Comment by PaulHoule

Solar thermal as well as solar-chemical systems have the problem of start-up.

PVs do not have any problem starting up, they produce less than full power with less than full illumination but they produce something and once the illumination is full they produce full power immediately.

Many solar thermal power plants are fired with natural gas in the morning to get them spun up to the point where they can take advantage of the solar energy. Without that they'd probably lose a few hours of production.