# Emergency Water Desalination



## NeverSailed (Mar 8, 2010)

Hi there-
I'm on a team of junior level engineering students who, as a design project have been tasked with creating an emergency water desalinator. It is our understanding that very few smaller vessels carry any sort of device like this - largely because of cost. We have a conceptual design, however, none of us have any real experience sailing. From those willing, we would greatly appreciate some input.

Here's the basics:
1. Remove salt through evaporation instead of expensive RO filters or through FO filters that require a sugar-like solution.

2. Total weight 15-25lbs

3. _APPROX_ Dimensions of: 2.5ft*1ft*1ft

4.Production of 1-2 gallons/day should be very easy

5.Total cost to produce >30USD

6.We are attempting to make this work only requiring hand-power($$), but may require electrical input (similar to that of car battery) to achieve 1-2 gal/day. (Evaporating water is very energy intensive)

Are there any thoughts given that much? Anything you would or would not like to see in this type of device? Do you realistically seeing something like this being included in your emergency supplies? How many consecutive days would you want to be able to count on this device providing water?

Any thoughts that you have would be very much appreciated and seriously considered.

Thanks much,
David


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## hellosailor (Apr 11, 2006)

"1. Remove salt through evaporation"
There's nothing new about that. Survival training has taught how to use a piece of plastic for solar evaporative desalination for ages. Replicating something so well documented would be pointless, unless you can add something new to it.
And it is no trick doing this on a small boat--except of course when the sea is not calm. If your setup can work, say, on the roof of a car while four big guys are jumping up and down rocking it on the shocks, now you've got conditions similar to what might be found on a sailboat.


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## NeverSailed (Mar 8, 2010)

The advantage we see in creating a machine, is that it would produce a much larger quanitity of water than using just solar energy - especially if there's no sun. 
We are considering conditons in using this, we've wanted some insight on just how rough the sea is - particularly in a small boat.


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## sailingdog (Mar 19, 2006)

A solar still is not hard to create, and given sunlight in the tropics, quite effective. One way to improve on it is to use a Pelletier effect chiller to increase the rate of condensation.


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## tommays (Sep 9, 2008)

If you out to sea (offshore) and there is any kind of wind the big issue would be a unit that would hold up to the normal waves/wind that beat up most anything on deck 

Things get torn off sailboats all the time in bad weather


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## stolpsTDI (Mar 4, 2010)

Thoughts:

You're going to need quite a few BTU's in order to evaporate enough water to meet your goals. The first thing I can think of is using some sort of hand operated heat pump in order to accomplish the energy transfer...

Sea Roughness? Standing up while below is like trying to stand up inside a pickup camper while driving down a washed out forest road that throws you side to side and just happens to take you over 8-10 foot high rolling hills at the same time. Not impossible, but not that easy at first either, and you better have something to hold on to.uke


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## COOL (Dec 1, 2009)

If you could develop a device capable of a 
gallon or two of fresh water a day, you would
definitely be on to something.
There are emergency hand pump
water makers that require a lot of hard labor
to yield a gallon of water. Solar stills require
a bit of manipulation to eek out a mere trickle of water.
I envision a device that could sit on deck and
passively, yet slowly, produce drinking water from 
sea water all day long. You might consider 
incorperating a solar powered fan to hasten 
evaporation. Two gallons a day sounds optimistic,
but I hope you prove it is not impossible.


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## RXBOT (Sep 7, 2007)

You should have 2 quarts per day per crew member as a minimum objective. I think some kind of piston pump (hand operated) and membrane is likely better than evaporation. If it's dark & stormy the hand pump should still be viable.


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## sailingdog (Mar 19, 2006)

Hand powered RO watermakers, like the Survivor 35/40e series are well known. They're also high-maintenance and expensive. 

Solar stills are low-maintenance, low cost, and low output.  Hell, you can make one from a big ziploc bag, a bowl and a piece of black plexiglass.

I think the OP is looking to design something between the two.


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## bubb2 (Nov 9, 2002)

NeverSailed said:


> Hi there-
> I'm on a team of junior level engineering students who, as a design project have been tasked with creating an emergency water desalinator. It is our understanding that very few smaller vessels carry any sort of device like this - largely because of cost. We have a conceptual design, however, none of us have any real experience sailing. From those willing, we would greatly appreciate some input.
> 
> Here's the basics:
> ...


I don't get it! One would think if you are going to need a emergency water desalinator you are going to need it in a life raft and not on board the vessel.

I can't see packing a car battery in my ditch bag. How would a person recharge it so you make more water? The 4 x 8 foot solar panel or the gen-set in the ditch bag.

The cost of 30 dollars? You can't buy the car battery for that. There is a reason that there are hand pump water makers on the market.

I don't see the need or the practicality of it.


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## NeverSailed (Mar 8, 2010)

1. bubb2 has brought up something that I failed to clarify in my description. The cost of $30 excludes the cost of any sort of battery (something like the small sterno heaters are a possibility as an energy source if we can provide them oxygen while keeping them safe from splashing water or creating a fire hazard) - there are lots of options there.

(Sterno heaters would limit the amount of water you could get depending on how many you're willing to carry)

2. RO filters seem to be very popular, but do most people have them on-board? The cost seems to be prohibitive.

3.We are very curious about the size and weight of device you'd be willing to accept into a life raft. 

Thanks


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## hellosailor (Apr 11, 2006)

In order to be effective, whatever your power source and still are, they will also need to be cheaper, stabler, and more compact than the equivalent in bottled water. $30 buys me 30 gallons of bottled water, you've got to beat the price and bulk, because you can't assume there is any other power source in working order on a small craft.


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## RXBOT (Sep 7, 2007)

Say you did not get any additional water on the raft. It is overcast and rough seas for the next 7 days. The device is on the raft at all times. What device will work?


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## COOL (Dec 1, 2009)

NeverSailed said:


> We are very curious about the size and weight of device you'd be willing to accept into a life raft.


For the most informative look at conditions in a
liferaft, including the use of solar stills, read
Steven Callahans book 'Adrift'.
Your device must not require a fuel source or
battery. It takes a lot of energy to evaporate
a gallon of water, you would need more fuel than 
you would yield water. It would be easier to just
carry an emergency water supply.
Your device must utilize, a limited supply of, 
human, wind,or solar power.


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## COOL (Dec 1, 2009)

RXBOT said:


> Say you did not get any additional water on the raft. It is overcast and rough seas for the next 7 days. The device is on the raft at all times. What device will work?


In that situation, your only option will be a hand pump
water maker. They can produce 1 gal/hr as long as your
muscles hold out.


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## erps (Aug 2, 2006)

> You're going to need quite a few BTU's in order to evaporate enough water to meet your goals.


Wonder if one could get the BTU's with some sort of inflatable parabolic sun reflector, sort of a solar stove? I saw a piece on the boobtube that showed folks cooking using a solar stove with bits of broken mirror arranged in a bowl that focused the sunlight under the frying pan.


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## bubb2 (Nov 9, 2002)

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http://www.winslowliferaft.com/downloads/raftspecs/16.pdf

Rafts come prepackaged with provisions including emergency water ration, and a Hand operated water maker.

I would never lite a can of Sterno in a life raft. Considering what they are made out of, It would be suicide.


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## erps (Aug 2, 2006)

Good point Bubb2. It would be best to work on a liferaft, but if there was something cheap and reliable that only worked on the primary boat, I'd still be interested.


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## sailingdog (Mar 19, 2006)

Fitting 30 gallons into your ditch bag or liferaft canister is going to be a *****, and make it really heavy. 30 gallons of water weighs 210 lbs or so... and not many people can heft a liferaft with an additional 200 lbs. of weight on it.



hellosailor said:


> In order to be effective, whatever your power source and still are, they will also need to be cheaper, stabler, and more compact than the equivalent in bottled water. $30 buys me 30 gallons of bottled water, you've got to beat the price and bulk, because you can't assume there is any other power source in working order on a small craft.


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## erps (Aug 2, 2006)

> Fitting 30 gallons into your ditch bag or liferaft canister is going to be a *****, and make it really heavy. 30 gallons of water weighs 210 lbs or so... and not many people can heft a liferaft with an additional 200 lbs. of weight on it.


Seems like you could pitch your jerry jugs of water overboard into the water attached to a line to your liferaft though. A person would be properly motivated too if it's time to breakout the liferaft.


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## stolpsTDI (Mar 4, 2010)

erps said:


> Wonder if one could get the BTU's with some sort of inflatable parabolic sun reflector, sort of a solar stove? I saw a piece on the boobtube that showed folks cooking using a solar stove with bits of broken mirror arranged in a bowl that focused the sunlight under the frying pan.


Google 'Cool Earth' to see inflatable solar reflectors, it's pretty neat.


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## COOL (Dec 1, 2009)

erps said:


> but if there was something cheap and reliable that only worked on the primary boat, I'd still be interested.


There is definitely a place for such a device on a cruising
boat, in every day non emergency living.
I can picture a small, simple, low maintenance device that 
you can set out on deck, that quietly produces one or two
gallons of clean drinking water every day.
I think the idea of combining a solar oven with a solar still,
and working in a solar powered computer fan, sounds like
it might make for a feasible prototype.


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## bubb2 (Nov 9, 2002)

I always liked this design.
Watercone® The Product


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## NeverSailed (Mar 8, 2010)

If there is a need for desalination capabilities on primary vessels, producing a device to meet that need would be much easier than on a life raft. It seems here that people feel there is that need.

If this is the case, what kind of electrical power would you readily devote to a device like this?


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## sailingdog (Mar 19, 2006)

Again, it depends on how much time you have to prep the liferaft. If it is a major holing, then you may only have seconds... if the device is small enough to stay in the ditch bag or better yet, stay in the packed life-raft, you wouldn't have to worry about it. Of course, some boats deal with holing better than others... mine would be difficult to sink by holing it, since it has three hulls, separated into ten separate compartments. 



erps said:


> Seems like you could pitch your jerry jugs of water overboard into the water attached to a line to your liferaft though. A person would be properly motivated too if it's time to breakout the liferaft.


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## erps (Aug 2, 2006)

NeverSailed said:


> If there is a need for desalination capabilities on primary vessels, producing a device to meet that need would be much easier than on a life raft. It seems here that people feel there is that need.
> 
> If this is the case, what kind of electrical power would you readily devote to a device like this?


If that's the route you're going to take (an electrical appliance) a lot of cruising boats have solar panels or wind generators already installed that put out 5 to 20 amps or more depending on how many panels they have up or how much wind they have to drive their generator.


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