Start-up and control of liquid salt energy storage combined cycle systems

A method of operating a combined cycle power plant,

• the combined cycle electric power plant comprising:
• a combustion turbine generator that combusts fuel to generate electricity and produce hot exhaust gases;
• a second heat source, different from the combustion turbine;
• a thermal energy storage system that stores heat from the second heat source;
• a steam turbine generator that expands superheated steam across a steam turbine to generate electricity;
• a feedwater reservoir that stores feedwater condensed from steam exhausted from the steam turbine;
• a feedwater preheater configured to heat feedwater from the feedwater reservoir with heat exclusively from the combustion turbine exhaust gases;
• a boiler configured to boil feedwater from the feedwater preheater with heat exclusively from the thermal energy storage system to generate steam;
• a superheater configured to heat steam from the boiler exclusively with heat from the combustion turbine exhaust gases to generate the superheated steam;
• a third heat source, different from the combustion turbine;
• and
• a startup feedwater heater configured to use heat from the third heat source to heat feedwater from the feedwater reservoir to a temperature greater than a freezing point of a heat transfer fluid used to transfer the heat from the thermal energy storage system to the boiler;
• the method comprising heating feedwater from the feedwater reservoir to a temperature greater than the freezing point of the heat transfer fluid using the startup feedwater heater.