CRYOSTORAGE SYSTEM

Description

Field of invention

[0001] The present invention relates to a cryogenic storage system comprising a cryogenic container for storing hydrogen, in particular as a mobile cryogenic storage system for storing hydrogen for powering a motor vehicle. State of the art

[0002] It is known that mobile cryogenic storage systems are used to carry the hydrogen required for propulsion in a motor vehicle.

[0003] To extract gas from the storage tank, the pressure inside it is increased, which is usually done by heating the contents of the tank, either with external energy or by a heat exchanger located in the inner tank of the storage tank, through which already vaporized gas flows.

[0004] Utility models AT 009 291 U1 and AT 010 015 U1 describe extraction devices that partially eliminate the disadvantages associated with the usual device by recirculating gaseous gas from a pump and blowing it into the storage container, either into the gas space or near the bottom into the liquid.

[0005] Alternatively, fluid transport can be carried out by a liquid pump with linear drive and conditioning by means of a downstream heat exchanger, as known from US 2012317995A1.

[0006] However, known solutions have some disadvantages, for example: In known solutions, the operating pressure in the inner tank must be higher than the supply pressure to the consumer. This reduces the usable storage capacity of the inner tank, as the density of the cryogenic liquefied gas decreases with increasing pressure. A higher normal operating pressure in the inner tank reduces the pressure differential until the boil-off valve's response pressure, meaning the pressure build-up time is reduced. Pressure build-up in the inner tank is only possible with a passive system (closed inner tank heat exchanger) if gas is being drawn off by the consumer simultaneously. In practice, this means that after refueling—which takes place at a pressure below the operating pressure—only very small quantities of gas can initially be supplied to the consumer. With an alternative concept, a so-called...In this active system, a powerful blower is used, located outside the system. This blower uses a pipe connection to pump warm hydrogen at a low pressure differential into the inner tank, thereby increasing its pressure level, regardless of any simultaneous withdrawal by the consumer. The blower and the necessary high-voltage electronics require power consumption in the kilowatt range.

[0007] From US patent 2002 / 069857 A1, a method for conveying a cryogenically stored fuel in the liquid state is known, in which the cryogenic fuel is taken from a thermally insulated fuel tank and forced into a fuel line by a conveying device, wherein at least temporarily during the operation of the conveying device the pressure in the fuel tank is increased by an amount that is greater than the difference between a drop in the inlet pressure occurring on the suction side of the conveying device and the difference between the prevailing tank pressure at a pump inlet point and the boiling pressure determined by the current fuel temperature.

[0008] DE 10 2019 205601 A1 discloses a method for operating a fuel system that supplies a combustion engine of a motor vehicle with natural gas, wherein the natural gas is essentially stored in liquid form in a tank on board the motor vehicle and is extracted from the tank by means of a pre-supply pump located in the tank and supplied via a feed line to a high-pressure pump for pressurization, wherein the pre-supply pump draws in natural gas from a liquid phase as well as natural gas from a gas phase also present in the tank and the gas component contained in the liquid natural gas in the form of gas bubbles is at least partially condensed on the pressure side of the pre-supply pump under pre-supply pressure.

[0009] From US Patent 7,356,996 B2, a device for receiving and extracting a cryogenic fluid is known, wherein the device comprises: (a) a double-walled vacuum-insulated container defining a cryogenic chamber for receiving the cryogenic fluid; (b) a pump assembly comprising a pump with a suction inlet located within the cryogenic chamber and at least one elongated element extending from the pump to a drive unit located outside the cryogenic chamber, wherein the elongated element comprises an elongated non-metallic section having a thermal conductivity lower than that of a structurally equivalent elongated stainless steel element of the same length; and (c) a conduit with one end located within the cryogenic chamber and connected to an outlet of the pump assembly, and another end located outside the cryogenic chamber. Summary of the invention

[0010] It is an object of the invention to provide a cryogenic storage system of the type mentioned which can reduce at least some of the problems mentioned and in particular to provide a cryogenic storage system comprising a cryogenic container for storing hydrogen which enables a cost-effective operation in an inner tank and reliable extraction of the medium from the inner tank.

[0011] The problem is solved by a cryogenic storage system with the features according to claim 1.

[0012] The cryogenic storage system comprises a cryogenic container for storing hydrogen, with an inner tank and an outer container, wherein at least one cryopump is arranged in the inner tank of the cryogenic container, wherein the cryopump is completely surrounded by cryogenic fluid during normal operation and / or wherein the drive of the cryopump is configured to operate at cryogenic temperatures, wherein the cryopump delivers liquid and gaseous hydrogen in one or more stages to a consumer at a higher pressure than the pressure in the inner tank.

[0013] According to the invention, the cryopump is designed as a linear pump that delivers on both sides, with a left and a right delivery flow.

[0014] According to the invention, the left and / or right flow of the linear pump is designed to selectively pump gas or liquid.

[0015] According to the invention, a cryogenic storage system in the inner tank of a cryogenic container has at least one cryopump. The cryopump allows liquid and gaseous hydrogen to be extracted from the inner tank at extremely low temperatures and – preferably via a heat exchanger that warms the hydrogen – conveyed to a consumer. The conveyance to the consumer can take place at a pressure higher than the pressure in the inner tank of the cryogenic storage system.

[0016] The cryopump is located in the inner tank of the cryogenic storage container, i.e., in a cryogenically cold area of ​​the cryogenic storage system during normal operation. Therefore, the cryopump is completely surrounded by cryogenic fluid during normal operation. The cryopump's drive is designed to operate at extremely low temperatures.

[0017] The following advantages can be achieved by using a cryopump in the inner tank: The operating pressure in the inner tank can be minimized and may be lower than the lowest possible supply pressure to the consumer. A lower operating pressure in the inner tank allows for longer pressure build-up times or lower design pressures, and thus thinner walls, meaning lighter inner tanks or more complex storage tank geometries become feasible. Backgas losses during liquefied gas refueling can be reduced by the lower inner tank pressure. The improved thermodynamic conditions in the inner tank enable higher refueling speeds. Changes in delivery head (pressure) or flow rate are accelerated or facilitated. The energy consumption for operating the cryogenic pump, which is entirely exposed to the cryogenic fluid temperature, is significantly lower than for an active system with a blower or with pumps or compressors whose drive and / or compression work takes place at approximately ambient temperature.With a suitable configuration, either liquid or gas can be pumped. This allows for precise coordination between the pumped mass flow rate and the pressure reduction achieved through volumetric work.

[0018] The cryopump preferentially feeds the extremely cold hydrogen to a heat exchanger, which heats the hydrogen and then directs it from the heat exchanger to the consumer.

[0019] Preferably, the cryopump is located near the bottom of the inner tank and is surrounded by liquid hydrogen during normal operation.

[0020] Preferably, at least one intake port of the cryogenic pump is equipped with a gas extraction line, the open end of which is located near the ceiling of the inner tank and / or contains gaseous hydrogen at the open end of the gas extraction line during normal operation, so that gaseous hydrogen can be extracted from the inner tank by the cryogenic pump via the gas extraction line. The gas extraction line is thus configured to allow gaseous hydrogen to be extracted from the inner tank via the gas extraction line. The gas extraction line can be designed as an extension of the intake port.

[0021] A further extraction line or extraction opening for the extraction of liquid may be provided at the same or a different intake port of the cryopump.

[0022] According to the invention, at least one intake port of the cryopump can selectively pump either gaseous or liquid hydrogen. Preferably, a shut-off valve for switching between gaseous and liquid hydrogen is provided at the intake port of the cryopump. The shut-off valve is preferably located near the cryopump and / or the intake port of the cryopump.

[0023] Particularly preferably, the left and / or right delivery flow of the linear pump is designed to selectively convey either gas or liquid, via a shut-off valve near the pump for switching between gaseous and liquid hydrogen, i.e. from LH2 to GH2.

[0024] Preferably, the cryogenic container is configured so that a partial flow of the heated hydrogen, i.e., the hydrogen extracted after the heat exchanger, can be returned to the inner tank via a gas return line in order to increase the inner tank pressure and preferably maintain it at a minimum pressure. Preferably, a shut-off valve for gas return to the inner tank is arranged in the gas return line.

[0025] Preferably, a pressure reducer, preferably with a downstream pressure relief valve, is installed in the gas return line for gas return to the inner tank. This allows the pressure for gas return to the inner tank to be limited.

[0026] Preferably, a buffer tank for warm hydrogen is arranged between the cryopump and the consumer. This allows any fluctuations in the cryopump's delivery rate to be compensated for.

[0027] Preferably, a spring-loaded check valve or a changeover valve is arranged in a pressure line of the cryopump that discharges the pumped medium, so that the pressure line that discharges the pumped medium transitions at the spring-loaded check valve or changeover valve into an inlet line into the inner tank.

[0028] The inner tank can be refueled via a refueling interface, preferably refueling taking place at least section by section via a withdrawal line, and particularly preferably refueling taking place via the spring-loaded check valve or the changeover valve and the inlet line into the inner tank.

[0029] Preferably, the changeover valve has an integrated float, the weight of which holds the float in a lower end position during refueling, thus opening the inlet line for filling the inner tank. When the cryogenic pump is started, the float is lifted by the flow, closing the inlet line to the inner tank and directing the flow exclusively to the consumer. Brief description of the drawings

[0030] The invention is described below by way of example with reference to the drawings. Fig. 1 is a schematic representation of a cryogenic storage system not according to the invention. Fig. 2 is a schematic representation of a part of the cryogenic storage system not according to the invention. Fig. 1 in another embodiment. Fig. 3 is a schematic representation of a part of the non-inventional cryogenic storage system according to Fig. 1in another embodiment. Fig. 4 is a schematic representation of a cryogenic storage system according to the invention in one embodiment. Fig. 5 is a schematic representation of a cryogenic storage system according to the invention in another embodiment. Fig. 6 is a schematic representation of a cryogenic storage system not according to the invention in another embodiment. Fig. 7 is a schematic detail view of a changeover valve of a system according to the invention. Fig. 6 in a first state. Fig. 8 is a schematic detail view of a changeover valve of a cryogenic storage system according to Fig. 6 in a second state. Detailed description of the invention

[0031] In Fig. 1 Figure 1 shows a cryogenic storage system comprising a cryogenic container which includes an inner tank 1 and an outer tank 2, with an isolation space as an intermediate space between the inner tank 1 and the outer tank 2.

[0032] The cryogenic storage system can pump cryogenic liquid from the inner tank 1 to a consumer 5 by means of a power-controlled pressure-boosting cryopump 21 via a pressure line 22 of the cryopump, which transitions into a withdrawal line 27 and leads to a supply line 4 at a line connection 3.

[0033] The cryogenic pump 21 is completely surrounded by cryogenic fluid, meaning that the pump 21's drive also operates at extremely low temperatures, thus enabling low electrical power consumption for cold gas compression. The cryogenic pump 21 is located near the bottom of the inner tank 1 and is completely surrounded by liquid hydrogen. Gas can also flow from the inner tank 1 into the extraction line 27 by opening a GH2 tank valve 15 and / or liquid by opening an LH2 tank valve 16. Gas can be extracted from the inner tank 1 via a combined safety and gas extraction line 18. A check valve 17 for gas extraction can be provided downstream of the GH2 tank valve 15. Gas can also be released to the outside from the combined safety and gas extraction line 18 via a pressure relief safety valve 19.

[0034] After being drawn from the inner tank 1, particularly after the cryogenic pump 21 and the tank valves 15, 16, the cryogenic fluid is passed through a heat exchanger 7. During this process, it is completely converted into the gas phase by the addition of heat, preferably via cooling water 11 from the consumer 5, and simultaneously heated sufficiently for the consumer 5. The cryogenic pump 21 delivers the hydrogen to the consumer 5 at a higher pressure than that present in the inner tank 1, if required. When fuel is drawn from the cryogenic storage system, the pressure and the amount of fuel in its inner tank 1 decrease.

[0035] To compensate for any fluctuating delivery rate of the cryopump 21, a buffer tank 8 for warm hydrogen can be additionally arranged between pump 21 and consumer 5, particularly in the supply line 4. A shut-off valve 12 for the H2 supply to consumer 5 can be arranged in the supply line 4 upstream of consumer 5.

[0036] The cryogenic storage system can be refueled via a refueling interface 14. Refueling can be carried out in sections via the extraction line 27 and an LH2 inlet line 20 into the inner tank 1.

[0037] A spring-loaded check valve 25 can be installed in the pressure line 22 of the cryopump 21, which discharges the pumped medium ( Fig. 1-5 ) or a changeover valve 26 ( Figs. 6-8 The system is arranged such that the pressure line 22, which discharges the conveyed medium, transitions into an inlet line 20 into the inner tank 1 at the spring-loaded check valve 25 or the changeover valve 26. Refueling can then take place via the extraction line 27 and the spring-loaded check valve 25 or the changeover valve 26 and the inlet line 20 into the inner tank 1.

[0038] If it is necessary to increase or maintain the pressure in the inner tank 1 of the cryogenic storage system, gas can be transferred back into the inner tank 1 via valve 13 in a gas return line 6, which branches off from the extraction line 27 after the heat exchanger 7 at the line connection 3. To limit the pressure for the gas return to the inner tank 1, a pressure reducer 9 with a downstream pressure relief valve 10 can be installed in the gas return line 6 if required. Fig. 1 A single-stage pressure increase with gas recirculation shows, shows the Fig. 2 a variant with a serial pump arrangement for a two-stage pressure increase with gas recirculation.

[0039] If there is a need for very high supply pressures (supercritical, for example more than 20 bar), at least one further cryopump stage can be connected in series after the first cryopump stage (see below). Fig. 2The final pressure of the first cryopump 21 becomes the intake pressure of the second cryopump 21. This series connection allows for higher final pressures while simultaneously reducing energy consumption for compressing the cold gas. Alternatively, a warm compressor for final compression can be installed outside the tank system following the cryopump 21 and the heat exchanger 7.

[0040] Fig. 3 Instead of the standard feed pump, a special version of the pump is shown in the form of a linearly driven, double-sided displacement cryopump 21, with two opposing displacement working chambers, each with separate suction and discharge ports for bidirectional fluid transfer. The cryopump 21 is thus designed as a linear pump that transfers the stored medium from both sides. Fig. 3 only in the form of the liquid medium.

[0041] Fig. 4shows a variant of a linearly driven double-sided displacement cryopump 21 with separate suction ports (as Fig. 3 ), whereby one-sided (in Fig. 4 A switching valve 23 is provided on the left side of the linear pump for selectively pumping either liquid or gas. A gas extraction line 24 is formed at this intake port of the cryogenic pump 21, the open end of which is located near the ceiling of the inner tank 1. Under normal operating conditions, gaseous hydrogen is present at the open end of the gas extraction line 24, allowing the cryogenic pump 21 to extract gaseous hydrogen from the inner tank 1 via the gas extraction line 24. Only liquid is pumped on the opposite side of the pump. Otherwise, the cryogenic storage system is designed identically to the variants of the Figs. 1 to 3 .

[0042] Also, configurations of a cryogenic storage system with a cryopump 21 that is not designed as a linear pump, such as in Fig. 1-3 The illustrated components may include such a gas extraction line 24 and / or such a switching valve 23 for the selective conveyance of liquid or gas.

[0043] By installing additional equipment in the inner tank (cryogenic valve(s), piping(s)), either gas or liquid can be selectively supplied to the respective intake port by means of controlled, alternating valve switching positions. This is achieved, for example, through valve control 23 in Fig. 4The ratio of gas to liquid withdrawal is variable, and thus also the ratio of mass flow to consumer 5 to pressure reduction in the inner tank 1. The option to choose between gas or liquid withdrawal offers an additional degree of freedom, because the ratio of mass flow to consumer 5 to pressure reduction in the inner tank 1 is no longer approximately constant and the respective value can no longer be changed solely via the pump frequency, but is flexible in each case.

[0044] With valve 23 open, LH2 floods the pipe up to the intake port of the cryopump 21 and up the gas extraction line 24 to the level of the LH2 (as a result of hydrostatic equalization). When valve 23 is closed, the remaining LH2 is first pumped out of the intake port pipe before gaseous hydrogen flows from above through the gas extraction line 24 to the intake port.

[0045] Gas can thus be drawn from the inner tank 1 via a gas extraction line 24, which serves as an extended suction port for the cryogenic pump 21. A switching valve 23 located near the pump allows switching between LH2 and GH2, enabling the pump 21 to selectively deliver either liquid or gas from the inner tank 1.

[0046] Is a linear pump ( Fig. 3 - 6 Using a system that pumps from both sides, various extraction options are possible: For example, the left and right flow streams can both pump only LH2, i.e., liquid hydrogen; or one of the two sides, for example the left, can pump either GH2 or LH2 and the other side only LH2; or both sides can pump either GH2 or LH2, i.e., gas or liquid, so that the pumped medium can vary from 100% GH2 to 100% LH2.

[0047] Fig. 4One of these possibilities shows a variant with a linearly driven double-sided displacement cryopump 21 with connected suction nozzles, with optional pumping of liquid or gas on one, namely here the left, side of the pump.

[0048] Fig. 5 shows a variant of a linearly driven double-sided displacement cryopump 21 with separate suction ports, both of which are optionally configured for pumping liquid and / or gas.

[0049] Each of the two intake ports of the cryopump 21 has a switching valve 23 for switching from LH2 to GH2.

[0050] In the arrangements described so far, a spring-loaded check valve 25 in the filling line of the inner tank allows refueling bypassing the pump 21 and preferably into the gas space. It is required that the refueling pressure for opening the spring-loaded check valve 25 is higher than the maximum delivery pressure of the cryogenic pump 21. While the check valve 25 does create additional flow resistance during refueling, it prevents a restriction in the flow from the cryogenic pump 21 to the consumer 5.

[0051] Fig. 6 shows a different configuration of the valves for refueling, namely a changeover valve 26 in the inner tank 1 - here with a float position when withdrawn by the cryopump 21 - instead of the spring-loaded check valve 25.

[0052] The changeover valve 26 with integrated float 28 (see Figs. 6-8This represents an alternative embodiment for this function, the switching between withdrawal and refueling. The changeover valve 26 is located at the connection point between pressure line 22, withdrawal line 27 and inlet line 20 in the inner tank 1.

[0053] The floating body 28 remains in place during refueling due to its own weight ( Fig. 7 ) in the lower end position and opens the inlet line 20 for filling the inner tank. By activating the cryogenic pump 21, the float 28 is lifted / moved by the flow in such a way that it closes the inlet of the filling line to the inner tank 1, i.e., the inlet line 20 ( Fig. 8 ), so that the flow is pumped exclusively to consumer 5.

[0054] The advantages of this alternative are that refueling can be carried out with lower flow resistance and that the refueling pressure and the maximum delivery pressure of the cryogenic pump 21 are independent of each other. However, the float 28 integrated in the changeover valve 26 results in additional flow resistance for the delivery flow of the cryogenic pump 21 to the consumer 5.

[0055] Both configurations of this device allow pressure relief of the adjacent lines and the cryopump 21 into the inner tank 1 when enclosed fluid expands due to heating.

[0056] Fig. 7 This shows the flow in the changeover valve 26 during refueling. The weight of the float 28 holds it in a lower end position during refueling, so that the inlet line 20 is open for filling the inner tank 1.

[0057] Fig. 8The figure shows the flow in the changeover valve 26 when water is drawn via the cryopump 21. When the cryopump 21 is started up, the float 28 is lifted from the valve seat 29 by the flow, so that it closes the inlet line 20 to the inner tank 1 and the flow is pumped exclusively to the consumer 5. Reference symbol list

[0058] 1 Inner tank of the primary storage system 2 Outer tank 3 Piping connection 4 Supply line 5 Consumer 6 Gas return line 7 Heat exchanger 8 Buffer tank 9 Pressure reducer 10 Pressure relief valve 11 Cooling water circuit 12 Shut-off valve for H2 supply to the consumer 13 Shut-off valve for gas return to the inner tank 14 Refueling interface 15 GH2 tank valve 16 LH2 tank valve 17 Check valve for gas withdrawal 18 Combined safety and gas withdrawal line 19 Pressure relief safety valve 20 LH2 inlet line to the inner tank 21 Cryopump(s) 22 Pressure line of the cryopump 23 Switching valve near the pump for switching from LH2 to GH2 24 Gas withdrawal line as extended intake port of the cryopump 25 Additional check valve 26 Changeover valve 27 Withdrawal line 28 Floating body 29 Valve seat

Claims

1. Cryostorage system, comprising a cryocontainer for storing hydrogen, having an inner tank (1) and an outer container (2), wherein at least one cryopump (21) is arranged in the inner tank (1) of the cryocontainer, the cryopump (21) being fully surrounded by cryogenic fluid during normal operation and / or the drive of the cryopump (21) being adapted to work at very low temperatures, the cryopump (21) delivering liquid and gaseous hydrogen in one or more stages to a consumer (5) at a pressure higher than the pressure in the inner tank (1), characterized in that the cryopump (21) is configured as a linear pump which delivers on both sides, with a left and a right delivery flow, wherein the left and / or right delivery flow of the linear pump is configured selectively to deliver gaseous or liquid hydrogen.

2. Cryostorage system according to Claim 1, characterized in that a gas extraction line (24) is configured to be at least at one intake port of the cryopump (21), the open end of which gas extraction line is configured to be in the vicinity of the top of the inner tank (1), and / or gaseous hydrogen being situated at the open end of the gas extraction line (24) during normal operation, so that, via the gas extraction line (24), gaseous hydrogen can be extracted from the inner tank (1) by the cryopump (21).

3. Cryostorage system according to Claim 1 or 2, characterized in that gaseous or liquid hydrogen may selectively be delivered at least at one intake port of the cryopump (21), preferentially via a check valve (23) for switching between gaseous and liquid hydrogen.

4. Cryostorage system according to at least one of the preceding claims, characterized in that the left and / or right delivery flow of the linear pump is configured selectively to deliver gaseous or liquid hydrogen, via in each case a check valve (23) near to the pump for switching between gaseous and liquid hydrogen.

5. Cryostorage system according to at least one of the preceding claims, characterized in that the cryocontainer is adapted so that a partial flow of the warmed hydrogen, i.e. the extracted hydrogen downstream of a heat exchanger (7), can be returned via a gas return line (6) into the inner tank (1) in order to increase the inner tank pressure, preferentially via a check valve (13) for the gas return to the inner tank (1).

6. Cryostorage system according to Claim 5, characterized in that a pressure reducer (9), preferentially with a downstream pressure safety valve (10), is installed in the gas return line (6) for the gas return to the inner tank (1).

7. Cryostorage system according to at least one of the preceding claims, characterized in that a buffer container (8) for warm hydrogen is arranged between the cryopump (21) and the consumer (5).

8. Cryostorage system according to at least one of the preceding claims, characterized in that a spring-loaded nonreturn valve (25) or a shuttle valve (26) is arranged in a pressure line (22) of the cryopump (21), which takes off the delivered medium, so that the pressure line (22) which takes off the delivered medium joins at the spring-loaded nonreturn valve (25) or at the shuttle valve (26) with an inlet line (20) into the inner tank (1).

9. Cryostorage system according to Claim 8, characterized in that the inner tank (1) is capable of being filled via a filling interface (14), the filling taking place at least in part via an extraction line (27), preferentially the filling taking place via the spring-loaded nonreturn valve (25) or the shuttle valve (26) and the inlet line (20) into the inner tank (1).

10. Cryostorage system according to Claim 8 or 9, characterized in that the shuttle valve (26) has an integrated float (28), the inherent weight of the float (28) keeping the float (28) in a lower end position so that the inlet line (20) for filling the inner tank (1) is uncovered, the float (28) being raised by the delivery flow when the cryopump (21) is started so that it blocks the inlet line (20) to the inner tank (1) and the delivery flow is pumped only to the consumer (5).