Letters to the Editor
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Not quite "leftover" energy
The concept of harnessing wasted energy is intriguing, but this device is not doing that. If nothing is plugged into the headphone jack, then there is no energy delivered, thus no energy is wasted or "leftover".
By plugging in this device, then there will be energy delivered. This adds an additional burden to the source of the electricity in a plane (presumably the engines). So while it's a clever way to get some juice out of an unconventional source, it's not exactly a "new trend" or "green".
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Dubious "harvesting"
It is probably better to call this "energy diversion" rather than harvesting. The voltage is present at the audio jack, but no current is drawn until something is connected to it. So the energy that winds up in your ipod using this device is, truly, a little more energy that has to be drawn from the plane's audio amplifier, and thus from the airplane's general electrical system, which powers the audio system. "No free lunch" in other words. You can also tap a little current off the regular POTS (Plain Old Telephone Service) dial system and store it for your own use, similarly. But the phone company is going to have to put that much more (plus a slight additional amount for the frictional losses) in at the other end. The original source has to be the same basic hydropower or jet fuel or natural gas or geothermal or solar which powers the base system.
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Huh?
I'm willing to bet that the audio jacks in airplanes don't have a switch built in to only deliver a signal when something is plugged in - it's far more likely that they receive a steady amount of power because that's easier to implement and maintain (no switches = nothing to break at point of connection). Correspondingly, the power used to send the signal is essentially being wasted when the signal isn't being used.
If that's the case, then you're basically wrong about this device increasing the load on the plane. I'd be willing to bet that if the power draw for the audio jacks was really that significant, the airlines would be regulating it either with switches or usage fees.
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Good point
Yeah, qyn and civiliz are right, Inflight Power isn't exactly harvesting leftover energy but, rather, finding a use for energy that isn't being offered in a useful form. As qyn says, "If nothing is plugged into the headphone jack, then there is no energy delivered, thus no energy is wasted or 'leftover.'"
I should have been more explicit that the green uses concern other sorts of energy conversions, especially from vibrations. The vibrations created by your car engine truly are leftover energy (just like the heat created by your lightbulbs). Harvesting energy from these things -- using the same tech in Inflight Power -- is a novel thing.
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Gain stages
I'm assuming you'd get a faster charge with this device if you have the Muzak cranked at a high volume?
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To Johnny re volume
Yup, that's the recommendation -- crank it up to max.
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A jet fuelled iPod is no Green Breakthrough!
The 60Hz voltage oscillating in your home electrical socket is not waste of power and it is not a “green breakthrough” when one plugs a lamp into it. Remember, power is current multiplied by voltage (P=I*V). Current will not flow until a load closes the circuit.
The audio signal oscillating in an unused armrest follows the same principal, but not necessarily at 60Hz. Any device closing that circuit will be a load, drawing a current (electrically) from the aircraft’s audio amps and onboard generator and (hydraulically) fuel lines.
Perhaps we should stick with our portable chargers that use long-life rechargeable batteries (charged on our green-grid of choice).
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Some basic electrical theory
I'm willing to bet that the audio jacks in airplanes don't have a switch built in to only deliver a signal when something is plugged in - it's far more likely that they receive a steady amount of power because that's easier to implement and maintain (no switches = nothing to break at point of connection). Correspondingly, the power used to send the signal is essentially being wasted when the signal isn't being used.
Imagine it this way: Your house has a 110/220 AC electrical system that's sending power to your wall outlets all the time, regardless of whether anything is plugged into them or not. Does the electricity leak out of the outlets when nothing's plugged in to them?
In case you don't know the answer, it's NO. That's not the way power works. As several others have already noted, there's no such thing as a free lunch.
I remember back in high school, in my physics class, there were students who thought that operating the car's radio was "free energy." That is, we were asked the question: If you use the radio or other electrical devices in your car while driving, does it cause an increase in the use of gasoline? And the answer is, yes of course it does, though to be fair the amount of extra gas consumed is relatively small (because there's a lot of energy in gasoline compared to how much is used by most solid-state electronics).
Pretty much everybody in the class got that answer wrong. Except me, of course!
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If you really want to scavenge energy to power your iPod ...
... they need to make a version of one of these little gizmos that you can take to your local rock concert and put in front of the speakers there! After all, there's a hell of lot of energy being pumped out of most venue amps to shake the walls and wake the neighbors, why not channel it into "green music."
Also all these gizmos absorbing scavenging too-loud music would help lower the volume in the area outside the club and keep the neighbors from complaining. It's a win-win situation!
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ummm, no
"Harvesting energy from these things -- using the same tech in Inflight Power -- is a novel thing."
This is not true at all nor is the "super cap" the big breakthrough. The "same tech" is nothing more than a rectifier. The super cap, which has been around for many years, has a smallish form factor but, in applications, can discharge energy faster than a battery. Super caps have the same energy density as some battery types.
The earliest versions of this tech that I saw, and I'm sure there were much earlier ones, were over 10 years ago in BEAM robotics mechanisms. The robot would hang out waiting to have enough charge to move, then move and begin waiting again.
In other words, the tech getting pumped here is a novel use of some very old tech. It is sad that it is included in a blurb on energy harvesting because it just confuses people. I guess that is why we call it "marketing" and not "science".
As for the vibration 2 electricity thing. That to is old, but not ancient. Remember the shoes that blinked an LED each step? Same tech. Piezo to diode. However, mass market adoption of the stuff is interesting.