Potential Energy can easily be converted into kinetic energy. You just have to release the body, and it will fall down.
The problem is to convert the kinetic energy into electric energy. There is only one possibility to do so. A phenomenon called induction. When a magnet is approached or removed from a coil a voltage is induced. We can use this effect. In our experimental setup we have a NdFeB (1,2 Tesla) magnet, which we let fall through a plastic pipe to keep the direction. At the end of the pipe we have a coil. For getting the voltage from the entering and the exiting magnet we use a rectifier.
Furthermore we plotted the voltage (blue line) and the magnetic field strength (red line; measured with a Hall-sensor) versus time. The first diagram shows the experiment without a rectifier, the second with a rectifier.
The highest voltage we got in our experiments was approximately 80 V. However if we used a stronger magnet and a better coil we could get better results. Moreover our magnet had only a mass of a half kilogram and not one. So the highest voltage which we can get with this magnet is much lower than the calculated 443 Volt. In conclusion we can say that we converted quite a high percentage of the initial energy.