Study of triboelectric kinetic energy harvester with an asymmetric double variable capacitor implemented in a bennet doubler

Overview & Synopsis

Energy harvesting is the process that involves converting otherwise unused energy present in our environment into usable electrical energy that can be used to power an electronic system. Electrostatic kinetic energy harvesters (eKEHs) utilize vastly present kinetic energy that originates either from an object in motion or vibrations and converts it into electrical energy. The employed principle is based on a polarized variable electrostatic capacitor. With an addition of a triboelectric layer between its plates and utilizing the triboelectrification effect, an eKEH is transformed into a triboelectric nanogenerator (TENG). This type of transducer accumulates charges by contact in the triboelectric layer which thus becomes an electret whose generated semi-permanent electric field allows a variation of the distribution of the electric charges in the electrodes by electrostatic induction.Altering the architecture of a TENG by adding the third electrode, a single-capacitive transducer is converted into a double-capacitive TENG. Doubling the conversion element in a transducer is expected to increase the amount of converted energy. Chosen electronics circuit to condition obtained signal from the generator is Bennet’s charge doubler. An increase without saturation point at the output of this circuit is the unique characteristic of this unstable charge pump. It reflects through an exponential increase of output voltage and a number of charges accumulated in the storage capacitor which increase (in theory) in an infinite way. This means that the surface of the charge-voltage cycle at the terminals of the TENG, and thus the converted energy of the mechanical domain, increases at each iteration of the mechanical cycle of the transducer.The scope of this thesis encompasses the simulation, analytical and experimental research of Bennet’s charge doubler with two asymmetric variable capacitors each containing a triboelectric layer. It is postulated that the performance of the "double TENG" - "double Bennet" system is superior to the classic Bennet’s double. The results of analytical and simulation analysis have shown that the expected behavior of this circuit aligns with hypothesized performance results. The system has been tested experimentally. It is concluded that the results of the constructed system are relevant when compared with the reported performance of the classic "single-capacitive TENG" - "Bennet’s doubler" system.When compared with classic Bennet’s doubler, double Bennet reaches the same voltage levels in less time. That is due to the advantage of double capacitive TENG which increases the number of accumulated charges per mechanical cycle. In analytical analysis, it was found that the two TENG capacitors are codependent and that in operation they affect one another.The output signal of double Bennet is characterized by high voltages ranging from a few hundreds of volts to a few kilovolts (kV). To reduce the rectified output voltage to a level compatible with a commercial application, a Buck DC-DC converter is implemented. This requires a switch. This thesis proposes and studies the use of a high-voltage MEMS micro-plasma switch whose actuation voltages is defined by Paschen’s law. Within the scope of this thesis, the theoretical and experimental studies of this law at the micrometer scale propose optimal actuation voltages for better management of the converted energy