You an see an early version of one of these in Barstow, if that's what you're thinking of. There is a functional one in Spain as well (http://en.wikipedia.org/w

You an see an early version of one of these in Barstow, if that's what you're thinking of. There is a functional one in Spain as well (http://en.wikipedia.org/wiki/PS10_solar_power_tower http://en.wikipedia.org/wiki/PS10_solar_power_tower) Anyway you may be right that the tower concept isn't going to last long, but the troughs have been shown to last decades (see Victorville, California) and obviously they have the same issue of dust... so there must be a known solution for that engineering challenge.