EnviroMission is planning “world’s first large-scale solar thermal power station” which will generate a whopping 200MW. Their website has a useful animation about this type of tower works. It’s quite simple, low maintenance, and totally passive. All that’s needed is sun, a large tower with a turbine in it, and acres of transparent sheeting.
Another type of much more complicated solar towers, have been tested in Barstow. They use mirrors to reflect the sun to heat water, sometimes using “used molten salt, a combination of 60% NaNO3 and 40% KNO3, as an energy storage medium.”