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Comment by grecy | Hacker News Reader

Right, but that doesn't mean anything when we're only getting ~16% efficiency in our ICE.

Gasoline is still way ahead. It still has ~40x the density of batteries. Even at 16%, it's still going to be about 6x as efficient as batteries, even if batteries + electric motors are at 100% efficiency.

A Toyota Camry car carries 17 gallons of fuel, which, at 6 lbs per gallon, is about 100 lbs. At 28 mpg, that's enough to travel 476 miles. The Tesla S carries a 900 lb battery which is enough to travel about 250 miles. In miles per lb, that's 4.7 for the Toyota, and 0.28 for the Tesla.

Obviously, there are a lot of other considerations than just miles per lb, but gasoline's energy density and portability are stellar.

Good thing we have been doing better than that for some time now.

>The MAN S80ME-C7 low speed diesel engines use 155 grams (5.5 oz) of fuel per kWh for an overall energy conversion efficiency of 54.4%

>The efficiency of a combined cycle gas turbine system can exceed 60%.

http://en.wikipedia.org/wiki/Diesel_engine#Fuel_economy

In fact, it's shameful how underutilized diesel engines are in this world. Same with stirling engines.

If you're allowed any scientific process regardless of engineering challenge and economics, thermally crack the crude down to hydrogen and pure carbon coke deposits, sequester the carbon for carbon credits, and pipe the H2 into fuel cells for near 100% efficiency.

(That's a marine engine though. Larger engines are more efficient.)

Maybe so, but 16% is misrepresentative of ICE's as a whole.

It means a lot. The Tesla Model S (a reasonable sedan) needs 85kwh to reach a 300+ mile range, and the drivetrain is probably about as efficient as electric cars will ever be. So realistically, we need 85-100kwh of power on board a reasonable car.

A single gallon of gasoline is ~33kwh of power. At 30mpg (easy for a sedan), 10 gallons (330kwh) is sufficient for a 300 mile range. So the Tesla is ~4 times as energy efficient as internal combustion, and unlikely to get any better.

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