This air motor/generator is part of a display at the Science Museum of Minnesota the subject of which is storing wind energy by compressing air. The display was built by a group of six senior engineering students from the University of Minnesota as their senior design project. They were aided by staff members at the Science Museum.
The motor uses Airpot cylinders and spool valves. The valves are actuated by a model helicopter swash plate the angle of which is controlled by a flyweight governor. The system runs on about 4 psi. The alternator is of a three phase permanent magnet axial flux design. Its output voltage about 24 volts at 400 rpm with a power output of about .7 watts. In the display it powers a number of LEDs that light up a group of model houses. Compressed air is supplied by a wind turbine driven air compressor which also uses three Airpot cylinders (see http://www.youtube.com/watch?v=JW6nlS3Dcn8&feature=plcp). The compressed air is stored in a gang of seven 2 liter pop bottles.