System

Abstract

A hydrogen generation system 2 for mounting to a machine in which hydrogen generated by the system is utilised to provide energy to a prime mover (such as an engine or fuel cell) is detailed. The gene

Description

FIELD The present disclosure relates to a hydrogen generation system for mounting to a machine, for example a working machine. The disclosure also relates to a machine, for example a working machine, comprising said hydrogen generation system and a method of operating said hydrogen generation system. BACKGROUND Off-highway vehicles / working machines are typically those used in construction industries (e.g. backhoe loaders, slew excavators, telescopic handlers, forklifts, skid-steer loaders, dump trucks, bulldozers, graders), agricultural industries (e.g. tractors, combine harvesters, wheeled loading shovels, telescopic handlers, self-propelled harvesters and sprayers), quarrying (e.g. excavators, wheeled loading shovels, aggregate crushing equipment), and forestry (e.g. timber harvesters, feller bunchers). Many working machines have a primary function of moving material using either a lifting arm (e.g. a pivoting boom) or a working arm (e.g. an excavator arm) and may be referred to as material handling machines. Conventionally, working machines of the type referred to above are generally powered by diesel internal combustion engines. However, there is a general need to reduce vehicle emissions in the face of climate change and other more stringent air quality standards, leading to working machine OEMs considering alternative energy sources for such machines. One proposed alternative is to use hydrogen gas as a fuel. However, this introduces problems of storing the hydrogen gas and refuelling. The present disclosure seeks to overcome or at least mitigate some of the problems associated with the prior art. SUMMARY The present teachings provide a hydrogen generation system according to appended claims 1 to 16. An aspect of the teachings provides a hydrogen generation system for mounting to a machine in which hydrogen generated by the system is utilised to provide energy to a prime mover thereof. The hydrogen generation system may comprise a reaction vessel arranged to hold a water containing liquid. The hydrogen generation system may comprise a metallic substance delivery apparatus for selectively delivering a reactive metallic substance to the reaction vessel, which on contact with the liquid reacts to generate hydrogen. The hydrogen generation system may comprise a pressure regulator assembly arranged to deliver the hydrogen at a pressure above atmospheric pressure to an energy conversion apparatus downstream of the generation system. As used herein, the term "metallic substance" will be understood to mean any substance comprising a metal, a compound containing a metal, a metal ion, a metalloid, and / or any substance that exhibits the properties of a metal at least to the extent that it reacts with said liquid to generate hydrogen. The hydrogen generation system disclosed herein enables hydrogen to be provided on demand and ata required pressure. In an exemplary embodiment, the hydrogen generation system is provided on a machine, e.g. a working machine or vehicle. In this embodiment, hydrogen can be provided on demand at the machine itself. In this way, the machine is not tethered to a hydrogen supply facility for refuelling. Provided that the machine has a sufficient supply of metallic substance, the machine can simply be replenished with liquid containing water to generate the required hydrogen fuel. Consequently, as long as there is a supply of liquid containing water (e.g. a water supply), the machine is not restricted by the location of hydrogen refuelling facilities. In exemplary known systems, hydrogen fuel may be produced at a production site e.g. by electrolysis which requires energy to produce hydrogen. This typically requires a large investment in infrastructure. From the production site, transport of the hydrogen gas to where it is needed is then required. Transport of a gas may be inefficient and typically requires a trailer or vehicle to move the hydrogen gas to where it is required. It is also necessary to consider the pressure of hydrogen gas produced at the production site versus the pressure required by the machine. Some means of pressurising and / or decompressing is typically required to ensure the hydrogen gas is delivered to the machine at the required pressure. By providing the hydrogen generation system disclosed herein on board a machine, the above-described potential problems associated with refuelling are avoided. Rather, a simple and convenient way of running a machine on hydrogen gas is achieved. In some known examples, hydrogen fuel is stored in pressurised tanks on machine. The system disclosed herein reduces the need for such hydrogen storage onboard the machine, since hydrogen is produced on demand. Accordingly, the need to accommodate numerous hydrogen storage tanks onboard the machine is removed. In some embodiments, renewable energy may be used to create the metallic substance. In this way, the hydrogen generation system disclosed herein may be carbon neutral. In some embodiments, renewable energy may also be used to treat unwanted waste products from the reaction between the metallic substance and the liquid. For example, renewable energy may be used to regenerate metallic substance from the reaction waste products. Optionally, the pressure regulator assembly is configured to deliver hydrogen at in excess of about 3 bar. Optionally, the generation system further comprises a buffer vessel downstream of the reaction vessel and configured to hold a volume of hydrogen at an elevated pressure. In this way, hydrogen that is generated by the generation system can travel to the energy conversion apparatus, via the buffer vessel. In the event that more hydrogen gas is generated by the generation system than is required by the energy conversion apparatus, the excess hydrogen gas can be stored in the buffer vessel until such time as it is required by the energy conversion apparatus. For example, where demand from the prime mover of the machine ceases, hydrogen produced from the reaction taking place in the reaction vessel can be stored in the buffer vessel. This may be more efficient, and avoid the need to vent hydrogen, which is undesirable from a safety and environmental perspective. In some embodiments, the generation system is controlled such that a volume of excess hydrogen gas does not exceed a volume of the buffer vessel. In some embodiments, the system is configured such that hydrogen is continuously produced. In other words, such that the reaction producing hydrogen is continuously taking place in the reaction vessel. In some embodiments, the system is configured such that hydrogen is produced in batches. For example, the system may be configured to initiate production of hydrogen in the reaction vessel when the pressure of hydrogen in the buffer vessel reaches a predetermined minimum setpoint. For example, the system may be configured to cease production of hydrogen in the reaction vessel when the pressure of hydrogen in the buffer vessel reaches a predetermined maximum setpoint. For example, the system may be configured to control the production of hydrogen based on a level of demand from the prime mover. Optionally, the metallic substance delivery apparatus is configured to deliver the metallic substance in powdered form to the reaction chamber. By delivering the metallic substance in powdered form, as opposed to a form having a lower surface area:volume ratio, the rate of reaction between the metallic substance and said liquid is increased since there is a greater surface available to react. In other words, the speed at which hydrogen is generated is increased. The metallic substance may develop or comprise a surface layer, e.g. comprising a metal oxide, which inhibits reaction of the metallic substance. In some embodiments, the powdered metallic substance comprises a sufficiently fine powder such that a said surface layer cannot form. Optionally, the metallic substance delivery apparatus is configured to deliver metallic substance powder when suspended in a liquid to form a paste. In this way, the metallic substance is provided in a form which can flow. This may facilitate delivery and / or handling of the metallic substance. In some embodiments, the delivery apparatus may deliver the metallic substance via a hydraulics-based apparatus. Optionally, the metallic substance delivery apparatus comprises a receptacle to hold or an interface to mount a replaceable cartridge of metallic substance powder. In this way, the generation system can be easily replenished with metallic substance when required. Optionally, the metallic substance delivery apparatus further comprises a mechanical transfer mechanism such as a screw, a plunger and / or an agitation device to introduce the metallic substance powder to the reaction vessel. In this way, a simple and effective means for introducing the metallic substance to the reaction vessel is provided. Optionally, the metallic substance delivery apparatus comprises a grinder arranged to grind the metallic substance into a powder in situ. In this way, the metallic substance can be modified to a desired powdered form by the generation system. For example, the metallic substance may be provided in a variety of forms e.g. a form having a lower surface area:volume ratio than desired, and then modified to the desired form in situ. Optionally, the hydrogen generation system further comprises a liquid delivery system comprising a liquid reservoir separate from the reaction vessel and a delivery conduit thereto. In this way, the liquid reservoir can be spaced apart from the reaction vessel (or vice versa), so that each component can be placed at a desired location. Having a separate liquid reservoir and reaction vessel enables fresh liquid to be introduced to the reaction vessel as and when required. Optionally, the generation system further comprises a waste reservoir downstream of the reaction vessel and arranged to store reaction products therefrom. In this way, waste reaction products can be removed from the reaction vessel, for example carried in liquid, and stored and the waste reservoir until such time as they can be removed. Once the reaction vessel has been emptied, e.g. by emptying the contents into the waste reservoir, in some embodiments, fresh liquid from the liquid reservoir can be introduced into the reaction vessel ready for reacting with the metallic substance. In some embodiments, the waste reservoir is coupled to the reaction vessel via a delivery conduit. In this way, the waste reservoir can be located at any desired location, for example when the generation system is located on a machine the waste reservoir can be positioned at a desired location. Optionally, the liquid reservoir and waste reservoir are of variable volume and are provided in a common housing. In this way, the volume of the common housing can be optimised depending on the required volumes of the liquid and waste reservoirs. For example, prior to a hydrogen generating reaction, the volume of the liquid reservoir can be configured to be larger than that of the waste reservoir. Similarly, during or after a hydrogen generating reaction, the volume of the waste reservoir can be configured to be larger. Optionally, the liquid reservoir and waste reservoir comprise flexible bladders. Optionally, the generation system further comprises a reaction adjuvant delivery apparatus arranged to deliver a reaction adjuvant material, such as a caustic material, to the reaction vessel. The metallic substance may develop or comprise a surface layer, e.g. comprising a metal oxide, which inhibits reaction of the metallic substance. The adjuvant material may act to strip this surface layer from the metallic substance, or otherwise expose the metallic substance beneath, thereby facilitating reaction of the metallic substance with the liquid. In this way, production of hydrogen is facilitated. In some embodiments, the adjuvant may comprise an alkali and / or an acid, for example a caustic material. In some embodiments, the adjuvant comprises NaOH. In some embodiments, the adjuvant comprises mercury, for example mercury chloride and / or mercury oxide, or any material that acts to expose the metallic substance for reaction with said liquid. Optionally, the reaction vessel is arranged to withstand a pressure of at least about 10 bar, for example, at least about 20 bar. Optionally, the generation system further comprises a controller arranged to monitor a hydrogen pressure and adjust at least an amount metallic substance delivered by the metallic substance delivery apparatus to the reaction vessel so as to maintain a predetermined setpoint minimum hydrogen pressure. In this way, the generation system ensures that hydrogen of a required pressure for use by the energy conversion apparatus is provided. Optionally, the reaction vessel further comprises a stirring device for mixing the contents of the reaction vessel. In this way, reaction between the metallic substance and liquid is facilitated. The present teachings provide a machine according to appended claims 17 to 30 comprising an onboard hydrogen generation system as disclosed herein. An aspect of the teachings provides a machine comprising an onboard hydrogen generation system as disclosed herein. The machine may comprise a prime mover powered by the hydrogen generation system. In exemplary embodiments, the machine is a working machine, for example a backhoe loader, slew excavator, telescopic handler, forklift, skid-steer loader or other working machine. Optionally, the energy conversion apparatus is the prime mover, the prime mover is an internal combustion engine, and the hydrogen is combusted therein to generate kinetic energy. Optionally, hydrogen is the only fuel combusted in the engine. Optionally, the engine comprises at least one fuel injector and the pressure regulator assembly is configured to deliver hydrogen to the fuel injector at a pressure of at least about 3 bar. Optionally, the prime mover is an electric motor, and the energy conversion apparatus is a hydrogen fuel cell arranged to convert the hydrogen to electrical energy to power the electric motor. Optionally, the machine is a self-propelled vehicle, and the prime mover is arranged to propel the vehicle. Optionally, the machine is a ground vehicle comprising a ground engaging propulsion structure and the prime mover powers the ground engaging propulsion structure. Optionally, the machine is an off-highway working machine and the prime mover provides power to perform a working operation, such as to move a working arm thereof. Optionally, the machine is a telescopic handler comprising a working arm pivotable about a generally horizontal axis to a machine chassis proximate a rear of the chassis in a normal direction of travel, wherein a free end of the working arm comprises an interface to mount a working implement forward of the machine chassis, and wherein an operator station for a machine operator is offset to a side of the working arm, and wherein at least the liquid reservoir is mounted at least partially under the operator station. Optionally, the prime mover is positioned in a housing offset from the other side of the working arm to the operator station, and at least the buffer vessel is located in the housing. Optionally, the waste reservoir is mounted at least partially under the operator station. Optionally, the reaction vessel is mounted at least partially under the operator station. Optionally, the reaction vessel is located within the housing. Optionally, the machine is a tractor, and the working arm is a three point linkage, or the machine is a backhoe loader and the working arm is a loader arm and / or backhoe, wherein an operator station is located in a substantially laterally central position on a chassis thereof, and wherein at least the liquid reservoir is mounted at least partially under the operator station. In accordance with appended claims 31 to 33, the present teachings provide a method operating a hydrogen generation system as disclosed herein. An aspect of the teachings provides a method of operating a hydrogen generator as disclosed herein. The method may comprise the steps of: a. the controller monitoring the hydrogen pressure; and / or b. adjusting a delivery of metallic substance to the reaction vessel in response to whether the hydrogen pressure is at least above a lower setpoint pressure value. Optionally, the controller further adjusts the delivery of metallic substance in response to whether the hydrogen pressure is above an upper setpoint value. Optionally, the controller further adjusts the delivery of metallic substance in response to an electrical signal provided to the prime mover of demanded power. It will be appreciated that the optional features described may apply to any aspect disclosed herein. All combinations contemplated are not recited explicitly for the sake of brevity. BRIEF DESCRIPTION OF DRAWINGS Embodiments will now be described by way of example only with reference to the accompanying figures, in which: Figure 1 is a schematic illustration of the hydrogen generation system disclosed herein; Figure 2 is a side view of a telehandler having an onboard hydrogen generation system as shown in Figure 1; Figure 3 is a plan view schematic illustration of the telehandler of Figure 2; Figure 4 is a plan view schematic illustration of a telehandler according to an alternative embodiment; Figure 5 is a side view of a backhoe loader having an onboard hydrogen generation system as shown in Figure 1; Figure 6 is a plan view schematic illustration of the backhoe loader of Figure 5; and Figure 7 is a flow chart of a method in accordance with an embodiment disclosed herein. DETAILED DESCRIPTION In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of various embodiments and the teachings. However, those skilled in the art will understand that: the present teachings may be practiced without these specific details or with known equivalents of these specific details; that the present teachings are not limited to the described embodiments; and, that the present teachings may be practiced in a variety of alternative embodiments. It will also be appreciated that well known methods, procedures, components, and systems may not have been described in detail. References to term axial in the present disclosure is generally used in relation to the longitudinal axis of the machine. The term width is generally used in relation to the longitudinal length, that is, transverse to the length. With reference to Figure 1, a hydrogen generation system generally indicated by the reference numeral 2 is provided. The system is configured for mounting to a machine (described in more detail below) such that hydrogen generated by the system 2 is utilised to provide energy to a prime mover thereof, for example an engine or a motor. In the schematic illustration shown in Figure 1, arrows are used to denote movement of reagents, adjuvant and / or reaction products between components, whereas lines are used to denote communication links between components. The hydrogen generation system 2 includes a reaction vessel 4 arranged to hold a water containing liquid, for example water. The system 2 also includes a metallic substance delivery apparatus 6 for selectively delivering a reactive metallic substance to the reaction vessel 4. When the metallic substance is brought into contact with the water in the reaction vessel 4, a reaction occurs which generates hydrogen gas. The system 2 also includes a pressure regulator assembly 8 arranged to deliver hydrogen gas generated by the system 2, at a pressure above atmospheric pressure, to an energy conversion apparatus 10 downstream of the generation system 2. In particular when the system is onboard a working machine or other vehicle, the energy conversion apparatus 10 is a hydrogen fuelled internal combustion engine or a hydrogen fuel cell. In the illustrated embodiment, the pressure regulator assembly 8 is configured to deliver hydrogen at in excess of about 3 bar. In some embodiments, the pressure regulator assembly is configured to deliver hydrogen at about 5 bar or higher, for example at about 10 bar or higher, for example at about 20 bar or higher, for example at a pressure in the range of from about 20 bar to about 50 bar. The reaction vessel 4 is arranged to withstand elevated pressure of at least about 10 bar, for example at least about 20 bar. Furthermore, the reaction vessel 4 includes a stirring device for mixing the contents of the reaction vessel 4. In the illustrated embodiment, the system 2 also includes a hydrogen buffer tank 12 located downstream of the reaction vessel 4 and arranged to hold a volume of hydrogen at an elevated pressure. The hydrogen buffer tank 12 is coupled to the reaction vessel 4 via a delivery conduit 13, such that hydrogen generated in the reaction vessel 4 flows to the hydrogen buffer tank 12 via the delivery conduit 13. The system 2 also comprises a liquid barrier device 15 configured such that liquid and / or solids in the reaction vessel 4 are inhibited or prevented from entering the hydrogen buffer tank 12, but hydrogen gas generated in the reaction vessel 4 is able to pass through the barrier device 15 and enter the hydrogen buffer tank 12. In this way, liquid and / or solids are prevented from entering the buffer tank 12, in particular, when the machine is moving around and liquid and / or solids in the reaction vessel 4 are similarly caused to move within the reaction vessel 4. In some embodiments, the liquid barrier device 15 may be a structure that inhibits flow or liquids and / or movement of solids past the barrier device 15, for example a series of fins or baffles. In some embodiments, the liquid barrier device 15 may be a gas-permeable membrane that inhibits or prevents liquids and / or solids passing therethrough. The pressure regulator assembly 8 is arranged to control the pressure of hydrogen gas released from the hydrogen buffer tank 12 to the hydrogen engine or fuel cell 10, such that hydrogen is delivered to the hydrogen engine or fuel cell 10 at a required pressure. In the illustrated embodiment, the pressure regulator assembly 8 is a valve configured to open when the pressure in the hydrogen buffer tank 12 reaches the required pressure, e.g. about 3 bar, e.g. about 5 bar, e.g. about 6 bar. It will be appreciated that any suitable pressure regulator assembly may be used such that hydrogen is delivered to the energy conversion apparatus at a required pressure. The metallic substance delivery apparatus 6 is configured to deliver the metallic substance to the reaction vessel 4 in powdered form. In some embodiments, the metallic substance delivery apparatus is configured to deliver metallic substance powder when suspended in a liquid to form a paste. In the illustrated embodiment, the metallic powder delivery apparatus 6 includes a receptacle 14 to hold a replaceable cartridge 16 of metallic substance powder. In some embodiments, the metallic substance delivery apparatus includes an interface to mount a replaceable cartridge of metallic substance powder. The metallic substance delivery apparatus 6 also includes a mechanical transfer mechanism 18 to introduce the metallic substance powder to the reaction vessel 4. Such a mechanical transfer mechanism may be a screw, a plunger, an agitation device and / or any other suitable mechanism. The system 2 includes a liquid delivery system having a liquid reservoir which is separate from the reaction vessel 4. In the illustrated embodiment, the liquid reservoir is a water tank 20 which is coupled to the reaction vessel 4 via a delivery conduit 22, such that water can be introduced into the reaction vessel 4 from the water tank 20 via the delivery conduit 22. A valve 23 is provided between the delivery conduit 22 and the reaction vessel 4, to ensure that the contents of the reaction vessel 4 cannot flow upstream along the delivery conduit 22, in the direction of the water tank 20. In the illustrated embodiment, a pump 25 is provided to pump liquid from the water tank 20 to the reaction vessel 4 as and when required. The system 2 also includes a waste reservoir 24 downstream of the reaction vessel 4 and which is arranged to store waste reaction products from the reaction vessel 4. The waste reservoir 24 is coupled to the reaction vessel 4 via a delivery conduit 26, such that waste reaction products can be transferred from the reaction vessel 4 to the waste reservoir 24 via the delivery conduit 26. In the illustrated embodiment, waste products from the reaction vessel 4 are carried in water from the reaction vessel 4 to the waste reservoir 24. A valve is 27 provided between the delivery conduit 26 and the reaction vessel 4. When the valve 27 is open, the contents of the reaction vessel 4 can only flow along the delivery conduit 26 to the waste reservoir 24. When the valve 27 is closed, flow along the delivery conduit 26 is prevented. The water tank 20 and the waste reservoir 24 are provided in a common housing 28 and each of the water tank 20 and the waste reservoir 24 have a variable volume such that the use of space inside the housing 28 is optimised. The water tank 20 and the waste reservoir 24 are each formed of a flexible bladder. The system 2 further includes a reaction adjuvant delivery apparatus 30 which is configured to deliver a reaction adjuvant material to the reaction vessel 4. For example, the reaction adjuvant material may be a caustic material, such as sodium hydroxide (NaOH). In the illustrated embodiment, the adjuvant delivery apparatus 30 is configured to deliver adjuvant material directly into the reaction vessel 4. Alternatively, the adjuvant delivery apparatus may be configured to dose adjuvant material into the water tank 20. In some embodiments, the adjuvant delivery apparatus may be configured to dose adjuvant material into the delivery conduit 22 between the water tank 20 and the reaction vessel 4, such that adjuvant material is delivered to the water tank 20 as water is introduced into the reaction vessel 4. The system 2 includes a controller 32 which is arranged to monitor a hydrogen pressure in the hydrogen buffer tank 12 and to adjust an amount of metallic substance delivered by the metallic substance delivery apparatus 6 to the reaction vessel 4. In this way, a predetermined setpoint minimum hydrogen pressure can be maintained, specifically, the minimum pressure required by the hydrogen engine or fuel cell 10. Furthermore, the controller 32 is also arranged to control delivery of water from the water tank 20 to the reaction vessel 4, for example by controlling the pump 23, control emptying of the reaction vessel 4 into the waste reservoir 24, for example by controlling the valve 27, and adjust an amount of adjuvant delivered by the adjuvant delivery apparatus 30 to the reaction vessel 4. In this way, the reaction taking place in the reaction vessel 4 can be more closely controlled such that the required amount of hydrogen is produced. The controller may comprise: control circuitry; and / or processor circuitry; and / or at least one application specific integrated circuit (ASIC); and / or at least one field programmable gate array (FPGA); and / or single or multi-processor architectures; and / or sequential / parallel architectures; and / or at least one programmable logic controllers (PLCs); and / or at least one microprocessor; and / or at least one microcontroller; and / or a central processing unit (CPU), to perform the described methods. The controller may include an associated memory, or the memory may be located locally to the controller or remotely. The memory may be a non-volatile flash memory. In use, the water tank 20 is filled with water, which is then pumped into the reaction vessel 4 by the pump 25 via the delivery conduit 22. A replaceable cartridge 16 of metallic substance is mounted in the receptacle 14 of the metallic substance delivery apparatus 6. In the illustrated embodiment, the metallic substance in the cartridge is in a powdered form. The metallic substance in powdered form is introduced into the reaction vessel 4 by the mechanical transfer mechanism 18 of the metallic substance delivery apparatus 6. When an adjuvant is required, this is introduced into the reaction vessel 4 from the adjuvant tank 30. The metallic substance reacts with water in the reaction vessel 4 to produce hydrogen gas and waste products. The hydrogen gas flows from the reaction vessel 4, through the liquid barrier device 15, to the hydrogen buffer tank 12. When the hydrogen gas in the buffer tank 12 reaches the required pressure, e.g. about 3 bar, the valve 8 opens to deliver hydrogen gas to the hydrogen engine or fuel cell 10. The controller 32 monitors the hydrogen pressure in the hydrogen buffer tank 12. If it is determined that the hydrogen pressure is too low, the controller directs the metallic substance delivery apparatus 6 to increase an amount of metallic substance delivered to the reaction vessel 4. In this way, a predetermined setpoint minimum hydrogen pressure can be maintained, specifically, the minimum pressure required by the hydrogen engine or fuel cell 10. Similarly, if it is determined that the hydrogen pressure is too high, the controller directs the metallic substance delivery apparatus 6 to decrease an amount of metallic substance delivered to the reaction vessel 4, or cease delivery of the metallic substance to the reaction vessel 4. In this way, a predetermined setpoint maximum hydrogen pressure can be maintained, specifically, the maximum pressure required by the hydrogen engine or fuel cell 10. It will be understood that, where the amount of metallic substance introduced to the reaction vessel 4 is the determining factor in the amount of hydrogen that is produced, sufficient water and optionally adjuvant will be present in the reaction vessel 4. The controller 32 also controls delivery of water from the water tank 20 to the reaction vessel 4 by controlling the pump 23 and adjusts an amount of adjuvant delivered by the adjuvant delivery apparatus 30 to the reaction vessel 4, such that the required pressure is maintained in the hydrogen buffer tank 12. In some embodiments, the load on the engine 10 or a motor powered by the fuel cell 10 is monitored by the controller 32 to determine a hydrogen fuel demand. The controller 32 then adjusts the delivery of the metallic substance by the metallic substance delivery apparatus 6, adjusts the delivery of water from the water tank 20, and / or adjusts the delivery of adjuvant from the adjuvant delivery apparatus 30. In this way, the reaction taking place in the reaction vessel 4 and the amount of hydrogen produced, hence the pressure of hydrogen in the hydrogen buffer tank 12, is controlled in accordance with demand. Waste products and water in the reaction vessel 4 are removed from the reaction vessel 4 when required and stored in the waste reservoir 24, such that fresh reagents, and optionally adjuvant, can be introduced to the reaction vessel 4. The system 2 may be used to carry out a range of reactions to produce hydrogen. Various examples are provided below. Example 1 The metallic substance is a metal, for example, aluminium, which reacts with water to produce hydrogen according to reaction (1) below. 2AI + 4H2O 2AIO2H + 3H2 (1) Example 2 The metallic substance is aluminium. Sodium hydroxide is used as an adjuvant to remove the surface oxide layer from the aluminium, thereby exposing the aluminium metal for reaction. Aluminium reacts with water to produce hydrogen in accordance with reaction (1) above. In addition, hydrogen is produced via reaction (2) below. 2AI + 2NaOH + 2H2O 2NaAIO2 + 3H2 (2) Example 3 The metallic substance is a metal hydride, for example magnesium hydride, which reacts with water to produce hydrogen according to reaction (3) below. MgH2 + 2H2O -> 2H2 + Mg(OH)2 (3) Example 4 The metallic substance is an alkali metal, for example lithium, which reacts with water to produce hydrogen according to reaction (4) below. Li + H2O LiOH + H2 (4) Example 5 The metallic substance is an alkali earth metal, for example calcium, which reacts with water to produce hydrogen according to reaction (5) below. Ca + 2H2O -» Ca(OH)2 + H2 (5) Example 6 The metallic substance is a metalloid, for example silicon, which reacts with water to produce hydrogen according to reaction (6) below. Si + H2O SiO2 + H2 (6) With reference to figures 2 to 3, a machine 100 is provided having an onboard hydrogen generation system 2. With reference to figure 2, the machine 100 is a telescopic handler, commonly known as a telehandler, having a working arm 134 pivotable about a generally horizontal axis H to a machine chassis 136 proximate a rear of the chassis 136 in a normal direction of travel A. A free end of the working arm 134 comprises an interface 138 to mount a working implement 140 forward of the machine chassis 136. An operator cab 142 for a machine operator is offset to a side of the working arm 134. The telehandler 100 is a self-propelled vehicle and includes a prime mover arranged to propel the vehicle. As shown in Figure 2, the telehandler 100 is a ground vehicle having a ground engaging propulsion structure including a pair or front wheels 144 and a pair of rear wheels 146. The prime mover is arranged to power the front and rear wheels 144,146. The prime mover is also arranged to provide power to perform a working operation, such as moving the working arm 134. As shown in figure 3, the prime mover is powered by the hydrogen generation system 102. The features described in relation to figure 1 are denoted by the same reference numerals but preceded by the number"!". In the embodiment of figure 3, the energy conversion apparatus 110 is the prime mover, and the prime mover is an internal combustion engine 110 configured to run on hydrogen fuel. The hydrogen fuel is combusted in the internal combustion engine 110 to generate kinetic energy. In the illustrated embodiment, hydrogen is the only fuel combusted in the engine 110. The pressure regulator assembly 108 is configured to deliver hydrogen to the engine 110 at a pressure of about 20 bar or less, for example at a pressure of about 10 bar or less. The internal combustion engine 110 is arranged to drive at least one of the pairs of front and rear wheels 144, 146 via a suitable mechanical or hydrostatic transmission (not shown). The internal combustion engine 110 is also arranged to drive a hydraulic pump (not shown) to power actuators 135 which move the working arm 134. The engine 110 includes at least one fuel injector 149 and the pressure regulator assembly 108 is configured to deliver hydrogen to the fuel injector 149 at a pressure of at least 3 bar, for example at least 10 bar, for example at least 20 bar, for example at a pressure in the range of from about 20 bar to about 50 bar. With reference to figure 3, one or more of the components of the system 102 are located under the operator cab 142. In the illustrated embodiment, the water tank 120 and the waste reservoir 124 are mounted under the operator cab 142. The water tank 120 and waste reservoir 124 are located in a common housing 128. The adjuvant delivery apparatus 130 is also mounted under the operator cab 142. This location is readily accessible to the machine operator to fill the water tank 120 and adjuvant delivery apparatus 130, as well as empty the waste reservoir 124. In addition, the location may help to maintain a similar weight distribution to a corresponding diesel powered machine, and thereby allow the machine to have a similar load carrying capacity (load chart) to a corresponding diesel machine. In a standard diesel powered telehandler, the diesel fuel tank may be located under the operator cab 142. In a hydrogen powered telehandler 100, a diesel tank is not required and one or more of the components of the hydrogen generation system 102 can be mounted in the space where the diesel tank would previously have been. This optimises the layout of the telehandler and minimises the changes required to modify a diesel powered telehandler design to be a hydrogen powered telehandler, and may maintain a similar weight distribution to a diesel powered telehandler. In some embodiments, all the components of the hydrogen generation system 102 are mounted in the space that would previously been occupied by the diesel fuel tank, e.g. under the operator cab 142. The water tank 120 may be arranged to hold up to about 90L of liquid, for example up to about 120L of liquid, for example up to about 150L of liquid. By providing about 90L of water and sufficient metallic substance, in a typical machine, up to about lOKg of hydrogen gas can be produced. This is approximately the amount required for a typical working day's use of the machine. For example, a standard backhoe loader, with an internal combustion engine with a rated power output of up to 81kW, will typically consume 35L of diesel per day in an average duty cycle. 1kg of hydrogen holds more energy (33kWh) compared to IL of diesel (lOkWh). As a result, a hydrogen powered machine, of similar specification to the diesel powered machine would consume around 10kg per day of hydrogen on a similar duty cycle. In the illustrated embodiment of figure 3, the telehandler 100 includes an engine housing 148 located opposite the operator cab 142, offset from the other side of the working arm 134. The engine 110 is located in the engine housing 148, together with the buffer tank 112, reaction vessel 104 and metallic substance delivery apparatus 106. Locating the buffer tank 112 and reaction vessel 104 proximal the engine reduces the length and / or complexity of the flow path along which hydrogen gas generated in the reaction vessel must travel to reach the engine, hence reducing the chance of leaks. Figure 4 illustrates a machine 200 having an onboard hydrogen generation system 202. The machine 100 is a telescopic handler similar to that shown in figures 2 and 3, with the exception that the prime mover of the machine 200 in figure 4 is an electric motor 210 to provide propulsion, and the energy conversion apparatus is a hydrogen fuel cell 211. A second electric motor (not shown) may be powered by the fuel cell to drive a hydraulic pump (not shown) to power the actuators which move the working arm 234. The features previously described in relation to the previous embodiments of figures 1 to 3 are denoted by the same reference numerals but instead are preceded by the number "2". Figure 5 illustrates a machine 300 in accordance with another embodiment having an onboard hydrogen generation system 302. The features previously described in relation to the previous embodiments of figures 1 to 4 are denoted by the same reference numerals but instead are preceded by the number "3". With reference to figure 5, the machine 300 is a backhoe loader having chassis 336, a loader arm 334 provided proximate a front of the chassis 336 and a backhoe 335 provided proximate a rear of the chassis 336, in relation to a normal direction of travel A'. The backhoe loader 300 is a self-propelled vehicle and includes a prime mover arranged to propel the vehicle. As shown in Figure 5, the backhoe loader 300 is a ground vehicle having a ground engaging propulsion structure including a pair or front wheels 344 and a pair of rear wheels 346. The prime mover is arranged to power the front and rear wheels 344, 346. The prime mover is also arranged to provide power to perform a working operation, such as moving the loader arm 334 and / or backhoe 337. An operator station 342 is located in a substantially laterally central position on the chassis 334 thereof. With reference to figure 6, the energy conversion apparatus 310 is the prime mover, and the prime mover is an internal combustion engine 310 configured to run on hydrogen fuel. The internal combustion engine 310 is arranged to drive at least one of the pairs of front and rear wheels 344, 346 via a suitable mechanical or hydrostatic transmission (not shown). The internal combustion engine 310 is also arranged to drive a hydraulic pump (not shown) to power the actuators 335 which move the working arms (loader arm 334 and / or backhoe 337). The water tank 320, waste reservoir 324, reaction vessel 304, metallic substance delivery apparatus 306 and adjuvant delivery apparatus 330 are mounted under the operator station 342. In a standard diesel powered backhoe loader, the diesel fuel tank may be located under the operator cab, towards the left hand side of the vehicle with respect to the normal direction of travel A'. In a hydrogen powered backhoe loader 300, a diesel tank is not required and one or more of the components of the hydrogen generation system 302 can be mounted in the space where the diesel tank would previously have been. This optimises the layout of the backhoe loader 300 and minimises the changes required to modify a diesel powered backhoe loader design to be a hydrogen powered backhoe loader, and may maintain a similar weight distribution to a diesel powered backhoe loader. In some embodiments, all the components of the hydrogen generation system 302 are mounted in the space that would previously been occupied by the diesel fuel tank, e.g. under the operator cab 342. In the illustrated embodiment, the water tank 320 and waste reservoir 324 are located in the space that would previously been occupied by the diesel fuel tank. This location provides ready access to for an operator to fill the water tank 320 and empty the waste reservoir 324. The hydrogen buffer tank 312 is located forward of the operator station 342, proximal the engine 310. In this way, the flow path for hydrogen between the buffer tank 312 and the engine 310 is minimised. In the illustrated embodiment, the metallic powder delivery apparatus 306 includes a grinder 319 arranged to grind the metallic substance into a powder of a desired granularity in situ. In other embodiments the metallic powder delivery apparatus is arranged to delivery pre-ground powder in a similar way to the first and second embodiments. In an alternative embodiment, the internal combustion engine 310 of the backhoe loader May be replaced by a fuel cell and one or more electric motors in a similar way to the telehandler 200 of Figure 4. It will be appreciated that the hydrogen generation systems 102, 202, 302 of the machines illustrated in figures 2 to 6 operate as described in relation to figure 1. The machines also comprise a controller 32. The controller is configured to control the introduction of reagents, and optionally adjuvant, to the reaction vessel 104, 204, 304, and also to control emptying of the reaction vessel 104, 204, 304 into the waste reservoir 124, 224, 324 as required. With reference to figure 7, the controller 32 monitors the hydrogen pressure 450 in the buffer tank 112, 212, 312. If the pressure in the buffer tank 112, 212, 312 is determined to be below a lower setpoint 452, the controller 32 directs the metallic substance delivery apparatus 106, 206, 306 to adjust a delivery of metallic substance 454 to the reaction vessel 104, 204, 304 to increase the production of hydrogen gas. Similarly, if the pressure in the buffer tank 112, 212, 312 is determined to be above an upper setpoint 456, the controller 32 directs the metallic substance delivery apparatus 106, 206, 306 to adjust a delivery of metallic substance 454 to the reaction vessel 104, 204, 304 to decrease the production of hydrogen gas. The controller 32 is also configured to adjust the delivery of metallic substance 454 in response to an electrical signal provided to the prime mover 110, 210, 310 of demanded power. In other words, in response to the demand for power by the prime mover 110, 210, 310 caused by the requests made of the machine 100, 200, 300 by the operator. The controller 32 is configured to continuously monitor a pressure in the buffer tank 112, 212, 312 and control the reaction taking place in the reaction vessel 104, 204, 304 accordingly. The controller controls the introduction of reagents, and optionally adjuvant, to the reaction vessel 104, 204, 304, such that the amount of hydrogen gas produced does not exceed what can be safely stored by the buffer tank 112, 212, 312. For example, the controller controls the amount of hydrogen produced such that, in the event that the operator directs the machine 100, 200, 300 to stop while a reaction is taking place in the reaction vessel 104, 204, 304, such that demand from the prime mover ceases, the amount of hydrogen produced will not exceed that which can be safely stored in the buffer tank 112, 212, 312. In some embodiments, the controller 32 controls the introduction of reagents, and optionally adjuvant, to the reaction vessel 104, 204, 304, such that hydrogen gas is produced in batches. The controller 32 may also control the introduction of reagents, and optionally adjuvant, to the reaction vessel 104, 204, 304, such that hydrogen gas is produced continuously. It will be appreciated that waste materials that are emptied from the waste reservoir 24, 124, 224, 324 may be processed to obtain the reagents from the waste material. For example aluminium may be recovered from waste AIO2H to be subsequently re-used in a closed loop. In other embodiments the hydrogen generation system may be adapted for use in other self-propelled working machines such as tractors, wheel loaders, slew excavators or the like. In the embodiment of a tractor, a similar system layout may be used to that of the backhoe loader 300 of figures 5 and 6, except that the loader arm 334 and backhoe 337 are omitted and replaced by one or more three-point linkages to mount implements at the front and / or rear of the machine and one or more power take-off shafts to provide power to such implements. Further, the hydrogen generation system may be used in static applications, such as gensets, where the hydrogen is used to generate electricity for use in off-grid locations, either directly via a fuel cell, or via a hydrogen IC engine and an alternator. The hydrogen generation system may further be applicable for use in on-highway vehicles including passenger cars, light and heavy commercial vehicles, and buses. The one or more embodiments are described above by way of example only and it will be appreciated that the variations are possible without departing from the scope of protection 5 afforded by the appended claims.

Claims

1. A hydrogen generation system for mounting to a machine in which hydrogen generated by the system is utilised to provide energy to a prime mover thereof, the generation system comprising:a reaction vessel arranged to hold a water containing liquid;a metallic substance delivery apparatus for selectively delivering a reactive metallic substance to the reaction vessel, which on contact with the liquid reacts to generate hydrogen; anda pressure regulator assembly arranged to deliver the hydrogen at a pressure above atmospheric pressure to an energy conversion apparatus downstream of the generation system.

2. The generation system of claim 1 wherein the pressure regulator assembly is configured to deliver hydrogen at in excess of 3 bar.

3. The generation system of claim 1 or claim 2 wherein the generation system further comprises a buffer vessel downstream of the reaction vessel and configured to hold a volume of hydrogen at an elevated pressure.

4. The generation system of any preceding claim wherein the metallic substance delivery apparatus is configured to deliver the metallic substance in powdered form to the reaction vessel.

5. The generation system of claim 4 wherein the metallic substance delivery apparatus is configured to deliver metallic substance powder when suspended in a liquid to form a paste.

6. The generation system of claim 4 or claim 5 wherein the metallic substance delivery apparatus comprises a receptacle to hold or an interface to mount a replaceable cartridge of metallic substance powder.

7. The generation system of any one of claims 4 to 6 wherein the metallic substance delivery apparatus further comprises a mechanical transfer mechanism such as a screw, a plunger and / or an agitation device to introduce the metallic substance powder to the reaction vessel.

8. The generation system of claim 4 or claim 5 wherein the metallic substance delivery apparatus comprises a grinder arranged to grind the metallic substance into a powder in situ.

9. The generation system of any preceding claim further comprising a liquid delivery system comprising a liquid reservoir separate from the reaction vessel and a delivery conduit thereto.10.The generation system of any preceding claim further comprising a waste reservoir downstream of the reaction vessel and arranged to store reaction products therefrom.11.The generation system of claim 10 when dependent upon claim 9 wherein the liquid reservoir and waste reservoir are of variable volume and are provided in a common housing.12.The generation system of claim 11 wherein the liquid reservoir and waste reservoir comprise flexible bladders.13.The generation system of any preceding claim, the generation system further comprising a reaction adjuvant delivery apparatus arranged to deliver a reaction adjuvant material, such as a caustic material, to the reaction vessel.

14. The generation system of any preceding claim wherein the reaction vessel is arranged to withstand a pressure of at least 10 bar, for example, at least 20 bar.

15. The generation system of any preceding claim further comprising a controller arranged to monitor a hydrogen pressure and adjust at least an amount metallic substance delivered by the metallic substance delivery apparatus to the reaction vessel so as to maintain a predetermined setpoint minimum hydrogen pressure.16.The generation system of any preceding claim, wherein the reaction vessel further comprises a stirring device for mixing the contents of the reaction vessel.

17. A machine comprising an onboard hydrogen generation system according to any preceding claim and a prime mover powered by the hydrogen generation system.

18. The machine of claim 17 wherein the energy conversion apparatus is the prime mover, the prime mover is an internal combustion engine, and the hydrogen is combusted therein to generate kinetic energy.

19. The machine of claim 18 wherein hydrogen is the only fuel combusted in the engine.

20. The machine of claims 18 or 19 wherein the engine comprises at least one fuel injector and the pressure regulator assembly is configured to deliver hydrogen to the fuel injector at a pressure of at least 3 bar.

21. A machine of claim 17 wherein the prime mover is an electric motor and the energy conversion apparatus is a hydrogen fuel cell arranged to convert the hydrogen to electrical energy to power the electric motor.

22. A machine according to any one of claims 17 to 21 wherein the machine is a self-propelled vehicle and the prime mover is arranged to propel the vehicle.

23. A machine according to claim 22 wherein the machine is a ground vehicle comprising a ground engaging propulsion structure and the prime mover powers the ground engaging propulsion structure.

24. A machine according to any one of claims 17 to 23 wherein the machine is an off-highway working machine and the prime mover provides power to perform a working operation, such as to move a working arm thereof.

25. A machine according to claim 24, wherein the machine is a telescopic handler comprising a working arm pivotable about a generally horizontal axis to a machine chassis proximate a rear of the chassis in a normal direction of travel, wherein a free end of the working arm comprises an interface to mount a working implement forward of the machine chassis, and wherein an operator station for a machine operator is offset to a side of the working arm, and wherein at least the liquid reservoir is mounted at least partially under the operator station.26.The machine of claim 25 wherein the prime mover is positioned in a housing offset from the other side of the working arm to the operator station, and at least the buffer vessel is located in the housing.

27. The machine of claim 25 or 26 wherein the waste reservoir is mounted at least partially under the operator station.

28. The machine of any one of claims 25 to 27 wherein the reaction vessel is mounted at least partially under the operator station.29.The machine of any one of claims 26 or claims T1 or 28 when dependent upon claim 26 wherein the reaction vessel is located within the housing.30.The machine according to claim 24 wherein the machine is a tractor, and the working arm is a three point linkage or the machine is a backhoe loader and the working arm is a loader arm and / or backhoe, wherein an operator station is located in a substantially laterally central position on a chassis thereof, and wherein at least the liquid reservoir is mounted at least partially under the operator station.

31. A method of operating a hydrogen generator of claim 15, the method comprising the steps of:a. the controller monitoring the hydrogen pressure; andb. adjusting a delivery of metallic substance to the reaction vessel in response to whether the hydrogen pressure is at least above a lower setpoint pressure value.

32. The method of claim 31 wherein the controller further adjusts the delivery of metallic substance in response to whether the hydrogen pressure is above an upper setpoint value.33.The method of claim 31 wherein the controller further adjusts the delivery of metallic substance in response to an electrical signal provided to the prime mover of demanded power.

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