Dispatchable storage combined cycle power plants

A method of operating a combined cycle electric power plant, the method comprising:

• operating a topping cycle that combusts fuel to generate electricity and produce hot exhaust gases;
• storing heat from a heat source other than the topping cycle in a thermal energy storage system at a temperature T1;
• in a first mode of operation:
• producing steam in a boiler by heating feedwater with heat supplied at temperature T1 from the thermal energy storage system by a heat transfer fluid, thereby cooling the heat transfer fluid, and storing heat from the cooled heat transfer fluid in the thermal energy storage system at a temperature T2<T1;
• heating the steam from the boiler with heat from the topping cycle exhaust gases to produce superheated steam at pressure P1;
• and
• expanding the superheated steam at pressure P1 through a steam turbine generator to generate electricity;
• and in a second mode of operation, after depleting the thermal energy storage system of heat stored at temperature T1:
• producing steam in the boiler by heating feedwater with heat supplied from the thermal energy storage system at a temperature of T2 or less by the heat transfer fluid;
• heating the steam from the boiler with heat from the topping cycle exhaust gases to produce superheated steam at pressure P2<P1;
• and
• expanding the superheated steam at pressure P2 through the steam turbine generator to generate electricity.