Last week Gizmodo, Macworld and several other sites pointed to a gadget called Inflight Power, a nifty device that plugs into the audio jack of an airplane seat and converts the music into electricity to charge up your iPod or other portable energy suck. The device sounded rather ingenious -- finally, someone had found a use for the Muzak that airlines pump out in the armrest -- and I called up its inventor, an engineer named Tom Giannulli, for more information. It turns out that Inflight Power marks an intriguing new trend in power generation, something that folks call energy "harvesting" or "scavenging." Small amounts of wasted energy are constantly floating about us -- in ambient vibrations, in electromagnetic radiation, in temperature variations -- and Giannulli says that his device is one of the first commercial examples of new technology that allows us to mine and put to use the unused juice.
The sound coming through your coach seat's armrest is just an electrical signal of low voltage; Giannulli's charger works by storing this electricity in a capacitor and then, when it reaches a certain threshold, outputting it through a USB plug. (You call such a device a "charge pump.")
Not all music channels will give your iPod the same power, Giannulli says. You've got to provide the Inflight Power with music that's got some bite to it. "Talk radio doesn't have a lot of energy," Giannulli says. "You want to use heavy metal or salsa. The reason that's so good is because of how they record it -- they saturate the amps, so there's just a lot of energy there." Giannulli has been pushing airlines to add a "charging tone" to their audio lineups -- this is a prerecorded tone of a specific frequency to deliver the optimum energy to his device. Jet Blue and Virgin are considering doing so, he says.
Inflight Power also uses a couple of AAA batteries to smooth out and supplement power delivery when the input audio is weak. Giannulli says these aren't required, but your iPod will charge faster when they're in place. Still, the power does not come as quick as on the ground. He estimates that charging an iPod with his device takes three times as long as when you plug it into a computer. Giannulli's basic Inflight Power charger sells for $35; one with connections for the iPod (or iPhone) sells for $45. (Note that the Inflight Power charger -- which outputs only 5 volts through a USB plug -- can't charge up your laptop.)
Inflight Power is made possible by a breakthrough called a supercapacitor, which is a circuit that can store a large amount of energy in a small space. "A couple years ago, a capacitor that stores 3.3 farads -- that's how many farads are in the capacitor that I have in my unit -- used to be the size of your head," Giannulli says. (A farad is the standard measure of electrical capacitance.) "Now they've got it down to the size of the tip of your finger."
Such small high-capacity circuits allow for fascinating new possibilities in collecting power. "The idea is that you take very small amounts of energy and concentrate and collect them in these supercapacitors," Giannulli says. "You could have all these energy harvesters sitting all over your house, and all they do is take up leftover vibrational energy from your TV, say, or the vibrations from the windows or the motor of your refrigerator. And they just sit there and take little millivolts every day. And then they concentrate that, and at the end of the week, well, maybe you can run your hair dryer with it."
Many researchers are also looking to use harvested energy to power wireless computer sensors to collect environmental data on buildings or other structures -- for instance, sensors that detect how the Golden Gate Bridge moves in response to seismic activity could be powered by the vibrations of the bridge itself. Indeed, last week engineers at the University of Southampton in the UK unveiled just such a device -- a power generator fueled by tiny vibrations.
The inventors say that in addition to charging up sensors, the device could be useful in some medical applications. A beating heart, for instance, provides enough vibrational energy to charge up a generator that could, in turn, power a pacemaker. Now that's an energy conservation innovation that even Dick Cheney could appreciate.
Update: Several readers point out that Inflight Power isn't exactly harvesting "leftover" energy but, rather, finding a use for energy that isn't being offered in a useful form. That's because, as reader qyn says, "If nothing is plugged into the headphone jack, then there is no energy delivered, thus no energy is wasted or 'leftover.'" So when you do plug your Inflight Power into the jack, you are drawing more of the airplane's power.
So that's not quite "green" -- it's powered, after all, by jet fuel. I should have been more explicit that the Inflight Power uses technology that allows for other "green" uses, especially harvesting energy from vibrations. The vibrations created by your car engine do represent wasted energy (as does the heat created by your light bulbs). Harvesting this power -- using the same tech that Inflight Power uses to convert jet fuel into iPod juice -- is a novel thing.