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mrguyorama • today at 8:55 PM • 1 reply • view on HN

In places with low ambient humidity, harvesting water from the air is an atrocious process. The physics have not changed since people came up with this idea the last time, and the time before that.

For reasons of thermodynamics, pulling water out of the air uses more energy than desalination, and that's before the fact that you have to have a large fan to move a large volume of air to get a few drops of water.

It is on the order of using 60X as much energy to dehumidify air if you are trying to produce bulk water, rather than just desalinating water through a method like reverse osmosis


Replies

RobGR • today at 9:55 PM

When these systems are designed for low ambient humidity areas, they use a desiccant based first stage, where desiccant wheel or loop captures water from the low humidity air, and then is heated in a chamber to "regenerate" it and drive off the water into a 100% humidity chamber where the condensation can happen.

The applications of condensate water sources typically aren't in areas where desalination is the competing technology -- usually the competition is piping water in from far away via a utility system.