> dehumidifiers already do a good job of getting water out of air for the energy price you have to pay
They do a terrible job. Condensate dehumidifiers are as expensive to run as an AC, produce unwanted heat, and are noisy. Dessicant dehumidifiers are even less energy-efficient.
If there's a way to extract moisture from the air with less energy and less noise, that would be huge.
Less energy would definitely be a huge plus but unless this violates our understanding of thermodynamics there will still be unwanted heat put out into the air. The heat from a dehumidifier comes primarily from the latent heat in the water being released so that the water can become liquid. This heat must be released somehow in this process unless they actually did find something that breaks our understanding of physics.
Obligatory Technology Connections video on the topic: https://www.youtube.com/watch?v=j_QfX0SYCE8
That's true, but I was under the impression that most of the heat generated by current compressor dehumidifiers is just waste heat from the mechanical operation of the compressor itself. The phase change heat is there too, but it's significantly less. So there should still be a lot of room for improvement, theoretically.
Yeah, there's certainly some of that, but going off of Alec's numbers and trial above you end up with a larger portion coming from the latent heat than from the mechanism, for the same reason that a heat pump is more efficient than an electric heater: it's condensing more water than it is running mechanisms.
That said, his demo is not under typical operating conditions in that a dehumidifier is normally expected to actually be able to catch up and reduce humidity in the room, while his demo ensures that the humidity levels stay high throughout the hour. So it's likely that under normal operating conditions the mechanism's proportion of the waste heat is higher than it is in his demo.
> That's true, but I was under the impression that most of the heat generated by current compressor dehumidifiers is just waste heat from the mechanical operation of the compressor itself.
Nope. It's almost all (>80%) latent heat. I believe, the theoretical limit is around 90% for typical room temperatures.
>The heat from a dehumidifier comes primarily from the latent heat in the water being released so that the water can become liquid.
A dehumidifier movies heat from one side to another using electricity to do the work. One side gets cold so the water can condense on it, while the other side gets hot from extracting the heat from the cold side. Heat is still generated from this process even if there are 0 water molecules in the air and no water is collected. The water does not create the heat, the electricity does.
I don't think there has to be any heat involved with collecting water molecules in the air into a larger volume of water, depending on the process used.
> I don't think there has to be any heat involved with collecting water molecules in the air into a larger volume of water, depending on the process used.
For the water to condense, there must be heat given off, unless I’m fundamentally misremembering my high school physics class.
state change takes 63 calories per cubic centimeter of H2O unless I am misremembering my high school science class.
at least for water solid to liquid
Both processes create/release heat, and in Alec's tests in the linked video the bulk of the heat from the dehumidifier running in a humid space is coming from latent heat released from the water. That may not be true in regular operating conditions, but there will always be a substantial amount of heat released from the water when you trigger a phase shift.
> I don't think there has to be any heat involved with collecting water molecules in the air into a larger volume of water, depending on the process used.
The only other option is to increase the pressure in the room or in a space within the room, which this material pretty clearly isn't doing.
It’s not just the electricity creating the perceived heat https://en.wikipedia.org/wiki/Enthalpy_of_vaporization
If water changes phase from a gas to a liquid, it releases a large amount of energy (enough heat to heat five times as much water from 0 to 100°C). That's likely far more heat than the electricity generates - though, of course, the heat released by electricity is very real as well, and as you say will even happen if the air is completely dry.
Possibly this doesn't happen if the condensation happens in a capillary (there is some funkyness related to energy levels), but then it must stay trapped there.
> If there's a way to extract moisture from the air with less energy and less noise, that would be huge.
Less noise: I agree, but you still need some air flow so the corners of the room that are far away also get dehumidified. Perhaps a slow fan in enough, and when you run them slowly they are quieter.
Less energy: It's not clear that this uses less total energy. It's easier to imagine what is happening if you compare it to a high tech Dehumidifier Bag. https://www.amazon.com/Wisesorb-Moisture-Eliminator-Fragranc... But instead of sending the drops down, they get attached to the device. You can use it only once unplugged. Then you have to buy a new one or use energy to extract the water (like boiling the water of the dehumidifier bad until you get the crystals again). It's not clear if building a new copy of this is cheaper than building some new calcium chloride salts, and/or if regenerating the new device is cheaper than regenerating the calcium chloride salts (that is usually not done).
So, is this new method less noisy and/or more energy efficient? The article doesn't really say.
>without the need for any external energy.
That sure seems to imply that there's no need for a noisy and power hungry compressor.
It also seems to imply that it violates thermodynamics.
It takes energy to condense water, so where does it get it? If it isn't external, it runs out.
Condensation of water is exothermic. If you add a cold thing to the environment, ie, remove heat from the water, the water will condense all on its own. This reaches steady-state when the cold thing is warm and the water is condensed. No thermodynamics issue!
They’re claiming they have a material that will do it at higher temperatures. Assuming such a material gets hotter as it works, there’s no thermodynamics problem here.
> They’re claiming they have a material that will do it at higher temperatures. Assuming such a material gets hotter as it works, there’s no thermodynamics problem here.
That's ok, but the amount of water you get is fixed - the process can't continue. You install the device into your room, it condenses 1L of water as droplets on its surface (or, more likely 1ml of water), and it's now done, that's all the water it's going to remove/produce, if this is the right explanation. It would be perfectly equivalent to bringing in a cold slab of metal from your fridge into your room - it will condense some water as it gets hotter, and it will eventually get as warm as the room and stop condensing anymore water, forever.
Conversely, if the process were continuous (say, as long as you remove the condensed droplets, new droplets form), as they seem to claim, that would very likely violate thermodynamics again.
What about entropy? The reason you need to power AC for example is that if you didn't you could reduce entropy and generate power for free, and basically reverse time.
The amount of entropy in a closed system is not allowed to decrease, but it is allowed to be constant. The amount of energy released by the phase shift is equal to the amount of energy absorbed by the object as heat.
Sure, but then the temperature of the object has to increase. And as its temperature increases, it has to stop condensing water - at the very least, once it reaches ~100C, it will instantly boil off any extra water that it condenses.
You are super confident a thing that exists can't exist
https://en.wikipedia.org/wiki/Air_well_(condenser)
Check out the passive section of the above
Especially for somewhere like UAE that in summer has the upsetting combination of massive humidity, no rain, and huge water demand.
Someone here once posted a link to a story[0] about the Persian Cooling Towers, that you see all over the ME.
Thousands of years old, I think.
[0] https://www.bbc.com/future/article/20210810-the-ancient-pers...
Perhaps OP was describing "swamp coolers" — or evaporative cooling?
That's the exact opposite of extracting moisture from the air.
Running a swamp cooler + dehumidifier that doesn't heat up would mean being able to do self contained cooling which would be a massive thing. Currently the only way to do that is with desiccant which needs recharging too often to be practical.
Tech Ingredients demonstrates how this works: "Revolutionary Air Conditioner!"
> If there's a way to extract moisture from the air with less energy and less noise, that would be huge.
I vote we write to our legislators to update the laws of thermodynamics to enable this. Typically I would agree we should leave well enough alone, but in this case it seems like the benefits outweigh the costs.
That's not how the laws of thermodynamics work.
In reality, you would need to convene an international consortium to approve to the change, and the Chinese wouldn't sign on unless we agree to a temporary suspension of Newton's third law.
We would only need a committee's approval if changing it would break things.
I say we skip that process, test it in a lab somewhere in rural midwest where nobody lives, and see if gravity starts changing or whatever. As long as cows don't start to float in a 3 mile radius within 4-5 hours, that's probably good enough validation to move forward with changing thermodynamic legislation.
[edit] we should also probably make sure the boiling point of water stays the same
I’m not sure the constitution grants Congress that power.
They already weighted in on the definition of π so why not?