Electromechanical Energy Conversion Jb Gupta Pdf 40

Abstract:Among the various forms of natural energies, heat is the most prevalent and least harvested energy. Scavenging and detecting stray thermal energy for conversion into electrical energy can provide a cost-effective and reliable energy source for modern electrical appliances and sensor applications. Along with this, flexible devices have attracted considerable attention in scientific and industrial communities as wearable and implantable harvesters in addition to traditional thermal sensor applications. This review mainly discusses thermal energy conversion through pyroelectric phenomena in various lead-free as well as lead-based ceramics and polymers for flexible pyroelectric energy harvesting and sensor applications. The corresponding thermodynamic heat cycles and figures of merit of the pyroelectric materials for energy harvesting and heat sensing applications are also briefly discussed. Moreover, this study provides guidance on designing pyroelectric materials for flexible pyroelectric and hybrid energy harvesting.Keywords: pyroelectric materials; thermal energy harvesters; flexible

The most common method to induce voltage generation is the use of mechanical vibrations [19]. This energy form can be easily found in everyday life, i.e., household appliances, vehicle movement, etc. The most typical vibrations with the highest amplitudes occur every day for frequencies lower than 100 Hz. To use these energy sources in the most efficient way, it is essential to construct devices to convert vibration energy within this frequency range. Smart textiles and wearable nanogenerators are other branches in which piezoelectric and triboelectric nanogenerators may be successfully and efficiently use. They may be fabricated based on rayon, cotton, or wool [20,21,22], as well on SbSI nanowires [23]. Recently, there is a growing demand for these kinds of energy sources. They should allow converting the energy of human movement into the electrical energy to supply and charge mobile electronics in the future. Electrical, mechanical, and thermal properties were measured for textiles coated with nanomaterials and were found to be important for the performance of smart textiles [24].

Recently, there is a growing interest in nanogenerators and nanosensors which are fabricated based on SbSI nanowires [23,26,27,28,29,30,31]. SbSI is a semiconductor and ferroelectric material exhibits very good electromechanical (k33 = 0.9) [32] and piezoelectric (d33 = 650 pC/N) properties [33]. Because of the huge values of the mentioned parameters, sensors based on SbSI are competitive to sensors made of other materials.

Preliminarily conducted research shows that the application of the external electric field allows SbSI nanowires aligning which should improve the piezoelectric response of the composite due to anisotropy of piezoelectric modulus and electromechanical coefficient of SbSI nanowires. Besides, it can also be one of a possible solution to the conglomeration issue.

Energy autonomy is key to the next generation portable and wearable systems for several applications. Among these, the electronic-skin or e-skin is currently a matter of intensive investigations due to its wider applicability in areas, ranging from robotics to digital health, fashion and internet of things (IoT). The high density of multiple types of electronic components (e.g. sensors, actuators, electronics, etc.) required in e-skin, and the need to power them without adding heavy batteries, have fuelled the development of compact flexible energy systems to realize self-powered or energy-autonomous e-skin. The compact and wearable energy systems consisting of energy harvesters, energy storage devices, low-power electronics and efficient/wireless power transfer-based technologies, are expected to revolutionize the market for wearable systems and in particular for e-skin. This paper reviews the development in the field of self-powered e-skin, particularly focussing on the available energy-harvesting technologies, high capacity energy storage devices, and high efficiency power transmission systems. The paper highlights the key challenges, critical design strategies, and most promising materials for the development of an energy-autonomous e-skin for robotics, prosthetics and wearable systems. This paper will complement other reviews on e-skin, which have focussed on the type of sensors and electronics components.

Multi-sensing and flexible electronic skin for robots and humans. 3D schema of a flexible e-skin with multiple electronic components (sensors, electronics, memory, energy harvesters, etc.) distributed a along the same surface or b stacked. Reprinted with permission from Dahiya et al.211 Copyright © 2015, IEEE. The e-skin self-powered by c a bulky battery (reprinted with permission from Leonov et al.54 Copyright © 2009, AIP Publishing) or d, e a light-weight wearable solar cell. Reprinted with permission from García Núñez et al.1 Copyright © 2017, John Wiley and Sons. Reprinted with permission from Bauer et al.3 Copyright © 2013, Springer Nature. f iCub robotic body and arm covered with e-skin (see inset). Reprinted with permission from Cannata et al.49,53 The 3D reconstruction of a skin patch placed on g a container, and h a KUKA LWR arm. Reprinted with permission from Dahiya et al.50 Copyright © 2013, IEEE. i Image of the prosthetic/robotic hand with e-skin.8

Currently, the energy requirements of e-skin are met with bulky batteries or energy harvesters (Fig. 1c) that do not always produce sufficient energy, and also affect the portability and overall wearability of the e-skin. The batteries offer a limited life span and short charging/discharging cyclic stability and durability, risky over-heating effects, and are often heavy.26 Because of the need, and currently the lack of suitable solutions, significant efforts have been devoted during the last decades to develop alternative solutions such as light-weight e-skin (Fig. 1d) with wearable energy harvesters (e.g. photovoltaics, thermo-electricity, piezo-electricity and tribo-electricity1,27) and energy storage devices (e.g. flexible batteries (Fig. 1e)28,29 and supercapacitors30). Considering the key role of energy, this paper focuses on the e-skin requirements and potential solutions with integrated energy harvesting/storing technologies. Among all potential energy sources, light, thermal and mechanical energies, have demonstrated excellent performance for powering e-skin due to abundance in the environments where the e-skin could be used. In addition, the chemical energy from various human body fluids (e.g. tears, saliva, sweat, etc.) and biofuels are attracting interest as promising energy sources for powering e-skin in wearables.31,32,33,34 The progresses in the field of energy-harvesting technologies include the fabrication of energy harvesters on rigid as well as non-conventional flexible/stretchable substrates, e.g. stretchable PV cells,35 light thermocouple energy generators,36 or flexible triboelectric energy nanogenerators.37 In this regard, the future of e-skin is sometimes subjected to the success of energy harvesters and storage technologies developed on flexible/stretchable substrates. The performance of some of the above technologies is still far from the requirements for fully autonomous e-skin, i.e. an e-skin that can work continuous for 24 h with high stability and reliability. Low power conversion efficiency of technology developed on flexible substrates and discontinued energy supply are the two main drawbacks observed in energy harvesters based on light, mechanical and thermal energies. Although there are already some examples of continuous powering of e-skin,38 the latest progress reported on multi-sensing e-skin7,39 and the reduction of the sensors and electronics size,16,40,41,42 have drastically increased the energy requirements for this technology. Therefore, current challenges on energy-autonomous e-skin are not focused only on the discovery of new sources of energy (e.g. chemical and electrochemical energy43) and high-efficient energy-harvesting mechanisms (e.g. triboelectrics44,45,46,47), but also on the integration of different energy harvesting and storage technologies, resulting in a portable power pack.38,48

Energy-autonomous electronic skin: potential energy sources. The schematic diagram of self-powered e-skin, comprising: (i) energy harvesting (light, mechanical, chemical and thermal energy), (ii) energy storage (batteries and supercapacitors) and (iii) examples of self-powered e-skin solutions. Energy harvesting: the illustration compiles the best performance energy harvesters and their corresponding energy outcome (i.e. power density) depending on the energy source (light,66,73,81 mechanical,98,103 chemical32,33 and thermal energy133,137), highlighting successful devices exhibiting features including stretchability, lightweight, output powers and wearability. Energy storage: highlighting various flexible active electrodes that enhance the performance of LiBs169,220,221,222 and textile/fibre/cloth-based supercapacitors223,224,225,226,227 for wearable systems. Examples of self-powered e-skin solutions: the illustration shows representative examples of electronic devices continuously self-powered by various energy sources, including tactile e-skin for robots self-powered by sunlight (reprinted with permission from García Núñez et al.1 Copyright © 2017, John Wiley and Sons), e-skin self-powered by a biofuel cell and integrated on a contact-lens (reprinted with permission from Falk et al.34 Copyright © 2012 Elsevier B.V), wearable sensors self-powered by thermoelectric generators (reprinted with permission from Leonov et al.54 Copyright © 2009, AIP Publishing), wearable e-patch for human health monitoring (reprinted with permission from Yang et al.55 Copyright © 2009, American Chemical Society), multi-sensing e-skin on fabrics self-powered by piezoelectric generators (Reprinted with permission from Li et al.56 Copyright © 2016, Springer Nature) 2b1af7f3a8