No abstract

No abstract

We present an optimized flutter-driven triboelectric nanogenerator (TENG) for wind energy harvesting. The vibration and power generation characteristics of this TENG are investigated in detail, and a low cut-in wind speed of 3.4 m/s is achieved. It is found that the air speed, the thickness and length of the membrane, and the distance between the electrode plates mainly determine the PTFE membrane’s vibration behavior and the performance of TENG. With the optimized value of the thickness and length of the membrane and the distance of the electrode plates, the peak open-circuit voltage and output power of TENG reach 297 V and 0.46 mW at a wind speed of 10 m/s. The energy generated by TENG can directly light up dozens of LEDs and keep a digital watch running continuously by charging a capacitor of 100 μF at a wind speed of 8 m/s.

Aiming to improve the energy harvesting efficiency under low wind speed, we propose a dual auxiliary beam galloping triboelectric nanogenerator (GTENG) in this work. The structural design of a single main beam and a pair of auxiliary beams enables the device to work under a higher vibration frequency when triggered by wind. A stable and improved working frequency of about 4.6 Hz was observed at various wind speeds. The device started to vibrate at a wind speed of 1.7 m/s and generated an output voltage of about 100 V. The outputs of this GTENG approach to saturation at a wind speed of around 5 m/s. The output voltage and short-circuit current reached 260 V and 20 μA, respectively. A maximum power of about 1 mW was obtained under a wind speed of 5.7 m/s with a load of 33 MΩ. Moreover, the effectivity and long-term stability of the device were demonstrated under low wind speeds. A digital watch is powered for 45 s after charging a 47 μF capacitor for 120 s at a wind speed of 3.1 m/s.

A novel energy harvester based on vortex-induced vibration (VIV) of the sphere and piezoelectric effect is proposed to efficiently gather wind energy from all horizontal directions. An elastically-supported foam sphere is vertically arranged and considerably oscillates in the cross-flow direction when the wind speed is in the lock-in region. A piezoelectric beam is attached to the supported sphere by a spring and deforms periodically around the original buckling state, thereby converting kinetic energy into electrical energy. Experimental studies are performed to assess the power output of the harvester when exposed to wind flows with varying directions and speeds. The omnidirectional wind flow is divided to 12 orientations with the interval angle of 30°, and the wind speeds range from 1.17 m/s to 7.87 m/s. The testing findings indicate that the harvester has excellent consistency in both lock-in region and average power for various wind azimuths. When the wind direction is changed from 0° to 360°, the peak average power changes from 179.8 μW to 247.5 μW, and the wind speed region where the sphere undergoes vibration changes from 2.58 m/s"~" 7.05 m/s to 2.58 m/s"~" 7.87 m/s. Following that, the effects of the length of the supporting spring and the diameter of the sphere on the output average power and lock-in region are investigated experimentally. Finally, a demonstration of powering a wireless sensing node is performed to show applications of the designed energy harvester in windy conditions.