A method of transporting hydrogen

Abstract

A method of transporting hydrogen comprising: forming an alcohol from hydrogen and carbon dioxide; transporting said alcohol; breaking down said alcohol to form carbon dioxide and hydrogen; using said hydrogen as a fuel; and capturing said carbon dioxide to transport for reuse in generating more alcohol.

Description

[0001] A METHOD OF TRANSPORTNG HYDROGEN

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a method of transporting hydrogen, to a method of propelling a vehicle, to a method of creating and transporting a fuel and to a vehicle and relates particularly, but not exclusively, to a mechanism for using renewably sourced electricity to power vehicles or other energy hungry technologies, such as data centres, factories or housing.

[0004] BACKGROUND OF THE INVENTION

[0005] Manifested from an urgent requirement to address climate change, methods of generating renewable energy and reducing societies need for fossil fuels is on the increase. Typical methods include the use of hydrogen or methane as a fuel source.

[0006] The generation and transportation of hydrogen for fuel is a known concept. Hydrogen can be generated through various methods, such as electrolysis or biomass conversion. Involving the decomposition of organic materials, biomass conversion uses processes such as gasification or pyrolysis to extract hydrogen-rich gases. Electrolysis utilises electricity to split water molecules into hydrogen and oxygen and then isolating the hydrogen for collection. Typically, the electricity used by the electrolysis process can be generated through renewable means for example, wind turbines or solar power. This isolated hydrogen can then be used as a fuel in various ways due to its clean combustion properties and versatility. One example of using hydrogen as a fuel or energy source is via hydrogen fuel cells. Hydrogen fuel cells work through an electrochemical process by combining hydrogen and oxygen without combustion that generates electricity, heat, and water. The electricity produced by the fuel cells can be used to power electric vehicles such as cars, boats and lorries and provide zero-emission alternative to internal combustion engines. When transporting hydrogen, it is common practice to use compression or liquefaction to increase the energy density. It is also common to combine it with CO2 to form with alcohols molecules, such as methanol.

[0007] Green methanol, also known renewable methanol, is a sustainable and environmentally friendly variant of conventional methanol. It is known as biomethanol if produced from renewable sources such as biomass using the process of gasification or pyrolysis. It is known as e-methanol if it is synthesised directly from hydrogen and CO2. For e-methanol to be green, both the H2 and CO2 need to be from green sources. The green H2 can be made through processes such as electrolysis using renewable energy inputs. The green CO2 can be sourced from biomass or direct air capture machines. This sustainable production distinguishes it from traditional methanol, which is typically derived from steam reformation of natural gas (a fossil fuel).

[0008] Green methanol is a clean fuel and a versatile chemical feedstock. It can be used in various sectors, including transportation, energy storage, and chemical manufacturing. As a fuel, it can power vehicles directly or be blended with diesel or petrol, reducing greenhouse gas emissions and contributing to cleaner air quality. Moreover, its role in energy storage and as a raw material for chemical synthesis offers a pathway towards decarbonizing industries that heavily rely on fossil fuels. This renewable form of methanol plays a crucial role in the transition to a more sustainable and low-carbon economy, offering a viable alternative to conventional methanol derived from non-renewable sources.

[0009] Biogenic and direct air captured supplies of CO2 will be severely constrained in comparison to the quantity of fossil fuels that need to be displaced. Prior art refers to ‘linear’ systems that will therefore not be considered as a scalable zero emission fuel in 2050.

[0010] Preferred embodiments of the present invention seek to overcome or alleviate the above described disadvantages of the prior art.

[0011] SUMMARY OF THE INVENTION According to an aspect of the present invention there is provided a method of transporting hydrogen comprising: forming an alcohol from hydrogen and carbon dioxide; transporting said alcohol; breaking down said alcohol to form carbon dioxide and hydrogen; using said hydrogen as a fuel; and capturing said carbon dioxide to transport for reuse in generating more alcohol.

[0012] Capturing carbon dioxide (CO2) offers several advantages, both in environmental and economic terms. CO2 is a major greenhouse gas contributing to global warming and climate change. By capturing CO2 emissions, industries can significantly reduce their carbon footprint and prevent the release of this greenhouse gas into the atmosphere. Moreover, this captured CO2 is being reused in the synthesis process with hydrogen to generate more alcohol, preventing any future problems with it being released back into the atmosphere. That is, although carbon is used in the production of the alcohol, this carbon is captured, recycled and reused in a loop without significant loss of carbon at any stage of the process. As a result, a so-called “carbon loop” is created utilising carbon without adding to the atmospheric discharge of carbon dioxide. Furthermore, capture of the carbon dioxide in combustion process is complex due to the presence of water vapour, NOx and in the case of dual fuel engines, SOx and particulate materials and typically results in a 60 to 80% capture rate. However, in the present invention, the use of pre-combustion carbon dioxide capture using reformers has a 100% capture rate of pure CO2.

[0013] In a preferred embodiment the alcohol is formed in a synthesis plant and said captured carbon dioxide is transported to said synthesis plant or a different synthesis plant.

[0014] Preferably the alcohol is transported in at least one tank, the captured carbon dioxide from the subsequent breaking down of the alcohol being subsequently transported in the same tank once said alcohol has been emptied therefrom. Preferably the alcohol is chilled prior to delivery into said at least one tank, prior to transportation.

[0015] By capturing the carbon dioxide and returning it to the synthesis plant in the same storage tanks that delivered the alcohol offers many advantages. Firstly, it sets up a circular carbon dioxide economy that avoids future supply constraints of green carbon dioxide. Secondly, it optimizes logistical efficiency by maximising the use of existing infrastructure, particularly where the energy produced by the method of the present invention is used to power a marine vessel. Existing infrastructure may be used to refuel (bunker) the vessel, e.g. an existing ro-ro vehicle ramp for trailers or lo-lo shore crane for container handling. This means that a port authority is not required to make fresh additional investment into bunkering equipment, such as static tanks, pumps, pipes, hoses, hose gantries, power supplies, access, security fencing, hazardous areas, etc., which could be a significant financial obstacle to making progress in a project.

[0016] By employing the same storage tanks for both carbon dioxide and alcohol, the transportation processes is simplified by reducing the need for additional equipment and separate transport systems. Thirdly, it reduces the number of tanks required for the transportation of alcohol and carbon dioxide, thus, reducing the costs of required equipment further and reducing the weight and space occupied by storage tanks.

[0017] In a further preferred embodiment, the alcohol is chilled and said carbon dioxide is liquefied.

[0018] When the alcohol has been chilled prior to transportation, the cold energy contained in the alcohol is partially transferred from the alcohol to the respective storage tank and thereby removes the need to initially chill the storage tank using vaporisation of liquid CO2, which would add to boil-off and associated electrical energy required for re-liquefaction. This process conserves cold thermal energy within the storage tanks when transferring between alcohol use to carbon dioxide use. This reduces the power consumption of an electrically driven CO2 re-liquefier that would otherwise be required to chill the tank to liquid CO2 temperature from ambient temperature. Furthermore, the transfer of cold energy from chilled alcohol to compressed CO2 will bring about CO2 liquefaction with little or no need to use additional electrical power. This decreases the associated manufacture and operational costs for the CO2 liquefier. Additionally, liquefying the captured CO2 greatly increases the bulk density for storage and transportation of the carbon dioxide. By using chilling in addition to compression of CO2 the inventors provide the opportunity to super-chill the alcohol at its point of production so that the ‘cold energy’ delivered with the alcohol in the storage tanks can be used to offset the amount of parasitic electricity required at the point of use of the hydrogen to carry out the CO2 liquefaction, thereby improving efficiency, reducing cost of captured CO2 and in turn reducing levelised cost of alcohol production.

[0019] In a preferred embodiment, liquefying the carbon dioxide includes passing the chilled alcohol and the carbon dioxide through a counter-flow or crossflow heat exchanger.

[0020] In another preferred embodiment, the heat exchanger may contain a phase change material in the heat transfer pathway between the warming methanol and chilling CO2.

[0021] By including a phase change material, such as organic, or inorganic or eutectic phase change material, as a thermal barrier in the heat exchanger, an advantage is provided that the impact of the cold energy from the chilled alcohol is dampened, meaning that the carbon dioxide will be chilled to the desired liquid temperatures and not chilled so quickly as to result in the forming of solid carbon dioxide (dry ice) which would otherwise cause significant problems.

[0022] In one embodiment the energy is used for the propulsion of a vehicle, more preferably a marine vessel. Alternatively the energy may be used to power computing facilities, such as data centres, or for powering factories, housing or other energy hungry facilities, or for powering plant or vehicles on a construction site.

[0023] In another preferred embodiment, the carbon dioxide is captured within a reformer. In a preferred embodiment the alcohol comprises methanol.

[0024] By capturing the carbon dioxide in a reformer and returning it to the methanol synthesis plant (circular economy) there is significantly less requirement for additional carbon dioxide in the synthesis plant.

[0025] By super-chilling the methanol at the on-shore methanol synthesis plant, to a temperature as low as -90QC, which is still above the methanol freezing point of - 97.6QC, allows a significant quantity of cold energy to be transferred to the vessel to be used for the purpose of liquefying CO2. The super-chilling is carried out at the same time as the methanol is being synthesised, which is when renewable energy is available, so that the electrical load associated with super chilling is contributing to the overall Power-to-X purpose of avoiding curtailment of wind farms. Superchilling onshore with renewable energy conserves the use of electrical power on board the vessel or onsite.

[0026] In a further preferred embodiment, the methanol may be mixed with water. Mixing the methanol with water is beneficial for a number of reasons. Firstly, blending the methanol with water allows for precise control over the reactants' concentrations, thus ensuring the desired ratio before their entry into the reformer. Additionally, the water acts as a regulator during the reforming process and therefore moderates the temperatures within the reformer. This moderation is crucial in averting excessive temperatures that could otherwise detrimentally affect the catalyst or disrupt the reaction equilibrium.

[0027] In an additional preferred embodiment, the hydrogen may be used in hydrogen fuel cells.

[0028] The use of hydrogen fuel cells and reformers is a more efficient use of methanol than combustion. Furthermore, combustion is not a so-called “zero emission” process because NOx is produced, whereas reforming with carbon (dioxide) capture is zero emission. In an alternative preferred embodiment, at least a portion of the water formed from the hydrogen fuel cells may be mixed with the methanol.

[0029] When water produced in the fuel cells is fed back and mixed with the methanol supplied to the reformer, 30% to 40% more hydrogen is formed than from methanol alone. The water produced in the fuel cells is more than the quantity needed for reaction of carbon monoxide to carbon dioxide.

[0030] In another aspect of the present invention there is provided a method of propelling a vehicle comprising: receiving alcohol formed as part of the method set out above; and using said hydrogen to fuel said vehicle.

[0031] In a preferred embodiment of the present invention the vehicle is a marine vessel.

[0032] In another preferred embodiment the hydrogen may be used in fuel cells, for example proton exchange membrane fuel cells.

[0033] In a further aspect of the present invention there is provided a method of creating and transporting a fuel comprising: splitting water to create hydrogen; and forming alcohol from said hydrogen and carbon dioxide.

[0034] In a preferred embodiment of the present invention the hydrogen is synthesised through electrolysis and electricity is used for said electrolysis.

[0035] In another preferred embodiment the electricity is generated by renewable means.

[0036] In an additional aspect of the present invention there is provided a vehicle comprising: at least one storage tank containing alcohol; a reformer for splitting said alcohol into hydrogen and carbon dioxide; at least one hydrogen fuel cell for generating energy from said hydrogen; propulsion means for propelling said vehicle using said generated energy; and carbon dioxide capturing means for capturing said carbon dioxide wherein said at least one storage tank is used to store said carbon dioxide after being emptied of alcohol.

[0037] In a preferred embodiment of the present invention the means for capturing said carbon dioxide occurs in said reformer.

[0038] In another preferred embodiment said vehicle comprises a marine vessel and the propulsion means comprises one or more thrusters or propellers.

[0039] In a further preferred embodiment, the alcohol is methanol.

[0040] The following problems, with their associated solutions, are addressed by the invention of this application.

[0041] Main problem: The IMO (International Maritime Organisation) has set a significant advance decarbonisation milestone of “at least 5% Scalable Zero Emission Fuel (SZEF) use by 2030.” The word ‘Scalable’ means ‘having the potential to be produced at the volumes necessary to meet a significant amount of global maritime demand.’

[0042] Candidate SZEFs are: battery electric, compressed or liquefied green hydrogen, green methanol and green ammonia. Of these, conventional ‘linear’ green methanol is unlikely to be sufficiently scalable given the anticipated future constraints in supply of green CO2 from biological and Direct Air Capture sources. This would cause green methanol to be removed from the list of candidate SZEFs and consequently to lose support as part of the 5% target.

[0043] Associated Problem 1 : Captured CO2 is liquefied on board the vessel to greatly increase the bulk density for storage and transportation. In order to conserve energy, this is achieved in part by utilising the cold thermal energy contained in the delivered methanol in a heat exchanger. There is a risk that the CO2 liquefaction process conditions could deviate to the point where solid CO2 (dry ice) is formed. This would be detrimental to continued flow patterns in the system. Associated Problem 2: When tanks of liquid CO2 are agitated during heavy weather conditions (sloshing) there would be an increase in partial pressure that causes boil- off back to the gaseous form. This could cause significant losses of product to atmosphere due to activation of pressure relief valves and reduce the effectiveness of the circular CO2 model.

[0044] Associated problem 3: Filling ambient temperature ISO tanks with cold liquid CO2 at -20 °C will cause large amounts of boil-off until the tanks are chilled down.

[0045] Associated problem 4: At the onshore e-methanol plant location, there is a risk that rapid expansion of liquid CO2 to gaseous form would reduce product temperature to the point where dry ice is formed.

[0046] Main Solution: The applicant has an ongoing project that sets out to investigate the feasibility of establishing a ‘NI / GB Green Shipping Corridor’ between Northern Ireland (Larne or Belfast) and the North West of England (Liverpool or Heysham) using a roll-on-roll-off freight ferry design optimised for the carriage of unaccompanied trailers and powered by hydrogen reformed onboard from green methanol delivered in road mobile ISO tanks. The green methanol would be synthesised in the Ports of Larne or Belfast from green H2 and green CO2. The main innovation in the project is to capture CO2 from the onboard reformer and return it to the methanol synthesis plant in the same storage tanks that delivered the methanol, thereby setting up a circular CO2 economy that avoids the inevitable future supply constraint of green CO2. The port based flexible green methanol plant would use otherwise curtailed wind power to drive a large-scale electrolyser that feeds green hydrogen to a catalytic reactor. This Domestic Green Shipping Corridor would have ‘true-zero’ emissions, would not be reliant upon limited supplies of bio derived CO2 or direct air captured CO2 and would not need any carbon offsetting to meet net zero objectives. Consequently, the use of a ‘circular’ CO2 model avoids the risk that linear CO2 constraints will cause green methanol to be removed from the IMO list of scalable zero emission fuels, and in so doing, our solution will provide a disruptive differentiation in the maritime fuels market - indeed it would become a key Enabler of the Green Methanol Economy. Associated Solution 1 : The counter-flow heat exchanger can be designed and specified to incorporate a phase change material barrier in the heat transfer pathway that modulates any temperature excursions that would otherwise occur and so removes the risk of dry ice blockages in pipework.

[0047] Associated Solution 2: The boil-off management system can be designed and specified to incorporate re-liquefaction equipment to remove the risk of product loss from storage.

[0048] Associated Solution 3: The ISO storage tanks can be used to deliver methanol to the vessel at -20 °C and if, when a tank is drained of methanol, can be refilled with liquid CO2 in a timely manner, thereby avoiding increases in boil off.

[0049] Associated Solution 4: An onshore counter-flow heat exchanger can be provided, incorporating a phase change material barrier in the heat transfer pathway that modulates any temperature excursions that would give rise to sudden expansion and formation of dry ice.

[0050] BRIEF DESORPTION OF THE DRAWINGS

[0051] Preferred embodiments of the present invention will now be described, by way of example only, and not in any limitative sense with reference to the accompanying drawings in which:-

[0052] Figure 1 is a flow chart of a method of transporting hydrogen of the present invention;

[0053] Figure 2 is a schematic representation of a portion of the process of figure 1 ;

[0054] Figure 3 is another schematic representation of another portion of the process of figure 1 ;

[0055] Figure 4 is a representation of a chemical process used as part of the process of figure 1 ; and

[0056] Figure 5 is a schematic representation of a vehicle of the present invention.

[0057] DETAILED DESCRIPTION OF THE DRAWINGS With initial reference to figures 1 and 2, a method of transporting hydrogen begins with generating electricity (step 1 ). Figure 2 highlights the processes that include the synthesis of hydrogen and methanol before they arrive at the transported location (for example the vessel of figure 3).

[0058] Preferably this electricity is generated by renewable means, such as on-shore or off-shore wind turbines, as indicated by 10. The renewable electricity is transmitted to a hydrogen synthesis plant (step 2) where hydrogen is formed. At the hydrogen synthesis plant, hydrogen is formed by splitting water by electrolysis. Electrolysis may be achieved by using a proton exchange membrane (PEM) electrolyser. The electrolysers may be powered by the renewable electricity indicated at 12 (step 3).

[0059] Preferably the electrolysers operate on a ‘generation following mode’. In this mode of operation, the electrolyser adjusts its hydrogen production to match the varying supply of renewable energy. This allows the production of certifiably ‘green’ hydrogen. In this case, ‘green’ hydrogen refers to hydrogen produced through a process powered by renewable energy sources, such as solar, wind, hydroelectric, or geothermal energy. The term ‘green’ signifies that the production process does not involve the emission of greenhouse gases or other pollutants, thereby minimising or eliminating the carbon footprint associated with its production.

[0060] Once the required hydrogen has been produced, it can be further processed such as purified, compressed, or liquefied. The hydrogen is then either stored and used in the same synthesis plant, or it is transported to a different synthesis plant. When the hydrogen is being transferred to another plant (step 4) the transportation means can take various forms. For example, the hydrogen can be transported through a sub-sea or terrestrial pipeline, a high pressure tube trailer or by a liquid hydrogen tanker.

[0061] At the methanol synthesis plant the transported ‘green’ hydrogen is combined with carbon dioxide (CO2), through carbon dioxide hydrogenation, to form an alcohol such as methanol (step 5). As indicated by 14, the plant may be flex-methanol synthesis plant. This type of plant generates ‘green’ methanol (CH3OH) (also referred to as E-methanol) to match the hydrogen supplied by the hydrogen synthesis plant indicated at 12. There is therefore no requirement for high pressure H2 compressors or H2 storage, significantly reducing both CAPEX and OPEX.

[0062] Once the methanol has been formed, it may be stored in a holding tank until it is required, as indicated by 16, or the methanol may be immediately prepared for transportation. When the methanol is required for transportation, it may be transferred into an ISO storage tank (step 6). The storage tanks may be based on ISO standards (International Organisation for Standardisation) for carrying liquids in bulk. The methanol may be chilled down to -20 °C at 20 bar to comply with commonly adopted standards for transportation of liquid CO2.

[0063] As indicated by 18, when the methanol is being dispatched for the road transport sector, for example to be used as a fuel or a fuel blend, it may be maintained and transported at ambient temperature and pressure. This process demonstrates a ‘Linear CO2 Economy’ and results in a carbon neutral environmental performance.

[0064] When the methanol is being dispatched to a marine vessel, such as a vehicle transporting ferry, containership or tanker, further preparation of the methanol is required. As indicated by 20 and 22, the methanol is chilled down to conditions in the range of -20 °C (to keep the ISO storage tank inner skin at cryogenic temperature) to -50 'C (to prevent liquid CO2 from solidifying to dry ice) by an electric super chiller. The methanol is then transferred to the storage tanks via vacuum insulated pipes as shown in 24. The methanol can then be sent to a filling station where multiple chilled ISO storage tanks may be filled in parallel, as indicated at 28. Alternatively, the methanol may be individually filled into a respective chilled ISO storage tank and sent for dispatch to a vessel, as indicated at 30. Once within an ISO storage tank, the temperature of the methanol is preferably maintained between -20 °C and -90 °C, as indicated by 26. Note that at temperatures below the triple point of -56.7 'O it is impossible for CO2 to exist in liquid form. Note also that if liquid CO2 at -20 'C at 20bar is added to an ISO tank that has just been emptied of methanol at -50QC, then the liquid CO2 will remain as a liquid and gradually heat the inner skin to -20 °C. If liquid CO2 at -50 °C and 10bar is added to the respective ISO storage tank, then the potential for conservation of cold energy on the vessel can be maximised and the resultant electrical power consumption required for compression and liquefaction of CO2 can be minimised. The chilled methanol may then be delivered to the vessel using ISO storage tanks on trailers. The ISO storage tanks may be stowed at a suitable open-air deck location adjacent to a ‘truck-to-ship’ bunkering station.

[0065] Referring now to figure 3, when the methanol containing storage tanks have arrived on board a vessel, the methanol may be emptied out of the storage tanks. When a transfer hose is connected to a given ISO storage tank, the storage tank effectively becomes part of the ships bunkering and fuel storage system, and as such is required to comply with all relevant maritime regulations. The methanol may be withdrawn from the ISO storage tanks while the ship is moving on its voyage. Note, this is an industry first for both methanol and liquid CO2. Any emptied ISO storage tanks are then ready for further use as a storage container to hold and transport liquid carbon dioxide, when available (see below for further detail).

[0066] The chilled methanol may be transferred to a methanol pre-heater, located on the vessel, as indicated at 32. The primary function of the pre-heater is to start raising the temperature of the methanol before it enters the reformer.

[0067] Next the methanol is preferably mixed with water in a water mixer as shown at 34. Mixing the methanol with water is an desirable step for a number of reasons. Firstly, by pre-mixing methanol with water, the concentration of the reactants can be controlled and adjusted to the desired ratio before entering the reformer. Secondly, the water serves as a moderator in the reforming process by regulating the temperature within the reformer. It also helps prevent excessive temperatures that might negatively impact the catalyst or the reaction equilibrium. The methanol and water mixture is then heated up to 300 °C in a heater as indicated at 36. This process converts the water into steam and the methanol into methanol vapour, with both required to be in their gaseous state for the methanol reformer process.

[0068] As indicated at 38, the methanol gas and steam are transferred to the methanol reformer (step 7) to form carbon dioxide and hydrogen. The primary reaction within the reformer is steam reforming, where the methanol and steam react in the presence of the catalyst. Typically, the catalyst used is based on nickel. Nickel-based catalysts are effective in promoting the steam reforming reaction at elevated temperatures. The steam and methanol mixture is then fed into a tubular reactor where it makes contact with the catalyst inside.

[0069] Additionally referring to figure 4, the process of the reaction in the reformer will be explained in more detail. Firstly the methanol is de-hydrogenated into formaldehyde and hydrogen.

[0070] The formaldehyde is then further decomposed into hydrogen and carbon monoxide with both reactions occurring over the metal catalyst.

[0071] Lastly, due to the presence of water, the carbon monoxide is converted into carbon dioxide and hydrogen is produced (referred to as the water gas shift reaction) via the methanol reforming reaction.

[0072] Following this, the hydrogen produced during the chemical reaction is isolated from the carbon dioxide and water in a subsequent chamber. This isolation may be achieved either by pressure swing adsorption (a technique used to separate some gases from a mixture of gases under pressure) or by utilising a membrane that only allows most of the hydrogen to pass through.

[0073] As indicated at 40, the hydrogen may then be transferred to the hydrogen fuel cells, such as a proton exchange membrane fuel cell (PEMFC). A PEMFC is a type of fuel cell that generates electricity through an electrochemical reaction between the hydrogen and oxygen from the air as indicated at 42 (step 10). It consists of an electrolyte, typically a polymer membrane (the proton exchange membrane), sandwiched between two electrodes, the anode and the cathode. During operation the hydrogen gas is fed to the anode, where it is split into protons and electrons. The protons pass through the proton exchange membrane, while the electrons are forced through an external circuit, generating an electric current. At the cathode, oxygen from the air reacts with the protons and electrons, forming water as a byproduct.

[0074] The energy created from the PEMFCs may be used to power the vessel using a suitable propulsion means as indicated at 44. Propulsion means may include one or more of a propeller, thruster or electrical propulsion.

[0075] Any residual energy from the PEMFCs may be sent to a battery storage system, shown at 46.

[0076] One of the by-products from the reaction in the PEMFC is water. At least part of this water by-product may be re-circulated back into the methanol / water mixer, indicated at 36.

[0077] Referring back to figure 4, the carbon dioxide formed from the methanol reformer reaction is captured in the reformer (step 8). The carbon dioxide is separated from the hydrogen and exhausted out of the reformer. This separation may be achieved using a membrane through which the hydrogen can pass leaving the carbon dioxide to be exhausted.

[0078] The captured and isolated carbon dioxide may then be liquefied and delivered into an empty one of the ISO storage tanks for return to shore, thereby completing the ‘circular’ carbon dioxide economy. As a first stage, the carbon dioxide is preferably transported to the methanol / water heater for heat exchange with the chilled methanol, as described below. This heat exchange may occur in a counter-flow or crossflow heat exchanger that starts to cool the CO2 at the same time as heating the methanol / water mixture to its final inlet temperature. Because the methanol was chilled onshore using electricity from a renewable source, preferably to a temperature lower than necessary for the intended use of the methanol, this “cold energy” can be utilised to begin the condensation / liquification of the carbon dioxide for storage. At the same time the methanol is heated to a more suitable temperature for vaporisation. In order to avoid too rapid cooling of the carbon dioxide with the risk of solidification into dry ice, a phase change material is preferably used in the barrier between the two sides of the heat exchanger to maintain the temperature of the barrier at between -20 °C and -40QC.

[0079] To further reduce the temperature of the gaseous CO2, it may be transported to a seawater cooling system, as indicated at 46. This process may involve using seawater as a cooling medium in a seawater heat exchanger. As the warm carbon dioxide gas passes through the seawater heat exchanger, it releases heat to the cooler seawater flowing in the other side of the exchanger. The heat is transferred from the carbon dioxide to the seawater, causing the carbon dioxide to cool down. As the seawater warms from the heat transfer it may be pumped back into the sea through an outlet.

[0080] Next, the carbon dioxide gas may be separated into two different channels. A first channel may transport a portion of the CO2 to a respective chilled methanol containing ISO storage tank at 26 whereby the CO2 may be used as an inert gas blanket. This is to ensure that there is no air in the gas space that could form an explosive atmosphere with the methanol vapour which is particularly important as methanol is a low flash point fuel. Nitrogen is normally used for such inert gas blanket in conventional methanol storage tanks. The use of product CO2 can be adopted for that purpose as long as the e-methanol is sufficiently dry to avoid formation of carbonic acid. The e-methanol synthesis plant may include a distillation column to remove all water from the product methanol. Note also that the ISO storage tanks do not need to be cleaned between service on methanol and CO2 or between service on CO2 and methanol.

[0081] A second channel may transport a portion of the CO2 to a carbon dioxide chiller I liquefier as indicated at 48. Cold energy embodied in the chilled methanol may be transferred to the CO2 gas in the heat exchanger, adapted to chill I liquefy the CO2 and thereby conserve the energy requirements on board the vessel. The at least partially liquefied CO2 may then be transported to a carbon dioxide re-liquefier as indicated at 50. The re-liquefier is used to complete the conversion of gaseous CO2 into its liquid form. The re-liquefier may be powered directly by the PEM fuel cells indicated at 40 or from the stored energy in the battery indicated at 46. The CO2 re-liquefier is an active unit that compresses and chills to re-liquefy boil-off gas from the ISO tank and / or residual gas from the CO2 chiller / liquefier.

[0082] As previously described, the methanol that arrived from the methanol synthesis plant to the vessel was transported in chilled ISO storage tanks. The methanol arrived having been chilled to temperatures between -90 'C and -20QC, thus keeping the respective ISO storage tank cool. After the methanol is emptied from the respective tank and transferred to the methanol pre-heater, the emptied ISO tank still maintains a temperature below freezing for a period of time. The respective emptied and chilled ISO tank is now ready to be reused to contain the liquid CO2. As indicated at 52, the liquid CO2 may be transferred to the respective ISO storage tank at a temperature of -20 'C and at a pressure of 20bar.

[0083] In the event that delivery of the respective ISO storage tank, now with the contained liquid carbon dioxide, is delayed, any boil-off CO2 may be recirculated back into the re-liquefier shown at 50. This may form a closed loop system (as indicated at 54) for any CO2 that is warming and returning to its gaseous form. The re-liquefier may cool the gaseous CO2 again returning it to its liquid form and then back to the ISO tank.

[0084] Referring back to figure 2, as indicated at 54 (step 9), the contained CO2 may be transported from the vessel and withdrawn into an insulated liquid CO2 tank shown at 56. This tank may be designed to store the CO2 in its liquid form by maintaining a low temperature and preventing it from evaporating or escaping. The insulation may help keep the CO2 at the required low temperature, typically around -20 'C for it to remain in its liquid state. The CO2 may remain in the insulated tank until a request from the methanol synthesis plant (indicated at 14) has been issued.

[0085] Once a designated supply of CO2 has been requested, the liquid CO2 may be transferred to a liquid carbon dioxide vaporiser as indicated at 58. The vaporiser may be connected to the insulated storage tank containing liquid and pressurised CO2 for easy transportation. Inside the vaporiser heat exchanger, the liquid CO2 may be counter-flowed with ambient methanol. The heat absorbed by the liquid CO2 causes it to increase in temperature. As the temperature rises, the liquid CO2 evaporates from liquid form back into a gaseous state. The gaseous CO2 may then be released from the vaporiser and transported to a flex-methanol synthesis plant to match the hydrogen supply. This is the final stage of the ‘circular’ carbon dioxide economy, and the recaptured carbon dioxide may be reused to react with hydrogen to form methanol and the cycle begins again. The methanol exits the liquid CO2 vaporiser as a partially chilled liquid.

[0086] Referring now to figure 5, where the methanol is to be used as a fuel source for a vehicle 60, such as a marine vessel (e.g. boat, ferry or containership), the vehicle may include a reformer 64. The vehicle may be loaded with at least one storage tank, which may be in the form of one or more ISO storage tanks 62, containing chilled methanol. The methanol containing storage tanks may be brought onto the vessel 60 and at least one of the tanks may be emptied for the methanol to be prepared to go into a reformer 64. Preparation of the methanol may include mixing the methanol with water in a mixer (not shown) and converting the methanol water mixture into steam and methanol vapour in a heater (not shown). The gaseous forms of the water and methanol are then transferred into the reformer 64.

[0087] As previously described in figure 4, the reformer 64 preferably converts the methanol into formaldehyde and hydrogen by dehydrogenation. Then through decomposition the formaldehyde is converted to carbon monoxide and hydrogen. Lastly, the carbon monoxide is further converted, in the presence of water, to carbon dioxide and hydrogen.

[0088] During the reformer process, the hydrogen and carbon dioxide gases are preferably separated through pressure swing adsorption and / or membranes separation.

[0089] The isolated hydrogen may be transferred to a hydrogen fuel cell, for example in the form of a proton exchange membrane fuel cell (PEMFC) 68, although the use of other types of fuel cells is envisaged. The fuel cell generates electricity through an electrochemical reaction between the hydrogen and oxygen. This electricity may provide the energy required to drive the vessel through propulsion means, in the form of a thruster or propeller 70, or to provide a power source for numerous other applications.

[0090] The isolated and captured carbon dioxide is preferably then prepared for storage or transfer. Preparation of the carbon dioxide includes chilling it to -20 °C under 20 bars of pressure. At this temperature and pressure, the carbon dioxide changes from a gas to a liquid, making it suitable to be stored or transported in a suitable storage tank. The liquid carbon dioxide may be then moved into a respective empty ISO storage tank 62 that initially transported the methanol. Lastly, when required, the ISO storage tanks containing the liquid carbon dioxide collected from the reformer may be transported off the vessel as indicated at 72 and the carbon dioxide may be reused in the production of more methanol.

[0091] It will be appreciated by persons skilled in the art that the above embodiments have been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the protection which is defined by the appended claims. For example, the above description mentions a vessel, and in particular makes reference to waterborne vessels such as ships. However, any means of transport capable of using a hydrogen-cells and carrying and storing the methanol and carbon dioxide could be used, including, but not limited to, wheeled vehicles, such as truck and trains. Furthermore, the process can also be used to provide power for industrial and other high energy use facilities, such as data centres, particularly those in remote locations, or for powering electrically driven plant or machinery at construction sites, by generating the methanol and transporting to where it is needed. The above description indicates that the alcohol used in this process is methanol. This is the simplest alcohol and is the most suitable for use in this process, because it has the highest hydrogen to carbon ratio of any hydro-carbon molecule. However, in principle other alcohols can be formed or the methanol transformed into other alcohols or e-fuels such as e-petrol, e-diesel, or e-kerocene.

[0092] Other possible applications and advantages of the principles of the present invention are as follows: 1. Zero marginal cost of circular CO2 i. The Levelised Cost of Methanol Production (LCMP) is in part determined by the input cost of CO2. ii. Present cost of linear grey CO2 = €300 / tonne delivered in liquid form iii. Present cost of linear green CO2 - €600 / tonne delivered in liquid form iv. One tonne of methanol synthesis requires 1 .4 tonnes of CO2 as a feedstock. v. So, CO2 cost input per tonne of linear green e-methanol = €840 per tonne vi. This will rise much further due to the Sustainable Aviation Fuel (SAF) mandate that is now in place in many countries around the world. vii. NB, SAF is a blend of mostly fossil sourced kerosene but with a proportion of green sourced kerosene that must grow over time. Kerosene has between 12 and 16 carbon atoms in its defined molecular structure, so has a relatively low hydrogen to carbon atomic ratio compared to methanol and represents a less efficient use of scarce CO2. However, kerosene is necessary for the jet engine powered aviation sector because of the unique properties of the molecule to operate across the very large temperature range experienced during high altitude flight. viii. The aviation sector can afford much higher prices for green CO2 than the marine sector and so it will soak up the majority of available supplies. This projection now means that linear green methanol supplies in the maritime sector are no longer being considered by International Maritime Organisation (IMO) and Zero Emission Maritime Buyers Alliance (ZEMBA), for example, as being scalable to the requirements of anticipated 2050 demand. ix. This patent application for recirculation of CO2 in a ‘Carbon Loop’ is a disruptive innovation that liberates the maritime sector from this competitive strangle hold, because aircraft cannot replicate the technical solutions on account of weight restrictions on airframes and landing gear and due to lack of space for additional tanks. x. Moreover, the input cost of circular CO2 to the LCMP is a small fraction of the linear figure of €840 / tonne shown in v) above. The actual cost per tonne equates to the marginal cost of capturing CO2 at the reformer vent, liquefying it and pumping the LCO2 to the ISO tank filling manifold through vacuum insulated pipes. The CAPEX for this balance of plant is very low, the duty factors are very high and the OPEX can be minimised by use of -50oC cryogenic temperatures coupled with conservation of cold energy, delivered along with the methanol, and by lower pressure (10bar) compression I liquefaction on board load requirements. The marginal cost of circular CO2 is effectively zero, in the scheme of things, and investors can be certain that it remains so throughout the full life of the plant. This final attribute provides a dominant contribution to making the Carbon Loop system and investable proposition.

[0093] 2. CO2 as a practical inert gas i. Nitrogen is normally used for the inert gas blanket in conventional methanol tanks, but in this innovation, the use of product CO2 can be adopted for that purpose as long as the e-methanol is sufficiently dry to avoid formation of carbonic acid. The e-methanol synthesis plant design includes a distillation column to remove all water from the product methanol. Note also that the ISO tanks do not need to be cleaned between service on methanol and CO2 or between service on CO2 and methanol. ii. ISO tank vendors and leading classification societies have confirmed that a standard ISO tank design specification for carriage of liquid CO2 product can be used for carriage of methanol with no modifications being required. CO2 can be used for inert gas blanketing when carrying methanol as mentioned above, the inner skin is made of 300 series austenitic stainless steel, the gross weights of both products with tank tare and trailer weights do not exceed permitted values for triple axles on standard 20ft (and non-standard 30ft) form factors, both products can be filled and withdrawn through the same tank bottom penetration and resident times without boil-off are in excess of 100 days.

[0094] 3. Private wire Direct Connections between Offshore wind farms and electrolysers i. Private wire direct electrical connections between wind farms and electrolysers are essential for avoidance of the high cost of conventional grid connections which these days need to incorporate network upgrading costs because infrastructure investment has been lagging behind demand. ii. Private wire direct electrical connections are also essential to avoid the problem of dispatch-down; when wind turbines are switched off due to i) insufficient balancing electrical load on the grid that would cause voltage to rise above statutory limits if they were allowed to keep running, curtailment, or ii) insufficient capacity in electrical circuits to carry the electrical current required by customers, constraint. Dispatch down is now causing business interruption through loss of revenues in any given year of up to 40% of expected values. This has undermined wind farm investor confidence and brought the wind industry expansion to a complete halt in Northern Ireland for the last 6 years. The policy and regulatory response has been to oblige electricity utilities to compensate wind farm operators for dispatch down, a cost they are allowed to pass through to customers’ bills. The option to upgrade the electricity network to cope with the additional wind generation required for the decarbonisation agenda is fundamentally flawed; it would cost too much, take too long, attract massive objections to new power lines and if all the worlds’ governments followed suit there wouldn’t be enough copper! Private wire-based projects can enjoy zero risk of dispatch down for their entire lifetime. iii. Private wire-based projects do not trade on the electricity market, so they don’t need costly support schemes that are set up to manage market volatility caused by dominance of fossil fuel price fluctuations in electricity price determination. These so-called Contracts for Difference (CfDs) are high priced over 15-year periods so that debt repayment and investor returns can be condensed into this time frame. The technical life of wind farms is now designed to be 35 years, i.e. 20 years longer than CfD durations. Financing projects over that longer timeframe has the effect of greatly reducing the electricity price, which in turn has the largest single effect of reducing the Levelised Cost of Hydrogen Production.

[0095] 4. Use of waste heat from electrolysers i. Electrolysers are typically around 70% efficient at converting electricity and water into hydrogen and oxygen with the other 30% of input electricity being wasted in the form of heat at around 45oC. This manifests itself as hot water flowing away from heat exchangers into the environment. ii. If the electrolyser can be located adjacent to a large population centre, then this renewable heat can be elevated to higher flow temperatures using a heat pump and distributed to heat customers through a city scale district heating system. Heat customers pay money for the heat which creates an additional revenue stream to the electrolyser business model. Good use of the heat allows the overall conversion efficiency of electrolysers to move closer to 100%. The renewable heat used will displace existing fossil fuels such as heating oil and natural gas, which allows municipalities to significantly reduce GHG emissions in their area and keep on track with decarbonisation pathways. There could be avoidance of fines and carbon trading costs too. iii. Heat network investors normally accept long term heat supply agreements with industrial, commercial and public sector parties but prefer not to deal directly with domestic parties. This allows developers to trade heat to the domestic sector in a measured way that is affordable for customers and helps to alleviate fuel poverty. This in turn provides a valuable social dimension to the project, which attracts vital political support.

[0096] 5. Use of flexible e-methanol synthesis i. Traditional chemical processes are designed to be in continuous operation to maximise equipment utilisation and commercial returns to investors. This requires feed stocks to be stored, however, and for hydrogen feedstocks, at large scale, this storage would be both complex and expensive. It would involve either compression of hydrogen into pressure vessels or liquefaction into cryogenic tanks, both of which more than double the levelised cost of hydrogen production. Therefore, a flexible plant that can modulate the production rate up and down to match the instantaneous availability of hydrogen output from the electrolyser is the preferred option for e-methanol synthesis. ii. The only active control point in flexible methanol synthesis is to vaporise sufficient CO2 out of liquid storage to match the mass of hydrogen being input to the plant at that moment. Vaporising CO2 is carried out in a counter flow heat exchanger with product methanol being chilled as it is prepared for loading into ISO tanks. This is the land based section of the cold energy conservation approach that is a fundamentally important energy efficiency measure within the overall carbon loop system.

Claims

Claims1 . A method of transporting hydrogen comprising: forming an alcohol from hydrogen and carbon dioxide; transporting said alcohol; breaking down said alcohol to form carbon dioxide and hydrogen; using said hydrogen as a fuel; and capturing said carbon dioxide to transport for reuse in generating more alcohol.

2. A method according to any preceding claim wherein said alcohol is formed in a synthesis plant.

3. A method according to claim 2 wherein said captured carbon dioxide is transported to said synthesis plant or a different synthesis plant.

4. A method according to any preceding claim wherein said alcohol is transported in at least one storage tank, said carbon dioxide produced from breaking down said alcohol being subsequently stored and transported in the same storage tank once said alcohol has been emptied therefrom.

5. A method according to claim 4 comprising chilling said alcohol prior to transportation in said at least one storage tank.

6. A method according to claim 4 or claim 5, including liquefying said carbon dioxide prior to delivery into said at least one storage tank.

7. A method according to claim 6 when dependent upon claim 5, wherein said carbon dioxide is at least partially liquefied by heat exchange with said chilled alcohol.

8. A method according to claim 7 wherein said carbon dioxide is liquefied by passing said chilled alcohol from one of said at least one storage tanks and said carbon dioxide through either side of a heat exchanger prior to delivering the carbon dioxide into an emptied one of said at least one storage tanks.

9. A method according to claim 8 wherein a barrier of said heat exchanger contains a phase change material contained within said barrier.

8. A method according to any preceding claim wherein said energy is used for the propulsion of a vehicle or for providing an electricity power supply for a data centre.

9. A method according to any preceding claim wherein said carbon dioxide is captured within a reformer.

10. A method according to any preceding claim including the step mixing said alcohol with water.

11. A method according to any preceding claim wherein said hydrogen is used in hydrogen fuel cells.

12. A method according to claim 10 and 11 wherein said water is formed from said hydrogen fuel cells, at least a portion of said water being mixed with said alcohol.

13. A method according to any preceding claim wherein said alcohol comprises methanol.

14. A method of propelling a vehicle comprising: receiving alcohol formed as part of the method according to any preceding claim; and using said hydrogen to fuel said vehicle.

15. A method according to claim 14 wherein said vehicle comprises a marine vessel.

16. A method according claims 14 and 15 wherein said hydrogen is used in one or more fuel cells.

17. A method according to claim 16 wherein said one or more fuel cells comprise proton exchange membrane fuel cells.

18. A method of creating and transporting a fuel comprising: splitting water to create hydrogen; and transporting said hydrogen using a method according to any of claims 1 to 13.

19. A method according to claim 18 wherein said hydrogen is synthesised through electrolysis using electricity.

20. A method according to claim 19 wherein said electricity is generated by renewable means.

21. A vehicle comprising: at least one storage tank; a reformer for splitting said alcohol into hydrogen and carbon dioxide; at least one hydrogen fuel cell for generating energy from said hydrogen; propulsion means for propelling said vehicle using said generated energy; and carbon dioxide capturing means for capturing said carbon dioxide wherein said at least one storage tank is used to store said carbon dioxide after it has been emptied of methanol.

22. A vehicle according to claim 21 wherein said means for capturing said carbon dioxide occurs in said reformer.

23. A vehicle according to claims 21 and 22 wherein said vehicle comprises a marine vessel and said propulsion means comprises one or more thrusters or propellers.

24. A vehicle according to claims 21 to 23 wherein said alcohol comprises methanol.

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