In most pneumatic systems, the pressure provided by the compressor (or by the air tank) is rated slightly higher than what's required by the tool that needs the highest pressure.
The pressure is then reduced from this source pressure to the (lower) operating pressure by a device known as a pressure regulator. This consists of a pressure sensor, and a valve; as the pressure on the downstream side decreases, the valve opens, as the pressure on the downstream side increases, the valve closes.
This throttling expansion wastes otherwise usable energy.
I propose replacing the pressure regulator with (tiny) air powered motor, which would use the pressure difference between the high pressure source, and the lower pressure desired by the tool attached to the system, to generate mechanical energy.
Naturally, the obvious use for the generated mechanical energy would be to compress fresh air from the atmosphere, and use it to augment the air passing through the motor.-- goldbb, Mar 31 2009 The efficiency of an air-compressor cannot exceed 17%. (I know wherof I speak, I design them for money.) Thus, you're going to retrieve only a teensy teensy part of the excess energy, not to mention the extra tubing involed in returning it to the air reciever.
However, using the extra air for something would make sense. This being the Halfbakery, might I suggest a latte foamer to refresh the hardworking tool-users? [bun pending]-- gisho, Mar 31 2009 I don't intend to have extra tubing to bring the newly compressed air all the way back to the supply tank... just to put it on the "high pressure" side of the regulating device, rather than puttting it on the "low pressure" side of the regulating device.
The logic being that the newly compressed air is probably warmer than the air coming from the tank; thus, mixing the new (warm) air with the cool air (from the tank) warms that cool air, before the cool air moves through the motor.
Thus, it should be slightly more energy efficient (themodynamically) than putting the newly compressed air on the low pressure side of the regulating device.
Some kinds of air powered cars do something like this to prevent the engine from freezing from all the expanding compressed air -- they take a little bit of atmospheric air, compress it, mix it with air from the storage tank, then expand the mixed warm and cool air. It's a much simpler way to warm the air from the tank, than expanding in stages and using interwarmers would be.-- goldbb, Mar 31 2009 something smells of a paradox.-- WcW, Mar 31 2009 WcW, what kind of paradox does it smell like?
It's not perpetual motion or perpetual energy -- it's running off of the energy which would otherwise be discarded.-- goldbb, Jul 28 2010 [+] I was just gonna post this for an hydraulic system.-- FlyingToaster, Jul 30 2010 Awesome anno gisho.(+) for the concept, I never knew that there were losses from different tools.-- 2 fries shy of a happy meal, Jul 30 2010 [WcW] As long as the ratio is favoring loss, there is no paradox.
However:
The energy lost moving through a regulator is at most 1-2 PSI expended specifically to over come the diagphram. Rather than wasting the remainder, it is held back without being spent. That is, a 30 gallon tank at 90 PSI will fill a 30 gallon tank at 30 PSI twice through a regulator (before the pressures balance). With this system, it would fill it once, and the remaining 30 PSI would be used to add air to the high pressure side, which I believe would be less efficient.
Using a similar system to reclaim some of the less than fully employed air coming off the exhaust side of air tools might be possible, with a sufficiently large mechanical advantage.-- MechE, Jul 30 2010 This might make more sense in scuba diving, where the pressure drop is much greater. The shaft energy could then be used to drive a small propeller mounted to the tanks, giving his swimming speed a boost.-- ldischler, Jul 30 2010 random, halfbakery