Power to go

More and more powerful batteries and increasingly ­innovative ways of charging them are emerging onto the market. The charger cable is likely to soon be a thing of the past.

Power is essential to wearables, too, of course. The demands in terms of energy storage in wearables are unusual, however: the systems not only have to be light and small, they also have to be encapsulated to protect against ambient effects and need to be charged frequently owing to the diversity of integrated electronic components. At present, lithium-ion batteries are the most popular energy storage systems. According to Lux Research, it is a technology which still has a lot more potential to offer: in ten years’ time, batteries will run for five times longer than today and their energy density will be double at more than 400 watt-hours per kilogram. And new battery types will also be developed: solid-state batteries, especially, will play a key role in future – the analysts at Lux Research predict they will have a 39 per cent market share by 2035. The advantages of solid-state energy storage systems include the ability to be recharged very frequently. The micro-energy cell from Thinergy, for example, is rated for 100,000 charge cycles. Energy stores of this kind are thus ideal for applications in conjunction with energy harvesting.

Energy from the environment

Energy “harvesting” means drawing power from the surrounding environment, from sources such as ambient temperature, motion or the sun. As one example, a team of scientists at the Korean Institute of Science and Technology has developed a small, flexible thermo-electric generator which utilises the wearer’s body heat to generate electricity. The Ampy draws power from a different source: the compact device can be fastened to the arm, leg or hip, where it converts the wearer’s kinetic energy into electricity and then stores it. Users can then connect their smartphone to the Ampy to recharge its battery.

Cable-free charging

Wearables incorporating induction-charged batteries work without any physical connection to charge their battery. All the owner has to do is place the device on an electromagnetic transmitter coil which generates an alternating magnetic field. When the receiver coil built into the wearable is brought close to the alternating field, electricity is generated. There are currently three competing standards for cable-free charging: Qi, Rezence and Powermat. The fact that this is no mere future dream is illustrated by a news release from Ikea: in early 2015, the furniture store chain launched a collection incorporating a cable-free charging function based on the Qi standard.

(Picture credits: Shutterstock)

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