Researchers at Georgia Institute of Technology have demonstrated – at the IEEE conference July 6 – technology capable of harnessing ambient electromagnetic energy that pervades our modern world.
By taking advantage of the transmitters that are already covering modern cities power is extracted from thin air. In a sense turning mobile phone base stations, tv transmitters and radio station transmitters into micro power stations. While this technology only provides very small amounts of power it is enough to power simple sensors and devices, eventually as the technology develops more advanced electronics may be powered, we may eventually see self-powered bumper stickers telling us to back the f off.
“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.”
Researcher Manos Tentzeris and his research group have developed special antennas along with custom AC to DC converters that allow ambient electromagnetic energy to be converted into a DC current, the right kind of power to store in a battery. The antennas themselves are printed onto paper or plastic using a commercial ink modified with silver nano particles, which is then simply printed using a standard inkjet printer. A range of antenna’s have been demonstrated along with a self-powered temperature sensor made using the antenna, a printed temperature sensor and AC/DC circuit. The demonstration was power courtesy of a TV station over a kilometer away. The team isn’t standing still either,some are working on greater efficiency antennas, new printed sensors and one team is working on a self-powered microprocessor that is switched on by simply holding the antenna up in the air.
Tentzeris and his team began printing antennas in 2006, the original paper circuits absorbed ambient electromagnetic energy at frequencies of 100 or 200 MHz. The next generation antennas utilize polymer sheets instead of paper and now are able to absorb energy from 15 GHz to 60GHz. In the future multiple variations will be included into one design to allow multiple electromagnetic frequency bands to be targeted.. TV stations use specific frequencies as do mobile towers and satellite transmitters, by targeting multiple heavily used frequency at once each antenna could potentially reach milli-watt’s power, getting close to the power requirements of small electronic gadgets and simple wireless communications. This more advanced antenna may also be put together into larger array’s. Like a solar grid an array of antenna’s could be electrically run in parallel and collectively generate a 1 volt of current. This may not sound like much but is a milestone for this kind of power source.
This breakthrough isn’t the solution to the world’s power problems though. The system is only able to provide very small amounts of power – micro watts – not enough to run an iPod but it is enough to run very simple sensors and electronics. The applications for this technology will always be limited to low power gadgets. Combined with other green energy such as solar this could provide a small amount of continuous power to supplement the solar power especially when the sun goes down. A kind of backup system power. By using a super-capacitor to build up the charge and release it when a set level is reached the system could provide 50 milli-watts periodically. This could allow a communications chip to connect to a network a few times a second, not continuous but enough to stay connected with the network, enough of a connection for a message like Sensor OK’ but not the sort of network to display images or video.
The research done at Georgia Tech actually has a lot in common with other wireless power transmission technologies, some of which are already commercially available, most commonly used as wireless recharging systems for our gadgets. The science of power transmission has a long and colorful history. Tesla is the most well-known of the proponents of power transmission, his research dates back to the early 1900’s. Advances in wireless power technologies have concentrated on the transmitter side of the equation, in order to increase the amount of power that makes it to the device, the efficiency. The ambient energy technology works from the antenna side to produce power from a very weak source, no direct transmitter. If you put them both together though you would have an interesting power source for electric planes and blimps, with the underside painted on instead of inkjet printed. There are also many other kinds of transmitters that could be tapped, mobile phones, wireless networks, the list goes on.
While this research dates back to 2006 this technology is only in its infancy, the team at Georgia Tech have only just begun. All of this research and development should lead to cheap self-powered paper sensors, add an ultra low power e-ink displays and a sticky backing and the world may be about to see the first cheap self-powered sticker. A whole new generation of smiley face stickers maybe about to take over the world.
More information at Georgia Institute of Technology
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