Actually, there's a shortage of gearboxes for windmills. Once it breaks it's down for months waiting for parts. The Chinese had problems with ice as well. Moving parts require much more maintenance, and are far more prone to breakdown.

Also, what about transmission lines? You are aware that the biggest barrier is everyone saying "not in my back yard", or environmental concerns, right? In CA at least, to run transmission lines from the optimal areas (think Mojave Desert) from a thermal-solar facility would require changing federal law protect those areas. Not an easy thing to do.