Solar-powered system offers a route to inexpensive desalination
news.mit.edu
news.mit.edu
If true -- this could be utterly transformative for much of the world.
> We did not build a family scale prototype, such as 10 sq ft. It would be some efforts for us to scientifically test that scale one with existing testing setups, mostly due to the limiting size of our solar simulator. Our existing waterjet cannot handle that size as well. A tank to work with will be 100L at least for our testing.
1 square kilometer (0.4 sq miles) patch on top of a sea can sustain 1 million families' needs (~3 million people)!
For example, a person in the USA uses 4 tons of water per day! Yet under 0.05% of that is drunk.
„Highly efficient and salt rejecting solar evaporation via a wick-free confined water layer“, https://www.nature.com/articles/s41467-022-28457-8
Does the salty water drop to the bottom? or concentrate at the top? How do you extract the clean water?
The engineering question is how much water do you use? You could use a thick later, like a swimming pool. But that takes a lot of energy to heat up. You could use a thin layer, like an inch thick across a parking lot. This takes less heat energy, but a lot of energy to clear out the brine, and a lot of salt will build up that you will need to periodically need to clean out.
This thingie does the best of both worlds. It is a thin layer at the top. Thin is good, because it takes less energy to heat. The layer between them is insulated, so you don't lose heat energy to the pool of water below it. There are channels between them that transports water upwards and salt downward via convection.
The thin layer at the top heats and evaporates quickly. The salt is transported fairly rapidly past the insulated boundary and into the large pool below. The large pool supplies more water through the same boundary.
The large pool can be slowly mixed with the ocean.
I'm kinda blown away by this. What a shockingly ingeniously simple and effective mechanism. It's like when I learned that the guts of a normal coffee machine that makes coffee machines do coffee machine things is just a heater, a hose, and a one way ball valve, and literally nothing else.
I hope it works and I hope it scales. We could be done with California's drought problem in a decade.
Thank you, this makes it much more understandable. I was clearly missing the understanding of prior systems.
This innovation simply helps prevent the water where the evaporation is occurring from getting too salty over time.
* Dirty Water
* White Foam Stuff
* Heat Absorbing Layer
* Insulation
* Filter
* Brine Water
[0] https://pubs.rsc.org/en/content/articlelanding/2020/ee/c9ee0...
also the reservoir below will have to be significant enough that increasing the salinity below does not adversely change the buoyancy of the floating insulation with the convection holes enough to make the evaporation layer above too thin.
that is; in the closed system shown the insulation will float higher as the water is evaporated eventually self limiting
- Salt water is poured into a reservoir that is exposed to the sun.
- The salt water evaporates due to the heat from the sun.
- Leaving the salt behind (and most other impurities), the water vapor rises until it lands on the glass and condenses into water droplets.
- After enough builds up on the glass, gravity pulls the water droplets down the glass until they drop into a separate reservoir - not exposed to the sun. This water is desalinated and drinkable
It's efficient, cheap, slow, space consuming, simple and works well.
At the end of the day, that's the metric that matters.