All of celestial space, as a body is in constant motion. This yields a great amount of kinetic energy. A technology based on the principles of an 'Air-Brake' system could generate a great amount of energy.
A method of stabilization to oppose this movement must first be employed. The mechanism could be 'anchored' by a ultra-heavy mass. This would slow the movement of the ‘Air-Brake’ device relative to the surrounding space. A 'windmill' or other kinetic motion capture system could then take advantage of the continuous movement of space, and convert the kinetic energy into a standard form.