Atmospheric water generation

[ekelly36]

This may not be the right place for this but has anyone looked into the new atmospheric water generators? An interesting concept if they can increase the efficiency….

[GordMay]

Are you thinking of a solar thermal atmospheric water generation system, using some sort of heliostat [compound parabolic collector], or an electrically powered system?

[ekelly36]

Originally Posted by GordMay

Are you thinking of a solar thermal atmospheric water generation system, using some sort of heliostat [compound parabolic collector], or an electrically powered system?

Something like this,

https://us.watergen.com/mobility/watergen-on-board/

I was just Instagram scrolling and randomly had an ad pop up about a different brand. It was just completely random but the theory is sound depending on power usage. Since a boat is always in humid air the output would probably be pretty good as opposed to a dry arid climate. That one says 400w and solar compatible.

[dougweibel]

Looks like a great product for a motor vehicle driving around all day, or a power boat doing the same. Looks doubtful to have much utility for a cruiser. Power consumption is advertised at 480 watts and it produces 50 liters per day. Let's be generous and assume a "day" is 12 hours and not 24, then that is 1.1 gallons per hour.

My Spectra makes 15 gallons an hour at about half the power, so is roughly 30 times more efficient. Even a regular marine watermaker without an energy recovery pump, including the overhead of an inverter, would be many times more efficient.

[Pete7]

Originally Posted by dougweibel

Power consumption is advertised at 480 watts and it produces 50 liters per day. Let's be generous and assume a "day" is 12 hours and not 24, then that is 1.1 gallons per hour.

Sheesh, that's dreadful. Even the little Katadyn will produce that an hour for about 4A

[newhaul]

Originally Posted by Pete7

Sheesh, that's dreadful. Even the little Katadyn will produce that an hour for about 4A

Mine produces average 1.5gph using 3.8ah in 48°F water. ( power used will be lower per gallon in warmer water)

[SailingHarmonie]

480 W for 24 hours to make 50 liters?

That’s so terrible it defies description.

480 W * 24 hours = 11.5 kilowatt-hours of energy per 50 liters. Heck, just run your air conditioner and collect the condensate. That’s all this is.

At 12 volts that’s 960 Amp-hours per day. At 24 volts it’s 480 Amp-hours per day. That’s the entire capacity of my battery bank.

My RO unit makes 40 liters in an hour with 600 Watt-hours of energy. This unit uses almost 200 times the energy to make that much water.

There are lots of good reasons you don’t see these in use.

And what the heck does “solar compatible” mean anyway? This there any electrical device that is not “solar compatible”?

[newhaul]

Originally Posted by SailingHarmonie

480 W for 24 hours to make 50 liters?

That’s so terrible it defies description.

480 W * 24 hours = 11.5 kilowatt-hours of energy per 50 liters. Heck, just run your air conditioner and collect the condensate. That’s all this is.

At 12 volts that’s 960 Amp-hours per day. At 24 volts it’s 480 Amp-hours per day. That’s the entire capacity of my battery bank.

My RO unit makes 40 liters in an hour with 600 Watt-hours of energy. This unit uses almost 200 times the energy to make that much water.

There are lots of good reasons you don’t see these in use.

And what the heck does “solar compatible” mean anyway? This there any electrical device that is not “solar compatible”?

One thing is "solar compatible " means it has the ability to run directly off of solar alone . Don't need a battery or an in v erter to run it . Just enough solar to do the job.
Which in my experience 480 watts means a thousand watts worth of solar panels.

[SailingHarmonie]

Originally Posted by newhaul

One thing is "solar compatible " means it has the ability to run directly off of solar alone . Don't need a battery or an in v erter to run it . Just enough solar to do the job.
Which in my experience 480 watts means a thousand watts worth of solar panels.

My point is it is total advertising puffery. Anything is solar compatible, if you have enough solar panel capacity. A whole CITY is "solar compatible". I think the term is something they throw out there because it sounds good to the technically unsophisticated who are the target customer.

I think you are wildly optimistic in solar capacity needed. My 615 W solar panels generate about 3 kW-hrs on a bright sunny day. To supply this thing with power enough to run it twenty-four hours would need at least 2300 W of solar panels, pus a battery bank big enough to store more than half that.

But heck, if you have 3000 W of solar sitting around not doing anything else, it is "solar compatible".

[RaymondR]

Large central aircon systems on offshore vessels in tropical waters produce a surprising amount of condensation water. From memory 3-4 tons per day in the South Atlantic off the coast of Brazil.

[newhaul]

Originally Posted by SailingHarmonie

My point is it is total advertising puffery. Anything is solar compatible, if you have enough solar panel capacity. A whole CITY is "solar compatible". I think the term is something they throw out there because it sounds good to the technically unsophisticated who are the target customer.

I think you are wildly optimistic in solar capacity needed. My 615 W solar panels generate about 3 kW-hrs on a bright sunny day. To supply this thing with power enough to run it twenty-four hours would need at least 2300 W of solar panels, pus a battery bank big enough to store more than half that.

But heck, if you have 3000 W of solar sitting around not doing anything else, it is "solar compatible".

You are not getting what solar compatible means it means exactly this it can run directly off of the solar panel output no battery or anything now won't work outside of daylight hours .

[catalystcat]

ANOTHER LONG AND PROBABLY BORING TECH ANALYSIS


There may be some good use cases for this technology.

(BTW - Here is another company who is reporting higher performance with a major gotcha -
https://aquaria.world/faqs/ . They are claiming 5l/kWh. The gotcha is that they require a very large surface area, like your home's backyard.)

There are some real limitations here.

First, the efficiency is very low. To start with, it doesn't commit to 50l/day. It is "up to" 50l/day. That implies under somewhat idea conditions - i.e., 24 hrs operation; high humidity; warm conditions. (kinda like the environment of the ACs in Brazil noted above.) For non-ideal conditions, that number would be lower.

An indication of how that would work in real life is that they require a minimum humidity of at least 20%. But, their ideal would be around 100% RH.
Since they are using condensation from environmental air, that means they are relying on what might be called their dew point. To make this work, they are imposing a temperature differential to induce condensation. The rate is highly dependent on the relative humidity. https://www.researchgate.net/figure/...ig12_261716067

Forcing a delta-T takes power.

What do these items mean? It means you should derate the performance according to your use case.

First, power -
It consumes a lot of power per liter for a reasonably portable size. If you have power to burn, this might not be a big deal. They try to get around this by noting the solar compatibility. That gives you (arguably) free power for about 8-12 hrs/day.
So, with almost free power, e.g., you are running a motor yacht or on road vehicle around the clock, you can get your 5l/day in ideal environmental conditions. If you are doing solar (sans batteries) you'll get maybe half of that.

Second, the yield rate -
yield rate drops as you move away from the ideal relative humidity/temperature. As shown in the chart in the link above, that can be several hundred percent if the RH drops from 100% to something like 40%, especially if you are forcing a large delta-T (31 degrees is the largest curve in the chart).
If you don't force a large delta-T, the performance gets bad pretty quickly (see the bottom part of the chart). Not sure how much they get from their 480W, but, I would suspect it is not that high. (See note on their proprietary technology below).

Overall, that means you'll likely average something like half that ideal number (total SWAG on my part) if you are lucky and operate in relatively warm, fairly humid places. Halve that again if you are using solar (without batteries).

The bottom line is that it can work if you have extra power, something close to a tropical environment, and you really value a few liters of water. (e.g. DARPA - https://www.darpa.mil/news-events/2020-12-18 )
Or, if you have a gigantic surface to work with that already does a lot of cooling, like a gigantic cooling system/AC, you could do this at a larger scale, with less cost.

For boats, you are sitting on a giant pile of water and RO systems work. So, it's hard to see how this competes well for boats.


************************************************** *******
SEMI-RANDOM NOTES

Note re: their "proprietary technology":
Their big technology is their proprietary heat exchanger that preheats and pre-cools interleaved branches (it's explained in their patent) to improve condensation efficiency, in part by inducing a larger delta-T. It's a kinda clever form of counterflow heat exchanger. But, note that to get good efficiency, they need to keep delta-T high from inlet to output. That's hard and any inefficiencies hurt the system performance.


Note re: possible paths to more commercial applicability:
I note that if they were to use some microfluidics concepts (e.g. switchable hydrophopic/hydrophilics; or Tuckerman's microchannel heat transfer) and could scale them up commercially, they could likely improve performance.