Global simulations, designs and characterisations of a broadband vibration energy scavenging system are here reported. High damping electrostatic conversion structures have been investigated: Mathematica analytical models have been performed and confronted with ANSYS simulations. A scavenging electronics has also been developed: taking in account ohmic, capacitive and inductive losses, the global conversion efficiency has been calculated. Finally, a macro and a micro resonant structure tuned to 50 Hz have been realized. A scavenged power of 1 mW is already available on the macro structure under a vibration amplitude of 90 µm at 50 Hz. The corresponding global conversion efficiency is about 60% which is in good agreement with mechanical and electrical simulations.