I'm not an expert by any means, but your comment reminds me of various nature documentaries in which desert species in certain locales would collect dew in the morning before it evaporates. Conceivably at least in such places it suggests that there is ample moisture in the air, and indeed if nature can get it out of the air then likely we could too. Conceivably an array of metal funnels leading to a bottle or tank (underground or otherwise protected from evaporation) could naturally harvest the moisture in such areas, even without a special hydrogel.

> huge amounts of energy

Condensation doesn't require energy. The energy mentioned in the article seems to be releasing the water from the hydrogel, but in my off-the-top-of-the-head metal funnel example a sufficiently steep big metal funnel can collect the water without any mechanical energy at all.

> Any such scheme isn't reliable in any case, and especially unreliable when things are dry and you really need the water. It works best precisely when you don't need it.

Water is stored easily enough, as long as you keep a surplus on hand for dry spells I don't see the problem?

EDIT: I am curious why my post is being downvoted. This doesn't seem particularly controversial.