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
I feel like I must be missing something here.
If you’re extracting energy from ambient heat without a temperature differential, then is that not a perpetual motion machine? Once you use that energy, 100% of it goes right back into the system as waste heat, ready to be harvested again. You can run this indefinitely and it will never reach absolute zero, so…what am I missing?
Sounds like from the properties of graphene they are able to turn its thermal energy to electrical so long as the material isn’t at absolute zero (obviously or then it would be a perpetual motion like machine), plus i dont see anything that says this process is lossless just high efficiency. It’s definitely not perpetual motion eventually the system would lose all thermal energy and no longer output any electrical energy. If producing waste heat meant perpetual motion, geothermal would also be classified as perpetual motion, but it isn’t lossless. It seems like it’s essentially a heat pump at a much smaller scale where the ambient temp of the room keeps the graphene’s thermal energy charged in a way. Idk nothing on this seems unintuitive unless they start trying to claim it has massive outputs. I’m guessing this is something that could help power some micro sensors by using heat in the environment but not for anything larger as you’d probably need massive sheets of graphene and they havent really said anything about scaling. Although word of caution I’m only a software engineer not a theoretical physicist, so take my ramblings with a grain of salt and defer to any actual physicists in the comments here haha
You can’t destroy energy though. Where is it going?
Consider a closed system. That energy has to go somewhere. In the geothermal example, it is going into waste heat — heat which cannot be re-harvested because it requires a temperature differential.
If you don’t require a temperature differential, where’s the loss occurring here? How is the “waste” heat non-harvestable? I don’t see how a closed system could ever reach absolute zero.
Well if this works as they say I’d guess this isn’t working without a temperature gradient, just a very small one that is found throughout the molecules in the graphene sheet itself, hence why this needs to be above zero Kelvin and why I’d guess they are only targeting micro/nano sensors to power as they can’t ever scale this beyond the inherent gradient present in graphene. I’m not a physicist so don’t take my word as the gospel but at the same time I don’t see why this is ruffling so many feathers when it clearly can’t scale past these smaller voltages that they are targeting, which seems to hint at this just being a way to take advantage of the natural heat loss on graphene for small powered devices.
If it works then it doesn’t matter how many feathers it ruffles. I had the perpetual motion thought as well, but if it works, it works.