Posted by Scott Ellis (220.127.116.11) on August 08, 2002 at 02:39:07:
In Reply to: Air Pressure posted by Scott Ellis on August 08, 2002 at 01:32:02:
Here is a device which I believe shows that gravitational energy can be tapped by exploiting air pressure. Imagine we could build a giant wheel 5,500 feet in diameter, with high quality pistons to store and release air pressure at just the right moments as the wheel turns around.
The pressure in the pistons is stored and released instantaneously at positions I and III (the pistons are fitted with locking mechanisms that are triggered at these positions). The piston/weight assemblies are initialized at sea level at position III, so that the assembly is in equilibrium with the weight lifted up at that position.
(Imagine the surface area of the piston heads are 1 square inch.)
At position III, we have
14.7 pounds of air pressure pushing the piston up,
and 1 pound of weight pulling the piston down,
Therefore the assembly is in equilibrium if there are 13.7 psi stored in the piston.
At position I, we have
12 pounds of air pressure and
1 pound of weight and pushing the piston down.
But we can release 13.7 pounds of pressure stored in the piston straight up at this point. Thus, the equilibrium for the assembly at position I is with the weight pushed upwards and 13 psi stored in the piston.
As we come back around to position III again, with the weight still on the outer radius, we have 13 pounds pushing down from the piston plus 1 pound of weight, for a total of 14 pounds pushing down. But we have 14.7 pounds pushing up from the atmospheric pressure at this point. So the weight will be pushed back up to its equilibrium position at this point, repeating the cycle.
Even though the device would be difficult, if not impossible, to build because of its size, I believe that it shows the theoretical possibility of harnessing pure gravitational energy in this way.
: I think atmospheric air pressure is ultimately caused by gravity. As gravity condenses the earth's atmosphere, the air density and pressure increases. Atmospheric pressure changes inversely with altitude, just like gravitational force. At sea level, the average air molecule is travelling at 450 m/s (over 1,000 miles per hour!). That represents a LOT of energy. And that energy ultimately came directly from gravity. Solar heating makes the air molecules move even faster, but it is not necessary. So I think air pressure itself is a REAL conversion of gravitational potential energy into (effectively permanent) kinetic energy. The question is how to tap it?
: As you know the Costa Wheel has glass bottles all along its rim. I read somewhere that the bottles supposedly protect some particular moving parts (like springs) from the weather and elements. This may or may not be true. But glass bottles definitely do a good job of storing energy in the form of air pressure. Could the Costa wheel somehow be exploiting the difference in air pressure between the highest and lowest points of the machine? Could that be why the wheel needs to be so large?
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