GB2541734A

GB2541734A - Dewar vessel storage apparatus

Info

Publication number: GB2541734A
Application number: GB1515344.8A
Authority: GB
Inventors: Winand Henri; Chellappa Anand; Leonard Adcock Paul
Original assignee: Intelligent Energy Ltd
Current assignee: Intelligent Energy Ltd
Priority date: 2015-08-28
Filing date: 2015-08-28
Publication date: 2017-03-01
Anticipated expiration: 2035-08-28
Also published as: EP3341645A2; WO2017037429A3; WO2017037429A2; GB201516763D0; GB201515344D0; GB2541752A; US20200224825A1; GB2541734B; EP3341645B1; US11137116B2

Abstract

A Dewar vessel storage apparatus configured to hold at least two Dewar vessels 2 containing liquefied gas or cryo-compressed gas, comprises a box having an outer, thermally insulating wall 3 and a plurality of insulating cavities 5. Each cavity is configured to receive a single Dewar vessel and is thermally insulated from each other cavity. A thermally insulating bung 7 is configured to close an open end of each cavity. A ventilation assembly comprises at least one conduit 8 within the box configured to provide for venting of gas released from the Dewar vessels when stored in the respective cavities of the box, the ventilation assembly configured to provide a gas outlet flow path from each cavity.

Description

DEWAR VESSEL STORAGE APPARATUS

This disclosure relates to a dewar vessel storage apparatus and, in particular, a cryogenic gas storage apparatus. In particular, it provides a dewar vessel storage apparatus for storing liquefied natural gas, helium, nitrogen, hydrogen or other cryogenic liquids orcryo-compressed gasses or cryogenic liquid or slush. The invention also relates to a method of providing a liquefied or cryo-compressed gas or slush to a point of use.

According to a first aspect of the invention we provide a dewar vessel storage apparatus configured to hold at least two dewar vessels containing liquefied gas or cryo-compressed gas, comprising; a box having an outer, thermally insulating, wall; the box comprising a plurality of insulating cavities, each cavity configured to receive a single dewar vessel and is thermally insulated from each other cavity; each cavity including a separately removable thermally insulating bung configured to close an open end of its cavity; a ventilation assembly comprising at least one conduit within the box configured to provide for venting of gas released from the dewar vessels when stored in the respective cavities of the box, the ventilation assembly configured to provide a gas outlet flow path from each cavity.

This is advantageous as the apparatus provided a cryogenically insulated storage box for holding at least two dewar vessels for transportation or storage. The ventilation system that extends at least in part in the box, to connect to the cavities, advantageously provides for venting of boil-off gas from the dewar vessels. The bungs prevent disturbing the insulation around another dewar vessel when one is removed.

Optionally, the outer, thermally insulating, wall and/or insulation between each cavity and/or bung comprises at least one of; a vacuum insulated panel utilizing a multilayer insulation blanket in the vacuum gap; a vacuum jacket or panel with no multilayer insulation blanket in the vacuum gap; a wall utilizing spray on foam insulation; and a wall incorporating aerogel insulation.

Optionally, each cavity and its associated bung is configured complimentary to the shape of the dewar vessel it is configured to receive such that there is substantially no air space when the dewar vessel is received in the cavity and the bung is in place. The bungs are advantageous as they avoid the need to expose other dewar vessels to the ambient environment when removing one of the dewar vessels. Further, providing a tight fitting cavity and bung reduces the chance for air to freeze around the dewar vessel. It will be appreciated that manufacturing tolerances and surface finishes may allow for a very small quantity of air to be present around the dewar vessel. In other examples, the apparatus may be configured to provide for introduction of a fluid other than air into the space around a dewar vessel when in place in the cavity with the bung closing the open end. The fluid may have a freezing/condensing point lower than a predetermined temperature expected to be experienced within the cavity. Thus, the cavity and/or bung may have means to introduce said fluid. In other examples, the bung provides a hermetic seal and the cavity and/or bung includes means to introduce a vacuum within the bunged cavity around the dewar vessel.

Optionally, the outer walls of the box may have a thermal performance so as to achieve a thermal input from the surroundings of less than 100W (or less than 10W), such as when containing a cryogenic dewar vessel (which may contain fluid at less than 100K, 80K, 60K, 40K, 20K, 10K or 5K). It will be appreciated that the thermal performance of the apparatus is important if it is to store the dewar vessels for an extended period of time.

Optionally, the box includes an aperture configured to provide access to the cavities, said aperture closed by a removable thermally insulating lid. A combination of a lid and bungs is particularly advantageous to provide the required thermal performance as well as avoiding disturbing other dewar vessels when removing a dewar vessel. Optionally, the lid comprises at least one of; a vacuum insulated panel utilizing a multilayer insulation blanket in the vacuum gap; a vacuum jacket or panel with no multilayer insulation blanket in the vacuum gap; a wall utilizing spray on foam insulation; and a wall incorporating aerogel insulation.

Optionally, the ventilation assembly includes a releasable connector configured to releasably couple the outlet flow path of one of the cavities to a pressure relief valve of a dewar vessel inserted into said one of the cavities for receiving boiled-off fluid from the dewar vessel. In other examples, the ventilation system receives boiled-off fluid from the cavity. The cavities may be sealed.

Optionally, the releasable connector is arranged at a base of the cavity such that a connection is made between the dewar vessel and the ventilation assembly when the dewar vessel is substantially completely inserted into said cavity.

Optionally, the ventilation assembly comprises a manifold configured to connect to each cavity and provide a common ventilation flow path, the manifold providing the outlet flow path from each cavity. In other examples, the ventilation assembly provides for individual vents for each cavity.

Optionally, the ventilation assembly is configured to; connect the gas outlet flow path from at least one of the cavities to atmosphere; connect the gas outlet flow path from at least one of the cavities to burner or catalyser for consuming the vented gas; connect the gas outlet flow path from at least one of the cavities to an electrochemical fuel cell, the fuel cell configured to use gas vented from the one or more dewar vessels to generate electricity; or connect the gas outlet flow path from at least one of the cavities to a gas store; or provide a combination of the above.

Optionally, the ventilation assembly includes a controllable valve for controlling the receipt of gas into the gas outlet flow path of at least one or more or all of the cavities. In other examples, the controllable valve is provided in the dewar vessel. In another example, a control element, such as an electromagnetic actuator, is provided in the box for controlling a controllable valve, such as a solenoid valve, in the dewar vessel. Power required to actuate these control elements may be provided by a battery or by a fuel cell that consumes vented hydrogen or by a combination of one or more power sources.

Optionaliy, the apparatus includes a refrigeration or cryogenic cooling system configured to cool an interior of the box. Optionally, the refrigeration or cryogenic cooling system is powered at least by gas vented from the dewar vessel(s) contained within the cavities.

Optionally, the box is configured to house a sacrificial gas storage vessel configured to continuously or intermittently vent its contents over a predetermined time period and thus lower its temperature, the box configured to provide for connection of the sacrificial gas storage vessel to an outlet to receive the gas released therefrom and a heat transfer element configured to cool an interior of the box and/or the cavities using the lowered temperature of the sacrificial cavity.

Optionally, the predetermined time period is selected to exhaust its entire contents over an intended use period. Optionally, the sacrificial dewar vessel is predetermined or built into the box. Alternatively the ventilation system controls which dewar is the sacrificial dewar by way of the connection between the ventilation system and an inserted dewar vessel.

Optionally, the heat transfer element comprises at least one of; one or more a heat pipes; a refrigeration system; a cryogenic cooling system; and a thermal mass comprising a first part that extends around the sacrificial dewar vessel and a second part that extends around at least one of the cavities, the first part thermally connected to the second part to provide heat transfer between the parts.

The refrigeration/cryogenic cooling system may include a compressor, condenser, and a working fluid.

Optionally, the sacrificial dewar includes a pressure relief valve to provide for venting of its contents and said pressure relief valve is configured at a lower pressure to any other dewar vessel received by the apparatus.

Optionally, the apparatus includes a dewar vessel filling assembly within the box and configured to fill one or more dewar vessels received within the cavities, the filling assembly comprising a releasable filling connector configured to releasably couple to a dewar vessel inserted into one of the cavities and a fill port for receiving a flow of gas to fill the dewar vessel, the assembly configured to direct gas from the fill port to the dewar vessel connected to the connector. Optionally, the fill port comprises a removable connector for connecting to a (cryogenic) dewar vessel filling apparatus.

Optionally, the dewar vessel filling assembly is configured to circulate gas through the dewar vessel(s) when filling the dewar vessel(s) wherein the filling assembly comprises a circulation loop having an inflow section, including the fill port and the filling connector to receive the gas and direct to the or each dewar vessel received within a respective cavity and an outflow section to receive the gas from the or each dewar vessel within a respective cavity for recirculating to the inflow section. Optionally, the ventilation assembly forms at least part of the outflow section when filling the or each dewar vessel. Thus, the dewar vessel filling assembly may connect to the fill port and a vent of the ventilation system.

Optionally, the box includes a carrying structure configured to allow one or more users to carry the dewar vessel storage apparatus.

Optionally, a thermal mass is configured to extend around the at least one of the cavities, the thermal mass comprising a thermally conductive material relative to the insulation of the outer wall and is surrounded by the outer wall. Optionally, the thermal mass has an isobaric volumetric heat capacity of greater than 2 J.cm'^.K ^

Optionally, the box has outer walls formed of cryogenic insulation, wherein the interior of the box is divided, at least in part, by further cryogenic insulation into a plurality of cavities. Optionally, the cavities are configured in terms of size and shape to closely engage with a wall of the dewar vessel inserted therein.

According to a further aspect of the invention we provide a dewar vessel storage apparatus configured to hold at least one dewar vessel containing liquefied gas or cryo-compressed gas, comprising; a box having an outer, thermally insulating, wall; the box comprising at least one insulating cavity, the or each cavity configured to receive a single dewar vessel and is thermally insulated from any other cavity; the or each cavity including a separately removable thermally insulating bung configured to close an open end of its cavity; a ventilation assembly comprising at least one conduit within the box configured to provide for venting of gas released from the dewar vessel(s) when stored in the respective cavity(ies) of the box, the ventilation assembly configured to provide a gas outlet flow path from the or each cavity.

Thus, a dewar vessel storage apparatus for at least one dewar vessel may be provided. It will be appreciated that all of the optional features of the first aspect apply equally to this aspect as appropriate.

According to a further aspect of the invention we provide a method of providing a liquefied or cryo-compressed gas or slush to a point of use comprising; providing a dewar vessel storage apparatus as defined in any other aspect; providing a plurality of dewar vessels (or at least one) for receiving the liquefied or cryo-compressed gas or slush; transporting the dewar vessel storage apparatus having the plurality of dewar vessels (or at least one) stored therein to the point of use; and providing for individual removal of one of the dewar vessels at the point of use.

Optionally, the method includes filling the plurality of dewar vessels (or at least one) while stored within the dewar vessel storage apparatus. Optionally, the step of filling includes circulating gas through the dewer vessel(s).

There now follows, by way of example only, a detailed description of embodiments of the invention with reference to the following figures, in which:

Figure 1 shows a cross sectional view of a first example of a dewar vessel storage apparatus;

Figure 2 shows a cross sectional view of a second example of a dewar vessel storage apparatus including a sacrificial dewar;

Figure 3 shows a cross sectional view of a third example of a dewar vessel storage apparatus including means for providing active refrigeration/cryogenic cooling; and

Figure 4 shows a cross sectional view of a fourth example of a dewar vessel storage apparatus including a fuel cell.

The transport of liquefied or cryo-compressed gases or slushes is typically provided by large, well-insulated tankers that carry a large quantity (such as 20,000 litres) of the gas and, at a desired locality, transfer a portion of the gas to a local storage facility, which may have containers of a volume of 1000 or more litres. Such tankers may include diesel powered refrigeration or cryogenic units to maintain the gas in its liquefied or cryo-compressed state during transport or may boil off part of the liquid utilising the latent heat of vaporisation to keep the liquid cold.

The dewar vessel storage apparatus of the invention provides for transport of individual, separate quantities of liquefied or cryo-compressed gases or slushes packaged in a plurality of dewar vessels (or vacuum insulated vessels) and stored within the dewar vessel storage apparatus. Slush hydrogen contains some hydrogen in the solid form (13.8 K, 1 atm). The dewar vessels therefore may be cryogenic dewar vessels.

The provision of hydrogen in this way is advantageous as hydrogen is a suitable fuel for electrochemical fuel cell power systems. Compressed hydrogen sources at both 350 bar and 700 bar are limited by gravimetric capacities of about 4 wt.-% and volumetric capacities of about 20 g H2/L. Practical targets for widespread commercialization is > 6 wt.-% and > 30 g/L. For aircraft applications employing Proton Exchange Membrane (PEM) fuel cell systems, such as Unmanned Aerial Vehicles, gravimetric and volumetric capacity is a critical design factor with a requirement that may be at least 6wt.-% and 40 g/L.

The boiling point of hydrogen is 20 K (critical temperature = 33.2K; critical pressure = 13 bar). Thus, a hydrogen storage vessels such as a dewar vessel may allow for continuous boil off of hydrogen to prevent over pressurization of the dewar vessel. Pressure relief valves are used to vent hydrogen vapour when the pressure increases to a pre-set value, which may be about 5 bar. For example, assuming a heat loss of 1 watt, a 5 kg liquid hydrogen dewar vessel within the apparatus 1 may not require boil-off venting until about 5 days of dormancy.

When used to power PEM fuel cell systems, it may be the boil off hydrogen that is supplied to the fuel cell. However, before use and in transit, the boil off must be managed effectively. Thermal management may therefore be important to minimize boil off rates during storage or shipment of liquid hydrogen vessels, while providing sufficient rates to support PEM fuel cell systems (or hydrogen combustion engines). Generally, this balance is achieved by using well insulated dewar vessels that contain internal heating elements.

Figure 1 shows a dewar vessel storage apparatus 1 configured to hold at least two dewar vessels 2. Four dewar vessels 2 are shown which are configured to contain liquefied gas or cryo-compressed gas or slush. In this example, the gas is hydrogen but it will be appreciated that the apparatus 1 has application for storing dewars of other fluids, such as helium or nitrogen among others. The apparatus comprises a box 3 having an outer, thermally insulating, wall 4. The box comprising a plurality of insulating cavities 5, each cavity 5 configured to receive a single dewar vessel 2. Thermal insulation 6 extends between the cavities 5 to thermally insulate them from each other. Each cavity may comprise an elongate bore extending into the box which is surrounded by thermally insulating material. Each cavity 5 has an open end through which the dewar vessel 2 is inserted into the cavity and is closed by a separately removable thermally insulating bung 7. Thus, with the bung 7 in place, the dewar vessel 2 within the cavity may be completely surrounded by insulating material. Given that each cavity 2 has an associated bung 7, an individual cavity can be opened, to remove a dewar vessel for example, without affecting the insulation that surrounds another dewar vessel in a different cavity. Further, the apparatus 1 includes a ventilation assembly 8 within the box configured to provide for venting of gas from the dewar vessels 2 when stored in the respective cavities 5 of the storage apparatus 1. The ventilation assembly 8, in this example, provides a conduit 10 to each cavity 5 for connection to each dewar vessel 2 which provides a gas outlet flow path from each cavity 5.

The arrangement of the apparatus and the way of packaging the gas in individual dewars is particularly advantageous as an end user is able to remove one of the dewar vessels without substantially affecting the insulation that surrounds any of the others in the box. This is particularly convenient as each dewar vessel may be sized to fit a particular application. Therefore, a user has a ready supply of dewars, thermally insulated in the box, to remove as and when required. For example, the gas may be hydrogen and the application may be fuel cell powered autonomous aircraft. In this example a user can remove a dewar vessel from the box, load it into the aircraft to act as a fuel source, and launch the aircraft. Thus, the dewar vessels comprise a removable fuel source or tank for an application. When the autonomous aircraft returns or another aircraft is to be launched, a further dewar vessel can be removed from the box and installed as described above.

The box 3 may be cuboidal although it may be cylindrical. It will be appreciated that the outer wall 4 of the box 3 and any walls interior to the box, such as those separating the cavities, and the bungs 7 may be thermally insulated sufficiently to store a liquefied gas or cryo-compressed gas in a dewer vessel, for at least 1 hour, 5 hours, 10 hours, 12, 24, 72 or more hours without losing more than 10% of the contents due to boil-off (in a 25 deg C ambient environment). The outer, thermally insulating, wall may comprise a multi-layer Insulation (MLI) or a super insulation (SI) material inside a high or soft vacuum respectively, a vacuum insulated wall or panel (VIP) or be formed of a plurality of vacuum insulated panels or combination of the above. The interior walls may also include MLI, SI or VIP. Thus, the box 3 may be considered to be a dewar vessel for receiving a plurality of dewar vessels 2. The walls 4 or panels may be of metal, such as stainless steel, and include a hollow interior for the vacuum. The walls or panels may be infilled with any appropriate insulating material, such as an aerogel, MLI or SI. The thermal insulation may reduce or minimize heat transfer from the atmosphere via radiation through the insulation. conduction through the insulation and other heat losses through hydrogen inlet and outlet fittings and conduits. Suitable insulation arrangements may comprise a vacuum jacket or panel utilizing a multilayer insulation (MLI) blanket in the vacuum gap; a vacuum jacket or panel with no MLI; a single-walled tank utilizing external spray on foam insulation; and a single-wailed tank utilizing aerogel insulation. The vacuum jacket or panel with and without a MLI blanket may provide the lightest thermal insulation design solution.

The cavity 5 may be configured to receive a specific size of dewar vessel and thus may include a head space adjacent the open end of the cavity once the dewar vessel has been received therein. The head space may include a wall 11 that is complimentary to an outer surface of the bung 7 such that the bung is seaiingly received within the cavity. The seal formed between the bung 7 and the cavity 5 may be hermetic. The head space wall 11 and/or the bung 7 may include sealing structures, such as seal(s) to seal therebetween. The cavities 5 may be substantially cylindrical, cuboidal or any other shape that may be complimentary to the dewer vessel it is configured to receive. Further, the bung may be configured to fit closely adjacent to, such as against, the dewer vessel 2 to reduce the quantity of air surrounding the dewer vessel. For example, the bung 7 may fill substantially all of the space around the dewar vessel, which may reduce the quantity of air that may freeze around the outside of the dewar. Thus, a lower face of the bung may be complimentary to the shape of the base (the end opposite the valves) of the dewar vessel 2. Further, when the dewar vessel is removed and the bung replaced, the air in the space will cool/liquefy and a partial vacuum may form. If the bung is sealed then it will prevent further air entering the cavity. The bung 7 may include a pressure control/relief valve.

The bung 7 and/or cavity 5 may include conduits, which may terminate in ports, to provide for introduction of a storage fluid within the bunged cavity and around the dewar vessel. The storage fluid may be such that it does not condense or freeze in use when subjected to the cold conditions surrounding the dewar vessel 2. Alternatively, the conduits may provide for removal of air from the bunged cavity to form a vacuum/partial vacuum around a dewar vessel stored within the cavity.

In this example, the dewar vessel storage apparatus 1 includes a removable lid 12. Thus, the box 3 includes an aperture 13 configured to provide access to the bungs 7 and cavities 5 and the aperture 7 is closed by the removable lid 12. The removable lid 12 may comprise a vacuum insulating panel or may be of an insulating material as described above in relation to the box 3. In other examples, it is not specifically configured to provide for thermal insulation, although by virtue of its material it may have some thermal insulating properties. The lid 12 may include an engagement structure, such as a rim or flange, to engage with a complimentary engagement structure on the box 4, such as at the perimeter of the aperture 13. The engagement structure may comprise hinges and/or clasps and/or slots to secure the lid in place during use. In other examples, the lid 12 is provided without the bungs 7. Further, the bungs 7 may be configured to close a subset of the cavities.

The dewar vessels 2 may be of known design and may be configured to hold at least or up to 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5 kg of hydrogen.

The dewar vessels 2 may include pressure release valves to release gas therein to relieve the pressure within the vessels as the fluid within the dewar vessel boils off. Thus, the ventilation assembly 8 of the apparatus 1 is configured to receive said gas so that uncontrolled accumulation of gas within the apparatus 1 is prevented. The pressure release valves may form part of a fluid outlet 9 of the dewar vessels 2. In this example, the ventilation assembly comprises a network of conduits within the box 3 that connect to each cavity 5 and provide a flow path for any gas within the cavities 5 to flow into the network of conduits and (possibly) to atmosphere via a vent 14 that extends through the outer wail 4.

In particular, the ventilation assembly 8 comprises a manifold 15 having a common flow path conduit 16 that has a plurality of branches extending therefrom for connecting to each cavity 5. The common flow path conduit 16 connects to the vent 14. It will be appreciated that other network arrangements may be used such as each cavity 5 connecting to a separate conduit that provides a direct vent to atmosphere or elsewhere. Further, it will be appreciated that the vent may not open to atmosphere. Instead, the ventilation assembly 8 may open into a gas storage volume (not shown) for storing the gas from the dewar vessels at a higher temperature.

The outlet flow path 10 may thus connect to the cavity 5 or may be configured to connect to the dewer 2 within the cavity 5.

Further, in this example, the ventilation assembly 8 includes a plurality of releasable connectors 15, each cavity 5 including a connector for releasably coupling to a dewar vessel. The connector 5 may be a standard connector or othenwise compatible with the structure of the inlet/outlet of a dewar vessel 2. Thus, when a dewar vessel 2 is inserted into the cavity it releasably and securely engages with the connector 15, which provides a sealed and direct connection to the conduits of the ventilation assembly 8. Thus, when the pressure relief valve of a dewar vessel 2 is actuated by excessive pressure due to gas therein boiiing off, said reieased gas is received into the ventilation assembiy 8 through the connector 15.

The reieasabie connectors 15 are arranged at a base of each cavity 5 such that a connection is made between the dewar vessel 2 and the connector 15 of the ventilation assembiy 8 when the dewar vessei 2 is substantially completely inserted into said cavity 5. In other examples, the connectors may be arranged elsewhere in each cavity 2. However, providing the connectors 15 at the base of the cavity is advantageous as the walls of the cavity guide the dewar vessel into engagement with the connector 15.

While in the example of Figure 1, the vent 14 is to atmosphere, in other examples the ventilation assembly 8 may connect the gas outlet flow path 10 from at least one or all of the cavities 5 to a burner or catalyser or fuel cell for consuming the vented gas (not shown).

In this example, a neck of the dewar vessels 2 includes the pressure relief valves and any other valves required to control the filling and dispensing of fluid from the dewar vessels. On coupling of the dewar vessel to the connector 15, a sealed connection is made and, on removal, the conduits of the ventilation system may be self-sealing.

In another example, the ventilation assembly 8 includes a controllable valve for controlling the receipt of gas into the gas outlet flow path of at least one or more or all of the cavities or dewars vessels. Preferably, the dewar vessel includes the controllable valve. The controllable valve may comprise a solenoid valve. The valve or valves may be used to close off the connection to the ventilation assembly 8 for a particular cavity 5 or dewar vessel 2, such as one that does not contain a dewar vessel 2 or due to a fault. The ventilation assembly 8 may provide for a vent for each cavity or groups of cavities.

The apparatus 1 is further configured to provide for filling of the dewar vessels 2 in situ within the box 3. The filling of the dewar vessels 2 while loaded in the box 4 may be advantageous as the interior walls/surfaces of the box 3, such as those in closest contact with the dewar vessels 2 can be cooled by the dewar vessels as they are filled. Accordingly, the apparatus 1 includes a dewar vessel filling assembly 16 configured to fill, in this example, each of the dewar vessels received within the cavities 5. The filling assembly 16 comprises a releasable filling connector configured to releasably couple to a fluid inlet 17 of each dewar vessel 2. In this example, the connector 15 of the ventilation assembly 8 provides for connection to the fluid inlet 17 of each dewar vessel. Thus, the connector 15 may have separate flow paths for gas leaving the dewar vessel 2 and gas entering the dewar vessel 2. In other examples, separate connectors are provided for the ventilation assembly and the filling assembly. The filling assembly 16 further comprises a fill port 18 for receiving a flow of gas from a source external to the apparatus 1 to fill the dewar vessels. The fill port 18 provides a connection to the filling assembly 16 through the outer wall 4 of the box 3. An external filling apparatus may connect to the fill port 17. Accordingly, the fill port may include a connector part complimentary to connector part on the external filling apparatus. A network of conduits, such as a manifold 19, within the box is configured to direct gas from the fill port 17 to the dewar vessels 2 via gas inlet flow paths 20 for each of the cavities that terminate in the connectors 15.

The manifold 19 includes a control valve 21 for controlling the flow of gas into the filling assembly 16 through the fill port 18. The valve 21 may be a solenoid valve or a one-way valve to prevent flow out of the fill port 18.

Further, in this example, the apparatus 1 is configured to circulate gas through the dewar vessels when filling. This technique may be advantageous for ensuring that the temperature of the vessels themselves and the filling assembly is sufficiently cold to allow the vessels to be filled to their capacity. Thus, the filling assembly 16 comprises an inflow section which delivers fluid into each of the dewar vessels 2. The dewar vessels 2, in this example, have a divider 22 which separates the fluid inlet 17 from the fluid outlet 9. The ventilation assembly, connected to the fluid outlet 9, forms an outflow section to receive fluid from the vessels during the filling processes. The fluid flows to vent 14 which, during filling, may be connected to the external filling apparatus which may recirculate the gas into the inflow section.

In other examples, the filling assembly 16 may have dedicated inflow and outflow sections distinct from the ventilation assembly 8.

The dewar vessels may be pre-cooled using a coolant such as liquid nitrogen prior to disposing in each cavity of the apparatus 1.

The external filling apparatus and/or the dewar vessels and/or the apparatus 1 may be provided with suitable authentication mechanisms to prevent tampering and to confirm and authenticate the filling history and ownership of each dewar 2. The authentication system may use RFID or other sensors mounted within the apparatus, such as within each cavity.

The apparatus 1 is configured to be transported easily. For example, the apparatus 1 may be configured to be carried by a user. Accordingly, the dewar vessel storage apparatus 1 may include a carrying structure (not shown), such as a handle(s) or hand sized indents to allow one or more users to carry the dewar vessel storage apparatus 1.

It will be appreciated that the dewar vessel storage apparatus 1 is provided with sufficient insulation or insulation of a particular performance to effectively perform its function providing for storage of dewar vessels during transportation. Thus, from filling to the delivery to the user the insulating performance may be such that at least 90% of the contents of the dewar vessels at filling is available at delivery. It will be appreciated that other performance criteria may be used. For example, the outer walls of the box may have a thermal performance so as to achieve a thermal input from the surroundings of less than 100W (or less than SOW, or less than SOW, or less than 40W) when at cryogenic temperatures.

An example size of the dewar vessel storage apparatus may be 1.2 x 1 x 1m with an insulation thickness (of at least the outer wall) of at least than 50mm. Such a box may contain twelve dewar vessels. The heat loss from the box should be controlled by insulation to allow extended storage time of the cryogenic fluid. If a high vacuum MLI insulation is used it may be possible to reduce the heat gain to a few watts. With the correct configuration, storage times could be achieved of at least 12 hours, 1 day or 1 week or more if an active cryo-cooler is used. The interior of the box 3, inward of the outer walls, may be substantially thermal insulation 23.

Figure 2 shows a second example in which a sacrificial gas storage vessel, such as a sacrificial dewar vessel, is provided to assist in maintaining the other dewar vessels 2 within the box at a low temperature. The same reference numerals have been used for like features except that “100” has been added to them.

The one or more sacrificial gas storage vessels 130 and 131 are allowed to expel their contents in a controlled manner such that the cooling effect due to evaporation of the gas out of the sacrificial gas storage vessels can be used to cool the “normal” dewar vessels 102. The sacrificial dewar vessels 130, 131 may be located adjacent the outer wall 4 or outwards of the other dewar vessels 2. The pressure in the sacrificial dewar vessels may be lower than the others.

The dewar vessel storage apparatus 101 further includes a thermally conductive element 132 that surrounds the sacrificial gas storage vessels 130,131 (or the cavity within which they are located) as well as at least one of other dewar vessels 102. In this example, a single thermally conductive element 132 surrounds all of the cavities 105 and the sacrificial gas storage vessels 130, 131. The thermally conductive element 132 may be of metal, such as aluminium. The thermally conductive element provides for transfer of heat between the dewar vessels 102 and the sacrificial gas storage vessels 130, 131.

In the example of Figure 2, the sacrificial dewar vessels 130, 131 are non-removable and thus fixed within the thermally conductive element 132 and connect to the ventilation assembly 108 and filling assembly 116. However, in other examples, the sacrificial gas storage vessels 130, 131 may be removable. Thus, the apparatus 101 may include “sacrificial” cavities designated to receive the sacrificial dewar vessels 131, 132. The “sacrificial” cavities may be substantially the same as the other cavities. They may differ in that the ventilation assembly 108 may be configured differently to receive the sacrificial gas vented from the sacrificial dewar vessels. Thus, the connector 115 or an element associated with the connector within a sacrificial cavity may provide for release of the gas within the sacrificial gas storage vessel at a particular predetermined rate.

The ventilation assembly 16 may include means to actively control the release of gas from the sacrificial gas storage vessel(s) 130,131, which may be in response to a sensor input, such as a temperature sensor. The apparatus 101 may be configured or the sacrificial 4 dewar vessel may be configured to continuously or intermittently vent its contents over a predetermined time period. The predetermined time period may be selected to exhaust its entire contents over an intended use period. For example, if the dewar storage apparatus is configured to transport the dewars over a 5 hour journey, the predetermined time may be 5 hours or based on the expected journey time or based on a “rating” of the dewar storage apparatus.

While the thermally conductive element 132 for providing heat transfer between the dewar vessels 102 and the sacrificial dewar vessels 130, 132 comprises a block in this example, in other examples, it may comprises one or more heat pipes or a refrigeration or cryogenic cooling system. Thus, the refrigeration/cryogenic cooling system may include a compressor, condenser and a working fluid that is cooled by the sacrificial gas storage vessel(s).

In the example of Figure 2, the sacrificial gas storage vessels are dewar vessels 130, 131 similar to the “normal” dewar vessels 102, as they are adapted to hold the same liquefied or cryo-compressed gas or slush. The vessels 102, 130 are all connected to the filling assembly 116 and are configured to be filled together. As in the example of Figure 1, the gas is circulated through the vessels 102, 130 using the ventilation assembly 108 as an outflow section. Once filled, the external filling apparatus (not shown) may be disconnected from the fill port 118 and vent port 114 and the apparatus 101 may be ready for transport or storage of the dewar vessels 2. In this example, the pressure relief valve of the sacrificial dewar vessels 130,131 is configured at a lower pressure than the “normal” dewar vessels. Alternatively, the pressure relief valves may be set to the same value, but by virtue of locating the sacrificial dewer vessels adjacent an outer wall, they may release their gas quicker than the other dewer vessels. In other examples, the apparatus 101 is configured to control the rate at which the gas is released from the sacrificial dewar vessels 130, 131.

Figures 3 and 4 show third and fourth example of the dewar vessel storage apparatus. The same reference numerals have been used for like features except that “200” has been added to them for Figure 3 and “300” has been added to them for Figure 4.

In these examples a thermally conductive element 232, 332 is provided within the box 203, 303. The thermally conductive element is spaced inwardly of the outer walls 204, 304 such that it is thermally isolated from the exterior of the box. In this example the thermally conductive element comprises a thermal mass of aluminium. A high thermal mass may advantageously control temperature fluctuations. The thermally conductive element 232, 332 includes a heat exchanger 240, 340. The heat exchanger is provided in direct or indirect thermal contact, such as via the thermally conductive element 232, 332, with the dewar vessels 202, 302. The heat exchanger 240, 340 is configured to receive a working fluid, comprising a suitable refrigerant/cryogenic working fluid, which is cooled using a cryo-cooling apparatus 241, 341. In these examples, the cryo-cooling apparatus 241, 341 is external to the box 203, 303, although it may be integrated therein. The cryo-cooling apparatus 241, 341 receives a supply of power for cryo-cooling the refrigerant/cryogenic working fluid for supply to the heat exchanger.

The example of Figure 4 differs from that shown in Figure 3 in that an electrochemical fuel cell 342 is provided to generate, at least in part, the electrical power required by a refrigeration system, such as cryo-cooling apparatus 341. The fuel cell 342 is arranged to use, as its fuel, the hydrogen that is vented from the ventilation assembly 308. In this example, a conduit 343 is provided to direct the hydrogen gas leaving the vent 314 to an anode of the fuel cell 342. A cathode of the fuel cell 342 is configured to consume oxygen from atmospheric air as its oxidant. This arrangement may be advantageous as an increase in the gas leaving the ventilation assembly 308 may be indicative of the temperature in the apparatus 301 rising. As the gas is supplied to the fuel cell 342 it automatically reacts by generating electricity to power the cryo-cooling apparatus to cool the apparatus 301. Thus, a closed loop feedback loop is provided by the ventilation assembly 308, the conduit 343, the fuel cell 342, the cryo-cooling apparatus 341 and the heat exchanger 340. Such an arrangement may be advantageous in combination with a sacrificial dewer vessel, which may provide the gas/hydrogen to power the fuel cell 342.

In other examples, the fuel cell 342 may be configured to use the gas vented from the one or more dewar vessels to generate electricity for a different purpose, such as for sensors to monitor the temperature of the apparatus 1. For example, the heat exchanger 340 and cryo-compressor 341 may not be present. The fuel cell 342 may be used to power a display or a user interface disposed on the dewar vessel storage apparatus or any other load. The fuel cell 342 may power circuitry to determine at least one operating parameter of one or more of the dewar vessels and may store the data which is representative of the at least one operating parameter of the dewar in a memory device located on the dewar or as part of the apparatus for display or recording.

In any of the above examples, the dewar storage apparatus may include a thermal mass element configured to surround one or more of the cavities 5. The thermal mass may be cooled to a temperature, such as during filling of the dewar vessels in situ, that assists in maintaining the dewar vessels 2 at a desired temperature. The thermal mass element may have an isobaric volumetric heat capacity of greater than 2 J.cm’^.K'^

It will be appreciated that the features described in relation to the above embodiments may be provided in any combination. The filling assembly, a particular layout of the ventilation assembly, a particular layout to provide a sacrificial gas storage vessel, the thermal mass element, the heat exchanger, the number and layout of the cavities, the refrigeration/cryogenic cooling system and/or the fuel cell, at least, may be provided in any combination. Further, while we reference a dewar vessel we intend to include other vessels that may be appropriate for cryogenically storing gases.

Figure 5 shows a flow chart illustrating the method of providing a dewar vessel storage apparatus as described above 500; providing a plurality of dewar vessels for receiving the liquefied or cryo-compressed gas/slush 501; transporting the dewar vessel storage apparatus having the plurality of dewar vessels stored therein to the point of use 502; and the dewar vessel storage apparatus providing for individual removal of one of the plurality of dewar vessels at the point of use 503 without disturbing the insulation provided for another of the dewar vessels.

Claims

1. A dewar vessel storage apparatus configured to hold at least two dewar vessels containing liquefied gas or cryo-compressed gas, comprising; a box having an outer, thermally insulating, wall; the box comprising a plurality of insulating cavities, each cavity configured to receive a single dewar vessel and is thermally insulated from each other cavity; each cavity including a separately removable thermally insulating bung configured to close an open end of its cavity; a ventilation assembly comprising at least one conduit within the box configured to provide for venting of gas released from the dewar vessels when stored in the respective cavities of the box, the ventilation assembly configured to provide a gas outlet flow path from each cavity.

2. A dewar vessel storage apparatus according to claim 1, in which the outer, thermally insulating, wall and/or insulation between each cavity comprises at least one of; a vacuum insulated panel utilizing a multilayer insulation blanket in the vacuum gap; a vacuum jacket or panel with no multilayer insulation blanket in the vacuum gap; a wall utilizing spray on foam insulation; and a wall incorporating aerogel insulation.

3. A dewar vessel storage apparatus according to claim 1 or claim 2, in which each cavity and its associated bung is configured complimentary to the shape of the dewar vessel it is configured to receive such that there is substantially no air space when the dewar vessel is received in the cavity and the bung is in place.

4. A dewar vessel storage apparatus according to any preceding claim, in which the outer walls of the box may have a thermal performance so as to achieve a thermal input from the surroundings of less than 100W when containing a cryogenic dewar vessel.

5. A dewar vessel storage apparatus according to any preceding claim, in which the box includes an aperture configured to provide access to the cavities, said aperture closed by a removable thermally insulating lid.

6. A dewar vessel storage apparatus according to any preceding claim, in which the ventilation assembly includes a releasable connector configured to releasably couple the outlet flow path of one of the cavities to a pressure relief valve of a dewar vessel inserted into said one of the cavities for receiving boiled-off gas from the dewar vessel.

7. A dewar vessel storage apparatus according to claim 6, in which the releasable connector is arranged at a base of the cavity such that a connection is made between the dewar vessel and the ventilation assembly when the dewar vessel is substantially completely inserted into said cavity.

8. A dewar vessel storage apparatus according to any preceding claim, in which the ventilation assembly comprises a manifold configured to connect to each cavity and provide a common ventilation flow path, the manifold providing the outlet flow path from each cavity.

9. A dewar vessel storage apparatus according to any preceding claim, in which the ventilation assembly is configured to; connect the gas outlet flow path from at least one of the cavities to atmosphere; and/or connect the gas outlet flow path from at least one of the cavities to burner or catalyser for consuming the vented gas; and/or connect the gas outlet flow path from at least one of the cavities to an electrochemical fuel cell, the fuel cell configured to use gas vented from the one or more dewar vessels to generate electricity; connect the gas outlet flow path from at least one of the cavities to a gas store.

10. A dewar vessel storage apparatus according to any preceding claim, in which the ventilation assembly includes a controllable valve for controlling the receipt of gas into the gas outlet flow path of at least one or more or all of the cavities.

11. A dewar vessel storage apparatus according to any preceding claim, including a refrigeration or cryogenic cooling system configured to cool an interior of the box.

12. A dewar vessel storage apparatus according to claim 11, in which the refrigeration or cryogenic cooling system is powered at least by gas vented from the dewar vessel(s) contained within the cavities.

13. A dewar vessel storage apparatus according to any preceding claim, in which the box is configured to house a sacrificial gas storage vessel configured to continuously or intermittently vent its contents over a predetermined time period and thus lower its temperature, the box configured to provide for connection of the sacrificial gas storage vessel to an outlet to receive the gas released therefrom and a heat transfer element configured to cool an interior of the box and/or the cavities using the lowered temperature of the sacrificial cavity.

14. A dewar vessel storage apparatus according to claim 13, in which the heat transfer element comprises at least one of; one or more a heat pipes; a refrigeration system; a cryogenic cooling system; and a thermal mass comprising a first part that extends around the sacrificial dewar vessel and a second part that extends around at least one of the cavities, the first part thermally connected to the second part to provide heat transfer between the parts.

15. A dewar vessel storage apparatus according to claim 13 or claim 14, in which the sacrificial dewar includes a pressure relief valve to provide for venting of its contents and said pressure relief valve is configured at a lower pressure to any other dewar vessel received by the apparatus.

16. A dewar vessel storage apparatus according to any preceding claim, comprising a dewar vessel filling assembly within the box and configured to fill one or more dewar vessels received within the cavities, the filling assembly comprising a releasable filling connector configured to releasably couple to a dewar vessel inserted into one of the cavities and a fill port for receiving a flow of gas to fill the dewar vessel, the assembly configured to direct gas from the fill port to the dewar vessel connected to the connector.

17. A dewar vessel storage apparatus according to any preceding claim, in which the dewar vessel filling assembly is configured to circulate gas through the dewar vessel(s) when filling the dewar vessel(s) wherein the filling assembly comprises a circulation loop having an inflow section, including the fill port and the filling connector to receive the gas and direct to the or each dewar vessel received within a respective cavity and an outflow section to receive the gas from the or each dewar vessel within a respective cavity for recirculating to the inflow section.

18. A dewar vessel storage apparatus according to any preceding claim in which the ventilation assembly forms at least part of the outflow section when filling the or each dewar vessel.

19. A dewar vessel storage apparatus according to any preceding claim, in which the box includes a carrying structure configured to allow one or more users to carry the dewar vessel storage apparatus.

20. A dewar vessel storage apparatus according to any preceding claim, in which a thermal mass is configured to extend around the at least one of the cavities, the thermal mass comprising a thermally conductive material relative to the insulation of the outer wall and is surrounded by the outer wall.

21. A dewar vessel storage apparatus according to claim 20, in which the thermal mass has a isobaric volumetric heat capacity of greater than 2 J.cm'^.K \

22. A method of providing a liquefied or cryo-compressed gas or slush to a point of use comprising; providing a dewar vessel storage apparatus as defined in any preceding claim; providing a plurality of dewar vessels for receiving the liquefied or cryo-com pressed gas or slush; transporting the dewar vessel storage apparatus having the plurality of dewar vessels stored therein to the point of use; and providing for individual removal of one of the plurality of dewar vessels at the point of use.

23. A method according to claim 22, in which the method includes filling the plurality of dewar vessels while stored within the dewar vessel storage apparatus.

24. A method according to claim 22 or 23, in which the step of filling includes circulating gas through the dewer vessels.

25. A dewar vessel storage apparatus as described herein and as illustrated in any one of the Figures.