Dispatchable combined cycle power plant
A combined cycle power plant comprises a combustion turbine generator, another heat source in addition to the combustion turbine generator, a steam power system, and an energy storage system. Heat from the heat source, from the energy storage system, or from the heat source and the energy storage system is used to generate steam in the steam power system. Heat from the combustion turbine generator exhaust gas may be used primarily for single phase heating of water or steam in the steam power system. Alternatively, heat from the combustion turbine generator exhaust gas may be used in parallel with the energy storage system and/or the other heat source to generate steam, and additionally to super heat steam. Both the combustion turbine generator and the steam power system may generate electricity.
1. A 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 other than the combustion turbine;
a thermal energy storage system that stores heat transferred from the second heat source;
a steam turbine generator that expands superheated steam across a steam turbine to generate electricity;
a first boiler; and
a superheater;
wherein the combined cycle electric power plant has a first mode of operation in which the superheated steam is produced by heating condensate from the steam turbine generator primarily with heat from the combustion turbine exhaust gases to produce hot liquid feedwater, boiling the hot liquid feedwater in the first boiler with heat primarily from the second heat source, from the thermal energy storage system, or from the second heat source and the thermal energy storage system to produce steam, and superheating the steam in the superheater primarily with additional heat from the combustion turbine exhaust gases.
2. The combined cycle electric power plant of claim 1 , wherein in the first mode of operation the superheated steam is produced by heating condensate from the steam turbine generator exclusively with heat from the combustion turbine exhaust gases to produce hot liquid feedwater, boiling the hot liquid feedwater in the first boiler with heat exclusively from the second heat source, from the thermal energy storage system, or from the second heat source and the thermal energy storage system to produce steam, and superheating the steam in the superheater exclusively with additional heat from the combustion turbine exhaust gases.
3. The combined cycle electric power plant of claim 1 , having a second mode of operation wherein the superheated steam is produced using heat exclusively from the combustion turbine exhaust gases.
4. The combined cycle electric power plant of claim 1 , wherein the thermal energy storage system stores heat in a low vapor pressure heat transfer fluid at a pressure of about one atmosphere and a temperature greater than or equal to about 300° C.
5. The combined cycle electric power plant of claim 4 , wherein the thermal energy storage system provides heat to boil the hot liquid feedwater by heat exchange between the low vapor pressure heat transfer fluid and the hot liquid feedwater.
6. The combined cycle electric power plant of claim 1 , wherein the superheated steam has a pressure of about 70 bar and a temperature of about 470° C. at an inlet to the steam turbine.
7. The combined cycle electric power plant of claim 1 , wherein the second heat source is or comprises a solar thermal system that concentrates solar radiation to collect solar energy as heat.
8. The combined cycle electric power plant of claim 1 , wherein the second heat source is or comprises another combustion turbine generator.
9. The combined cycle electric power plant of claim 1 , wherein the second heat source is or comprises an electrically powered heater.
10. The combined cycle electric power plant of claim 1 , wherein:
in the first mode of operation the superheated steam is produced by heating condensate from the steam turbine generator exclusively with heat from the combustion turbine exhaust gases to produce hot liquid feedwater, boiling the hot liquid feedwater in the first boiler with heat exclusively from the second heat source, from the thermal energy storage system, or from the second heat source and the thermal energy storage system to produce steam, and superheating the steam in the superheater exclusively with additional heat from the combustion turbine exhaust gases;
the thermal energy storage system stores heat in a low vapor pressure heat transfer fluid at a pressure of about one atmosphere and a temperature greater than or equal to about 300° C.;
the thermal energy storage system provides heat to boil the hot liquid feedwater by heat exchange between the low vapor pressure heat transfer fluid and the hot liquid feedwater; and
the superheated steam has a pressure of about 70 bar and a temperature of about 470° C. at an inlet to the steam turbine.
11. The combined cycle electric power plant of claim 1 comprising a second boiler;
wherein in the first mode of operation additional condensate from the steam turbine generator is heated exclusively with heat from the combustion turbine exhaust gases to produce additional hot liquid feedwater, the additional hot liquid feedwater is boiled in the second boiler with heat exclusively from the combustion turbine exhaust gases to produce additional steam, and the superheated steam is produced in the superheater by heating a mixture of steam from the first boiler and the additional steam from the second boiler with heat exclusively from the combustion turbine exhaust gases.
12. The combined cycle electric power plant of claim 11 , having a second mode of operation wherein the superheated steam is produced in the superheater by heating steam exclusively from the second boiler with heat exclusively from the combustion turbine exhaust gases.
13. The combined cycle electric power plant of claim 11 , wherein the superheated steam has a pressure of about 60 bar and a temperature of about 550° C. at an inlet to the steam turbine generator.
14. The combined cycle electric power plant of claim 11 , wherein the second heat source is or comprises a solar thermal system that concentrates solar radiation to collect solar energy as heat.
15. The combined cycle electric power plant of claim 11 , wherein the second heat source is or comprises another combustion turbine generator.
16. The combined cycle electric power plant of claim 11 , wherein the second heat source is or comprises an electrically powered heater.
17. The combined cycle electric power plant of claim 11 , comprising a feedwater heater that heats liquid condensate from the steam turbine generator with heat from the combustion turbine exhaust gases and provides a first stream of the heated liquid condensate to the first boiler and a second stream of the heated liquid condensate to the second boiler.
18. The combined cycle electric power plant of claim 17 , wherein the mass flow rate of the second stream of heated liquid condensate is about four times the mass flow rate of the first stream of heated liquid condensate.