  This paper presents the physical operating principles of several micro wind
turbines based on different aerodynamic forces: drag-type Vertical Axis Wind
Turbine (VAWT) and lift-type Horizontal Axis Wind Turbine (HAWT). All these
devices share the similarity of exploiting the same mechanical-to-electrical
conversion: the electrostatic conversion. This type of conversion is based on
capacitance variations induced by the motion between a rotor and a stator and
requires a source of polarization. We will focus our study on two technologies
to polarize the capacitive structure: the use of electrets and the exploitation
of triboelectricity. Some experiments conducted in a low-speed wind tunnel
between 0 and 20m.s-1 have highlighted power flux densities from 0 to
150{\mu}W.cm-2 corresponding to power coefficients of 0 and 9% respectively.
Among these results, we can especially retain an ultralow speed operation,
which has never been reached until now, in terms of speed and efficiency (9% of
efficiency at 1m.s-1). Finally, we will end up comparing different types of
circuits to supply a temperature/acceleration sensor, in order to complete the
energy harvesting chain.
