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Body Powered Batteries -- Thermoelectrics
An Anonymous Coward writes: "According to this story on Yahoo, the folks at Applied Digital Solutions have "developed a miniaturized thermoelectric generator -- a half-inch diameter ceramic-based `battery' that converts low gradient body heat flow into electrical power." Right now they can power watches or small medical devices. How long before these things can power my handheld?"
handheld?
Screw that. How long before they can power an
artificial heart!?
A completely self-contained, reliable, artifical
heart available off-the-shelf and requiring no
external battery pack or management would be a
sea change in modern medicine. Jean-Luc Picard
lives! Wonder what brand he uses?
As always my memory fails me, but I read in Wired Magazine, about a year ago, about this guy that stored the energy generated by your footsteps and then used it to power all sorts of devices. It turns out he was doing pretty well, but I don't know what came out of it.
Now, if we were to identify a real demand for personal power generation, I'm sure there's a combination of strategies we could use, like those footsteps, body heat, chemicals, heck, even blinking!.. If you consider how many calories are burnt every day by our bodies in order to make it work, and how much energy is released in all sorts of ways, I'm sure we could power our cellphones and PDA's forever.
There are two kinds of people in the world: Those with good memory.
small devices, with their own power which can be placed on/in any person and run off of them for an indefinite amount of time... tagged at birth, tracked in secret... never off the screen for even a nanosecond...
we speak the way we breathe --Fugazi
And you thought falling into a frozen lake was a health hazard before... just wait until you have an artificial heart run by your body heat.
Even after the EMTs pull you from the lake they couldn't restart your heart for at least half an hour until your body temperature increased. Bad news.
Seriously, it doesn't mention what's the minimum temperature the device requires.
--CTH
--Got Lists? | Top 95 Star Wars Line
Hearing aids. Not quite as mission critical as a heart, but still good to use as a sort of field test, IMO.
EveryDNS. Use it. It works.
AC's need not reply
I guess if we assume a skin temperature of 34 celsius (307 K), and an ambient temperature of 20 C (293 K), then our efficiency is bounded by about 4.5%. Given that we dissipate on average 64W/m^2 at idle, and a "fingernail" sized device (1.5 cm^2), we should have about 0.001 W available to us, or 0.4 mW assuming 100% of Carnot cycle efficiency. At 1.5V, this gives a maximum current output of 0.27 mA. Since they are getting about 10 microA, then we can assume they see an efficiency of about 4% themselves. So, it seems like there's room to grow!
Maybe they'll be able to power those PDA's after all!
There's a quick discussion here with regards to human-body-power available for wearable computing.
Also, there's another company that builds thermo-ionic power generating chips (cleverly named PowerChips) called Borealis. They see them being used as a second-stage on typical gas turbine/etc.. generators. They claim to see 20% efficiency wrt the Carnot cycle limit, a few orders of magnitude better than most thermo-electric (Peltier based) generators.
BTW: All these calculations are very "back of the envelope"!
Many of these types of reactors were developed by the russians, and even americans for space use. They all operate on the same principle as your air conditioner. They are glorified heat pumps. They need a "hot bath" and a "cold bath". Their efficency is proportional to the temperature difference between the two. The hot part is easy, and comes from the nuclear material. The cold bath is usually a radiator. Now, in space there's no material (like air or water) to pass over your radiator, so you have to depend entirely on blackbody radiation. (i.e. infrared photons carry energy away) If you remember your physics class the power radiated for this is P=sigma*T^4 where sigma=stefan-boltzmann constant and T is temperature. Anyway, this is the limiting factor. Making nuclear material hot is easy, and the upper limit is the melting point of your container. Making the cold bath cool is hard. It requires a large radiator (since power radiated is proportional to surface area!)
I had some bookmarks on the subject but can't seem to find them now. One of the devices was manufactured by GE. The russians have several. A google search for "nuclear rocket" should turn up something.
--Bob
1^2=1; (-1)^2=1; 1^2=(-1)^2; 1=-1; 1=0.