Storage system for a pressurized gaseous fuel

Abstract

The invention relates to a storage system (1) for a pressurized gaseous fuel, comprising at least two pressurized gas containers (2), which are coupled to one another and to filling and withdrawal connections via a line system (6), and at least one temperature-control device (15), wherein the temperature-control device (15) is arranged in the line system (6). The storage system according to the invention is characterized in that the temperature-control device (15) is arranged in a connecting line (13) between at least two of the pressurized gas containers (2).

Description

[0001] Storage system for a pressurized gaseous fuel

[0002] The invention relates to a pressure storage system for a pressurized gaseous fuel of the type defined in more detail in the preamble of claim 1. The invention also relates to a vehicle with such a pressure storage system.

[0003] Pressure storage systems for pressurized gaseous fuels are well-established in the art. They can be used in both stationary and mobile applications. Particularly in mobile applications, the storage of hydrogen in compressed, i.e., pressurized, form plays a crucial role in order to then convert it into propulsion power in an internal combustion engine or, especially, in a fuel cell system.

[0004] Such storage systems typically have several pressurized gas containers connected to each other via a piping system. They also typically include a tank nozzle and a pressure regulating unit, which, for example, in the application described above, reduces the high-pressure stored hydrogen to a pressure level suitable for a consumer in one or more steps. The pressurized gas storage units themselves are usually designed in different sizes and shapes to make optimal use of the available installation space. The individual or interconnected pressurized gas storage units have a tank valve, which is generally electrically controlled and equipped with a temperature sensor. Such a tank valve, as defined in the present invention, includes at least the functionality of filling the pressurized gas container as well as withdrawing fuel from the pressurized gas container.Typically, this system incorporates a non-return valve for refueling and a fuel withdrawal mechanism via an electromagnetically operated withdrawal valve. Generally, pressure and / or temperature sensors are integrated into various components of the storage system to control it. The control itself is then managed by a control unit for the tank valves, which occasionally also directly integrates the pressure regulating unit. In older designs, these two functionalities are sometimes located in separate valves, for example, at opposite ends of the compressed gas cylinder. In a system with multiple tank valves, the opening and closing of each valve can occur independently.

[0005] In practice, when filling a storage system, for example with hydrogen, the compression of the hydrogen to the currently typical pressure of 70 to 110 MPa heats up considerably. The refueling process is generally controlled by the tank system to ensure that the pressurized gas cylinders remain below critical temperatures, which, according to current technical regulations and standards, are around 85°C. This applies essentially the same way to other compressed gaseous fuels, such as natural gas.

[0006] When fuel is drawn from the storage system during operation, the pressure is regulated from the high-pressure side to a medium-pressure side via the pressure control unit. The pressure in the connected pressure vessels drops, and the mass flow rates adjust according to the volume ratios of these vessels. Due to thermodynamic effects, the emptying of the pressure vessels always results in a more or less significant cooling of the hydrogen inside the storage system.

[0007] If fuel is extracted at low ambient temperatures and / or, in particular, at high mass flow rates, the fuel temperature can drop so low after a relatively short operating time that the critical lower operating temperature of individual components of the storage system is reached. Falling below critical lower temperature limits, which, according to current technology, are usually on the order of -40°C as the lowest possible operating temperature, can, in the worst case, damage the affected components. This ultimately leads to the risk of fuel escaping into the environment. When mixed with atmospheric oxygen, this emission can, in the worst case, create an explosive mixture.

[0008] To avoid this risk, such a storage system is monitored by the sensors mentioned above, especially temperature sensors. To prevent critical lower operating temperatures from being reached, mass flow rates are reduced if necessary, which typically results in a restriction for the connected loads.

[0009] While the problem of cooling can generally be countered by integrating a heater into the interior of the pressurized gas cylinders, as described in EP 2 754 946 B1, this is comparatively complex because the openings of the pressurized gas cylinders must be as small as possible for technical reasons. The heater then has to be inserted through this small diameter for installation, which is correspondingly complex and expensive. Such solutions also have the disadvantage of being subject to very high mechanical stresses, as they must protrude very far into the interior of the respective pressurized gas cylinder to be effective. Nevertheless, this results in poor heat distribution and transfer. Furthermore, they reduce the available storage volume, which is also undesirable.

[0010] In principle, heat can also be supplied by external heating of the pipes and / or the pressurized gas containers. Such a method is described in DE 10 2020 128478 A1, where a gas or gas mixture, such as air, serves as the heat transfer medium, which is preferably conveyed openly over the relevant elements to avoid the need for a complex recirculation system.

[0011] However, this has the disadvantage that the relevant elements must be arranged in such a way that they can be easily surrounded by the gas or gas mixture. This necessitates corresponding limitations in installation space and the arrangement of all components in the same area, as otherwise additional conveying equipment would be required, which in turn consumes energy. This makes the flexibility of distributing the individual pressurized gas cylinders of such a storage system, for example, across the available installation space in different areas of a truck chassis, practically impossible. Furthermore, the heat transfer coefficient, and thus the heat flux density, is comparatively low when gases are flowing around them compared to liquids.

[0012] The object of the present invention is to provide an improved storage system for storing a pressurized gaseous fuel with several pressure gas containers, which avoids the aforementioned disadvantages and enables continuous operation without temperature-related throttling, particularly during fuel withdrawal, by means of a temperature control device.

[0013] According to the invention, this problem is solved by a storage system with the features of claim 1, and in particular in the characterizing part of claim 1. Advantageous embodiments and further developments are described in the dependent claims. Furthermore, a vehicle according to claim 13 solves the problem. Advantageous embodiments and further developments of this vehicle are also described in the dependent claims.

[0014] The storage system according to the invention for a pressurized gaseous fuel, such as hydrogen, provides at least two individual pressurized gas containers which are interconnected via a piping system with filling and emptying connections. Similar to the prior art designs, this storage system includes at least one temperature control device.

[0015] Unlike prior art designs, a temperature control device is not integrated into each of the pressurized gas containers, but rather arranged in the piping system. According to the invention, it is located in a connecting line between at least two of the pressurized gas containers. The temperature control device thus allows the gaseous fuel to be tempered on its way from one pressurized gas container to another. This primarily concerns heating during withdrawal, but in principle, cooling during refueling is also conceivable.

[0016] According to a particularly advantageous embodiment of the storage system according to the invention, the connecting line between a primary tank valve of at least one compressed gas container and a secondary tank valve or a secondary-side tank connection can be configured as follows: A tank valve within the meaning of the invention, as already explained above, is a valve assembly that has both a filling and a withdrawal function within the compressed gas container. A tank connection within the meaning of the present invention is equipped without these functionalities and can, for example, be configured as a modified so-called end plug, which is connected to the interior of the compressed gas container via a bore to which a high-pressure line can be connected.The primary tank valve is the type of tank valve commonly used in the art, serving for the general withdrawal of fuel and the filling of individual pressurized gas cylinders. A possible secondary tank valve, as an alternative to the standard tank connection, would be located on the opposite side of the pressurized gas cylinder and could therefore be used for reintroducing fuel after it has passed through the temperature control device.

[0017] In the case of a simple tank connection, a check valve would be necessary, depending on the application. This can be integrated into the piping system if required. However, according to a further, very advantageous embodiment of the storage system according to the invention, the tank connection can also be provided with a check valve as its sole functional element.

[0018] According to a further exceptionally advantageous embodiment of the storage system according to the invention, it can now also be provided that the secondary-side tank valve or the tank connection is exclusively connected to the connecting line or a distributor connected to the connecting line. "Connected" or "in contact" within the meaning of the invention always refers to the connection between two components via corresponding lines, so that a connection that may exist in practice, albeit fluidically, via several intermediate components and pressurized gas containers or the like, is not considered a connection within the meaning of the invention. The connecting line with the temperature control device is therefore arranged exclusively on the secondary side of the individual pressurized gas containers.The functionality of the temperature control, and this applies in particular to the heating at high withdrawal rates from the storage system, is therefore only implemented on the secondary side, so that the gaseous fuel heated by the temperature control device flows into the pressure gas containers and heats them uniformly by mixing the gases.

[0019] A particularly advantageous embodiment of the storage system according to the invention can also provide that the tank connection with the integrated check valve or the check valve provided in the piping system in its area is connected to that area of ​​the piping system which has the filling and withdrawal connections for the gaseous fuel.

[0020] In this configuration, the tank connection of at least one pressurized gas cylinder is connected via the check valve to the area containing the filling and emptying connections. During filling, fuel thus enters the corresponding pressurized gas cylinder via the tank connection, which is then connected via the connecting line on the side of its tank valve.

[0021] The temperature control device according to the invention preferably comprises a section of the piping system which is surrounded externally by a heat generator. The setup would thus be implemented, for example, in the manner of an instantaneous water heater. The temperature control device can then be used exclusively for its primary purpose: heating the gaseous fuel during dispensing. According to a particularly advantageous embodiment, the heat generator itself can be electrically operated, for example, as a resistance heater or an eddy current heater. Additionally or alternatively, the heat generator can also be designed as a burner, which provides the heat via flame combustion, catalytic combustion, or a similar process.

[0022] Another alternative, which can be used for both heating and cooling the fuel, can, according to a highly advantageous further development, also provide for the temperature control device to be designed as a heat exchanger, one side of which is traversed by the gaseous fuel and the other side by a heat transfer medium. Heat can be transferred to or extracted from the gaseous fuel via this heat transfer medium. The heat transfer medium can be, for example, a gas or a liquid. According to the second prior art mentioned above, it can, for instance, be conveyed through the heat exchanger as a gaseous medium without a closed loop.

[0023] However, according to a particularly advantageous embodiment of the storage system according to the invention, it can also be provided that the heat transfer medium is part of a cooling circuit that is already present in the higher-level system containing the storage medium. For example, in a vehicle application for storing hydrogen for a fuel cell system, this could be the cooling circuit of the fuel cell system, whose waste heat can thus be used to preheat the gaseous fuel when high volume flows are extracted.

[0024] Another very advantageous embodiment can further provide for at least two temperature control devices in order to be able to heat all necessary areas connected via the connecting line in a targeted manner, even with a more complex distribution of the pressurized gas containers in the system.

[0025] Furthermore, according to a favorable embodiment of the storage system according to the invention, at least one of the tank valves, and in particular the secondary tank valve, may have separate filling and emptying paths. The secondary tank valve can thus be designed in a correspondingly simpler manner, without having to exhibit the complex structure of the primary tank valve, which is typically designed as a so-called OTV (On Tank Valve).

[0026] As mentioned above, the storage system can preferably be used in a vehicle, and in particular for storing compressed hydrogen in a vehicle equipped with a hydrogen engine or, even more preferably, with a fuel cell system. The vehicle can be a truck, especially since, particularly for such heavy vehicles intended for electrical power, a fuel cell system with corresponding compressed hydrogen storage systems offers clear advantages in terms of vehicle weight compared to battery-powered vehicles, while maintaining the same achievable range. Of course, an application with other compressed gaseous fuels, such as natural gas, would also be conceivable. For all conceivable gaseous fuels, both vehicle and stationary applications are possible.The term "vehicle" must be understood very broadly and can include free or rail-bound land vehicles, watercraft, aircraft or spacecraft of any kind.

[0027] Further highly advantageous embodiments of the storage system according to the invention also result from the exemplary embodiment, which is described in more detail below with reference to the figures.

[0028] This shows:

[0029] Fig. 1 shows a storage system for pressurized gaseous fuel according to the prior art;

[0030] Fig. 2 shows a first possible embodiment of a storage system according to the invention;

[0031] Fig. 3 shows a second possible embodiment of a storage system according to the invention;

[0032] Fig. 4 shows a third possible embodiment of a storage system according to the invention;

[0033] Fig. 5 shows a fourth possible embodiment of a storage system according to the invention;

[0034] Fig. 6 shows a fifth possible embodiment of a storage system according to the invention;

[0035] Fig. 7 shows a sixth possible embodiment of a storage system according to the invention; and

[0036] Fig. 8 shows a schematically indicated vehicle with such a storage system.

[0037] Figure 1 shows a storage system 1 in an embodiment according to the prior art. The storage system 1 serves to store pressurized fuel, for example, compressed hydrogen or compressed natural gas. For compressed hydrogen, the pressures currently used are typically between 70 and 110 MPa. The storage system 1 in Figure 1 comprises various pressurized gas containers 2, of which the three containers shown above are of a smaller design and the containers shown below are of a larger design.

[0038] Each of these compressed gas containers 2 includes a tank valve 3 on its primary side, shown here on the left. This tank valve 3 is specifically designed as an on-tank valve (OTV). It typically includes a refueling function with a check valve, a controllable withdrawal valve, and corresponding sensors, such as a temperature sensor projecting into the interior of the respective compressed gas container 2. Such valves are generally known from the prior art, so it is clear to those skilled in the art what type of valve to use here. On the rear side, i.e., the secondary side of the respective compressed gas container, so-called end plugs 4 are arranged, which tightly seal the opening created there during production in the respective compressed gas container.

[0039] A control line, shown as a dotted line, is shown for controlling the individual tank valves 3 and is connected to a control unit 5. The control line can be used both to control the tank valves 3 and to transmit data, for example from the pressure and / or temperature sensors, to the control unit 5.

[0040] The individual compressed gas containers 2 are interconnected via a piping system 6. In this case, this piping system 6 is a high-pressure piping system corresponding to the nominal pressure level of the connected compressed gas containers 2. The individual lines are combined in a distributor 7, often also referred to as a rail or common rail, so that the corresponding high-pressure lines of the power system 6 are connected to the respective tank valves 3 from this distributor 7. A tank nozzle 8, used for refueling the storage system 1, is also connected to this distributor 7 via a high-pressure line.

[0041] Storage system 1 essentially serves to supply a consumer, designated 10, with gaseous fuel at a pressure level suitable for that consumer. This pressure level is typically referred to as the low-pressure level or medium-pressure level. To reach this pressure level from the high-pressure level of the piping system 6 with its distributor 7, a pressure regulator or pressure reducer, designated 9, is provided between these two components. For the sake of clarity, the line between the pressure regulator 9 and the consumer 10 is shown as thinner than the line between the pressure gas reservoir 2 and the pressure regulator 9.

[0042] Figure 2 illustrates this setup again, but it is further developed according to the invention. In the embodiment shown here, the fuel is heated only for the two large pressurized gas containers 2 shown below, since this functionality can be omitted for smaller pressurized gas containers 2. To enable the heating of the fuel when high mass flow rates are drawn, the design of the piping system 6 is modified such that the distributor 7 is connected to the tank nozzle 8 and, via the pressure regulating unit 9, to the consumer 10, analogous to the prior art design. It is also connected to the two large pressurized gas containers 2.The three small pressurized gas containers 2 are connected to the distributor 7 via their own distributor 11 and a check valve 12, whereby the check valve allows flow only in the direction from the first distributor 7 to the second distributor 11. The second distributor 11 and the smaller pressurized gas containers 2 connected to it are then connected to a third distributor 14 via a connecting line 13. A temperature control device 15 is arranged in this connecting line 13, which can be designed, for example, as a chemically or electrically heated flow heater or as a heat exchanger. The gaseous fuel flowing to the third distributor 14 is thus heated. From the distributor 14, it passes through two tank connections 16 into the two large pressurized gas containers 2. These tank connections 16 can simply be designed as end plugs with a bore for receiving the corresponding pipe elements.By modifying the extraction path compared to Figure 1, the fuel always flows through at least one of the two large pressure gas containers 2 to the pressure control unit 9. The fuel is heated in the connecting line 13 via the temperature control device 15, so that the heated fuel maintains the two large pressure gas containers 2 and the medium contained within them at a temperature that reliably prevents shutdown due to falling below a lower limit temperature, typically -40°C. The smaller pressure gas containers are not actively heated in this configuration. However, this is not strictly necessary, as the problem of cooling is less pronounced in the smaller pressure gas containers 2 due to their lower surface area to enclosed volume ratio.

[0043] The idea according to the invention can now be implemented in various other constructive embodiments in a largely analogous manner.

[0044] In the illustration of Figure 3, for example, only the first distributor 7 is present. However, the upper pressure gas container 2, where several could be arranged parallel to each other, now also has a tank connection labeled 16. It is arranged such that its primary side is now on the right, while the secondary side with the tank connection 16 is on the left. This tank connection 16 is connected to the distributor 7 via the check valve 12, allowing fuel to flow from the distributor 7 into the pressure gas container 2. The fuel can then pass through the tank valve 3 of this pressure gas container 2 shown above into the connecting line 13 with the temperature control device 4 and flows into the pressure gas container 2 shown below via the tank connection 16 to heat its contents accordingly.The actual extraction of the compressed gaseous fuel then takes place via the tank valve 3 of the pressure gas container shown below, whereby of course several pressure gas containers 2 could also be used in parallel.

[0045] The larger compressed gas container 2 is thus heated with fuel from the smaller compressed gas container 2. Such a setup would also be possible using a conventional end plug 4 in the smaller compressed gas container 2. This variant can be seen in Figure 4. The smaller compressed gas container 2, which again provides the heated fuel for the larger compressed gas container 2 (shown below), has a conventional end plug 4 on one side and the tank valve on its primary side (shown on the right). This valve is connected to the distributor 7, to which the tank nozzle is also connected. The connecting line 13 then branches off from the distributor 7 to a tank connection 16 of the second large compressed gas container 2 (shown below), in which the temperature control device 15 for temperature control of the fuel is located.Fuel is then drawn from the large pressurized gas container 2 via its tank valve 3 and the corresponding control unit 5. It also flows through the pressure regulator 9 and then, at the lower pressure level (shown with thinner lines), to the consumer 10.

[0046] Instead of the tank connection 16, which could have the check valve 12 in a line to the tank connection 16 or even be integrated into the tank connection 16, the pressurized gas containers 2 can, of course, also be equipped with a tank valve 3 on both the primary and secondary sides. This is illustrated in Figure 5 using the example of two pressurized gas containers 2 of the same size; naturally, the pressurized gas containers 2 could also have different sizes. On the primary side, both pressurized gas containers 2 are connected via their tank valve 3 to the piping system 6 and, in particular, to the distributor 7, which is additionally connected to the tank nozzle 8 and the pressure regulating unit 9 for supplying the consumer 10 with the gaseous fuel. On the secondary side, further secondary-side tank valves 17 are provided, which can, in principle, be identical in design to the tank valves 3.These are connected to the connecting line 13 with the temperature control device 15 located therein. Of course, it would also be possible, similar to the illustrations in Figures 3 and 4, to provide only a tank connection 16 for the lower of the pressurized gas containers 2 instead of the secondary tank valve 17. The functionality is the same here: heated fuel is transferred from one container to the other. The control unit 5 allows for flow both from bottom to top and from top to bottom, as shown in Figure 5. However, special regulatory requirements apply to such interconnections in bundles. When using two secondary tank valves 17, the design is correspondingly more flexible, as the containers can be positioned according to the available installation space in the vehicle 100.

[0047] Figure 6 takes up this principle again and creates a setup in which three pressurized gas containers 2 are used. These also have the tank valve 3 on their primary side and the secondary tank valve 17 on their secondary side. Two connecting lines 13, each including a temperature control device 15, are connected via a distributor 14. This allows fuel to be supplied as temperature-controlled fuel from the lower to the middle pressurized gas container 2 as well as from the lower to the upper pressurized gas container 2. Fuel could also be supplied from the middle to the upper and lower simultaneously, or vice versa, from the upper and lower to the middle pressurized gas container 2 simultaneously. This variant of the storage system 1 offers the greatest flexibility but requires three tank valves 3, 17 on each of the pressurized gas containers 2.

[0048] Figure 7 illustrates this setup again. It is somewhat simplified compared to the setup shown above with regard to the secondary tank valves 17. The secondary tank valves 17 are now designed to include a switchable valve 18 on one side and a check valve 19 on the other. In Figure 7, these are only individually labeled in the upper secondary tank valve 17. This design allows for the use of correspondingly simpler secondary tank valves than the primary tank valves 3. However, this setup requires a significantly more complex pipework arrangement, but in return, it eliminates the need for one of the two temperature control devices required according to Figure 6.The connecting lines are connected here on the side of the check valve to the distributor 14, which is then connected via the section of connecting line 13 containing the temperature control device 15 to a second distributor 20, which in turn is connected to the respective switching valves 18. All the functionalities described above are possible here as well. The possibility of using simpler components and managing with only one temperature control device comes at the cost of additional lines, which is not critical if sufficient installation space is available.

[0049] Finally, Figure 8 shows a vehicle designated 100 in the form of a truck, in the embodiment shown here a combination of tractor unit and semi-trailer. This vehicle 100 has the storage system designated 1 in one of the embodiments described above, with at least two pressurized gas containers 2, which are not explicitly shown and labeled here. Hydrogen is stored in this storage system 1 of the vehicle 100, which is supplied as a consumer 10 to a fuel cell system, also indicated in the vehicle 100, in order to provide drive power for the vehicle 100. In principle, this can be any type of vehicle 100.The vehicle 100 is particularly preferably the truck shown here, since especially in heavy vehicles 100, which require a large amount of drive power, storage systems 1 with a large amount of stored gaseous fuel provide ideal conditions for the use of the storage system according to the invention. Such heavy vehicles require high drive power and thus comparatively large volume flows when extracting hydrogen from the storage system 1. It is particularly advantageous here if the temperature control device 15, in one of the variants described above, can ensure that this power is always available.

Claims

1. Patent claims 1. Storage system (1) for a pressurized gaseous fuel with at least two pressure gas containers (2) which are connected to each other and to filling and withdrawal connections via a piping system (6), and at least one temperature control device (15), wherein the temperature control device (15) is arranged in the piping system (6), characterized in that the temperature control device (15) is arranged in a connecting line (13) between at least two of the pressure gas containers (2).

2. Storage system (1) according to claim 1, characterized in that the connecting line (13) is formed between a primary tank valve (3) of at least one pressurized gas container (2) and a secondary tank valve (17) or a secondary tank connection (16).

3. Storage system (1) according to claim 2, characterized in that the tank connection (16) has a check valve as the only functional element.

4. Storage system (1) according to claim 2 or 3, characterized in that the secondary-side tank valve (17) or the tank connection (16) is exclusively connected to the connecting line or to a connection with the connecting line. Distributors (14, 20) are connected.

5. Storage system (1) according to claim 3, characterized in that the tank connection (16) with the integrated check valve is connected to that area of ​​the piping system which has the filling and withdrawal connections for the gaseous compressed fuel.

6. Storage system (1) according to one of claims 1 to 5, characterized in that the temperature control device (15) comprises a conduit section which is surrounded on the outside by a heat generator.

7. Storage system (1) according to claim 6, characterized in that the heat generator has an electric heating element.

8. Storage system (1) according to claim 6 or 7, characterized in that the heat generator has a burner.

9. Storage system (1) according to one of claims 1 to 5, characterized in that the temperature control device (15) is designed as a heat exchanger, one side of which is flowed through by the gaseous fuel and the other side through which is a heat transfer medium which transfers heat to or from the gaseous fuel.

10. Storage system (1) according to claim 9, characterized in that the heat transfer medium is part of a cooling circuit.

11. Storage system (1) according to one of claims 1 to 10, characterized in that at least two temperature control devices (15) are provided.

12. Storage system (1) according to claim 11 , characterized in that at least one of the tank valves (3, 17), in particular the secondary-side tank valve (17), has separate filling and emptying paths (19, 18).

13. Vehicle (100) with a storage system (1) according to any one of claims 1 to 12.

14. Vehicle (100) according to claim 13, comprising a storage system (1) for storing compressed gaseous hydrogen for a fuel cell system as a consumer (10).

15. Vehicle (100) according to claim 13, comprising a storage system (1) for storing compressed gaseous fuel for an internal combustion engine as a consumer (10).

16. Vehicle (100) according to claim 13, 14 or 15 characterized by its design as a truck.

Images