by steam_cannon » Thu 31 May 2007, 16:26:30
$this->bbcode_second_pass_quote('whereagles', '')$this->bbcode_second_pass_quote('Hawkcreek', 'A') steam car could run an hour on 25 pounds of good firewood. Maybe we should go for steam?
Steam engine thermodynamical efficiency is 5-10%, maybe 15% in lab conditions. Gasoline engine is 15-25% - much better.
True, but many other factors play into fuel and engine choice.
Thermodynamics, transport cost, availability and EROEI...
For wood, the EROEI can certainly be better then a depleted oil deposit and you don't have to rely on an oil company for it. Gasifying hay to run farm tractors is another example.
Regarding coal, lets say:
1 ton of coal =< 63 gallons of gas, 1.5 barrels of fuel
Lets also say all that fuel is gasoline.
1 gallon gasoline 125,000 Btu
1 ton coal 16,200,000 to 26,000,000 Btu
63 Gallons of gas * 125,000 Btu = 7,875,000 Btu
And lets say that...
Auto efficiency 25%
Steam efficiency 8%
But since both engines are using coal...
16 200 000 / 7 875 000 = 2.05714286 twice less energy
Engine efficiency divided by energy lost in processing.
25/2.0
So compared to burning coal directly, an auto engine burning coal based fuels may have a
total process efficiency more like 12.5%
Conclusion: engines using coal liquids are 12.5% efficient
I suspect there are better ways to calculate that, but
I'm just saying efficiency of the engine isn't the only factor. Since both are using coal, total process efficiency must be accounted for. Like how compressed air engines are highly efficient, but where the power comes from to compress the air also needs to be accounted for. Or like converting coal to hydrogen to fuel a car, big energy losses there too...
So an engine that burns coal, oil, wood or straw might have practical advantages. Just as using a combined cycle gas turbine of 50% to 60% efficiency to produce electricity for electric car batteries, might be competitive with coal to liquids. So you know, maybe 8% efficiency from directly burning coal in a steam engine would be competitive with coal to liquids schemes.
"In practice, a steam engine exhausting the steam to atmosphere will have an efficiency (including the boiler) of 1% to 8%, but with the addition of a condenser the efficiency may be greatly improved. A power station with steam reheat, etc. will achieve 30% to 42% efficiency. Combined cycle in which the burning material is first used to drive a gas turbine can produce 50% to 60% efficiency. It is also possible to capture the waste heat using cogeneration in which the residual steam is used for heating. It is therefore possible to use about 90% of the energy produced by burning fuel—only 10% of the energy produced by the combustion of the fuel goes wasted into the atmosphere."
http://en.wikipedia.org/wiki/Steam_engine#Efficiency
steam car
http://www.stanleysteamers.com/modern_steam.htm
steam jet boat
http://www.newscientist.com/article.ns?id=dn3321
Steam Bicycle
http://www.users.globalnet.co.uk/~pattl ... rc0373.htm
Personally, despite my nick I favor solar, gasification, and gas to liquids more then steam for practicality, but steam still has potential.
Well my teakettle is whistling!
