News analysis: Powering the Internet of Things with radio waves

The demand for cheap, clean energy has never been higher. So rejoice that sometime soon you may be able to ditch your batteries and power your devices using ‘thin air’.

The idea of free, perpetual energy may sound like a fantasy, but this is exactly what research and development company Drayson Technologies recently unveiled at the Royal Institution in London.

The technology, called Freevolt, works by harvesting radio frequency (RF) energy from existing wireless and broadcast networks and converting the energy into usable electricity.

How does it work?

The device harvests energy using a multi-band antenna, which locates RF energy from any source, within the 0.5–5GHz range, including mobile and TV signals. The signal is then fed through a rectifier that converts the waves into standard DC electricity, which can then be used to power other devices.

While the concept of powering devices in this way isn’t exactly new – in fact crystal radios harnessed this power back in the early 20th century – it has proved to be somewhat impractical and costly in the past.

Over the years many companies have tried, and failed, to find an efficient way of harvesting energy in this way. In 2009 Nokia announced that it was working on a prototype for a radio-wave-powered mobile phone. The simple fact that we are still plugging our mobile phones into the mains suggests that this one didn’t quite pan out.

Until now most successful attempts at developing devices charged by radio waves have been somewhat limited in scope, requiring the use of dedicated transmitters that power devices at short ranges. An example of this is PoWiFi, a device developed at the University of Washington, which tricks wireless routers into transmitting a constant wireless signal that can then be converted to DC power using a harvester and used to power low-energy devices nearby.

Freevolt differs in that it is the first commercially available technology that powers devices using RF energy with no dedicated transmitter required – meaning that devices can be charged anywhere, simply using RF waves that exist all around us.

According to Lord Drayson, CEO of Drayson Technologies, the technology is truly a world first, as it can be implemented without any costly set up fees.

“It doesn’t require any extra infrastructure, it doesn’t require us to transmit any extra energy, it’s recycling the energy which isn’t being used at the moment,” he said.


Those of you hoping to be able to ditch your mobile phone chargers for good might have to hold on for a while, as Freevolt is currently only capable of powering low-energy devices.

Low-energy doesn’t have to mean low-impact though – with the rise of the so-called ‘Internet of Things’ (IoT) the market for such devices has never been bigger.

According to Drayson Technology, Freevolt has the potential to become the power source for the IoT, allowing all such devices, such as wearables and sensors, to operate without being plugged in. To get the ball rolling, the company will soon offer investors the opportunity to purchase a Freevolt development kit.

While it waits for investors to jump on the Freevolt bandwagon Drayson Technologies has come up with an application of its own, the CleanSpace Tag – a personal air pollution sensor that is completely powered by Freevolt.

The CleanSpace tag is a portable device used to measure air quality on the go. The device transmits data onto a mobile app, allowing users to check how much carbon monoxide they have come into contact with, and view pollution levels across the country.

While the CleanSpace tag is about the size of a smartphone, Freevolt itself is scalable, meaning that it can be made bigger or smaller to suit a range of uses. However, the amount of energy harvested is proportionate to the size of the harvesting antenna – so bigger devices mean more energy.

Potential issues

Of course as with any new devices, there are potential problems that could arise.

While radio waves are freely available around us all the time they already have a very important use – to send data. Could harvesting energy in this way theoretically interfere with transmission?

The public definitely seem to have this concern. Technology sites reporting on the device’s release have seen a host of comments from tech enthusiasts concerned by the possible consequences such a device might have.

In response Drayson Technologies has assured that Freevolt does not interfere with data connectivity, or require any increase in transmission power. Freevolt is not designed to be disruptive, and on a small scale the effect of Freevolt device has on a wireless signal is tiny.

Dr John Batchelor, energy-harvesting and antenna specialist at the University of Kent, further echoes this sentiment: “It's unlikely they will interfere with other devices in the sense that they will produce spurious interfering signals,” he says. “The devices will take energy out of a signal wave front that hits the antenna, but this is a tiny proportion of the whole power available. They will take energy from a received signal with as much effect as your ears take energy from a passing sound wave.”

However, it has been conceded that if the technology is misused or implemented on too large a scale, devices could end up disrupting wireless transmissions.

Issues of scalability

At the Freevolt launch Lord Drayson highlighted that one of the most exciting things about Freevolt was its scalability – suggesting that the device could in the future be further developed to fit into the brickwork of a house, to harvest energy in a way similar to solar panels.

While the potential for another method of producing clean household energy is very exciting, this is where further concerns about data interference arise. Is it conceivable that a house fitted with large-scale Freevolt devices could function as kind of Faraday cage, absorbing all the RF waves emitted by, for example, a wireless router, and causing the signal to drop within the house?

“If the RF harvester was scaled up to large areas, and it is very efficient, then it could cause signal shadows behind it.,” says Batchelor.

Signal disruption in itself is a big issue, but it also brings with it the potential for regulatory interference, as communications’ regulators such as Ofcom and the FCC specifically prohibit devices that cause interference to radio signals outside of limited wavelengths – such as that experienced when a mobile phone is placed too close to a radio.

Batchelor points out that while any wall could pose a reasonable chance of creating signal shadows, a Freevolt-enabled wall could prove slightly more problematic from a legal perspective: “Maybe one is accidental blockage and the other is theft?” he suggests. “Certainly intentionally disrupting a public communications system is a crime.”

Unfortunately, with the CleanSpace Tag not due to ship until November, and development kits currently only available for pre-order, it’s too soon to tell what effect even a small Freevolt device might have, and remains to be seen whether the devices will prove popular with the public.

“The Freevolt people have kept a lot of the technical detail back so it's difficult to be certain of what edge they’ve got,” says Batchelor. “What they claim is impressive and remains to be proven on a wide scale. The technology will only be viewed as successful by the users if it's highly reliable and useful enough to bother putting on every day.”

In this respect, Batchelor says, more research into the technology is definitely required. “Even if their harvesting is sufficient to power the sensors now, there will be a demand for more functionality in the devices in the future and that will require more power.”

Sign up to the E&T News e-mail to get great stories like this delivered to your inbox every day.

Recent articles