METHODS FOR PRODUCING AND STORING ENERGY SOURCES

Abstract

A method for producing an energy source from excess electricity is disclosed. The method uses excess electricity from a power grid when electrical demand is low. The method produces the energy source by performing the steps firstly in the storage phase of feeding the excess electricity to a thermal reactor wherein solid carbon and gaseous hydrogen are produced from the thermal reaction of a hydrocarbon; feeding the gaseous hydrogen to a hydrogen storage unit; feeding the solid carbon to a carbon storage unit; and secondly in the discharge phase, feeding the solid carbon to a combustion unit wherein steam is produced; and feeding the steam to an engine or a turbine thereby producing electricity.

Claims

1. A method for producing an energy source using excess electricity from a power grid comprising the steps: a) feeding the excess electricity to a thermal reactor wherein solid carbon and gaseous hydrogen are produced from the thermal reaction of a hydrocarbon; b) feeding the gaseous hydrogen to a hydrogen storage unit; c) feeding the solid carbon to a carbon storage unit; d) feeding the solid carbon from the carbon storage unit to a combustion unit wherein steam is produced; and e) feeding the steam to a turbine thereby producing electricity.

2. The method as claimed in claim 1 wherein the solid carbon energy source is combusted.

3. The method as claimed in claim 1 wherein excess electricity from the power grid is an amount of electricity produced that is greater than the amount of electricity demand.

4. (canceled)

5. The method as claimed in claim 4 where the hydrocarbon is methane.

6. The method as claimed in claim 1 wherein the gaseous hydrogen is compressed before being fed to storage.

7. The method as claimed in claim 1 wherein the gaseous hydrogen is deployed in a method selected from the group consisting of car fueling, pipeline injection, and fuel cell for power generation.

8. The method as claimed in claim 7 wherein the gaseous hydrogen is combusted to produce electricity.

9. The method as claimed in claim 1 further comprising feeding an oxygen-containing gas selected from the group consisting of air, enriched air and oxygen to the combustion unit.

10. The method as claimed in claim 1 wherein the combustion unit is a heat recovery steam generator.

11. The method as claimed in claim 1 further comprising producing carbon dioxide in the combustion unit.

12. The method as claimed in claim 1 wherein the turbine produces low pressure steam which is fed to a second heat recovery steam generator.

13. The method as claimed in claim 12 wherein the second heat recovery steam generator feeds high pressure steam to the combustion unit.

14. (canceled)

15. The method as claimed in claim 1 further comprising feeding the steam to an engine to produce electricity.

16. A method for producing electricity using excess electricity from a power grid comprising the steps: a) feeding the excess electricity to a thermal reactor wherein solid carbon and gaseous hydrogen are produced from the thermal reaction of a hydrocarbon; b) feeding the gaseous hydrogen to a hydrogen storage unit; c) feeding the solid carbon to a carbon storage unit; d) feeding the solid carbon from the carbon storage unit to a combustion unit wherein steam is produced; and e) feeding the steam to a turbine thereby producing electricity.

17. The method as claimed in claim 16 wherein excess electricity from the power grid is an amount of electricity produced that is greater than the amount of electricity demand.

18. (canceled)

19. The method as claimed in claim 18 where the hydrocarbon is methane.

20. The method as claimed in claim 16 wherein the gaseous hydrogen is compressed before being fed to storage.

21. The method as claimed in claim 16 wherein the gaseous hydrogen is deployed in a method selected from the group consisting of car fueling, pipeline injection, and fuel cell for power generation.

22. The method as claimed in claim 21 wherein the gaseous hydrogen is combusted to produce electricity.

23. The method as claimed in claim 16 further comprising feeding an oxygen-containing gas selected from the group consisting of air, enriched air and oxygen to the combustion unit.

24. The method as claimed in claim 16 wherein the combustion unit is a heat recovery steam generator.

25. The method as claimed in claim 16 further comprising producing carbon dioxide in the combustion unit.

26. The method as claimed in claim 16 wherein the turbine produces low pressure steam which is fed to a second heat recovery steam generator.

27. The method as claimed in claim 26 wherein the second heat recovery steam generator feeds high pressure steam to the combustion unit.

28. The method as claimed in claim 16 wherein the energy source is produced when electrical demand is low.

29. The method as claimed in claim 16 further comprising feeding the steam to an engine to produce electricity.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a schematic of a process for producing and storing carbon for the later production of power.

[0026] FIG. 2 is a schematic of a process for combusting the stored carbon to produce power.

DETAILED DESCRIPTION OF THE INVENTION

[0027] In FIG. 1, there is shown a process for thermally decomposing a hydrocarbon to produce hydrogen and carbon. A feed of excess electricity that is drawn from a power grid during times of lower electrical demand is directed to a thermal reactor A through line 1A. A hydrocarbon such as natural gas is fed through line 1 to a thermal reactor A. This thermal reactor A can be a typical decomposition unit. The hydrocarbon is typically methane gas that has been derived from biomass decomposition or is a waste hydrocarbon stream from various petroleum refinery operations.

[0028] The decomposition produce hydrogen which is fed through line 3 to a compressor 44 and into line 5 where it will enter a hydrogen storage container C. The solid carbon that is produced in the decomposition is fed through line 2 to a carbon storage unit B.

[0029] The compressed and stored hydrogen can be used as a power source by feeding to one or more intended destinations through line 6 to line 7 for fuel cell for power generation or line 8 for pipeline conversion and/or line 9 for car or other vehicle fueling operation.

[0030] Additionally in a co-generation like manner, the hydrogen storage can be partially integrated with the thermal reactor by feeding electricity produced by the hydrogen when used as a feed stock to join with through line 10 the excess electricity feed 1A to the thermal reactor.

[0031] Turning to FIG. 2 which represents the discharge phase of the process, power is now needed. The carbon storage unit B will provide the solid carbon through line 11 and this solid carbon is fed along with air or oxygen through line 12 into a combustor or heat recovery steam generator (HRSG) labeled D.

[0032] The carbon is combusted thereby producing carbon dioxide which is recovered through line 18 and steam which is fed through line 13 to an engine or turbine E.

[0033] The engine or turbine will be driven by the steam to produce electricity through line 14. Low pressure steam will be removed through line 15 and fed to a heat recovery steam generator F which will recover heat from the low pressure steam and which will produce high pressure steam which can be fed through line 17 back into the combustor or heat recovery steam generator D.

[0034] If pure oxygen or an oxygen-rich gas is employed to burn the carbon in the combustion unit D, nearly pure carbon dioxide can be produced and recovered. Less pure carbon dioxide can be disposed of in an environmentally responsible manner while this nearly pure carbon dioxide can be employed as a saleable merchant product or used in other industrial applications such as enhanced oil recovery operations.

[0035] Compared to the electrolysis of water, methane decomposition requires 8 to 10 time less energy. This provides more economic utilization of the carbon and hydrogen as energy storage methods.

[0036] During the storage phase of the invention, excess electricity from the grid is utilized to produce the solid carbon and hydrogen gas. The carbon that is created can be stored in a storage tank while the hydrogen produced can be used as a chemical fuel.

[0037] At a later stage when electrical demand is high and power is required in the grid, the discharge phase begins and carbon is combusted in a stream of an oxygen-containing gas such as air to generate heat and subsequently steam which can be used in conventional devices such as boilers to generate electricity when require. The storage of solid carbon is simpler and less expensive than storing hydrogen for power generation using a fuel cell. Further, compared to electrolyzer based energy storage systems which only use hydrogen while oxygen is vented, similar efficiencies are achieved.

[0038] The advantages of the subject invention can be further understood by the following example and assumption based on usage of 1 kilo mole (16 kg) of methane as a sample hydrocarbon: [0039] Methane cost: $0.26/kg ($5/MMbtu) [0040] Hydrogen price: $3/kg [0041] Electricity-buy: $0.05/KWH (solar power price at generation—conservative) [0042] Electricity-sell: $0.07/KWH (at times of power demand—conservative) [0043] Electrical Efficiency of converting methane to carbon & hydrogen: 70% (AHI has 75% actual efficiency) [0044] Electrical Efficiency of converting carbon to CO.sub.2 & power: 28% (conventional combustor) [0045] % of credit of hydrogen sale to the energy storage concept: 25% [0046] With these assumptions, the energy requirements are estimated as: [0047] To convert 16 kg methane to 12 kg carbon and 4 kg hydrogen

TABLE-US-00001 Ideal energy required KWH 21.0 Actual energy (electrical) KWH 29.9 [0048] To convert 12 kg carbon to 44 kg CO.sub.2

TABLE-US-00002 Ideal energy released KWH 110.2 Actual energy (electrical) KWH 30.9 [0049] And the corresponding revenues for the power sold to the grid are:

TABLE-US-00003 Revenues Power sales KWH produced 30.90 $2.16 H.sub.2 credit kg produced 4 $5.00 Total revenue potential; $7.16

[0050] To generate this revenue, on an operating basis, the following high level costs are required: [0051] Costs

TABLE-US-00004 Operating - storage Methane kg 16 $4.18 Power KWH used 29.9 $2.10 Total operating costs - methane & power $6.27

[0052] While this invention has been described with respect to particular embodiments thereof, it is apparent that numerous other forms and modifications of the invention will be obvious to those skilled in the art. The appended claims in this invention generally should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of the invention.