1y ago

Harvesting almost-unlimited energy (in tiny amounts) from ripples in graphene

interestingengineering.com Scientists manage to harvest energy from ripples in graphene

Feynman thought that energy can't be harvested from Brownian motion at thermal equilibrium, but scientists have now done it.

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

30 comments

This is not a source of energy, but it could be used two ways:
By applying thermal energy you can extract electricity.
By not applying thermal energy, this might be used to supercool things (like electronics, or to make helium flow as a superfluid).
The potential here (ha!) is that power May be extracted without being concerned about Carnot efficiency limits, at least on a very small scale.
- It's more like a generator that uses ambient heat as the "battery". With previous systems you could only extract useful work from heat if you had a heat gradient (e.g. one area that's hotter than another). With this invention the innovation is that graphene's unique combination of thinness and conductivity basically let you convert the brownian "heat" of the substance itself (not the environment) into electricity.
  
  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.
  
  I couldnt access the full text, but that was my impression, too, based on the summary. It appears to work on some analog of hysteresis where the technical balance of energy is maintained but the time scale of restitution is long enough that power can be "siphoned off". Again - since conservation of energy must be preserved and no matter is created or destroyed, this would serve to reduce the temperature of the graphene. There doesn't appear to be a scale for their experimental work and whether they're extracting pico amps or microamps across the (I guessing form the publicly available graphs) 0-0.4 volt potential.
  It's not clear if they're looking at nominally uniform temperature material which has fluctuations in temperature due to the surroundings, or if they are inducing temperature gradients in the material intentionally to produce the signal. I'm an engineer, not a theoretical physicist, so anyone claiming to end-run the second law of thermodynamics is going to be treated with a bit of skepticism as to the practicality or scalability of this "cheat".
- They specifically said that you don't have to apply an external thermal source.
  
  If you'll allow me to be pedantic, they already applied heat to the sample as it was above absolute zero. For this device to not violate the laws of thermodynamics it has to cool down when the power is extracted so, in an otherwise adiabatic system, a perpetual use would eventually require the addition of heat to continue to produce power.
  Like the recent claim of a room temperature superconductor, the ability to produce this effect at a macro scale would be revolutionary. Example: 99% efficient solar panels. Combination refrigerator/water heater appliances which use no outside energy. Home heating and cooling which requires not only no energy but produces surplus power in the cooling months. Your home dehumidifier could charge your car or your laptop. You could drop this generator into the ocean and simply pipe unlimited energy to the shore, using the water as a sink. Practically, though, it sounds like microamps (at best) is the result, so - as they said - semi-autonomous, very lower power electronics is the real target application, leaching thermal energy from the environment in such small amounts as to be negligible. A bit like using harvesting energy from radio waves (a myth that was explored on Mythbusters and, while possible, was highly impractical)

Holy shit that's actually really big news even if any practical applications are very far off. As someone said in a comment below, this is essentially Maxwell's Demon, which as I understand it violates the second law of thermodynamics-- that entropy must always increase. In other words, "waste heat" is no longer truly a waste; we can extract energy from heat without a temperature gradient! I'll be watching for more news on this (both for confirmation and dispute) in the future. If this does turn out to be true, it's almost certainly Nobel Prize worthy.

It sounds like this is a method for harvesting zero-point energy. If so, and if it works, that would certainly be a big step forward.
- Sadly it's not extracting energy from the quantum flux :) But happily, it is extracting energy from the heat of the world -- of which there is plenty (enough for us to treat it as unlimited).
  
  Thanks for the explanation.
  I'm getting one scientific revolution ahead of things here.
- Is it? The fact it needs to be above absolute zero makes me think it's instead just a clever way of harvesting the thermal energy of the environment without large apparatus.
  
  It's definitely not extracting energy from the vacuum. It's converting latent heat energy into electrical energy due to clever engineering and the quirky properties of graphene.
  
  Even that could be huge, if it's scalable and cost effective.

30 comments