Chemists Work to Desalt the Ocean for Drinking Water, One Nanoliter at a Time

Original paper: doi: 10.1002/anie.201302577

From their paper it is mentioned they have a 40 nanolitre/min flow rate (25% desalination rate, 99% is considered safe to drink water).

They use an electric pole to generate an ion depletion zone, their problem right now lies in the severely limited flow rate and desalination rate. From my understanding the 25% desalination rate does not compound linearly and decreases in efficiency as the concentration of salt ions decreases.

Additionally their flow rate is 0.4 microlitres per minute, this would equate to needing 625 000 channels for one pass only to get 250mL / min. Scaling for microfluidics isn't simply using a larger pipe size, microfluidic devices largely operate with minimal forces and a Reynolds number of 1, that doesn't hold as you get larger.

The other big problem here is that this requires pressure driven flow, to do that they made two reservoirs of uneven height on opposite ends to drive flow. Again this is very electrically cheap (picowatts) when dealing with such small and perfect flow conditions.

The biggest problems they need to address are the low filtration rate and the low flow rate, it does not seem like there is a simple answer to the first, they do state that they are conducting a larger scale experiment that they will publish later.

I largely suspect that the larger scale experiment will fail in efficiency as another group (doi:10.1038/nnano.2010.34) who also uses a ion depletion zone (albeit by a different mechanism) found after publishing that they were orders of magnitude (10^3) too low in their predictions.

If anything this will perhaps be better than small, portable RO setups but not replace large factories which are actually pretty efficient.

its not only make ocean water drinkable, but also make ocean be livable, especially those tropic oceans, they would build solar powered water tower and soilless vegetable/food factories, war might break out between some countries for the ocean

  The process doesn't even have to be super efficient

Economics are important. We didn't go back to the moon because it was too expensive, and we're not going to see massive-scale desalination because it's also too expensive: http://physics.ucsd.edu/do-the-math/2012/10/the-energy-water...

  California uses 46 billion gallons of water per day. 
  Supplying 25% of this via desalination would require 36 GW of 
  thermal-equivalent power. California runs on 30 GW of 
  electricity, and a total energy budget of 262 GW (thermal; 
  from oil, gas, coal, hydro, nuclear, etc.—according to the 
  EIA). That’s a substantial amount for 25% of our water needs.

A "ten dollar glass of water" isn't even the big issue. Agriculture requires water, and expensive water means expensive food. Expensive food means people die, mostly from bullet wounds inflicted by people who are hungry. (I hardly need to provide citations for the number of wars resulting from food shortages)

I had an electrical engineering old timer explain the misconception as the Current Push Theory. (His industrial war stories were pretty good.)

"consumes less energy and is dramatically simpler than conventional techniques."

I remember a video that shows some kind of filter (it looked like a plastic sheet). They were simply pushing water against it and you get clean water from salty water.

I don't think it gets easier than that. However if I remember correctly the filter gets unusable after a while