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Old 12-09-2013, 08:49   #16
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Re: Cheap Alterantive for Watermaker?

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Originally Posted by barnakiel View Post
1) 99% may not be good enough for drinking water,
2) before the thing gets into production, the device will be only slightly cheaper than a membrane/pump based desalinator,
3) it may (?) use less energy though.

Let's wait & see.

b.
If you check the spec's on RO water makers, they are between 98 and 99% efficient. Even with that you have people on the internet that will tell you that you are going to die from drinking RO water because it's too pure. They are wrong of course but they'll tell you anyway.

The graphene membrane is not likely to yield much of an energy improvement though with such a thin membrane you could probably increase the surface area a lot. Most of the energy required in RO comes from having to generate the nearly 800 PSI pressure to overcome the osmotic pressure of sea water. That requirement won't be changed by the membrane. I can imagine that the membranes themselves could be physically smaller. This might mean that you need only a 20 inch tube instead of 2 40 inch tubes to get 40 GPH.

There used to be a saying in engineering that the first 95 percent was really cheap but when you absolutely needed 99% that last 4% was really going to cost you. These guys are at 25%, I can't wait to see what 99% will cost, because 95% just won't do.
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Old 12-09-2013, 17:33   #17
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Re: Cheap Alterantive for Watermaker?

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(...) The graphene membrane is not likely to yield much of an energy improvement (...)
I am aware of the graphene membrane BUT the new trick, as per OP, is not a graphene membrane(?) I think they say something about using some sort of electronic/electric field 'filter'?

Anyways, when they nail a more energy efficient watermaker, this will be one great news for the world, sailing, and otherwise.

Cheers,
b.
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Old 17-09-2013, 23:21   #18
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Re: Cheap Alterantive for Watermaker?

I read a bit about desalination a few months ago. Here's a good explanation of ion depletion process. . . http://http://www.rle.mit.edu/micron...salination.htm. You can actually buy the graphene at: https://graphene-supermarket.com/Gra...ide-Paper.html only $300 for a 4cm diam sheet. I suspect with all of the other high tech applications for graphene or nano tube technology, we may see cost effective filters before ion depletion works on a usable scale.
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Old 20-09-2013, 10:25   #19
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Re: Cheap Alterantive for Watermaker?

i look at the under sink RO system i have in my house, $200 from home depot, no electricity, works on city water pressure and makes about 10gal of great drinking water a day. but then again it doesnt have all the salt to deal with.
what ive been looking for, and kind of stunned it doesnt seem to exist, is a manual or hand cranked desalinator. something along the lines of the hydrolic coffee grinders they use on the AC34 boats only to move water. one reference i read said those things are putting out 2200psi but i dont know if thats true. or a small pedal powered unit. seems like you could get a half hour workout and make your days drinking water at the same time. something bigger than a ditch bag unit but not intended to take a shower. doesnt seem like it would be that difficult to piece together...
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Old 20-09-2013, 12:09   #20
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Re: Cheap Alterantive for Watermaker?

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i look at the under sink RO system i have in my house, $200 from home depot, no electricity, works on city water pressure and makes about 10gal of great drinking water a day. but then again it doesnt have all the salt to deal with.
what ive been looking for, and kind of stunned it doesnt seem to exist, is a manual or hand cranked desalinator. something along the lines of the hydrolic coffee grinders they use on the AC34 boats only to move water. one reference i read said those things are putting out 2200psi but i dont know if thats true. or a small pedal powered unit. seems like you could get a half hour workout and make your days drinking water at the same time. something bigger than a ditch bag unit but not intended to take a shower. doesnt seem like it would be that difficult to piece together...
Katadyn makes a hand powered deslainator. Doesn't make a lot of water, but it will keep a few people alive. If you have a hand or foot powered pump that puts out 2200 psi, all you need is a filter and a membrane to make your own water maker. You can buy a small hosung and membrane for about $500. All you needed on the brine outlet is a needle valve to control the pressure and perhaps a guage to meake sure you don't exceed the 1000 PSI working pressure of most housings and membranes. Maybe just a popoff valve adjusted to 800 psi would do the trick. You will of course want to make sure you get a small enough membrane that you can maintain the needed pressure and has a low enough flow rate requirement that your pump can meet it. If your flow ate is not high enough the water quality will deteriorate. Then again a pump on an AC boat might cost $50K, in which case you would be better off buying a regular water maker.
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Old 20-09-2013, 13:27   #21
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Re: Cheap Alterantive for Watermaker?

yeah katadyn seem to be for emergency desal, not intended for daily use. and the lever action is not very efficient. i would have thought with all the 2012 end of the world nonsense someone would be making a stationary bike desalinator. then again i walk around my gym and wonder why all these exercise bikes arent pumping electrons back to the grid, or keeping the lights on...

i tend to get fat on passages with all the carb comfort food and no real way to burn them off. and i dont have the extra amps to run a power survivor. plus, if youve got to earn your fresh water you wont tend to be wasting it so much.

and now im thinking of fiddling with and old stationary bike and the pump from my pressure washer. good way to kill the weekend...
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Old 20-09-2013, 14:52   #22
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Re: Cheap Alterantive for Watermaker?

Here in Australia the government is letting the Chinese buy up a lot of agricultural land and water rights. How dumb is that.
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Old 23-09-2013, 14:47   #23
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Re: Cheap alterantive for watermaker?

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Wasn't there a sci-fi movie based on that concept made some years back?
I read a sci-fi short story where Tugs towed Icebergs back to the cities and had to outrun evil conglomerates and pirates.
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Old 23-09-2013, 14:54   #24
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Re: Cheap Alterantive for Watermaker?

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Originally Posted by robwilk37 View Post
. . . what ive been looking for, and kind of stunned it doesnt seem to exist, is a manual or hand cranked desalinator. . . seems like you could get a half hour workout and make your days drinking water at the same time. something bigger than a ditch bag unit but not intended to take a shower. doesnt seem like it would be that difficult to piece together...
There was WATERLOG made in UK, but I think they went out of business. Too many comments about drag and jokes about trolling for sharks. . . You could look at that design, probably bring the tube on deck, and use some mechanical means of turning the pump. Although I think I calculated one would need to pedal for an hour to get 1 gal
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