shows photographs of the self‐powered pressure system. Figure 2.24c presents four foams with different heights. The resistances of the elastic foam that was connected to the TENG can be changed with the diversification of the external forces, resulting in changes in the measured voltage, as shown in Figure 2.24d.
Figure 2.22 The wind‐driven self‐powered wireless smart temperature sensor. (a) Photographs of the temperature sensor. (b) Charging curve of a capacitor by using the TENG with a PMC. Photographs of the temperature sensor before (c) and after (d) being powered by the TENG.
Source: Reproduced with permission from Zhao et al. [61]. Copyright 2016, American Chemical Society.
Figure 2.23 The wind‐driven self‐charging Li‐ion battery. (a) Charging and discharging curves of the Li‐ion battery via the TENG. (b) Photograph of the self‐charging system. (c) Photographs of lighting up a green LED via the Li‐ion battery charged by the TENG.
Source: Reproduced with permission from Jiang et al. [69]. Copyright 2018, American Chemical Society.
Figure 2.24 The wind‐driven self‐powered pressure sensor. (a) Schematic diagram of the as‐fabricated self‐powered pressure sensor. (b) Photograph of the prepared pressure sensor. (c) Photograph of foams with heights. (d) The output voltage of the foam connected to the TENG.
Source: Reproduced with permission from Zhao et al. [77]. Copyright 2019, John Wiley and Sons.
2.4 Comparison
With the fast development of modern industry, energy shortage has become an important problem that restricts the further development of the human society. Conventional wind harvesters based on the electromagnetic effect have been created as one of the most important ways for harvesting wind energy. Recently, TENGs based on the cooperation of the triboelectric effect and the electrostatic induction have been used to harvest wind energy. Figure 2.25 shows the comparison between two wind harvesters, focusing on the mechanism, characteristics, and disadvantages [78]. Compared to conventional wind harvesters, TENGs can be considered as current sources with a large internal resistance, leading to characteristics of high voltage and low current. In addition, WD‐TENGs possess many advantages such as low cost, high efficiency, and easy fabrication, providing them the potential to be utilized as self‐powered electronics.
Figure 2.25 The comparison between conventional wind harvester and new wind harvester based on a triboelectric nanogenerator.
Source: Reproduced with permission from Chen et al. [78]. Copyright 2018, John Wiley and Sons.
2.5 Conclusion
With the development of wearable electronics and wireless sensors, WD‐TENG, which can convert wind energy to electrical energy, are researched not only to enhance output performance but also to improve compatibility with other electrical devices. It has become a new trend in the further development of self‐powered devices that harvest energy from surrounding environment.
The theoretical models and working mechanisms of current WD‐TENGs have been described in this chapter. The output performances of the TENGs can be improved by optimizing advanced structures and materials. Among the several structures, vibrating plate‐based structure, elasto‐aerodynamics‐based structure, and rotary‐driven mechanical structure are three popular structures. Some advanced materials, such as cellulose, superhydrophobic surfaces, and nanowires, have been used. Lastly, soma smart self‐powered devices based on WD‐TENGs are introduced to present wide application prospects.
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