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Show HN: Open-source atmospheric water generator – first lab reports

openawg.github.io

The problem places have with lack of good water; is a lack of money. Not a lack of water.

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.

Our current approach is to get the AWG module working, then add a module which boils urine and feeds the vapor into the AWG module for distillation and filtration.

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?

Like I said.. There isn't a 'lack' of water.. there is a lack of energy for purification in rural places.. In these places you should be figuring out purification via chemical and physical methods.

https://s-media-cache-ak0.pinimg.com/736x/83/a6/d9/83a6d9886...

Hey everyone, I'm around for a bit to answer any questions you might have :)

How does it taste? :) And what plans do you have for tackling the pH and turbidity level issues?

edit Missed the note on turbidity. I'm guessing a follow-up test might show that resolved?

It tastes surprisingly good, although not as good as some of the Ozarka bottled spring water I've had, but almost.

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.

That's great! I had missed the test0 procedure text, but it did seem clear after reading it.

So... this is basically a dehumidifier. Dehumidifiers typically use some sort of air cooling to reduce water below the dew point to draw water out of the air.

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.

https://en.wikipedia.org/wiki/Atmospheric_water_generator

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.

For simplicity and adoption, we're utilizing mechanical refrigeration since parts and HVAC(R) skills have been widespread over the past several decades.

EDIT: Spelling is hard. Clarification is hard.

It has Wi-Fi

Indeed. Ideally, we'd like to include a mini-datacenter module, allowing for data storage, streaming, and processing.

We'd like to be able to gather metrics from these machines all over the world, and identify trends in things such as the weather, water production and consumption, efficiency, power generation and carbon sequestration, as well as identify opportunities to improve the operation of the machines through software updates.

Indeed, it is energy intensive. That can be addressed with the implementation of the power supply module. Ideally, we'd like to use gasifiers and build upon the open source work by http://www.allpowerlabs.com/

If it takes a lot of energy, and we implement carbon-negative power generation, then we increase the rate of carbon sequestration :)

It's also going to be the centerpiece for a water-conscious art installation addressing the global water crisis at Burning Man, pulling water out of some of the driest air on the planet :)

I agree with you... Why not dig a deep well and run a solar pump? Around Tucson... I have friends that have +400ft. deep wells that cost $60k to install. Seems expensive... but we are talking +35gpm all day long/

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 would like to see that comparison as well!

I'm not sure how to determine the practicality of well excavation, but my intuition tells me it largely depends on geographically influenced factors. I'll look into that.

An AWG is rarely the most efficient solution, but sometimes it's the best solution.

If you're not going to be in a particular area for very long, digging a well might not be an option. An AWG can collect water while you're moving -- all you need is access to air.

If you find yourself in an area where the water table is contaminated, using an AWG may end up being the safer option.

Imagine you're living in space (or a similarly resource-constrained environment): you've got multiple people losing something like 0.5+ L/day (citation needed) to the air through perspiration -- that's valuable water. Moreover, to keep people comfortable, you should make sure your relative humidity stays below 60% (citation needed), so you're going to be pulling it out of the air anyhow. NASA undoubtedly has these systems in place in space, but that doesn't mean we should develop a open source version of the equipment that everyone can collaborate on and improve.

TL;DR Sometimes you're willing to trade energy for water. Also, open source.

If you're digging a new well, you should see if you can do a ground source heat pump to get heating and cooling out of it at the same time.

Most of the startup cost is in digging the heat exchange loop.

https://en.wikipedia.org/wiki/Geothermal_heat_pump

There are rotary desiccant dehumidifiers that do not cool the air, but heat it.

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.

Whoa. That is cool. Where can I read more about this, and are there any designs available to peruse?

The technical term for them is adsorption dehumidifier.

Here is a video of a guy tearing down a typical household unit and he explains the basics of operation:

https://www.youtube.com/watch?v=mR57FhytzFk

We have a couple of Meaco DD8L desiccant humidifiers - they are fantastic. Quiet, efficient and they each suck a few litres of water out of the air each day.

Enhancement request: support for desiccant module

I will definitely look into that, and probably test a commercially available model or two.

If you end up beating me to it: https://github.com/openawg/openawg/pulls

Let's quantify "a lot of energy": the dehumidification part is 210 watts per person. Maybe Clay can provide actual power consumption numbers that include the other parts of the system, such as filtration.

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.

Love your math. Something to consider is the excessive amount of wind power being generated in certain parts of the world right now. If you can't move that power somewhere, could use it to extract fresh water from the atmosphere rather than curtail production.

That is awesome! We'd love to have a chat with you to better understand your thinking process, perspective, and sources.

The pump were using right now consumes 104 W intermittently. For our next prototype, we're going to use a condenser unit from a walk-in freezer (1168W), a split A/C unit to pretreat the air (560W) MinnowBoardMax (15W), duct fan (208W), etc.

Awesome! I'd totally be up for chatting. How much water does it produce?

So for one person you'd need $2000 worth of solar panels, 16 square meters of panel.

One person.

It seems like you've supported my point, not refuted it.

But I appreciate your analysis, even if I dispute your conclusion! Thanks!

It's kind of like the Tesla, which people think is amazing. For $90k you could also buy a $60k car and $30k worth of gasoline up-front and tada! you can now refuel it for free or almost free (it takes a little energy to pump the gas out of the underground storage tank and into your car's gas tank).

Does US$2000 per person for the energy to solve the potable water problem for 30 years seem like a lot to you? Compared to the cost of other survival necessities (housing, food, sanitation, heating, cooling — http://resiliencemaps.org/) it's quite reasonable. 16 m² is also pretty small compared to the space customarily used for housing.

However, I made an error! It turns out I left out the coefficient of performance in my calculations. So it's actually 105 watts, 8 m², and about US$1000:

    You have: (8 liters / day) * (41 kJ / mol) / (18 g / mol) * (1 g / cc)
    You want: W
            * 210.90535
            / 0.0047414634
    You have: (8 liters / day) * (41 kJ / mol) / (18 g / mol) * (1 g / cc) / 2
    You want: W
            * 105.45267
            / 0.0094829268
    You have: (8 liters / day) * (41 kJ / mol) / (18 g / mol) * (1 g / cc) / 2 / (13 W / m^2)
    You want: m^2
            * 8.1117442
            / 0.12327805

My guess of US$1000 for 8 m² is based on my guess that 8 m² is about 8000 watts of solar constant, and at 16% efficiency that's 1280 peak watts, and people quote PV modules as below US$1/watt, which I assume is a peak watt. The actual price right now is about US$0.55/watt, depending on where you are, so a more precise estimate is actually US$700:

    You have: 8000 watts * 16% * $ 0.55/watt
    You want: 
    	Definition: 704 US$

My friend who's getting those 13 W/m² has her panels in England, though. So that's kind of a worst-case number. You'd need a fraction of that (like, say, 20% or so) in an equatorial desert.

If PV modules return to their previous price trend (they were dropping fairly smoothly by 36% per year in 2010-2013, but have been nearly plateaued since hitting grid parity in much of the world in 2013 and therefore having a hard time with capacity keeping up with demand) then they'd drop by another factor of 4. The Credit Suisse doc posted earlier today to HN https://doc.research-and-analytics.csfb.com/docView?sourceid... about how we are now in a "solar manufacturing oversupply" situation suggests that something like that might actually happen. Like what happened to DRAM prices in 1996 after the price-fixing cartel collapsed and they went from $40 a meg to $10 a meg almost overnight.

Not likely to work well in place like Tucson, AZ... due to the consistently low relative humidity or am I reading this wrong?

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.

Interesting.

  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

Absolute humidity here is specified as grams of water per cubic meter of air.

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

[0]: http://www.nasa.gov/centers/dryden/pdf/87878main_H-937.pdf

EDIT: Formatting is hard. Added source. Clarification.

Physicist here. I'm confused why you are using the enthalpy of fusion in your calculation, since your project does not appear to be freezing the water after condensation. Also, you seem to be using the enthalpy of vaporization from boiling at 100 C in your calculations, which is incorrect for use around 30 C.

A better way to calculate your energy needs would be to look at a steam table, such as the one on Wikipedia's water data page, then take the deltaHvap. This is the accurate enthalpy of vaporization. https://en.wikipedia.org/wiki/Water_%28data_page%29

In theory you need to add the amount of energy to cool the air/vapor mixture to the dew point. However, this amount will likely be small enough to be within your experimental error. For low humidity applications (like Burning Man), you can assume you are cooling mostly air, which is around 1.2 Joules/K per m^3. At 30 K temp differential, and humidity of 4 g/m^3, this is only 9 joules per gram water, or pretty much negligible.

So, you are looking at a deltaHvap of around 2420 to 2450 J/g in this temperature range. This is reasonably close to your original estimate of 2590 J/g, and the good news is that the error is in your favor.

Thank you for the feedback, this is awesome!

There is always more to read up on and calculate :)

EDIT: The current dehumidifier does accumulate ice on the evaporator coils, depending on the ambient conditions. Once enough ice has accumulated, the compressor turns off and the ice melts into the collection tray. I'm assuming we have to depose the ice out of the dry atmosphere at BRC, since the dew point is below the freezing point of water. Is this not the case?

If you aren't trying to make ice, then the energy which goes into making ice is waste. This cuts your efficiency. So, in that case, you do need to include the enthalpy of fusion in your calculations, just be aware that portion is waste. In fact it is doubly wasteful, because the ice reduces the thermal transfer rate and having to stop the compressor means your duty factor is lowered (less water per hour for same size machine).

There are ways to prevent this, although I'm not sure if they would work for your project. Adding salt is a classic, so you can supercool your water while remaining liquid. That's probably not great for drinking water, even with RO. If you can use the melting of the ice as a source of cooling, you can recycle the enthalpy of fusion. It really is a waste and you don't need to pay it. One way to do this is to use the melting ice to lower the heat rejection temperature of your compressor.

However, it may not be worth adding complexity just to cut your energy costs by 15%.

Would it make sense to use a reversing valve and use the hot fluid to melt the collected ice?

Agreed that it'd be better not to freeze the water at all, but that might be difficult at low dew points.

Have you thought about using an attached TEG [1] and a few 9volts to increase the amount of water produced as an optional strap-on.

[1] - https://en.wikipedia.org/wiki/Thermoelectric_generator

Interesting. I haven't thought about combining it with the mechanical refrigeration process! I'll run the numbers on that, thanks.

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

That's basically the same thing as what I'm asking. I'll be happy to read the numbers when you get it going.

I have a question about your website. While trying to figure out what exactly you're doing i browsed around a bit and eventually ended up here:

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?

Ah, that makes sense, thank you for the feedback.

When I was drafting it in Google Docs, I was using footnote annotations, and I just copypasta'd it over.

Would it be possible for me to use something like this on a boat I live on to generate fresh water?

It would, but it would most likely be less efficient than filtering the water you're floating in :)

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-...

Thanks for the reply! I'd of course use a watermaker first (very simple operation, relying on only a pump and a membrane) but its always smart to have redundancy in life critical systems ;)

Absolutely love your project. I think its going to help a lot of people!

Thank you! I hope it does too.

lol, that does desalination?

It probably does, but not as effectively as a marine-grade watermaker.

http://www.westmarine.com/watermakers

> It would, but it would most likely be less efficient than filtering the water you're floating in :)

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

Can you please explain how this differs from a dehumidifier?

The only difference is the addition of a filtration system to render potable water.

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.

> pH does not have a MCL (Maximum Contaminant Level) defined in the EPA's National Primary Drinking Water Regulations [...] but does have a [..limit defined in..] non-mandatory guidelines for aesthetics

Wait, there's not a pH range limit on drinking water in the U.S.?!

Right? I was thinking that was quite odd as well.

I wonder how the current primary and secondary drinking water regulations came to be.

If I had to take a guess, the EPA probably issues MCLs for acids and bases and not the resulting pH of them combined.

Probably because distilled water with no buffering salts can have a huge range of pH and is effectively harmless.

Ok, I really hate to shit all over somebody else's livelihood, but this whole project seems like a total waste of time.

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.

Where should we spend our time instead?

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.

>Where should we spend our time instead?

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...

> This isn't a new or novel technology, and it's already available for public use.

Can you point me in the direction of this project? I'd like to see what the current implementation looks like.

> (or even ice cubes and a glass) you can achieve the same thing.

We're trying to do it at scale and improve on the technology.

> real issues behind water scarcity, which has nothing to do with a shortage of liquid water

Can you elaborate on this point?

I'd agree but, isn't it open? You could go and help them.

It's not that I think their AWG isn't good enough, it's that I think a AWG isn't the answer to the problem they're addressing.

Agreed that the problem being addressed is not stated clearly enough.

If the goal is to provide clean drinking water in emergency situations, then this could definitely help. If the goal is to provide a sustainable source of clean water for a large population, then this is not the solution (there's a pun in there somewhere).

Regarding emergencies... no electricity generally. So, how about this: http://www.ezwaterwellhandpumps.com/ for approx. $169.

The only downside is that the water table needs to be relatively shallow

Interesting. How often is the groundwater potable during an emergency situation?

Since it's intended for an art installation, any shortcomings in the actual functionality of the device can be excused with the magical phrase "we're trying to start a dialog / get people thinking about X, not actually do X"

Doesn't seem much different than a normal venture capital startup with no viable product er marketing hype as a platform.

That's a pretty good comparison, I like it!

Agreed that AWGs, especially vapor-compression systems, aren't exactly mind blowing technology, but I'm excited for this for a different reason:

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.

> but this whole project seems like a total waste of time

Are you talking about just the water generator, or the "civilization-in-a-box" collection of modules?

It's an art installation at Burning Man, not a livelihood?

> The lower the pH, the more basic the water.

It's been a couple of decades since I took chemistry, but I think you've got that backwards.

Oops, thanks for the feedback. Fixed :)

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