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Comment by adriand | Hacker News Reader

This may be a stupid question, but if the device requires power in order to move air over the water-collecting surface, would it work without power if it were outside in a breeze? Or is there something about the air flow in terms of its characteristics or location in/on the device that requires a manufactured flow?

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I guess the airflow is to make it more efficient. In high humidities, you can easily collect 1 liter potable water with a 3m2 plastic sheet, a clean recipient, a hole in the ground and some sunlight, or just hot weather. It's an old survival trick. His apparatus is a kind of upgrade.

The plastic sheet process is different from the one in the article. In the case of the plastic sheet, you are baking the water out of the ground, not extracting it from ambient air. It seldom works well in practice, because you get a little condensation under the sheet, but it's not enough to run in rivulets into the jar, and when you DO get a few drops in the jar, the same process that is baking the water out of the dirt evaporates it from the jar. You end up shaking the plastic, lifting it up and licking it.... Works better in theory than in practice.

But imagine that, instead of a special water bottle, you have a poncho-sized sheet of coated plastic in the shape of a windsock with a coiled wire ring at the opening and a pouch at the end. If this could work like the beetle's wings and take water out of the ambient air, that would be interesting.

I spent some time learning from a respected survival expert who claimed the 'solar still' was not an efficient use of one's energy. I tried it out a couple of times anyway and proved to myself that he was right.

What did work fairly well was a transpiration bag [1]. It took a few bags to get a meaningful supply of water and one needs to be careful about the foliage used.

[1] http://www.youtube.com/watch?v=q2EBiA0Csts

To get water out of the air, it has to be condensed into liquid. Condensation requires a significant temperature difference, and the best way to get that is refrigerant. I'm surprised that he was able to do this using only a solar powered fan.

You could create condensation with only a light breeze, but it probably wouldn't yield a significant amount of water. I think the best case for these would be to attach them to balloons and put them high into the atmosphere (where it's much colder), so that they could produce even more water with the same amount of energy.

My read is that the coating doesn't need a manufactured flow (after all, the beetle that inspired it doesn't) put it's very possible they'll make a bottle with a surface that requires it, say, a conch shell.

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