Browsing by Author "Azni Nabela Wahid, Ph.D"

Harvesting energy from ambient sources has sparked significant interest in its potential to drive low-powered electronic devices and reduce electronic waste. Vibration energy harvesting is particularly well suited in these micro-scale types of energy harvesting. A hybrid energy harvester that consists of piezoelectric and electromagnetic energy harvester is the approach to overcome the limitation of a single energy harvester. However, most hybrid energy harvesters suffer from random motion and unidirectional sensitivity as they can only efficiently harvest energy at constant frequency and one direction of motion. The work investigates the capability of an electromagnetic energy harvester and a piezoelectric energy harvester for a wearable device, mainly when operating at a low-frequency range between 1 Hz to 13 Hz at a random direction of human motion. The linear motion of human motion is converted into rotational motion using an eccentric mass. Each time the eccentric mass passes the beam, the magnets repel each other, resulting in the beam deflecting to its maximum possible deflection. This technique is known as the magnetic plucking technique and simultaneously changes magnetic flux around the wound copper coil to generate the largest amount of current. When the eccentric mass rotates at a constant frequency of 5 Hz, the DC voltage produced is 1.5 V, 4.9 mA, and 7.35 mW. In contrast, when manually rotated using hand, it generates 1.4 V, 4.7 mA, and 6.58 mW. However, when the full-bridge circuit replaces with a voltage doubler circuit, the voltage increases to 3.2 V and 3.8 V respectively although the current reduces to half. This research demonstrated the ability of the hybrid energy harvester to effectively harvest energy at low-frequency inputs. The findings of this work provide the possibility to cater for the energy demand for wearable electronic devices and efficiently generate energy at a low and random frequency of human motion.