Our wireless power article showcased new products that you don't need to plug in to charge up—but they still use a base station that's tethered to some kind of power supply. Now Intel has demonstrated an even more innovative way to draw power. It's a wireless device that grabs its energy from a freely-available and abundant source: radio transmissions.
An Intel research team set up a system that collected enough energy from a TV signal transmitter around 4km away to power a tiny electronic desktop meteorology gadget. Technically speaking, they built a box of tricks wired to a standard table-top TV antenna. That allowed them to sample some of the 960 KW of effective radiation power put out by a TV transmitter set on channel 48. Their set-up managed to harvest some 60 microwatts of power, which was enough to create 0.7 volts across an 8 kilo-ohm load: essentially just about enough juice to drive the little weather station and its LCD screen.
And that's the slightly creepy part. All that wireless power was there already. The TV transmission radio waves streaming past us all, pretty much all the time, contain that much energy. And that's not to mention the sea of FM radio transmissions, Wi-Fi signals, GSM signals from cellphones and towers, Bluetooth headsets...
Before you start reaching for your tinfoil hat, note the use of the words "slightly creepy" back there. We're all being bathed in radio-frequency signals all the time, and they're harmless. The only time they're harmful is when they're designed to interact with the molecules in our bodies: For example, a microwave oven's radio waves are tuned to make molecules of water in food oscillate, and thus heat the food. I won't go into the debate on the supposed biological dangers of cellphone signals here—it's just too complicated, and the jury's still out.)
What this demonstrations shows is that one day it may be possible to power our gadgets by sipping on ambient radio signals that just happen to be zipping past anyhow. The goal of this research is to develop several hybrid power sources that combine different ways of generating electricity—including this radio-frequency one—to devise a more eco-friendly way of powering our gadgets.