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Simple, solar-powered water desalination (2020)

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Re: Simple, solar-powered water desalination (2020)

#221

Post by ajb »

crackercrews wrote: post #3

For those curious what the 385% refers to > the team’s demonstration device can achieve an overall efficiency of 385 percent in converting the energy of sunlight into the energy of water evaporation. Honestly I still don't know what that means, or how efficiency can be over 100%.

Its disingenuous. We know what the theoretical best efficiency of desalination is, by thermodynamics. You can calculate it by assuming a completely ideal reverse osmosis setup. Compared with that, the efficiency would be less than 100%. This article takes 'efficiency' as compared to just evaporating the water and not reclaiming any energy on condensation.

Re: Simple, solar-powered water desalination (2020)

#223

Post by throwaway894345 »

SV_BubbleTime wrote: post #178
throwaway894345 wrote: post #162

Earlier quoted context omitted.

This makes sense to me. I wonder how feasible it would be to release the saltier water over a broader area to reduce the salinity in any one area? Also, there are at least some ecological benefits to increasing the amount of fresh water. An extreme example is the lake that appeared in the middle of a desert in the United Arab Emirates. I have no idea how we weigh one against another.

Now you’re paying for salt transportation again.

Not if you have many small desalination plants distributed over a larger area. This would work well for less-densely populated areas.

Re: Simple, solar-powered water desalination (2020)

#224

Post by throwaway894345 »

EricE wrote: post #183
kevstev wrote: post #166

Earlier quoted context omitted.

Why not just collect the salt, and sell it as... salt? Even if its not ok for cooking, it should be fine for roads? I am sure there are other industrial uses for salt.

Salt from roads is seriously contaminating our environment and significantly impacting farming in more and more areas. Ever hear of the Romans salting the earth of people the conquered? It was so they couldn't grow crops - yet we routinely do this to ourselves - pretty daft.

We also farm in a way that is almost optimized for erosion of topsoil. We’ve already lost a third of it and it only renews on geological timescales. Daft is too polite.

Re: Simple, solar-powered water desalination (2020)

#225

Post by SamBam »

Scoundreller wrote: post #220
SamBam wrote: post #196

Earlier quoted context omitted.

Can't wait for all our text input boxes on the web to be GPT-3-enabled, and then all comments on HN and Reddit and Twitter will be just people accepting the defaults, and it will end up just being GPT-3 talking to itself, and we can all go back to doing something productive.

Reminds me of a post here where it was some neural network chat/excuse generator. Just two people back and forthing about why they couldn’t meet up. I lost it when one of the excuses was, 3 weeks later “oh, I can’t meet for lunch on July 29th, I have to go to my mother’s funeral”

Amy way you can link to that conversation? I tried to find it on Google.

Re: Simple, solar-powered water desalination (2020)

#226

Post by okareaman »

mixmastamyk wrote: post #219
okareaman wrote: post #212

Earlier quoted context omitted.

I meant the salinity content per liter of the world's oceans would rise an insignificant amount, especially since fresh water flows back to the sea for the most part. If someone can tell me otherwise, I'm ready to be educated.

It takes a while to disperse. Meanwhile salinity in the region has gone up, say 2%. Apparently sea life is very sensitive to it. I agree there are a number of solutions though. Adding to treated sewage is a good one.

I grew up in a town with a gray water pipe to the ocean. When the environmentalist movement took hold, it was decided the pipe should be extended further into the ocean so as not to disturb the ecosystem. They got it done, so I know even a small town can do this.

Re: Simple, solar-powered water desalination (2020)

#227

Post by mrfusion »

SamBam wrote: post #196
adolph wrote: post #155

Earlier quoted context omitted.

Nothing to worry about. Its people alpha-testing the Copilot internet commenting plugin.

Can't wait for all our text input boxes on the web to be GPT-3-enabled, and then all comments on HN and Reddit and Twitter will be just people accepting the defaults, and it will end up just being GPT-3 talking to itself, and we can all go back to doing something productive.

Relevant xkcd: https://xkcd.com/810/

Re: Simple, solar-powered water desalination (2020)

#228

Post by ohgreatwtf »

These are all extremely cool approaches to the problem but unfortunately they are all high tech and most require a substantial amount of complex component fabrication to work.

I have been thinking about a passive, low cost system. It would use series of rows of shell-like structures with fresnel attributes and coatings that simultaneously cause water to condense on heated surfaces and then drain into subsequent rows of shells, a process that passively cycles with the heat of the sun. A large fraction of each row's output collects in a tank that is periodically raised to backflush the row and reduce the saline buildup.

Re: Simple, solar-powered water desalination (2020)

#229

Post by m463 »

kwhitefoot wrote: post #75
goodcanadian wrote: post #34

Earlier quoted context omitted.

Usually, numbers over 100% mean that you are putting in less energy than is needed for the process. In this case, that would mean putting in a little over a quarter of the needed energy. That does not imply free energy or anything. The rest of the energy has to come from the environment. A heat pump is another common example with efficiency numbers in the same ballpark. With a heat pump, the heat is being moved from…

Efficiency is still the wrong name. What you are describing is usually referred to a coefficient of performance , abbreviated to COP . See https://en.wikipedia.org/wiki/Coefficient_of_performance

I wonder if concentrating solar cells should have similar nomenclature.

Re: Simple, solar-powered water desalination (2020)

#230

Post by achn »

amelius wrote: post #128
TeMPOraL wrote: post #59

Earlier quoted context omitted.

Others already explained where the >100% efficiency comes from, but I want to point out that a good 1/4th of the article is repeatedly explaining how this works, over a couple of paragraphs.

Reading it in the comments was still more efficient than reading the article.

220% more efficient.
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