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Engineers harvest clean, continuous energy from air

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Re: Engineers harvest clean, continuous energy from air

#41

Post by pdonis »

AnimalMuppet wrote: post #34
pdonis wrote: post #31

Earlier quoted context omitted.

> Warmer if it's warm Yes, but not quite for the reason you give. See below. > colder if it's cold. This I don't agree with. Cold air can't hold any significant amount of water vapor to begin with. It is true that a cold, rainy day feels colder than a cold, dry day with the same air temperature, but rain isn't humidity; rain is water, not water vapor. > I think the deal is that it's more efficient at transferring hea…

Good explanation on the warm. I still disagree on the cold. The cold in the midwest cuts through you in a way that it doesn't in the dry. Air temperature's the same, but the difference is noticeable. Why is that? If not humidity, then what is it?

See my response to the sibling post to yours.

My experience in the Midwest (and elsewhere) on colder days is that the biggest factor is wind. Even a relatively light wind on a cold day can make a big difference in draining heat from your body. Convection makes a big difference in the heat transfer properties of air.

Btw, you say "in the dry", but have you ever been in the desert on a cold night? I think you might reconsider just how cold "dry cold" can feel.

Re: Engineers harvest clean, continuous energy from air

#42

Post by BobaFloutist »

pdonis wrote: post #29
raphaelj wrote: post #18

Something similar happened when I put a dehumidifier in my bedroom. Basically, I noticed that the room was heating significantly when I turned it on. Way faster than what you should expect from its power usage (about 250W avg.). Correct me if I'm wrong, but by converting air moisture to liquid water using a compressor, the dehumidifier is releasing the latent energy of water vapor (0.627Wh/L) in addition to its own e…

> by converting air moisture to liquid water using a compressor, the dehumidifier is releasing the latent energy of water vapor The latent heat does get released, but the question is, where does it go? In an air conditioner, which also condenses water vapor from the air, the heat released goes into the refrigerant, which means it ultimately gets put into the atmosphere outside from the condenser. A dehumidifier is ba…

I guess it's like a reverse swamp-cooler?

Re: Engineers harvest clean, continuous energy from air

#44

Post by gs17 »

Animats wrote: post #33
deegles wrote: post #2

The paper says a cubic meter of the material could generate more than a kilowatt (per hour?)... sounds promising if it actually gets commercialized. I assume it would only work well in places where there are significant humidity swings, I didn't read the paper very carefully though. https://onlinelibrary.wiley.com/doi/epdf/10.1002/adma.202300...

The good info is apparently in table S2 of "supporting materials", where they compare energy harvesting devices. That's not part of what you can read for free. Some kind of energy harvesting device that could generate a few milliwatts in ambient indoor conditions would be very useful. We have lots of things with AA batteries in them that use very little power but need a new battery every year or so. That's the potent…

I got a copy, it says "~0.0001-0.05" W/m^2 for their material, which they put at the same order of magnitude as "Hydrovoltaic" harvesters, and several orders below something like wind or solar. But they do list theirs as the only 3D scalable, "continuous and ubiquitous" harvester.

Re: Engineers harvest clean, continuous energy from air

#47

Post by hex4def6 »

Feeling a little skeptical, but I'd love for someone to explain where the energy is coming from. From the paper:

In fact, an Air-gen device made from protein nanowires, which was kept in the ambient environment for over 3 years, still produced a similar voltage output ...These time spans are much longer than the typical hydration time, supporting the sustainable mechanism based on a dynamic equilibrium ... The Air-gen device is not a “perpetual motion engine”, because the energy comes from the electrostatic energy (not kinetic one) of discrete water molecules in a vast open source.

Does this mean that the energy they're harvesting is a result of imparting a charge on otherwise neutrally charged water molecules, but because it's infinitesimally small compared with the "vast source", you can disregard any net effect from the perspective of the harvester?

If so, this doesn't feel "right", because this implies that a charged particle's state is at a lower energy state than a neutral one. If that were so, wouldn't the universe tend to that lower energy state by default?

Again, I'd appreciate if someone could tell me where the energy is supposed to be coming from, because "TANSTAAFL" seems to be being violated here.

Re: Engineers harvest clean, continuous energy from air

#48

Post by capitainenemo »

hex4def6 wrote: post #47

Feeling a little skeptical, but I'd love for someone to explain where the energy is coming from. From the paper: In fact, an Air-gen device made from protein nanowires, which was kept in the ambient environment for over 3 years, still produced a similar voltage output ...These time spans are much longer than the typical hydration time, supporting the sustainable mechanism based on a dynamic equilibrium ... The Air-ge…

Aren't they basically harvesting incredibly diffuse lightning? These charge imbalances that accumulate naturally before discovering that lower energy state dramatically?

Presumably it doesn't instantaneously happen due to insulating effects in the air.

Re: Engineers harvest clean, continuous energy from air

#49

Post by okwhateverdude »

gs17 wrote: post #44
Animats wrote: post #33

Earlier quoted context omitted.

The good info is apparently in table S2 of "supporting materials", where they compare energy harvesting devices. That's not part of what you can read for free. Some kind of energy harvesting device that could generate a few milliwatts in ambient indoor conditions would be very useful. We have lots of things with AA batteries in them that use very little power but need a new battery every year or so. That's the potent…

I got a copy, it says "~0.0001-0.05" W/m^2 for their material, which they put at the same order of magnitude as "Hydrovoltaic" harvesters, and several orders below something like wind or solar. But they do list theirs as the only 3D scalable, "continuous and ubiquitous" harvester.

Presupposing completely optimal 50mW/m^2, could you origami that surface? Because then you could probably have something pretty useful.

Re: Engineers harvest clean, continuous energy from air

#50

Post by aredox »

hex4def6 wrote: post #47

Feeling a little skeptical, but I'd love for someone to explain where the energy is coming from. From the paper: In fact, an Air-gen device made from protein nanowires, which was kept in the ambient environment for over 3 years, still produced a similar voltage output ...These time spans are much longer than the typical hydration time, supporting the sustainable mechanism based on a dynamic equilibrium ... The Air-ge…

The movement of the water molecules is what is generating the charge difference. In effect, this is using the wind - or just the movement of air, but not in a mechanical way. It is just using the wind to generate static electricity - the same way you generate an electric potential by rubbing felt on a balloon. Movement -> electricity.

Of course it is fairly weak, but it is continuous and simple. There has to be uses for it.

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