'Free' Power from Broadcast Transmitters
Researchers at Georgia Tech are tapping emissions from a TV station located half a kilometer from their lab to power a wireless temperature sensor.
Manos Tentzeris, a professor in the Georgia Tech School of Electrical and Computer Engineering leading the research said, “There is a large amount of electromagnetic energy all around us, but nobody has been able to tap into it. 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.”
The self-powered wireless sensors are created using ink-jet printers and a special ink containing nanoparticles of silver and/or other material. The researchers have been able to combine sensors, antennas and energy-scavenging capabilities on paper or flexible polymers. The resulting sensors can be used for chemical, biological, heat and stress testing for defense and industry. The devices are able to use RF sources ranging from 100 MHz to 15 GHz or higher.
A Georgia Tech Research News article said scavenging experiments using TV bands have already yielded power amounting to hundreds of microwatts. Multi-band systems are expected to generate one milliwatt or more, enough to operate many small electronic devices, including a variety of sensors and microprocessors. Devices requiring 50 mW or more should be able to be powered by adding super-capacitors and using cycled operation.
The Georgia Tech team is also looking at alternative power for the sensors—most likely solar—with the scavenged RF power used at night. Can you imagine a situation where keeping those high power TV transmitters on the air could become a national security issue, not because of the programming but because they are powering an array of sensors used in critical applications?