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Join Date: Jun 2013
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Seawater Desalinization

06/05/2013 1:05 AM

Could wave action pumps provide the water pressure needed for facilities to remove the salt content by reverse osmosis or other methods?

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#1

Re: seawater desalinization

06/05/2013 1:12 AM

In principle, yes; whether economical, uncertain.

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#2

Re: seawater desalinization

06/05/2013 3:12 AM

For seawater RO, only if they can generate somewhere north of 40bar. If they are pushing seawater through an evaporator, then rather less pressure is needed.

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#3

Re: Seawater Desalinization

06/05/2013 9:42 AM

If the newer technology of forward osmosis that utilizes a thermolytic draw solution (ammonium bicarbonate) can be advanced enough to make scale up worth it, this requires no extreme pressure, since osmotic pressure differential takes care of the driving force necessary to pull water from the seawater side to the product side (draw side). Then, solar energy can be used to provide the necessary heat to drive off the draw solution, leaving essentially pure water behind, and the draw solution is recycled to provide another loop through the system. The wave pumps are only needed to pump seawater up to the elevation of the system, and pump a suitable circulation rate across the membrane surfaces.

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#4

Re: Seawater Desalinization

06/05/2013 12:16 PM

I have often pondered the possibility of building a large enclosure that would capture water during high tide and harness the gravity to generate electricity as the tide reversed, which could be used for water purification....The tank mounted on spring action type device would amplify the effect of the water level variation....With turbine incoming and outgoing to and from enclosure, this would seem to be a reliable source of energy...In the regions where the tidal change reaches 50 ft, the only limiting factor is the size of the enclosure.... I haven't really sat down and worked out all the details...any thoughts?

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#5
In reply to #4

Re: Seawater Desalinization

06/05/2013 1:08 PM

Sounds doable. But, is desalination the highest and best use for such power?

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#6
In reply to #5

Re: Seawater Desalinization

06/05/2013 1:51 PM

No probably not, but it is on topic....

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#7
In reply to #5

Re: Seawater Desalinization

06/05/2013 4:55 PM

Tidal power and desalination really would only be a match where the intracoastal area is desert or at least mildly arid or highly populated, and the tides are extreme, with a considerable potential. Otherwise the users will be stuck with various low head devices which may not deliver what they cost.

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#8
In reply to #3

Re: Seawater Desalinization

06/05/2013 8:47 PM

I know this is getting off the original subject, but how is forward osmosis with solar better than solar distillation?

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#9
In reply to #8

Re: Seawater Desalinization

06/06/2013 5:33 PM

A tremendously smaller energy input required. Solar distillation may require total evaporation of the water using concentrated solar collectors, whereas with forward osmosis, any form of waste heat (from an industrial engine, or generating plant, or a high capacity air compressor, etc.) will have suitable waste heat, also one can utilize solar energy to achieve temperatures between 45 to 60 C rather easily in quite a few places.

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#10
In reply to #9

Re: Seawater Desalinization

06/06/2013 8:54 PM

OK. I thought I read your description carefully the first time, but I see now I misunderstood the process. Thanks for pointing that out.

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#11
In reply to #10

Re: Seawater Desalinization

06/10/2013 4:34 PM

I think the original research on forward osmosis as a means of desalination of seawater was done at Yale University.

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