THEORETICAL PIEZOELECTRIC ENERGY GENERATION FROM THORACIC EXPANSION DURING RESPIRATION FOR SMART WEARABLES

Energy generation and storage is vital to power many sensors used in research and industry. The process by which energy is generated and stored can have critical impacts on the environment. Piezoelectric energy harvesting is one method of renewable energy generation that can have reduced environmental impacts compared to other non-renewable forms of electricity generation. Additionally, it is capable of being portable, which is ideal for powering smart wearables. The respiratory rate monitoring garment is a smart wearable that monitors the breathing rate of the wearer. Piezoelectric energy harvesting was explored as a power source for the respiratory rate monitoring garment by initial theoretical calculations of potential maximum voltage output from the wearer's chest motion during respiration to improve the portability of the design. The constitutive equations in combination with a simple circuit representation of the piezoelectric element in series with the respiratory rate sensor was used to generate equations to calculate the maximum voltage available during normal respiration. The maximum voltage during one minute of simulated respiration was determined to be 3.3 mV, which is much lower than the necessary 6.8 - 7.15 V needed to power the respiratory rate monitoring garment. To make piezoelectric energy harvesting suitable for the respiratory rate monitoring garment, the voltage demands of the microcontroller and LoRa wireless transceiver would have to be significantly lowered, or a new method of data collection would have to be developed. While it was determined that piezoelectric energy harvesting could not provide enough voltage for the existing design of the respiratory rate monitoring garment, it may be suitable for other low voltage sensors or applications.