A piezoelectric frequency up-converting energy harvester with rotating proof mass for human body applications

• Published in: Sensors and actuators. A. Physical. 2014-02, Vol.206, p.178-185
• Main Authors: Pillatsch, Pit, Yeatman, Eric M., Holmes, Andrew S.
• Format: Article
• Language: English
• Subjects: Acceleration; Devices; Energy harvester; Energy harvesting; Frequency up-conversion; Human body; Inertial; Piezoelectric; Piezoelectricity; Proving; Rotating; Rotational; Upconversion
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2013.10.003

•We present a piezoelectric inertial energy harvester for human motion.•Benefits of rotational devices are discussed.•The successful results of a device test during a half marathon are presented.•Alterations to the magnetic coupling are made based on the findings.•Power output measurements in the laboratory consequently show significant improvement. Energy harvesting from human motion faces the challenges of low frequency and random excitation. One strategy that has been successful in the past is frequency up-conversion. This paper introduces an inertial device that combines this principle, in the form of piezoelectric beam plucking through magnetic coupling with a rotating proof mass. The advantages rotational systems can have for body movements are discussed. The prototype is described and tested in a real world environment during a running race and later on in a laboratory environment on a custom built linear excitation table. Throughout these tests it is confirmed that such a device can operate over a broad range of frequencies and under varying orientations, making it suitable for this intended application. Across frequencies between 0.5 and 4Hz and accelerations between 1 and 20m/s2 power outputs in the range of tens of microwatts were achieved, with a peak value of 43μW at 2Hz and 20m/s2 when the rotor went into a continuous rotation.