Check out this printable 3 phase alternator I designed a while back, I don't have a reprap so it hasn't been tested yet. It is fairly crude, but it should be able to generate electricity.More info here: http://dev.forums.reprap.org/read.php?1,11789,page=1You need: 8 mm threaded rod nuts and washers enamel coated copper wire, about 36 gauge should do 1 608 skate bearing, 8mm ID, 22 mm OD, cost $1.00 http://www.skates.com/roller-skate-bearings-s/34.htm8 9 mm diameter neodymium disc or ring magnets, cost $5.20 http://www.supermagnetman.net/product_info.php?cPath=41&products_id=389 Epoxy or glue Power drill, optional, for winding coilsThere are 3 files, the stator(where the coils go), the armature(alternator magnet 2), and the coil winding tool, which is optional if you want to wind them by hand.The coil winding tool: The coil winding tool connects to a power drill via a length of 8mm threaded rod held on to it by nuts. Wind a couple times by hand then use the power drill to wind the rest until the coil covers about as much area as the tool. Carefully feed the wire back and forth as not to have it cross over itself. Remember leave some wire with the insulation off so you can connect them! Wind 9 coils.The stator: The hole in the center is where the skate bearing goes, screw some threaded rod in from one of the side holes to keep it in place. Next wind the coils, then put the threaded rod through the bearing. Then secure the threaded rod to the bearing with two nuts and two washers.You should wire the coils together as seen in steps 12 and 14: http://www.instructables.com/id/Pringles-Wind-Turbine-Pleech---Version-One/Or if you are familiar with alternators in wye configuration. http://www.tpub.com/content/neets/14177/css/14177_73.htmThe armature: put magnets in holes with the poles n-s-n-s-n-s... configuration and glue them in with epoxy. Them attach the armature to the threaded rod of the stator using nuts. Adjust the armature so that it is as close to the coils as possible and can freely rotate.Wind turbines anyone?