Waste Mechanical Energy Harvesting (I): Piezoelectric Effect
Mechanical energy is one of the most ubiquitous energies that can be reused in our surroundings. The sources of mechanical energy can be a vibrating structure, a moving object, and vibration induced by flowing air or water. The energies related to induced
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Waste Mechanical Energy Harvesting (I): Piezoelectric Effect
2.1 Introduction Mechanical energy is one of the most ubiquitous energies that can be reused in our surroundings. The sources of mechanical energy can be a vibrating structure, a moving object, and vibration induced by flowing air or water. The energies related to induced vibrations or movement by flow of air and water at large-scale are wind energy and hydroelectric energy, respectively, which are not within the scope of this book. Instead, the mechanical energies here can be classified as so-called ‘‘low-level’’ vibrations and movements. Such potential ‘‘low-level’’ vibrations and movements are summarized in Table 2.1 [1] and Table 2.2 [2]. Mechanical waste energies usually can be harvested by using vibration-toelectricity conversion [2–4]. The most distinguished characteristic of this kind of waste energy harvesting is initially identified for low power generations. Therefore, one of the targeted applications is to power small electronic devices. However, recent development indicates that it can also be used for large-scale applications [5].Vibration-to-electricity conversion can be realized through three basic mechanisms, including electromagnetic [6–8], electrostatic [9], and piezoelectric [10, 11] transductions. Among the three mechanisms, piezoelectric transduction has received the greatest attention. This is because piezoelectric materials have larger power densities and higher feasibility for practical applications than the materials used in the other two mechanisms [3]. For example, voltage outputs in electromagnetic energy harvesting are typically very low and thus must be amplified to a level sufficiently high to charge storage devices. In contrast, however, piezoelectric energy harvesters output voltages that can be used directly. In electrostatic energy harvesting, the materials should be subject to an external applied voltage to trigger the relative vibratory motion of the capacitor elements, which outputs alternative electrical currents [9]. Such external applied voltages are required in piezoelectric energy harvesting. Another advantage over electromagnetic devices is that piezoelectric harvesting devices can be fabricated at both macro-scale and micro-scale, due to the well-established deposition techniques for thick-films and thin-films piezoelectric L. B. Kong et al., Waste Energy Harvesting, Lecture Notes in Energy 24, DOI: 10.1007/978-3-642-54634-1_2, Springer-Verlag Berlin Heidelberg 2014
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2 Waste Mechanical Energy Harvesting (I)
Table 2.1 Sources of mechanical energy around us each and every day that can be harvested for electricity [1] Human body/motion Transportation
Infrastructure
Industry
Breathing, blood Aircraft, Bridges, roads, Motors, flow/pressure, automobile, tunnels, farm, compressor, exhalation, train, tires, house structure, chillers, walking, arm tracks, peddles, control-switch, pumps, fans, motion, finger brakes, turbine water/gas pipes, vibrations, motion, jogging, engine, AC system cutting and talki
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