Re: SRAM or nuvinci electric pedal asssist

Ryan Cousineau wrote:
In article <rcousine-596579.06370123122008@[74.223.185.199.nw.nuvox.net]>,
Ryan Cousineau <rcousine@xxxxxxxxx> wrote:

In article <cad59565-7189-48c8-80dc-ed57924af638@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Chalo <chalo.colina@xxxxxxxxx> wrote:

Carl Fogel wrote:
"A gallon of gas weighs about 6.3 pounds and produces roughly 35
kilowatt hours of energy."
--and is toxic, dangerously flammable, stinky, and totally unsuitable
to park inside an efficiency apartment or office cubicle.

Chalo
The general point about how crazy gasoline is makes sense, but Carl is pointing out something else that is overlooked a lot by people who should know better: gasoline and diesel are used as fuels because nothing as easy to handle as them has anywhere near the same energy density.

Re-reading, I ought to clarify this: gas is basically the cheapest source of reasonably portable energy available. It's common, the industrial processes to refine it work very well, and its energy density is great.

Coal is much cheaper. When it comes to electricity generation, hydro & geothermal often beat even coal, wind is close, solar thermal isn't far off.

Now, an internal-combustion engine only uses a fraction of that fuel to make a car's wheels move, which is why other technologies even have a chance.

This, however, holds, and is the reason why gasoline can be beaten at all.

Converting thermal energy to electrical energy typically runs about 30% efficiency (worst case, 60% best case), so with coal at $150/ton, 1kW-h of electricity costs around $0.10. From that POV, you could say that the 35kW-h in a gallon of gas is (currently) cheaper than the $3.50 coal generated electricity, but that's off by a factor of about 5, so the "electric equivalent" is more like $9-20/gal. (gas price between $1.60-4.00).

Unless you're heating a house, it doesn't make sense to talk about raw (thermal) energy. It makes more sense to talk about electrical energy since the thermal energy must be converted to mechanical and electric can be considered an equivalent for it. The 120 lb of gas in a 20 gal tank could be replaced by 240 lb of coal for the equivalent thermal energy, filling your tank (bin) would be much cheaper.

Of course true costs need to include all factors, including all forms of environmental and economic impact.



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