car that runs 200 miles on compressed air


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After about 2:40 the narrator has a stupid idea: use compressed air to make compressed air, never run out of fuel.

http://youtu.be/OJeMnZuOOJU

Never run out of fuel? The energy source is not the air in the tanks, it is the pressure of the air. To produce the pressure one needs a compressor. And what does a compressor run on? Most likely it is electric powered. And what produces the electricity? Most likely a generator turned by a steam turbine which requires heat to turn water into steam. And what heats the water. Not compressed air. It will be coal, oil, natural gas or fission. And these fuels one can run out of.

It all comes down to the ideal gas equation

pV= NRT

where p is the pressure, V is the volume, N is the number of moles of gas, R is the gas constant and T is the temperature in Kelvin. If you want to find out the energy look at what produces the temperature T.

Ba'al Chatzaf

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A simple air pump as for bicycles would let you compress the air, and get your cardio-aerobics in for the day. (That might lead to more effective and efficient pumps, worked by pedaling, lifting, windmilling, etc., as the standard bicycle pump is painful.)

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After about 2:40 the narrator has a stupid idea: use compressed air to make compressed air, never run out of fuel.

http://youtu.be/OJeMnZuOOJU

Can anybody be that stupid? He actually called it "perpetual motion." Maybe he was sticking a knife between the ribs of this thing. My bet, though, is on stupid.

--Brant

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Yes, compressed air has to be created by another power source, in most cases fossil fuels. Likewise true for electric car batteries. Yet, the enviro-lobby likes the little tin cans because, unlike traditional cars, they don't give off many hydrocarbons. But is there a net hydrocarbon saving?

What about the fossil fuel plants that generate the electricity that runs the compressor that fills the air tank? That counts.

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Yes, compressed air has to be created by another power source, in most cases fossil fuels. Likewise true for electric car batteries. Yet, the enviro-lobby likes the little tin cans because, unlike traditional cars, they don't give off many hydrocarbons. But is there a net hydrocarbon saving?

What about the fossil fuel plants that generate the electricity that runs the compressor that fills the air tank? That counts.

That's easy. Pump up at a hydro dam or nuclear power station.

--Brant

just drive up to the gate

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That's easy. Pump up at a hydro dam or nuclear power station.

--Brant

just drive up to the gate

over 80 percent of the electricity generated in the U.S. is generated by plants burning hydrocarbons

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Let us look at the energy density of compressed air. I one meter cubed tank at 70 atmospheres pressure stores 21 megajoules of energy. A ten gallon gasoline tank stores 10 x 1055 x 114,000 joules which is 1.2 giga joules of energy which is almost 6 times as much energy. If a car can go 300 miles on a 10 gallon tank of gasoline it will go only 50 miles on a tank of compressed air assuming the energy is transformed into motion equally in both cars. A compressed air tank on meter cubed is over 32 cubic feet volume. That is a big air tank.

Compared to a gasoline powered auto the compressed air version is pretty feeble.

But that is not the end of woe. When the air is let out of the tank it cools way down and it will freeze any moisture in the plumbing and block the flow. This is a matter of thremodynamics (see Charle's Law). So the tank will have to be heated to prevent ice clogging of the plumbing or the engine. So a battery will be required to power a heater for the compressed air tank. Rapid filling of the air tank heats it up, and dangerously (Charle's Law going the other way). Compressing gas heats it up. So your compressed air buggy is going be hauling a tank which is pretty hot. It will have to be insulated.

Then there is the matter of power loss. As the air is drown from the tank, the pressure lowers and the rate of energy transfer to the motor diminishes. compare this to an electric vehicle which delivers full power until the battery is completely down. Or a gasoline or diesel powered car which delivers full; power until the fuel tank is emptry.

All in all the compressed air car is a looser without a mizoozer.

It is a bad idea. Forget about.

Ba'al Chatzaf

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That's easy. Pump up at a hydro dam or nuclear power station.

--Brant

just drive up to the gate

over 80 percent of the electricity generated in the U.S. is generated by plants burning hydrocarbons

Well, get your air elsewhere. We have to fight climate change.

--Brant

Jerry should have started this thread in the Humor section

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After about 2:40 the narrator has a stupid idea: use compressed air to make compressed air, never run out of fuel.

http://youtu.be/OJeMnZuOOJU

Hayzoooos Marimba. A perpetual motion machine! There ain't no such thing.

Ba'al Chatzaf

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Yes, compressed air has to be created by another power source, in most cases fossil fuels. Likewise true for electric car batteries. Yet, the enviro-lobby likes the little tin cans because, unlike traditional cars, they don't give off many hydrocarbons. But is there a net hydrocarbon saving?

What about the fossil fuel plants that generate the electricity that runs the compressor that fills the air tank? That counts.

Read the first sentence in what you quoted.

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