US20120186252A1

US20120186252A1 - Method of Electricity Distribution Including Grid Energy Storage, Load Leveling, and Recirculating CO2 for Methane Production, and Electricity Generating System

Info

Publication number: US20120186252A1
Application number: US13/400,498
Authority: US
Inventors: Eric Schmidt
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-01-17
Filing date: 2012-02-20
Publication date: 2012-07-26
Also published as: WO2013109581A1

Abstract

A method is provided for generating and distributing electricity via an electrical grid, wherein a fossil fuel plant and a renewable energy electricity generating station are interconnected with the electrical grid and are both operable to generate electricity output. The electricity output is directed from both the fossil fuel plant and the renewable energy electricity generating station to the electrical grid for distribution. Then, at the fossil fuel plant, at least a portion of the electricity output is directed to within the plant and utilized in generating hydrogen. The method provides further a reacting step wherein the generated hydrogen reacts with carbon dioxide to produce methane. Continued operation of the fossil fuel plant is conducted utilizing the produced methane as fuel, to generate electricity output, and also, capturing carbon dioxide exhaust and utilizing it in the reacting step.

Description

FIELD OF THE INVENTION

The present application claims the benefit of U.S. Provisional Application Ser. No. 61/587,548, filed on Jan. 17, 2012 (pending), which disclosure is hereby incorporated by reference for all purposes and made a part of the present disclosure.
The present invention relates generally to a system and method for generating electricity and, further, distributing electricity to consumers via an electrical grid. The present invention also relates to a system and method of reducing potentially harmful exhaust or byproduct (e.g. carbon dioxide exhaust) of an electric generating system. The present invention also relates generally to a system and method for operating a fossil fuel plant utilizing an alternative fuel to fossil fuel and further, to a system and method for generating and distributing electricity, whereby both a fossil fuel plant and a renewable energy electricity generating station are operated (with the latter being utilized at increased frequency).

BACKGROUND OF THE INVENTION

Electricity is generated in large-scale at various types of power plants through the conversion of energy resources. The more common modes of energy conversion include the combustion of hydrocarbon fuels and secondly, nuclear fission. Electricity is also generated through conversion of renewable energy resources such as hydro, geothermal, biomass, solar, and wind. With about 800,000 MWe of installed capacity, the electric power system in the United States is the largest in the world. A large majority of the electricity generated come from fossil fuel plants, primarily natural gas and coal-fired plants. These energy sources account for over two-thirds of all electricity generated in the United States. Nuclear power plants contribute about 20% to the total generated, while hydroelectric facilities contribute about 7%.
The mix of resources utilized in power generation varies over time, depending on market factors as well as public policy. For example, environmental concerns and government regulations addressing these concerns provide a strong motivation for moving away from coal-fired power plants and toward utilization of cleaner burning fuel such as natural gas. In the past, nuclear power was promoted worldwide by many as a cleaner and more efficient energy alternative, but safety concerns and construction difficulties have slowed the commissioning of new nuclear power plants in the United States. Many agree that, with worldwide electricity demand projected to increase by 50% by year 2025, increasing the world's capacity of electricity generation is an inevitability that must be balanced by environmental and safety concerns as well as economic and political interests. Further development and incorporation of renewable energy resources can help strike this balance.
Renewable energy is energy derived from natural resources that are naturally replenished. The systems and methods of the present invention are particularly applicable to the operation of renewable energy electricity generating stations such as wind turbine farms. Unlike fossil fuels, wind as an energy source is kinetic energy in its natural state. At present, wind power is harvested more cost effectively than any other renewable energy resource except hydroelectric power. The cost of generating wind power is roughly one-third (per megawatt hour) of that for solar power. According to a 2011 report by Vestas Inc., the power needs of 100% of the American homes could be met by operating a 120 square mile wind farm off the coast of the north-eastern seaboard. Wind power is fickle, however, and as such, wind farm-generated electricity is not always available. To be commercially available, a state of the art wind farm requires a minimum average wind speed of 6.5 m/s at the site. Wind turbines begin to produce at about 4 m/s of wind speed, but reach maximum power at about 10-12 m/s. Engineering design and economics currently do not allow wind turbines to exploit wind energy beyond the 10-12 m/s limit. With this and other types of design restrictions, most commercially viable wind farms in the United States produce some energy only about 80% of the time and, even then, the most productive of these wind sites produce at or near full capacity somewhere between 20% to 50% of the time.
Furthermore, even if wind power is available for production, it is not always utilized by the electric grid. As with all renewable energy electricity sources, wind farm output is often declined by the utility (i.e., curtailed). In many cases, the utility elects not to throttle down its fossil fuel production, in favor of wind farm production, because the traditional fossil fuel plant cannot readily increase production to meet a sudden grid demand. Such a sudden grid demand can, of course, be caused by a sudden decrease in wind availability to a wind farm. In the case of solar power, a sudden change in weather conditions may cause an interruption in output and a corresponding loss of capacity in the grid. A traditional fossil fuel plant in a state of reduced operating cycle may not be able to ramp up in time to cover the shortfall.

SUMMARY OF THE INVENTION

The present invention is directed generally to a system and method for generating electricity and, more particularly, distributing electricity to consumers via an electrical grid. The present invention is also directed to a system and method of reducing, if not eliminating, certain potentially harmful byproducts of an electric generating system, such as carbon dioxide exhaust of a fossil fuel electric generating plant. In the alternative, the invention provides a system and method for operating a fossil fuel plant utilizing an alternative fuel to fossil fuel and further, to a system and method for generating and distributing electricity, whereby both a fossil-fuel plant and a renewable energy electricity generating station are operated (with the latter being utilized at increased frequency).
In one aspect of the invention, a method is provided for generating electricity for distribution via an electrical grid, wherein a fossil fuel plant is interconnected with the electrical grid and incorporates a turbine and an electric generator operable to output electricity to the grid. At the fossil fuel plant, a Rankine cycle is employed to drive the turbine and electric generator to generate electricity. This includes burning a fossil fuel to generate heat and transferring the generated heat to a working fluid of the Rankine cycle. Hydrogen is provided at the fossil fuel plant and an alternative fuel to the fossil fuel is provided or produced by utilizing chemical energy in the hydrogen. The alternative fuel is burned to generate heat and the heat generated is transferred for use in the Rankine cycle. Thereafter, the method entails continuing to employ the Rankine cycle to drive the turbine and electric generator to output electricity to the electrical grid.
In another aspect of the invention, a method is provided for generating and distributing electricity via an electrical grid. The method entails operating a fossil fuel plant to generate electricity output and directing electricity output to the electrical grid for distribution. At the fossil fuel plant, at least a portion of the electricity output may be directed to within the plant (e.g., re-circulated). Also, at the fossil fuel plant, hydrogen is generated utilizing the electricity directed within the plant. Chemical energy in the hydrogen is utilized to provide an alternative fuel for the fossil fuel plant. In one embodiment, the method provides for reacting the generated hydrogen with carbon dioxide to produce methane as the alternative fuel. At this point, the step of operating the fossil fuel plant is continued utilizing the alternative fuel as fuel for a furnace of the fossil fuel plant, to generate electricity output. In another embodiment, the method entails combustion of the generated hydrogen in the furnace (as the alternative fuel), to generate electricity output.
In another aspect, a method is provided for generating and distributing electricity via an electrical grid. This method entails operating both a fossil fuel plant and a renewable energy electricity generating station (e.g., wind farm, solar power station) to generate electricity output. Electricity output is directed from each of the fossil fuel plant and the renewable energy electricity generating station to the electrical grid for distribution. At the fossil fuel plant, at least a portion of the electricity output is directed to within the plant and hydrogen is generated utilizing the electricity directed. Then, the generated hydrogen is reacted with carbon dioxide to produce methane, and the fossil fuel plant is continued to be operated utilizing the produced methane as fuel, to generate electricity output. Preferably, the method also involves such a reacting step, wherein carbon dioxide is exhausted and the carbon dioxide exhaust is captured and directed to the reacting step, whereby the captured dioxide is reacted with hydrogen.
In yet another aspect of the invention, a system is provided for generating electricity for distribution via an electrical grid. The system includes a fossil fuel plant interconnected with, and configured to, direct electricity output to the electrical grid, the fossil fuel plant being further configured to operate a Rankine cycle to drive a steam turbine and electric generator. The fossil fuel plant includes: a furnace for burning fuel to generate heat; a hydrogen generator for generating hydrogen; a reactor for reacting hydrogen and carbon dioxide to produce methane; a recirculating loop interconnecting the furnace and the reactor including a line for directing methane produced by the reactor to an inlet of the furnace and a line directing carbon dioxide captured from the exhaust of the furnace to the hydrogen generator, wherein the furnace is operable to burn fossil fuel and methane; and power transmission means for directing electricity output of the electric generator to the hydrogen generator. The system also includes electricity output transmission means for directing electricity output to the electrical grid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a simplified representation of a system for generating electricity and distributing same to consumers;

FIG. 1B is a simplified representation of the system in FIG. 1A modified to incorporate a wind turbine farm as an alternate electric generating system;

FIG. 2 is a simplified representation of an electric generating system, according to the present invention;

FIG. 3 is an alternative embodiment of the electric generating system in FIG. 3, according to the present invention; FIG. 4 is yet another embodiment of the electric generating system of FIG. 2, according to the present invention;

FIG. 5 is a simplified schematic of yet another embodiment of a system and method for generating electricity according to the present invention;

FIG. 6A is a simplified flow chart illustration of a method of generating electricity, according to one embodiment of the present invention;

FIG. 6B is a simplified flow diagram illustrating sub-processes in an exemplary method of generating electricity, according to the present invention;

FIG. 7 is a simplified flow chart illustration of a method of generating and distributing electricity, according to one embodiment of the present invention;

FIG. 8 are graphical representations of modes of electricity generating operations during a typical 24-hour period including operation of a system according to the invention;

FIG. 9A is a simplified representation of an electric generating system according to an alternative embodiment according to the present invention; and

FIG. 9B is a simplified representation of an electric generating system according to yet another alternative embodiment according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1A is a simplified representation of an electric generating system 10. The electric generating system 10 includes a fossil fuel electric generating plant 20 (or “fossil fuel plant”) that generates electricity by burning a fossil fuel such as natural gas, coal, fuel oil, or other suitable and available fuels. As described in the present disclosure, the electric generating system 10 also provides for the transmission of the generated electricity to commercial and residential consumers. The electric generating system 10 is, therefore, described as including transmission lines 40 and an electrical grid 50 connected to the fossil fuel plant 20 by the transmission lines 40. Further, the electrical grid 50 is interconnected with commercial and residential consumers as well as wholesale consumers that operate local distribution networks. As sometimes used herein for purposes of describing certain aspects of the invention, the term electric generating system 10 may include the transmission lines 40 and the electrical grid 50. The term electrical grid 50 refers to all or a distinct part of a network of transmission lines, substations, and local distribution networks, which allow for the movement and regulation of electricity between the various physical nodes in the network as well as the various commercial, residential, and wholesale consumers connected to the grid 40. It is also noted, however, that a not so uncommon use of the term electrical grid 50 may encompass a larger network that includes one or more electric generating plants. The present description of the invention will make clear that certain aspects of the invention is directed to the interaction and interconnection between one or more electric generating plants or electricity sources, one or more ultimate consumers and/or the “electrical grid” with which the consumers are interconnected. In this respect, the electric generating system 10 according to the invention refers to the electricity generating source(s) and the network that facilitates delivery of electricity to the consumer(s), which network is usually defined for present purposes of description as the electrical grid 50. The electrical grid 50 also facilitates transmission of electricity between electricity generating sources (e.g., a fossil fuel plant and a wind turbine farm as further described below), but it is conceivable that the two electricity sources may be substantially physically remote from each other and yet still directly connected. In such a case, if the electricity generating sources are interconnected with, and can deliver electricity to, the consumer via the electrical grid, the two electricity generating sources are still described for present purposes as being mutually connected via the electrical grid.
Referring now to FIG. 1A, the fossil fuel plant 20 generally operates to convert chemical energy stored in fossil fuel into thermal energy (heat), then mechanical energy, and then electrical energy (electricity). Common fossil fuels include non-renewable sources such as fuel oil, coal and natural gas. The electric generating plant 20 includes a large scale, on-site fuel supply 22 for storing or receiving the fossil fuel. Fossil fuel (FF) is conveyed from the fuel supply to a combustor or furnace 24, under conditions that promote complete combustion of the fuel. In a coal-fired plant, for example, pulverized coal may be conveyed from coal storage and air-blown into the furnace 24 by air nozzles, wherein it mixes with an oxidant (i.e., air). The fine coal mixture may be ignited thereby effecting a combustion reaction, which releases chemical energy in the form of heat energy (H_T). The fossil fuel plant 20 then utilizes the heat generated in a closed loop Rankine cycle to operate a prime mover, typically in the form of rotating machinery such as a steam turbine and electric generator combination. For most industrial power applications, the working fluid used in the Rankine cycle is water, which, as known in the art, is cycled between liquid and water vapor phases. The Rankine cycle is, therefore, sometimes referred to herein as a “steam power plant cycle” or “steam cycle.”
As represented in FIG. 1A, heat (H_T) generated in the furnace 24 is supplied to a closed loop thermodynamic process (R) employing water as the working fluid. The boiler 26 is, therefore, logically positioned near the furnace 24 so that the heat generated in the furnace can readily transfer, primarily by way of thermal radiation, to water circulating in the boiler 26. In the boiler 26, water is preferably circulated through tubes which run near the periphery and pass heat radiating from the furnace 24. The circulating water absorbs heat sufficient to change water from a liquid phase to a vapor phase, thereby generating steam (S). The steam (S) is separated from the water in the boiler 26, and is often conveyed and superheated in additional tubes before exiting the boiler 26. The superheated, high-pressure steam (S) is then directed to a steam turbine 28, which may actually comprise a series of turbines on a common shaft. The energy in the steam (S) operates to drive or turn the turbine 28, thereby converting the energy in the steam (S) to mechanical energy (work). As the steam (S) moves through the series of turbines, it loses heat and pressure and expands, before exiting at the turbine exhaust. Ultimately, the steam condenses completely, returning to water (W₁) in the liquid phase and then returned to the boiler 26. This re-circulated water (W₁) again travels through the boiler tubes, wherein it is turned into steam, before being directed back to the steam turbine.
The rotating steam turbine 28 is connected to a rotatable electric generator 30 and, as such, the mechanical energy of the steam turbine 28 rotates the electric generator 30. The rotating electric generator 30 produces electrical energy or electricity in the form of three-phase alternating current, which is the output of the electric generating plant 20. Typically, the alternating current is directed from the electric generator 30 to a transmission substation at the plant 20, where large transformers convert the generator voltage to a high voltage suitable for long-distance transmission. The alternating current is then transmitted over high-voltage transmission lines 40 across the electrical grid 50 to the target locations and target consumers. At certain points, the high-voltage transmission lines lead to power substations that employ transformers to step down the high voltage to a lower voltage more suitable for distribution to the end consumers.
As described above, and for purposes of describing aspects of the present invention, the fossil fuel plant 20 may be described as operating a Rankine or steam cycle to drive a turbine—generator combination and generate electricity, or in the alternative, to convert heat energy into mechanical energy and directing the mechanical energy to operate the electric generator 30, thereby generating electricity. The fossil fuel plant 20 may also be described as utilizing or operating a boiler 26 and rotating machinery preferably in the form of a steam turbine 28 to operate the steam cycle and/or to convert heat energy into mechanical energy, and further, to operate the electric generator 30, thereby generating electricity. The above description is provided in general and exemplary terms for present purposes. It should be understood, particularly to one skilled in the engineering or other relevant art, that different aspects of the invention are applicable to fossil fuel plants of more detailed and/or varied design, including those employing different but thermodynamically equivalent mechanical elements in the power generation method.
The more common fossil fuels are hydrocarbons that contain hydrogen and carbon. During combustion, hydrogen and carbon combine and react with oxygen in air to produce carbon dioxide and water vapor and other gases (pollutants). Thus, the burning of the fossil fuel supply not only generates heat, but produces and then exhausts hot carbon dioxide into the atmosphere. This chemical reaction may be represented as follows:
CH₄+O₂→CO₂+H ₂0+Energy (Heat) (1)
As shown in FIG. 1A, the furnace 24 and, more generally, the fossil fuel plant 20 exhausts unwanted carbon dioxide (CO₂) (and other pollutants) as a byproduct of the combustion process. The carbon dioxide exhaust is considered a greenhouse gas and one of the contributors to the “greenhouse effect.” When present in the atmosphere, carbon dioxide gas tends to absorb and emit radiation in the thermal infrared range. In addition to the carbon dioxide gases, the burning of various common fossil fuels may emit fly ash and other exhaust gases. The typical exhaust gas may contain nitrogen and such additional combustion products as nitrogen oxide and sulfur dioxide. Although the fossil fuel plant may employ means, including scrubbers and catalysts, to reduce the presence of contaminants in the plant's exhaust before release, the flue gas from a fossil fuel plant will normally contain some amount of each of the above-mentioned pollutants. When pollutants emitted by the plant exceed certain levels, the plant may be fined or even shut down.
In one aspect and objective of the present invention, a system and process is provided that will reduce, if not eliminate, the exhaust of carbon dioxide from the electric generating plant 20 into the atmosphere. In a further aspect of the invention, a system and process is described in which carbon dioxide produced from combustion in the furnace is actually utilized in, and as a part of, the supply of fuel to the furnace. In this respect, it may be described that the carbon dioxide is actually recycled by the fossil fuel plant (as fuel for the furnace). Various aspects of the invention may be described as specific systems and processes contained in the electric generating plant 20 or, more generally, systems and processes involving or incorporating an additional or alternate electric generating plants and the electrical grid. In the exemplary embodiments of such general descriptions of the invention, the alternate electric generating plant is preferably an electricity generating station that employs or utilizes a renewable energy source, e.g., wind, solar, etc. These systems for generating electricity present significant advantages over fossil fuel plants primarily because these systems do not exhaust such harmful byproducts as carbon dioxide emissions and other pollutants. These alternate systems are considered cleaner and also safer alternatives to most fossil fuel plants. These systems are also preferred because of their use of a renewable energy resource (e.g., wind, solar), rather than depleting a more finite resource such as fossil fuel.
Referring now to FIG. 1B, a common electricity generating station connected to the electrical grid 50 is the wind turbine farm or simply, wind farm 52. Wind farms typically comprise a collection of individual wind turbines strategically clustered in a region with consistent non-turbulent wind flow. Individual turbines are interconnected with a power collection system and medium—voltage transmission network. These are usually further connected to a substation that steps up the medium-voltage electrical current to high voltage. From the substation, the wind farm generated electricity is distributed along high-voltage transmission lines to the rest of the grid. The larger onshore wind farms in the United States typically have capacities in the range of 500 MW to about 750 MW. In total, wind power installed capacity in the United States now exceeds 43,000 MW and supplies over 3% of the total electricity usage.
Referring again to FIG. 1B, the electrical grid 50 generally receives all of the electricity generated by the fossil fuel electric generating plant 20 during normal usage. Typically, the fossil fuel plant 20 will gradually ramp up output to meet (and exceed) increasing demand or, more appropriately, an expected rise in demand. Because it can directly control power generation by the fossil fuel plant 20 and maintain the plant's power output once ramped up, the utility (or system or fossil fuel plant operator) prefers operating the fossil fuel plant at and even slightly above whatever capacity is required or expected by the electrical grid. This prevents any short fall in the electric grid's capacity and ensures that consumer demand will be met at almost all times. The wind farm's capacity and consistency are, on the other hand, generally dependent on the availability of wind power as well as the physical limitations of the wind farm itself. Accordingly, reliance and priority are generally placed on the fossil fuel plant's electric generating capacity.
In between peak loading and a low point in demand (usually at night), the fossil fuel plant 20 requires time to gradually ramp down. During this period, all of the electricity generated by the fossil fuel plant 20 is delivered to the grid 50, even though the combined capacity of the wind farm 52 and the fossil fuel plant 20 may exceed the consumer demand of the grid 50. Moreover, during low demand periods, the utility or system operator prefers to operate the electric generating plant 20 at some capacity above grid demand and not too far below a demand level that might be expected should there be a sudden spike. As discussed previously, fossil fuel plants are not very responsive to fluctuations and thus, a plant must also generate such excess electricity to readily accommodate unexpected increases in grid demand or use very expensive peaking turbines. During such periods, electricity generated, or which could be generated, by the wind farm 52 is rarely used.
With the conventional system such as the system 50 of FIG. 1B, utilities or system operators can practice a method of load balancing in which operation and output from both the /fossil fuel plant and the wind farm is managed together to consistently meet changing grid demand. In this context, the wind farm could be operated to supplement the capacity of the electrical grid and perhaps, relieve some of the burden on the fossil fuel plant. If the wind farm increases its output (e.g., due to increased wind availability) the utility can recognize the electricity output of the wind farm and reduce its fossil fuel plant production. Utilities are, however, reluctant in accepting electricity from such renewable energy sources on the grid due to the inconsistency of these sources as power generators. Prevailing winds may suddenly drop or a cloud cover may unexpectedly form, thereby causing a corresponding reduction in grid capacity that the utility must, just as quickly, replenish. A typical Rankine steam turbine (by far, the most common thermodynamic cycle used to generate electricity) cannot change its power setting very quickly, however. A utility can “step on the gas” to increase power in the furnace of a steam turbine, but the power plant does not generate additional output instantaneously as a result. There is a lag. Further, cycling the temperatures of the steam more quickly is not practical as this puts thermal stresses on the steam pipes and can lead to cracks and premature failures.
Thus, the utility risks falling short of meeting grid demand if it elects to throttle down the fossil fuel plant in favor of recognizing the increased electricity output from the wind farm. Accordingly, utilization of these alternate electricity generating stations are usually restricted to periods of peak demand and periods in which, historically, production from these energy sources have proven to be consistent. For example, solar or wind farm output may be used to satisfy peak demand during the middle of the day in the summer, when electric wholesale rates are at their highest. Output from a particular wind farm may be relied on, in another example, during certain periods in April when winds in the area of the wind farm have been shown to prevail 90% of the time between the hours of 6 p.m. and 10 p.m.
Even in the above-mentioned periods of consistently available wind or solar power, the utility often elects not to utilize some or all of the seemingly available capacity in the system. Because of the practical limitations on how fast the traditional fossil fuel plant can ramp up, plants are discouraged from throttling down at any time, in favor of additional output from renewable energy electricity generating stations or otherwise. In fact, utilization of additional electricity output from a wind farm or solar power station may be prompted only by the utility's need to fulfill its requirement for minimum renewable energy usage. In such case, the fossil fuel plant may still operate near normal (instead of throttling down) and generate electricity. The plant operates in a “spinning reserve” mode, however, in which the excess output is not utilized by the grid and from which electricity output can be readily directed back to the grid should the need arise. In this load balancing response mode, fossil fuel is sacrificed by the plant.
Applicant submits that, ideally, all or substantially all of the electricity generated by the wind farm 52 should be utilized whenever available. One of the primary advantages to favoring wind farm-generated electricity is, of course, the reduction in emissions from operating the fossil fuel plant, namely carbon dioxide and other pollutants. Also, reduction in the operation of the fossil fuel plant necessarily translates to a desirable reduction in the need and consumption of the fossil fuel, i.e., coal, fuel oil, or natural gas. In one aspect of the invention, a system and method is provided for integrating, utilizing, and/or optimizing electricity generated by cleaner, alternative sources of electricity while reducing the dependence on fossil fuel plant electricity generation. Further, in another aspect of the invention, a system and method is provided for reducing the byproducts of fossil fuel electricity generation. More particularly, such a system and method is provided in which the exhaust of carbon dioxide from fossil fuel electricity generation is substantially reduced.
In accordance with a further aspect of the present invention, the supply and consumption of fossil fuel in the traditional fossil fuel electricity generating plant is modified to incorporate the utilization of an alternate or supplemental fuel. Preferably, the electricity generating process is modified to reduce, if not eliminate, the exhaust of carbon dioxide (and other potential pollutants). More preferably, a system and process is provided in which the carbon dioxide exhaust is not only reduced but utilized in the production of an alternate or supplemental fuel for the fossil fuel plant. This supplemental fuel is also burned in the furnace 24 to generate heat for the boiler 26.
As a foundation and basis to many of the inventive aspects of the invention, Applicant recognizes that, in the traditional process of burning fossil fuels to generate heat, the process does not so much rely on burning oil, natural gas, coal, or other fuel, but on the burning of the hydrogen contained in the fossil fuel. Moreover, it is not the hydrogen component, but the other combustion reactants and elements that produce undesirable byproducts.
One kg of hydrogen has three times the energy density by weight as gasoline. The energy density of hydrogen by volume is, however, substantially less (on the order of several thousands) than that of gasoline (and other fossil fuels). In fact, hydrogen must be compressed to 5000 psi to have a comparable volumetric density as gasoline. This and other physical properties of hydrogen make its transport and storage in both liquid and gas forms problematic, and thus, its availability as a direct energy source for the electricity generating plant especially challenging. The present invention elects to store, supply, and use hydrogen in compound form, and more preferably, on-site at the fossil fuel plant. The compound is supplied to the furnace, thereby making energy carried by the hydrogen in the compound available to the electricity generating plant.
The present invention introduces, therefore, a means for storing, and making available, hydrogen for use as an energy source for an electricity generating process. Further, in one aspect of the invention, a system and process is provided wherein such a hydrogen compound is made available as an alternate or supplemental fuel source to a fossil fuel plant (such as the plant described in respect to FIGS. 1A, 1B). In accordance with the invention and in this context, the system and process also provides for generating that hydrogen compound and fuel source, wherein and whereby undesirable carbon dioxide is captured and recycled (consumed). Preferably, the source of carbon dioxide is unwanted carbon dioxide exhaust from the fossil fuel plant, specifically the exhaust of the combustion process that generates the heat required for the steam cycle. Thus, in accordance with the invention, hydrogen and carbon dioxide are used to produce methane, CH₄, and this methane is used as the alternate or supplemental fuel source of the fossil fuel plant. The reaction implemented at the fossil fuel plant to produce the methane is represented by the following equation:
CO₂+4H₂→CH₄+2H₂O (2)
In other words, the fossil fuel plant's unwanted exhaust is consumed and used to produce highly desirable methane gas as fuel for the fossil fuel plant. In so doing, the inventive system and process also achieves reduction, if not elimination, of the fossil fuel plant's harmful carbon dioxide exhaust.
The term “alternate” as used herein to describe the produced methane as a source of fuel for the furnace shall apply whether the methane is used exclusively as the fuel source or in conjunction with the traditional fossil fuel supply. Thus, the methane may be used in addition or supplemental to the traditional fossil fuel with the fossil fuel at any one time or in certain durations. The methane may be consumed at the same time as the fossil fuel or substitute for the fossil in discrete durations. In any case, the methane is referred to as being an “alternate” to using the traditional fossil fuel supply exclusively at any given time or for given durations.
As carbon dioxide is plentiful in the exhaust of the traditional fossil fuel plant, utilizing this carbon dioxide instead of simply exhausting it positively addresses an emission problem of the traditional plant. This may also reduce the expense and use of plant equipment to treat the exhaust prior to release. A reduction in plant emissions may, in many instances and for many plants, can also translate directly and indirectly to cost savings from reduced fees, taxes, and fines levied against the plant and the community.
Methane may be produced as a fuel supply from the above reaction provided that stable hydrogen can be delivered consistently and practically. Preferably, the hydrogen is generated locally or on-site, and consistent primary supply is available to the plant. As the generation of hydrogen requires energy input, the inventive system and process must locate energy (or electricity) to address this input. In one aspect of the invention, the system and process provides a means for directing “excess” electricity for this purpose, from the grid 50 or from the output of the fossil fuel plant 20, without compromising but, in another respect, enhancing, the electrical grid's capacity to meet consumer demand (but rather, enhancing it). The system and process may also achieve increased utilization (e.g., 100% utilization of grid-compliant renewable electricity) of a renewable electricity source on the grid 50 over the consumption of fossil fuel.
An exemplary system 110 of generating and distributing electricity is illustrated schematically in FIG. 2. FIG. 2 may also be used to illustrate the method of generating and distributing electricity according to the invention. The preferred system 110 includes a traditional fossil fuel plant 120, with modifications to accommodate both a means 162 for reacting hydrogen and carbon dioxide to produce methane and a means 160 for generating hydrogen to supply the reacting means, as will be further described below. The preferred system and process also provides a means 164 for directing and supplying electricity 158 to accommodate the power needs of hydrogen generation.
The system 110 is further described for present purposes as including an electrical grid 150 for distributing electricity to consumers, including residential, commercial, and wholesale consumers, a fossil fuel electricity generating plant 120 interconnected with the electrical grid 150 and an alternate or secondary electricity generating source or station152 that is also interconnected with the electrical grid 150. As suggested above, the alternate electricity generating station 152 is preferably a renewable energy power generation station such as a wind farm 152, a solar thermal station, a geothermal plant, or other. In the exemplary system 110 depicted in FIG. 2, a traditional wind farm 152 is shown interconnected with the electrical grid 150. In other embodiments, multiple alternate electricity generating stations of one or more varieties may be interconnected with the electrical grid 150 and fossil fuel plant 120, and operated therewith in accordance with an exemplary method of the invention.
In describing the systems and method of the invention, each of the wind farm 152 and other renewable energy electricity generation stations configured in combination with the fossil fuel plant 120 and the electrical grid 150 is referred to as an “alternate” electricity generating system or station. The use of the term is employed for convenience and reference and should not be construed as limiting the system and in particular, the operation of the system, according to the invention. For example, the capacity of most fossil fuel plants today substantially exceeds that of wind farms, geothermal plants, and solar power plants, and thus, operation of such fossil fuel plants could be reasonably construed as being primary relative to operation of a smaller “alternate” plant. It is contemplated, however, that the capacity and capability of future alternate electricity generating stations, individually or collectively as a cluster, could become comparable to those of traditional fossil fuel plants. Moreover, in some stages of operation according to the invention, the preference remains 100% utilization of the output capacity of “alternate” electricity generating stations over the traditional fossil fuel plants.
The plant 120 depicted in FIG. 2 is a modified version of the fossil fuel plant 20 shown in FIG. 1. As described previously, the fossil fuel plant 120 includes a fossil fuel supply 122, a furnace 124 to which the fossil fuel supply 122 conveys fossil fuel, a boiler 126 operatively positioned adjacent the furnace 124, a steam turbine 128 interconnected with the boiler 126, and a rotary electric generator 130 mechanically interconnected with the turbine 128. As shown, the output of the electric generator 130 is conveyable to the electrical grid 150 via transmission lines 140, in a manner similar to how the wind farm 152 is also interconnected with the electrical grid 150. As also described previously, the fossil fuel plant 120 employs a Rankine cycle in transferring heat generated in the furnace 124 during combustion to the boiler 124 and utilizing this energy to drive the turbine 128 and, ultimately, the electric generator 130. In this preferred embodiment, water is the working fluid in a steam cycle and the turbine 128 is a multi-stage steam turbine 128.
In accordance with one embodiment of the present invention, the system and process now includes means 164 for directing some or all of the output of the electric generator 130 (and thus, the output of the fossil fuel plant 120) to a destination within the fossil fuel plant 120. Preferably, the output is interconnected with the means 160 for generating hydrogen, which is in the form of a hydrogen generator 160. Further, the hydrogen generator 160 is interconnected with the means 162 for reacting hydrogen and carbon dioxide to produce methane, which is preferably provided by a Sabatier-type reactor 162. As indicated in FIG. 2, the hydrogen generator 160 and the Sabatier reactor 162 are located locally and within the fossil fuel plant 120. Such directing means 164 may, therefore, include such electrical power components as transmission lines, substations, and transformers as required to transmit some or all of the alternating current output of the electric generator 130 to the physical location of the hydrogen generator 160 within the plant 120 and in a state suitable for use by the hydrogen generator 160. In some applications, the power supply 158 to the hydrogen generator 160 may require conversion of the alternating output to a direct current supply.
The hydrogen generator 160 is configured to receive and/or draw electricity on an inlet side from the power supply 158. On an output side, the hydrogen generator 160 connects to the inlet of the reactor 162. The furnace 124 and reactor 162 are preferably configured and operatively interconnected to form a fuel-carbon dioxide exhaust recirculation loop 166. The reactor 162 can draw hydrogen supply (H₂) directly from the hydrogen generator 160. The inlet of the reactor 162 is also connected with, and draws hot carbon dioxide supply (CO₂) directly from the exhaust of the furnace 124. Preferably, the reactor 162 is physically located at the plant 120 and near the furnace 124, and the carbon dioxide supply (CO₂) drawn by the reactor 162 is at a temperature between about 450° F. to about 700° F. The output of the reactor 162 is connected with and is directed to the input of the furnace 124. As provided in the earlier fossil fuel plant arrangement, the furnace 124 receives fossil fuel (FF) on an inlet side, which may be fuel oil, natural gas, or coal conveyed directly on demand from the fossil fuel supply 122. The furnace 124 utilized in the preferred embodiment can selectively receive such fossil fuel (FF) from the fossil fuel supply 122, or, partially or entirely receive its fuel from the output of the reactor 162 in the form of methane. In a system wherein the fossil fuel is natural gas supplied by an inlet pipe, a supply line for methane gas from the reactor 162 may be readily integrated and regulated with the fossil fuel supply.
On the output side of the furnace, the furnace 124 still exhausts hot carbon dioxide as well as other exhaust gases. The preferred embodiment provides, however, a furnace—reactor connection 174 that allows for selective diversion of the hot carbon dioxide gases from the furnace exhaust to the inlet of the reactor 162. Advantageously, the carbon dioxide exhaust will be at or about a temperature preferable for input to the reactor 162, which eliminates significant pre-heating or processing before mixing with hydrogen and consumption by the reactor 162.
A suitable on-site, commercial-scale hydrogen generator 160 is a self-contained device or subsystem for generating hydrogen through either electrolysis of water or the reformation or extraction of another hydrogen-rich chemical (e.g., HTGR or sulfer-iodine or similar cycle). In water electrolysis, water molecules are split into hydrogen (H₂) and oxygen (O₂) through application of electricity:
H₂O+electricity→H₂+1/2O₂ (3)
One suitable hydrogen generator is one of several known self-contained devices for initiating an electro-chemical reaction that yields free hydrogen as described below. For example, hydrogen may be generated through a process of steam reforming, wherein methane and water vapor are converted into hydrogen and carbon monoxide:
CH₄+H₂O+Heat→3H₂+CO (4)
In the exemplary embodiments described herein, the hydrogen generator 160 preferably employs re-cycled electricity to initiate or power electrolysis of water. Such a DC power supply 158 is represented in FIG. 2 as being interconnected with the output of the electric generator 130. Suitable hydrogen generators are readily available to one skilled in the relevant art and include that described in US Pat. App. Publ. 2004/020914 A1 (Oct. 14, 2004), which is hereby incorporate by reference.
The chemical reaction that occurs in the reactor 162 is an exothermic one described by the following equation:
CO₂+4H₂→CH₄+2H₂O (5)
In a preferred embodiment, the reactor 162 is of a Sabatier-type as also described in US Pat. App. Publ. 2004/020914 A1 (Oct. 14, 2004), which is hereby incorporated by reference. The Sabatier-type reactor 162 is basically a large catalytic converter. It is a flow-through device with two inlets, one outlet, and a drain for any condensed water. Typically, a collection of reactor plates or beds made of such materials as nickel, alumina, and, possibly, ruthenium are situated within the reactor. A first inlet receives hot carbon dioxide from the furnace exhaust along with the nitrogen that is normally associated with the carbon dioxide exhaust. A second inlet receives free hydrogen, H₂, from the hydrogen generator. A mixture of these inlet gases is introduced into the reactor tubes and contacts the catalyst situated therein. As the inlet gases pass, an exothermic reaction occurs that produces methane and water. The outlet outputs two gaseous products: methane, CH₄, and nitrogen, N₂(which remains unreacted), plus water, mostly in vapor form. In a typical reactor operation, carbon dioxide and hydrogen gases at 300 to 350 deg C. are induced to flow between the plates at substantial flow rates. A one liter reactor can generally process about 10,0001 of gas/hr. The methane provides, of course, the alternative or supplemental fuel supply for the furnace 124.
The hydrogen generator 160 generally produces hydrogen at a reasonable 77% thermal efficiency at about 24 kW/lb H₂. Thus, the hydrogen generator 160 requires about 48,000 kWh to produce one ton of H₂. One ton of hydrogen can react with the required amount of carbon dioxide to make eight tons of methane. So, at 100% efficiency, 6000 kWh will be required to make a ton of methane or 7500 kWh at 80% efficiency. As discussed previously, in accordance with the present system and process, these power requirements may be met by excess electricity output by the electric generator 130 and/or, as required, electricity output directed from the wind farm 152.
In a variation of the inventive system and process as illustrated in FIG. 3 (wherein like numerals are used to refer to like elements), a traditional fossil fuel plant 220 is further equipped with a hydrogen storage means 266, in the form of pressurized H₂vessels or equal. The hydrogen storage 266 is connected to the outlet of the hydrogen generator 160 and configured to selectively store hydrogen produced by the hydrogen generator 160. The hydrogen storage means 266 is also connected with an inlet of the reactor 162. The reactor 162, hydrogen storage 266, and hydrogen generator 166 are further configured so that the reactor 162 may selectively draw hydrogen from either the hydrogen generator 160 or the hydrogen storage 266, or both.
The configuration of the system 210 and the fossil fuel plant 220 represented in FIG. 3 is particularly suitable for use if or when capacity available from alternative energy sources exceeds consumer demand. In FIG. 3, a system 210 of generating and distributing electricity is shown incorporating a “larger” wind farm 252 available to the electrical grid 150. The wind farm 252 may, of course, be replaced or supplemented by other alternative energy sources. For example, the “larger” wind farm may be replaced by a “larger” solar power station or a combination of wind farms and solar power stations. With electricity supplied to the system 210 exceeding consumer demand, some portion of the electricity delivered by the wind farm 252 is directed to the fossil fuel plant 220 as excess power. At the fossil fuel plant 220, this excess energy is directed to and used for operation of the hydrogen generator 160. In the scenario contemplated, wherein the wind farm 152 generates more electricity than there is demand, there may be no need for the fossil fuel plant 220 to output any additional electricity to the electrical grid 150. The fossil fuel plant may be operated at reduced or minimal capacity (so as to make any subsequent ramp-up easier), as further explained below. Under other circumstances, it may be desirable to substantially reduce operation of the furnace 124, which operation exhausts unwanted carbon dioxide. It may then be preferable to operate the hydrogen generator 160 using the excess electricity, but directing all available hydrogen production to hydrogen storage 266. The stored hydrogen may be used during periods when demand exceeds the capacity of the wind farm 252 to supply electricity, which would typically occur at peak demand periods and periods of sub-capacity wind farm production (e.g., windless periods). In such scenarios, it will usually be preferable to draw from hydrogen storage before commencing use of the fossil fuel supply.
Notably, with consumer demand being met and exceeded by electricity produced by the wind farm 252, the supply of fossil fuel (FF) to the furnace 124 may be substantially reduced or ceased. As shown in FIG. 3, the fossil fuel supply (FF) may be drawn only intermittently or optionally. At such point, nearly 100% of the carbon dioxide exhaust from the furnace 124 may be captured (or retained) by the reactor-furnace loop 166. Furthermore, the process may require more carbon dioxide than is “supplied” by the fossil fuel. In some instances, the plant 120 may temporarily increase supply (FF) and consumption of fossil fuel to boost carbon dioxide in the recirculation loop 266, before returning the fossil fuel supply (FF) to a significantly reduced mode.
FIG. 4 illustrates a simplified schematic of yet a further exemplary embodiment of a system 310 for generating and distributing electricity (whereby like reference numerals are used to refer to like elements). The system 310 preferably employs largely the same components of the fossil fuel plant 220 described in respect to FIG. 3. The system 310 also incorporates a wind farm 152 and an electrical grid 150, as described previously. As shown, the supply of carbon dioxide may be delivered by trucks 370 to the fossil fuel plant 320 and stored in a carbon dioxide storage tank 372 at the plant 320. The carbon dioxide supply may also be delivered by pipeline or other feasible transportation means. In any event, the reactor 162 may draw from the carbon dioxide storage tank 372 for supplemental carbon dioxide required in methane production. As a consumer of carbon dioxide, it is contemplated that the fossil fuel plant 320 will be positioned to commercially transact with traditional carbon dioxide producers. Carbon dioxide is an unwanted byproduct in many plant operations, including chemical plant operations and other fossil fuel plant operations. Carbon dioxide exhaust from these operations is captured and sequestered with increasing frequency in off-site locations (e.g., caverns in South and West Texas and New Mexico). Some operations may capture the carbon dioxide exhaust and choose to store the compressed gas on site, either short term or long term. Many of the plant operations may also implement scrubbers and separators in their address of the carbon dioxide and hydrocarbon byproducts. In any case, there is a cost to such plant operations addressing carbon dioxide exhaust. A potential advantage and commercial benefit to implementing a system and process according to the invention therefore presents itself in the form of receiving third party carbon dioxide supply, preferably for a fee, in addition to obtaining a ready supply of carbon dioxide for the system's methane production needs. The plant or utility may also claim income from carbon credits. Although a system of carbon credits is not particularly established in the United States, carbon credits are presently valued in Europe at about 25% of fuel cost. An added benefit of consuming third party CO₂at the utility level is that when pressurized CO₂is released from the high pressure of its transport container, it is cold and the utility can use the latent heat in its exhaust to heat the imported CO₂to a usable temperature without cost.
FIG. 4 depicts yet another variation of the system and method according to the invention. Specifically, FIG. 4 depicts an alternative or supplemental source of hydrogen supply for the reactor. With the capabilities of hydrogen storage 266, hydrogen may be transported from outside sources at any time, for later use by the reactor 162. FIG. 4 suggests transporting the hydrogen by truck 378, but hydrogen may also delivered by other transportation means. This supply of hydrogen may be especially beneficial during long periods of peak demand when excess electricity may not be as readily available for use in operating the hydrogen generator 160. In this way, operation of the reactor 162 may be maintained to process the higher volume of carbon dioxide exhaust from the furnace 124 and, at the same time, continue to reduce dependence on and consumption of the supply of fossil fuel.
FIG. 5 illustrates yet another variation of the system and process according to the invention, wherein like reference numerals are used to indicate like elements. In this system 410, a fossil fuel electricity generating plant 420 is modified to incorporate a carbon separation unit 480 at or about the exhaust of the furnace 124. Exhaust gases from the furnace 124 is directed through the separation unit 480, thereby separating hot carbon dioxide gases from the exhaust and delivering only this separated portion of the exhaust gases to the reactor 162. The rest of the exhaust, which consists substantially of nitrogen, may be released safely into the environment. This modification operates to mitigate the possible build-up and release of harmful nitrous oxide emissions from the furnace 124. As air contains nitrogen, the recirculation of hot furnace exhaust gases as suggested in previous descriptions of the inventive system is likely to pass more (and hotter) nitrogen into the furnace 124. This promotes the formation of nitrous oxide, especially as the hot exhaust gases traverse the furnace-reactor loop 166 multiple times.
The systems 110, 210, 310 according to the invention generally allows for a method of generating and distributing electricity that facilitates near optimal operation of both the fossil fuel plant 120, 220, 320, and the alternate or renewable energy electricity generating system 152. The inventive system and method also allows for generation and distribution of electricity in a manner that meets consumer demand, while promoting optimal operation of both power plants, and allaying the safety and environmental concerns of the local and global communities.
In further aspects of the invention, the system is utilized in a method of electrical grid energy storage and/or load balancing by and between the traditional fossil fuel electric generating plant and a renewable energy electricity generating station(s). As discussed above, the utility often operates the fossil fuel plant even when total system capacity exceeds demand, due to the plant's inability to readily respond to and match changing demand, and the risk from relying on renewable energy in meeting demand. Methods according to the invention, as further described below, introduce energy load balancing in which the fossil fuel plant may be maintained at or near operating capacity, while re-circulating its electricity output and fuel supply. In a further aspect, such load balancing entails simultaneous increase and decrease of fuel supplies into the furnace of the fossil fuel plant.
Exemplary Processes for Generating Electricity and/or Electricity Distribution
FIG. 6A is a simplified flow chart of the steps in an exemplary method of generating electricity. The description of the inventive method may be read with particular application to a fossil fuel plant that incorporates certain unique mechanical features (i.e. in accordance with the inventive system). That is the inventive method can be performed in the context of operating a fossil fuel plant, and more specifically, certain steps are performed at the fossil fuel plant. Firstly, fossil fuel is burned to generate heat (610). The heat generated is transferred to, and utilized, in a Rankine cycle that drives the fossil fuel plant's turbine (612). In this manner, the generators are operated to output electricity (614). In a subsequent step, at least some of the electricity output (i.e., excess electricity) is directed back to (or maintained within) the fossil fuel plant (616). Further, the electricity directed is utilized to generate hydrogen at the fossil fuel plant (618) and this hydrogen is reacted with carbon dioxide to produce methane (620). Then, as with the fossil fuel, the methane is burned to generate heat (622) (i.e., at the furnace). The inventive method then reverts back to the step of utilizing heat in the Rankine cycle to drive the fossil fuel plant's turbine (612). In this subsequent burning step, however, the methane gas produced by the reacting step (620) is utilized as fuel.
In further embodiments, the method may alternate between, or select from, methane, fossil fuel, or combinations thereof as the source of chemical energy exploited in the burning steps. Preferably, the inventive method includes the step of capturing carbon dioxide exhaust from the burning step and utilizing the captured carbon dioxide as a reactant in the reacting step. This method embodies the recirculation loop 166 described previously. In further embodiments, the method entails directing all of the electricity output to the hydrogen generation step (i.e., it powers the hydrogen generating step or operation) or directing some portion of the output to the electrical grid to meet grid demand. Such a method may be described as embodying or employing an energy recirculation loop according to one aspect of the invention. In a further aspect of the invention, the electricity recirculated may, in response to a change in grid demand or grid capacity, be re-directed back to the grid to accommodate the “negative” change. Such a response may be accompanied by the step of increasing fossil fuel supply to the furnace for burning so as to accommodate any reduction in hydrogen generation and methane supply to the furnace.
The simplified flow diagram of FIG. 6B presents an exemplary electricity generating process 660 that incorporates both a fuel-carbon dioxide recirculation loop 166 and an energy recirculation loop 168, according to the invention. In the energy recirculation loop 168 and process, electricity is generated by the fossil fuel plant (662), but maintained within the plant (664). Specifically, the electricity is directed to (664) and used in a hydrogen generation step (666). Preferably, the electricity generated is expended as input in an electrolysis reaction to generate hydrogen. The hydrogen generated is subsequently reacted with carbon dioxide to produce methane gas, in a reacting sub process (668). The methane gas is then supplied to a combustion process (670) that converts the chemical energy (provided primarily by the hydrogen previously generated) in the methane into heat. As is well known in the art, the heat produced is then used in a Rankine cycle to drive the conversion of mechanical energy into electrical output by the electric generator (662). This stage is, of course, the electricity generating sub process (662) at the top of the flow chart. In this recirculation loop 168, energy is converted from electricity to chemical energy (in the hydrogen and in the methane), to heat, to mechanical energy, and then back to electricity. It should be noted, however, the efficiency of this recirculation loop (168) will be less than 100% and more likely to be in the neighborhood of about 75%.
In the carbon dioxide recirculation loop 166, the combustion sub-process (670) produces carbon dioxide gas in addition to heat. The hot carbon dioxide gases are then captured and re-directed (672) as opposed to being exhausted by the fossil fuel plant. Specifically, the captured dioxide gas is directed to the sub-process (668) that produces methane, and employed therein as a reactant. The methane is then supplied to the combustion sub-process (670), which exhausts and effectively recycles the carbon dioxide. As previously described, the combustion and reacting sub-processes may be performed through operation of the fossil fuel plant's furnace and a Sabatier-type reactor, respectively.
The simplified flow chart of FIG. 7 reveals yet another exemplary embodiment of a method (700) of generating and distributing electricity according to the invention. In the steps of the illustrative method (700), both a fossil fuel plant and an alternate electricity generating station are operated to output electricity to the grid. Initially, the fossil fuel plant is operated to generate electricity output (i.e., at the electric generator) (720). Meanwhile, the alternate electricity generating station is also operated to generate electricity output (720). At this stage, electricity output is directed from both the fossil fuel plant and the alternate electricity generating station (730). This is performed to satisfy 100% of the demand on the electrical grid, for example. Then, at the fossil fuel plant, at least a portion of the electricity output is directed to within the plant (740), as opposed to being directed to the electrical grid. The method then entails generating hydrogen at the fossil fuel plant (750), utilizing the electricity directed within the plant in the preceding step. The hydrogen generated is subsequently used in a reacting step (760), wherein hydrogen is reacted with carbon dioxide to produce methane. The methane is then supplied as fuel in continuing to operate the fossil fuel plant to generate electricity output (780). Preferably, in further and alternate steps, at least some or all of the electricity output now generated (by the electric generator) is again directed (i.e., recirculated) to, and used in, a continuing hydrogen generating step (see Step 750). In effect, the fossil fuel plant generates electricity that is then used to make its own fuel.
In further embodiments of the invention, the method may include the steps of continuing to operate the fossil fuel plant but directing all of the electricity output to the hydrogen generating step. In this further variation, the alternate electricity generating station is further operated at a capacity that is essentially satisfying 100% of grid demand. In further embodiments, this operating step may be altered so that some of the electricity output is directed to the fossil fuel plant for use (and consumption) in the hydrogen generating step. In yet further embodiments, continued operation of the fossil fuel plant may include intermittently utilizing fossil fuel and/or the produced methane for burning to generate heat used in a Rankine cycle. Further yet, the process may include a step of re-directing the re-circulated electricity (from the fossil fuel plant) back to the grid in response to a “negative” change in grid capacity (increased demand and/or reduced wind farm output).
Exemplary States of System Operations
Table A below is provided to further illustrate aspects of the invention by describing exemplary modes and states of operating a system comprising a fossil fuel plant, a wind farm, and an electrical grid interconnected with both the plant and the wind farm. Each of the modes or states of operation are described in terms of the system's response to the changes in demand placed on the electrical grid or the electrical capacity available to the grid. In this way, Table A also helps to illustrate a method of balancing the loads and/or capacities (outputs from the plant and wind farm) on an electricity generating and distribution system according to the invention.

TABLE A

Exemplary States of System Operation

	2. Grid		4. Momentary
	Demand		Excess Plant		5. Wind		7. Consumption of
	(% of		Output	Farm		6. Fossil Fuel	Energy for
	max or	3. Fossil Fuel	(Plant Output -	Output	Consumption	Synthetic Methane
	peak	Plant Output	Demand) as	(% of Max	(assuming apx	(100% of
	power	(% of Max or	% of Max or	or Peak	cycle eff of	Renewables +	8. Hydrogen
1. State	demand)	Peak Demand)	Peak Demand	Demand)	75%)	excess power)	Storage	9. Comments

1	85%	86% of	1%	Offline	100%	Offline	Offline	Normal
		peak demand						Plant Output
2	Peak,	102% of peak	2%	3%	(102 − .75*(3 +	5% (2 + 3)	Offline	Plant
	100%	demand			2) ~99%			Throttling
		(5% maybe						Up
		Recalculated with
		97% to Grid)
3	75%	80% of	5%	3%	(80 − .75*(5 +	8% (5 + 3)	offline	Plant
		peak demand			3)) ~74%			Throttling
		(8% Recirculated;						Down
		72% to Grid)
4	60%	~70% of Peak	10%	70%	(70 − .75*(70 +	80% (10 + 70)	Not quite	Plant
		Demand			10) ~10%		there	Throttling
		(All 70%						Down
		Recirculated; 0%						~100% CO₂
		to Grid))						Captured
5	Low-Up	Low to Variable	Substantial	>100%	Minimal, if any	Near 100%	Substantial	Plant Output
	to 100%	Power Setting (all						Down
		Recirculated)						~100% CO₂
								Captured
6	Low-Up	Low to variable	Substantial	>100%	Minimal, if any	Near 100%	Substantial	Plant
	to 100%	Power Setting (all						Output
		Recirculated)						Down
								CO₂Draw
								from
								Storage/
								Pipeline
								Produce
								& export
								methane

In Table A, the Grid Demand for each of the States as well the Outputs of the Fossil Fuel Plant and the Wind Farm are expressed in relation to (% of) the Maximum or Peak Grid Demand for the exemplary operating period (e.g., a twenty-four hour period). Of the amount indicated for Plant Output, Column 3 also provides the amount that is re-circulated and the amount directed to the grid. Under Column 4, Table A provides the power output from the Fossil Fuel Plant that exceeds Grid Demand (Momentary Excess Plant Output). Table A also describes the operating modes of three important sub-processes: consumption, by the furnace, of fossil fuel; consumption, by the furnace, of methane generated by the reactor; and storage of hydrogen generated by the hydrogen. The two fuel consumption columns (6, 7) indicate the percentage of the fossil fuel plant output (which is provided as a percentage of Maximum Grid Demand) derived from the fossil fuel supply or from re-circulating electricity to produce methane. For these examples, the recirculating sub-process is assumed to have an efficiency of 0.75 (i.e., each BTU of electrical energy re-circulated is turned to 0.755 BTU furnace fuel).
In State 1, the fossil fuel plant is operated to meet or exceed grid demand. The level of grid demand at this initial state is provided at 85% of the Maximum Grid and plant output slightly above that, at 86% of Peak Demand. For illustration, the reactor is not operated to generate methane in this initial state and the fossil fuel plant only bums fossil fuel. The hydrogen generator is also offline at this stage and thus, Table A notes that excess hydrogen is not being directed to storage. In State 1, the system, including the fossil fuel plant, is, in effect, operated in the conventional manner.
After exemplary State 1, demand on the grid may rise toward peak demand. Graph (a) in FIG. 8 describes the typical relation between output from a fossil fuel plant (dash curve) and grid demand (solid curve) during a period of operation (e.g. a typical 24-hour period). The period includes both a rise (left of peak) in grid demand toward peak demand and a subsequent decrease from peak demand. State 2 is indicated at the peak of the demand curve. As fossil fuel plant output rises toward peak demand, it leads demand slightly. The excess energy simply pads the demand curve, as electricity is neither stored nor recycled during this conventional system operation. After peak demand (right of peak), reductions in plant output normally lag diminishing demand and thus, excess energy is generated. In conventional operations, this excess electricity is also wasted.
In exemplary State 2, the fossil fuel plant output is at 102% (2% momentary). Meanwhile, the wind farm is operating and all of its output is directed to the grid. The grid is now supplemented by some, albeit relatively slight, output from the renewable energy source. The wind farm output satisfies, in this example, about 3% of the peak grid demand, which together with the fossil plant output means that the system is producing 105% of grid demand. In one mode, all of the fossil fuel plant output may be directed to the grid along with the wind farm output. With all system output distributed to the grid, the extra 5% in capacity serves as a cushion for absorbing any sudden rise in demand or interruption of wind farm output.
In the alternative, and as shown in Table A, the fossil fuel plant may elect to re-circulate the additional 5% capacity and only direct the 97% of Maximum Grid Demand to meet current grid demand (along with the 3% contribution from the wind farm). In this case, the recirculated energy would be used to generate hydrogen, which would then be used to generate methane for the furnace. As shown in Column 6, the re-circulated energy results in the generation of some methane and also begins to reduce fossil fuel consumption by a slight margin.
State 3 in Table A describes an exemplary state of operation in which grid demand has subsided to 75% of peak demand. With fossil fuel plant output alone exceeding grid demand by 5%, the total electricity output of the system exceeds grid demand by 8%. Rather than wasting this 8% of output on the grid, the system according to the present invention balances the system outputs by re-circulating this energy within the fossil fuel plant and ultimately, producing methane for the furnace (as described previously). Table A also indicates that fossil fuel consumption is reduced (by an amount equal to 5% of the Maximum Grid Demand)-due to the additional availability of methane.
In contrast to conventional system operations, State 3 describes a mode of operation that is particularly responsive to fluctuations in grid demand and adept of balancing the outputs of the fossil fuel plant and wind farm with these fluctuations. As grid demand falls, whether suddenly or gradually, any resulting excess plant output is re-circulated. Meanwhile, all of the wind farm output is maintained on the grid. In the event of an increase in wind farm capacity, fossil fuel plant output on the grid may be “reserved” and “stored” in favor of the additional wind farm output. In the case of a wind farm, such an increase may be caused by increased wind availability due to weather occurrences. In a system employing a solar power generating station, increased output may arise as sustained cloudy conditions unexpectedly give way to a clear and sunny day.
As noted previously, the traditional fossil fuel plant and the Rankine cycle it employs do not readily respond to or accommodate such rapid changes in demand or output; so, any potential energy windfall usually goes untapped. With the present exemplary system, the system balances plant and wind farm output and grid demand, by directing excess output to energy storage and thereby, exploiting the energy windfall. In the same instant as the grid is oversupplied by additional output, the system adjusts fossil plant operations. Specifically, fossil fuel supply to the furnace is reduced and the now “excess output” of the plant is re-circulated. As described previously, the re-circulated output is used to generate hydrogen, which in turn, is used to produce methane. As the methane replaces the reduction in fossil fuel supply to the furnace, the power output from the furnace (in this example) is hardly reduced from the prior exemplary state. Only the consumption of fossil fuel by the plant is reduced.
If, thereafter, grid demand suddenly increases or wind farm output falters, the utility will sense the change in conditions and reduce the recirculation of excess electricity to the hydrogen generator. At the same time, the supply of fossil fuel to the furnace will be increased to offset the reduction in methane production. In both modes of operations, the system responds to a change (or imbalance in outputs and demand) by adjusting the energy recirculation sub-process in the fossil fuel plant.
In exemplary State 4 (see also FIG. 8 b), the capacity of the wind farm is greatly expanded and its output is greater than the minimum nightly demand. All of the wind farm output is directed to the grid, however. The fossil fuel plant continues to operate as before, perhaps at reduced capacity (˜70% of Maximum Grid Demand), but still above the grid demand (60%) and ensuring that operating pressures and temperatures are maintained. The excess output above grid demand again provides a cushion against sudden decline or failure in wind farm production. In any event, the wind farm output is sufficient to meet all of grid demand; so, the fossil fuel plant is operated mostly in re-circulating mode. With abundant re-circulated electricity available for hydrogen production, effectively all of the furnace exhaust is recycled into methane and burned.
If, under exemplary State 4, the system experiences a sudden interruption in the output from the wind farm, the utility can readily direct fossil fuel input into the furnace and plant output back to the grid. Although, in such a load balancing response, methane production may be reduced due to a reduction in hydrogen supply, fossil fuel supply to the furnace may be increased to offset the reduction and maintain fossil plant output at the desired level. In this way, the fossil fuel plant and the rest of the system experience a seamless transition from one mode of electricity generation and distribution to another.
Furthermore, because the system becomes limited by the availability of CO₂in recirculation, any excess production of hydrogen may be placed in storage. Thus, all of the excess electricity in the system is still re-circulated and used to generate hydrogen, even though not all the resulting hydrogen is immediately reacted with CO₂. Such excess hydrogen supply may be used later in the day, for example, when the system is using more energy and is not CO₂limited.
Exemplary State 5 is provided to show modes of operation when wind farm output is greatly expanded and much greater than Grid Demand at most if not all times. In accordance with another aspect of a method of the invention, some of the wind farm's output is deployed to satisfy all of the grid demand, while the remaining output is directed to the fossil fuel plant for hydrogen generation (i.e., recirculated). This optional course of utility management and electricity distribution is, of course, contrary to traditional methods in which wind farm output is not only reduced in favor of fossil fuel plant output, but is ignored or shut off if demand could be met by fossil fuel plant production. In this exemplary State, the fossil fuel plant operates at full pressure and temperature, but at a somewhat lower power setting. Also, in this state, the fossil fuel plant is readily available to supply the grid if and when wind farm output declines. With continuing excess electricity being recycled, fossil fuel plant production draws from methane production for furnace fuel. The fossil fuel supply is, therefore, effectively shut down and the reactor consumes hydrogen to produce methane and satisfy 100% of the fuel requirements of the furnace. In State 5 (see also FIG. 9B), energy is recycled and the power curve remains smooth to maintain stability in a Rankine cycle even if the demand suddenly drops or wind farm output suddenly declines. Also, with reduced amounts of fossil fuel consumed by the furnace, the amount of carbon dioxide exhaust is reduced (of which the system is able to capture near 100%). In fact, the system at this point begins to become limited by CO₂availability, not by electricity or hydrogen availability. As such, the fossil fuel plant may import CO₂from outside sources and use this CO₂to supplement the plant's CO₂needs. The fossil fuel plant is uniquely positioned to process CO₂supplied by a 3^rdparty because when the CO₂leaves the pressurized delivery system (pipe, truck, etc) it becomes cold and the fossil fuel plant has the latent heat in its exhaust to heat the CO₂, without cost, to a temperature suitable for reacting.
Exemplary State 6 may be regarded as an extension of State 5. At different times of an operating period, the ratio of the output from the wind farm to grid demand becomes so large that the system desires to have a supply of carbon dioxide from storage or pipeline from which the reactor can consume. In further scenarios (and modes of operations), the reactor may also draw hydrogen from hydrogen storage to supplement supply to the reactor. This mode of operation may actually produce excess methane which may be exported onto the natural gas grid or shipped to other locations. Such a mode of operation is particularly suited for a period after an extended exemplary State 6, when there may be a build-up in hydrogen storage.
Table A and the above descriptions of the stages of operation are, of course, provided for illustration only. Actual operation of the system according to the invention may involve only certain stages or other states, and different sequence of states and modes of operations.
Now referring to the graphical representations of FIG. 8, each of the graphs illustrates an exemplary twenty-four hour period of operation of multiple electricity generating processes, including operation of the system according to the invention. Graphs (a) and (b) display exemplary electricity production modes for the fossil fuel plant and the renewable energy electricity generating station, relative to grid demand. Specifically, Graph (a) illustrates how the inventive system may integrate and distribute variable and erratic electricity output of the renewable energy electricity generating station. In the scenario represented, electricity output by a renewable energy electricity generating station is relatively small compared to fossil fuel production and grid demand. Thus, all of the renewable energy electricity generating station's output is directed to the grid at all times, even during the early morning hours (in the left region of the graph) when grid demand is lowest.
Graph (a) also displays the level of fossil fuel consumption by the fossil fuel plant and illustrates how this may be impacted by operation of the inventive method. During the low demand times (i.e., early morning hours (as indicated in the left region of the graph), the fossil fuel plant is operated at a relatively low output rate, but excess production still results. As shown in Graph (a), the rate of fossil fuel consumption is significantly lower than the fossil fuel plant's total output. The excess power is, of course, being redirected to within the plant and used to generate hydrogen and ultimately, methane. With methane available, the amount of fossil fuel consumption is reduced and the utility can claim a carbon offset. Later in the day, when grid demand has risen, all of the fossil fuel electricity output is directed to the grid, and there may be little or no excess power to be re-directed to within the fossil fuel plant. This point of the day may be read as corresponding to a State of System Operations similar to State 2 in Table A (which is followed by a point that may correspond to State 3 in Table A). Throughout, the plant's steam cycle is maintained at normal pressure and temperature, with output being changed only gradually, thereby minimizing stress on plant equipment.
The modes of operation represented in Graph (a) may be limited by hydrogen supply. All of the hydrogen generated is directed to the reactor and used to make methane. All of the produced methane is also consumed, by the furnace. In other scenarios, the system may store excess hydrogen, and even methane, that are generated during process operations and save these loads for later use.
The second Graph (b) illustrates exemplary modes of operation wherein much higher levels of electricity output are available from the renewable energy electricity generating station. In fact, the electricity output from this renewable energy source is significantly higher than fossil fuel plant output. During the early morning hours, output from the electricity generating station even exceeds grid demand. (See e.g., area between the Renewable Power curve and the Power Demand curve). The system generates hydrogen using re-circulated electricity but elects to store it on-site rather than feed the reactor. Notably, methane production is not stored. This may be because operation of the system does generate enough “excess” carbon dioxide. Further, because less than 100% of the carbon dioxide can actually be captured from the furnace exhaust and the Sabatier reactor will not convert 100% of the hydrogen inputted into methane, some fossil fuel consumption must take place to compensate (for carbon dioxide and for energy output). Fossil fuel consumption is, therefore, at a minimum, but is not ceased. Alternatively, the CO₂could be added via a 3^rdparty supplier, i.e., the fossil fuel plant could run on stored H₂and imported CO₂.
Later in the day, as grid demand rises and exceeds output from the renewable energy electricity generating station, increasing fossil fuel consumption may be required to increase the fossil fuel plant's contribution to the grid. With increased fossil fuel plant production, more carbon dioxide is exhausted by the furnace. Thus, the reactor has available to it larger amounts of carbon dioxide that can be matched with hydrogen from storage (which was stored at earlier low demand periods). As a result, the amount of fossil fuel consumption can actually be reduced (as represented by the dash lines extending from the fossil fuel consumption curve).
System and Method Incorporating Hydrogen Combustion
FIGS. 9A and 9B illustrate alternate systems (and methods) 910, 910′ according to the invention, wherein like reference numerals are used to indicate like elements. Specifically, the systems 910, 910′ provide for the direct combustion of hydrogen in the furnace as an alternative to combustion of fossil fuel. In FIG. 9A, the hydrogen generator 160 is shown connected directly to the inlet of the furnace 124 via a hydrogen fuel feed line 972. In this system 910, the fossil fuel plant 920 does not employ a reactor for reacting hydrogen and carbon dioxide to produce methane. Thus, the combustion of hydrogen replaces the use of produced methane as an alternative furnace fuel to fossil fuel. Advantageously, operation of this system 910, with direct combustion of hydrogen in the furnace 124 instead of fossil fuel or methane, does not result in carbon dioxide exhaust.
In the alternative embodiment illustrated in FIG. 9B, the system 910′ includes a fossil fuel plant 920′ that also employs a Sabatier-type reactor 162 to react hydrogen and carbon dioxide (as in previously described embodiments) and provide methane fuel to the furnace 124. As shown, the furnace 124 can selectively receive hydrogen directly from the hydrogen generator 160 via the hydrogen feed line 972 or receive methane from the reactor 162. As with previously-described embodiments, the fossil fuel plant 920′ employs a recirculation line 974 to capture carbon dioxide exhaust and use same to react with hydrogen to produce methane. The fossil fuel plant 920′ can, therefore, selectively employ methane or hydrogen as an alternative to fossil fuel for combustion or burn fossil fuel. This alternative system 910′ also retains the capability of receiving and processing third-party carbon dioxide supplies.
Applicant notes that hydrogen burns about 500° F. hotter than methane and at a flame velocity that is about 10 to 20 times higher than that for methane. In air, hydrogen bums with a “pop” and it is far more explosive than gasoline. For these reasons, it is expected that some traditional natural gas plant furnaces cannot be practically employed for direct hydrogen combustion or will require modifications or redesign to do so. Applicant recognizes, however, that a coal-fired furnace usually burns at almost the same temperature (4000° F.) as hydrogen in air and thus, can more easily handle direct combustion of hydrogen as described herein. Also, coal fired plants are usually in greater need to reduce its carbon footprint (than natural gas plants, for example, due to greater carbon dioxide exhausts). Thus, the system configurations in FIGS. 9A and 9B may be particularly suited for incorporation with such coal fired fossil fuel plants.
The systems 910, 910′ (or parts thereof) of FIGS. 9A, 9B may be employed in, or be the subject of, many of the processes and methods described earlier. These include the methods and processes described in respect to or in relation to FIGS. 6-8, as well as Table A. In many of such applications, the described methods and processes may require some modification so as to incorporate the systems and sub-processes described in respect to FIGS. 9A, 9B.
In the preceding drawings and this specification, typical preferred embodiments of the present invention have been disclosed. Although specific terms are employed, the terms are used in a descriptive sense only and not for purposes of limitation. The present invention has been described in considerable detail with specific reference to the illustrated embodiments. It will become apparent, however, that various modifications and changes can be made within the spirit and scope of the invention as described in the foregoing applications. For example, various components and systems described herein may be utilized in different electricity generating or distributing applications or in different combinations and configurations. Furthermore, some of the processes or sub processes described in respect to operation of specific fossil fuel electricity generating installations may, individually or in various combinations, be employed in and with respect to different power plant or process installations.

Claims

1. A method of generating electricity for distribution via an electrical grid, wherein a fossil fuel plant is interconnected with the electrical grid and incorporates a turbine and an electric generator operable to output electricity to the grid, the method comprising the steps of

at the fossil fuel plant, employing a Rankine cycle to drive the turbine and electric generator to generate electricity, including burning a fossil fuel to generate heat and transferring the generated heat to a working fluid of the Rankine cycle;

providing hydrogen at the fossil fuel plant;

providing an alternative fuel to the fossil fuel by utilizing chemical energy in the hydrogen;

after burning fossil fuel, burning the alternative fuel to generate heat;

transferring the heat generated by the burning alternative fuel step for use in the Rankine cycle; and

continuing to employ the Rankine cycle to drive the turbine and electric generator to output electricity.

2. The method of claim 1, wherein the step of providing an alternative fuel includes reacting the hydrogen and the carbon dioxide at the fossil fuel plant to produce methane as the alternative fuel.

3. The method of claim 2, wherein the Rankine cycle is a power plant steam cycle employing water as a working fluid, the method further comprising the steps of:

generating hydrogen by operating a hydrogen generator, wherein the reacting step utilizes the generated hydrogen as a reactant; and

wherein the steps of generating hydrogen and reacting hydrogen and carbon dioxide are performed at the fossil fuel plant, the reacting step including operating a reactor to produce methane.

4. The method of claim 3, wherein the burning steps exhaust carbon dioxide, the method further comprising the steps of :

capturing exhausted carbon dioxide from the burning steps and directing the captured carbon dioxide to the reactor for use in the reacting step as a reactant.

5. The method of claim 3, further comprising the step of directing at least a portion of the electricity outputted by the electric generator to the hydrogen generator, whereby the directed electricity is expended during the hydrogen generating step.

6. The method of claim 3, further comprising the steps of:

interconnecting a renewable energy electricity generating station with the electrical grid;

operating the renewable energy electricity generating station to generate electricity;

directing electricity from the renewable energy electricity generating station to the electrical grid; and

re-directing at least a portion of the electricity outputted by the electric generator to the hydrogen generator, whereby, in the hydrogen generating step, the directed electricity is expended to generate hydrogen to supply the reacting step.

7. The method of claim 6, further comprising the step of

during the step of re-directing at least a portion of the electricity outputted by the electric generator, reducing a supply of fossil fuel to the furnace such that the fossil fuel burning step is correspondingly reduced and the methane burning step is increased relative to the fossil fuel burning step.

8. The method of claim 7, further comprising the step of:

upon a change in demand on the electrical grid, redirecting at least some of the electricity re-directed to the hydrogen generator back to the grid to accommodate the change in demand.

9. The method of claim 8, further comprising the steps of

during the second re-directing step, increasing the fossil fuel burning step by increasing the supply of fossil fuel to the furnace.

10. The method of claim 3, further comprising the steps of:

altering the step of generating hydrogen by directing at least some of the hydrogen generated in the hydrogen generating step to storage;

storing the directed hydrogen in storage at the fossil fuel plant; and

after the storing step, altering the reacting step by drawing at least some of the hydrogen for the reacting step from hydrogen storage.

11. The method of claim 1, further comprising the step of:

ceasing the step of burning fossil fuel such that the transferring heat step includes receiving about 100% of the heat used in the Rankine cycle from the step of burning alternative fuel produced by the reacting step.

12. The method of claim 1, wherein the step of burning the alternative fuel includes combusting the hydrogen in a furnace of the fossil fuel plant.

13. A method of generating and distributing electricity via an electrical grid, the method comprising the steps of:

operating a fossil fuel plant to generate electricity output;

at the fossil fuel plant, directing at least a portion of the electricity output to within the plant;

at the fossil fuel plant, generating hydrogen including utilizing the electricity directed within the plant to generate hydrogen;

utilizing chemical energy in the generated hydrogen to provide an alternative fuel for the fossil fuel plant; and

continuing the fossil fuel plant operating step utilizing the alternative fuel as fuel for a furnace of the fossil fuel plant, to generate electricity output.

14. The method of claim 13, further comprising the steps of:

operating a renewable energy electricity generating station to generate electricity output;

directing electricity output from each of the fossil fuel plant and the renewable energy electricity generating station to the electrical grid for distribution;

reacting the generated hydrogen with carbon dioxide to produce methane; and

continuing the fossil fuel plant operating step utilizing the produced methane as the alternative fuel to generate electricity output.

15. The method of claim 14, wherein the step of operating a fossil fuel plant includes utilizing fossil fuel as fuel in a burning step to generate heat; and

wherein, after the step of continuing to operate the fossil fuel plant, the method further includes directing, at least a portion of the electricity output to within the plant and utilizing the directed electricity in the hydrogen generating step.

16. The method of claim 15, wherein the step of operating the fossil fuel plant includes exhausting carbon dioxide, the method further comprising the step of:

capturing at least a portion of the exhausted carbon dioxide and directing the captured carbon dioxide to the reacting step, whereby the carbon dioxide is reacted with hydrogen.

17. The method of claim 14, further comprising the step of:

altering the step of directing electricity output by re-directing all of the electricity output of the fossil fuel plant to within the plant and directing at least a portion of the electricity output of the renewable energy electricity generating station to within the plant, whereby the hydrogen generating step includes expending directed electricity output from both the plant and the renewable energy electricity generating station.

18. A system for generating electricity for distribution via an electrical grid, the system comprising:

a fossil fuel plant interconnected with, and configured to, direct electricity output to the electrical grid, the fossil fuel plant being further configured to operate a Rankine cycle to drive a steam turbine and electric generator combination, the fossil fuel plant including

a furnace for burning fuel to generate heat,

a hydrogen generator for generating hydrogen,

a reactor for reacting hydrogen and carbon dioxide to produce methane.

a recirculating loop interconnecting the furnace and the reactor including a line for directing methane produced by the reactor to an inlet of the furnace and a line directing carbon dioxide captured from the exhaust of the furnace to the hydrogen generator; and

power transmission means for directing electricity output of the electric generator to the hydrogen generator; and

electricity output transmission means for directing electricity output to the electrical grid.

19. The system of claim 18, wherein the hydrogen generator is an electrolyzer configured to draw electricity from the power transmission means for electrolysis of water; and

wherein the reactor is a Sabatier reactor configured to pass a mixture of the carbon dioxide and hydrogen and initiate a reaction producing methane.

20. The system of claim 18, further comprising a renewable energy electricity generating station interconnected with, and configured to, direct electricity output to the electrical grid, wherein the power transmission means and electricity output transmission means are further configured to direct electricity output of the renewable energy electricity generating station to the hydrogen generator.