1 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION Exporting renewable hydrogen via offshore ammonia synthesis The following statement is a full description of this invention, including the best method of performing it as known to me: 2 Exporting renewable hydrogen via offshore ammonia synthesis FIELD OF THE INVENTION (01) The present invention relates broadly to a method of using offshore ammonia synthesis, storage and offloading platforms to export renewably generated hydrogen in the form of ammonia. BACKGROUND TO THE INVENTION (02) In recent years there has been an expansion of interest and knowledge in the use of offshore platforms, both floating and fixed rig, to undertake various processes in the oil and gas industry including the floating production, storage and offloading of oil (FPSO) and the floating liquefaction of natural gas (FLNG). (03) In recent years there has also been an expansion of knowledge and interest in using ammonia (NH 3 ) as a vector to transport zero emission hydrogen (H 2 ) where such hydrogen is generated via the electrolysis of water powered by renewable energy such as solar, tidal, wind or geothermal energy. (04) Hydrogen once generated, whether from renewable energy sources or from fossil fuel sources such as methane or coal, can be combined with nitrogen in a chemical synthesis plant, such as the Haber Bosch (HB) process, to produce ammonia. (05) In recent years, as an alternative to HB, interest has grown in a process known as solid state ammonia synthesis (SSAS), which combines the electrolysis step (to produce hydrogen) with the synthesis step (of combining the nitrogen and hydrogen to produce ammonia) into a single process. (06) By combining the electrolysis and synthesis step into a single process, SSAS offers prospects of being up to 30% more efficient in terms of its energy use than the more traditional electrolysis plus Haber Bosch process. (07) By Innovation Patent number 2014100635 an invention was disclosed via which a floating ammonia production vessel was fed renewably generated hydrogen (or renewably generated hydrogen and nitrogen) from a shore based gas generating facility. (08) The present invention is differentiated from that in Innovation Patent 2014100635 in that it is renewably generated electricity (rather than hydrogen and/or nitrogen gases) which is transported from shore to the offshore platform.
3 (09) In the present invention a water desalination unit, an air separation unit (to generate the nitrogen), a plant to spilt hydrogen from water and a plant to synthesise ammonia by combining nitrogen and hydrogen, are all located on board the offshore platform and the energy to run these processes is brought to the offshore platform via high voltage cables which transmit electricity which has been generated on-shore from renewable sources such as solar, wind, tidal or geothermal energy. (10) The offshore platform will also accommodate ammonia storage tanks which will hold the ammonia produced on board until such time as it could be offloaded into an ammonia transport ship tanker which berths alongside. (11) In one embodiment of the invention the offshore platform accommodates a separate electrolysis unit to split hydrogen from water and a separate Haber Bosch unit to synthesise ammonia by combining nitrogen and hydrogen. (12) In another embodiment of the invention the offshore platform accommodates a solid state ammonia synthesis plant which combines the hydrogen splitting function and the ammonia synthesis function into a single plant, thereby removing the need for a separate on board electrolysis plant (13) For "stranded" renewable energy seeking an export market, a logistics chain utilising ammonia synthesis on an offshore platform as described herein can overcome distance issues, provide short term storage and can promote efficiencies by combining both the ammonia synthesis function and the port offloading function into a single, conveniently located asset. SUMMARY OF THE INVENTION (14) According to one aspect of the present invention there is provided a method of exporting renewably generated hydrogen via offshore ammonia synthesis, by: a. Producing electricity on-shore from a source of renewable energy such as solar, tidal, wind or geothermal power; and b. Transmitting this renewably generated electricity via high voltage cable to an offshore platform; and c. Accommodating on such offshore platform a water desalination plant, an electrolysis plant, a nitrogen production plant and a Haber Bosch ammonia synthesis plant, the power for all of which would be provided by the renewably generated electricity which has been transmitted from the shore to the offshore platform; and d. Harnessing the offshore platform's water desalination plant, electrolysis plant, nitrogen production plant and Haber Bosch ammonia synthesis plant to enable the on-board roduction of ammonia which would then be stored 4 on-board pending offloading into ammonia transport ships which can berth alongside. (15) According to another aspect of the present invention there is provided a method of exporting renewably generated hydrogen via offshore ammonia synthesis, by: a. Producing electricity on-shore from a source of renewable energy such as solar, tidal, wind or geothermal power; and b. Transmitting this renewably generated electricity via high voltage cable to an offshore platform; and c. Accommodating on such offshore platform a water desalination plant, a nitrogen production plant and a solid state ammonia synthesis plant, the power for all of which would be provided by the renewably generated electricity which has been transmitted from the shore to the offshore platform; and d. Harnessing the offshore platform's water desalination plant, nitrogen production plant and solid state ammonia synthesis plant to enable the on board production of ammonia which would then be stored on-board pending offloading into ammonia transport ships which can berth alongside. BRIEF DESCRIPTION OF THE FIGURES (16) In order to achieve a better understanding of the nature of the present invention a preferred embodiment of a method of exporting renewable hydrogen via offshore ammonia synthesis will now be described, by way of example only, with reference to the accompanying drawings in which: (17) Figure 1 is a schematic view of one method of exporting renewable hydrogen via offshore ammonia synthesis in which an offshore platform contains both an electrolysis unit and a Haber Bosch ammonia synthesis unit. (18) Figure 2 is a schematic view of another method of exporting renewable hydrogen via offshore ammonia synthesis in which an offshore platform does not contain a separate electrolysis unit and a separate Haber Bosch ammonia synthesis unit but combines these functions by containing a solid state ammonia synthesis unit.
5 DETAILED DESCRIPTION OF THE PREFERRED EMBODIEMET (19) Figure 1 depicts one method of exporting renewable hydrogen via offshore ammonia synthesis involving the following steps: a. Producing electricity on-shore from a source of renewable energy such as solar, tidal, wind or geothermal power 1 ; and b. Transmitting this renewably generated electricity via high voltage cable 2, to an offshore platform 3; and c. Accommodating on such offshore platform a water desalination plant 4, an electrolysis plant 5, a nitrogen production plant 6 and a Haber Bosch ammonia synthesis plant 7, the power for all of which would be provided by the renewable electricity generation plant 1, the electricity from which has been transmitted from the shore to the offshore platform via a high voltage cable 2; and d. Harnessing the offshore platform's water desalination plant 4, electrolysis plant 5, nitrogen production plant 6 and Haber Bosch ammonia synthesis plant 7 to enable the on-board production of ammonia which would then be stored in on-board holding tanks 8, pending offloading into ammonia transport ships which can berth alongside. (20) Figure 2 depicts another method of exporting renewable hydrogen via offshore ammonia synthesis involving the following steps: a. Producing electricity on-shore from a source of renewable energy such as solar, tidal, wind or geothermal power 1 ; and b. Transmitting this renewably generated electricity via high voltage cable 2, to an offshore platform 3; and c. Accommodating on such offshore platform a water desalination plant 4, a nitrogen production plant 5 and a solid state ammonia synthesis plant 6, the power for all of which would be provided by the renewable electricity generation plant 1, the electricity from which has been transmitted from the shore to the offshore platform via a high voltage cable 2; and d. Harnessing the offshore platform's water desalination plant 4, nitrogen production plant 5 and solid state ammonia synthesis plant 6, to enable the on-board production of ammonia which would then be stored in on-board holding tanks 7, pending offloading into ammonia transport ships which can berth alongside.
6 (21) Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. For example, the offshore platform could be a permanent rig anchored to the sea bed or it could be a floating vessel. In another example, the ammonia synthesis plant may be able to operate directly with air and water and not require a either separate nitrogen production plant or a separate electrolysis plant. (22) All such variations are to be considered within the scope of the present invention, the nature of which is to be determined from the foregoing description.