Digital thermometers work this way, as do isotope batteries for space probes. But getting significant power from body heat alone is new. The Seebeck effect can convert temperature differences into a voltage, which until now has been quite slow.
This voltage is used to generate a flow of current which, if switched correctly, could charge all kinds of portable devices. The only crucial problem is that heat transfer also continues. Therefore, the quantities of electricity are so small that they are of no practical use. At least that’s what’s happened so far.
Agreed: NASA builds batteries with highly radioactive isotopes such as plutonium-238, but these have significantly greater temperature differences between the radiating isotope inside and the cold of space.
Thanks to a carbon fiber nanotube just 8 nanometers thick (a human hair is about 10,000 times thicker), the effect should soon be usable on your own skin. According to the study by NAIST in Japan, the power output could be increased several times compared to previous methods.
At the same time, it was possible to maintain heat conduction approximately at the same level as in previous experiments. Indeed, if heat were transported between the fibers, the temperature difference would decrease and significantly reduce energy production.
However, the nanofiber still achieves 242 microwatts per meter per degree of temperature difference squared. The greater the distance between hot and cold, the greater the power available.
If a difference of 10 kelvins could be exploited, around fifty meters of fiber would be enough to obtain an entire watt. And with 5 watts, most portable devices could already be charged, even if not quickly.
Given the nanotubes’ minimal thickness, such an amount would be barely noticeable in most clothing – charging port, perhaps. Production has also already been optimized and the time required has been reduced to one eighth of the previous method. Before long, the hoodie will be able to either charge your smartphone or deliver electric shocks, probably.
