Current approaches to water desalination are tremendously expensive and energy-intensive, so the search is very much on for new technologies that can get the job done more efficiently. Scientists in Melbourne have put forward one rather promising solution, developing a new kind of system that heats up and purifies water using only the power of the Sun.

It consists of a disc crafted from super-hydrophilic filter paper, a material that attracts water, which is coated with a layer of carbon nanotubes that convert sunlight into heat. Water is fed into the center of the disc via a simple cotton thread, where the heat turns it into steam that builds up on the disc while pushing the salt to the edge.

“This device can produce six to eight liters (1.6 to 2.1 gal) of clean water per square meter (of surface area) per day,” Zhang tells New Atlas. “We are working to further improve the water production rate.”

https://youtu.be/OGZVhcQ33MQ

https://newatlas.com/solar-steam-generator-water-desalination/60726/

(let’s find an old envelope and scribble some numbers on the back)

So, a square kn array of these would produce 6-8 million litres per day. Or about 2.2-2.9 billion litres per year.
So a 100 billion litres per year plant would need an array of about 35-45 square km.

I guess it would be doable-ish.

party_pants said:

(let’s find an old envelope and scribble some numbers on the back)

So, a square kn array of these would produce 6-8 million litres per day. Or about 2.2-2.9 billion litres per year.
So a 100 billion litres per year plant would need an array of about 35-45 square km.

I guess it would be doable-ish.

Bad form to make definitive calculations on such a new discovery. Makes you wonder what a similar attitude would be on other inventions like aircraft, motorcars, etc.

party_pants said:

(let’s find an old envelope and scribble some numbers on the back)

So, a square kn array of these would produce 6-8 million litres per day. Or about 2.2-2.9 billion litres per year.
So a 100 billion litres per year plant would need an array of about 35-45 square km.

I guess it would be doable-ish.

At an enormous cost, that’s a lot of carbon nanotubes, but the cost will come down.

I haven’t read the link yet and I’ll look into the technical details later, my first concern is how steam builds up on the disk.

PermeateFree said:

Current approaches to water desalination are tremendously expensive and energy-intensive, so the search is very much on for new technologies that can get the job done more efficiently. Scientists in Melbourne have put forward one rather promising solution, developing a new kind of system that heats up and purifies water using only the power of the Sun.

It consists of a disc crafted from super-hydrophilic filter paper, a material that attracts water, which is coated with a layer of carbon nanotubes that convert sunlight into heat. Water is fed into the center of the disc via a simple cotton thread, where the heat turns it into steam that builds up on the disc while pushing the salt to the edge.

“This device can produce six to eight liters (1.6 to 2.1 gal) of clean water per square meter (of surface area) per day,” Zhang tells New Atlas. “We are working to further improve the water production rate.”

https://youtu.be/OGZVhcQ33MQ

https://newatlas.com/solar-steam-generator-water-desalination/60726/

> the crystallisation of salts on the surface of photothermal materials during steam generation leads to a gradual decline in the water evaporation rate.

Most of the time, that’s what you actually want. The salt that crystallises first on the surface is pure NaCl. So you remove that as table salt and throw the rest (dominated by MgCl₂) away as “bitterns”. By condensing the water given off, say on a plastic membrane, you get the purest water, too.

This looks promising as a way of mining chloride minerals for use in metal manufacture. Groundwater can contain a lot of metal salts that are in a much more concentrated form than in seawater. I’m particularly thinking of barium.