Steam can be generated using insolation by a solar collection system. A thermal storage system can store enthalpy in insolation-generated steam at times and can generate steam from stored enthalpy at other times. During some operating periods, a gas-fired superheater can further heat the generated steam to provide superheated steam to generate electricity. Steam at a substantially uniform electricity generating temperature may be produced selectively and at different operating periods from insolation only, from insolation and gas firing, from transfer of enthalpy from a thermal storage system and gas firing, or from a combination of insolation, stored enthalpy transfer, and gas firing. Operating periods can be characterized by at least one of an insolation level, a time of day, or a stage in the operation process. The generated steam can be used in the production of electricity.