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Old 19-02-2010, 17:28   #121
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The energy released or consumed in the adding or removal of salt from fresh water is 750 watt-hours per cubic meter. So with a perfect system you will need .25 amp-hour per gallon at the very least. A Spectra runs about 1 amp hour per gallon...not bad.

Adding brine to fresh water releases this heat. Try it.
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Old 19-02-2010, 18:19   #122
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Hell Guys & Gals,

some very scientific posts in here
very interesting (if you happen to own a battleship or similar)
where safety, space, energy and aesthetics did not matter

BUT why not just drink beer, ?
let your body be the "tank & tube"

Collect the waste product
and repeat the process ad nauseum

you can carry on recircling the same water
all the way across the "ponds"

even more motivation when you find out
exactly what fish DO in the water anyway,

To further motivate you
I vaguely remember reading a recent article that said
that someone (*) had calculated the every drop of water on this planet
has passed throught the human system some obscene number of times already
(*) (obviously another person without a boat to keep them busy)

So basically you are not even thinking or acting "outside the box"
just cutting out the middlemen,
but at least in this case you will know who the last "user" was

and you would have an "audit trail" back to a reliable source
like Becks, Fosters, Carlsberg, Heineken or similar

Cheers .... I'm off to charge up MY own watermaker !

John
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Old 19-02-2010, 18:23   #123
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Cheers indeed! One of my important uses for the precious fresh water is a rinse after the saltwater shower. Can I use beer for this? If so, do I rinse with it or just drink it so I don't care about the salty itch?
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Old 19-02-2010, 18:57   #124
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Good point and one side effect I missed
drink enough and you simply don't care anyway ....
might fit in with the law of "diminishing returns ?"
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Old 19-02-2010, 19:33   #125
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Cheers indeed! One of my important uses for the precious fresh water is a rinse after the saltwater shower. Can I use beer for this? If so, do I rinse with it or just drink it so I don't care about the salty itch?
Drink then rinse, after enough beer it will start making sense anyway. What is that line Hakuna Matata or something. The circle of life.
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Old 19-02-2010, 21:48   #126
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The bell is presumably empty at the surface and at atmospheric pressure. It will take a significant amount of ballast to sink it. That ballast must be lifted back to the surface after the bell is filled with fresh water. Very heavy. Compute the energy. I bet it's similar to that of a watermaker pump.
It may very well be. But not because of conservation of energy. lesee (slow night at the lab...)

500 meters depth, 1m^3 of water weighs 1000kg, g~10m/s^2 => ~5megajoules

5mJ~1.4kWh

So 1.4kWh produces about 1k liter of water in the diving bell.

What does a watermaker draw?

I think it's something like 1 Amp*h/gallon, -> 12W*h/gallon (@12V) so 3.78liter/gallon -> ~45Wh/liter -> 45kWh/k liter

Looks like the diving bell wins... unless you want to haul it out of the water. I'm too lazy to calculate your likely freeboard and such. Just go get a straw.

Of course, if you're not in a hurry, you don't need to drop it to 500 meters.
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Old 19-02-2010, 21:51   #127
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To further motivate you
I vaguely remember reading a recent article that said
that someone (*) had calculated the every drop of water on this planet
has passed throught the human system some obscene number of times already
(*) (obviously another person without a boat to keep them busy)
I think the quote you are remembering is that in every glass of water, at least one molecule has passed through the bladder of Julius Caesar (or Oliver Cromwell, or whomever). This is because there are MANY more molecules of water in a glass than there are glasses of water in the world. Pretty kewl.
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Old 19-02-2010, 23:39   #128
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It may very well be. But not because of conservation of energy. lesee (slow night at the lab)

I think it's something like 1 Amp*h/gallon, -> 12W*h/gallon (@12V) so 3.78liter/gallon -> ~45Wh/liter -> 45kWh/k
:-) not do fast there Einstein. Sometimes in science it makes a difference whether one divides or multiplies. On this planet we would divide 12 by 4 to get the watt-hours per liter. So 3Wh per liter looks more like what I said. Plus figure your diving bell will slow considerably, then stop, as it becomes half full of water. Also consider how slow you'll be sailing with 500m of cable and a big iron sphere in the sea - compared to a watermaker in a locker. :-)
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Old 20-02-2010, 08:08   #129
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I think the quote you are remembering is that in every glass of water, at least one molecule has passed through the bladder of Julius Caesar (or Oliver Cromwell, or whomever). This is because there are MANY more molecules of water in a glass than there are glasses of water in the world. Pretty kewl.
Indeed.

According to Lewis Wolpert, as cited by Richard Dawkins, the laws of probability show that for every glass of water you drink, at least one molecule has passed through the bladder of Oliver Cromwell. There is nothing special about Cromwell, it’s just that "there are many more molecules in a glass of water than there are glasses of water in the sea".

“... Every time you drink a glass of water, you are probably imbibing at least one atom that passed through the bladder of Oliver Cromwell ...”

The God delusion ~ by Richard Dawkins
The God delusion - Google Books

See also ➥ Richard Dawkins Lecture Page 8
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Old 20-02-2010, 09:48   #130
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Just saw something on the discovery channel.
The desalination plant in Abu Dhabi uses 1.5 gallons of fuel (presumably diesel) for every 4.5 gallons of processed water.
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Old 20-02-2010, 09:54   #131
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Just saw something on the discovery channel.
The desalination plant in Abu Dhabi uses 1.5 gallons of fuel (presumably diesel) for every 4.5 gallons of processed water.
I bet somebody made a mistake. Dropped a few zeros. 1.5 gallons of diesel will easily desal hundreds of gallons.
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Old 20-02-2010, 10:06   #132
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Actually what they said was 1.5 million gallons of fuel to produce 4.5 million gallons of water.
They also showed that it was not RO but was via distillation.
For sure... it sounds like a lot of fuel.
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Old 20-02-2010, 10:10   #133
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Actually what they said was 1.5 million gallons of fuel to produce 4.5 million gallons of water.
They also showed that it was not RO but was via distillation.
For sure... it sounds like a lot of fuel.
Wow! It might be cheaper to simply FedX bottled water from Paris.
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Old 20-02-2010, 10:23   #134
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There you go
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Old 20-02-2010, 10:38   #135
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Just saw something on the discovery channel.
The desalination plant in Abu Dhabi uses 1.5 gallons of fuel (presumably diesel) for every 4.5 gallons of processed water.
The Shuweihat 2 power generation and seawater desalination plant, in Abu Dhabi, United Arab Emirates, is a natural gas-fired installation that will (scheduled completion Sept 2011) deliver 1,500 MW of electricity and 454,610 cu.m./day (100 million gal/day) of water.
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