The growing severity of environmental problems such as plastic waste and climate change has inspired active research into solutions based on recyclable and renewable energy devices. Triboelectric nanogenerators (TENGs) that convert wasted mechanical energy into electrical energy offer a solution that needs to be made recyclable to reduce or eliminate the generation of electronic waste (e‐waste) on their disposal. In this study, an all‐recyclable TENG (AR‐TENG) based on a thermoplastic polymer with a nanohole pattern is developed; it delivers an excellent output power density of 1.547 W m−2 (peak output voltage = 360 V, current = 22 µA) and shows superior mechanochemical stability by maintaining its performance after immersion into seawater or 1 000 000 cyclic tests. The practical utility of this AR‐TENG is demonstrated through its use to power a buoy‐type ocean monitoring system and an intelligent life jacket, whereas recyclability is demonstrated by the re‐fabrication of the AR‐TENG; reusability in other devices is validated by the successful fabrication of a plasmonic color filter. This work paves the way for the efficient harvesting of renewable energy without the concomitant production of e‐waste; therefore, it contributes to the mitigation of global environmental problems such as global warming and ozone depletion.
For the purpose of stably supplying electric power to the underwater wireless sensor, the energy harvesting technology in which a voltage is obtained by generating displacement in a piezoelectric material using flow-induced vibration is one of the most attractive research fields. The funnel type energy harvester (FTEH) with PVDF proposed in this study is an energy harvester in which the inlet has a larger cross-sectional area than the outlet and a spiral structure is inserted to generate a vortex flow at the inlet. Based on numerical analysis, when PVDF with L = 100 mm and t = 1 mm was used, the electric power of 39 μW was generated at flow velocity of 0.25 m/s. In experiment the average RMS voltage of FTEH increased by 0.0209 V when the flow velocity increased by 1 m/s. When measured at 0.25 m/s flow velocity for 25 s, it was shown that voltage doubler rectifier (VDR) generated a voltage of 133.4 mV, 2.25 times larger than that of full bridge rectifier (FBR), and the energy charged in the capacitor was 44.3 nJ, 14% higher in VDR than that of the FBR. In addition, the VDR can deliver power of 17.75 μW for 1 k load. It is shown that if the voltage generated by the FTEH using the flow velocity is stored using the VDR electric circuit, it will greatly contribute to the stable power supply of the underwater wireless sensor.
The Drivability Index (DI) of gasoline is a measure of fuel performance of engine operations. Therefore, distinguishing a gasoline of specific DI in advance is useful for improving engine efficiency and maintenance. We consider the problem of distinguishing between normal gasoline and HiDI (High DI) gasolines and propose an electromagnetic wave-based rectangular cavity sensor. For commercialization, it is designed to have a simple structure and basic resonance mode TM110 in the common frequency range of 5 GHz to 6 GHz. The proposed sensor has a simple structure of monopole radiating electromagnetic waves and a metal rectangular cavity containing gasoline samples. By considering one commercial normal gasoline sample of permittivity 2.157 and five HiDI gasoline samples of permittivity in the range of 2.018 to 2.218, we obtain 11.5 MHz resonance separation at room temperature to the closest HiDI sample from the simulation and 8 MHz resonance separation from the fabricated sensor experiment. To verify the feasibility of the fabricated sensor under temperature variation from 0°C to 20°C, we derived a simple linear distinction function of resonance frequency and S11 parameter and obtained a minimum 4.4MHz resonance separation. These results showed that the distinction performance for normal gasoline is robust to temperature variations. Furthermore, we showed that the distinction property is robust to design parameter errors, installation position variations and sensing time variations. These results show that the proposed sensor can be utilized effectively for distinguishing normal gasoline.
In this paper, a cylindrical cavity sensor based on microwave resonant theory is proposed to distinguish between various driveability index gasolines under temperature variations. The working principle of the proposed sensor is based on the fact that the change in permittivity of gasoline samples inside cavity sensor will also cause a change in resonant frequency. The proposed sensor has good sensitivity in terms of resonant frequency separation, which enables it to capture the minute permittivity changes and distinguish different gasolines. By using a normal gasoline permittivity of 2.15 and changing sensor dimension parameters, the sensor was designed by high-frequency structure simulator (HFSS). The designed sensor has a resonant frequency of 7.119 GHz for the TM012 mode with a 19.2 mm radius, a 35 mm height, and one-port coupling probe of 8 mm height. The proposed cylindrical cavity sensor shows advantages of excellent resonant characteristics of small cavity size and small sample amount. To optimize and verify the parameters of the sensor, many experiments have been carried out using HFSS and a vector network analyzer (VNA). Consequently, the proposed sensor is proven to be robust to temperature changes in terms of resonant frequency separation. The minimum frequency separation to distinguish gasoline samples is found to be larger than 29 MHz with reflection coefficients under −11 dB for temperature changes from −35 °C to 0 °C. The consistency of experimental and theoretical results also are presented, which guarantees accuracy of the sensor for the distinction of gasoline.
Polyvinylidene fluoride (PVDF) is an emerging method for energy harvesting by fluid motion with superior flexibility. However, the PVDF energy harvester, which has a high internal impedance and generates a low voltage, has a large power transmission loss. To overcome this problem, we propose an impedance-coupled voltage-boosting circuit (IC-VBC) that reduces the impedance of the PVDF energy harvester and boosts the voltage. SPICE simulation results show that IC-VBC reduces the impedance of the PVDF energy harvester from 4.3 MΩ to 320 kΩ and increases the output voltage by 2.52 times. We successfully charged lithium-ion batteries using the PVDF energy harvester and IC-VBC with low-speed wind power generation.
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