The very idea: Kitchen gadgets powered by microwave leaks

Sep 22, 2013 by Nancy Owano weblog
Credit: Yoshihiro Kawahara et al.

(Phys.org) —Can your microwave oven power other gadgets in your kitchen? That is the question explored in the paper, "Power Harvesting from Microwave Oven Electromagnetic Leakage," by researchers from the University of Tokyo in Tokyo and Georgia Institute of Technology in Atlanta. They presented their work at the Conference on Ubiquitous Computing in Zurich earlier this month. "In this paper," said Yoshihiro Kawahara, an associate professor in the field of ubiquitous computing at the University of Tokyo. and colleagues, "we present the feasibility of harvesting and storing a small amount of leaked energy from a microwave oven and operate low-power devices without battery in a domestic environment."

Their experiment actually did show that it was possible to from the microwave and use it for other appliances. "Our experimental results showed that the leakage received by a was about 0 dBm (1 mW) at a point 5 cm in front of the door. A rectenna consisting of a dipole antenna and charge pump can convert the leaked into a DC current. When a microwave oven is operated for 2 min, 9.98 mJ of energy was harvested."

[A is an antenna which is used to convert microwave energy into direct current electricity.]

They demonstrated that this energy was enough. They said, "The energy accumulated over 2 min was found to be suf?cient for the operation of some of low-power kitchen tools for a few minutes and operate wireless for 2.5 hours."

Reporting on their work, Scientific American noted that "A microwave oven uses a device called a magnetron to generate electromagnetic waves with a wavelength of 12.5 centimeters and a frequency of 2.4 gigahertz – enough for vibrating to heat food. Although a waveguide delivers the microwaves into the food chamber some still escape through the gap around the oven door and through the metal-meshed window."

In the bigger picture of power consumption today, the authors noted that, because of the reduced power consumption of electronics devices, quite a few battery-operated devices such as kitchen tools only consume a few dozen microwatts. The reduced power requirements are accelerating power harvesting from various ambient energy, they wrote. " As energy ef?ciency continues to improve, the energy requirements to power electronic devices will continue to drop; this in turn means it is feasible to power more devices by a small amount of energy of about a few dozen microwatts."

Authors of the paper are Yoshihiro Kawahara, Xiaoying Bian, Ryo Shigeta, Rushi Vyas, Manos M. Tentzeris and Tohru Asami. The paper appears in UbiComp 13 Proceedings of the 2013 ACM International Joint Conference on Pervasive and Ubiquitous Computing.

Explore further: Desktop device to make key gun part goes on sale in US

More information: Power harvesting from microwave oven electromagnetic leakage: dl.acm.org/citation.cfm?id=2493500
www.ubicomp.org/ubicomp2013/program.php
www.newscientist.com/article/d… kitchen-gadgets.html

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User comments : 19

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Pressure2
1.4 / 5 (10) Sep 22, 2013
How can a 12.5 centimeter wavelength get through the 1 millimeter holes on the door? The waves of particles theory of light can explain this.
antialias_physorg
3.7 / 5 (3) Sep 22, 2013
How can a 12.5 centimeter wavelength get through the 1 millimeter holes on the door?

Erm...you do know that 'wavelength' does not refer to an actual up-and-down (wavey) motion, right?

And even if it did that the one is longitudinal, while a 1mm hole is transversal to the line of flight, right?

Just checking...
baudrunner
1.4 / 5 (10) Sep 22, 2013
"How can a 12.5 centimeter wavelength get through the 1 millimeter holes on the door? The waves of particles theory of light can explain this."
That's probably not a serious question (I hope)@antialias_physorg: you could have just said that photons are small enough to pass between molecules.
Pressure2
1 / 5 (7) Sep 22, 2013
http://en.wikiped...collapse

"The cluster of phenomena described by the expression wave function collapse is a fundamental problem in the interpretation of quantum mechanics, and is known as the measurement problem. The problem is deflected by the Copenhagen Interpretation, which postulates that this is a special characteristic of the "measurement" process."
Pressure2
1 / 5 (8) Sep 22, 2013
"Even though you can see into the microwave oven when your food is cooking, the microwaves are effectively blocked from getting out into the room because the holes in the metal screen on the microwave oven door are about 1 mm in diameter compared to a 120 mm wavelength for the microwaves. The wavelength of the microwaves is about 120 times the size of the holes, and can't "see" the holes to get out. This is an application of the fact that you cannot image anything that is smaller than the wavelength of the radiation you use to image it. You can see through the holes because at 500 nm wavelength, the light wavelength is about 2000 times smaller than the holes."

http://hyperphysi...ven.html
MR166
1.4 / 5 (10) Sep 22, 2013
Just another research paper that is useless as teats on a bull.
Pressure2
1.5 / 5 (8) Sep 22, 2013
Just another research paper that is useless as teats on a bull.

Until you lose your eyesight looking into the microwave.
LarryD
not rated yet Sep 22, 2013
This is actually not a bad idea. Some years ago when living in England I remember that the heat from my microwave oven (side vents) was more than enough to warm a small glass of milk (over 10 mins or so) but I couldn't drink it. The milk had 'turned' a little and there was considerable amounts of dust floating on top. The dust was easy to explain but the suface 'turning' a bit, wasn't. I didn't think there was enough 'leaking' to do that...was I wrong?
nkalanaga
5 / 5 (1) Sep 22, 2013
The basic principle of the Faraday Cage is that radiation can't penetrate a conductor with holes smaller than the wavelength:
"Faraday cages cannot block static or slowly varying magnetic fields, such as the Earth's magnetic field (a compass will still work inside). To a large degree, though, they shield the interior from external electromagnetic radiation if the conductor is thick enough and any holes are significantly smaller than the wavelength of the radiation." Wikipedia

LarryD: If the door seals on a microwave oven are damaged, or the area the contact is unusually dirty, microwaves can easily leak, often at high enough intensity to cause problems. If the metal mesh in the door isn't grounded properly, such as a loose ground wire around the hinges, potentially dangerous amounts of energy can be lost.

In your case, since the milk was on the side, it probably was the heat, since the metal case SHOULD have blocked everything.
MR166
1 / 5 (9) Sep 22, 2013
"Until you lose your eyesight looking into the microwave. "

They have been manufacturing cheap meters that measure any leakage from microwave ovens for 50 years. This article has no scientific value at all!!!
nkalanaga
5 / 5 (2) Sep 23, 2013
Scientific? Maybe not. It seems to be more of an engineering-physics article, which qualifies as "applied sciences". "We know these things leak energy, now let's see if we can use that energy for a practical purpose". For those interested in doing, rather than just studying, this is a very interesting article.
nkalanaga
not rated yet Sep 23, 2013
deleted - double posted due to mouse malfunction.
tscati
1 / 5 (5) Sep 23, 2013
And in other news...

Scientists have discovered that the kinetic energy of a person jumping off a two-storey roof and hitting the ground is enough to power an electric lawn mower for 1.7 minutes.
antialias_physorg
5 / 5 (2) Sep 23, 2013
For those interested in doing, rather than just studying, this is a very interesting article.

Good call. Though I hope no one starts creating 'intentional leaks' in their microwave oven in order to increase the effect for some home experimenting.

Energy harvesting for wireless applications is a hot topic in research, after all.
alfie_null
not rated yet Sep 23, 2013
For those interested in doing, rather than just studying, this is a very interesting article.

Good call. Though I hope no one starts creating 'intentional leaks' in their microwave oven in order to increase the effect for some home experimenting.

Energy harvesting for wireless applications is a hot topic in research, after all.

Ouch.
MR166
1 / 5 (8) Sep 23, 2013
"We know these things leak energy, now let's see if we can use that energy for a practical purpose."

Sorry to burst your bubble but a solar cell that collects energy from the microwave oven light light would produce more power than this device.
Msafwan
1 / 5 (4) Sep 26, 2013
I am furious that people vote 1 for right comment and 5 for WRONG comment.

"Big wave can't go thru smaller hole" -This is correct. WHY vote this comments only 1 star?!
"Light is not actually a wavy motion of an electric field"- This is blatant FALSE (light IS an actual wave in space). WHY did people vote a person who dispute basic principle with 5 star?!

WHO is this people who vote actually? They should be humbler and go read some books and stop voting for wrong stuff.
antialias_physorg
5 / 5 (1) Sep 27, 2013
Sorry to burst your bubble but a solar cell that collects energy from the microwave oven light light would produce more power than this device.

Nope, because the energy of the photons is far too small to make anything like a PV cell work with this. You need an antenna for optimal capture. And that's exactly what they got here.
shpilk
not rated yet Sep 28, 2013
You can get 'free electricity' by simply making an antenna and rectifying any RF soup through a diode. The closer you are to a transmitter, the more signal you'll have.

If you think it's impractical, you might want to read this.

rfidjournal.com/articles/view?4613