Electrical generator where a dielectric is pulled out of a capacitor
Yes. Such a generator does exist, and has done for centuries. It is called a "Wimshurst Machine"


  In a Wimshurst machine, the two insulated discs and their metal
  sectors rotate in opposite directions passing the crossed metal
  neutralizer bars and their brushes. An imbalance of charges is
  induced, amplified, and collected by two pairs of metal combs with
  points placed near the surfaces of each disk. These collectors are
  mounted on insulating supports and connected to the output terminals.
  The positive feedback increases the accumulating charges exponentially
  until the dielectric breakdown voltage of the air is reached and an
  electric spark jumps across the gap.
  
  The machine is theoretically not self-starting, meaning that if none
  of the sectors on the discs has any electrical charge there is nothing
  to induce charges on other sectors. In practice, even a small residual
  charge on any sector is enough to start the process going once the
  discs start to rotate.


However, the energy comes from the energy put into the rotating disk(s)