I don't think you can gather water on top of anything. This collects it underneath like a leaf. Also its meant for desert conditions really. In Azerbaijan you would get water collecting on a roof overnight but try that in Qom even, and you would need another miracle. We have the magic well so I guess a magic roof is not beyond the realms of Islamic reality and scientific logic.They could have just had the water that collected on the regular flat roofs or any other shape roof or yard or whatever drain into a collection reservoir. This doesn't seem too practical.
As far as keeping the roofs cool, their are much easier and cheaper ways of doing that, like reflective surface, using a layer of insulation or even solar panels.
I also wonder how well these bowls will stand up to high winds. The engineering to keep them in place will require reinforcements trough the entire structure down to the foundation.
Not to mention, they're ugly.
You wouldn't be able to collect any water from plaster or cement either. The structure would be metallic most likely an Aluminum alloy of sorts. They can even indent the surface with grooves to guide the water down to the base. It doesn't evaporate readily either because its shaded from direct sunlight. But the main thing is what material is used. The structure needs to have very good heat transfer rate to condense as much vapour as possible. Its the effect you get with glasses in hot weather, so as long as the lower surface is kept cooler than the ambient, any moisture in the air will condense on the surface. That's why the structure is hollow so the heat from the upper surface doesn't warm up the lower one and the heat generated by the water condensing is conducted away quickly. That is the trick that makes it work. And it makes it pretty light weight so there is no need for extra reinforcement for low rises I would have said.
Its also for public buildings really. Although yes if it was a little less in your face, I could've lived with it. Hey it would make a lovely beach umbrella for the roof-top pool if you get creative with it no!!
But seriously it does make sense on paper. Lets see if it works out in practice but not holding my breath either. I think if there are firms trying to innovate then that alone is huge. If you don't try you will never succeed. They might have to change it in some ways or get rid but the experience will generate better basis for the next try and so on.
Right, before I put you to sleep, I am coming down from my preaching thingamajig (can't remember what its called in Iran where the mullahs give their sermon from) and hand the talking stick over to you. That's quite enough talking about me and my take on things, lets talk about you. What do YOU think about my take then??