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."

The inverse makes silent sub air-conditioning

[MichaelCrawford]

My dad was an engineer for a Naval submarine shipyard. He told me that thermoelectric panels attached to the inside of the hull cooled the submarine silently when a voltage was applied.

Hope that wasn't classified or anything - but then Dad passed away a while back.

reversible?

[TheSHAD0W]

Is this effect reversible? Could it be turned into a super-efficient Peltier module?

There is a better way.

[headbulb]

You are always moving. Most likely the phone is in your pocket moving with you.

Have you seen those ever lasting flashlights. Which use a magnet, a coil and a capacitor. The same concept could be used here. It might not keep the phone charged for heavy users but it could be a nice supplement to the charger.

Maybe if they really got creative they could reuse the coil and magnet as the vibrator.
OH and I didn't read the article. These are both interesting idea's but how much power can we really extract.

Re:Basic physics: no.

[david.given]

SO, the most energy we could possibly get out of this generation system is 0.6 * 1.7% = 10 milliwatts... This idea's dead in the water at the basic physics stage, before we even get to the engineering considerations.

Actually, 10mW is loads. You're not going to charge batteries off that or run a GSM phone, but it's more than ample for powering things like wristwatches, calculators or medical sensors; and with appropriate design, there's no reason why you couldn't build a PDA that worked at that kind of power level. Microchip make a 16-bit PIC that runs at about 1.3mW per MIP. Combine this with an eink screen which only uses power when updating, burst radio powered by a capacitor for low bandwidth data transfer, and a lot of static RAM (which has standby loads in the microwatt range), and you could easily come up with a basic but useful device.

Personal Thermonuclear Generators

[sgartner]

How about using these in a water-heater sized device in your home. With a isotope heat source at the bottom, a coil lined with these strings, filled with some kind of heat transferring liquid (say, water). You could put one of these in every home and without any moving parts (as in a traditional thermonuclear generator with giant turbines) it would be very reliable.

Seebeck effect

[piotrr]

I thought the Seebeck effect [wikipedia.org] already had a conversion efficiency of 2-3%. How can you possibly increase that a hundredfold without breaking the laws of thermodynamics?

Re:Personal Thermonuclear Generators

[jc42]

How about using these in a water-heater sized device in your home.

I've seen this suggestion any number of times, often with snide comments about how engineers have missed something obvious. This usually causes some engineer to simply mention that there's a better way. No matter how your water heater is powered, it's always more efficient to add insulation to the water heater, and use the fuel that you save to directly power an electrical generator. This skips the stage of extracting power from the water heater's heat loss, and can thus extract more electricity from the fuel (or use less fuel to generate the same electricity).

Unfortunately for such schemes, it's only practical to extract energy from a heat gradient if the heat gradient is going to be there anyway. Then, if the extra weight isn't a problem, you might be able to use some of the heat you're losing to produce a small amount of electricity "for free" (i.e., at no additional fuel cost).