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Startup hopes energy harvested from the air will power smart homes and wearables

A new technology called Freevolt converts the babble of radio waves into electrical power that can run wireless sensors and other devices.

Drayson Technologies

LONDON -- With smartphones and Wi-Fi everywhere, the air today is saturated by radio waves. A British startup hopes to capitalise on that, converting radio's ambient energy into small but useful amounts of power for electronic devices.

The technology, called Freevolt, can harvest that energy to run low-energy devices such as sensors and beacons so their wireless communication ability is matched by a wireless power supply, too. A British company called Drayson Technologies unveiled the Freevolt harvester -- a device the length and width of a mobile phone but the thickness of a credit card -- at an event here on Wednesday.

Freevolt could help smooth the way to a future in which computing brains are infused into everything from tea kettles and cats to trash cans and cars. This idea, called the Internet of Things, will link billions of devices and, according to analyst firm International Data Corp., lead to an immense $1.7 trillion in spending worldwide by 2020.

Radio isn't the only energy source for energy harvesting. Other designs take advantage of acceleration forces, temperature differences, sunlight and differences in chemistry. One example: A rotating car wheel provides enough force to power a sensor that gauges tyre pressure and sends the information to the car's computer control system.

Sensors and wireless communication abilities will help us locate our pets and tell us whether it's time to put the bins out. Freevolt allows such sensors to run without us needing to plug it in or change its batteries, the company said.

"Companies have been researching how to harvest energy from Wi-Fi, cellular and broadcast networks for many years," said Paul Drayson, chief executive and chairman of Drayson Technologies. "But it is difficult, because there is only a small amount of energy to harvest and achieving the right level of rectifying efficiency has been the issue."

To overcome this challenge, Drayson Technologies had to develop a method to make these small amounts of energy it harvested usable, and to do so without losing any of that energy in the process. Three major technological breakthroughs ultimately allowed the company to achieve this.

The first was a multi-band antenna that can harvest energy across a wide spectrum of radio bands. The company has built an efficient version of a component called a rectifier that turns the energy into a current. And an optimised power management snatches every last bit of spare energy, "like a dog that picked up on a strong scent and will not let go of its target," Drayson said.

Drayson Technologies will license Freevolt to companies that want to build it into their products, but it has also built a £55 (about $85 or AU$120) wearable reference product called CleanSpace to demonstrate what's possible. It measures air quality and beams that information to a smartphone with a Bluetooth radio link so people measure carbon monoxide exposure as they move around. The device has a lifespan of three to five years, but this is only limited by the sensor, not by Freevolt itself.

For now Freevolt technology is technically pocket-sized, but Drayson Technologies is working on making it even smaller and more flexible so it could work better with compact wearable products. Limited battery life has so far been a major drawback of smartwatches and activity trackers, but with Freevolt tech built in, it's possible that one day we may not have to worry about constantly recharging them, the company hopes.

Similarly, the modules could be made larger to power multiple connected objects within a smart home. Unlike solar panels, which must be mounted outside, Freevolt could be built within walls -- as long as you don't mind it slurping up your Wi-Fi signal beamed across the house. "It's going to be really exciting to see what ideas people come up with," Drayson said.