500 megawatts is a substantial power plant. They chose to build in the corner of Nevada, a sparsely populated area with a lot of sunshine, and went with solar thermal instead of photovoltaic. It's economically viable, but the industry seems to be moving towards photovoltaic panels which generate electricity directly instead of having the intermediate step of a turbine. The costs for the physical solar panels are still going down.
There remain two ways of looking at the fact that solar power stations do not generate power at night. Way one, it's a tragedy that compromises the value of the station. Way two, energy demand is lower at night anyway, so it's great to produce the most power in the hot afternoon when air conditioners are running all over California.
The Ivanpah station is rated around 390 megawatts, and that one should come on line around 1 year from now. This one is also solar thermal.