At present, both efficiency and output of solar thermal power plants are quite low and it's a big reason behind the high cost of kWh electricity produced in present day solar thermal power plants. The other reason is the high cost of maintenance of array of reflectors. But, this cost can be reduced to less than 1/3rd of the present day level.
The way is using atmospheric or psychometric heat along with solar heat. The way is very very simple. Evaporate the water with the help of a vacuum pump in such a way so that the latent heat of vaporization of water comes from the atmospheric heat and then heating the vapor produced in this manner with solar heat. It can be easily calculated that in a steam at temp 300ºC produced in the same manner as that of present day thermal and solar thermal power plants; latent heat of vaporization of water is about 2/3rd of the heat consumed by water in this process. By vacuum evaporation of water, the latent heat of vaporization of water comes from the atmosphere and heating the vapor by array of solar reflector would need 1/3rd of heat necessary before. Therefore, with just 1/3rd of the amount of solar reflecting arrays, we can get same efficiency and output. And during the night too, less heat reserve will be necessary to run the power plant.