Fig. 1

(a) 2D schematic of ideal OWTENG; (b) simulation diagram of electrostatic field between UEP and LEP when OWTENG is working; (c) 3D diagram of assembled OWTENG; (d) physical prototype of assembled OWTENG; (e) simplified spring oscillator model of OWTENG; (f) simplified capacitance model of TENG unit (color online)"

Fig. 2

Wind tunnel test setup of OWTENG (color online)"

Fig. 3

Variations of (a) lift and (b) drag coefficients with reduced speed; (c) and (d) comparison of experimental and numerical results of sphere's vibrational displacement and OWTENG's peak open-circuit voltage for different wind speeds; (e) and (f) comparison of experimental and numerical results of time-history curves of sphere's vibrational displacement and OWTENG's open-circuit voltage for wind speed of 5.72 m/s, where "Exp." denotes experimental results, and "Num." represents numerical results (color online)"

Table 1

Main parameters of OWTENG"

Fig. 4

Changes in peak open-circuit voltages of OWTENG with wind speed for different values of (a) spring length L1 and (b) sphere diameter D, where "Exp." represents experimental results, and "Theo." represents theoretical results (color online)"

Fig. 5

Time-history curves of open-circuit voltage for OWTENG with various (a) original lengths and (b) sphere diameters (color online)"

Fig. 6

Variations of vibration frequency for OWTENG with wind speed for different (a) L1 and (b) D, where "Exp." represents experimental results (color online)"

Fig. 7

FFT analysis of the open-circuit voltage for OWTENG with various (a) original lengths and (b) sphere diameters (color online)"

Table 2

Wind speed, vibration frequency, reduced speed, and Strouhal number associated with maximum output voltage for different OWTENGs"

Fig. 8

(a) Variations of peak short-circuit current with wind speed for OWTENG-A; (b)–(d) time-history curves of short-circuit current for OWTENG-A at varying wind speeds of (b) 2.50 m/s, (c) 4.34 m/s, and (d) 6.23 m/s when θ=0° (color online)"

Fig. 9

(a) Variations of total charge transfer with wind speed for OWTENG-A; (b)–(d) time-history curves of charge transfer for OWTENG-A at varying wind speeds of (b) 2.50 m/s, (c) 4.34 m/s, and (d) 6.23 m/s when θ=0° (color online)"

Fig. 10

Variations of (a) peak and (b) RMS voltages of OWTENG-A with external resistance at wind speed of 5.72 m/s; variations of (c) peak and (d) average powers of OWTENG-A with external resistance (color online)"

Fig. 11

Variations of (a) RMS voltage and (b) average power of OWTENG-A connected to 100 MΩ resistor with wind speed for different wind directions; contour maps of (c) RMS voltage and (d) average power of OWTENG-A connected to 100 MΩ resistor for different wind directions and wind speeds (color online)"

Fig. 12

Time-history curves of voltage across 100 MΩ resistor linked to OWTENG-A at varying wind speeds when θ=0° and 60°: (a) 2.50 m/s; (b) 4.34 m/s; (c) 6.23 m/s; (d) 8.44 m/s (color online)"

Fig. 13

(a) Variations of vertical (z-direction) and horizontal (x-direction) components of sphere's vibrational amplitude with wind speed for wind direction of 60°; vibration process of sphere with wind direction of 60° when wind speed is (b) 6.23 m/s and (c) 8.84 m/s (color online)"

Fig. 14

Open-circuit voltage waveform for OWTENG at wind speed of 5.72 m/s over 7 000 s (color online)"

Fig. 15

Variations of voltage charged by OWTENG for (a) various capacitors at wind speed of 3.93 m/s and (b) various wind speeds when charging 10 µF capacitor (color online)"

Fig. 16

Schematics of designed OWTENG powering approximately 100 LEDs (color online)"