Solar Thermal Power System

A method of operating a solar thermal power system, comprising:

• providing a solar receiver;
• with a thermal energy storage arrangement, circulating a thermal energy storage fluid through the solar receiver to store thermal energy;
• operating a multistage steam turbine on variable pressure steam generated from feedwater supplied from a feedwater supply via the thermal energy storage fluid;
• providing a steam generator arrangement comprising an economizer section, an evaporator section and a superheater section that utilizes heat of the thermal energy storage fluid at an entrance of the evaporator section to generate and supply the variable pressure steam to the superheater section and further to the multistage steam turbine;
• providing a recirculation line around the economizer section, the recirculation line having an inlet and an outlet, the inlet of the recirculation line disposed at one of an outlet from the economizer section or the evaporator section, the outlet of the recirculation line disposed at an inlet to the economizer, and the recirculation line configured directly between the inlet and the outlet of the recirculation line such that all heated water directed into the inlet of the recirculation line is discharged at the outlet of the recirculation line;
• and
• increasing heat load on the economizer section and, in turn, increasing pressure range of the variable pressure steam in the steam generator arrangement, while maintaining the temperature of the thermal energy storage fluid at an inlet of the evaporator section and at an outlet of the economizer section, and the feedwater temperature to the economizer section at desired values;
• and
• adjusting recirculation through the recirculation line to control water inlet temperature to the economizer section.