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Old 07-07-2005, 06:22 PM
AZCivic AZCivic is offline
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Real Name: Brandon
Location: Phoenix, AZ
Hybrids: 1997 Civic HX
Posts: 878
Default Re: WSJ Biodiesel article: both +s & -s

Quote:
Originally Posted by EricGo
I'm partial to electricity, myself. Straight from the battery to the motor, and not used to heat a vat to fractionate oils that then burn dirty.
Electricity is great, but the whole point of liquid fuels is to use it as a storage mechanism. Batteries don't do you much good without range and rapid refueling. If you go through the gyrations of converting units, you'd come up with the following table:

200 pounds diesel fuel = 1123 kw/h
200 pounds of gasoline = 1112 kw/h
200 pounds of E85 = 737 kw/h
200 pounds of lead-acid batteries = 3.2 kw/h
200 pounds of NiMH batteries = 6.3 kw/h
200 pounds of LiIon batteries = 13.6 kw/h

I'll also produce a second chart here that accounts for thermal efficiency. Diesel is at least 40% thermally efficient these days, and gasoline/ethanol with port fuel injection can be up to 35% thermally efficient with technology such as the Prius engine. Corrected numbers then become:

200 pounds diesel fuel = 449 kw/h
200 pounds of gasoline = 389 kw/h
200 pounds of E85 = 258 kw/h

Even if you don't count how much faster you can refuel a liquid fuel car, liquid fuels still win by a large margin over batteries, which honestly aren't 100% efficient anyway, but they are darn close, so I'll leave it at that.

For those wondering how the numbers were generated, diesel is 6.75 lb/gal, 128,000 BTU, gasoline is 6 lb/gal, 114,000 BTU, E85 is 6.5 lb/gal, 81,800 BTU. The battery efficiency per pound came from this page.

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