Harvesting energy from the RF signals that surround us
Thanks to AlternativeSource.org for alerting me to this very cool story about Hawaii-based Ambient Micro LLC, which has developed a way of harvesting small amounts of power from the ambient radiowaves that surround us every day. The company calls its process the “recycling of radiowaste,” and it initially envisions its technology replacing batteries that would be used in smoke alarms, RFIDs and other sensor-dependent devices that consume very small amounts of power.
The story, which appeared in the Honolulu Star Bulletin, reports that Ambient Micro recently snagged a $100,000 (U.S.) research contract with the U.S. Air Force to develop a prototype power supply for sensors on tiny intelligence drones, or unmanned aerial vehicles.
“The emergency of ambient energy as a viable alternative power source is really driven by the advancements in semiconductor design,” company president Scott Weeker told the paper, though he admitted the technology wouldn’t collect nearly enough energy to power something like a laptop, let alone a car. But, he added, “Things that used to require watts of power are now running on milliwatts and will soon only require microwatts.”
According to the article, “Ambient Micro’s goal is to develop a tiny device that harvests not only photons (visible light and invisible electromagnetic radiation), but also converts sound waves, vibrations and hot-cold temperature differences into power.”
Cool.
So, it appears Nikola Tesla’s dream of wireless power transmission is alive and well. Mind you, Tesla envisioned massive amounts of electricity being transmitted through the air. Fact is, the idea of collecting small amounts of energy from radiowaves, or transmitting small quantities of power wirelessly over short distances, has been around for years. Splashpower Inc., for example, has a product today that lets you wirelessly charge cellphones and other small gadgets over extremely short distances — basically by resting the device on a charging pad. But Ambient Micro would take this idea to another level, by literally — and freely — plucking photons out of the surrounding environment.
It would be nice to see a replacement for small batteries made of toxic materials, and radiowaves — like the sun and wind — are all around us so might as well use them. As for creating power from hot-cold differentials, if this could be done couldn’t you then use geoexchange systems as a power source? Curious. And converting sound into electricity? Even more curious.
Anyway, an interesting development to follow, but it does raise this question: If you can turn stray cellphone signals into power, then are we really doing damage to ourselves by pressing these devices to our heads for hours each day? Freaky.
Tyler Hamilton is senior energy reporter and columnist for the Toronto Star, Canada's largest daily newspaper. In addition to this Clean Break blog, Tyler writes a weekly column of the same name that discusses trends, happenings and innovators in the cleantech market. This blog is a personal project started in April 2005. It is not an official blog of the newspaper. Tyler can be reached at tyler@cleanbreak.ca
April 11th, 2006 at 7:38 pm
Microphones produce electricity, perhaps we greens can finally harness the power of the media.
April 11th, 2006 at 7:49 pm
No, that’s hot air — but great for renewable thermal applications.
April 13th, 2006 at 12:50 pm
Cool idea but with a problem capturing RF. I remember a story about farmers in the midwest that wired their fences to lights in the barn, henhouse, etc. Energy from power lines passing over their property was being coupled into the fences and thereby helping keep the chickens laying. By the laws of physics, though, what power went into the light bulb was subtracted from what the power company could get out of the power lines at the far end, and when lots of people started doing it the courts ruled that this was stealing and made it illegal.
The same is physics holds true when picking up radio transmissions to power small electronic devices — put enough of them around sucking up RF and cell phones won’t reach as far, planes won’t pick up navigation signals, etc.
When this technology scales to large numbers it will run into problems. Once more, no free lunch.
April 13th, 2006 at 4:29 pm
I’m now 45. When I was a child I made a cat’s whisker radio that used the carbon rod from the core of a D-cell battery and a cat’s whisker. (Try Google Cat’s Whisker Radio, -then try getting a whisker from your cat!) It was tunable and powerful enough to provide baseball into an earbud taken from a transistor radio. No batteries needed, powered by the radiowaves themselves. I now have a set of modern military telephones, using 1940’s technology since they therefore have no electronics so are able to withstand a nuke blast’s emission pulse that would knock out sensitive electronics. (Not that I know what you’re going to say to each other at that point.) It too has no batteries, and is powered by voice alone. We tried hooking it up to a set of 1000 ft spools of wire, and it worked just fine through 3000 ft. Induction might have helped with that since it was unsheilded wire, but it is still impressive that voice power alone can shove a voltage that far. A low voltage at that.
March 26th, 2008 at 7:05 pm
Well I think you may be a little mistaken. The power that is being picked up by these devices is not draining or taking anything away from the power companies or radio stations. What is happening is leakage that isn’t being used by anyone. When a radio station broadcasts a signal the power used determines the distance it reaches not how many people can use it. If everyone on earth was in range of the same radio station powering out at 40 W they will all happily be able to listen in. The same principle can be recognized by large power line towers. Very large amounts of power are transmitted through the power lines and a resulting electromagnetic field is created which if picked up by some unshieled metal acting as an antenna is not taking anything away from the power company because that leakage has always been leaking and never got to the end user in the first place. The world works on leakage and friction so harnessing the waste makes the concept all the more incredible.
March 27th, 2008 at 2:43 pm
Transformers work by induction -leakage. The primary side, through proximity, induces current in the secondary side. Yes this is helped along by winding each around the other but one is transmitting and the other receiving. This forms my rationale for not absorbing power from the transmission lines that run across my farm; if I were to draw current from them by hooking up strings of copper wire in parallel with them but on my own property, ie across my fields but outside the utility’s right of way, it would still be stealing. If instead of power lines I had a radio transmission tower in my field, and just outside the tower’s right of way I decided to erect similar towers in a circle surrounding it, with wires strung between them, say every 6 inches or so, all the way from the ground up to above the tower. I could suck much energy from that, through whatever my loads are, and into the ground. I have basically created a shielding system, draining to ground. Yes some signal would still get through, but could I still say I have done nothing than absorb some leakage? When you load the secondary side of a transformer you also load the primary side, there’s no such thing as free energy.
March 28th, 2008 at 9:14 am
Capacitance likely plays a part in this too. The air surrounding the transmission line conductor has a certain capacitance. That capacitance allows a certain amount of leakage, and this leakage volume would therefore change with the weather, especially with changes in humidity. This capacitance would also likely be altered by other things, one of which I assume would be me stringing lines along in that airspace. I am not an engineer, but it seems plausible that my displacing of air with copper loaded to ground would also alter the flow of leakage, just like humidity would, by changing the electrical characteristics of the environment surrounding the conductor. And that this would be a measurable difference, and therefore admissible in a court of law. (?)