Researchers have discovered a way to capture and harness ambient electromagnetic energy transmitted by such sources as radio and television transmitters, cell phone networks and satellite communications systems. By scavenging this ambient electromagnetic energy from the air around us, the technique could provide a new way to power networks of wireless sensors, microprocessors and communications chips.

MultiBand Printed Antenna for Electromagnetic Energy Scavenging from Cellphones and Satellite TV Signals“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 who is leading the research. “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.”

Tentzeris and his team are 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; radio-frequency identification (RFID) tagging for manufacturing and shipping, and monitoring tasks in many fields including communications and power usage.

Communications devices transmit electromagnetic energy in many different frequency ranges, or bands. The team’s electromagnetic energy scavenging devices can capture this energy, convert it from AC to DC, and then store it in capacitors and batteries. The electromagnetic energy scavenging technology can take advantage presently of frequencies from FM radio to radar, a range spanning 100 megahertz (MHz) to 15 gigahertz (GHz) or higher.

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

And by combining energy-scavenging technology with super-capacitors 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 super-capacitor and is utilized when the required power level is reached.

The scavenging device could be used by itself or in tandem with other generating technologies. For example, scavenged energy could assist a solar element to charge a battery during the day. At night, when solar cells don’t provide power, scavenged energy would continue to increase the battery charge or would prevent discharging.

Utilizing ambient electromagnetic energy could also provide a form of system backup. If a battery or a solar-collector/battery package failed completely, scavenged energy could allow the system to transmit a wireless distress signal while also potentially maintaining critical functionalities.