Let's be fair on the high-mileage EVs

[dcb]

Though I don't think anybody here is ignoring powerplant (aka heat engine) losses Jim, except as alternate bad comparison examples.

And I'm not convinced that the GREET model does either, do you have specifics?

[Coyote X]

How about we do it more like the EPA does it to some extent. Every type measures in whatever convenient form. MPG Miles/CuFT centiL/Km Miles/Kwh or whatever. And list cost per year, 15000 annual miles at the avg price of fuel used by the vehicle. And the total yearly estimated carbon footprint.

That would be about the only sane way to measure things. Still not a direct comparison but close enough to get the general idea.

[Ernie Rogers]

There are really two problems with the "heat value" of gasoline.

The first is that there are two different kinds of heat value (as some of you know). High heat value and low heat value. The difference is the form of the products after the reaction. If you start with the fuel and air at room temperature, and obtain the heat when the products end up at the same temperature, then you have the "high heat value." If you aknowledge that the products leave the engine as gases, you get the "low heat value." And, if you account for the exact temperature of the exhaust, then you can get an even lower "low heat value."

Dcb, your value of 124,000 BTU per gallon is a high heat value. (125,000 is quoted more often for this.) The others are low heat values--that's why this one value is so much different than the others.

The second problem is that there is no clear definition for what "gasoline" actually is. Every refinery makes a different product, subject to an ASTM or a API specification that insures the stuff will burn okay in a car.

Since the chemical compositions are different, the energy content can be a little different too. Sometimes people doing research will specify a particular gasoline formula to guarantee that their data can be reproduced. I have seen isooctane used for this "standard gasoline."

Ernie Rogers

Originally Posted by dcb

LOL, even that is not simple

From the wiki discussions on gasoline:
BTU per gallon of gasoline

• 1 kilowatt hour = 3,412.14163 BTU

But nobody seems to know how much energy is supposed to be in a gallon of gas.

• 1 Gallon = 124,000 Btu (rounded to nearest 1000)(based on U.S. consumption, 2007)DOE
• 1 Gallon = 115,000 Btu ORNL
• 1 Gallon = 114,100 Btu About.com
• 1 Gallon = 114,063 Btu NAFA.org
• 1 Gallon = 114,000 Btu EPA
• 1 Gallon = 110,400 Btu/gallon in California [www.vta.org/bart/documents/final_eir/vl_1_ch_4_08_energy.pdf VTA]

• 1 Gallon = 114,000 Btu/gallon according to NIST. They came up with the GGE concept in 1994.NIST

I will assume NIST's figure for 114,000 Btu per gallon of base gasoline is their standard, since they are the ones behind the GGE concept. EPA's figure agrees with this in most places. Kgrr (talk) 16:02, 1 January 2009 (UTC)
Even some government institutions cannot be internally consistent:

• 1 Gallon = 115,400 Btu/gallon ORNL

This figure seems to gain a lot of traction:

• 1 Gallon = 114,264 Btu/gallon AFDC
• 1 Gallon = 114,264 Btu/gallon Province of Alberta, Canada
• 1 Gallon = 114,264 Btu/gallon Chemistry course

[trebuchet03]

I continue to challenge Argonne for their GREET model which continues to deny the Second Law of Thermo, that is, they keep it in their model that electric energy is equivalent to heat energy, leading people to ignore the heat engine effect for conversion of heat to electric energy. This has to get fixed since they are a key national authority.

What unit of energy would you prefer using for comparing any type of energy?

Energy is energy... there may not be clear agreement on energy content... but it's still energy... thermal energy is energy.... electrical energy is energy.... chemical energy is energy.... radiant energy is energy... etc.

Now if radiant energy isn't the same as thermal energy... Well, I should just go burn my heat transfer books - it's got all sorts of stuff where radiant and thermal are simply added together using the same units!

The only difference... electrical, thermal and radiant are kinetic while chemical energy is potential. And hell, EV's have chemical energy storage just like an ICE powered car. Now when kinetic E stops having an equivalence to potential E (such as saying chemical energy != electric energy+...) - we can't even get to the second law of thermo because we've violated the first.

-----
It's not the physics... It's the metric

[Ernie Rogers]

Okay, folks, I found the table. To calculate greenhouse gases per mile, divide the number in the table by the mpg of the vehicle.

Example:

Gasoline car getting 50 mpg---

.... 11,800 / 50 = 236 gm CO2 per mile

Let's do an EV getting 250 wh /mile, or 4 miles per kWh---

.... 777 / 4 = 194 gm CO2 per mile

See note at bottom of the table about CO2 from electricity.

Ernie Rogers
------------------------

TABLE OF GHG PER FUEL UNIT

Gasoline...........11,800 gm CO2e /gallon gasoline
….Energy content: 116,090 BTU /gallon, or 34 kWh per gallon

Diesel #2..........12,700 gm CO2e /gallon diesel
....Energy equivalent: .0.90 gal = 1gal gasoline

Corn ethanol.......6,135 gm CO2e /gallon ethanol (from Wang)
....Energy equivalent: 1.52 gal = 1 gal gasoline

Electricity.............777 gm CO2e /kWh (U.S. power plant mix)
...or..................26,400 gm CO2e /gallon gasoline equivalent
....Energy equivalent: 34 kWh = 1 gal gasoline

Compressed NG...111.1 gm CO2e /SCF
....Energy equivalent: 118 SCF = 1 gal gasoline

H2 gas................34.2 gm CO2e /SCF
....Energy equivalent: 400 SCF = 1 gal gasoline

Biodiesel...........5940 gm CO2e /gallon biodiesel
....Energy equivalent: 1 gal = 1 gallon gasoline

CO2e refers to equivalent CO2 effect of all greenhouse gases combined, "Well-To-Wheels." All of these numbers come from Wang. The numbers for electricity assume that the electricity is from an "average" United States power grid.

-------------------------------

Originally Posted by Ernie Rogers

Argonne national lab (Wang and others, the GREET model) has published the conversion from units of fuel to grams of CO2, including all of the steps like refining and mining. With those factors all you have to do is multiply--

(fuel units /mile) x (gms CO2 /fuel unit) = gms CO2 / mile

And, the tables include gms CO2 /kWh under various assumptions.

The tables are available on line, and I have a table on my computer here somewhere. I will have to send it later when I get back. (Have to get to work now.)

Ernie Rogers

[dcb]

Originally Posted by Ernie Rogers

There are really two problems with the "heat value" of gasoline.

The first is that there are two different kinds of heat value (as some of you know). High heat value and low heat value. ... If you aknowledge that the products leave the engine as gases, you get the "low heat value."...

I have to say to this point that I've been assuming a simple bomb calorimeter type measurement of the BTU of gasoline. I am struggling to understand how using an intermediate value makes any sense though. If the engine (or powerplant) releases hot gasses (or even liquid that is slightly above room temperature) it is releasing energy that it might otherwise be using.

One doesn't get to apply a handicap because the discharge happens to be in gaseous state, I don't get that at all.

[dcb]

Originally Posted by Coyote X

How about we do it more like the EPA does it to some extent. Every type measures in whatever convenient form. MPG Miles/CuFT centiL/Km Miles/Kwh or whatever. And list cost per year, 15000 annual miles at the avg price of fuel used by the vehicle. And the total yearly estimated carbon footprint.

I'm starting to agree, even just having a separate kwh entry field as has been mentioned would probably be good (you should be able to note the mileage when adding fuel or kwh or both). Then the plug-in hybrid could track both electric and gas separately, and you could track your block heater separately from your tank.

So the kwh would be measured at the wall, and the gallons at the pump. But we still need a Conversion factor so you can subtract the kwh miles and not have 150mpg hybrid hummers in the garage.

[theunchosen]

the 150 mpg hummers are just dividing by gallons.

Fastest conversion is add BTUs of electricity, multiply gallons by BTU per gallon add the two and then divide miles by that.

[dcb]

What value do you use for "BTU per gallon"?

[theunchosen]

114,000

add electricity

divide by 114000 btus=gg +gge

miles/(gg+gge)

so long as you use the same number everywhere it won't affect it that badly.