This is quite possible. During the fabrication of scale model steam locomotives, they are "run on air" to set up the valve gear and test the chassis before the steam boiler is installed. If storage of compressed air was possible at greater energy density it may be possible to run scale locomotives on air instead of steam!
Compressed air does have the problems mentioned - low energy density etc. but higher compressed air pressures are now possible way past SCUBA tank levels by specialized tank construction such as used for oxygen storage for firefighters.
While automakers have all but anointed electric hybrids as the successor to our gas-guzzling cars, there is one competing technology that may have a realistic chance — at least on city streets.
Researchers at Lund University in Sweden announced today that they have developed a compressed air hybrid engine that would allow buses to cut fuel consumption by 60 percent.
“The technology is fully realistic. I was recently contacted by a vehicle manufacturer in India which wanted to start making air hybrids”, says Lund University researcher Per Tunestål.
Pneumatic or “compressed air” engines has been a concept that researchers have toyed around with for about a couple centuries. The technology never got very far because, well, the car themselves didn’t go very far. This is due to the fact that compressed air has an extremely low energy density compared to other engine technologies.
But recently, researchers have brought about a resurgent interest in pneumatic air technology by developing hybrids that primarily run on gas, but can also tap into a tank of compressed air when an added burst is needed.
Air hybrids offer some attractive selling points compared to their electric counterparts. The technology is cheaper since it can easily be integrated into diesel, petroleum or natural gas engines. This is done by re-configuring the engine (which already works somewhat like an air compressor) and adding a chamber to store the compressed air. Stepping on the brakes helps to continually replenish the energy reserves, which makes it well-suited for the constant stop-and-go of city driving. And although air hybrids haven’t shown to be as energy efficient as electric hybrids, proponents believe the technology is close to closing the gap.
To test out the real-world viability of their technology, the researchers ran the engine in a simulation and reported calculations that showed nearly half of the energy captured from braking could be re-used later.
“This is the first time anyone has done experiments in an actual engine,” says Sasa Trajkovic, a researcher at Lund University.
The researchers are hoping to take the technology a few steps further and convert their research results from a single cylinder to a complete, multi-cylinder engine.
Photo: Motor Development International
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