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Treehugger.com article on Waterseer

Wind-powered device can produce 11 gallons per day of clean drinking water from the air

[...]

The WaterSeer is relatively simple device, designed to be operated without an external power input, and without the need for costly chemicals or maintenance, that can 'pull' moisture from thin air and condense it into water using the temperature difference between the above-ground turbine and the collection chamber installed six feet underground. The potable water can then be delivered to the surface for use via a simple pump and hose, and the device is said to be able to produce up to 11 gallons per day, even in arid regions.

11 (US) gallons is about 41 litres, but the attached video makes a slightly more conservative claim:

Under optimal conditions, a single WaterSeer may collect as much as 37 L of clean fresh water every day

On the face of it, the device described in the video seems to be possible in principle, but thinking about it a bit more brings up some questions.

Has this device been proven to work? Are the claims correct?

  • I've edit the question a little, but I found it difficult because there is an inconsistency between the claim made by WaterSeer in the video [37 L, ideal conditions] and TreeHugger article surrounding it [~41 L, arid conditions]. – Oddthinking Oct 13 '16 at 6:47
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    I also have some doubts regarding purity. That big tank at the bottom seems like a great breeding ground for water-borne bacteria to me. I can't imagine the water produced would really be drinkable without the use of water purification tablets or boiling it before consumption. – GordonM Oct 13 '16 at 10:56
  • Some context: there's an older ,less complex, version of the video with different version which works on similar heat-sink principles:youtube.com/watch?v=sqCliCqYNd8 – Murphy Oct 13 '16 at 14:56
  • To the potential answerers: we don not allow answers based on "back of the napkin" calculations or simplified models. Answers relying on such will be removed. Read the FAQ here – Sklivvz Oct 14 '16 at 10:36
  • At least two youtubers have "debunk" videos of the waterseer, you might be interested in searching for them, they contain quite solid numbers – PlasmaHH Oct 25 '16 at 11:57
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I can't give a complete answer.That would require original research and/or actually testing a unit for an extended period of time.

But some of the statements on that page aren't correct and weaken their claims. I'm going to focus on a single one.

That link includes this picture.

waterseer

"because the sides of the underground chamber are always cooler than the air ,waterseer is always collecting water day and night, even when there is no wind"

The bolded claim is simply false.

A few feet underground the average temperature is (roughly) the average temperature at the surface over recent times (actually a fraction of a degree higher than the average).

Lets look at some example real data:

In this graph we can see an example of soil temperature above air temperature in april:

Air temperature example

It's affected somewhat by things like soil water content. Generally the greater the depth the longer term the average is.

soil temp 1

This graph shows something similar to above but it's more crowded. Even 4 feet deeper than this device soil temperature is higher than air temperature for significant portions of the year.

enter image description here

More theoretical:

During the day in summer the soil will be cooler than the air, during the winter or at night it will be warmer (mostly).

That's not entirely bad, I expect people need water the most when it's very hot in summer but at night don't expect this to work very well.

Water carries a lot of latent heat of vaporization and so you'd expect the soil around the chamber to warm up pretty rapidly to close to air temperature. You're basically taking advantage of the temperature difference but evening it out at the same time.

The more water you harvest and the faster you harvest it the faster you'll warm the surrounding soil to close to air temperature.

So be wary of any "tests" or short term demonstrations which show that it can harvest X amount of water in a day. They may be early on while the soil is at it's coldest vs the air before the machine has run for any significant time.

To get an idea of how much energy is being dumped into the earth around the reservoir if 37 liters of water is being collected:

If you had a small chamber 6 feet underground containing a small gasoline heater and burned 3/5ths of a galleon of gas each day every day to warm the surrounding soil you'd be in about the right ballpark.

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    This answer seems very theoretical to me. The first graph is only for one foot deep, not six. You'll warm the surrounding earth, but enough to seriously affect the operation? This is a warning that tests need to be done carefully, but not a convincing answer. – Oddthinking Oct 13 '16 at 11:34
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    @Oddthinking I've rearranged it to be a bit more clear, at least one claim their device rests on is simply false. With that false it cannot work as claimed "always collecting water" "day or night" but may work at some times of day at some times of year. I've put the more general problem with this at the end. The graph for 30cm is illustrative but ones for deeper are pretty boring, the line just gets flatter and flatter keeping closer to the average. – Murphy Oct 13 '16 at 11:47
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    @DJClayworth ??? but the system relies on water condensing on the inside of the underground chamber due to the cold. If the walls of the chamber get too warm then that doesn't work and the device doesn't collect water. Should I have been more explicit? – Murphy Oct 13 '16 at 13:53
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    It's almost certain that places where the ground freezes in the winter are not the target geography of this device. – DJClayworth Oct 13 '16 at 14:16
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    This answer is clearly not a complete answer to the question, as it says in the first sentence, but it clearly explains that a claim made in the advertisement is absolutely false. During the day the air is warmer than the ground. During the night, the air is cooler than the ground. The average underground temperature is about equal to the average year-round air temperature. It's not physically possible for the device to collect water 24 hours a day, as claimed, regardless of any heating effect due to condensing water. More work is needed to answer the question, but one claim is false. – Mark Oct 14 '16 at 12:23

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