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> there wasn't a cost effective power solution for just desalination There absolutely is. All you need is a bunch of mirrors to direct the sun at a chamber fi
by abhibeckert 3y ago
> there wasn't a cost effective power solution for just desalination
There absolutely is.
All you need is a bunch of mirrors to direct the sun at a chamber filled with water. The water will evaporate, the expansion into steam creates significant pressure so you can run it through a turbine, and then once the steam cools down and liquifies again, it won't have any salt in it.
It's not even remotely expensive. Mirrors are cheap. The turbines/etc are basically the same as a coal or gas power plant and mirrors are a hell of a lot cheaper than mining coal or gas. Also if you're boiling a usable quantity of water you'll be generating a lot of power, which is a handy byproduct (more valuable than the water to be honest).
"Not in our back yard" is the real issue. The chamber is generally at the top of a tower, and even painted black all that sunlight focused onto it is very bright. People generally don't want a really bright object on top of a tower anywhere near them. I guess you could build a wall around it or something, but you'll still get complaints from aircraft/etc.
Driving into the sunset or sunrise is annoying. Imagine if that was all day every day instead of just for 20 minutes or so.
Having said that, if you're in a remote area to counter the NIMBY issue, and clean water is hard to find, then the system I've described is very effective and they are being used for cost competitive farming of cheap crops.
Anyone who actually wants to desalinate seawater can do it. It's just that almost nobody wants to right now.
- eropple 3y agoThis is really interesting; I of course know of salt retrieval via evaporation but I don't have a strong understanding of steam capture for pressure. How big a tower are we talking about for the steam volume necessary to turn a reasonably sized turbine?
- aaronbwebber 3y agoBig. https://en.wikipedia.org/wiki/Crescent_Dunes_Solar_Energy_Project https://en.wikipedia.org/wiki/Crescent_Dunes_Solar_Energy_Pr...
- bin_bash 3y agoisn't molten salt quite a bit different?
- thayne 3y agoAnd how much land do you need for the mirrors, to evoporate the water at a reasonable tate?
- toomuchtodo 3y agoHow are you handling the byproducts of the concentrated solar distillation process (ie remnants not evaporated in the focal point chamber, salt and anything else you’re not filtering out prior to steam production)? Does this solution assume a closed loop heat exchange system, where the primary loop feeds a steam generator (which is fed raw saltwater as feedstock)?
- DropInIn 3y agoBrine is the one word term to replace that sentence defining desalination byproduct... Why use so many words when there is literally a very old term well established in use?
- toomuchtodo 3y agoI didn’t think of the word while writing my comment. I should’ve! Thanks for correcting me.
- jethro_tell 3y agoI don't quite understand the rest for the turbine? Once it's steam can't you just cool it and then you have a distilled water source? I.e. steam through coils becomes water again.
- deleted 3y ago[deleted]
- pertymcpert 3y agoIt's more efficient to use mechanical filtration than to use distillation.
- ChuckMcM 3y agoA survey paper from 2019 on CSP Desalination techniques. https://drive.google.com/file/d/1kuDYo__EdM2-ew0SJ0RuZ_MdhOZVvfTI/ https://drive.google.com/file/d/1kuDYo__EdM2-ew0SJ0RuZ_MdhOZ... They have their own issues and they require quite a bit of real estate. Not something that was easily obtained in Sunnyvale but I'm sure that there are places where they would work.
- urinotherapist 3y agoEvaporation cannot create pressure needed to run turbine, while boiling will, but boiling will create highly corrosive steam with salt.
- dotancohen 3y ago> People generally don't want a really bright object on top of a tower anywhere near them. There is such a tower 50 km south of my house. We see it brightly even at this distance. There is a stretch of road near the tower that is uncomfortable to drive on during the day, the tower is so bright. I honestly can imagine that many a child has hurt themselves staring at it, it is extremely eye catching and there's really nothing else to look at in that desert. I'm all for green power (I have an electric car that I feed from roof-mounted solar) but these towers should be very far from population centers.