US-12624649-B2 - Hydrogen fueled electric power plant with thermal energy storage

Abstract

The invention relates generally to methods and apparatus for operation of hydrogen fueled electric power plants integrated with thermal energy storage. It is an object of this invention to reduce the cost of providing reliable electricity from variable renewable energy sources by storing excess renewable energy and using the stored renewable energy to reduce the quantity of fuel required, to reduce the cost of producing hydrogen fuel by electrolysis, and to produce and store hydrogen at the power plant to eliminate the cost of transporting hydrogen and the need to upgrade natural gas pipelines and pipeline compressors.

Inventors

• William M. Conlon

Assignees

• PINTAIL POWER LLC

Dates

Publication Date

20260512

Application Date

20250206

Claims (18)

1. 1 . A combined cycle power plant comprising: a combustion turbine generator configured to combust a fuel comprising hydrogen gas to generate electricity and produce hot exhaust gases; a second heat source, different from the combustion turbine; a thermal energy storage system configured to store heat from the second heat source; a steam turbine generator configured to expand superheated steam across a steam turbine to generate electricity; a feedwater reservoir configured to store feedwater condensed from steam exhausted from the steam turbine; a boiler configured to boil feedwater from the feedwater reservoir with heat exclusively from the thermal energy storage system to produce steam and to provide a portion of the steam to heat the feedwater reservoir; a superheater configured to heat steam produced in the boiler with heat exclusively from the thermal energy storage system to produce the superheated steam; and an electrically powered electrolyzer configured to electrolyze steam produced in the boiler to produce the hydrogen gas.
2. 2 . The combined cycle power plant of claim 1 , wherein the fuel consists essentially of the hydrogen gas.
3. 3 . The combined cycle power plant of claim 1 , wherein the fuel comprises methane mixed with the hydrogen gas.
4. 4 . The combined cycle power plant of claim 1 , comprising: a compressor configured to compress the hydrogen gas produced in the electrolyzer; and a hydrogen storage tank configured to store hydrogen gas compressed by the compressor for subsequent combustion in the combustion turbine generator.
5. 5 . The combined cycle power plant of claim 1 , wherein the electrolyzer is electrically connected to be powered by electricity generated by the steam turbine generator.
6. 6 . The combined cycle power plant of claim 1 , wherein the electrolyzer is or comprises a solid oxide electrolyzer.
7. 7 . The combined cycle power plant of claim 1 , wherein the second heat source is an electrically powered heater.
8. 8 . The combined cycle power plant of claim 1 , wherein the thermal energy storage system comprises a molten salt.
9. 9 . The combined cycle power plant of claim 1 , wherein the electrolyzer is fluidly coupled to electrolyze steam produced in the boiler and not further heated before reaching the electrolyzer.
10. 10 . The combined cycle power plant of claim 9 , wherein: the electrolyzer is or comprises a solid oxide electrolyzer; the second heat source is an electrically powered heater; and the thermal energy storage system comprises a molten salt.
11. 11 . The combined cycle power plant of claim 1 , wherein the electrolyzer is fluidly coupled to electrolyze steam produced in the boiler and superheated by heat exchange with the hydrogen produced in the electrolyzer.
12. 12 . The combined cycle power plant of claim 11 , wherein: the electrolyzer is or comprises a solid oxide electrolyzer; the second heat source is an electrically powered heater; and the thermal energy storage system comprises a molten salt.
13. 13 . The combined cycle power plant of claim 1 , wherein the electrolyzer is fluidly coupled to electrolyze steam produced in the boiler, superheated in the superheater, and extracted partially expanded from the steam turbine generator.
14. 14 . The combined cycle power plant of claim 13 , wherein: the electrolyzer is or comprises a solid oxide electrolyzer; the second heat source is an electrically powered heater; and the thermal energy storage system comprises a molten salt.
15. 15 . The combined cycle power plant of claim 1 , wherein the electrolyzer is fluidly coupled to electrolyze steam produced in the boiler, superheated in the superheater, extracted partially expanded from the steam turbine generator, and reheated by heat exchange with the hydrogen produced in the electrolyzer.
16. 16 . The combined cycle power plant of claim 15 , wherein: the electrolyzer is or comprises a solid oxide electrolyzer; the second heat source is an electrically powered heater; and the thermal energy storage system comprises a molten salt.
17. 17 . The combined cycle power plant of claim 1 , wherein the electrolyzer is fluidly coupled to electrolyze steam produced in the boiler, superheated in the superheater, and bypassing the steam turbine generator.
18. 18 . The combined cycle power plant of claim 17 , wherein: the electrolyzer is or comprises a solid oxide electrolyzer; the second heat source is an electrically powered heater; and the thermal energy storage system comprises a molten salt.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. patent application Ser. No. 18/230,914 filed Aug. 7, 2023, which is a continuation-in-part of International Patent Application No. PCT/US2022/015417 filed Feb. 7, 2022, which claims benefit of priority to U.S. Patent Application No. 63/147,044 filed Feb. 8, 2021, each of which is incorporated herein by reference in its entirety. FIELD OF THE INVENTION The invention relates generally to methods and apparatus for operation of hydrogen fueled electric power plants integrated with thermal energy storage. BACKGROUND Renewable resources are so abundant in some places that after displacing fossil fuel generation, the renewables must also be curtailed. For example, on Apr. 21, 2019, before COVID related load reductions, the California Independent System Operator (CAISO) curtailed almost 32 GWh of solar energy because generation exceeded demand. For both economic and environmental reasons, it is essential to store this otherwise curtailed energy for use when the natural variability of renewable resources demands backup from dispatchable generation. Each day, as solar production begins, the CAISO grid experiences a large and rapid drop in net load that forces combined cycle plants off-line. And as solar production wanes in the late afternoon, these plants must rapidly come back on-line. These two related grid operational issues—over-generation and renewable curtailment, and steep ramps in the load served by CAISO are phenomena that create the now famous “Duck Curve” shown in FIG. 1. National, regional and local governments throughout the world have established laws, mandates, and targets for still larger amounts of renewable energy. For example, in 2018, California enacted SB-100, which mandates that 60% of retail electricity (i.e., electricity delivered to customers) is from renewable resources, which was defined to exclude large hydro and nuclear power. As VRE increases, the “neck” of the Duck gets steeper and the “belly” of the Duck gets deeper so that the base load is eliminated, as illustrated in FIG. 2 for a 50% renewable portfolio. Under such a scenario, power plants would not operate to serve base load, but would be dispatched as a complement to renewable generation. The excess renewable generation and electricity from less flexible plants would also be stored and time-shifted. The renewable resources are preferentially dispatched because they have very low (often zero) marginal cost, which places them first in the economic merit order. In contrast, conventional power generation has variable costs per MWh for fuel and O&M (operations and maintenance). The cost-duration curve of FIG. 3 shows that an electric power market with moderate quantities of wind and solar VRE will have four distinct economic opportunities for power plants: A, High value peaking power for several hundred hours per year; B, Moderate value plateau for about five thousand hours per year; C, Ramping need for about one thousand hours per year; D, Zero marginal cost for about two thousand hours per year. There is a further need to reduce Greenhouse Gas (GHG) emissions by storing excess renewable generation for use when renewable energy is not available, reducing the amount of fuel consumed by dispatchable power systems used to back up the variable renewable energy, producing renewable fuels by capturing and recycling GHGs, capturing and sequestering GHG emissions, or by using hydrogen fuel to eliminate GHG emissions. Hydrogen is commonly produced from natural gas using a steam-methane reforming process which produces carbon dioxide as a byproduct that could be captured and sequestered. Alternatively, hydrogen could be produced by using excess renewable or nuclear power to split water by electrolysis into its constituents without GHG emissions. Hydrogen, whether produced from natural gas or by electrolysis of water is several times more expensive than natural gas, so its use as a fuel in conventional thermal power plants would increase the cost of electricity. SUMMARY It is an object of this invention to reduce the cost of providing reliable electricity from variable renewable energy sources by storing excess renewable energy and using the stored renewable energy to reduce the quantity of fuel required. A second object of this invention is to reduce the cost of producing hydrogen fuel by electrolysis. A third object of this invention is to produce and store hydrogen at the power plant to eliminate the cost of transporting hydrogen and the need to upgrade natural gas pipelines and pipeline compressors. In a first aspect of the invention, an electric power plant comprises a combustion turbine generator that combusts hydrogen fuel, or a blend of hydrogen and natural gas 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 ste