Design and Implementation of Electrostatic Energy Harvesters with Green Nanomaterials

In recent years, smart infrastructure systems have been widely used to connect the physical world to the internet. Extending connectivity between these systems (e.g. smart home appliances, intelligent transportation, smart power grids, etc.) is often referred to Internet of Things (IoT). One of the key technology in the IoT is wireless sensor networks (WSNs) which are platforms that containing sensing futures, processing units and communication capabilities. For the sensors that are placed in an environment that vibration occurs (e.g. machines and vehicles), harvest kinetic energy and use it to power the sensors can extend the battery lifetime of the WSNs. By using the kinetic energy, vibration-based harvesters are a promising solution to achieve continuous-operation for low-power WSNs. In this thesis, a regenerative electrostatic energy harvester is introduced and analyzed. The proposed harvester operates in a regenerative mode and can self-start from electrical noises without a startup battery. A class of regenerative harvesters is designed to archive different purposes (e.g. obtain higher output power, or start under lower vibrations) under different vibration conditions. The mechanical model of the transducer is combined with the electrical circuits to demonstrate the influences of the transducer force under the rapidly increased voltages in the regenerative harvester. By understanding the coupled model of the harvester, suitable materials and their fabricating process are introduced. In this research, renewable materials include nanocellulose and carbon nanocomposites are used to fabricate the variable capacitors. The proposed biobased capacitors are very thin and light, and have good flexibility. The use of biobased materials decreases the environmental impact and increases the biodegradability of the energy harvesters. In the thesis, we also investigate the feasibility of combining green nanocellulose materials and inks that contain water-dispersible carbon nanoparticles to fabricate the substrate, the dielectric layers, and the conductive layers using only a conventional low-cost inkjet printer. The proposed green printing technique is promising for manufacturing organic electronic devices at reduced costs and environmental footprint. The model of proposed regenerative energy harvester is modelled, simulated, verified, and tested. The materials and fabricating process of the transducer is studied and optimized. The regenerative harvester is then assembled, measured and compared with simulation results and results from the literature. The simulation and experimental results match well and present the easy start-up and scalable energy availability of the proposed harvester for driving WSNs and other low-power electronic devices.