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Body Heat Could Charge Your Cellphone
An anonymous reader writes to mention Nature is reporting that scientists have discovered a much more efficient way to use silicon to convert heat into electricity. This offers the possibility of many different applications including possibly charging your portable electronics just by wearing them close to your skin. "The concept of converting waste heat into electricity isn't exactly new, but it never really materialized due to efficiency hurdles. Now, scientists from the U.S. Department of Energy's (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California at Berkeley think they may have found a key [to] increase the conversion efficiency by a factor of 100."
Between the cell phones being charged by shaking them, by solar power, and by body heat - at what point will they be blowing up in our pockets?
Slap Slap Slap - But m'aam, I just wanted to charge my cellphone and your breasts were handy.
Table-ized A.I.
Think bigger. Put these and some batteries near your brakes or under the hood of your car. Line the Shuttle with them, attach them to the boosters that get jettisoned. Tape them to politicians so all the hot air charges them.
I was thinking of converting to paganism, but where the hell can you find sacrificial virgins these days?
I just hope the word "insert" doesn't appear in the instructions.
Brett
Paging Dr. Carnot, Dr. Nicolas Carnot, call for you on line 2...
Human body thermal output is about 120 watts on average, skin surface area is 2 m^2, so a 50-cm^2 cell phone body can intercept 0.6 watts of body heat. BUT, the laws of thermodynamics place a limit on how much of that heat can be converted into useful work to charge the batteries in the phone. That limit depends on the temperature of the heat source and sink.
Suppose one side of the phone is in contact with your skin at 32 C (305 Kelvin), and the other side is in contact with room-temperature air at 27 C (300 K). (In practice, the temperature difference will be smaller, because the air near your body will be warmed above room temp.) The maximum efficiency one could get from these thermodynamic efficiency is (305-300)/300 = 1.7%.
And that's the theoretical maximum possible conversion efficiency. Real systems rarely come close to that.
SO, the most energy we could possibly get out of this generation system is 0.6 * 1.7% = 10 milliwatts. My iPhone's battery holds about 2400 mW-hours of juice, so if I installed this charging system and held it against my skin 24/7, it would take about 10 days to charge in the theoretical best case... and in practice, much longer than that.
This idea's dead in the water at the basic physics stage, before we even get to the engineering considerations.
Right, I'm not a scientist, but TFA talks about all sorts of fantastic things (e.g. charging your iPod with body heat) that aren't mentioned in the Abstract of the cited piece in Nature. While the article does quote one of the authors for such claims, what the Nature article Abstract (I'm not paying $ to read stuff online) alludes to is improving the efficiency of potential co-generation from sources of waste heat from combustion--power plants, car engines, etc. Besides, if it's cold enough out that I'm wearing a winter coat, do I really want to shove a heat sucking iPod down my pants? Not really. But sticking it against my car's engine? Sure.
Also TFA mentions "...the discovery will depend on whether these rough nanowires will be efficient enough to make commercial sense." So yeah, I don't see it (soon) being any more energy efficient to manufacture heat converting nanowires for my iPod Nano than it would be to say, construct a battery. But maybe they have something that could better convert a massive heat gradient into electrical energy cheaper for the purposes of co-generation. Who knows, maybe even cut down on heat pollution.
Hope that wasn't classified or anything - but then Dad passed away a while back.
Request your free CD of my piano music.
"[Scientists] may have found a key increase the conversion efficiency by a factor of 100." Let me guess, this is involves some form of fusion.. and the machines have found all the energy they will ever need. This happened in a dream once, that I was so sure was real..