https://en.wikipedia.org/wiki/Multistage_flash_distillation
It's surprising they didn't mention this in the article. (It is, of course, mentioned in the paper, because its authors are decent and honest people.)
> more than 1.5 gallons of fresh drinking water per hour
I don't understand. Are those imperial gallons, US gallons, US dry gallons, or Irish gallons, which are all different sizes? https://en.wikipedia.org/wiki/Gallon#Sizes_of_gallons How many hamburgers is that the same weight as? How many ngogns is that? Or maybe acre-feet, pony shots, or Olympic swimming pools? MIT should be ashamed of their News Office.
The abstract of the paper https://pubs.rsc.org/en/content/articlelanding/2020/ee/c9ee0... does give the result in modern units, and to a much higher precision:
> a production rate of 5.78 L m⁻² h⁻¹ under one-sun illumination
In Dercuano http://canonical.org/~kragen/dercuano I wrote a note about multistage distillation, which I didn't realize was already a known technique until later; see notes/recycling-distillation.html or p. 1776 in the PDF. The basic summary is that modern reverse-osmosis distillation plants require on the order of 7 kJ/ℓ to get freshwater from seawater (which works out to about 50 kJ of sunlight per liter with a cheap 16%-efficient solar panel) while multistage distillation requires a few hundred kJ/ℓ.
The number given by the paper abstract works out to 623 kJ/ℓ if we assume one sun is 1000 W/m² (a common figure for the solar constant at the surface). So if you use those square meters to run photovoltaic panels which you then use to drive a reverse-osmosis machine, you can get dozens of times as much fresh water from the same solar energy. But you need to build or buy a reverse-osmosis machine, and then you need to defoul it, so this device might be a good choice in some circumstances. (You might need to defoul the distillation apparatus as well, though.)