I just had an idea for a new energy source, but I don't know how well it would work. Ideas, anyone?

So, it would consist of a spinning beam in a vacuum. The beam would spin around a central axis which is connected to a magnet and copper coil, in turn producing electricity. The beam would spin for a long time because there would be no drag in the vacuum, providing potentially unlimited electricity while using very little to keep it spinning. The only two problem that I can think of are as follows:
1: The magnetic field may put excessive drag on the axis and slow down the beam.
2: Maintaining an artificial vacuum may be difficult, and building it in space would leave it difficult to get the electricity to Earth.

Would this be somewhat feasible, Fluther? I’m not knowledgeable in all the math behind such a contraption, but I know that there are all types on this website – I’m sure someone will have an answer.