Studying the effects of temperature on energy harvesting using pre- stressed piezoelectric diaphragms

Energy harvesting is a process in which energy which would otherwise be wasted is captured, stored and then used to power a system. Devices having such capabilities enjoy an extended life particularly advantageous in systems with limited accessibility, such as biomedical implants and structure embedded micro and wireless sensors. A viable family of materials for this purpose is piezoelectric materials because of their inherent ability to convert vibrations into electrical energy. This paper uses a type of pre-stressed PZT-5A Unimorph called Thunder, to actively convert mechanical vibrations into useable power. The effects of temperature, 20-100oC, pressure, 138-345kPa, frequency, 2-5Hz, and load resistance, 0.47-2.0MΩ, on the energy harvesting potential of the device are studied. The data obtained is analyzed using statistical techniques that assess the significance of the factors being studied. Results showed that the effect of temperature by itself on the voltage, AC or DC, and power generation was seen to be not significant. In combination with other factors such as pressure, frequency, and load resistance however, the temperature effect becomes statistically significant. These interaction effects tend to reduce voltage and power conversion. The maximum DC voltage and power were calculated as 108V and 11641μW at 20oC, 275.8kPa, 2.5Hz and 2MΩ. Similarly the greatest peak to peak AC voltage of 338V was also measured at 20C and 2.5Hz. Based on the geometry of the piezoelectric diaphragm the most power density was evaluated to be 15μW/mm.