회전 에너지 적용을 위한 다학제간의 에너지 하베스팅 연구

Abstract

Energy harvesting provides the opportunity to power wireless sensors perpetually, and rotational type piezoelectric energy harvesters have been actively researched. However, previous works have the disadvantages, such as low power density, low durability, narrow resonance frequency range, and low efficiency. In order to solve the problems, I designed and optimized the piezoelectric energy harvesting device and circuit for rotational energy application. First, the hybrid type device on a secondary impact method is designed to increase the power density and the saturation frequency. It is shown that the RMS output power of the hybrid type is 324% higher than that of the conventional type at an impact frequency of 20 Hz. In the optimum impact frequency condition, the hybrid type generated 124 mW (RMS value) and 342 mW/cm3 at an impact frequency of 60 Hz. The output power of hybrid type device is 12 times higher than previous works. Section 3 present the device that can be uniformed stress distribution was designed to improve the durability of the device. The experimental results show that the b-type did not crack even after 40 h. From design, simulation, and experiment process, I was able to determine the most durable piezoelectric device shape for application as a power source of electronic devices. In order to improve circuit efficiency, I designed DC-DC converter that can be able to accurate impedance matching and self-powered oscillator circuit in the Section 4. The experimental results show that self-starting time is 0.45 second and mini PEH has a fast self-starting capability, and buck-boost output power was 1.71 mW with resistive load (7kΩ) and high efficiency (88 %). As the results of DC-DC converter that can be able to accurate impedance matching and the self-powered oscillator circuit, I achieve the high efficiency. Section 5 presents adjustable hysteresis converter that can supply the power for electronic devices when low input power is delivered to the circuit. The experimental results show that adjustable hysteresis converter that can supply the power even if a power consumption of an electronic device is higher than generated power from a PEH device. In order to compare the efficiency between proposed circuit and commercial PEH circuit (LTC3588, Linear Tech as shown in Fig. 51), I experimented the two types of circuits in the same input power condition. Comparison results show that efficiency of proposed circuit was 11.7% higher than LTC-3588.