Pyroelectric nanogenerators in energy technology

Abstract

[Excerpt] International crisis such as global warming, environmental pollution, and e-waste significantly increased the demand of electronic devices powered by renewable and sustainable energy sources [1, 2]. It is known that batteries are key renewable energy sources for powering electronic systems, which suffer from drawbacks like environmental issues, limited life-time, weight, and periodic maintenance or replacement [3]. Therefore, energy harvesting from the most reliable sources such as green energy (solar, wind, biomass, and hydrogen) and mechanical energy (water flow, mechani cal vibrations, and human motions) are inevitable. In our daily life, different forms of energies like thermal, mechanical, and photovoltaic are scattered around or wasted. Thus, commercialization of wasted energy into electrical energy has become imperative to build a clean and sustainable world [4, 5]. Moreover, thermal energy exists everywhere in the form of sun light, wind, human body, etc. [6–8]. For instance, our human body is an indispensable source of thermal energy, and we are simply wasting it without knowing the importance. However, harvesting of electrical energy from thermal energy requires a thermal fluctuation or temperature gradient. For instance, the human respiration and locomotion create fluctuations in the thermal energy and can be converted into electrical energy [7, 8]. The process of generating electrical energy using the temperature gradient is known as pyroelectric effect or pyroelectricity [8]. Besides, the pyroelectric materials can gener ate electrical energy from the temperature fluctuations induced due to small-scale physical changes. These pyroelectric materials that can generate electrical energy using small physical-change induced thermal fluctuation are known as pyroelectric nanogenerators (PENGs). Converting such a feasible energy source to electrical energy using PENGs under ambient conditions is of great impor tance for long-term self-powered energy systems. Figure 9.1 illustrates the schematic representation of various applications of PENGs. [...]