A friend recently made me aware of this story.
A garage inventor in Bristol, UK, has converted his Puch moped to air power. Propelled by 2 high-pressure scuba tanks, his vehicle has a top speed of about 18 mph, and a maximum range of about 7 miles. Technical enhancements to the pressure tanks and/or the power unit could make the air-powered motorcycle a reasonable inner-city mode of transport for delivery services, security services, etc. Or he could hook up with the Chopper Golf Cart guys and tackle the golf market.
As the comments to the original article attest, there is a lot of debate over whether such a device would ultimately offer any significant ecological advantage once one considers the full cost of energy required to pressurize the tanks, etc., but his Puch does provide an interesting prototype, and one which will spawn other backyard inventors to improve the concept.
Just don’t expect to see a convoy of these heading down I-90 into Sturgis any time soon.