NOVELTY - An electrical energy is generated within a tire by associating a housing (311) including a piezoelectric element to tire portion, rotating the tire at first speed to lead a first deformation of the piezoelectric element during the tire rotation, rotating the tire at second speed higher than the first speed to lead to a second deformation of the piezoelectric element, and collecting the electrical energy generated by the two deformations.    USE - For generating electrical energy within a vehicle tire.    ADVANTAGE - The cantilever-mounted flexure type piezoelectric element, mounted in a portion of a tire in correspondence of the tread area, guarantees a resistance to early cracks and/or breakings that may be caused by tremendous centrifugal force to which the piezoelectric element is subjected during rolling of the tire, especially at high speed.    DETAILED DESCRIPTION - Generating an electrical energy within a tire comprises associating a housing including a piezoelectric element (313) to a tire portion in correspondence of a tire tread area, the piezoelectric element being disposed along a plane orthogonal to a radial direction of the tire and having a first end (315) substantially fixed to the housing and a second end (316) fixed to a loading mass (312), a gap being formed between at least one inner wall of the housing and an outer surface of the loading mass; rotating the tire on a rolling surface at a first rotation speed lower than a given speed, so as to cause the loading mass to oscillate within the gap, thereby leading to a first deformation of the piezoelectric element during the tire rotation; rotating the tire on the rolling surface at a second rotation speed higher than the given speed, to cause the loading mass to contact the inner wall during a first fraction of a complete tire revolution, during the first fraction the tread area corresponding to the tire portion being not in contact with the rolling surface, and to cause the loading mass to oscillate within the gap during a second fraction of a complete tire revolution, during the second fraction the tread area corresponding to the tire portion being in contact with the rolling surface, thereby leading to a second deformation of the piezoelectric element during the tire rotation; and collecting electrical energy generated from the first and the second deformations of the piezoelectric element.    INDEPENDENT CLAIMS are also included for:    (A) a system for generating electrical energy comprising tire; and a power supply (31) comprising a piezoelectric element, where the piezoelectric element is disposed within a housing to have a first end fixed to the housing and a second end associated to a loading mass, a gap being formed between at least one inner wall of the housing and an outer surface of the loading mass; the piezoelectric element is positioned substantially along a plane orthogonal to a radial direction of the tire, where the piezoelectric element, the loading mass and the gap are sized obtain: during rotation of the tire on a rolling surface at a first rotation speed lower than a given speed, an oscillation within the gap of the loading mass associated to the piezoelectric element; during rotation of the tire on the rolling surface at a second rotation speed higher than the given speed, a contact of the loading mass with the inner wall of the housing during a first fraction of a complete tire revolution, during the first fraction the tread area corresponding to the tire portion being not in contact with the roiling surface, and an oscillation within the gap of the loading mass associated to the piezoelectric element during a second fraction of a complete tire revolution, during the second fraction the tread area corresponding to the tire portion being in contact with the rolling surface; and    (B) a system for monitoring operating parameter of a tire comprising a system for generating electrical energy including a power supply; a sensor device including a measurement device adapted to measure the operating parameter and a transmitter device adapted to transmit the measured parameter, associated to the power supply; a receiving device adapted to receive the transmitted measured parameter.    DESCRIPTION OF DRAWING(S) - The drawing shows a flexing piezoelectric element to be included in the sensor device in the invention.    Power supply (31)    Housing (311)    Loading mass (312)    Piezoelectric element (313)    Interspace (314)    First end (315)    Second end (316)