And that takes a lot of energy.
So what is the purpose of this device? It can't be to provide potable water to areas without it, since those same areas are likely to lack a significant source of power.
I don't mean to be overly cynical, but I feel like I'm missing something here.
Typical coefficients of performance for air-source heat pumps, like air conditioners or dehumidifiers, are around 2; that means for every 2 joules of heat that it removes from the cold reservoir, it consumes a joule of electrical energy (dumping it as heat into the hot reservoir along with the heat it's pumping). The enthalpy of vaporization of water, at almost 41kJ/mol, is huge compared to the specific heat of air or even water itself, so that's a good approximation to how much heat you need to extract to condense the water. Water's molar mass is about 18 g/mol (two hydrogens of 1.0001 or so and an oxygen of 15.9994) so that works out to about 2.3kJ/g. At 10¢/kWh, this means your water costs 6.3¢/ℓ or US$78000/acrefoot.
This is a lot cheaper than bottled water, and a lot more expensive than what farmers can afford to pay for irrigation water, and a lot more expensive than reverse osmosis desalination, which I think is around $8000/acrefoot. (Corrections welcome!)
If we figure that a person needs 8 ℓ / day for cooking, drinking, and bathing (more or less what we use at Burning Man; if you're somewhere less hot and druggy then you might need less) which is about 210 watts. If a photovoltaic panel produces a 24-hour average of 13 W/m², which is what a friend of mine in England is getting, you need about 16 square meters of photovoltaic panels to power the device, which costs about US$2000 at this point. That's well within the bounds of feasibility, although it's a big enough asset to be a temptation to thieves.
So when you say, "I feel like I'm missing something here," I agree: you were missing quantitative understanding of the subject, and as a result your quantitative conclusions were completely wrong, even though they were based on correct qualitative understanding.
They operate by sucking air through a part of a rotating desiccant drum then exhausting it. At another spot, they heat and blow air through the desiccant, recharging it. The heavily moisture laden air is ran through a radiator where the moisture condenses out. If you have a source of low/medium grade heat, these can operate for the cost of running a few fans.
This type works actually can operate in colder climates as they can work down to near the freezing point of water, where the cooling type cannot operate when the dew point is below the freezing point of water.
Once the well is dug, cased, and the pump is installed there are very little operating costs especially with solar-powered electric pumps.
The math for a comparison between a well and this gizmo would be interesting.
I thought the same thing but reading their site led me to the above Wikipedia page which suggests there are other ways to do it than just dehumidification but I'm not sure what method they're using.
If it takes a lot of energy, and we implement carbon-negative power generation, then we increase the rate of carbon sequestration :)
https://openawg.github.io/#about
Which has a bunch of footnotes, many with one footnote per concept, where the footnotes are almost all wikipedia articles. Why don't you just link the words instead?
When I was drafting it in Google Docs, I was using footnote annotations, and I just copypasta'd it over.
[1] - https://en.wikipedia.org/wiki/Thermoelectric_generator
The initial proof-of-concept I threw together with spare parts actually used a spare TEC (19911-5L31-15CQ) [0] I had laying around. [1]
[0]: http://www.customthermoelectric.com/tecs/pdf/19911-5L31-15CQ... [1]: https://openawg.github.io/2016/01/27/blueice-alpha.html
edit Missed the note on turbidity. I'm guessing a follow-up test might show that resolved?
We're going to try and find another remineralization filter, or we might add electrolyte mix instead.
The second lab report was from the isolation of the remineralization filter, and we showed that the turbidity was indeed added by that filter.
Right now, for example in Tucson, AZ: humidity at 14% with a temperature of 76F and dew point of 24F. High will be 90F :( with Humidity around 6% mid-afternoon.
With 32.2C ambient, 14% RH, 1.35C DWP, the absolute humidity is 4.78 g/m^3
With 24.4C ambient, 14% RH, -4.80C DWP, the absolute humidity is 3.12 g/m^3
This is similar to the AH at BRC. Our current model assumes a DWP of -10C — 10C, so we can predict similar performance. We're not taking into account volumetric capacity and the thermal interface of the heat exchangers. If you know anyone able to help point us in the right direction with those calculations, it would be much appreciated!
Our current understanding is the enthalpy of vaporization + fusion for water is (2257 + 333.55) = 2590.55 J/g we want to pull out of the air. This is assuming we can process enough air, since the dew point is below freezing a fair amount of the time.
This is by using this equation specified in the NASA technical note [0]:
=((0.21668*((TMPC+273)^-1))*((DWPC+273)^-4.9283)*(10^(23.5518+(-2937.4/(DWPC+273)))))*1000
EDIT: Formatting is hard. Added source. Clarification.
A dehumidifier isn't a complicated mechanism. This is not a novel invention. It also isn't going to produce a sustainable amount of drinking water at a price affordable to the people who need it most.
The team running this seems to just be a group of friends who have none of the experience actually make a difference. We've got an Artist/Engineer, and artist, another artist, another Engineer and a product manager who have no meaningful job descriptions (apparently they "do things"), A "Web Engineer", and an advisor whose only task appears to be possession of knowledge of chemistry. It doesn't seem that this team was chosen due to what they could accomplish, but instead because they all pitched in to get an IndieGoGo project going...
I'll give them credit for their cause. At least their hearts are, presumably, in the right places, but this little device isn't going to change the world even a little bit. It would win the science fair without a doubt, but it's not much more impressive than that.
Definitely not novel at this stage, but once we modify the AWG to achieve water reclamation from urine, would that be considered novel?
The next milestone is to create open source designs for larger-scale, commercially available machines that are prohibitively expensive, and improve upon them. The machines exist and there is a market for them. Is it not worth the time and effort to increase access to technologies like this?
Not just knowledge of chemistry, but actively developing eyedrops to cure cataracts :)
http://www.viewpointtherapeutics.com/team/
EDIT: Wording. Added question.
That's for you to decide. There's nothing wrong with your project, I just don't see any real-world utility.
>once we modify the AWG to achieve water reclamation from urine, would that be considered novel?
Not at all. It wouldn't even be a "Atmospheric Water Generator" anymore. You would just be putting an evaporator in a closed space with your condenser... This isn't a new or novel technology, and it's already available for public use.
>Not just knowledge of chemistry, but actively developing eyedrops to cure cataracts :)
That's really cool, and I am not doubting her credentials, but it has nothing to do you with your AWG. We're talking about a device that condenses water vapor into liquid water. If you have access to Freon and and a pump (or even ice cubes and a glass) you can achieve the same thing.
Again, I don't take any personal offense to what you're doing. I would never invest in it because I don't think any amount of funding would ever turn this project into a success. It doesn't even address the real issues behind water scarcity, which has nothing to do with a shortage of liquid water...
I really like the idea of having open source infrastructure. I would like to see people build open source electric vehicles, farming robots, membrane bioreactors, etc. For the naysayers, at least two of these are already a thing: https://www.osvehicle.com/ https://farmbot.io/
Let's see how far these things get. Open source software has come a long way but there's a whole host of challenges with open source hardware projects which we haven't solved yet (open source toolchains for designing said hardware, open standards for modularity, collaboration tools, etc.). The only way we're going to overcome these challenges [and discover the ones we don't know about yet] is to try it.
To that end, I'm glad that this project IS relatively simple -- I think that increases its chances for success, especially considering that this is uncharted territory for most of the team members.
Moreover, there does seem to be a market for these things: http://www.grandviewresearch.com/industry-analysis/global-at... and I would expect that the cost of energy should eventually go down as we develop less naive means for generating energy.
I'm all for it. Work that dehumidifier.
TL;DR The meta problem of open source hardware is interesting in and of itself.
Are you talking about just the water generator, or the "civilization-in-a-box" collection of modules?
A good way to increase the efficiency of this machine would be to increase the relative humidity by adding moisture. This is the reasoning behind our next planned experiments of reclaiming water from urine!
You might be able to get away with using the reverse osmosis system we have, [0] but send the water to a lab to test influent (intake) and effluent (output) before consuming :D
[0]: http://123filter.com/catalog/ispring-7-stage-75-gpd-reverse-...
Absolutely love your project. I think its going to help a lot of people!
To put some numbers to this, they have achieved ~1kwh / L, wikipedia [0] puts reverse-osmosis desalination at ~3kwh / 1000 L
[0] https://en.wikipedia.org/wiki/Reverse_osmosis#Desalination
Wait, there's not a pH range limit on drinking water in the U.S.?!
I wonder how the current primary and secondary drinking water regulations came to be.
There are way more energy / cost efficient ways to produce water than a dehumidifier.
If you want to get into solving clean water; you really should be working on cheap energy.
Ideally, we'd like to use a gasifier for carbon negative power generation, as local biomass can be utilized.
Does this make sense, or do you have a more effective approach?
https://s-media-cache-ak0.pinimg.com/736x/83/a6/d9/83a6d9886...
Dehumidifiers are not designed to produce potable water.
Adding a filtration system removes the contaminants from the non-food grade components and anything else which was once floating in the air.
It's been a couple of decades since I took chemistry, but I think you've got that backwards.
