Flexible Mechanical Energy Harvesting Generators Based on Piezoelectric and Triboelectric Effects


Student thesis: Doctoral Thesis

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Award date7 Sep 2017


Today, as theenergy crisis problem intensifies, there has been a growing need for searchingof sustainable energy sources to help relieve the consumption of conventionalsources. Batteries, as a key energy storage technology, usually take up a lotof space and they are difficult to periodically replace under the condition ofhuge number of autonomous systems in large networks or harsh environments. Inaddition, such a quantity of batteries would be difficult to recycle and isdangerous for the environment. Therefore, sustainable sources are desperately neededfor sustainable power supply. Especially, to enhance the autonomy of portableand flexible smart systems, efficient flexible energy sources remain to bedeveloped. As a result, the realization of self-powered systems and new energysources is gradually becoming a major research direction for autonomous smartsystems. Wearable and flexible energy harvesters have become the concentrationof research efforts as they are expected to play a critical role in poweringindependent electronic systems. Mechanical energy is widespread and one of themost abundant in our daily life, particularly the activities of human body,which form a rich source of kinetic energy. Therefore applying energyharvesters to scavenge human motion has broad prospects. 

Mechanical energyharvesting generators (MEHG) are developed to harvest mechanical energy mainlyby applying two concepts, the piezoelectric and triboelectric effects. The coremotivation for conducting this study is to realize the energy conversion frommechanical energy to electrical energy by adopting the two effects andunderstand the working mechanism of each mechanical energy harvesting effect.Subsequently, hybrid effect MEHG are fabricated towards improving power outputand energy conversion efficiency.

On the other hand,the contribution of each effect to the final power output and the impact ofeach functional material on thepiezoelectricity or triboelectricity during the power generation process arealso worth exploring to comprehensively understand the output characteristicsof both piezoelectric and triboelectric generators. In addition, theoreticalsimulation work have reported that some design parameters can affect the outputproperties of MEHG, however, limited experimental work has been carriedout to verify the accuracy of the simulation results. In order to optimizingthe theoretical model and improving thepower output of MEHG, variousdesign parameters with a wide range are investigated. The findings can be used as guidance in designing more inclusivetheoretical equations, effective structures and power management of MEHG.

This research workprovides some insights to the MEHG from both materials-structure design andtheoretical understanding aspects. In addition, power management circuit forharvesting the triboelectricity and storing the converted electricity is establishedfor application of MEHG to light up LED lights. This is very promising and ofgreat significance in recycling the waste mechanical energy, particularlyscavenging the low frequency kinetic energy of human activities, which can befurther developed to integrate with smart electronics.