Electronics

Scavenging ambient electromagnetic energy to power small electronic devices

Manos Tentzeris holds a sensor (left) and an ultra-broadband spiral antenna for wearable energy-scavenging applications that were both printed on paper using inkjet technology (Image: Gary Meek)
Manos Tentzeris holds a sensor (left) and an ultra-broadband spiral antenna for wearable energy-scavenging applications that were both printed on paper using inkjet technology (Image: Gary Meek)
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Georgia Tech graduate student Rushi Vyas (front) holds a prototype energy-scavenging device, while School of Electrical and Computer Engineering professor Manos Tentzeris displays a miniaturized flexible antenna (Image: Gary Meek)
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Georgia Tech graduate student Rushi Vyas (front) holds a prototype energy-scavenging device, while School of Electrical and Computer Engineering professor Manos Tentzeris displays a miniaturized flexible antenna (Image: Gary Meek)
Manos Tentzeris holds a sensor (left) and an ultra-broadband spiral antenna for wearable energy-scavenging applications that were both printed on paper using inkjet technology (Image: Gary Meek)
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Manos Tentzeris holds a sensor (left) and an ultra-broadband spiral antenna for wearable energy-scavenging applications that were both printed on paper using inkjet technology (Image: Gary Meek)
Manos Tentzeris displays an inkjet-printed rectifying antenna used to convert microwave energy to DC power (Image: Gary Meek)
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Manos Tentzeris displays an inkjet-printed rectifying antenna used to convert microwave energy to DC power (Image: Gary Meek)

As you sit there reading this story you're surrounded by electromagnetic energy transmitted from sources such as radio and television transmitters, mobile phone networks and satellite communications systems. Researchers from the Georgia Institute of Technology have created a device that is able to scavenge this ambient energy so it can be used to power small electronic devices such as networks of wireless sensors, microprocessors and communications chips.

Manos Tentzeris, a professor in the Georgia Tech School of Electrical and Computer Engineering, and his team used inkjet printing technology to combine sensors, antennas and energy scavenging capabilities on paper or flexible polymers. Presently, the team's scavenging technology can take advantage of frequencies from FM radio to radar, a range of 100 Mhz to 15 GHz or higher. The devices capture this energy, convert it from AC to DC, and then store it in capacitors and batteries.

"There is a large amount of electromagnetic energy all around us, but nobody has been able to tap into it," said Tentzeris. "We are using an ultra-wideband antenna that lets us exploit a variety of signals in different frequency ranges, giving us greatly increased power-gathering capability."

Manos Tentzeris displays an inkjet-printed rectifying antenna used to convert microwave energy to DC power (Image: Gary Meek)
Manos Tentzeris displays an inkjet-printed rectifying antenna used to convert microwave energy to DC power (Image: Gary Meek)

So far the team has been able to generate hundreds of milliwatts by harnessing the energy from TV bands. It is expected that multi-band systems would generate one milliwatt or more, which is enough to operate small electronic devices, including a variety of sensors and microprocessors. Tentzeris says exploiting a range of electromagnetic bands increases the dependability of energy scavenging devices as if one frequency range fades due to variations in usage, other frequencies can be used to pick up the slack.

The team is also looking at combining the energy scavenging technology with supercapacitors and cycled operation so that the energy builds up in a battery-like superconductor and is utilized once the required level is reached. The team expects this approach would be able to power devices requiring over 50 milliwatts.

The researchers have already successfully operated a temperature sensor using electromagnetic energy captured from a television station that was half a kilometer away. They are now preparing another demonstration in which a microprocessor-based microcontroller would be activated simply by holding it in the air.

Georgia Tech graduate student Rushi Vyas (front) holds a prototype energy-scavenging device, while School of Electrical and Computer Engineering professor Manos Tentzeris displays a miniaturized flexible antenna (Image: Gary Meek)
Georgia Tech graduate student Rushi Vyas (front) holds a prototype energy-scavenging device, while School of Electrical and Computer Engineering professor Manos Tentzeris displays a miniaturized flexible antenna (Image: Gary Meek)

The researchers say the technology could also be used in tandem with other electricity generating technologies. For example, scavenged energy could assist a solar element to charge a battery during the day and then at night, scavenged energy would continue to increase the battery charge or would prevent discharging.

It could also be used as a form of system backup. If a battery failed completely, the scavenged energy device could allow the system to transmit a wireless signal while maintaining critical functions.

The Georgia Tech team believe that self-powered, wireless paper-based sensors will soon be widely available at very low cost, making then attractive for a range of applications, such as chemical, biological, heat and stress sensing for defense and industry; radio frequency identification (RFID) tagging for manufacturing and shipping, and monitoring tasks in many fields including communications and power usage.

20 comments
Felix Bayer
My Physics teacher once told me about someone using a similar technologie in the early days of Radio. Because this was considered Stealing it was banned as illegal, as it influenced the range of the transmitter
Muraculous
At this rate we will soon tap into technology that Tesla understood to be possible 100 years ago. Strange that a man such as he could be left to wither and die without proper compensation and acknowledgement from the profiteers (and society in general) who so greedily used this man and then kicked him to the curb.
AB
RCA already launched a similar product last year called Airnergy. It can charge a mobile phone & has a USB port out for charging. It has been commercially available since January 2010.
MikeB
Many years ago I discovered I could light up an LED by placing it behind a TV aerial in the loft of my parents house. Great I thought we could power all manner of things this way. I was told when I researched it that there was a case of a man who had tried the very same thing and had been prosecuted for stealing electricity from the BBC. His antics had created a shadow of reduced signal behind his house and people had complained about no TV signal. If it is possible to legally, scavenge EMR and turn it into a useable supply could I run some copper wire round the enclosure of the substation at the end of my garden and power the house from that, or put a load of TV aerials in the loft and light the house with LEDs?
Daryl Sonnier
Tesla voluntarily gave up his claims to patent royalties owed to him by the Westinghouse company. It sucks, but he did do so of his own free will. Unfortunately, it came back to haunt him later when he didn\'t have the funds to complete all of his research. Are all of you who asked about legality from the UK? I live in the US and have never heard of such a thing. I do know that it\'s illegal to decode signals that you\'re not paying for, i.e. satellite t.v. even though it\'s legal for them to bombard everyone with said radiation.
wrynic
Provided there is no specific Resonant tuning to a particular Transmitter frequency, field strength reduction [shadow-Mike B] should not be a problem. The tendency to move from multi, non specific frequencies or ambient \'noise Rf\' scavenging, to deliberate theft of those extra milliwatts is going to be a very difficult temptation to avoid. Cosmic Rf radiation background noise harvesting would be good!
Gabe Cross
I am not that bright, but I thought that you couldn\'t convert a lower energy wave (IR) into a higher energy form (useful electricity). Doesn\'t that break the 2nd law of thermodynamics? Again, not that bright over here, but if someone could explain how this is NOT a perpetual motion machine (without being a troll, thank you) I would be interested to read it.
Daniel Beach
\"The Georgia Tech team believe that self-powered, wireless paper-based sensors will soon be widely available at very low cost, making then attractive for a range of applications, such as chemical, biological, heat and stress sensing for defense and industry; radio frequency identification (RFID) tagging for manufacturing and shipping, and monitoring tasks in many fields including communications and power usage.\" ...excuse me but passive RFID tags have been doing EXACTLY what he\'s talking about for over 20 years! And yes, Tesla did it first. So how can they claim IP???
justanothertechie
Firefly Technologies invented this harvesting technology in 2005 and was issued a US patent for a broadband wireless power supply. In 2006, the company sold their technology to Powercast, which received an award from the consumer electronics show for best emerging technology in 2007. These guys better do some patent searching before they stake their claim in the wireless power arena as to who did what and when to avoid lawsuits.
PG
This is the basic principles behind a crystal set. If you use a small rectifier circuit with a basic radio receiver, anyone can do this. Use a long antenna such as the guttering around your house :)
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