A system for generating electricity or hydrogen from natural gas

Abstract

The present invention discloses a system for generating electricity or hydrogen from natural gas and connectable between a gas main and a local gas distribution line. The system includes a thermal energy storage unit containing a thermal energy storage material that is heated by an energy source. The system also includes a heat exchanger in fluid communication with the thermal energy storage unit for receiving a natural gas stream from the gas main and a heating fluid from the thermal energy storage unit for heating the natural gas stream. The system also includes an expander in fluid communication with the heat exchanger for receiving the heated natural gas stream from the heat exchanger and for expanding the heated natural gas stream to cool it and reduce its pressure. An electric generator connected to the expander generates electricity from the expansion of the heated natural gas stream through the expander.

Description

[Technical field]

[0001] INCORPORATION BY REFERENCE TO PRIORITY APPLICATION Any application for which a claim of foreign or domestic priority is identified in an Application Data Sheet filed with this application is hereby incorporated by reference under 37 CFR 1.57. This application claims priority to U.S. Provisional Patent Application No. 63 / 363,232, filed April 19, 2022, which is incorporated by reference in its entirety and is considered a part of this specification.

[0002] Technical Field The present invention relates to green energy generation, and more particularly to systems and methods for generating electricity or hydrogen from natural gas using renewable energy sources. [Background technology]

[0003] Natural gas is a non-renewable energy source and a widely used fossil fuel (e.g. for heating, cooking, electricity generation, etc.). In order to reduce greenhouse gas emissions into the atmosphere, there is an emphasis on reducing the use of fossil fuels. Summary of the Invention

[0004] What is needed is a system and method that reduces the use of natural gas in electricity generation.

[0005] According to one aspect of the disclosure, a system is provided for generating electricity or producing hydrogen by heating and expanding natural gas between a gas main and a local gas distribution line to capture energy that would otherwise be lost to entropy by expanding the gas between the gas main and a local gas distribution line through a valve (e.g., a throttling valve).

[0006] In some aspects, the technology described herein relates to a system configured to generate electricity or hydrogen from natural gas and to be connected to a gas main and a local gas distribution line. The system includes a thermal energy storage unit containing a thermal energy storage material and configured to receive energy from an energy source to heat the thermal energy storage material. The system also includes a heat exchanger in fluid communication with the thermal energy storage unit and configured to receive a natural gas stream from the gas main and a heating fluid from the thermal energy storage unit that heats the natural gas stream. The system also includes an expander in fluid communication with the heat exchanger and configured to receive a heated natural gas stream from the heat exchanger and expand the heated natural gas stream to cool it and reduce its pressure. The system also includes a generator connected to the expander and configured to generate electricity by expansion of the heated natural gas stream by the expander.

[0007] In some aspects, the technology described herein relates to a system in which the thermal energy storage unit, the heat exchanger, the expander, and the generator are part of a stand-alone portable unit.

[0008] In some embodiments, the technology described herein relates to systems in which the energy source is a renewable energy source.

[0009] In some aspects, the technology described herein relates to a system in which the energy source is a solar power plant.

[0010] In some aspects, the technology described herein relates to a system in which the energy source is a concentrated solar power plant.

[0011] In some aspects, the technology described herein relates to a system in which the energy source is the electrical grid.

[0012] In some embodiments, the technology described herein relates to systems in which the thermal energy storage material is water.

[0013] In some embodiments, the technology described herein relates to systems in which the thermal energy storage material is pressurized water.

[0014] In some aspects, the technology described herein relates to systems in which the thermal energy storage material comprises a solid material.

[0015] In some aspects, the technology described herein relates to systems in which the thermal energy storage material comprises rock.

[0016] In some aspects, the technology described herein relates to a system in which the thermal energy storage material comprises packed gravel.

[0017] In some aspects, the technology described herein relates to a system in which the expander includes a first expander and a second expander.

[0018] In some embodiments, the technology described herein relates to a system in which the heat exchanger includes a first heat exchanger between a gas main and a first expander, and a second heat exchanger between the first expander and a second expander.

[0019] In some aspects, the technology described herein relates to a system further including an electrolyzer configured to receive electricity generated from the generator and generate hydrogen.

[0020] In some aspects, the technology described herein relates to a system in which generated hydrogen is injected into a local gas distribution pipe.

[0021] In some aspects, the technology described herein relates to systems in which generated hydrogen is injected into a line separate from the local gas distribution line.

[0022] In some aspects, the technology described herein relates to a system in which generated electricity is fed into an electrical grid.

[0023] In some aspects, the technology described herein relates to a method of generating electricity or hydrogen from natural gas, the method including heating a natural gas stream flowing between a gas main and a local gas distribution line through a heat exchanger, the method also including expanding the heated natural gas stream received from the heat exchanger through an expander, the method including generating electricity by expansion of the heated natural gas stream through the expander.

[0024] In some aspects, the technology described herein relates to a method, wherein heating the natural gas stream includes receiving a heating fluid from a thermal energy storage unit in a heat exchanger to heat the natural gas stream.

[0025] In some aspects, the technology described herein relates to a method in which expanding the heated natural gas stream includes cooling the heated natural gas stream to reduce its pressure.

[0026] In some aspects, the technology described herein relates to methods in which the step of expanding the heated natural gas stream is performed in multiple stages.

[0027] In some aspects, the technology described herein relates to methods that include generating hydrogen via an electrolyzer powered by generated electricity.

[0028] In some aspects, the technology described herein relates to a method that includes injecting the generated hydrogen into a local gas distribution pipe.

[0029] In some aspects, the technology described herein relates to methods that include injecting the generated hydrogen into a line separate from the local gas distribution line.

[0030] In some aspects, the technology described herein relates to a method that includes providing at least a portion of the generated electricity to a power grid. [Brief description of the drawings]

[0031] [Figure 1] 1 is a schematic diagram of a system for generating electricity from natural gas. [Diagram 2] 1 is a schematic diagram of another system for generating electricity from natural gas. [Diagram 3] FIG. 1 is a schematic diagram of a stand-alone system for generating electricity from natural gas. [Figure 4] FIG. 1 is a schematic diagram of a stand-alone system for generating hydrogen from natural gas. [Diagram 5] FIG. 1 is a schematic diagram of a stand-alone system for generating electricity from natural gas. [Figure 6] FIG. 1 is a schematic diagram of a stand-alone system for generating hydrogen from natural gas. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] FIG. 1 illustrates a system 100 for utilizing natural gas to generate electricity or hydrogen. Natural gas (e.g., a hydrocarbon gas mixture including methane) is delivered from a source to a city or industrial site through a gas main 10 at a pressure ranging from about 25 bar to about 100 bar (e.g., about 363 Psi to about 1450 Psi, 75 bar, or 1087 Psi). The natural gas is transported from the gas main 10 through a connecting line 93 to a local distribution line 90 to which a valve 95 (e.g., a throttling valve) is coupled. The valve 95 can be operated to reduce the pressure of the natural gas in the local distribution line 90 to a lower pressure, for example, about 5 bar (e.g., about 73 Psi). The local distribution line 90 can be connected to a gas distribution line (not shown) that delivers the natural gas to homes, businesses, and industrial sites.

[0033] In one embodiment, system 100 advantageously uses a portion (e.g., 5%) of the natural gas flowing through gas mains 10 to generate electricity, by way of example, using a renewable energy source, and deliver the electricity to an electric grid or to an electrical storage device (e.g., a battery). In another embodiment, as described further below, system 100 advantageously uses a portion (e.g., 5%) of the natural gas flowing through gas mains 10 to generate hydrogen, by way of example, using a renewable energy source, and deliver the generated hydrogen, as described further below. In other embodiments, as described further below, electricity from the electric grid is used to generate electricity or hydrogen instead of a renewable energy source.

[0034] The system 100 includes a thermal energy storage unit 20 capable of storing thermal energy. In one embodiment, the thermal energy storage unit 20 can contain a liquid thermal energy storage material (e.g., water, pressurized water). In another embodiment, the thermal energy storage unit 20 can contain a solid thermal energy storage material (e.g., a packed bed of rocks, gravel). The thermal energy storage unit 20 can receive heat or energy from an energy source 30 to heat the thermal energy storage material, for example, to a temperature of about 100°C to about 160°C, inclusive. In one embodiment, the energy source 30 is an electrical grid that delivers electricity to the thermal energy storage unit 20 (e.g., a resistor in the thermal energy storage unit 20 that heats the thermal energy storage material). In another embodiment, the energy source 30 is a renewable energy source, for example, a solar (e.g., photovoltaic or PV) energy source or a wind energy source, that provides electricity to, for example, a resistive heater (e.g., an electrical resistor) in the thermal energy storage unit 20 that can heat the thermal energy storage material. In another embodiment, the renewable energy source may be a concentrated solar thermal energy source (e.g., concentrated solar power or CSP) that delivers heated air or heated liquid to the thermal energy storage unit 20 to heat the thermal energy storage material.

[0035] The thermal energy storage unit 20 is connected to the heat exchanger 40 via the pipe 22. When the thermal energy storage material is water, the thermal energy storage unit 20 supplies heated water to the heat exchanger 40 via the pipe 22. When the thermal energy storage material is a solid (e.g., rock, packed gravel), the thermal energy storage unit 20 supplies heated air to the heat exchanger 40 via the pipe 22. The heat exchanger 40 is connected to the gas main 10 via the pipe 42. The pipe 42 guides a certain amount of natural gas (e.g., 5% to 10% (including the boundary) of the amount supplied from the gas main 10) from the gas main 10 to the heat exchanger 40, and in the heat exchanger 40, the natural gas is heated by the heating fluid supplied by the thermal energy storage unit 20.

[0036] The heated natural gas leaves the heat exchanger 40 via a line 44 that directs the heated natural gas to an expander 50 (e.g., a turbine), which expands and cools the heated natural gas, and the cooled gas is provided to the local distribution pipe 90 via a line 52 at the nominal pressure of the natural gas in the local distribution pipe 90 (e.g., a nominal pressure of 5 bar, 4.8 to 5.2 bar, etc.). In one embodiment, the expander 50 is a single stage expander (e.g., a single stage turbine). In another embodiment, the expander 50 may be a two-stage expander (e.g., a two-stage turbine), as described further below. The expander 50 (e.g., an output shaft of the expander 50) is connected to an electric generator (e.g., an electric generator) 60, which generates electricity when the expander 50 (e.g., a turbine) expands the natural gas. In one embodiment, the electricity generated by the generator 60 is provided to an electrical grid. In another embodiment, as described further below, electricity generated by the generator 60 is supplied to the electrolyzer to generate hydrogen. In one embodiment, the generator 60 may be a synchronous generator (e.g., capable of rotating at 3600 rpm to synchronize with the grid) and the expander 50 may rotate at 5000 or 6000 rpm (e.g., with a gearbox between the two). In another embodiment, when the system 100 is used to generate hydrogen using an electrolyzer (as described further below), the generator may be a DC generator (e.g., a 0.5 MW generator) rotating at 10000 or 20000 rpm and operating with the expander 50 rotating at 20000 rpm, which may be connected to the electrolyzer via a DC-DC converter, and the energy source supplying energy to the thermal energy storage unit 20 may be a renewable energy source (e.g., a solar power plant) providing 1 MW or 2 MW.

[0037] FIG 2 illustrates a system 100' for generating electricity or hydrogen using natural gas. Certain features of the system 100' are similar to those of the system 100 in FIG 1. Accordingly, the reference numerals designating various components of the system 100' are the same as the reference numerals identifying corresponding components of the system 100 in FIG 1. Accordingly, it should be understood that the construction and description of the various features and components of the system 100 in FIG 1, as well as the methods of operation and control thereof, also apply to corresponding features and components of the system 100' in FIG 2, except as described below.

[0038] System 100' differs from system 100 in that it includes two-stage expanders (e.g., first expander 50A and second expander 50B, e.g., a two-stage turbine), two heat exchangers (e.g., first heat exchanger 40A and second heat exchanger 40B), and two generators (e.g., first generator 60A and second generator 60B), or optionally a single generator (e.g., generator 60). Pipe 42A connects gas main 10 to first heat exchanger 40A to conduct natural gas to heat exchanger 40A, where the natural gas is heated by heating fluid (e.g., heated air, heated water) from thermal energy storage unit 20. The heated natural gas leaves first heat exchanger 40A via pipe 44A and flows into first expander 50A, where the heated natural gas is expanded and cooled. The first expander 50A is connected (e.g., via an output shaft) to a first generator 60A, which generates electricity by expanding natural gas through the first expander 50A. The cooled natural gas leaves the first expander 50A via pipe 42B and is directed to a second heat exchanger 40B, where the natural gas is heated by a heating fluid (e.g., heated air, heated water) from the thermal energy storage unit 20. The heated natural gas leaves the second heat exchanger 40B via pipe 44B and flows into the second expander 50B, where the heated natural gas is expanded and cooled. The second expander 50B is connected (e.g., via an output shaft) to a second generator 60B, which generates electricity by expanding natural gas through the second expander 50B. Alternatively, both expanders 50A, 50B are connected to a single generator (e.g., generator 60 shown in Figures 5-6) instead of two separate generators 60A, 60B. The heated natural gas exits the second expander 50B, which expands and cools the heated natural gas, and the cooled gas is supplied to the local distribution pipe 90 via pipe 52 at the nominal pressure of the natural gas in the local distribution pipe 90 (e.g., a nominal pressure of 5 bar, 4.8-5.2 bar, etc.). In another embodiment, as further described below, electricity generated by the generators 60A, 60B is supplied to an electrolyzer to generate hydrogen.

[0039] Advantageously, by using a two-stage expander in system 100' (e.g., expander 50A and expander 50B with reheat through intermediate heat exchanger 40B), system 100' can reduce the pressure drop between each stage, thereby facilitating the design of thermal energy storage unit 20 and the thermal energy storage material used. For example, if gas main 10 operates at a pressure of 100 bar and local gas distribution pipe 90 operates at a nominal pressure of 5 bar, with two-stage expansion, first expander 50A can reduce the pressure of the natural gas from 100 bar to approximately 20 bar, and second expander 50B can reduce the pressure of the natural gas from 20 bar to 5 bar. Advantageously, the two-stage expansion allows the thermal energy storage material to have a temperature of 100°C to 160°C (e.g., 120°C) relative to the fluid supplied to the heat exchangers 40A, 40B, thereby allowing water (e.g., pressurized water at about 3 to 6 bar in a boiler) to be used as the thermal energy storage material. In such an embodiment, the thermal energy storage unit 20 can be simplified in design (e.g., a boiler for pressurized water) and thereby the systems 100, 100', 100A-100D can be supplied as a package or stand-alone system. On the other hand, if a single state expansion is used in the system, the pressure drop from 100 bar to 5 bar by the expander requires the thermal energy storage material to have a temperature of about 300°C relative to the fluid supplied to the heat exchanger.

[0040] FIG 3 illustrates a system 100A that utilizes natural gas to generate electricity. Certain features of the system 100A are similar to those of the system 100 in FIG 1. Accordingly, the reference numerals designating various components of the system 100A are the same as the reference numerals identifying corresponding components of the system 100 in FIG 1. Accordingly, it should be understood that the construction and description of the various features and components of the system 100 in FIG 1, as well as the methods of operation and control thereof, also apply to corresponding features and components of the system 100A in FIG 3, except as described below.

[0041] System 100A differs from system 100 in that it is a stand-alone system that is optionally housed in a container 2A or mounted on a frame. System 100A can be advantageously transported (e.g., in a container 2A) to a location where system 100A can be connected to a gas main and a local gas distribution (e.g., gas main 10 and local gas distribution 90). In one example, multiple systems 100A can be transported to different locations in a geographic region (e.g., outside a city or county) where an existing gas distribution network exists, with each system 100A connected to a gas main and a local gas distribution, thereby advantageously providing for energy resiliency (e.g., multiple systems 100A can be operational when one system requires maintenance, whether scheduled or unscheduled).

[0042] The system 100A may be connected via connector 41 to a gas main (e.g., gas main 10 operating at a relatively high delivery pressure, such as 25-100 bar) to direct a portion of the natural gas flowing through the gas main to heat exchanger 40 and then to expander 50. The system 100A in the container 2A may be connected via connector 53 to a local distribution pipe (e.g., local distribution pipe 90) to return said portion of the natural gas in an expanded state at a relatively low pressure (e.g., a nominal pressure of 5 bar). The system 100A may also have a connection 31, for example, via which electrical energy (e.g., from a solar power plant or an electrical grid) is provided to the thermal energy storage unit 20 to heat a thermal energy storage material therein (e.g., via a resistive heater), which then provides a heating fluid (e.g., heated air, hot water, hot pressurized water) to the heat exchanger 40 to heat said portion of the natural gas. In another embodiment, for example, via the connection 31, a heating fluid (e.g., heated air, heated water from a concentrated solar power plant) is provided to the thermal energy storage unit 20, which then provides a heating fluid (e.g., heated air, hot water, hot pressurized water) to the heat exchanger 40 to heat said portion of the natural gas. The system 100A may have an electrical connection 70, via which electricity generated by the generator 60 may be supplied outside the container 2A (e.g., to a power grid, an energy storage unit such as a battery, etc.).

[0043] FIG. 4 illustrates a system 100B for generating hydrogen using natural gas. Some features of the system 100B are similar to those of the system 100A in FIG. 3, which is based on the system 100 in FIG. 1. Accordingly, the reference numbers indicating various components of the system 100B are the same as the reference numbers identifying the corresponding components of the system 100A in FIG. 3. Accordingly, it should be understood that the configuration and description of the various features and components of the system 100A in FIG. 3, as well as the methods of operation and control thereof, based on the configuration and description of the various features of the system 100 in FIG. 1, also apply to the corresponding features and components of the system 100B in FIG. 4, except as described below.

[0044] System 100B differs from system 100A in that generator 60 supplies electricity to electrolyzer 80 to generate hydrogen, which can exit the system via tube and / or connector 81. Electrolyzer 80 can be a conventional electrolyzer (e.g., an alkaline electrolyzer using potassium hydroxide) that produces hydrogen at a pressure of, for example, 16 bar to 30 bar. System 100B is a stand-alone system that is optionally housed in container 2B or mounted on a frame. System 100B can be advantageously transported (e.g., in container 2B) to a location where system 100B can be connected to a gas main and a local gas distribution line (e.g., gas main 10 and local gas distribution line 90). In one embodiment, the generated hydrogen can be supplied to the container in compressed or pressurized form and transported. In another embodiment, the generated hydrogen can be injected into a line parallel to the local gas distribution line (e.g., line 90). In yet another embodiment, the generated hydrogen can be directly injected into the local gas distribution pipe (e.g., pipe 90), for example, such that 5-10% of the hydrogen flows through the local gas distribution pipe, thereby advantageously reducing greenhouse gas emissions of the distributed gas. In one embodiment, the hydrogen generated by electrolyzer 80 is green hydrogen if the energy source providing electricity or heating fluid (e.g., heated air, heated water) to thermal energy storage unit 20 is a renewable energy source (e.g., photovoltaic power plant, concentrated solar thermal energy plant).

[0045] FIG. 5 illustrates a system 100C for generating electricity using natural gas. Some features of the system 100C are similar to those of the system 100′ in FIG. 2. Accordingly, the reference numerals identifying various components of the system 100C are the same as the reference numerals identifying corresponding components of the system 100′ in FIG. 2. Accordingly, it should be understood that the construction and description of the various features and components of the system 100′ in FIG. 2, as well as the methods of operation and control thereof, also apply to corresponding features and components of the system 100C in FIG. 5, except as described below.

[0046] System 100C differs from system 100' in that it is a stand-alone system that is optionally housed in a container 2C or mounted on a frame. System 100C can be advantageously transported (e.g., in a container 2C) to a location where system 100C can be connected to a gas main and a local gas distribution line (e.g., gas main 10 and local gas distribution line 90).

[0047] In one example, multiple systems 100C can be provided in different locations in a geographic region (e.g., outside a city or county) where an existing gas distribution network exists, with each system 100C connected to a gas main and a local gas distribution line, thereby advantageously providing for energy resiliency (e.g., multiple systems 100C can operate, whether scheduled or unscheduled, when one system requires maintenance).

[0048] System 100C may be connected via connector 41 to a gas main (e.g., gas main 10 operating at a relatively high delivery pressure, such as 25-100 bar) as described above, to direct a portion of the natural gas flowing through the gas main to heat exchanger 40A and then to expander 50A. System 100C in container 2C may be connected via connector 53 to a local distribution pipe (e.g., local distribution pipe 90) to return the portion of the natural gas in an expanded state at a relatively low pressure (e.g., a nominal pressure of 5 bar). The system 100C may also have a connection 31, for example, via which electrical energy (e.g., from a solar power plant or a power grid) is provided to the thermal energy storage unit 20 to heat a thermal energy storage material therein (e.g., via a resistance heater), which then provides a heating fluid (e.g., heated air, hot water, hot pressurized water) to the heat exchangers 40A, 40B to heat the portion of the natural gas. In another embodiment, for example, via the connection 31, a heating fluid (e.g., heated air, heated water from a concentrated solar power plant) is provided to the thermal energy storage unit 20, which then provides a heating fluid (e.g., heated air, hot water, hot pressurized water) to the heat exchangers 40A, 40B to heat the portion of the natural gas. The system 100C may have an electrical connection 70, via which electricity generated by the generator 60 (connected to the expanders 50A, 50B) may be supplied outside the container 2C (e.g., to a power grid, an energy storage unit such as a battery, etc.).

[0049] FIG. 6 illustrates a system 100D for generating hydrogen using natural gas. Some features of the system 100D are similar to those of the system 100C in FIG. 5, which is based on the system 100′ in FIG. 2. Accordingly, the reference numbers indicating various components of the system 100D are the same as the reference numbers identifying the corresponding components of the system 100C in FIG. 5. Accordingly, it should be understood that the configurations and descriptions of the various features and components of the system 100C in FIG. 5, as well as the methods of operation and control thereof, based on the configurations and descriptions of the various features of the system 100′ in FIG. 2, also apply to the corresponding features and components of the system 100D in FIG. 6, except as described below.

[0050] System 100D differs from system 100C in that generator 60 supplies electricity to electrolyzer 80 to generate hydrogen, which can exit the system via tube and / or connector 81. Electrolyzer 80 can be a conventional electrolyzer (e.g., an alkaline electrolyzer using potassium hydroxide) that produces hydrogen at a pressure of, for example, 16 bar to 30 bar. System 100D is a stand-alone system that is optionally housed in container 2D or mounted on a frame. System 100D can be advantageously transported (e.g., in container 2D) to a location where system 100D can be connected to a gas main and a local gas distribution line (e.g., gas main 10 and local gas distribution line 90). In one embodiment, the generated hydrogen can be supplied to the container in compressed or pressurized form and transported. In another embodiment, the generated hydrogen can be injected into a line parallel to the local gas distribution line (e.g., line 90). In yet another embodiment, the generated hydrogen can be directly injected into the local gas distribution pipe (e.g., pipe 90), for example, such that 5-10% of the hydrogen flows through the local gas distribution pipe, thereby advantageously reducing greenhouse gas emissions of the distributed gas (e.g., reducing CO2 emissions). In one embodiment, the hydrogen generated by electrolyzer 80 is green hydrogen if the energy source providing electricity or heating fluid (e.g., heated air, heated water) to thermal energy storage unit 20 is a renewable energy source (e.g., photovoltaic power plant, concentrated solar thermal energy plant).

[0051] Advantageously, systems 100, 100', 100A-100D can separate (in resource and time) the heat sources that generate electricity or hydrogen. For example, where electricity (e.g., 1 KWh) is provided to thermal energy storage unit 20 to heat thermal energy storage material therein, such electricity can be provided from a renewable source (e.g., a solar power plant) for a period of time (e.g., 4 hours) and provided from the grid (e.g., by bidding or underbidding electricity from the grid for a set period of time), heat from thermal energy storage unit 20 can be provided to heat exchanger 40, 40A, 40B for a different and / or longer period of time that is disconnected from the period of time during which electricity is provided to thermal energy storage unit 20. In one example, electricity can be provided to the thermal energy storage unit 20 on weekends when there is low demand for natural gas (e.g., from industry), and the thermal energy storage unit 20 can then provide stored heat to the heat exchangers 40, 40A, 40B to heat the natural gas flowing through the system 100, 100', 100A-100D for the next few days or weeks. The thermal energy storage unit 20 (e.g., storing water or rock or gravel as a thermal energy storage material) can be relatively large and inexpensive to provide heat to the heat exchangers 40, 40A, 40B for the next few days or weeks. Thus, in one embodiment, the system 100, 100', 100A-100D can be used to provide base load energy (e.g., a baseline amount of electricity or a baseline amount of hydrogen), which can be provided, for example, 24 hours a day, 7 days a week.

[0052] In one embodiment, the amount of electricity or hydrogen generated by the system 100, 100', 100A-100D can be adjusted as needed (e.g., nominal gas pressure in the local gas distribution pipe is about 5 bar but varies from 4.8 to 5.2 bar). Advantageously, the system 100, 100', 100A-100D improves the efficiency of the gas line by heating and expanding the natural gas (e.g., via the heat exchangers 40, 40A, 40B and the expanders 50, 50A, 50B). For example, for 1 KWh provided to the thermal energy storage unit 20 (e.g., to heat the thermal energy storage material therein before providing it to the heat exchanger), more than 1 KWh (e.g., 1.5, 1.7, 2.0 KWh) can be generated by expanding the heated gas (e.g., via the expanders 50, 50A, 50B). Furthermore, the efficiency of systems 100, 100', 100A-100D (e.g., at least about 150%) may reduce the energy required to be supplied to thermal energy storage unit 20. For example, if a renewable energy source, such as a photovoltaic power plant or a concentrated solar thermal energy plant, is used to heat thermal energy storage unit 20, the energy field of the plant may be reduced.

[0053] Additional Embodiments In embodiments of the present invention, the system and method for generating electricity or hydrogen from natural gas may be any of the following:

[0054] Item 1. A system configured to generate electricity or hydrogen from natural gas and to be connected to a gas main and a local gas distribution pipe, a thermal energy storage unit containing a thermal energy storage material and configured to receive energy from an energy source to heat the thermal energy storage material; a heat exchanger in fluid communication with the thermal energy storage unit and configured to receive a flow natural gas from the gas main and to receive a heating fluid from the thermal energy storage unit for heating the natural gas flow; an expander in fluid communication with the heat exchanger and configured to receive a heated natural gas stream from the heat exchanger and expand and cool the heated natural gas stream to reduce its pressure; a generator connected to the expander and configured to generate electricity from expansion of the heated natural gas stream through the expander.

[0055] Item 2. The system of item 1, wherein the thermal energy storage unit, the heat exchanger, the expander, and the generator are part of a stand-alone portable unit.

[0056] Item 3. The system of item 1 or 2, wherein the energy source is a renewable energy source.

[0057] Item 4: The system according to any one of Items 1 to 3, wherein the energy source is a solar power plant.

[0058] Item 5. The system according to any one of Items 1 to 3, wherein the energy source is a concentrated solar power plant.

[0059] Item 6. The system according to any one of Items 1 to 3, wherein the energy source is a power supply grid.

[0060] Item 7. The system according to any one of Items 1 to 6, wherein the thermal energy storage material is water.

[0061] Item 8. The system of any one of items 1 to 7, wherein the thermal energy storage material comprises pressurized water.

[0062] Item 9. The system according to any one of items 1 to 6, wherein the thermal energy storage material comprises a solid material.

[0063] Item 10. The system of any of items 1, 2, 3, 4, 5, 6, and 9, wherein the thermal energy storage material comprises rock.

[0064] Item 11. The system of any of items 1, 2, 3, 4, 5, 6, 9, and 10, wherein the thermal energy storage material comprises filler gravel.

[0065] Item 12: The system according to any one of Items 1 to 11, wherein the expander includes a first expander and a second expander.

[0066] Item 13: The system according to any one of Items 1 to 12, wherein the heat exchanger includes a first heat exchanger located between the gas main pipe and a first expander, and a second heat exchanger located between the first expander and a second expander.

[0067] Item 14. The system according to any one of Items 1 to 13, further comprising an electrolyzer configured to receive electricity generated from the generator and generate hydrogen.

[0068] Item 15. The system of item 14, wherein the generated hydrogen is injected into the local gas distribution pipe.

[0069] Item 16. The system of item 14, wherein the generated hydrogen is injected into a pipe separate from the local gas distribution pipe.

[0070] Item 17: The system according to any one of Items 1 to 13, wherein the generated electricity is supplied to a power supply grid.

[0071] Item 18. A method for generating electricity or hydrogen from natural gas, comprising: heating a natural gas stream flowing between the gas main and the local gas distribution pipe via a heat exchanger; expanding the heated natural gas stream received from the heat exchanger through an expander; generating electricity by expansion of the heated natural gas stream through the expander.

[0072] Item 19. The method of item 18, wherein heating the natural gas stream comprises receiving a heating fluid from a thermal energy storage unit in the heat exchanger to heat the natural gas stream.

[0073] Item 20. The method of any one of items 18 to 19, wherein expanding the heated natural gas stream comprises cooling the heated natural gas stream to reduce its pressure.

[0074] Item 21. The method of any one of Items 18 to 20, wherein the step of expanding the heated natural gas stream is carried out in multiple stages.

[0075] Item 22. The method according to any one of Items 18 to 21, further comprising generating hydrogen via an electrolyzer powered by the generated electricity.

[0076] Item 23. The method of item 22, further comprising injecting the generated hydrogen into the local gas distribution pipe.

[0077] Item 24. The method of item 22, further comprising injecting the generated hydrogen into a line separate from the local gas distribution line.

[0078] Item 25. The method according to any one of Items 18 to 24, further comprising the step of supplying at least a portion of the generated electricity to a power grid.

[0079] Although specific embodiments of the present invention have been described, these embodiments are presented by way of example only and are not intended to limit the scope of the present disclosure. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions, and modifications of the systems and methods described herein may be made without departing from the spirit of the present disclosure. The appended claims and their equivalents are intended to cover such forms or modifications as fall within the scope and spirit of the present disclosure. Thus, the scope of the present invention is defined solely by reference to the appended claims.

[0080] It should be understood that features, materials, properties, or groups described in connection with a particular aspect, embodiment, or example are applicable to any other aspect, embodiment, or example described in this section or elsewhere in this specification, unless inconsistent therewith. All of the features disclosed in this specification (including the accompanying claims, abstract, and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive. Protection is not limited to the details of any of the foregoing embodiments. Protection extends to any novel, or any novel combination of features disclosed in this specification (including the accompanying claims, abstract, and drawings), or any novel, or any novel combination of steps of any method or process so disclosed.

[0081] Moreover, certain features described in this disclosure in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, although features may be described above as functioning in a particular combination, one or more features from a claimed combination can, in some cases, be deleted from the combination, and the combination can be claimed as a subcombination or a variation of the subcombination.

[0082] Furthermore, although operations may be shown in the figures or described in the specification in a particular order, such operations need not be performed in the particular order shown, or in sequential order, to achieve desirable results, and not all operations need to be performed. Other operations not shown or described may be incorporated into the exemplary methods and processes. For example, one or more additional operations may be performed before, after, simultaneously with, or between any of the described operations. Furthermore, operations may be rearranged or reordered in other implementations. Those skilled in the art will appreciate that in some embodiments, the actual steps performed in the illustrated and / or disclosed processes may differ from those shown in the figures. Depending on the embodiment, certain of the steps described above may be omitted and other steps may be added. Furthermore, the features and attributes of certain embodiments disclosed above may be combined in different ways to form additional embodiments, all of which are within the scope of the present disclosure. Also, it should be understood that the separation of various system components in the above-described implementations should not be understood to require such separation in all implementations, and that the components and systems described may generally be integrated together in a single product or packaged in multiple products.

[0083] For purposes of this disclosure, certain aspects, advantages, and novel features have been described herein. Not all such advantages may necessarily be achieved in accordance with any particular embodiment. Thus, for example, one skilled in the art will recognize that the present disclosure may be embodied or performed to achieve one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.

[0084] Conditional language, such as "can, could," "might," "may," and the like, unless expressly stated otherwise or understood otherwise within the context in which it is used, is generally intended to convey that certain embodiments include certain features, elements, and / or steps, while other embodiments do not. Thus, such conditional language is generally not intended to imply that the features, elements, and / or steps are somehow required in one or more embodiments, or that one or more embodiments necessarily include logic for determining whether those features, elements, and / or steps should be included in or performed in any particular embodiment, with or without user input or prompting.

[0085] Conjunctions such as the phrase "at least one of X, Y, and Z," unless otherwise noted, are understood in the context in which they are generally used to convey that an item, term, etc. may be either X, Y, or Z. Thus, such conjunctive language is generally not intended to imply that a particular embodiment requires the presence of at least one of X, at least one of Y, and at least one of Z.

[0086] As used herein, language of degree, such as "approximately," "about," "generally," and "substantially," refers to a value, amount, or characteristic that is close to a stated value, amount, or characteristic that still performs a desired function or achieves a desired result. For example, the terms "approximately," "about," "generally," and "substantially" can refer to amounts that are less than 10%, less than 5%, less than 1%, less than 0.1%, and less than 0.01% of a stated amount. As another example, in certain embodiments, the terms "generally" and "substantially parallel" refer to values, amounts, or characteristics that deviate from exact parallelism by no more than 15 degrees, 10 degrees, 5 degrees, 3 degrees, 1 degree, or 0.1 degrees.

[0087] The scope of the present disclosure is not intended to be limited by the specific disclosure of preferred embodiments in this section or elsewhere herein, but may be defined by the claims, as presented in this section or elsewhere herein, or as presented in the future. The language of the claims should be interpreted broadly based on the language used in the claims, and not limited to the examples described herein or during the prosecution of this application, and the examples should be interpreted as non-exclusive.

[0088] It is understood that the above description is directed to specific features, aspects and advantages of the invention, and that various changes and modifications can be made without departing from the spirit and scope of the invention. Moreover, the devices described herein need not feature all of the objects, advantages, features and aspects described above. Thus, for example, one skilled in the art will recognize that the invention may be embodied or performed to achieve or optimize one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein. Moreover, while many variations of the invention have been shown and described in detail, other modifications and methods of use that are within the scope of the invention will be readily apparent to those skilled in the art based on this disclosure. It is also contemplated that various combinations or subcombinations of the specific features and aspects of the embodiments can be made and still fall within the scope of the invention. Thus, it is to be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another to form various modes of the disclosed devices.

Claims

1. A system configured to generate electricity or hydrogen from natural gas and to be connected to a gas main and a local gas distribution pipe, a thermal energy storage unit containing a thermal energy storage material and configured to receive energy from an energy source to heat the thermal energy storage material; a heat exchanger in fluid communication with the thermal energy storage unit and configured to receive a natural gas flow from the gas main and to receive a heating fluid from the thermal energy storage unit for heating the natural gas flow; an expander in fluid communication with the heat exchanger and configured to receive a heated natural gas stream from the heat exchanger and expand and cool the heated natural gas stream to reduce its pressure; a generator connected to the expander and configured to generate electricity from expansion of the heated natural gas stream through the expander.

2. The system of claim 1 , wherein the thermal energy storage unit, the heat exchanger, the expander, and the generator are part of a stand-alone portable unit.

3. The system of claim 1 or 2, wherein the energy source is a renewable energy source.

4. The system according to any one of claims 1 to 3, wherein the energy source is a solar power plant.

5. The system according to any one of claims 1 to 3, wherein the energy source is a concentrated solar power plant.

6. The system of any one of claims 1 to 3, wherein the energy source is a power grid.

7. The system of any one of claims 1 to 6, wherein the thermal energy storage material is water.

8. The system of any preceding claim, wherein the thermal energy storage material comprises pressurized water.

9. The system of any preceding claim, wherein the thermal energy storage material comprises a solid material.

10. 10. The system of claim 1, 2, 3, 4, 5, 6, and 9, wherein the thermal energy storage material comprises rock.

11. 11. The system of claim 1, 2, 3, 4, 5, 6, 9, and 10, wherein the thermal energy storage material comprises filler gravel.

12. The system according to any one of claims 1 to 11, wherein the expander includes a first expander and a second expander.

13. The system of any one of claims 1 to 12, wherein the heat exchanger includes a first heat exchanger between the gas main and a first expander, and a second heat exchanger between the first expander and a second expander.

14. The system of any one of claims 1 to 13, further comprising an electrolyser configured to receive electricity generated from the generator and generate hydrogen.

15. The system of claim 14 , wherein the generated hydrogen is injected into the local gas distribution pipe.

16. 15. The system of claim 14, wherein the generated hydrogen is injected into a line separate from the local gas distribution line.

17. The system according to any one of claims 1 to 13, wherein the generated electricity is supplied to a power grid.

18. 1. A method for generating electricity or hydrogen from natural gas, comprising the steps of heating a natural gas stream flowing between a gas main and a local gas distribution pipe via a heat exchanger; expanding the heated natural gas stream received from the heat exchanger through an expander; generating electricity by expansion of the heated natural gas stream through the expander.

19. 20. The method of claim 18, wherein heating the natural gas stream comprises receiving a heating fluid from a thermal energy storage unit in the heat exchanger to heat the natural gas stream.

20. 20. The method of claim 18 or 19, wherein expanding the heated natural gas stream comprises cooling the heated natural gas stream and reducing its pressure.

21. A method according to any of claims 18 to 20, wherein the step of expanding the heated natural gas stream is carried out in multiple stages.

22. The method of any of claims 18 to 21, further comprising generating hydrogen via an electrolyser powered by the generated electricity.

23. 23. The method of claim 22, further comprising injecting the generated hydrogen into the local gas distribution pipe.

24. 23. The method of claim 22, further comprising injecting the generated hydrogen into a line separate from the local gas distribution line.

25. The method of any of claims 18 to 24, further comprising the step of supplying at least a portion of the generated electricity to a power grid.

Images