Wearable Ball-Impact Piezoelectric Multi-Converters for Low-Frequency Energy Harvesting from Human Motion

Abstract

Multi-converter piezoelectric harvesters based on mono-axial and bi-axial configurations are proposed. The harvesters exploit two and four piezoelectric converters (PCs) and adopt an impinging spherical steel ball to harvest electrical energy from human motion. When the harvester undergoes a shake, a tilt, or a combination of the two, the ball hits one PC, inducing an impact-based frequency-up conversion. Prototypes of the harvesters have been designed, fabricated, fastened to the wrist of a person by means of a wristband and watchband, and experimentally tested for different motion levels. The PCs of the harvesters have been fed to passive diode-based voltage-doubler rectifiers connected in parallel to a storage capacitor, Cs = 220 nF. By employing the mono-axial harvester, after 8.5 s of consecutive impacts induced by rotations of the wrist, a voltage vcs(t) of 40.2 V across the capacitor was obtained, which corresponded to a stored energy of 178 μJ. By employing the bi-axial harvester, the peak instantaneous power provided by the PCs to an optimal resistive load was 1.58 mW, with an average power of 9.65 μW over 0.7 s. The proposed harvesters are suitable to scavenge electrical energy from low-frequency nonperiodical mechanical movements, such as human motion.

Solar Energy Harvesting to Improve Capabilities of Wearable Devices

“…The generated power in every test is in the order of the milliwatts, which is higher than most values presented in Section 2 (Related Work). For example, in [ 28 , 30 ], TEGs and piezoelectric devices were used for energy harvesting and achieved results in the order of the microwatts. TEGs need a high temperature difference to generate the required power, which is difficult to accomplish in terms of body temperature and environment temperature.…”

“…As for mechanical energy, in [ 30 ], Nastro et al designed energy harvesters for wearables based on piezoelectric cantilevers. Piezoelectric materials generate power from mechanical energy, but they often need high frequency excitation.…”

“…The average power values generated by the devices presented in [ 27 , 28 , 30 ] are in the order of µW, which is enough for wearables with only a few functionalities, such as the presented glucose sensor or the temperature sensor that sends one sample every minute. However, wearable smart devices include more functionalities, so these proposals would not be able to significantly impact on their power consumption.…”

Piezoelectric Energy Harvesting from Low-Frequency Vibrations Based on Magnetic Plucking and Indirect Impacts

“…The most classic ways are referred to as multi-stability or impacts. Several investigations have been carried out on direct impacts, also, in recent times [ 11 ]. This approach has the advantage of easily handling low-frequency input and providing multi-modal structural responses.…”

Projeto E Desenvolvimento De Sistema De Colheita De Energia Baseado Em PVDF Para Aplicação Em Vants

“…Figura 3 -Exemplo de geração de energia dentro de um relógio de pulso usado do movimento de uma bola de aço. [6] Por fim, a colheita de energia triboelétrica gera energia por meio da fricção entre diferentes materiais, que gera cargas eletrostáticas opostas na superfície conjunta. Essa perturbação cria uma diferença de potencial elétrico que gera a corrente elétrica pela superfície de contato.…”