Disclosed is a thermal energy storage system for storing collected solar thermal energy. The system comprises a solar thermal energy collection facility in the form of a field of parabolic troughs, which is in thermal communication with a molten salt circuit. The molten salt circuit is in fluid communication with a molten salt storage facility comprising at least three storage tanks that are each in fluid communication with the molten salt circuit. The multiple tanks set-up allows using cheaper materials, and a more efficient storage of thermal energy.