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New Distillation type Watermaker, 'Slingshot'

Discussion in 'Watermakers' started by brian eiland, Jul 23, 2014.

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  1. brian eiland

    brian eiland Senior Member

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    I'm reading thru the June issue of Popular Science which contains a number of interesting short articles on the potable WATER shortages that exist in various parts of the world, and even those situations that are looming right here in the USA.

    One particular article that caught my attention, and that I though might have boating implications, was one about Dean Kamen's new distillation type watermaker, 'Slingshot'. Remember Dean Kamen?....he is that inventor of numerous medical devices, and the Segway transportation machines, etc. While working on a new peritoneal dialysis machine project, he found he needed a large supply of 'pure water' even above the relatively good quality we get from many of our city tap waters in the USA.

    Where does one find that quality and quantity of pure water at a reasonable cost? The 'distillation process' can get you that pure water even when the source might be sewage water, or chemical waste water, or seawater! But the process of distillation might need to be rather large scale, and it is normally expensive energy-wise. Kamen and his engineer's went to work on the problem, and what they have come up with they have chosen to call 'Slingshot', a vapor compression distillation machine.

    The energy efficiencies for this watermaker look very good, likely exceeding that of most other methods including the reverse-osmosis ones we often utilize on vessels. BUT, still it requires a 'jump start' to initiate the evaporation stage, and a minimum amount of additional energy input to keep it running. As a result of their desire to get some of these watermaking machines into remote and impoverished areas of the world were energy input is not so readily available, they have developed machines that can run on solar power, and one of Dean's pet projects, the Sterling engine.

    Of course our boats should have no problems with supplying these watermaking machines with enough power, either solar, or battery, or generator sourced. The point is we should be able to get a very high quality of water on board at a very reasonable expenditure of energy, and a very low demand of maintenance.

    Pure Genius: How Dean Kamen's Invention Could Bring Clean Water To Millions | Popular Science
  2. Marmot

    Marmot Senior Member

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    Not much new under the Sun or underwater.

    Fleet submarines in WW2 and through the 1960s used a Badger vapor compression still to produce potable and battery water. Badger stills were first patented in 1936 and were perfect for submarines because they used far less power than other low pressure evaporators and because they were DC powered, could be used when submerged.

    The were hot and miserable to manage, the sound of the roots compressor was obnoxious. They were used most often in tropical waters where battery water consumption was highest. The heat they radiated into the engine room along with the heat coming off the main engines after submerging made life very uncomfortable.

    Maybe Kamen fine tuned the process and repackaged it to look more like an Apple product but it is far from an original stroke of genius except perhaps for the marketing aspect of an old and well proven technique.

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  3. Marmot

    Marmot Senior Member

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    It doesn't take much of a review of the literature to show that the lowest energy desalination technique available today is reverse osmosis. If purification of surface water or other sources of fresh or brackish water is the objective, then the energy costs of RO are even less.

    Vapor compression consumes the least energy per unit of distillate produced compared to other evaporative techniques but it still consumes at least twice as much as RO.

    Call me skeptical but it looks like Kamen and Coke have interests other than providing the most water for the least energy and cost. If those were the objectives, a hand pumped RO would be the solution for family scale production of potable water from any source.

    That iWater thing looks cool and will probably generate a lot of government funding and good press for Coca Cola but I really question the claims of efficiency and utility for the application they are promoting. What are the savings and benefits to those who are expected to use it and support it? What is the real cost of each liter produced?

    As an alternative, consider the fact that native villagers are quite happy to spend the day operating a foot powered water wheel to move water from a ditch to a field. The same technique could easily power an RO pump to produce potable water from the same source.

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  4. chesapeake46

    chesapeake46 Senior Member

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    :confused:
    It beats contaminated water but "quite Happy " ?
  5. Marmot

    Marmot Senior Member

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  6. Kafue

    Kafue Senior Member

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    Market in California as a weight loss machine and the dams would be full once again.
  7. brian eiland

    brian eiland Senior Member

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    First off Marmot, thanks for that posting...interesting history.

    I think you are correct, its not an all-new technology. I don't see where Kamen is seeking any patents on the basic technology.

    Likely there have been considerable improves in compressor technologies and heat exchanger/transfer technologies since those days.

    Wonder what the Navy uses today?...RO or distillation?? ...not that they have any power restrictions aboard those nuclear boats. :)
  8. brian eiland

    brian eiland Senior Member

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    I must plead minimal knowledge on the subject of reverse-osmosis machinery, but I will attempt some observations.

    First off I find this quote from the article to be VERY interesting,...and from a number of documentaries I have seen over the years I believe it could be entirely true.
    This is a lofty goal.


    Can RO do these things?

    It's my understanding the RO units start to experience problems when dealing with VERY brackish water sources? And then the filter membranes need constant attention and/or often replacement??

    Is it also true that these filter membranes do not like to be left 'unused' for extended periods of time?...and that bacterias can begin to grow in under-utilized RO's

    I know of the existence of hand-held RO units, having asked about them one time for a survival package/liferaft. It would seem that such a peddled-powered unit would be applicable for third-world usage.


    If this were the case, then why did he pursue the 'distillation' theme? And particularly if he had in mind extending its usability to areas of the world were energy supplies were very limited, or often non-existent??

    Does not sound like a big power requirement?

    The expensive 'Stirling engine' aspect was not a necessary part of the watermaker, but rather an effort to extend it's application around the world....

  9. Capt J

    Capt J Senior Member

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    I think the Navy uses distillation and some of the waste heat from the Nuclear turbine to power the process.
  10. Marmot

    Marmot Senior Member

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    "Vapor compression consumes the least energy per unit of distillate produced compared to other evaporative techniques but it still consumes at least twice as much as RO."

    That was what got my attention ... only he can answer that one.

    http://www.desline.com/geneva/banat.pdf

    It takes X amount of power to change the phase of Y amount of water plus the power to compress vapor to Z temperature and pump the feed, distillate, and reject someplace so the only thing I can figure is it doesn't make much product water.

    Call me skeptical ... very skeptical.
  11. Marmot

    Marmot Senior Member

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    http://www.rexresearch.com/kamen/04159536.pdf


    That fact will improve the efficiency of the compressor above the old Roots blower but it cannot change the physics involved in converting liquid water to vapor then raising the temperature of that vapor.

    As water availability approaches crisis level in many parts of the world, some of the brightest minds have been involved in developing practical solutions. There are readily available reports and studies that compare the costs in cash and kW to produce potable water from different sources through different technologies. The numbers are consistent across every source but are not anywhere close to what is claimed by the authors of articles about Kamen's little marvel.

    Anyone who has even a passing familiarity with operating any type of desalinator or distiller will know that feed water treatment is critical to obtain acceptable performance for more than a day or so of continuous operation.

    I am amazed at the claims of operating for 5 years with no maintenance. The claims of needing no feed filtration or treatment are simply absurd. If the inlet pipe for that thing was stuck into a latrine as he claims possible I see it working for about 5 minutes before becoming clogged solid with material of the same composition as some of the claims.

    Even a low pressure evaporator will scale rapidly when fed with saline or other contaminated water. The pre-filters and storage for feed water treatment chemicals required to prevent scaling or fouling for 5 years without nearly constant attendance and would probably be about the size of 5 or 6 of the shipping containers shown in the photos.

    Doesn't anyone think it is odd that there are no peer reviewed analyses of the operation or even the thermodynamics of his claims? There are no specifications provided which might show if the claims for output are even close to reality? Where are the reports from those field trials?

    For a project that has had hardware around for 5 or 6 years and claims months of field trials there seems to be a thick cloud of smoke hiding the numbers that might support even part of the claims.

    I am surprised it isn't powered by Brownie's (yes, the diving folks) "Molecular Impact Energy" steam engine. That would put a cherry on top of the project.
  12. K1W1

    K1W1 Senior Member

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    Hi,
    The Brownies Boys might have been on the gas themselves and forgot the energy needed to get the water to the pressure claimed to enable it to boil so explosively
  13. brian eiland

    brian eiland Senior Member

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    Great research there Marmot, ...hope to find time to review it more thoroughly soon.

    Right now I have some automotive problems :mad: