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Simple, solar-powered water desalination

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Re: Simple, solar-powered water desalination

#181

Post by VBprogrammer »

pfdietz wrote: post #31
sacred_numbers wrote: post #26

Efficiency in desalination is measured by comparing the energy expenditure to the enthalpy of vaporization of water (basically the energy required to distill water by boiling it). The current state of the art reverse osmosis desalination plants use about 3.2 KWh of electricity per cubic meter of fresh water ( https://pdfs.semanticscholar.org/d4d7/821d585699719289dddd10... ). This technology uses about 173 KWh of sola…

One fascinating (well, to me) component of modern RO desalination systems is the rotary pressure exchanger. Such a simple device, but so important. It looks like something from the 19th century, but the base patent was issued in 1988. https://en.wikipedia.org/wiki/Pressure_exchanger

Thanks for pointing this out. I knew that recovering pressure from the outgoing brine was an important efficiency measure but I assumed it was done using a hydraulic motor coupled directly to a pump arrangement.

Re: Simple, solar-powered water desalination

#182

Post by nloladze »

sacred_numbers wrote: post #26

Efficiency in desalination is measured by comparing the energy expenditure to the enthalpy of vaporization of water (basically the energy required to distill water by boiling it). The current state of the art reverse osmosis desalination plants use about 3.2 KWh of electricity per cubic meter of fresh water ( https://pdfs.semanticscholar.org/d4d7/821d585699719289dddd10... ). This technology uses about 173 KWh of sola…

How much space would this thing take up for say, a remote oil rig?

Re: Simple, solar-powered water desalination

#183

Post by gonzo41 »

steamer25 wrote: post #61
pfdietz wrote: post #31

Earlier quoted context omitted.

One fascinating (well, to me) component of modern RO desalination systems is the rotary pressure exchanger. Such a simple device, but so important. It looks like something from the 19th century, but the base patent was issued in 1988. https://en.wikipedia.org/wiki/Pressure_exchanger

I found this video which seems to animate the concept nicely: https://www.youtube.com/watch?v=udffed4Pq3g

That is such an incredibly smart piece of design. A tip of the hat to whom ever thought it up.

Re: Simple, solar-powered water desalination

#184

Post by bufferoverflow »

gpm wrote: post #74
sacred_numbers wrote: post #26

Efficiency in desalination is measured by comparing the energy expenditure to the enthalpy of vaporization of water (basically the energy required to distill water by boiling it). The current state of the art reverse osmosis desalination plants use about 3.2 KWh of electricity per cubic meter of fresh water ( https://pdfs.semanticscholar.org/d4d7/821d585699719289dddd10... ). This technology uses about 173 KWh of sola…

Say solar panels cost $2 per watt, 6 liters/hour is about 20 watts of power, is about 40 dollars of solar panels. Plus whatever the reverse osmosis equipment costs. This system gets approximately 6 liters/hour/sq m... so it makes sense if we can manufacturer it for less than 40 dollars per square meter and space is cheap.

> Say solar panels cost $2 per watt

Not for a large desalination project. You will pay close to the spot price. Which is 30-45 cents.

Your biggest cost will be labor anyway. And the osmosis membrane, which needs to be regularly replaced, unlike the panels.

Re: Simple, solar-powered water desalination

#185

Post by jokoon »

I guess this an awesome tech for places where there is no clean water, as long as those places are close enough to the shore.

But again, I doubt that any investor will be interested, as they will probably not get good enough ROE with this.

This would probably get the attention of government of some poor countries, or maybe some humanitarian organizations, or even the military.

I would probably be confident that a small portable kit could be marketed to survivalists and it would sell extremely well.

Re: Simple, solar-powered water desalination

#186

Post by timonoko »

timonoko wrote: post #178
steamer25 wrote: post #61

Earlier quoted context omitted.

I found this video which seems to animate the concept nicely: https://www.youtube.com/watch?v=udffed4Pq3g

Bloody Hell I did not know that. I have parts of broken Katadyn PUR-06. I was thinking of rebuilding it from better materials. The pressure recovery is the worst part. I can totally fathom now a hand-held desalinator with only rotating parts running from solar or Li-On batteries.

PUR-06 lasts 300 days, not "indefinitely": https://youtu.be/dNjdgfGgPdE?t=208

Re: Simple, solar-powered water desalination

#187

Post by zo1 »

steamer25 wrote: post #61
pfdietz wrote: post #31

Earlier quoted context omitted.

One fascinating (well, to me) component of modern RO desalination systems is the rotary pressure exchanger. Such a simple device, but so important. It looks like something from the 19th century, but the base patent was issued in 1988. https://en.wikipedia.org/wiki/Pressure_exchanger

I found this video which seems to animate the concept nicely: https://www.youtube.com/watch?v=udffed4Pq3g

Awesome video. One of the better uses of Youtube, and what we should be striving for in terms of "online content".

Re: Simple, solar-powered water desalination

#188

Post by MayeulC »

taneq wrote: post #173
ebg13 wrote: post #167

Earlier quoted context omitted.

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.

Install the solar panels over the football fields as roofing.

If you can afford it, and/or land/actually mounting the panels is the most expensive part, I'd recommend to install photovoltaic panels instead, though, as they are more versatile.

And it would simplify plumbing a lot to put everything in the same place, vs pumping brine up many roofs, and water down again.

Re: Simple, solar-powered water desalination

#189

Post by idoubtit »

This is not only about efficiency. As noted in the article, it would reduce the pollution of highly concentrated brine rejected into the ocean.

See for instance this article of the Guardian about a region in Chile where the majority of drinkable water comes from a desalination plant built in 2003: "The salt they pump back in kills everything'" https://www.theguardian.com/cities/2020/jan/02/the-salt-they...

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