Feeds

RADIATION SNATCHED from leaky microwave ovens to power gadgets

Sudden explosion in meals-for-one predicted (by no one)

Secure remote control for conventional and virtual desktops

A collaboration between universities in Tokyo and Atlanta has spawned a device for harvesting power leaked from domestic microwave ovens – turning wasted waves into free energy.

Microwaves pump out energy in the 2.4GHz band: the industrial, scientific and medical (ISM) radio space popularised by Wi-Fi and Bluetooth. The casing of the oven contains almost all the energy used to heat the "meal for one", but some escapes to interfere with nearby wireless networks and that's the energy scooped up by the boffins and their new circuit.

The electronics in their microwave "rectenna" consists of an antenna, a diode and a capacitor, we're told. The incoming waves induce a tiny voltage across the antenna's terminals; the other components rectify and step up the voltage to a mighty 1.8V, enough for most gadgets.

The process

Harnessing microwaves ... how the tech works

Domestic microwave ovens are governed by regulations that restrict their leakage to five milliwatts per square centimetre, at a distance of five centimetres, as New Scientist explains. The researchers discovered leakage was well below that across the brands they tested, but were able to harvest a good proportion of that power to run kitchen appliances including a thermometer and countdown timer.

Equally interesting, to this correspondent at least, was the range of frequencies in which the tested ovens operated. According to the published study [PDF, readable up to page five] an oven from Sharp will blank out Wi-Fi in channel 7, while one from Whirlpool will only affect wireless networks in the top few slots (10 & 11), which could matter to some.

But the point of the project was to see if useful energy could be extracted from the stray radiation, and the conclusion was that it could. A low-power device could run happily on the harvested power, and a wireless sensor could be charged to run for hours from a two-minute burst of microwaves, all from energy that would otherwise be wasted.

It's not the first attempt to harvest energy from radio, as Yoshihiro Kawahara and his fellow boffins note. We've reported on energy harvested from TV signals and RFID transmissions, but those have side effects or use deliberately generated signals, while the leaks from a microwave oven are literally wasted without intervention.

How useful it is to harvest them is debatable: the energy is only there when the microwave is in use, and while most homes might indeed have a microwave oven, it may not be in use all that often, but practicability isn't what this kind of research is about. The question is "how"; "why" comes later. ®

Next gen security for virtualised datacentres

More from The Register

next story
Vulture 2 takes a battering in 100km/h test run
Still in one piece, but we're going to need MORE POWER
TRIANGULAR orbits will help Rosetta to get up close with Comet 67P
Probe will be just 10km from Space Duck in October
Boffins ID freakish spine-smothered prehistoric critter: The CLAW gave it away
Bizarre-looking creature actually related to velvet worms
CRR-CRRRK, beep, beep: Mars space truck backs out of slippery sand trap
Curiosity finds new drilling target after course correction
China to test recoverable moon orbiter
I'll have some rocks and a moon cheese pizza please, home delivery
What does a flashmob of 1,024 robots look like? Just like this
Sorry, Harvard, did you say kilobots or KILLER BOTS?
NASA's rock'n'roll shock: ROLLING STONE FOUND ON MARS
No sign of Ziggy Stardust and his band
Why your mum was WRONG about whiffy tattooed people
They're a future source of RENEWABLE ENERGY
Vulture 2 spaceplane autopilot brain surgery a total success
LOHAN slips into some sexy bespoke mission parameters
prev story

Whitepapers

5 things you didn’t know about cloud backup
IT departments are embracing cloud backup, but there’s a lot you need to know before choosing a service provider. Learn all the critical things you need to know.
Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Build a business case: developing custom apps
Learn how to maximize the value of custom applications by accelerating and simplifying their development.
Rethinking backup and recovery in the modern data center
Combining intelligence, operational analytics, and automation to enable efficient, data-driven IT organizations using the HP ABR approach.
Next gen security for virtualised datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.