Device harvests energy from ambient TV signals

Posted by Kate Taylor

Researchers have created a new energy-harvesting device that can draw power from sources such as radio and television transmitters, cell phone networks and satellite communications systems.

They say it could provide a new way to power networks of wireless sensors, microprocessors and communications chips, in a similar way to devices that harvest energy from vibrations.

"There is a large amount of electromagnetic energy all around us, but nobody has been able to tap into it," said Manos Tentzeris, a professor in the Georgia Tech School of Electrical and Computer Engineering.

"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."

And, cleverly, the team's using inkjet printers to combine sensors, antennas and energy scavenging capabilities on paper or flexible polymers.

The resulting self powered wireless sensors could be used for chemical, biological, heat and stress sensing for defense and industry, say, or RFID tagging for manufacturing and shipping.
               
The team's devices capture energy from a wide range of banks, convert it from AC to DC, and then store it in capacitors and batteries. They can currently take advantage of frequencies from FM radio to radar, a range spanning 100 megahertz to 15 gigahertz or higher.

Experiments using TV bands have already yielded power amounting to hundreds of microwatts, and multi-band systems are expected to generate one milliwatt or more. That's enough to operate many small electronic devices, including a variety of sensors and microprocessors.

And by combining energy scavenging technology with supercapacitors and cycled operation, the Georgia Tech team expects to power devices requiring above 50 milliwatts. In this approach, energy builds up in a battery-like supercapacitor and can be used when the required power level is reached.