9 - Power supply sources for smart textiles

Abstract

This chapter presents work towards alternative power supplies for smart textiles that avoids the use of conventional rigid batteries. Energy harvesting concerns the capture of ambient energy present in the environment and the conversion of this into electrical power. Such harvested energy can be used to power smart textiles directly or the energy can be stored in textile supercapacitors or batteries for use when required. The chapter considers a range of energy harvesting techniques that have been implemented in textile form together with an overview of textile batteries and supercapacitors. The energy harvesting techniques presented include capturing mechanical energy from physical movement using piezoelectric or ferroelectret materials or the triboelectric effect. Wireless power transfer (WPT) techniques that include near-field resonant inductive coupled systems can be used to transfer considerable amounts of energy over short ranges. Alternatively, far-field radio wave-based devices can be used to harvest either ambient or deliberately broadcast signals over longer distances. Harvesting solar energy can be achieved by integrating photovoltaic cells on, or in, yarns or by fabricating them on the surface of the textile. Thermal energy can also be harvested using thermoelectric yarns or films although the power levels demonstrated to date are very small. The textile structure makes an excellent mechanical scaffold for energy storage devices and several textile supercapacitors and batteries have been demonstrated with good energy storage properties. Working with textiles is challenging and whilst these techniques show great promise, they are not yet a practical proposition for real-world applications. WPT techniques are arguably the closest to becoming practical and have already been combined with textile supercapacitors to present a prototype textile power module.