[July 4th]

The questions are, how much energy will they waste constructing the materials for the tower, and how toxic will those materials be when they are removed and replaced?

[DestroyEraseImprove]

Water, sand, cement....there's enough sand in the desert to produce concrete.;) Nothing toxic in it and the materials(concrete, steel, glas) can be recycled.

[eno_]

It sounds plausible. The materials should mainly be low-tech. Much greater chance of working profitably than solar cells, for example. And it will never "silt up" like a dam. I kinda like it.