The energy-harvesting textile woven with colored wool. Image: Nature Energy
A few summers ago I was living in a tent in the high desert of far southwestern Colorado. In terms of weather, there were two things that defined the locale: wind and sun. Both were relentless, and I can still hear the sharp whapping and billowing of nylon subjected to the same wind gusts that had been filing smooth the redstone of the Colorado Plateau for many thousands of years.
Living in a tent in the desert is a bit paradoxical for a technology journalist. You wind up spending a lot of time at the library in town charging devices.
Some future version of me might not have to go through the hassle, however. Engineers are developing fabrics that can harvest not just solar energy, but mechanical energy as well. The material of the tent itself could be purposed as a portable wind farm, with all of that whapping and billowing being converted into voltage to charge portable electronics and beyond. Indeed, just such a textile is described in this week's issue of Nature Energy by engineers at the Georgia Institute of Technology, Chongqing University, and the Chinese Academy of Sciences.
"Here, we present a foldable and sustainable power source by fabricating an all-solid hybrid power textile with economically viable materials and scalable fabrication technologies," explain Georgia Tech nanomaterials scientist Zhong Lin Wang and colleagues. "Based on lightweight and low-cost polymer fibres, the reported hybrid power textile introduces a new module fabrication strategy by weaving it in a staggered way on an industrial weaving machine via a shuttle-flying process."
"Colourful textile modules with arbitrary size and various weaving patterns are demonstrated."
The materials demonstrated by Wang and his team are both breathable and robust, while allowing for enough motion to make them good candidates for wearable electronics. A human walking in sunlight wearing a 4 cm by 5 cm section of the material is capable of generating an average output of around .5 mW. Given human biomechanical movement such as hand-shaking, the material could power a commercial capacitor with up to 2 volts per minute.
You can see the structure of the fabric below. It basically just consists of solid photovoltaic elements woven together with copper electrodes and a material acting as a triboelectric nanogenerator—that is, a device capable of converting certain frictional forces into electric charge, a la static electricity. (Wang is a leading figure in triboelectric nanogeneration research, generally.)
"It is worth noting that the hybrid power textile is not limited to wearable applications," Wang and co. write. "It can also act as a piece of flag, harvesting energy from sunlight and ambient wind blowing, and the delivered power is also capable of charging personal electronics as well as driving electrochemical reactions for self-powered water splitting. In addition, the hybrid power textile was also demonstrated to generate power from weak sunlight and wind from a moving car in a city location on a cloudy day, which also indicates its decent capability of working even in a harsh environment."
The study emphasizes several times that the new material is robust and all but ready for integration into industrial textile production processes. It could be something we wear or use for shelter or fly on a flagpole, but the textile can also be scaled up as well, offering power generation at a much larger capacity. Will the energy future include hillsides covered over in parachute power generators? For now I'll settle for a charged phone.