alt.energy.renewable

-> > I'm intrigued by how they make the air-powered motor run efficiently
-> > while the pressure in the air tank decreases. How can it be as
-> > efficient when the pressure is 50 atmospheres as it is at 200
-> > atmospheres?

-> I would suppose that they either use a regulator to deliver lower
-> (say 50 atmospheres) pressure to the engine at all times or they
-> use a modulated valve that delivers variable amounts of tank pressure
-> air to the engine. No doubt both methods would work out to be very
-> similar mechanisms and the throttle needs to control the amount of
-> air going to the engine anyhow.

-> Anthony

Using a regulator will waste most of the energy as heat. Speed/power
control could be done fairly efficiently by varying the frequency at
which air is sent to the cylinder(s). It doesn't have to be done every
stroke. But designing the engine with some sort of variable expansion
ratio, so it will efficiently use air at different pressures, would be
a major challenge.

Maybe it would be better to have some sort of constant-pressure storage
vessel, maybe with a spring-loaded piston that effectively reduces the
volume of the tank as the air is taken out of it, without varying the
pressure much. But making such a thing so it will work without leaking
at 300 atmospheres, and doing it cheaply and reliably, would be
challenging, to put it mildly.

I wonder if they've really designed this vehicle, or if they are just
floating the idea to see what people come up with.

dow