Is It Possible to Capture and Condense the Vapor from Sea?

The production is going to be dependent on the area of the still's plastic, the moisture content of the ground, and the irradiance of the Sun.

Not ground; sea water.

You did not stipulate that. The article you linked gave that figure for a hole dug in the desert, not the ocean.

Yes, that is correct.

Unfortunately, I assumed that the more astute among you would instantly recognize that the OP is proposing a solar still for ocean deployment, given the OP's obvious reference to "sea", and that Wiki addressed the issue at hand, though not specifically the source of said humid air.

I'll concede that you were addressing me, specifically, so there.

I am vindicated!!! :)

Well, thanks for giving me a big smile. :)

Lyn's so darned smart, sometimes he forgets to explain things to the rest of us.

I knew you wouldn't get it.!!!

He's like the Dr who of forums only without the personality!

No, he's like the Dr. Know of forums only without the humor.

No, he's like the humor of forums, only without the Know.

Could be worse. I am married to Captain Obviouses sister Clueless Clara.

I finished wiring the home air conditioning power line today and told my wife that air conditioning is now working in the house.

What house? Was the response I got while she was standing right in front of the air conditioner vent while it was running and blowing cold air.

Have you built the house around the air conditioner, or did you wire up a solitary air conditioner in the middle of a corn field?

Yes on sea water…

Compared to the 'solar still experiment by National Geography':

1. Sea is expected to emit large amount of vapor compared to earth.

2. The condensing is more positive, since by cold water, compared to current of ambient air circulation.

3. By rowing the still/platform slowly we might capture huge quantity compared to a fixed location on the earth.

4. And the size, imagine a huge size (10000 sq ft or more)…

"And the size, imagine a huge size (10000 sq ft or more)…"

And the money, imagine the money, 100000 sq $ or more....

Number 3...

Explain that logic, please.

"By rowing the still/platform slowly, we might capture huge quantity compared to a fixed location on the earth."

If the still/platform is anchored in one place, the space underneath might get cooled eventually and lose the ability to emit considerable vapor. So the suggestion: to row it at very low speed to new area which is fresh and emitting huge vapor.

Tornado, rajeswari and many feel, "THEORITICALLY Possible. But COST wise WILL NOT FEASIBLE or VIABLE".

Yes, I agree. Who would have predicted a tiny solar cell (when invented) or wind turbine could have come this long way as to supplement the thermal and atomic power plants?

Kris says, "there is some sort of large array in the Saudi area'. Obviously at Saudi Arabia like places there is no iceberg. What is the average rain fall at Middle East? Still they have the need and money too…

Vapor emissions will not be better when moving due to currents and the dynamic nature of the ocean.

Leave it in one place.

How would this compare to a R.O. system?

Unless the capture area is HUGE, the ocean current will keep the water moving enough so that there is no loss of temperature,

However, the big flaw with your idea is absolutely no data to back up or substantiate your claim that there would be a loss of efficiency.

What exactly is a "huge" quantity compared to a fixed location? Calculate it.

I think that you are working on a problem (desalination) that has huge merit and is a very important project. If you want to make a contribution in this field you should consider more research in the field to understand what the current state of the art is, what the design and implementation issues are, and relative costs associated with the various approaches.

I used to have one of these on my boat....It seems much simpler than what you are proposing....

http://www.watermakers.com/

Personal Desalination Pumps

Of course.

You've re-invented a very slow method of distillation.

I thought that's how the evaporation and rain parts of the water cycle worked on this planet?

As far as fresh water on this planet goes we do not have a supply problem being the average nature is supplying is something like 25 - 30 thousand gallons per day for each and every one of us 7+ billion people here.

The problem is largely management related.

You beat me to it, I was about to post - Yes, it's called rain.

The problem you would have with such a setup, besides the lack of efficiency, is algae growth....it would quickly cover the glass surfaces....however this freshwater from seawater is being done on a large scale via reverse osmosis and many other methods....

http://news.nationalgeographic.com/news/2011/08/110804-fresh-water-crisis-desalination-environment-science/

http://en.wikipedia.org/wiki/Desalination

Some good answers already, and I've not even clicked Solar's links yet. There is something of this nature on another thread a year or so back. Hangover is currently preventing my brain from recalling the specifics, but there is some sort of large array in the Saudi area - wind blows in the water laden air, and the sun causes condensation etc. Brain consigned that to the 'interesting but not practical' zone.

I'd maybe try to find that thread, but "The whole platform may be rowed slowly"....That sounds horribly like a scene in Ben Hur or some such film. If my head ever stops aching, there is also another very serious idea about ships with some sort of funnel arrangement. If I can get a few more coffees down my neck, I'll try find it. The article was in a reputable journal a couple of years ago. As with electricity, the problem may be in the costs of 'where you can produce it versus where it's needed'. All said and done, I suspect that towing an iceburg may be cheaper.

This desert method works best at night. The temperature drops and the moisture condenses. In Chile they used large vertical panels of fine gauze, and the water dripped into a tray at the bottom of the panel. The sea air came in as a mist.

The Romans used, but this was in Britain, dew ponds, which consisted of metal cones set on a horizontal circular wall. Condensed moisture ran to the centre of the cone and into a receiving tank underneath.

The Roman thing is interesting. I've never seen such, and can't think why on earth they would need it in rain-sodden Blighty. Any links to hand ? Maybe it goes back to viticulture and drier climes in the South (which is also largely chalkland and soaks up any rain that falls)

One of natures ultimate ones seems to be the Atacama. Plenty of plants, but a conspicuous lack of rainfall. As you say, it's all about moisture condensing out of the air. Sea mist rolling in and all that. Whilst looking for a link on that I found something else that was quite a good read.

The Roman dew pond was mentioned either in New Scientist (most likely) or Scientific American. Can't remember when.

If your ship sink, and you are lost at sea and have little to no water, then this is exactly what you do to save yourself and others on board...

Dear Mr.yesyen,

THEORITICALLY Possible. But COST wise WILL NOT BE FEASIBLE or VIABLE.

RAJESWARI.D.

yes its called rain

Haven't had the time to do any theoretical mathematic engineering but from my experience as a sailor for the past 60 years (I started young) I would say no! To have PV panels of sufficient size to operate the pumps to raise the salt water up to the panels would have the panels too large and heavy for the floats to support your above water parts of your apparatus. The floats must displace enough water to keep the apparatus afloat (including their own weight!). The capacity of your apparatus is dependent upon the size of the PV panels and the condensation area. As the capacity increases so does the weight and therefore the floats must be larger. Boats (not ships) who use PV panels to power water purification usually have slow rates and utilize storage and judicious use of the resultant water to obtain fresh water. The alternate is to use the heat generated by the engine cooling system to heat the water.

At a minimum you would have to use 3 floats. The fewer the floats the less stable the apparatus will be. Conversely the more floats you have the greater the weight/displacement is. The best shape for the floats would be as spheres since they have the lowest ratio, not the cylinders you have illustrated.

From a theoretical standpoint it may be possible in a laboratory environment but from a practical standpoint no. From the sailors standpoint it is another TITANIC!

Good Luck, Old Salt

I think it is not a completely crazy idea. Solar stills have been used for many decades in lifeboats, voyaging sailboats (for backup/emergency purposes) etc.

You can buy one here, and play with it to get a feel for feasibility on a larger scale.

$240! Yikes!

From the ad, "...and has been used by military and civilian services throughout the world for the past 40 years."

And it appears to be used as well. :)

Lifeboats usually have a length of 25' up to 50' with a much larger displacement making them a much bigger and heavier platform. This also true of a voyaging sailboat (minimum of 30' up to and exceeding 70'). They also have a much larger surface area on the decks and cabin top for mounting panels. The extra weight for the panels and displacement, is insignificant on a life boat or voyaging sailboat. This is a much different platform than the OP has illustrated and the extra weight is a much higher % of the total weight. This is my reason for calling it a Titanic.

The unit you have referred to is $239.95 for a capacity of 1 to 4 pints of water daily. To use this as a model for a larger unit would produce a very expensive and not very durable unit. I do also note that they do not state the in use size, only the stowage size. It may have been used by the armed forces for over 40 years but that is an entirely different environment than floating in water. The waterborne unit must float, it is not staked into the ground with unlimited area usually available.

Having sailed from the New Jersey and New England to Bermuda and back several times I have some experience in the waterborne environment (that's why my friends refer to me as "Old Salt"). I'm by no standards an expert, but based on sea conditions from becalmed to 15' waves this unit is not going to be feasible to make, float, produce a usable quantity of water or withstand any sea conditions other than becalmed.

I wish this sort of unit was feasible and available but there are to many laws of physics and impracticalities that say NO, Another Titanic!

Good Luck, Old Salt

You seem to be repeating yourself. I was responding to the OP's question "Is it possible..." not to your post. Yes, it is possible, and small versions of such devices are commonly considered for abandon ship bags, ditch kits for oversea ferry flights of aircraft, etc.

If the OP is contemplating designing a many-thousand-dollar piece of equipment, then spending $240 would be small potatoes for playing around with the concept an a small scale. He will find that the amount of water collected is quite small.

It may have been used by the armed forces for over 40 years but that is an entirely different en vironment than floating in water. The waterborne unit must float, it is not staked into the ground with unlimited area usually available

You seem confused re how these work. They are not uncommon in abandon ship bags, and one was carried by a friend who sailed around the world on a Norsea 27. They float. You do not stake them down.

K Fry

With all due respects to your submissions and the OP's it appears from your most recent posting ,#41, that you do not agree with me that the OP's questions is not feasible as illustrated. I replied to #35 because your suggestion about solar stills appeared to be not following the original posting concerning the use of PV cells, floats, incline condensation surface, etc.

Yes, solar stills have been made and are currently used for mostly emergency purposes. They have very little output as compared to their in use size. They are not constructed as the proposed system was described. I also utilized the OP's statement that "The whole platform may be rowed slowly to new areas as to capture fresh abundant water". The production of the solar, the one you referenced has a max capacity of 4 pints per day did not seem to meet the reference to "fresh abundant water". To me, as a sail boater, 4 pints is not "abundant". The reasons I stated that the original proposed system was not feasible are the same, it can't support its own weight (displacement). If you disagree that is your right and that is a healthy use of this forum. It is not logical to compare an answer and a clarification of that answer with other than the original concept presented. Floating plastic sealed solar stills are not the same as the system referenced with its PV arrays, pumps, cooling water, inclined surface floats, etc. The solar stills are fine for their intended use but that is not what was shown in the posting.

My statement that "waterborne unit must float, it is not staked into ground with unlimited area usually available" seems to be misunderstood. Solar stills have been used by ground units in the military and they are staked to the ground so that they will not blow away and land surface is not usually a problem to be contended with. Waterborne units by their basic nature must float. The original system is very lacking in buoyancy therefore any size larger than a small model under ideal conditions will sink based on the weight of its components.

Also, I am not confused as to the operation of a solar still and how it works. If I was I certainly would not have replied. I have seen, handled, used and tested them under various condition. Their biggest problem is that the "4 pints per day" rating is under ideal conditions. Take a cloudy day or cold water and they don't do the rated capacity. Prior to making my first Bermuda passage the crew, which included me, put one to the test. Only under ideal conditions does it work as rated. Yes, they are included in various emergency sets but only for emergency use. The OP's original diagram didn't seem to be for emergency use.

Your statement "You seem confused re how these work" I can't discern what would prompt that. I also carried them when afloat, always! They are bulky when in use, easily tear, create a large sail area, make it harder to control and steer the boat or life raft since they act similar, not exactly, to a drogue anchor. I always prayed that I would never have to use one since they are of minimal advantage. I would prefer a torn sail rigged as a water collector to obtain my fresh rain water. That with a solar still would provide less than necessary water but any is better than none. With all respects considered, my statements about solar stills are based on personal use and familiarization. I also hope that your friend on a Norsea 27 has never had to use his. We sailors tend to hope for the best for each other!

Now, back to the original submission by the OP……………

Good Luck, Old Salt

Your statement "You seem confused re how these work" I can't discern what would prompt that.

It was this:

It may have been used by the armed forces for over 40 years but that is an entirely different environment than floating in water.

They float in water when used by the armed forces. You seemed to be saying the opposite.

According to a person who has served in Iraq and Afghanistan, they have been used in land areas and staked down. Don't know the intimate details but trust him enough to believe him. He also told me that many of his assignment were not public information due to the nature of them.

I have never known him to make false statements, has never given me any reason not to trust him, has the brains that would put both you and I to shame and is of the physical stature that I would never want to get him pis_ed off at me.

Otherwise, the pursuit of this minor difference of opinion is miniscule and tangential to the original question and illustration posted by the OP. I have made my postings based on scientific, engineered and practical information. I have no hands on experience with the exact question of the OP but do have a recognized amount of experience with theory, weights of components, buoyancy and several aspects of things that float on the water. I always try to consider the overall picture and not only one small fraction of it. With knowledge and experience I have determined, as many other posters have, that the proposed device would not be successful. Just because one device of a general theory works does not justify saying that all devices of that general theory will work. To paraphrase a portion of my postings 'if it is on water it has to float, if it is on land it doesn't have to float'. If you disagree with that and are looking for a perpetual difference of opinions based on conceived "lack of understanding" of the other poster please look elsewhere. I have neither the time or inclination to joust about this tangential distraction from the original posting and illustration. You are entitled to your views and I am entitled to mine. I know why I posted what I did, I don't know why you have made some of the statements you have. That is OK, this is America and our forefathers based this country on the right to disagree. But again, lets stick to the original posting and illustration. I still hope your friend has never and will never have to use the solar still.

Good Luck, Old Salt

The first thing that comes to my mind is an article I read about Perth Australia using wave powered pumps to send sewater for desalination.

I know that region has a sever need for fresh water (I think due to climate shift). I thought of this some time ago (but being stuck way too far away from water at the moment didn't develope it).

My thought was to use wave powered pumps to push the cold water over the top and if the water was heated enough by the sun, run it across a second sheet underneath the top. If the top were trasnparent, sunlight could heat a black second layer.

My thought was that it would not even need to be built on water. You could send the cold water across the tranparent chiller layer then through some solar hot water evacuated tubes then let the hot water flow across the black evaporation layer.

My father pointed out that that sea life is very agressive and organisms would try to grow inside any pipes or pumps installed.

Drew K

so yes its "possible", but since you neglected to state the amount of distilled water you expect to generate, or your budget for this white elephant I say the idea has little real life merit, in fact I think its nuts to consider.

If you were really serious, you would look into work done in the late 1960's (date??) by the Israelis in the area near the Dead Sea. I do believe they found that by making a saline gradient, the water temperature of shallow ponds rose to some very interestingly high temperatures. One could pipe a heat collector through the ponds, and use a vapor compression still to make abundant quantities of condensate water of quite low salinity even from sea water. If the temperature of the saline gradient pond is not enough for high production rate, then one could add some concentrating solar to "top off" the temperature, and if hot enough even produce net electrical energy and condensate.