Water Desalination by Using the Sun - Will it Work ?

[mintyspilot]

Kristian

In principle I think it will work. I think enough people have done the basic experiments to show that it is possible. We now have to consider constraints such as is it practical on a rolling boat? What size is the appartus? What rate does it produce water at and how much water do you actually need?

I reckon that we will need to wait until the equinox on 21st March before the sun gets powerful enough at this latitude to heat water.

[Jolly Roger]

Hey! Don’t get me wrong chaps, I’m all for self sufficiency where it is reliable. Drinking water at sea has been a timeless problem, so long as man has ventured upon it, and if someone can come up with a practical means of making the stuff out of sea water, for no money, whacko! They tell me modern watermakers can make drinking water out of any quality of sea water, but would this apply with Kristian’s idea? Would you not have to filter the water first to get nasty little bits out of it? The question of reliability is very important as well, because anyone who rigged such a contraption would then perhaps think they don’t need the proverbial Jerry Cans, and may even be tempted to shower more often than once a fortnight. Then the sun goes in and they are snookered……I think I will stay with my time honoured backup, canned Guinness. It keeps well in the bilge, tastes better than water, you can cook with it, and it has the singular effect of soothing gales, often reducing an eight to a six in no time at all.

[s/v Jedi]

I think this thread is on the wrong track. Without checking numbers, I think that the sun evaporates enough water from the sea all around us already so why not skip the boiling step and try to catch the water vapor that's all around us already? When the wind is up, enormous quantities of water are flowing over our decks and we just let it go while running watermakers. I think my original suggestion for a wind-trap wasn't taken serious enough because of my Arrakis, and Nua'Dib story...

cheers,
Nick.

[Kristian]

Hi S/V Jedi!

I like your idea and sure I belive that there is enough water in the air to satisfy our every needs.

I just have to admit that I have not given the idea any serious thoughts.

From the top of my mind I can only see three ways of getting to that water and it is by lowering the temp in the air or lowering the pressure or finally a combination of the two first.

I have to think a lot more to even have a first go at how to do that but it sure could be interesting!!

Dear Jolly Roger,

I do sure agree on that reliability is a major issue when it comes to water and long trips across the ocean.
I guess that prudence dictates that you shoud back up your sources of potable water no matter what way you go.

That given I belive that the simpeler the system the smaller the chances of a failure.

Rgds

Kristian

[mintyspilot]

Nothing wrong with your idea Nick, but we had already invested mental capital in the solar boiler idea. One crisis at a time.....

[s/v Jedi]

;-) but the sun & sea is one big solar boiler ;-)

On condensing from the wind, my first idea: create pressure with wind trap, like funnel-shape into small diameter hose. Next an expansion valve to dramatically lower pressure followed by a condenser. Production can be 4 times lower than using the sun because it'll work 24 hours per day.

cheers,
Nick.

[mintyspilot]

How about this as a variation?

Have a black metal plate facing the sun over which you run salt water warming it up. It then "dribbles" down a grid facing into the prevailing wind. Being warm it will have more tendency to evaporate from the grid and saturate the incoming airflow. This could then be directed onto a cold metal plate to condense the vapour into water and thence into a run-off channel.

I suspect that the warmer the salt water is, the more efficient this process would be.

[anjou]

Originally Posted by s/v Jedi

I think this thread is on the wrong track. Without checking numbers, I think that the sun evaporates enough water from the sea all around us already so why not skip the boiling step and try to catch the water vapor that's all around us already? When the wind is up, enormous quantities of water are flowing over our decks and we just let it go while running watermakers. I think my original suggestion for a wind-trap wasn't taken serious enough because of my Arrakis, and Nua'Dib story...

cheers,
Nick.

Nick
There is already a condensation machine for doing this but its so power hungry. Bad enough if your plugged in to the grid but not going to work on the hook.

[anjou]

Originally Posted by s/v Jedi

;-) but the sun & sea is one big solar boiler ;-)

On condensing from the wind, my first idea: create pressure with wind trap, like funnel-shape into small diameter hose. Next an expansion valve to dramatically lower pressure followed by a condenser. Production can be 4 times lower than using the sun because it'll work 24 hours per day.

cheers,
Nick.

Would a large aircraft type venturi create enough low pressure?
Trouble is, the wind has to be blowing.

[Jolly Roger]

Originally Posted by Kristian

Hi S/V Jedi!

Dear Jolly Roger,

I do sure agree on that reliability is a major issue when it comes to water and long trips across the ocean.
I guess that prudence dictates that you shoud back up your sources of potable water no matter what way you go.

That given I belive that the simpeler the system the smaller the chances of a failure.

Rgds

Kristian

That's why I suggested the canned Guinness - can't get anything simpler than that. The only problem I can envisage is showering. That could be really messy and very wastefull as well.

[rover88]

Place a tall cup in the center of a much larger pot. Surround the cup with wet seaweed and a half litre of sea water. Place and secure a sheet of plastic over the pot loose enough to weigh it with a small stone in the center. Leave in sunlight. Condensation will form on the plastic and drip down into the cup. It will yield a couple of mls of fresh water. Just enough to make you more thirsty.

[s/v Jedi]

For condenser, how about a Peltier element?

Yes, wind is needed but so many boats are in the tradewinds with enough of that!

cheers,
Nick.

[lorenzo b]

There is a book called Sailing The Farm written in the 70's that has plans for solar water makers that are really simple for use on small boats. The book is a real goof to read, truly a blast from the past.

[mintyspilot]

That is a great tip. Thanks. I shall be making a trip to the local library for that.

[Sam Plan B]

A few months ago I brought a Soleusair dehumidifier aboard. It runs on 120v shore power. It does a good job and keeps the condensate to a minimum. But it also produced about a gallon of water daily. I am wondering if the mechanics of dehumidification can be adapted to make even more water. What do you say?