for electric ones. By conflating the two you make the reader expect something you don't deliver and this is my main concern.