System and method for balancing power systems that convert ammonia to electrical power

Abstract

A power balancing system and method are provided in which an air separation unit (ASU) outputs a nitrogen-rich stream, a first electrolysis unit outputs a hydrogen-rich stream, and the nitrogen-rich stream and hydrogen-rich stream are converted to a first ammonia-rich stream in an ammonia synthesis unit. When additional power is needed, power generation is achieved by converting ammonia from an ammonia storage unit in an ammonia fuel cell. The system and method enable excess electrical energy to be converted to ammonia and stored during periods of low energy demand, and made available as electrical energy during periods of high energy demand.

Description

[Technical Field]

[0001] Technical Field The present invention relates to a power balancing system and method in which an air separation unit (ASU) outputs a nitrogen-rich stream and a first electrolysis unit outputs a hydrogen-rich stream. In this system, an ammonia synthesis unit receives the streams and converts them into a first ammonia-rich stream. An ammonia storage unit receives and stores the first ammonia-rich stream. When additional power is needed, an ammonia fuel cell receives and converts ammonia from the storage unit to power generation processes. The system and method allow excess power to be converted into ammonia and stored during times of low power demand, and the ammonia to be used for power generation during times of increased power demand. [Background technology]

[0002] background As renewable energy generation becomes more widespread, fluctuations in electricity production from these sources (which can occur on an hourly, daily, or seasonal basis) must be taken into account. As a solution to this problem, large-scale battery arrays are being developed commercially and are used to balance or "smooth" the supply and demand curves.

[0003] A system for balancing renewable energy generation and consumption on a power grid is disclosed in US 10323544. In US 10323544, electricity is generated as follows: a) Decomposition of NH3 to produce H2 and N2, b) Combustion of H2 / N2 (when combusted in a gas turbine, electrical energy is produced); c) Converting the sensible heat of the exhaust gas / gas turbine exhaust gas into electricity, for example, using a steam Rankine cycle or an organic Rankine cycle.

[0004] The focus is on balancing output from renewable energy sources while reducing downstream emissions of CO2 and other waste gases. Eliminating combustion or decomposition steps can lead to reduced heat demand and / or the need for in-plant reuse of heated streams. Furthermore, there is a need to reduce site area and utility consumption while increasing power production. It would also be advantageous to combine power balancing with useful electrochemical synthesis processes ("power-to-X"). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] US10323544 Summary of the Invention [Problem to be solved by the invention]

[0006] These problems are solved by the present technology.

[0007] summary The idea is to produce ammonia (NH3) when surplus electricity is generated from renewable energy sources (wind, solar, etc.). 。 NH3 is produced from N2 provided by an air separation unit (ASU) and H2 provided by electrolysis, and the electricity required for both the air separation and electrolysis processes is supplied from renewable energy. Ammonia can be easily stored in an ammonia storage unit and converted into electricity using an ammonia fuel cell when renewable energy cannot provide enough power to the power grid.

[0008] Therefore, a first aspect of the present invention relates to a power balancing system having the following configuration. - air supply, - a first water-enriched feed; - renewable electricity supply, - Air Separation Unit (ASU), - a first electrolysis unit, - Ammonia Loop, - Ammonia storage unit, - ammonia fuel cells, where: an air separation unit (ASU) configured to receive the air feed and a first portion of the renewable electricity supply and to output a nitrogen-enriched stream; - a first electrolysis unit configured to receive the first water-enriched feed and a second portion of the supply of renewable electricity and to output a hydrogen-enriched stream; - the ammonia loop is configured to receive the nitrogen-rich gas from the ASU and the hydrogen-rich gas from the first electrolysis unit and to output the first ammonia-rich gas; - the ammonia storage unit is configured to receive and store at least a portion of the first ammonia-rich stream; and to output a second ammonia-rich stream; - an ammonia fuel cell configured to receive at least a portion of the second ammonia-rich stream from the ammonia storage unit and to output an electrical power stream; wherein the power balancing system is arranged to supply power flow from the ammonia fuel cell to a power grid.

[0009] A method for balancing electrical energy in the power balancing system described herein is also provided.

[0010] Further details of the technology are provided in the following claims, the description and the accompanying drawings. [Brief explanation of the drawings]

[0011] FIG. 1 shows a schematic layout of a power balancing system in one embodiment of the present invention. FIG. 2 shows a schematic layout diagram of a power balancing system in another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Detailed Disclosure A power balancing system is provided that converts surplus electrical energy into ammonia for storage during periods of low energy demand, and converts ammonia into electrical energy for supply during periods of high energy demand.

[0013] When a component is described as an "enriched" stream, it generally means that the component makes up the majority of the stream (i.e., greater than 50% by volume). In some streams, the component may make up an even higher proportion.

[0014] Generally, the system includes: - air supply, - water-enriched supply, - renewable electricity supply, - Air Separation Unit (ASU), - first electrolysis unit, - Ammonia Loop, - Ammonia storage units, and - Ammonia fuel cells.

[0015] A supply of renewable electricity is required. The renewable electricity can be obtained from solar, wind, wave, or tidal power and is typically intermittent. A first portion of the renewable electricity supply is provided to the air separation unit and a second portion of the renewable electricity supply is provided to the first electrolysis unit.

[0016] The air feed comprises about 78 mole % nitrogen. The air separation unit (ASU) is configured to receive the air feed and a first portion of the renewable electricity supply and output a nitrogen-enriched stream. Suitably, the air separation unit includes a compressor unit and one or more pressure swing adsorption (PSA) units. The compressor unit can be configured to compress the air feed using renewable electricity. The PSA is configured to supply compressed air and output a nitrogen-enriched gas stream and a tail gas stream comprising oxygen and rare gases, such as argon. The nitrogen-enriched gas stream produced from the ASU is suitably high purity (e.g., greater than 98%, or greater than 99%) nitrogen. Membrane separation or cryogenic separation can also be used as a component of the ASU.

[0017] The water-rich feed is suitably high purity (e.g., greater than 99%, or greater than 99.999%) water or steam. The first electrolysis unit (preferably one or more SOECs) is configured to receive the first water-rich feed and a second portion of the renewable electricity supply and output a hydrogen-rich stream by electrolysis of the first water-rich feed. The hydrogen-rich stream produced in the first electrolysis unit is suitably high purity (e.g., greater than 98%, or greater than 99%) hydrogen.

[0018] The ammonia synthesis unit (so-called "ammonia loop") is configured to receive the nitrogen-rich stream from the ASU and the hydrogen-rich stream from the first electrolysis unit and output the first ammonia-rich stream. Those skilled in the art will know how to design and implement an ammonia synthesis unit to produce ammonia from N2 and H2. The ammonia synthesis unit may include a catalyst so that H2 catalytically reacts with N2. 。 The first ammonia-rich stream is suitably a gaseous NH3 stream containing ammonia of high purity (e.g., greater than 98%, or greater than 99%). The conversion in the ammonia loop is typically less than 30%. After condensing the main portion of the NH3 produced, 、 The remaining gas is added to additional synthesis gas (make-up gas) and recycled to the ammonia synthesis unit.

[0019] The ammonia storage unit is configured to receive and store a portion of the first ammonia-rich stream and output a second ammonia-rich stream. The first and second ammonia-rich streams are essentially identical in composition but may differ in physical properties (e.g., temperature and pressure). Storage of ammonia is typically accomplished in large pressurized tanks maintained at ambient temperature.

[0020] The ammonia fuel cell is configured to receive a portion of the second ammonia-rich stream from the ammonia storage unit and output a power stream. Fuel cells that convert ammonia into electrical energy are known. In one embodiment, the ammonia fuel cell includes one or more solid oxide fuel cells (SOFCs), such as one or more oxygen-ion conducting SOFCs (SOFC-O), one or more proton conducting SOFCs (PC-SOFC), or one or more direct ammonia fuel cells (DAFCs), and preferably includes one or more SOFC-O. Meanwhile, the system can further include an oxidant feed, which can be an oxygen-enriched feed, such as a high-purity (>98% or >99%) oxygen feed or air feed, or oxygen-enriched air (O2 >21%), and the feed is configured to be supplied to the ammonia fuel cell. Multiple cells can be combined into an SOFC stack, and multiple stacks can be further combined into an SOFC plant.

[0021] In an example embodiment, the ammonia fuel cell comprises one or more SOFCs. A solid oxide fuel cell (SOFC) is an electrochemical conversion device having two chambers (anode and cathode) separated by an electrolyte material made of a solid oxide or ceramic electrolyte. The oxidant feed is a high-purity oxygen-rich gas (greater than 98%, e.g., 99%) or air, or oxygen-enriched air (O2 > 21%), which is fed to the cathode side of the ammonia fuel cell. A second ammonia-rich stream enters the anode side (fuel side), where (2) NH3 is decomposed into (1) N2 and (3) H2, and the H2 then undergoes electrochemical oxidation to produce electrical energy. In one example embodiment, the ammonia fuel cell comprises one or more SOFC-O. In this example embodiment, electrons are transferred to H2 and negatively charged O2. 2- The electrons are released from the ion interaction surface and flow through an external circuit. The electron flow brings them to the cathode side of the fuel cell, where O2 accepts the electrons and converts them into O 2- ions and travel through the solid oxide electrolyte to the anode side of the cell. The electrolyte material for SOFC-O is either yttria-stabilized zirconia (YSZ) or samarium-doped ceramic (SDC) material. The output from the anode side of the SOFC-O is 、 NH 3、 N 2、 The electrolyte may contain H2, H2O, and HO. In other embodiments, the ammonia fuel cell may contain one or more PC-SOFCs or one or more DAFCs. In embodiments containing a PC-SOFC or DAFC, it is the protons that move through the electrolyte, thereby producing water (HO) on the cathode side, where the protons meet with oxygen. Thus, in ammonia fuel cell applications, a continuous supply of ammonia and oxidant creates a continuous flow of electrons and ions. The oxidant is fed to the cell.

[0022] The application of ammonia fuel cells achieves very high power efficiency. Furthermore, compared to conventional solutions, it requires a smaller footprint, reduces capital expenditures (CAPEX), and reduces utility consumption (e.g., cooling water). Thus, using one or more ammonia fuel cells (e.g., SOFC plants) instead of NH3 decomposition, gas turbines, and / or Rankine cycles increases power generation efficiency and reduces footprint and utility consumption.

[0023] By-products produced from an ammonia fuel cell can include at least one nitrogen-rich stream and at least one water-rich stream. The by-product streams provided from the ammonia fuel cell can be recycled to an associated unit.

[0024] In one embodiment, the ammonia fuel cell is configured to provide a second nitrogen-enriched stream, and the ammonia loop is configured to receive at least a portion of the second nitrogen-enriched stream from the ammonia fuel cell as a recycle stream, optionally mixed with the nitrogen-enriched stream from the ASU. In one embodiment, the system further includes a nitrogen storage unit configured to receive and store at least a portion of the second nitrogen-enriched stream from the ammonia fuel cell and output a third nitrogen-enriched stream, wherein the ammonia loop is configured to receive at least a portion of the third nitrogen-enriched stream as a recycle stream, optionally mixed with the nitrogen-enriched stream from the ASU. The second nitrogen-enriched stream and / or the third nitrogen-enriched stream from the ammonia fuel cell are high-purity nitrogen (e.g., greater than 95%, greater than 98%, or greater than 99%). This allows for nitrogen recycling, reducing the need for an air separation unit. Furthermore, by locating the nitrogen storage unit so that it can provide a nitrogen-enriched stream directly to the ammonia loop without delay, ammonia production efficiency can be improved when the ASU is operating at full capacity under conditions of excess renewable energy.

[0025] In one embodiment, the ammonia fuel cell is configured to provide a second water-rich stream, and the first electrolysis unit is configured to receive at least a portion of the second water-rich stream from the ammonia fuel cell as a recycle stream, optionally mixed with the first water-rich stream. In some embodiments, the system further comprises a water storage unit configured to receive and store at least a portion of the second water-rich stream from the ammonia fuel cell and output a third water-rich stream, and the first electrolysis unit is configured to receive at least a portion of the third water-rich stream as a recycle stream, optionally mixed with the first water-rich stream. The second and / or third water-rich streams from the ammonia fuel cell are optionally high-purity (e.g., greater than 98%, or greater than 99.999%) water or steam and excess ammonia. In this manner, this embodiment allows for the recycling of already high-purity water, reducing the amount of first water-rich feed required to supply the first electrolysis unit. Furthermore, by positioning the water storage unit so that it can provide a water-enriched stream (already of high purity) directly to the first electrolysis unit, further flexibility in water supply is achieved.

[0026] In one embodiment, the system includes both a nitrogen storage unit and a water storage unit, the ammonia loop is configured to receive a portion of the third nitrogen-enriched stream from the nitrogen storage unit as a recycle stream, and the first electrolysis unit is configured to receive a portion of the third water-enriched stream from the water storage unit as a recycle stream. The configuration of these storage units provides a recycled water-enriched stream and a high purity recycled nitrogen-enriched stream, providing flexibility in the power balance system and allowing for efficient ammonia production during times of excess renewable power.

[0027] The power balancing system is configured to feed the power flow from the ammonia fuel cell to a power grid. The feedback of power to the power grid enables the balancing of power through the production, storage, and conversion of ammonia to electricity. In certain embodiments, the power flow output from the ammonia fuel cell is configured to increase in response to a decrease in the supply of renewable electricity. More specifically, the power flow output from the ammonia fuel cell is configured to increase if the supply of renewable electricity to the ASU and / or the first electrolysis unit is decreased. In one aspect, the increase in power output from the ammonia fuel cell is provided by an increase in the output of the second ammonia-rich stream from the ammonia storage unit. Thus, the power balancing system is configured to generate electricity using ammonia when energy demand is higher than the amount of energy provided by the renewable electricity.

[0028] The system may further comprise a power conditioning section arranged between the renewable energy supply and the first electrolysis unit, the power conditioning section being arranged to route surplus power from the renewable energy supply and the first electrolysis unit, for example when supply exceeds demand on the power grid.

[0029] A method for balancing power in a power balancing system is also provided. Generally, the method includes the steps of: - feeding the air feed and a first portion of the renewable electricity supply to an air separation unit (ASU) and outputting a nitrogen-enriched stream; - feeding the water-enriched feed and a second portion of the renewable electricity supply to a first electrolysis unit and outputting a hydrogen-enriched stream; - feeding the nitrogen-enriched stream from the ASU and the hydrogen-enriched stream from the first electrolysis unit to an ammonia loop and outputting a first ammonia-enriched vapor stream; - feeding a portion of the first ammonia-rich stream to an ammonia storage unit and outputting a second ammonia-rich stream; - supplying at least a portion of the second ammonia-rich stream from the ammonia storage unit to an ammonia fuel cell to output an electrical power stream; - supplying the power flow from the ammonia fuel cell to a power grid.

[0030] All details of the inventive system apply mutatis mutandis to the method of the present invention. For example, the method suitably includes increasing the power flow provided by the ammonia fuel cell in response to a decrease in the renewable electricity supply, e.g., the supply to the ASU and / or the first electrolysis unit. As above, the increase in power flow can be provided by increasing the output of the second ammonia-rich stream from the ammonia storage unit.

[0031] In certain embodiments, the system includes an oxidant feed and one or more SOFCs in an ammonia fuel cell, and the method includes supplying an oxidant feed to the ammonia fuel cell, the oxidant feed being an oxygen-enriched feed, for example, a high purity (>98% or >99%) oxygen feed or oxygen-enriched air (O2 >21%) or air feed.

[0032] In one form, the method includes providing a second nitrogen-enriched stream from the ammonia fuel cell, optionally mixed with a nitrogen-enriched stream from an ASU, and supplying at least a portion of the second nitrogen-enriched stream to an ammonia loop as a recycle stream. Additionally or alternatively, the method includes providing a second nitrogen-enriched stream from the ammonia fuel cell, supplying at least a portion of the second nitrogen-enriched stream to a nitrogen storage unit, providing a third nitrogen-enriched stream from the nitrogen storage unit, and supplying at least a portion of the third nitrogen-enriched stream to an ammonia loop, optionally mixed with a nitrogen-enriched stream from an ASU, as a recycle stream.

[0033] In certain embodiments, the system includes a nitrogen storage unit, and the method includes supplying at least a portion of the third nitrogen-enriched stream from the nitrogen storage unit to an ammonia loop when the first portion of the supply of renewable electricity exceeds a predetermined threshold. The threshold is the power consumption when the air separation unit (ASU), the first electrolysis unit, and the ammonia loop are operating at minimum capacity, the minimum capacity being <30% (less than 30%) or <10% (less than 10%) of maximum capacity. The method steps enable optimized production of ammonia when renewable electricity exceeds energy demand.

[0034] In one form, the method includes providing a second water-rich stream from the ammonia fuel cell and supplying at least a portion of the second water-rich stream to a first electrolysis unit, optionally combined with the first water-rich stream, as a recycle stream. Additionally or alternatively, the method includes providing a second water-rich stream from the ammonia fuel cell, supplying at least a portion of the second water-rich stream to a water storage unit, and providing a third water-rich stream from the water storage unit and supplying at least a portion of the third water-rich stream to the first electrolysis unit, optionally combined with the first water-rich stream, as a recycle stream.

[0035] In certain embodiments, the method includes supplying at least a portion of the third water-rich stream from the water storage unit to the first electrolysis unit when the second portion of the supply of renewable electricity exceeds a predetermined threshold.

[0036] Specific Embodiments The power conditioning section (9) receives the renewable electricity (3) and exchanges at least a portion of the renewable electricity (91) with the power grid (90) so as to supply the power grid with the electricity required by the consumers. The power conditioning section (9) sends the surplus electricity to a power balancing system (100). In a first specific embodiment example, the power balancing system (100) is described as follows (see FIG. 1):

[0037] An air separation unit (ASU) (10) receives an air feed (1) and a first portion (3a) of the renewable electricity supply (3) and outputs a nitrogen-rich stream (11). A first electrolysis unit (20) receives a first water-rich feedstock (2) and a second portion (3b) of the renewable electricity supply (3) and outputs a hydrogen-rich stream (21). The nitrogen-rich stream (11) and the hydrogen-rich stream (21) are fed to an ammonia loop (30), which outputs a first ammonia-rich stream (31). An ammonia storage unit (40) receives and stores the first ammonia-rich stream (31). Optionally, the ammonia storage unit (40) outputs a second ammonia-rich stream (41), which is then received by an ammonia fuel cell (50). The ammonia fuel cell (50) outputs a power stream (51), which is fed to a power grid (90). An increase in the output of the second ammonia-rich stream (41) from the ammonia storage unit (40) is triggered in response to a decline in the renewable electricity supply (3), thereby enabling the production of electricity from ammonia by generating electricity directly from ammonia in a fuel cell when there is a shortage of renewable electricity relative to the electricity consumption of the power grid.

[0038] In an example embodiment, the power balance system (100) is further developed as shown in Figure 2. In addition to what is described in the first example embodiment, an ammonia fuel cell (50) receives an oxidant feed (4) and outputs a power stream (51), a second nitrogen-rich stream (52), and a second water-rich stream (53). The ammonia loop (30) receives at least a portion of the second nitrogen-rich stream (52) from the ammonia fuel cell (50) as a recycle stream, optionally mixed with the nitrogen-rich stream (11) from the ASU (10). The first electrolysis unit (20) receives at least a portion of the second water-rich stream (53) from the ammonia fuel cell (50) as a recycle stream, optionally mixed with the first water-rich stream (2).

[0039] 3, the power balancing system (100) further includes a nitrogen storage unit (60) and a water storage unit (70). The nitrogen storage unit (60) receives at least a portion of the second nitrogen-rich stream (52) from the ammonia fuel cell (50) and optionally outputs a third nitrogen-rich stream (61), which is optionally mixed with the nitrogen-rich stream (11) from the ASU (10) and supplied as a recycle stream to the ammonia loop (30). Similarly, the water storage unit (70) receives at least a portion of the second water-rich stream (53) from the ammonia fuel cell (50) and optionally outputs a third water-rich stream (71), which is optionally mixed with the first water-rich stream (2) and supplied as a recycle stream to the first electrolysis unit (20).

[0040] While the present invention has been described with reference to several examples and aspects, the overall scope of the invention is defined by the appended claims. Those skilled in the art can combine the example embodiments and aspects as needed within the scope of the present invention. All documents mentioned herein are incorporated by reference.

Claims

1. In a power balancing system (100), - air supply (1), a first water-enriched feed (2), - Renewable electricity supply (3), - Air Separation Unit (ASU) (10), a first electrolysis unit (20), - ammonia loop (30), an ammonia storage unit (40), ammonia fuel cells (50), A power balancing system (100) comprising: - said air separation unit, ASU (10), arranged to receive said air feed (1) and a first portion (3a) of said renewable electricity supply (3) and to output a nitrogen-enriched stream (11); - said first electrolysis unit (20) is arranged to receive said first water-enriched feed (2) and a second component (3b) of said renewable electricity supply (3) and to output a hydrogen-enriched stream (21); the ammonia loop (30) is arranged to receive the nitrogen-rich stream (11) from the ASU (10) and the hydrogen-rich stream (21) from the first electrolysis unit (20) and to output a first ammonia-rich stream (31); - said ammonia storage unit (40) is arranged to receive and store at least a portion of said first ammonia-rich stream (31); and to output a second ammonia-rich stream (41); - said ammonia fuel cell (50) is arranged to receive at least a portion of said second ammonia-rich stream (41) from said ammonia storage unit (40) and to output an electrical power stream (51); wherein said power balancing system is arranged to supply said power flow (51) from said ammonia fuel cell (50) to a power grid (90); The power balancing system (100).

2. 2. The system (100) of claim 1, wherein the power flow (51) output from the ammonia fuel cell (50) is arranged to increase in response to a decrease in the supply of renewable electricity (3).

3. 3. The system (100) of claim 2, wherein the power flow (51) output from the ammonia fuel cell (50) is arranged to increase in response to a decrease in the supply of the renewable electricity (3) to the ASU (10) and / or the first electrolysis unit (20).

4. 4. The system (100) of claim 2, wherein the increase in the electrical power flow (51) output from the ammonia fuel cell (50) is provided by increasing the output of the second ammonia-rich stream (41) from the ammonia storage unit (40).

5. The system (100) of any one of claims 1 to 4, wherein the ammonia fuel cell (50) comprises one or more solid oxide fuel cells (SOFCs), such as one or more oxygen-ion conducting SOFCs (SOFC-O), one or more proton conducting SOFCs (PC-SOFC), or one or more direct ammonia fuel cells (DAFC), preferably the ammonia fuel cell comprises one or more SOFC-O.

6. The system further comprises an oxidant feed (4), which may be an oxygen-enriched feed, such as a high purity (>98% or >99%) oxygen feed or oxygen-enriched air (O ２ 6. The system (100) of claim 5, wherein the feed is an ammonia fuel cell feed of at least 100 wt % or more than 21% by mass, or an air feed, the feed being arranged to be fed to the ammonia fuel cell.

7. 7. The system (100) of any one of claims 1 to 6, wherein the ammonia fuel cell (50) is configured to provide a second nitrogen-enriched stream (52), and the ammonia loop (30) is configured to receive at least a portion of the second nitrogen-enriched stream (52) from the ammonia fuel cell (50) as a recycle stream, optionally in combination with the nitrogen-enriched stream (11) from the ASU (10).

8. 8. The system (100) of any one of claims 1 to 7, further comprising a nitrogen storage unit (60) arranged to receive and store at least a portion of the second nitrogen-enriched stream (52) from the ammonia fuel cell (50) and output a third nitrogen-enriched stream (61), and the ammonia loop (30) is arranged to receive at least a portion of the third nitrogen-enriched stream (61) as a recycle stream, optionally in combination with the nitrogen-enriched stream (11) from the ASU (10).

9. 9. The system (100) of any one of claims 1 to 8, wherein the ammonia fuel cell (50) is arranged to provide a second water-rich stream (53), and the first electrolysis unit (20) is arranged to receive at least a portion of the second water-rich stream (53) from the ammonia fuel cell (50) as a recycle stream, optionally in combination with the first water-rich stream (2).

10. 10. The system (100) of any one of claims 1 to 9, wherein the system further comprises a water storage unit (70) arranged to receive and store at least a portion of the second water-rich stream (53) from the ammonia fuel cell (50) and to output a third water-rich stream (71), wherein the first electrolysis unit (20) is arranged to receive at least a portion of the third water-rich stream (71) as a recycle stream, optionally in combination with the first water-rich stream (2).

11. A method for balancing power in a power balancing system (100) according to any one of claims 1 to 10, comprising the steps of: - feeding said air feed (1) and a first portion of said renewable electricity supply (3a) to said air separation unit, ASU (10), outputting a nitrogen-enriched stream (11); - feeding the water-enriched feed (2) and a second portion of said renewable electricity supply (3b) to said first electrolysis unit (20) and outputting a hydrogen-enriched stream (21); - feeding the nitrogen-rich stream (11) from the ASU (10) and the hydrogen-rich stream (21) from the first electrolysis unit (20) into the ammonia loop (30) to output a first ammonia-rich stream (31); - feeding at least a portion of said first ammonia-rich stream (31) to said ammonia storage unit (40) and outputting a second ammonia-rich stream (41); - feeding at least a portion of said second ammonia-rich stream (41) from said ammonia storage unit (40) to said ammonia fuel cell (50) to output an electrical power stream (51); - feeding said power flow (51) from said ammonia fuel cell (50) into a power grid (90).

12. 12. The method of claim 11, wherein the power flow (51) delivered from the ammonia fuel cell (50) increases in response to a decrease in the renewable electricity supply (3), e.g., a decrease in the renewable electricity supply to the ASU (10) and / or the first electrolysis unit (20).

13. The method of claim 11 or 12, wherein the increase in power flow (51) is provided by increasing the output of the second ammonia-rich stream (41) from the ammonia storage unit (40).

14. The system includes an oxidant feed (4) and one or more SOFCs disposed in an ammonia fuel cell (50), and the method includes supplying the oxidant feed (4) to the ammonia fuel cell, the oxidant feed (4) being an oxygen-enriched feed, for example, a high purity (>98% or >99%) oxygen feed or oxygen-enriched air (O ２ 14. The method according to any one of claims 11 to 13, wherein the feed is an air feed.

15. 15. The method of any one of claims 11 to 14, wherein the method comprises providing a second nitrogen-enriched stream (52) from the ammonia fuel cell (50) and feeding at least a portion of the second nitrogen-enriched stream (52) to the ammonia loop (30) as a recycle stream, optionally in combination with the nitrogen-enriched stream (11) from the ASU (10).

16. 16. The method of any one of claims 11 to 15, wherein the method includes providing a second nitrogen-enriched stream (52) from the ammonia fuel cell (50) and feeding at least a portion of the second nitrogen-enriched stream (52) to a nitrogen storage unit (60), and providing a third nitrogen-enriched stream (61) from the nitrogen storage unit (60) and feeding at least a portion of the third nitrogen-enriched stream (61) to the ammonia loop (30) as a recycle stream, optionally in combination with the nitrogen-enriched stream (11) from the ASU (10).

17. 17. The method of claim 16, wherein the method comprises supplying at least a portion of the third nitrogen-enriched stream (61) from the nitrogen storage unit (60) to the ammonia loop (30) when the first portion (3a) of the renewable electricity supply exceeds a predetermined threshold.

18. 18. The method of any one of claims 11 to 17, wherein the method comprises providing the second water-rich stream (53) from the ammonia fuel cell (50) and feeding at least a portion of the second water-rich stream (53) to the first electrolysis unit (20) as a recycle stream, optionally in combination with the first water-rich stream (2).

19. 19. The method of any one of claims 11 to 18, wherein the method comprises providing the second water-rich stream (53) from the ammonia fuel cell (50) and feeding at least a portion of the second water-rich stream (53) to the water storage unit (70), and providing a third water-rich stream (71) from the water storage unit (70) and feeding at least a portion of the third water-rich stream (71) to the first electrolysis unit (20) as a recycle stream, optionally in combination with the first water-rich stream (2).

20. 20. The method of claim 19, wherein the method comprises supplying at least a portion of the third water-rich stream (71) from the water storage unit (70) to the first electrolysis unit (20) when the second portion (3b) of the supply of renewable electricity exceeds a predetermined threshold.

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