Field of Invention

The present invention relates to fuel cell systems using cryogenic working fluids, in particular liquid hydrogen fuel cell systems, and more particularly portable or exchangeable liquid hydrogen fuel cell systems.

Background of Invention

Cryogenic working fluids, such as liquified gases (for example hydrogen or helium), must be processed to allow commercially viable transportation. For example, applications with a high consumption of hydrogen, liquid hydrogen is generally used as the preferred storage medium, in situations when transport through a pipeline is neither available nor affordable.

To date, tanks used in road vehicles are installed in the vehicle. With the known tanks, either a local energy source must be used to release the liquefied gas, i.e. hydrogen from the tanks or compressed gas is used. For that case, the gas must be compressed during which heat is released and for the fuelling process, a refrigeration to -40° C is required in order to protect the pressure cylinder in the vehicle against excessive heat of compression. In case that the hydrogen is brought in gaseous form to the hydrogen refuelling station (HRS) there will be a pressure release process carried out multiple times with each transfer into a subsequent tank. This means that the process uses a large amount of energy.

Since refuelling with liquid hydrogen takes place at much lower pressures, the required energy for the transfer from the bunker tank to the vehicle's tank is significantly lower.

However, the following aspects cause the most problems in the known processes:

- liquid pumping energy requirement liberating hydrogen gas (the low viscosity of liquid hydrogen leaves the efficiency at low levels)

- release of gasses during the refilling process, which can provide risk at any refilling location, particularly environments which are subject to safety regulations.

Any future solution for providing power must take into account environmental considerations and global targets to reduce greenhouse gas emissions and limit global warming. The use of carbon-based fuels, for example in internal combustion engines, releases dangerous nitrogen oxides into the atmosphere. An alternative is electricity generated from hydrogen fuel cells. However, due to its low density, hydrogen is difficult to store since gas compression requires either high pressures or high volumes.

In large scale applications, such as for example for refuelling of ships or trains with gaseous fuels, it is necessary to take extreme care regarding the safety. In-depth safety studies are carried out taking into account all operational parameters. Such studies must generally be done for each port or refuelling station. This is very complex because measures must be taken to prevent the formation of flammable gas mixtures and also to eliminate any possible sources of ignition during refuelling. It is desirable to provide a simple, safe system of providing power supply for the end user.

Embodiments of the invention seek to provide systems which overcome some or all of these disadvantages.

Summary of Invention

In the following description, a gasification device is defined as being a device, such as a vapouriser or gas heater which converts a liquefied gas into at least a flow of vapourised gas.

According to a first aspect of the present invention there is provided a fuel cell system comprising a fuel cell system comprising

container defining an enclosed chamber, wherein three sub-chambers are provided inside the enclosed chamber:

a first storage vessel for storing cryogenically liquefied working fluid provided in a first sub-chamber,

a second storage vessel for storing liquefied oxygen, provided in a second sub- chamber,

a fuel cell arrangement provided in a third sub-chamber,

a first gasification device fluidically coupled to the first storage vessel, a second gasification device fluidically coupled to the second storage vessel, wherein the fuel cell arrangement is fluidically coupled to the first gasification device and the second gasification device, and

a control unit configured to control flow between the components within the enclosed chamber; wherein sealing is provided between the three sub-chambers so as to prevent leakage of gases between the sub-chamber.

The enclosed chamber may be substantially sealed such that in normal use, leaking of the working fluid to the atmosphere is substantially prevented.

The cryogenically liquefied working fluid may comprise hydrogen. The cryogenically liquefied working fluid may essentially be liquified hydrogen. The cryogenically liquefied working fluid may comprise liquified natural gas.

The fuel cell system may further comprise a first venting mechanism provided in the first sub-chamber. The fuel cell system may further comprise a second first venting mechanism provided in the second sub-chamber.

The first venting mechanism may be provided in an upper region of the first sub- chamber. The second venting mechanism may be provided in the lower region of the second sub-chamber. A third venting mechanism may be provided in the third sub-chamber. The third venting mechanism may be provided in the upper region of the third sub-chamber.

The fuel cell system may further comprise a control unit configured to operate the first and second venting mechanisms

The control unit may be configured to operate a third venting mechanism, provided in the third sub-chamber.

The control unit may be configured to:

- receive operational data from a plurality of sensors provided within the sub- chambers;

- compare the received operational data against predetermined threshold values in order to detect an emergency or potential emergency;

- if an emergency or potential emergency is detected, operate the system in a safe mode in which at least one of the venting mechanisms is opened.

Valves may be provided to control the flow between the components within the

chamber. In the safe mode, the control unit may operate one or more valves within the system in order to restrict fluid flow. In the safe mode, the control unit may operate one or more valves within the system in order to redirect fluid flow The fuel cell arrangement may include one or more hydrogen fuel cells. The fuel cell system may further comprise a water outlet coupled to the fuel cell arrangement.

The fuel cell system may further comprise a battery pack provided in the enclosed

chamber, wherein the battery pack is electrically coupled to the power cable and to the fuel cell arrangement.

The fuel cell system may further comprise means to convey heat generated into the at least one fuel cell to the first gasification device.

The fuel cell system may further comprise a power cable coupled at one end to the fuel cell arrangement and extending through an exterior wall of the outer chamber such that a second end of the cable extends outside the chamber.

The fuel cell arrangement may comprise at least one fuel cell. The outer container may be gastight, such that the enclosed chamber is essentially sealed from the external environment.

An ambient air inlet may be coupled to the fuel cell arrangement. The air outlet may extend from an outer wall of the outer container to the fuel cell arrangement. A water outlet may be coupled to the fuel cell arrangement. The water outlet may extend from an outer wall of the outer container to the fuel cell arrangement.

The fuel cell system may comprise valves which are provided to control the flow between the components within the chamber

The fuel cell arrangement may include one or more hydrogen fuel cells. The system may comprise an ambient air inlet coupled to the fuel cell arrangement. The system may comprise a water outlet coupled to the fuel cell arrangement. The system may comprise a gas outlet for venting excess or leaked gas. The system may comprise a gas outlet for venting excess or leaked hydrogen. The gas outlet may be routed so as to convey a gas out of an upper portion of the system.

The fuel cell system may comprise a battery pack provided in the enclosed chamber. The battery pack may be electrically coupled to the power cable and the fuel cell arrangement (the at least one fuel cell)

The fuel cell system may comprise means to convey heat generated into the fuel cell arrangement to the gasification device. The gasification device may be a vapouriser, preferably a water bath vapouriser. The gasification device may be a gas heater, preferably an electrical gas heater. The gasification device may use the heat generated in the fuel cell.

The fuel cell system may further comprise flow meters and/or composition detection sensors in suitable positions within the chamber. The meters and/or sensors configured to monitor operational parameters of at least one of the internal components within the chamber. The outputs from these meters and/or sensors may be fed to the control unit to provide additional data for controlling the internal system components. The sensors and/or meters may be configured to detect the presence of one or more gases. The sensors and/or meters may be configured to detect the presence of one or more gases, such as hydrogen, wherein the gas or gases can cause safety concerns when levels exceed a safety threshold. The system may be configured such that upon detection of the gas or the gases, a venting operation to expel the gas is performed, this provides a safe when a detected quantity of the gas or the gases exceeds a threshold value, a venting operation to expel the gas is performed

According to a further aspect of the invention, there is provided a method for producing electrical energy comprising,

within a substantially enclosed chamber

providing a stored quantity of a cryogenically liquefied working fluid in a first sub- chamber;

providing a stored quantity of liquefied oxygen in a second sub-chamber;

conveying the liquefied hydrogen into a third sub-chamber and gasifying the liquefied hydrogen;

conveying the liquefied oxygen into the third sub-chamber and gasifying the liquefied oxygen

supplying the gasified working fluid and the gasified oxygen to at least one fuel cell provided in the third sub-chamber; and

generating electrical energy in the at least one fuel cell

wherein the method further includes proving sealing between the three sub-chambers so as to prevent leakage of gases between the sub-chamber. The cryogenically liquefied working fluid may comprise hydrogen. The cryogenically liquefied working fluid may essentially be liquified hydrogen. The cryogenically liquefied working fluid may comprise liquified natural gas.

The method may further comprise sensing operational data with a plurality of sensors provided within the sub-chambers. The method may further comprise comparing the received operational data against predetermined threshold values in order to detect an emergency or potential emergency. The method may further comprise, if an emergency or potential emergency is detected, operating the system in a safe mode by opening at least one venting mechanism provided in the first or second sub-chamber.

Operating in a safe mode may comprise operative the first venting mechanism, when an emergency is detected in the first sub-chamber. Operating in a safe mode may comprise operative the first venting mechanism, when abnormal data is detected in the first sub-chamber. Operating in a safe mode may comprise operative the second venting mechanism, when an emergency is detected in the second sub- chamber. Operating in a safe mode may comprise operative the second venting mechanism, when abnormal data is detected in the second sub-chamber.

Operating in a safe mode may comprise operative a third venting mechanism, provided in the third sub-chamber.

The method may include in response to an external demand for power, conveying the produced electrical energy from the fuel cell arrangement to outside the enclosed chamber

The method may further comprise controlling the flow of the liquefied working fluid and the flow of the gasified working fluid, in order to control the electrical energy output. The method may further comprise that the working fluid is gasified in gasification

device. The method may further comprise conveying heat generated in the fuel cell arrangement to the gasification device.

The method may further comprise conveying a sub-stream of cryogenically liquefied working fluid from the fuel cell arrangement to provide heat to the gasification device.

The method may further comprise charging a battery provided within the enclosed

chamber from electrical energy generated by the fuel cell arrangement According to the invention operation of the hydrogen fuel cell with oxygen provides an extremely efficient operation, up to a range of 60% to 70% efficiency. The fuel cell system of the invention therefore ensures an efficient and at the same time safe means to supply energy. Furthermore, the hydrogen and oxygen fed system has high load flexibility. Within a few seconds the load can be increased from 10% to

100%.

Operation with liquid oxygen and its evaporation will also allow to replace the air

compressor (control devices associated with the compressor) of the fuel cells by an evaporator. This allows also the elimination of any dust and particulate retention systems. Finally, the ageing as observed in air driven systems, in particular by the presence of noxious gases, e. g. nitrous oxides or sulfurous compounds, will not take place. This will prolong the "cycle time" of the fuel cell.

The fuel cell arrangement may comprise at least one fuel cell.

The fuel cell arrangement may comprise at least one hydrogen fuel cell. The method may further comprise providing a supply of ambient air to the at least one hydrogen fuel cell. The method may further comprise extracting a flow of waste water from the at least one hydrogen fuel cell and conveying the waste water outside the chamber.

The method may further comprise controlling the flow of the liquefied working fluid and the flow of the gasified working fluid in order to control the electrical energy output. The working fluid may be gasified in a gasification device. The method may further comprise conveying a sub-stream of hydrogen from the fuel cell arrangement to provide heat to the gasification device. The method may further comprise conveying a sub-stream of hydrogen from the fuel cell arrangement to provide heat to a vapouriser or a gas heater to provide heat for the step of gasifying.

The method may further comprise conveying heat generated in the fuel cell

arrangement to the gasification device. The method may further comprise conveying heat generated in the fuel cell arrangement to the vapouriser/gas heater.

The method may further comprise conveying a sub-stream of hydrogen from the fuel cell arrangement to provide heat to the gasification device.

The method may further comprise charging a battery provided within the enclosed chamber from electrical energy generated by the fuel cell.

The method may further comprise monitoring operational parameters of at least one the internal components within the chamber. The outputs from these meters and/or sensors may be fed to the control unit to provide additional data for controlling the internal system components.

Whilst the invention has been described above, it extends to any inventive combination of features set out above or in the following description or drawings.

Brief Description of the Drawings

Specific embodiments of the invention will now be described in detail by way of example only and with reference to the accompanying drawings in which:

Figure 1 is a schematic view of a fuel cell system according to a first embodiment of the invention; and

Figure 2 is a schematic view of a fuel cell system according to a second embodiment of the invention.

Detailed description

Figure 1 shows a hydrogen fluid fuel cell system 1 according to an embodiment of the invention.

The system 1 comprises an outer container 2 (also referred to as a shell) and a gas tight container 4 which is provided within the outer container 2. The container 4 defines an enclosed chamber 4a comprising three sub-chambers 10, 20, 30. Sealing 1 1 , 21 is provided between the sub-chambers 10, 20, 30, so as to ensure that in use there is no leakage of any gas present in one of the sub-chambers into another sub-chamber. In a first sub-chamber 10 is provided a first storage vessel 12. In a second sub- chamber is provided a second storage vessel 22. In a third sub-chamber 30 are provided a first gasification device 32 (which may be a vapouriser or a gas heater), a second gasification device 34 (which may be a vapouriser or a gas heater) and a fuel cell arrangement 36.

The system also includes a control unit 50. The fuel cell arrangement 36 comprises one or more hydrogen fuel cells.

Valves (61 , 62, 63, 63, 64, 65, 66, 67, 68) are provided in the flow lines between the internal system components in order to control the flow between the components. The control unit 50 controls the operation of the valves (61 , 62, 63, 63, 64, 65, 66, 67, 68). The system is provided with a first vessel filling connection 14 which is used by an operator to fill/refill the vessel. The first vessel filling connection comprises: a filling valve 61 , a fill coupling 14b, and a gastight outer lock 14a. The gastight outer lock 14a is configured such that it can be opened only by operated in a certified EX-Zone safe filling-station.

The first storage vessel 12 is suitable for storing a liquefied cryogenic working fluid. This means that the vessel must be made from a suitable material such as low- temperature steel or cryogenic grade steel, to ensure resilience against the low operating temperatures. The cryogenic working fluid may be any suitable liquefied gas, such as liquid helium, liquid hydrogen, liquid nitrogen, liquefied air or liquefied natural gas (LNG). In a particularly advantageous embodiment, liquefied hydrogen is used. To exist as a liquid, hydrogen must be cooled and then stored below the critical point of hydrogen 33K.

The second storage vessel 22 is suitable for storing liquefied oxygen. This means that the vessel must be made from a suitable material such as low-temperature steel or cryogenic grade steel, to ensure resilience against the low operating temperatures. A second vessel filling connection 24 is provided which is used by an operator to fill/refill the vessel. The second vessel filling connection comprises: a filling valve 68, a fill coupling 24b, and a gastight outer lock 24a. The gastight outer lock 24a is configured such that it can be opened only by operated in a certified EX-Zone safe filling-station.

Sensors 19, 29, 39a and 39b are provided in the three sub-chambers. The sensors 19, 29 and 39 send output signals to the control unit 50.

The first sub-chamber 10 is provided in an upper portion with a first venting mechanism 13. In normal use, the first venting mechanism 13 is use closed such that the first sub- chamber 10 is substantially sealed.

The second sub-chamber 10 is provided in a lower portion with a second venting mechanism 23. In normal use the second venting mechanism 23 is closed such that the sub-chamber 10 is substantially sealed.

The first sub-chamber 10 is provided in an upper portion with a first venting mechanism 13. The first venting mechanism 13 is in normal use closed such that the sub-chamber 10 is sealed.

The control unit 50 controls the operation of the venting mechanisms 13, 23, 33. The operation is described in more detail below.

Additionally, flow meters and/or composition detection sensors may be provided in suitable positions within sub-chambers (not show in the figures). The outputs from these meters and/or sensors are fed to the control unit 50 to provide additional data for controlling the internal system components.

The outer container 2 is a rigid-frame container and provides an enclosed chamber 2a in which the other components are housed. The outer container may be, for example, an ISO-container. The enclosed chamber 4a is an essentially sealed chamber, such that in normal use, any vapour or gas generated inside the chamber 4a does not leak into the external environment.

The first gasification device 32 may be a vapouriser, and a preferred type is a water- bath vapouriser. Alternatively, a gas heater, such as an electrical gas heater may be provided to gasify the working fluid.

The at least one fuel cell 36 is provided appropriate to the cryogenic working fluid. For example, a hydrogen fuel cell is provided when the working fluid is hydrogen. Further, the size and configuration is selected in accordance with the power demand of the intended application.

An electricity meter 38 measures the power consumption.

The fuel cell is connected to a power cable 52, which extends out of the container 2. A gas tight transition 54 is provided at the point where the power cable 54 passes through the wall of the containers 2 and 4. The electricity can then be conveyed for use or into storage.

Waste water is extracted through the water outlet 35 to be disposed of or used as required. The flow through the outlet 35 is controlled by the control unit 50.

Air inlet to the fuel cell. The air inlet provides cooling air and an alternative/additional source of oxygen. The operation of the fuel cell system 1 will now be described.

The liquefied cryogenic working fluid (liquefied gas) is stored in the first storage vessel 12 and liquefied oxygen is stored in the second storage vessel.

In normal operation (power generation mode), when there is a demand for energy supply, the control unit 50 operates the valve 62 to allow a defined quantity of liquefied gas to be transferred into the gasifying device 32 and then into the fuel cell 36. The control unit 50 operates the valve 67 to allow a defined quantity of liquefied oxygen to be transferred into the gasifying device 34 and then into the fuel cell 36. Electrical power generated by the fuel cell arrangement 36 is supplied through the cable 52 and can be used to provide energy for any desired external use. Signals are received by the control unit 50 from some or all of the internal system components. This allow the control unit to control operation of each of the valves 61 , 62, 63, 63, 64, 65, 66, 67, 68, thereby controlling the flow of fluids through the internal system components.

In order to gasify the cryogenic liquid (for example the liquefied hydrogen) in the gasification device32, the gasification device 32 must be supplied with heat. In a preferred embodiment, heat generated in the fuel cell arrangement 36 is supplied back into the gasification device 32. This is not illustrated in the figure.

Alternatively, an external heat source can be used, for example ambient heat from the local atmosphere.

The sensors 19, 29, 39a and 39b monitor each of the sub-chambers 10, 20, 30. The sensors monitor operational parameters, including but not limited to: the gas composition, and pressure levels

In an emergency situation, for example if hydrogen leaks into the first sub-chamber, oxygen leaks into the second-sub-chamber, or if a pressure increase in the one of the sub-chambers is detected, the control unit 50 sends a signal to an external alarm (not shown in this figure). The alarm may be an audible and/or a visual alarm. The control unit 50 can also be configured to transmit a signal to a remote receiving station in order to notify an operator.

If an emergency situation or a potentially dangerous situation is detected, the control unit 50 is configured to operate the system in a safe mode. Safe mode operation involves operation of appropriate valves within the system to restrict fluid flow as necessary, and evacuation of potentially dangerous gas build up.

In order to evacuate potentially dangerous gas and/or heat build-up, the control unit operates each of the sub-chamber venting mechanisms 13, 23, 33 independently or in combination as necessary.

If gaseous hydrogen is detected in the first sub-chamber 10 above a predetermined threshold value, the first venting mechanism 13 is opened and the gaseous hydrogen which will be present in the upper portion of the chamber due to its relatively low density (<90 g/m3) will evacuate the first sub-chamber 10 upwards through the first venting mechanism 13. In a further embodiment, not shown, a chimney stack is provided above the first venting mechanism 13 to allow the hydrogen to be vented into the atmosphere at a remote location. This may be advantageous for example, in a situation where the container 2 is provided within an enclosed space or within a vessel such a ship where there no free convection. In general, restricted clearance or confined space above the container must not be permitted without suitable ventilation. Free convection of blowing off gases must be granted by a vent or venting pipe. Due to of the low density of gaseous hydrogen, convection velocities will be very high

If gaseous oxygen is detected in the second sub-chamber 20 above a predetermined threshold value, the second venting mechanism 23 is opened and the gaseous hydrogen which will be present in the lower portion of the second sub-chamber 20 due to its relatively high density (1 ,141 kg/m3) will evacuate the chamber downwards through the second venting mechanism 23. In a further embodiment, not shown, a pipe is provided below or adjacent to the second venting mechanism 33 to convey the evacuated gas to be vented into the atmosphere at a remote location.

The second sub-chamber 20 and second venting mechanism 23 are constructed in order to ensure that no grease, oil or asphalt is to be touched with any liquefied oxygen.

If excess heat, or abnormal gas quantities are detected within the third sub-chamber, the third venting mechanism 33 is operated and heat or gas is released upwards. In a further embodiment, not shown, a chimney stack is provided above or adjacent to the third venting mechanism 33.

Figure 2 shows a cryogenic working fluid fuel cell system 101 according to a second embodiment of the invention. In Figure 2, features similar to that in the above embodiment are given corresponding reference numerals. For simplicity, some reference signs are left out of the figure.

The system 101 comprises an outer container 102 and a gas tight container 104 defining an enclosed chamber 104a. As in the above example, the enclosed chamber 104a is divided into three sub-chambers 1 10, 120, 130. Also, similarly to the above example, the system includes: a first storage vessel 1 12, second storage vessel 122, first and second gasification devices 132, 134; a fuel cell 136; and a control unit 150.

Figure 2 shows an alarm 140 which is operated by the control unit 150. As described above, the system can be provided with any suitable alarm including but not limited to: audio, visual, tactile.

The system 101 further comprises in the first sub-chamber 1 10: a pressure regulator 180, and a gas processing box 182. The gas processing box is configured to convert the H2 into a harmless gas, the gas processing box may be example a small fuel cell, which creates electricity, which will be destroyed by an electrical heating or lightning element, or by catalytic burning

The second embodiment is a so-called hybrid design, since it further includes a battery pack 170. The battery pack 170 is electrically coupled to the fuel cell 136 via line 172, and to the power cable 152 via line 173.

The second embodiment operates in the way described above with reference to the first embodiment. However, in addition, the battery pack 170 can be used to provide additional energy output if there is a spike in demand or at peak loads. When there is no external power load on the fuel cell 136, the fuel cell 136 can charge/recharge the battery via line 172.

As with the above embodiment, heat generated in the fuel cell 136 is supplied back into the first gasification device 132 (this flow is not shown in Figure 2).

During operation of the hydrogen fuel cell(s), oxygen is supplied from the second storage vessel 122. Water generated by the fuel cell is extracted through the water outlet 135 to be disposed of or used as required.

In further embodiments, not shown in the figures, heat generated by the fuel cell(s) is routed back to the gasification device in order to provide the heat necessary to convert the liquefied working liquid and possibly liquid oxygen into a gas. It will be appreciated that in all of the above described embodiments, heat from the fuel cells can be conveyed to the gasification device.

With a fuel cell system of the invention, the user can use simply attached the power cable 52, 152 to any system requiring energy (not shown in the figure). The simple plug-and-play solution of the invention means that the user can easily replace one fuel cell system with another. The result is a quick and easy change over meaning a consistent power supply can be ensured. Depending on the user requirements, specific filling levels can be supplied. Refilling losses can be avoided because the containers can be refilled directly at the working fluid condenser, in particular, for a system incorporating hydrogen as the working fluid, at the hydrogen condenser. Since the user is supplied with a complete unit, they do not have to handle any potentially dangerous gases themselves. Furthermore, the fuel cell maintenance is no longer carried out in the location that the fuel cell is used, for example in a vehicle, since the with the removable system of the invention, when necessary the fuel cell can be maintained when the system is removed from the use location. No additional tank systems are required, because known fuel cell technology can be incorporated into the system of the invention.

The control unit 50, 150 receives inputs from sensors and meters provided within the system components and monitors operational parameters of the fuel system. The control system 5 is provided with communication equipment which is configured to remotely link to a receiver module in a working fluid filling station. The control unit sends operational status data (GPS position, power consumption) to the filling station, which enables the filling station to calculate estimated requirements for exchange of the fuel cell system 1 .

The fuel cell system of the invention, in particular hydrogen, fuel cell systems according to the invention, can be used in a wide variety of applications, for example, but not limited to, road vehicle such as lorries or cars, trains, ships, construction vehicles. For such applications, hydrogen fuel cell system exchange and refilling stations can be provided at suitable terminals, such as ports, transport hubs and train depots.

The fuel cell system can also be used as a stand-alone, or off-grid, electricity supply, for example in remote locations for festivals, camping, construction sites or sporting events, or in humanitarian mission in disaster areas

It will be appreciated that the dimensions of the system can be varied in accordance with the application. For example, larger systems can be provided for high power demand applications with a long running time between refill opportunities.

All of the invention has been described above with reference to one or more preferred embodiments. It will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.