A method and system for generating electric energy in a tire includes a device including a housing that extends according to a longitudinal axis X, at least one electrical winding, a magnet movable within the housing along the longitudinal axis, and a force providing element positioned at at least one of two opposite ends of the housing, which is adapted to exert on the magnet a force along said longitudinal axis. The device is fixed on a crown portion of the tire; the tire is rotated on a rolling surface so as to determine variations of forces that act on the device every time the device passes, due to the rolling of the tire, at a footprint of the tire; the force exerted by the force providing element and the variations of forces along the longitudinal axis are exploited so as to cause variations of the magnet position with respect to the at least one electrical winding; and the electric energy generated across the at least one electrical winding as a consequence of the variations of the position of the magnet with respect to the electrical winding is collected.