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Simple, solar-powered water desalination

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Re: Simple, solar-powered water desalination

#161

Post by pedantsamaritan »

lovemenot wrote: post #135
adamcharnock wrote: post #126

Earlier quoted context omitted.

I made a comment with regards to this a while ago [1]. I'll repeat it here as I think it is relevant: --- I’ve heard on the grapevine that facilities are now being designed which work at under 100% capacity in order to soak up excess/cheap power. I believe this is coming about because: 1) the high cost of power and presence of sporadically cheap power makes it economically viable, and 2) designing equipment with lowe…

It'd be a boon for renewables if energy consuming plant costs were less dominated by investment in equipment. Imagine doing shift planning at such a site though. Eight days from now, there's a 60% chance of wind in excess of 5m/s between 22.00 and 06.00. But labour costs would be 130% higher than 06.00 to 14.00 on that day. On that morning shift there's a 50% chance of clear skies ...

I would be sad to be the worker subject to that shift planning

Re: Simple, solar-powered water desalination

#163

Post by i_am_nomad »

forgotmypw wrote: post #159

Would this process also be useful for filtering polluted water? Several pollutants I have in mind are VOCs and fluorine compounds. Hopefully there is someone here that is qualified to answer this question.

Probably depends on the vapor pressureS of the VOCs; if less than water, then no.

Re: Simple, solar-powered water desalination

#164

Post by i_am_nomad »

jvanderbot wrote: post #114
quotha wrote: post #94

Earlier quoted context omitted.

So the salt is just going back into the ocean. How is that different from other systems, they end up dumping the salt somewhere.

There's no difference. Except that the processing and shipping of ions is passive / much easier. Contrasted with large permeable membrane plants that have to burn power to push all that brine out into the ocean.

But the processing and shipping isn’t the problem with desalination. The problem is that dumping bribe or salt into the ocean can kill local wildlife.

Re: Simple, solar-powered water desalination

#165

Post by kragen »

newnewpdro wrote: post #113
kragen wrote: post #53

Earlier quoted context omitted.

You don't need batteries to run a reverse osmosis desalinator from solar panels; you can run the desalinator when the sun is shining and store the water. I'm surprised boats are already moving to lithium. I wonder if it would be worthwhile to tow the batteries in a separate buoy behind the boat?

> I'm surprised boats are already moving to lithium. When the alternative is a bank of lead-acid batteries with effectively ~50% usable capacity and poor charge efficiency, at least for cruisers effectively living at sea off solar power, it's not surprising at all.

WTF! gnaritas's comment has been [dead]ed. This site is turning into a fucking shithole. Here's what he said:

"Lead-acid is still better, it's 1/10 the cost for equivalent usable amp-hours. Most boaters use deep cycle golf cart batteries, they're produced at such scale that they're cheap as hell. Lithium is a waste of money and dangerous to boot. They only make sense if you're extremely space limited, which most bigger boats aren't."

Edit: apparently enough people vouched for the comment, it's back from the dead. But this definitely should not be happening to people like gnaritas who have devoted so much time and effort to making HN better.

Re: Simple, solar-powered water desalination

#166

Post by WalterBright »

emmelaich wrote: post #160
WalterBright wrote: post #14

When I was in Boy Scouts loooong ago, there were instructions and diagrams for making solar stills out of a sheet of plastic, a cup, rocks and dirt.

Same. I wonder how well they worked; I've never seen one made. It surely would require fairly specific conditions to work well; a wet ground and low humidity.

Just get a large bowl or pail, put an inch of water, or plants, in the bottom. Put a cup in the center. Cover the top with clear plastic film. Weight the center of the plastic. Place it in sunlight.

After a while, condensation will form on the underside of the film, the drops will run downhill to the center, and drop off into the cup.

Voila! Distilled water.

Found it! https://en.wikipedia.org/wiki/Solar_still

Re: Simple, solar-powered water desalination

#167

Post by ebg13 »

MayeulC wrote: post #131
ebg13 wrote: post #54

Earlier quoted context omitted.

Indeed. If you do only the drinking water, 2L per person per day for 20 million people is only 10566000 gallons or 132 football fields.

And for those who wonder like I did, I counted around fifty of those on that page: https://www.nycgovparks.org/facilities/football

Ok, but if you use those then you don't have anywhere to play. I think more importantly, 132 football fields is about the same as the total floor area of the Pentagon.

Re: Simple, solar-powered water desalination

#168

Post by emmelaich »

WalterBright wrote: post #166
emmelaich wrote: post #160

Earlier quoted context omitted.

Same. I wonder how well they worked; I've never seen one made. It surely would require fairly specific conditions to work well; a wet ground and low humidity.

Just get a large bowl or pail, put an inch of water, or plants, in the bottom. Put a cup in the center. Cover the top with clear plastic film. Weight the center of the plastic. Place it in sunlight. After a while, condensation will form on the underside of the film, the drops will run downhill to the center, and drop off into the cup. Voila! Distilled water. Found it! https://en.wikipedia.org/wiki/Solar_still

Sure, I know the setup. Just never made it nor seen it made.

Re: Simple, solar-powered water desalination

#169

Post by numbsafari »

zamalek wrote: post #40
numbsafari wrote: post #32

Earlier quoted context omitted.

If I am reading [1] correctly, NYC needs approx. 1 billion gallons of water per day. So, they would need an array of 12,500 football fields to meet their needs. [1] https://data.cityofnewyork.us/Environment/Water-Consumption-...

> 1 billion gallons of water per day * How much of that water need be drinkable? * How much of that water can be salinated (e.g. for flushing)? * How much of that water can be partially desalinated (e.g. for showering)?

I like your line of thinking, except now you would need to introduce two independent clean water sources, label things appropriately, retrofit all existing plumbing, etc. also, the salt in the water would be corrosive and require totally different infrastructure.

In the end, I’m not sure if it wouldn’t just be easier to make sure that all the water is potable.

Re: Simple, solar-powered water desalination

#170

Post by catalogia »

logfromblammo wrote: post #75
jfengel wrote: post #39

Earlier quoted context omitted.

I guess it's not really surprising for American engineers. Food and drink are measured in Imperial units. Technical doodads are measured in metric. You don't really need them to be compatible in this case: even though it appears that you're talking about multiples of units of length, you don't really compare them. You're not going to do the calculation that this is "1.58 micrometers per second" or ".447 feet per day"…

Given the increasing popularity of 500 mL and 1 L units of bottled water, and the ubiquity of the 2 L HDPE beverage bottle, I think it would have been safe to measure the potable water output in liters. About the only things still sold by whole gallons any more are milk, water, iced tea, and lemonade, in the 1 gal jugs, or water in the 5-gal water-cooler jugs. I'm more confused by the efficiency numbers exceeding 100…

Containers marked in liters are very common in America, but every once in a while you'll run into some loud-mouthed boomer who starts feigning metric ignorance in a bizarre quasi-patriotic display, often while badmouthing the French. I believe that avoiding this nuisance is the primary reason why imperial volume units are still used at all.
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