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Should our desert communities make water from air?   The Consumer You: Marketplace

Started Jun-30 by Showtalk; 8279 views.
Showtalk
Host

From: Showtalk 

Jul-2

Solar is still very expensive to set up. 

In one of the Dune books, the Fremen were condensing water out of the atmosphere at night on the planet.

Showtalk
Host

From: Showtalk 

Jul-2

it could be a good plan in a very damp climate, which wouldn’t need the water anyway. 

Every air mass has a dew point. In a desert it may be near freezing, but essentially you refrigerate the air down until you chill it below the dew point, then you collect the water and finally use the hot freon in the refrigeration unit's condenser to re-warm the cold air and discharge the ultra dry air outdoors.

But if you are in a desert and near an ocean, you do what the Israelis do on an industrial scale. They have some pipes that go out into the Mediterranean for a ways. Sea water is pulled ashore in the pipes. They have a whole bunch of membrane units that they pump sea water up against at about 40 to 50 PSI of pressure.

The membranes are selectively permeable. Pure water is forced through between the molecular lattice of the membrane structure. The salt is unable to pass through, and you have more concentrated brine which then goes up a column to maintain hydrostatic pressure. The brine then goes into another pipe that is placed back in the ocean downstream a far as the currents are concerned, so the saltier brine is carried away.

The intake pipes have a progression of finer and finer mesh screens to keep fish and even plankton from getting into the system. It passes through some more fine filters before it reaches the membranes, and I think they expose the water to intense UV-C radiation to kill any microbes that remain that could colonize the membrane and have it for dinner.

On the other side of the membrane, they get thousands of gallons of water per minute, and on the ocean side, they circulate about 10x as much water, so the salinity doesn't go up enough to affect ocean circulation.

It's essentially one of the biggest reverse osmosis units that has been built in the world at the time. I think that some other Middle Eastern countries next to salt water have started building their own facilities - one in maybe Dubai or possibly Abu Dhabi might have a bigger one under construction by now.

WALTER784

From: WALTER784 

Jul-2

Showtalk said...

Solar is still very expensive to set up. 

Yes and no... I have 22 solar panels on top of my roof. 12 facing south, and 6 facing both east and west. Each panel creates 250W/hr. * 22 = 5.5KW/hr. They cost me $10,000 (incl. installation) about 8 years ago and I've sold back $7,115 of generated, but unused electricity to the electric company. My actual monthly electric bills are like $40 ~ $60/mo. for the times when the sun is not out (evening, midnight). Before installing them, my electricity bills were like $250 ~ $280/mo. So if you look at it in the long run... they are worth while. (Of course, not the cheap Chinese ones though.)

These are the panels when they were still boxed.

FWIW

Showtalk
Host

From: Showtalk 

Jul-3

Why haven’t we used the Israeli method?

Showtalk
Host

From: Showtalk 

Jul-3

It seems very costly here.

Bureaucratic inertia and the classic NIMBY syndrome, such as where a certain Massachusetts politician threw a conniption fit over proposed wind turbines offshore spoiling the view of him and his ultra-rich elites in their billion dollar mansions on the seashore.

And of course they jet around the world in their Gulfstreams to attend conferences on how to impoverish the rest of us and destroy jobs and all that stuff.

WALTER784

From: WALTER784 

Jul-4

Showtalk said...

It seems very costly here.

What is your average monthly electricity bill (including winter and summer months all averaged)?

Example: $500/mo x 12 months = $6,000/yr. That would be $12,000 for 2 years of electricity. Where as the solar panels were only $10,000 including installation cost. So it's like paying 2 years of electricity bills up front.

Is that really that expensive? Take it out as a home improvement loan!

FWIW

 

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