Scientists have figured out how to harness Brownian motion – literally the thermal energy of individual molecules – to make electricity, by cleverly connecting diodes up to pieces of graphene, which are atom-thick sheets of Carbon. The team has successfully demonstrated their theory (which was previously thought to be impossible by prominent physicists like Richard Feynman), and are now trying to make a kind of micro-harvester that can basically produce inexhaustible power for things like smart sensors.
The most impressive thing about the system is that it doesn’t require a thermal gradient to do work, like other kinds of heat-harvesting systems (Stirling engines, Peltier junctions, etc.). As long as it’s a bit above absolute zero, there’s enough thermal energy “in the system” to make the graphene vibrate continuously, which induces a current that the diodes can then pump out.
Original journal link: https://journals.aps.org/pre/abstract/10.1103/PhysRevE.108.024130
This is genuinely incredible though. Because it means you can cool things even when there’s nowhere to dump the heat into, for example, space.
EDIT: Though in space you lose heat as infra-red, but only in limited amounts. Scaled up this technology would allow far better control letting you run more powerful equipment while also improving efficiency.
And you’re limited to approaching 2.7K, the background temperature and limit for radiative cooling, which is higher than you would want for some sensors. Being able to either extract power and charge a battery to be either used as power, to heat other parts of the craft, or to concentrate for more efficient radiation would be quite useful.