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FW From SW

03/31/2016 4:38 AM

Ref/Credit: IQ, for link to Adelaide city desal. plant.

100 GL/annum = 3171 liters/second.

Specific heat capacity of seawater = 3.985 kJ/kg/K

Lets say we heat incoming seawater from 30C to 80C(temperature optimum for vacuum distillation)

i.e.: from Q=mcdT = (1)(4.0)(50) = 200 kJ

That's 200 kw/kg of seawater heat energy input.

Yes, that's a lot of energy!!

The thing is, and under Australian continental sun, evacuated solar thermal collector tube can raise tube content temperature to about 120-130C !!

But, all we need is 80C.

i.e.: absolutely doable.

Plan

1. Pump cold seawater off the coast of South Australia from a depth of about 100 m or so(close to 0C!), and send this straight to.... 500 km away, up north.

(NPSH remains same as that at surface, i.e.: no added power needed for pumping from depth.)

2. That amount of cold incoming seawater would provide for an azz.conda amount of cooling power, into the distillate condenser !!

3. Pass the heated seawater(condenser outlet) into vacuum evaporation chamber, to boil off.

Concentrated brine can then be drained off and dried.

Use dried salt to make a 500 km long salt track.

i.e.: seawater from sea takes a one-way-ticket trip to desal. plant.

So, for 3171 litre or kg, just multiply 200 kw to it.

i.e.:3171 x 200 = 634 200 kw

Yep, that's a lotta power !!

All Free for the taking, courtesy of good 'ole Apollo.

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#1

Re: FW from SW

03/31/2016 6:28 AM

..except a kW is a rate of doing work, not an amount of energy. kWh is a unit of energy. There seems to be a lack of consistency in the units in the post. Please review.

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#5
In reply to #1

Re: FW from SW

04/01/2016 3:49 AM

Plan is to introduce concept and highlight energy quantum(J) needed to raise temperature of 1 kg of water by number of degrees C.

(mass of)1 liter fresh water = 1 kg, i.e.: energy input required would be the same.

Didn't think necessary to clutter post with repetitive numbers

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#8
In reply to #5

Re: FW from SW

04/01/2016 9:28 AM
  • The thermal capacity of water is well-known information that is in the public domain.
  • The original post is suffering from obliqueness that could turn it into a sales pitch. If selling a process, then venture capitalists are the correct people to approach. Good luck.

<unsubscribes>

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#2

Re: FW from SW

03/31/2016 7:06 AM

I don't understand the reason to go 500km inland!!! Adelaide city is on the coast, so you would need to send that water 500km back to there.

There is insufficient population that far inland to need that much drinking water,

Then to move the water that far has significant pipe friction losses to be overcome. Why build a 1000km pipe loop?

Also, Adelaide city has significant high temperature days with great solar impact. There is already a "solar salt farm" there that would use some of the brine rather than starting with normal sea water. NaCl is only one of the products that is harvested.

Then, while you talk of a one way trip for the salt, Australia's inland is notorious for overland flooding that would return the salt to the waterways, but not necessarily flush it to the oceans. Some areas inland from Adelaide are already struggling with soil salinity problems due to evaporation of irrigation waters. This proposal would only compound those concerns.

Could you please provide more detail of why you feel the need to move the process 500km inland?

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#6
In reply to #2

Re: FW from SW

04/01/2016 4:14 AM

500 km inland = as far inland as possible, where the sun is always crazy a.s hot !

i.e.: if that's available right outside city limits, that's mighty fine too.

Salt track?

I was just playing

Bonneville is an established site, and therefore 'stable'.

Way too many unknowns in Oz for that kinda experiment !

Besides, I could end up getting salted and dried like a road-kill raccoon for even proposing such a preposterous proposition !!

And as you rightly observed, leftover salt is big money, i.e.: why dump it ?!!

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#14
In reply to #2

Re: FW from SW

04/03/2016 6:17 PM

It's all pretty much a moot point now, as the SA government has decided that the 1.8 billion dollar plant is too expensive to run and has mothballed it.

All of the urban water supply desal plants that were constructed are either in long term hibernation or operating at a fraction of their capacity just to keep them going.

The Sydney plant has been a very expensive lemon with costs since 2012 being over half a billion dollars just to keep it off line.

Pretty much all because one of our university professors (of Paleontology?, not environmental science) famously claimed that Sydney's reservoirs would never again be at capacity. Two years later they were all overflowing, and have been almost continuously since then. Politicians made that same dill an Australian of the year.

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#3

Re: FW from SW

03/31/2016 7:09 AM

There are two principal routes to freshwater from seawater: evaporation and Reverse Osmosis [RO].

  • Of the two, RO is the most efficient, with consumption in the region of 3kWh per tonne being typical for the most modern plants fitted with pressure exchangers. There is a showcase installation in Larnaca, on Cyprus, which is published on the 'net.
  • Evaporation is nothing new and ships have been doing it for years, which is fine provided there is ample low-grade heat available. Solar fits the bill. So does the waste heat from a ship's power plant.

The need to obtain seawater from the deep ocean and transport it 500km to where it is needed is lost on this particular username.

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#7
In reply to #3

Re: FW from SW

04/01/2016 4:34 AM

PWS, your second bullet beautiful put to rest doubt expressed in the 1st one.

1. For the main part of the operation, i.e.; heating of incoming process fluid(seawater) in a vacuum distillation plant, needs no PV, whereas R.O system does , plenty of it !

2. My system can run 24/7, whether the sun shines or goes off to a beer break.

(R.O. system would need energy storage system to do this)

How?

Think LTTD.

And this is also where seawater feed, sourced from 100m (or lower) below sea level comes in on its own.

In fact, all that I need to do is pass the cold water through open air cooler and collect atmospheric condensate, even before passing it into distillate condenser !!

3. This system can produce electric power round the clock too - nope, no moving parts either, whilst PV based system would need to pack up at sundown.

How?

TEC generator.

4. Air conditioning.

5. And, most importantly, sir, - chill beer !!!!!

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#15
In reply to #7

Re: FW from SW

04/03/2016 9:39 PM

So..It appears that you are relying on atmospheric condensate for this project.

Consider that 500km north of the SA coast average relative humidity has fallen to below 10% by mid morning, just how do you expect to extract much moisture from this during the day.

Then you have the fact that annual mean overnight temperatures plummet to below 6┬░C with corresponding low humidity, little condensate to be gained there either.

Not much chance of 24/7 operation here.

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#16
In reply to #15

Re: FW from SW

04/04/2016 10:45 AM

There is a better low tech solution to collecting atmospheric condensate (given a wide swing in daily temperatures and at least some point during the day when the temperature is below the peak humidity water content dew point.

If one piles up a large cone structure (based on allowable stacking angle) of round stones (or man made concrete balls) of a suitable size (about bowling ball size, as I recall), having placed this stack over a plastic sheet (to collect the condensate), even including a drain point and piping system of tubing, there will some water collection but the quantity will not be enough for more than even one home.

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#17
In reply to #15

Re: FW from SW

04/08/2016 12:41 AM

I'll describe the system again;

1. Main process to extract fresh water from seawater - vacuum distillation.

2. Heat source to heat incoming seawater - solar, i.e.: evacuated tube.

Incoming seawater, at approx. 5 C;

1. Using this cold incoming stream to collect atmospheric condensate is Not the main process.

i.e.: since it's available, might as well use it !!

Next,

Ambient temperature.

Mean overnight temp., below 6 C ?

Isn't exactly representative, for SA, and for the whole year, is it?

Av. T/C for July is 15C !!

https://en.wikipedia.org/wiki/Climate_of_Australia

In addition, a few dozen feet below ground level, temperature is a constant 20+C.

Why can't this be used as heat source during night?

So, we now have;

1. solar

2. terra-firma heat

3. ambient heat

4. atmospheric water vapor.

All these and we still can't pull this off, based simply on 6C at some obscure location ?!!!

And I haven't even included TEG yet !

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#20
In reply to #17

Re: FW from SW

04/08/2016 8:41 AM

OK, your system will indeed make condensate, I have no idea how much, and that all depends on the many and varied heat exchanges used, and clever means of creating the vacuum. Why not shove as much heat underground as possible during the day, and use that thermal ballast to drive process during the dark hours?

Not only that, if the ocean is deep enough where you wish to dispose of any brine (if you don't do the salt mining somewhere inland), why not put it down a deep shaft with a turbine on it to recover that energy?

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#22
In reply to #20

Re: FW from SW

04/08/2016 9:46 AM

JS, yes sir, that too, is an alternative backup for heat storage, assuming such a backup system is even needed.

Brine discharge from vacuum evaporator would be fully dried out and stored, to be either shipped out to buyers or for further local processing.

Full dry-out could be done in vacuum chamber itself, but, that'd mean handling related complications. Hence, best to drain it off vacuum evaporator and deal with the drying-out elsewhere.

Deep shaft storage is definitely a neat idea.

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#11
In reply to #3

Re: FW from SW

04/01/2016 12:58 PM

FO (forward osmosis) beats RO hands down on energy/Kg! Especially on seawater where the net driving pressure on RO is very high indeed, and the only high quality energy input to FO is simply moving water along the surface of the membrane (more agitation and supply refreshing than any sort of net driving pressure). Waste or low grade heat finalizes the separation of the recovered water (on the high osmotic pressure side of the membrane from the seawater side) by decomposing at 45-60 C, then being recovered. The heated water may be cooled by air cooling or by exchange with seawater intake.

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#13
In reply to #11

Re: FW from SW

04/01/2016 4:33 PM

I wouldn't question or doubt FO's efficacy at all.

There're plenty of factors involved when it comes to choosing technologies, for it could be as vain as sponsors 'liking' FO.

However, I was looking at it from a seawater mining POV, i.e.: incoming seawater 'diluted' by removing Mg salts, before letting it into the rest of the system.

But....., that shouldn't be done at the expense on losing its precious cooling effect, for e.g.

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#4

Re: FW From SW

03/31/2016 11:42 AM

Maybe he's a build it and they will come sort of person....

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#9
In reply to #4

Re: FW From SW

04/01/2016 12:35 PM

...or more likely an April Fool...

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#10

Re: FW From SW

04/01/2016 12:52 PM

One of your statements is a bit off: 200 kJ/kg water to heat to 80 C is not 200 kW/kg, but it is the power rate if the flow were 1 Kg/s. IF you are doing the Adelaide City plant, then 100 Gl/annum = 3171 L/s and effectively 3170 Kg/s flow.

The power requirement according to your calculation would then become 200 KJ/Kg x 3170 Kg/s = 634 MW thermal. This is probably typical thermal input for 790,000 m2 at sea level and a W.A.G for solar influx at your latitude, but the sun only shines for an average of about 12 hours (less for overcast, haze, etc.) Suppose you double or triple the amount of land, that brings it to 2,370,000 m2, or roughly 2.37 Km2, or the size of a reasonable farm at 100% coverage. Allowing for access between solar collectors for any maintenance, one could easily reduce coverage to 50%, then the land requirement would be about 4.8 Km2 (reads square kilometer, not thousand square meter).

Are you saying you can get this kind of heating with a single tube pipeline traveling 500 Km? If the pipe line is 3200 L/s capable, it would indeed need to be large diameter, or a parallel network of smaller tubes equal in trans-impedance to flow.

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#12
In reply to #10

Re: FW From SW

04/01/2016 4:26 PM

200 kJ, true, I simply presumed readers know kw = kJ/s, since this would be a continuous-operation plant anyway...... assuming some local government take it up, that is

Sun only shines for 12 hours or so ?

Precisely where the beauty lies for this system - protagonist being cold seawater from 100 m deep(or deeper) !

I've also explained this in my reply to PWS above;

1. LTTD, hence 24/7 FW generation.

2. General cooling(substitute for power robbing air-cond system).

3. Condensate from atmosphere.

4. Electric power generation with help of TEC based system.

5. In addition, because of the big thermal difference possible, Organic Rankine Cycle(ORC) plants can be feasible too, consider this backup.

i.e.: 790 000 m^2 would be just nice for the primary intended purpose, no buffer needed.

I haven't peeked into pipeline sizing yet, but, obviously slow flow type arrangement would be best all round.

Multiple line setup has its own benefits too - system redundancy.

Fact is, such a setup could be put up just about anywhere.

Yeah, I's thinking NAME, but since those folks are currently busy with their extra-curricular activities, other Equatorial/Tropical belt locations would be good too.

Important point to note here is, the enormous amount of energy involved, and by extension, potential to save or slash petro based energy input.

It isn't exactly free, but it would certainly go light years ahead, in our effort to get off petro-energy.

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#18
In reply to #12

Re: FW From SW

04/08/2016 3:33 AM

"... the enormous amount of energy involved...", agreed. Perhaps you can tell us how much energy goes into your auxiliaries, in particular moving all that fluid around and maintaining a vacuum, especially since your choice of energy recovery/generation systems (LTTD, TEC, ORC) includes those with very poor cycle efficiencies, given the small temperature differences/low quality of the heat.

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#19
In reply to #18

Re: FW From SW

04/08/2016 6:43 AM

RAMC, numbers would need to be location specific, i.e.: 500 km north of Adelaide.

I need some time, please

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#21
In reply to #18

Re: FW From SW

04/08/2016 8:47 AM

Global Seawater Extraction Technologies, LLC already has everything in place to make this system work. They utilize solar brine ponds that get so hot you would be astonished, these are near boiling temperature of pure water. They also utilize a unique SCC (supercritical carbon dioxide) piston engine to produce hydraulic fluid pressure/flow to drive RO pumps, very clever indeed.

It takes far less energy to do it their way, sorry vacuum distillation but you lose.

TFO (thermolytic forward osmosis) even beats the crap out of RO (reverse osmosis) for the lowest energy requirements yet. It is time to wake up and smell some coffee. There is the potential here to have all sorts of valuable minerals being recovered from seawater, lots of fresh water for inland irrigation (if you can afford pumping it uphill), watering thirsty city dwellers, etc.

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#23
In reply to #21

Re: FW From SW

04/08/2016 9:58 AM

I'm totally with you on the continued effort towards 100% efficiency. However, setting up a non vacuum FW production plant isn't always "...how much kwh/liter water generated..."

Such a simplistic comparison would be no different from what Russia, China, India and a few other amigos using "number of tractors manufactured this month....." type economic health check parametric reference.

How relevant, reliable or even significant is that ?

I mean, take this efficiency thing far enough, you're gonna end up with a Heath Robinson/Rube Goldberg machine/plant !!

Unless of course, that's what you originally intended to achieve

Vacuum Distillation to generate FW is the grandmama of BDB(Big Dumb Booster) concept.

You can't fail.

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#24
In reply to #23

Re: FW From SW

04/08/2016 10:29 AM

Nothing I have mentioned has not already been tried, proven, and seen to be highly cost competitive on a massive scale. FO is the only so-called new technology, although this has been around for decades in treating mine tailings.

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#25
In reply to #24

Re: FW From SW

04/09/2016 11:44 AM

Which simply means that kwh/liter-efficiency is, but only one of numerous other factors that decides technology selection route for such projects !!

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#26

Re: FW From SW

04/10/2016 7:53 AM

Hello again Ramm.

I'd be interensted in knowing where you are from and why you believe that having freshwater available 500km inland from Adelaide is such a world important outcome.

It could be better argued to build a dam 1000km north of Adelaide and catch the wet season waters and move that 500km south is better. Such schemes have been evaluated and found unsuited.

Your discussion on using underground themal readings is flawed, since once the "cold" water has passed, then the soil temperature will be lowered locally around the pipe, negating the outcome you desire.

I also contest that pumping the concentrated brine underground is ABSOLUTELY unsuitable as a solution. The artesian aquifers through that region of Australia are already brackish, but suitable for stock purposes. To corrupt those with brine would be criminal.

I'm wondering whether there are cocerns more local to your home that might better deserve your focus.

Don't get me wrong, It's great to dream, but sometimes the dreams become obsessions that consume passions and resources and in the end coming to nought.

Also note that the water industry in Australia is already reviewing "on site" water recycling for business and households, so the water needs could reduce to as little as 25% of current usage once that is in place.

We have one example industry that was using 50kL per day and now are using less than 1kL per day from the water supply network, while factory throughput has increased around 25% with no reduction in quality or throughput.

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