ERD50
Give me a museum and I'll fill it. (Picasso) Give me a forum ...
Might have got caught in the updates, I started before dinner...
I'm sure your arithmetic is right, I'm so confident I'm not even going to double check it. The apparent discrepancy is in how the numbers are applied.
Yes electric motors are very efficient at taking energy from the battery and getting it to the wheels ( ~ 90%). The missing link in the above arithmetic is - electric motors don't run on propane!
So feed the propane to a gas turbine to run a generator to make the electricity, and you might get 30% out as electric energy. Then lose ~ 8% in transmission, and maybe 15% in charging the battery, and 90% motor eff. So the new arithmetic is:
assuming 2.8G of propane = 75 kWh,
[-]edit - messed up my math, will return....[/-] OK, 3nd try....
(75kWh ⋅ 0.3 ⋅ 0.92 ⋅ 0.85 ) ~ 17.6 kwH into battery
At 75 kWh and 310 miles per charge, we get 0.242 kw/mile
So 17.6 kwH into battery gets us ~ 72.7 miles on 2.8 G of propane, and that is ~ 26 mpg. Or about 52 mpg if you could count on using a Combined Cycle turbine ~ 60% efficiency. So probably in between, call it 39~40?
Best case for the Tesla is not too impressive compared to a modern hybrid, worst case, many cars blow the Tesla away in efficiency.
OK, we do need to account for refining and delivering gasoline to the gas station. IIRC, I've seen 6 kWh of energy (not electricity! much of comes from burning waste from the refining process itself). I'll see if I can find that number, but i it's 10% of the delivered BTU or kWh, just multiply the ICE/hybrid mpg by 0.9 - still good.
Not counting other losses in the EV, like standby, heat, AC, etc. Not sure those are included in the EPA range #'s. So that would even things up a bit anyhow.
And it looks like NW-Bound's arithmetic on propane kWh was correct - I knew it would be
-ERD50
I checked and checked my arithmetic, and the data on different Web sites on the energy density of propane. Yes, 75 kWh is equivalent to 2.80 gal of propane. Electric motors are very efficient. Too bad lithium batteries are still expensive, else they would solve a lot of problems..
I'm sure your arithmetic is right, I'm so confident I'm not even going to double check it. The apparent discrepancy is in how the numbers are applied.
Yes electric motors are very efficient at taking energy from the battery and getting it to the wheels ( ~ 90%). The missing link in the above arithmetic is - electric motors don't run on propane!
So feed the propane to a gas turbine to run a generator to make the electricity, and you might get 30% out as electric energy. Then lose ~ 8% in transmission, and maybe 15% in charging the battery, and 90% motor eff. So the new arithmetic is:
assuming 2.8G of propane = 75 kWh,
[-]edit - messed up my math, will return....[/-] OK, 3nd try....
(75kWh ⋅ 0.3 ⋅ 0.92 ⋅ 0.85 ) ~ 17.6 kwH into battery
At 75 kWh and 310 miles per charge, we get 0.242 kw/mile
So 17.6 kwH into battery gets us ~ 72.7 miles on 2.8 G of propane, and that is ~ 26 mpg. Or about 52 mpg if you could count on using a Combined Cycle turbine ~ 60% efficiency. So probably in between, call it 39~40?
Best case for the Tesla is not too impressive compared to a modern hybrid, worst case, many cars blow the Tesla away in efficiency.
OK, we do need to account for refining and delivering gasoline to the gas station. IIRC, I've seen 6 kWh of energy (not electricity! much of comes from burning waste from the refining process itself). I'll see if I can find that number, but i it's 10% of the delivered BTU or kWh, just multiply the ICE/hybrid mpg by 0.9 - still good.
Not counting other losses in the EV, like standby, heat, AC, etc. Not sure those are included in the EPA range #'s. So that would even things up a bit anyhow.
And it looks like NW-Bound's arithmetic on propane kWh was correct - I knew it would be
-ERD50
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