Engineers at MIT and in China are aiming to turn seawater into drinking water with a completely passive device that is inspired by the ocean, and powered by the sun.
In a paper appearing today in the journal Joule, the team outlines the design for a new solar desalination system that takes in saltwater and heats it with natural sunlight.
The researchers estimate that if the system is scaled up to the size of a small suitcase, it could produce about 4 to 6 liters of drinking water per hour and last several years before requiring replacement parts. At this scale and performance, the system could produce drinking water at a rate and price that is cheaper than tap water.
You’re assuming that all heat energy input leaves with the water once it vaporises, which is unnecessary and indeed undesirable.
If you use the incoming water to condense the output vapor, you can recover and reuse a lot of the heat energy, plus you get output water at a much more reasonable temperature.