Video: An Energy Harvester Based on the Motion of Graphene

This seems more to me like those little piezo generators that require some compressive force to generate small quantities of current....a lot of effort and expense for very little current, still those devices did find niche uses....I guess we'll have to wait to see how it plays out....

That video is incorrect! It shows the piezo element being compressed by the finger and remaining compressed all the time the finger is depressed. If fact, a somewhat more complex mechanism makes it so a spring/mass is compressed during most of the finger depression, and then it is released suddenly during the last part of the finger depression. It is the sudden release that allows the spring to force the mass to strike the piezo element with considerable speed. It is that sudden compression of the piezo element that produces the high voltage and consequential spark to ignite the gas.

This seems more like a new material approach of converting mechanical energy into electrical energy known as a condenser microphone. I don't see from the short video where the biasing charge comes from.

Charge could be provided by electret.

I think I see what you are saying, in that one might inject charge to the graphene during its introduction, and it remains in a state as an electret.

Based on what I am reading of late about proton conductivity with graphene in sunlight, it might be the beginning of something far greater...i.e. - PV based on graphene proton charge carrier mobility being far higher than in silicon, resulting in improved efficiency at a lower cost, and also resulting in PV that when properly catalyzed on the water-splitting side of things, could be artificial leaves that produce hydrogen during daylight.

I don't think so. According to the video, each contact of the graphene with either metal plate transfers electrons to the plate just touched. Thus the graphene would require a source of current, not just charge.

Also, since charge is alternately transferred to one plate, then the other, the output would be a form of AC. Due to the small size of the graphene bump, I presume the AC would have a very high frequency, and it would be very difficult to synchronize the large numbers of graphene bumps required to produce a useable amount of electric energy. Finally, I suspect this would produce a voltage far below that required for direct use or conversion to DC using any diode(s) currently available.

More power to them if they can actually fabricate such a device!

"..... other than it violates a number of laws of thermodynamics. ...."

.

Which thermo laws does it violate? It does make me curious, but I can't think of any specific violation.

Wireless power and solar cells can generate electricity from EM waves without needing a needing to use a gradient or an area of higher and an area of lower energy.

Wireless power and solar cells get energy from low-entropy sources, namely the wireless transmitter and the sun or other sources of light.

Harvesting thermal energy from an object which is the same temperature as its environment is a different matter. Removing energy would cool it. More heat would flow in and the process would continue, generating an unlimited amount of energy, contrary to the first law of thermodynamics, conservation of mass/energy, not to mention reducing entropy (third law).

Heat engines which convert heat into energy require a temperature difference. They remove heat from a high-temperature source, convert some of it to energy, and deposit the rest in a low-temperature sink. It's analogous to a hydroelectric dam on a river which depends on the difference in water elevation. A heat engine without a temperature difference is like a hydroelectric dam in a lake -- no elevation difference, no energy.

When you have "free energy", there is invariably something amiss. (There is always a fly, sometimes hard to find, in the ointment.)

I'm wondering if there is a disconnect between the original research and the popular accounts by science writers.

Here is a copy of the original paper:

https://arxiv.org/pdf/1609.06301.pdf

I sort of think we should not then get ahead of ourselves here. I am not convinced that the STM or other microscopy is not putting a focused energy source into the experiment. That is a total game changer when considering energy balance.

Jury is left befuddled in the jury box, much less the jury room.

As to isothermal energy harvesting, this is obviously describing a perpetual motion machine of the first kind, and is therefore unworkable, impossible as a thermodynamic machine.

If this does not rely on thermodynamic action, then other considerations are possible, including energy tunneling, phonon effects, and the not-well-understood cosmic energy (that is supposed to be unavailable to us). All that being said, the number of such "engines" producing energy can probably be counted on the number of fingers a taxi driver holds up after being cut off, minus one.

" I am not convinced that the STM or other microscopy is not putting a focused energy source into the experiment."

That's a very good point!

And here's another thing. If these waves really are due to thermal motion, how much force is behind them. When you put some conductors close by and make them do some work (force x displacement) instead of moving freely, are they still going to move or will the attraction to the opposite charges on the plates bring that to a stop? I would hope someone has done some calculating.

Don't get me wrong, it also strikes me as odd, but I'm not sure any thermo violations are all that clear cut.

The entropy of an isolated system does not decrease with time....

Okay, entropy has the dimensions of energy per temperature. Assuming energy is conserved when converted to electricity, a decrease in temperature of the system does not lead to a decrease in entropy. It leads to an increase. No violation there.

.

No one makes much fuss about thermo laws being broken by wave power generating power from ocean waves, which must have the effect of damping ocean waves. What is the size limit below which harvesting power from waves becomes a violation?

The argument that wireless power or solar cells work because of a gradient of power from a discrete source isn't that helpful when you consider that solar cells and wireless power receivers will make electricity even when in isotropic fields.

There is nothing here arguing free energy. If it cools the surrounding, then energy is obviously coming from ambient heat. So long as that energy is conserved, there is no reduction in entropy if the temperature falls.

If I am messing something up here, please set me straight. I am certainly open to being wrong....in fact I suspect in all likelihood I am, so I'd really appreciate some nudging in the right direction.

The four Laws of Thermodynamics (0→3) are Physical Laws which are never violated. There are some laws of approximation in Thermodynamics that although being convenient in their realm can lead to apparent violations when used outside of the correct field.

You have only restated that the laws of thermodynamics when appropriately applied are known to be true laws of immutable nature . I agree.

You have not provided any insight into how that applies to the case being discussed.

How can I possibly make the case that ocean waves conform to the laws of thermodynamics when you don't explain your case that they don't conform to these laws?

That"s truly the case you thought I was trying to make?

Yep. It does explain why we both responded with incredulity.

I'm thinking this pretty much describes it...

"A perpetual motion machine of the second kind is a machine which spontaneously converts thermal energy into mechanical work. When the thermal energy is equivalent to the work done, this does not violate the law of conservation of energy. However, it does violate the more subtle second law of thermodynamics (see also entropy). The signature of a perpetual motion machine of the second kind is that there is only one heat reservoir involved, which is being spontaneously cooled without involving a transfer of heat to a cooler reservoir. This conversion of heat into useful work, without any side effect, is impossible, according to the second law of thermodynamics."

https://en.wikipedia.org/wiki/Perpetual_motion#Classification

That does hint at an explanation, but hides behind the description of 'more subtle' rather than provide actual edification. There are no references linked for this part of the Wikipedia article, so no help there either.

You didn't respond to my ocean wave power discussion nor to the dimensions of entropy line of reasoning, but perhaps the following will allow you to consider this might not be a thermo violation (I am playing devil's advocate, I still hold reservations myself):

Consider that a second heat reservoir need not be so much a function of space as time. The Beverly Clock has been running continuously for more than 150 years without winding or wall power. It runs on variations in barometric pressure. Variations in pressure cause bellows on a sealed volume to lift a weight which is used to drive the pendulum. Nothing precludes fluctuations in temperature being used to motivate a similar process to lift a weight.

Considering a volume of gas at a certain temperature, there will be a distribution of energies for the gas molecules. There will reliiably be variations in energy of incident molecules at a specific location on a fairly short time scale without the entire volume requiring any significant change in temperature. That reliable variation in energy of incident molecules might use time as the second reservoir in much the same way as the Beverly Clock, to extract energy from the surroundings to do useful work, even slightly cooling the surroundings, yet not violating the 2nd law of thermodynamics even subtly.

That is quite a good answer. Thank you.

Thanks for that link! I did read the paper, although I won't claim to have understood much of it.

On the other hand, I see a pretty big gap between that paper and the video of the OP of this thread.

I think James Stewart is likely on the right track...

"More heat would flow in and the process would continue, generating an unlimited amount of energy..." Not unlimited, because as the process continues, more and more of the surroundings would be cooled, making it more and more difficult for heat to flow in.

A long time ago, I read a science fiction short story set in an extremely cold climate. As the story developed it was revealed that there was an invention that had circumvented the second law of thermodynamics, turning the ambient thermal energy into useful work. This device was supplying power to humanity for years, sucking the thermal energy out of the environment until the ambient temperature was barely high enough for survival.

I'm not sure that this would actually happen. Practically all of the energy we use ends up as heat when we're done with it. If we stored the energy instead of using it, then, yes, it would reduce the ambient temperature. (Energy sequestration to combat global warming?)

A device like this wouldn't create energy, it would reduce the entropy of the energy so that we could use it again, which amounts to a freebie in that it takes something useless and makes it useful again. (I'm still skeptical, I don't believe in a free lunch.)

I have been searching the internet for the last couple of days for a reference to this story, and finally found it. It was Frederick Pohl's "The Snowmen".

http://www.docsford.com/document/432521