Solar-powered desalination system requires no extra batteries
news.mit.edu
news.mit.edu
The no batteries thing is basically irrelevant to the innovation, and in fact Genius Water already offers no battery RO systems, also with questionable benefit (as well as being difficult to work with).
I run a solar and water focused EPC in East Africa and will hopefully be working with these guys in the future when they're off the ground with a commercial system. The potential is extremely high, particularly if the maintenance overhead and operational complexity can come down in practice.
Without such a tank, they’d need to somehow power the thing at night, which means a big battery, just like RO.
Also, the article suggests the power input needs to be steady and they use a computer to run it at higher rates when the battery would be charging.
Assuming there is a small battery or power grid (as both systems require), you could oversize an RO system and then change its duty cycle to keep the batteries at (say) 80% to prevent the solar production from curtailing. Round-tripping electricity through our home battery loses about 20%.
So, the “advantage” boils down to two questions that the article doesn’t answer: (1) what are the relative energy efficiencies of this system (in theory) vs RO? If the new system is 20% worse, RO wins, regardless of this optimization (2) what is the relative equipment cost vs. max throughput? (Since both setups assume oversizing to get better solar utilization).
I’d also like to know if the new system requires plastic, since the RO membrane probably leaches all sorts of nasties into its output.
I do like the fact that they are focusing on brackish water. We have this problem even in the coastal US (in the form of water softener output), and I’m sure they could sell a premium alternative to RO as a way to get scaling advantages on the manufacturing of the equipment.
It uses Electrodialysis, which is a mass separation process in which electrically charged membranes and an electrical potential difference are used to separate ionic species from an aqueous solution and other uncharged components.
Reverse-osmosis is absurdly efficient compared to distillation: a single 1X1 meter square solar panel can potentially generate 200 liters of fresh water per day.
There is a commercial market for salt -- and for stuff like treating roads in the winter it doesn't have to be very clean.
Otherwise, disolve it into the local waste water stream and discharge it back into the ocean.
Either it's not as big of deal as people suggest, you are wildly underplaying it, or somewhere in between. I've never felt that the argument against being the cost to heat the water was a strong one since salt water pretty much means a coastline which tends to have steady wind and sun. The biggest hang up has typically been putting that brine back into the ocean.
- in the poorest places, they can't afford desal. - in non-poorest places, most water is delivered by unified piping systems due to cost and labor efficiency. Schlepping water in bottles and buckets is nuts, though I can see it turning into the next weird fad in exercise or robotics.
Not going to do that with reverse osmosis systems.
That said, with merely brackish input water, I'm wondering how many problems this really solves. Drinking water, sure, but you have to get rid of the concentrated brine at the end and it's still groundwater that can be overdrawn.
However, if v 2.0 can effectively desalinate ocean water, it would be huge for islands and coastal areas.
I imagine the paper has the actual parameters, so you can build upon their work.
Late 19th and early 20th century attempts at self-loading firearms were often ridiculous in their concepts; huge component counts, lots of tiny mechanisms, strange attempts at extracting recoil and gas energy, everything under the sun. The mechanisms engineers were crafting in literal garage workshops are stunning in their variety and staggering in their watch-like complexity. Some were genuine works of art.
Then the M1 Garand, the SVT-40, and afterwards the AK (under the economic pressures of WW2) demonstrated how much room there was to simplify and give various components double duties. Now, most modern automatic weapons derive from those designs, and the improvements since have been in the materials engineering: Stronger, lighter, thinner, and generally reducing the amount of steel to the minimum necessary.
Uh, that's just going to increase the rate of acquifer depletion.