> 1.5 gallons of fresh drinking water per hour for every square meter 7 litres per m^2 per hour.
American gallons are smaller than U.K. gallons, which is where I suspect you got the 7l (6.8) from
Simple, solar-powered water desalination (2020)
51–60 of 241 posts
Re: Simple, solar-powered water desalination (2020)
#52Would it be possible to re-green deserts with this technology? Does anyone know of any studies on using this technology to combat climate change?
Yishan Wong, of Reddit CEO infamy, has been working on this for a few years: https://www.terraformation.com/
Re: Simple, solar-powered water desalination (2020)
#53Would it be possible to re-green deserts with this technology? Does anyone know of any studies on using this technology to combat climate change?
Greening deserts is not a good solution for climate change. In fact it might worsen climate change due to albedo changes.
A nice video about this:
https://www.youtube.com/watch?v=lfo8XHGFAIQ
Re: Simple, solar-powered water desalination (2020)
#54For 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%.
It quantifies the heat re-used between stages. In the supplement, they note 600% is the maximum. The derivation is at the bottom of p834 from the journal pdf. It's basically vapor produced at the measured average temperature divided by energy input.
If 600% is the maximum, then what does this mean?
> Theoretically, with more desalination stages and further optimization, such systems could reach overall efficiency levels as high as 700 or 800 percent, Zhang says.
Re: Simple, solar-powered water desalination (2020)
#55Earlier quoted context omitted.
Reading the article might help: > Unlike some desalination systems, there is no accumulation of salt or concentrated brines to be disposed of. In a free-floating configuration, any salt that accumulates during the day would simply be carried back out at night through the wicking material and back into the seawater, according to the researchers.
Yes. So it is not an issue for the device. However, the salt does end up back in the ocean where at scale the salt levels will be higher leading to the (edit: local) environmental issues mentioned by the GP.
Is the water cycle not a thing any more?
Re: Simple, solar-powered water desalination (2020)
#56"Tests on an MIT building rooftop showed that a simple proof-of-concept desalination device could produce..."
So doesn't look like they've even hooked it up to the sea yet, so still a bit to go for a real implementation, but still sounds interesting.
I harbour a small dream that I could buy some seaside land someday on a Greek island and hook one of these desalination devices up to the sea and build myself a small oasis.
Re: Simple, solar-powered water desalination (2020)
#57This is the winning sentence for me: Unlike some desalination systems, there is no accumulation of salt or concentrated brines to be disposed of.
Or is it?
> In a free-floating configuration, any salt that accumulates during the day would simply be carried back out at night through the wicking material and back into the seawater, according to the researchers.
This is fine for a small scale demonstration unit, but with bigger plants you will again run into the problem of over-salinating seawater, destroying the environment (and reducing your still's efficiency).
So once you get past a certain scale, you'll again need to redirect the wick into some waste brine tank and figure out logistics for disposing it.
Re: Simple, solar-powered water desalination (2020)
#58Earlier quoted context omitted.
Yes. So it is not an issue for the device. However, the salt does end up back in the ocean where at scale the salt levels will be higher leading to the (edit: local) environmental issues mentioned by the GP.
Is the water cycle not a thing any more?
Not an expert but I could imagine some local negative effects. Salt concentration may get higher in the area where the brine is returned. Depending on volume, currents, etc...
Re: Simple, solar-powered water desalination (2020)
#59For 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%.
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.
Re: Simple, solar-powered water desalination (2020)
#60Earlier quoted context omitted.
It quantifies the heat re-used between stages. In the supplement, they note 600% is the maximum. The derivation is at the bottom of p834 from the journal pdf. It's basically vapor produced at the measured average temperature divided by energy input.
If 600% is the maximum, then what does this mean? > Theoretically, with more desalination stages and further optimization, such systems could reach overall efficiency levels as high as 700 or 800 percent, Zhang says.
I think it tracks how well the materials they're using move heat between stages or lose it to the atmosphere. Their modelling (supplement figure 2, mentioned on page 4) depends on their specific construction. I wonder what it would do with gold as the plate material and aerogel everywhere else...