EP2601433A1

EP2601433A1 - Device for storing low-molecular gases

Info

Publication number: EP2601433A1
Application number: EP11736290.5A
Authority: EP
Inventors: Jens Franzen; Gerardo Friedlmeier; Kai Kioschis; Detlef Zur Megede
Original assignee: Daimler AG
Current assignee: Mercedes Benz Group AG
Priority date: 2010-08-06
Filing date: 2011-07-26
Publication date: 2013-06-12
Also published as: CN103069207A; DE102010033597A1; WO2012016655A1; JP2013532809A; US8998024B2; US20130174920A1; JP5815031B2

Abstract

The invention relates to a device (5) for storing low-molecular gas (for example hydrogen (H₂)) under high pressure, comprising an inner shell (6) and at least an outer sleeve (7) enclosing the inner shell (6). The region between the inner shell (6) and the outer sleeve (7) is connected to the region enclosed by the inner shell (6) via at least one valve device (9) having a backflow preventer. The valve device (9) having a backflow preventer is designed in such a manner that low-molecular gas that has diffused through the inner shell (6) can flow back into the inner shell (6) under suitable pressure conditions.

Description

Device for storing low molecular weight gases

The invention relates to a device for storing low molecular weight gases under high pressure according to the closer defined in the preamble of claim 1.

Devices for storing gases or compressed gas storage are known from the general state of the art. Typically, such

Pressure gas storage divided into different types. For example, a so-called type II compressed gas storage is a compressed gas storage with an inner shell made of high-strength steel and an outer shell surrounding this inner shell, for example made of fiber-reinforced material. A Type I II pressure accumulator has an inner shell

Aluminum on and a type .IV pressure accumulator typically has an inner shell of a plastic material, for example of high density polyethylene (HDPE), which is surrounded by at least one outer sleeve of fiber reinforced material.

Such compressed gas storage devices serve as devices for storing gases under high pressures. In general, pressures of the order of about 350 bar, in the order of about 700 bar or even in the order of 1100 to 1200 bar provided in order, especially for light gases, the largest possible amount of gas in a relatively manageable volume to store the device.

Now, if low molecular weight gases, in particular hydrogen, are stored under high pressure in the device for storing the gas, it is virtually unavoidable in practice that small amounts of the low molecular weight gas will diffuse through the device and escape into the environment. This is generally unproblematic because of the relatively small amount. However, in certain situations, some amount of hydrogen diffuses through the inner shell and stays in the area between the inner shell and the outer shell. In normal operation, a slow diffusion of this hydrogen through the outer shell will occur, so that no problem arises. In an almost empty

However, pressurized gas storage can now come to decisive problems. When refueling occurs in the inner shell relatively quickly to a pressure increase from a very low residual pressure at nearly empty pressure gas storage to a very high pressure at fully pressurized compressed gas storage, for example, to a pressure in the order of the above-mentioned 700 bar. Since the inner shell typically has a certain elasticity, and in particular if this as

Plastic inner shell is formed in a type-IV-pressure gas storage, it comes through the relatively rapid increase in pressure that located between the inner shell and the outer shell of the gas cushion through the inner shell

diffused low molecular weight gas can be placed under a relatively high pressure. In these situations, the gas then passes relatively quickly through the outer shell, so that forms in the environment of the outer shell in these situations, a gas cloud, the concentration of which is significantly higher than is the case when diffusing through the walls of the compressed gas storage in normal operation. Now, if the tightness of the compressed gas storage is determined by appropriate detectors, in particular the tightness of compressed gas storage, which for the storage of

Fuel gas are used in vehicles, this concentration is typically so high that an alarm is triggered and this generally leads to an emergency shutdown of the system, such as an emergency shutdown of refueling.

From DE 2008 039 573 A1 a compressed gas storage is known, which is constructed with an inner shell and at least one outer shell. In the region between the inner shell and the at least one outer shell in this case a diffusion layer is arranged, which is adapted to the low molecular weight gas, that

optionally diffused through the inner shell, to collect specifically and to derive via a connection element. Since this derivation can be done with relatively low pressure loss and thus offers a much lower diffusion resistance than the penetration of the outer shell, by the inner shell may diffused low molecular weight gas follow this path and can be selectively removed from the region of the diffusion layer.

The structure has the disadvantage that it is relatively expensive and

Gas losses from the compressed gas storage does not restrict, but the diffusion through the inner shell through even favors, as it provides a way to flow out of the diffusing through the inner shell gas with very low pressure loss available and thus rather accelerated by the pressure drop diffusion.

Object of the present invention is to provide a structure of a device for storing low molecular weight gas under high pressure, which avoids the disadvantages mentioned, minimizes the loss of gas by diffusion and

in particular the problem of a refueling abruptly when refueling

Gas concentration in the environment of the device prevented.

According to the invention this object is achieved by the features mentioned in the characterizing part of claim 1. Advantageous developments of the device according to the invention will become apparent from the dependent claims. A particularly preferred use of the device according to the invention is specified in claim 11. An advantageous development of this can be found in the dependent

Under claim.

The solution according to the invention therefore provides that the device has in the area between the inner shell and the outer shell at least one valve device with a backflow safety device, which connects this area between the inner shell and the outer shell with the interior of the inner shell. The Rückströmsicherung is designed so that through the inner shell diffused gas can flow back under suitable pressure conditions in the inner shell. The construction with the

Backflow preventer thus allows gases from the area between the

Inner shell and the outer shell can flow back into the area within the inner shell. In the regular operation of the device, it is now becoming the inevitable

Losses of hydrogen by a diffusion of the hydrogen through the inner shell and then possibly also the outer shell come. In the regular operation of the device also typically the pressurized low molecular weight gas is removed from the area of the device, so that the Device or the area in the inner shell gradually becomes empty and loses pressure. When this situation occurs and is in the range between the

Inner shell and the outer shell is still low molecular weight gas, which was diffused through the inner shell, so this is whenever the pressure in the inner shell is smaller than the pressure in the area between the inner shell and outer shell, through the valve means with the Rückströmsicherung in the inner shell

flow back. This can achieve two effects. First, at least a portion of the low molecular weight gas diffused through the inner shell becomes

recovered by this can flow back in the region of the inner shell with empty or almost empty device. In addition, whenever the device is comparatively empty, such a backflow is made possible, so that in these operating situations little or no low molecular weight gas is between the inner shell and the outer shell. If the device is refueled again and the inner shell is thus subjected to a relatively high pressure in a comparatively short time, then no or at most very little gas can be forced through the outer sheath, so that an increase in the concentration of the low molecular weight gas in the vicinity of the device during refueling safely and reliably avoided.

The particular advantage of the structure is therefore on the one hand that safety-critical situations in the refueling through from the area between the inner shell and

Exiting gas can be prevented on the outer shell, and at the same time that at least part of the gas diffused through the inner shell flows back into the interior of the inner shell and can be used as intended. The backflow protection is of course designed so that a flow from the region of the inner shell is prevented in the area between the inner shell and outer shell.

In a particularly favorable and advantageous development of the device according to the invention, it may further be provided that the at least one valve device is biased by a spring means in the closed state. Such

Preload via a spring means which, for example, as a coil spring,

Compression spring or as a torsion spring in a suspension point of a flap or

may be formed, presses the non-return valve of the valve device supportive to the pressure of the gas in the inner shell in the closed Status. Only when a clear pressure difference between the area between the inner shell and the outer shell on the one hand and the inner shell on the other hand, opens the at least one valve device against this spring force and leaves the gas under higher pressure from the area between the inner shell and the outer shell in the area flow back the inner shell. The spring means can thus prevent that at comparatively balanced pressure situations, an opening of the valve device takes place, so possibly located in the interior of the inner shell gas through the valve devices themselves in the area between

Inner shell and outer shell could flow out, which is particularly the case when comparatively high pressures are present, which are transmitted through an inner shell, which has a certain elasticity, in the manner of a membrane on the area between the inner shell and the outer shell. At approximately equal pressures, it could then result in accidental opening in situations where this is not desired. By the spring means in the described development of the invention, this is reliably and reliably prevented.

In a further particularly advantageous embodiment of the invention

Device, it is further provided that the at least one valve device is formed so that its greatest structural extent is disposed in the interior of the inner shell. This structure could for example be realized in the form of a spring-loaded flap inside the inner shell, which closes openings in the inner shell in the normal state and always releases when the pressure in the region of the inner shell significantly smaller than the pressure in the area between the inner shell and

Outer shell is. The structural integration into the interior of the inner shell then allows the conventional construction of the device, for example as type IV compressed gas storage, so that the inner shell with built-valve devices can be easily wrapped by impregnated with binder fibers without valve devices or the like on the profile of the inner shell stand out and affect the structure by a change in the geometric shape of the outer shell or weaken its stability.

In an alternative or additional embodiment of the invention

Device is further provided that the at least one valve device is arranged in the region of a connecting element for refueling / removal of the low molecular weight gas. So it can be one or more of them Valve means may be provided in the region of the connection element. In such a connection element is typically a passage through the

different layers of the construction of the device. The connecting element is therefore connected to the front side both with the inner shell and the outer shell. Between these two areas, there is also a region of the connecting element which is connected to the area between inner shell and outer shell. From this area can now be made for example by a bore or the like, a connection to the interior of the inner shell. In this connection, a conventional check valve, in particular a spring-loaded check valve according to the embodiment described above can then be introduced. At least one of the at least one valve devices can be integrated into the construction of the connecting elements without significant additional expenditure.

In a particularly favorable and advantageous development of the device according to the invention, it is provided that the low molecular weight gas is formed as hydrogen. In particular, in the storage of hydrogen, for example under pressures of more than 350 or in particular more than 650 bar, it inevitably leads to a diffusion through the inner shell of the device, so specifically in the

Storage of hydrogen by the hydrogen absorbing material can be prevented too high hydrogen concentration in the environment of the device during refueling. Since hydrogen together with oxygen can form an ignitable mixture, a necessary safety shutdown can be reliably and reliably avoided if the concentration of hydrogen in the environment of the device is too high.

A particularly preferred use of the device according to the invention in one of the abovementioned embodiments always results when it comes to

Pressure gas storage is, which must be emptied relatively frequently and refueled. The device can therefore be used in particular for storing fuel in a vehicle. Such a vehicle, which is operated for example via an internal combustion engine with hydrogen or another low molecular weight gas, can be equipped with the device particularly efficiently. Due to the typically relatively high consumption of fuel, it is not expected that the fuel will be stored too long in the device, so that diffusion, which is unavoidable at least in the case of hydrogen, is not a major problem. There However, the device for storing the gas must be refueled relatively frequently, the solution according to the invention, which prevents too high a concentration of the gas around the device when refueling the same, represents a decisive advantage for this type of application.

A particularly preferred use is in the range of

Fuel cell vehicles in which the hydrogen in such

Devices according to the invention can be stored in a particularly user-friendly, since they can store a sufficient amount of hydrogen, for example, at a pressure level of 700 bar at a reasonable volume in order to achieve a good range of the vehicle. Unpleasant emergency shutdowns while refueling can be avoided reliably and without security risk.

Further advantageous embodiments of the device according to the invention will become apparent from the remaining dependent claims and are based on the

Embodiment clear, which is explained below with reference to the figures.

Showing:

Fig. 1 is a principle indicated fuel cell vehicle with a

Inventive device for storing hydrogen;

2 shows the device according to the invention for storing hydrogen in a cross section;

3 shows a first embodiment of a valve device according to the invention;

4 shows a second embodiment of a valve device in a first state; and

5 shows a second embodiment of a valve device in a second state.

In the illustration of Figure 1, a vehicle 1 can be seen. This indicated in principle vehicle 1 is intended to be driven by a direction indicated in the wheels of the electric motor 2, said electric motor 2 via a

Power electronics 3 is supplied with electrical power from a fuel cell 4 in a conventional manner. The power electronics 3 can also have an electrical buffer, for example a battery. Of the

Buffer can be used in particular for receiving recuperated braking energy. The fuel cell 4 are doing in a manner also known per se Way and supplied oxygen or air and hydrogen H ₂ for generating the electric power. The hydrogen comes from one or more, possibly distributed over the vehicle 1 arranged devices 5 for

Store hydrogen H ₂ under high pressure. The device or the compressed gas storage device 5 is typically operated at a pressure level of, for example, 350 or 700 bar and, in the exemplary embodiment shown here, should be designed as a so-called type IV compressed gas reservoir 5.

Such a type IV compressed gas storage consists, as can be seen in more detail in the sectional view of Figure 2, of an inner shell 6 and at least one of the

Inner shell 6 surrounding outer shell 7, which may be constructed, for example, of one or more layers. In a type IV compressed gas storage device 5, the inner shell 6 is made of a plastic, typically of a high density polyethylene (HDPE). This comparatively soft and elastic inner shell 6 is then surrounded by the outer shell 7, which is typically formed of a fiber-reinforced material. Typical for the construction of the

Outer shell 7 is a structure made of carbon fibers, which either with a

Binders or resin are preimpregnated or immediately before the

Applying to the inner shell 6 soaked with such. The outer shell 7 may consist of long fiber webs, which are wound, for example, in the production of the compressed gas storage 5 to the inner shell 6, the so-called liner. The structure thus has a very high mechanical stability at very low weight. Often the end regions are included in one or both

Connection elements 8, so-called domes, of metallic material, such as aluminum, arranged, which have the connections for refueling and removal of the hydrogen H ₂ from the compressed gas storage 5. In the illustration of Figure 2, only one connection element 8 is shown on one side of the compressed gas reservoir 5.

Both the material of the inner shell 6 and that of the outer shell 7 typically can not be formed such that it permanently and reliably encloses the hydrogen H ₂ in the interior of the compressed gas reservoir 5 over a long period of time. A very small amount of hydrogen H ₂ will typically always diffuse out of the compressed gas reservoir 5 through the inner shell 6 and the outer shell 7, so that slight losses of hydrogen H _{2 are} unavoidable. The very small one Amounts of hydrogen H ₂₎ which during normal operation of the compressed gas storage 5 in the vehicle 1 through the compressed gas storage. 5

Diffuse out, are thereby relatively uncritical and simply flow off to the environment. It becomes critical or problematic only when higher concentrations of hydrogen H ₂ diffuse through the walls of the compressed gas reservoir 5 and thus due to the comparatively high

Concentration of hydrogen in the vicinity of the compressed gas storage 5, the formation of an ignitable mixture or the formation of detonating gas is to be feared. For the detection of such critical concentrations, therefore, hydrogen sensors are almost always present which trigger an alarm and possibly a system shutdown when limit concentrations are exceeded.

During operation of the vehicle 1, the compressed gas storage 5 will continue to empty due to the hydrogen consumption of the fuel cell 4, whereby the pressure inside the inner shell 6 decreases accordingly. Hydrogen H ₂ , which has already diffused through the inner shell 6, can collect in particular in these situations in slightly larger amounts between the inner shell 6 and the outer shell 7. With a comparatively empty inner shell 6 and thus comparatively low pressure in the compressed gas storage 5, this gas collected between the inner shell 6 and the outer shell 7 will remain in this area for a comparatively long time. If the vehicle 1 now comes to a refueling of the compressed gas reservoir 5, fresh hydrogen H ₂ is conducted via the connection 8 into the region of the compressed gas reservoir 5 at a pressure of 700 bar. The pressure inside the inner shell 6 increases comparatively quickly to this 700 bar. The formed in the area between the inner shell 6 and the outer shell 7 pads on hydrogen H ₂ , which through the

Inner shell 6 are diffused therethrough, are thereby pressed in a conventional structure by the outer shell 7 to the outside of the compressed gas storage 5, so suddenly here in a very short period of time, a very high concentration of hydrogen H ₂ occurs. This then typically triggers the safety alarm, which is accompanied by a system shutdown and in particular a termination of the refueling process. However, since there is no real leakage or leakage of the compressed gas container 5 in these situations, but only an increased

Hydrogen concentration has occurred due to the structural characteristics of the gas cylinder 5, this safety alarm and especially in the emergency shutdown is a very annoying process. In the illustration of Figure 2 are therefore in the area between the inner shell 6 and the outer shell 7 valve devices 9 can be seen, which connect the area between the inner shell 6 and the outer shell 7 with the interior of the inner shell 6. One of the valve devices 9 is exemplary in the cylindrical region of the

Pressure gas accumulator 5 arranged, the other of the valve means 9 is shown by way of example in the region of the connecting element 8. The two valve devices 9, of which in principle only one or more can be arranged distributed over the compressed gas storage 5, are in this case valve devices 9 with

Return valve. They are designed so that the hydrogen contained in the interior of the inner shell 6 H ₂ in the regular operating condition not through the

Valve means 9 can pass. If there is now a diffusion of the hydrogen H ₂ in the interior of the inner shell 6 through this inner shell 6 into the area between the inner shell 6 and the outer shell 7, then the hydrogen H ₂ or at least the hydrogen H ₂ , which is not yet permeable the outer shell 7

diffused through and has flowed away, collecting in the area between the inner shell 6 and the outer shell 7.

If the vehicle 1 is now operated with the hydrogen H ₂ from the compressed gas reservoir 5, the compressed gas reservoir 5 will become increasingly empty over time. If this is almost or completely empty, it will have a comparatively low pressure inside the inner shell 6. In these situations, in which refueling is typically imminent, the gas located between the inner shell 6 and the outer shell 7 will then flow back into the area inside the inner shell 6 via the valve devices 9 with backflow protection, as soon as the pressure inside the inner shell 6 is smaller or significantly smaller than in the area between the inner shell 6 and the outer shell 7. The in the region of the inner shell. 6

Returning gas is thus not lost and can be reused. The special effect, however, is that after such a situation typically a refueling of the compressed gas reservoir 5 occurs in a timely manner. Since previously due to the low pressure in the interior of the inner shell 6 of the inner shell 6 and outer shell 7 located hydrogen H _{2 has} flowed back into the interior of the inner shell, this can at a pressure increase in the interior of the inner shell 6, as in the refueling typically within a very short period of time, not through the outer shell. 7 be pushed through, since he has previously flowed back through the valve means 9 in the interior of the inner shell 6.

In the illustration of Figure 3, a first possible embodiment of such a valve device 9 is indicated in principle. In the illustration of Figure 3 is a part of the inner shell 6 and a part of the outer shell 7 as a section of the connecting element 8 can be seen. The area between the inner shell 6 and the outer shell 7 is connected via a conduit element in the connecting element 8 with the interior of the inner shell 6. In the region of the line element, the valve device 9 is arranged as a spring-loaded check valve of simple design. Such a spring-loaded check valve simple design is known and customary, so that here only the usual symbolism is shown and no structural design must be specified. Such a check valve with spring load can be designed to be integrated in the region of the connecting element 8. In principle, a simple check valve without spring load would fulfill the task of the invention in any case. Since in particular in a type IV compressed gas storage with an inner shell 6 made of plastic this has a certain flexibility and transmits the pressure present in the interior in the manner of a membrane on the area between the inner shell 6 and the outer shell 7, it may in different situations come to an equal or approximately equal pressure between the two areas. In these situations, the valve device 9 could then open briefly with slight pressure differences, so that it could possibly also due to slight pressure fluctuations to a flow of hydrogen H ₂ through the valve device into the area between the inner shell and the outer shell 7. To avoid this safely and reliably, the valve device 9 may be formed as a spring-loaded check valve. By the spring then the valve device can be kept in its "closed" position, so that only at a pressure difference, which additionally overcomes the force of the spring, a back flow of hydrogen H ₂ from this area in the interior of the inner shell 6 is possible.

In the illustration of Figure 4, an alternative embodiment of the valve device 9 can be seen. Again, a section of the inner shell 6 and the outer shell 7 is shown again. The valve device 9 consists in this case of a simple flap 10, which is connected via a pivot point 11 with the inner shell 6. The flap is doing so on an opening 12 through the inner shell 6 so that this flap 10, the opening 12 seals, as long as the pressure in the interior of the inner shell 6 is higher than the pressure between the inner shell 6 and the outer shell 7. Again, this seal can be reinforced by a spring, which may be formed for example as a torsion spring in the region of the pivot point 11.

In the illustration of Figure 5, the same structure as shown in Figure 4 is again to recognize, in which case a state is shown in which in the region of the opening 12 and between the inner shell 6 and the outer shell 7, the pressure is higher than in the interior of the inner shell 6. Such a situation will typically occur when the compressed gas reservoir 5 is comparatively empty and the pressure in the interior of the inner shell 6 drops correspondingly. In these situations, the flap 10 opens around the fulcrum 11, thus allowing the higher pressure hydrogen H ₂ in the region between the inner shell 6 and the outer shell 7, as indicated by the arrow, to enter the region inside the inner shell 6 can flow back. In these situations, which typically occur before refueling of the compressed gas reservoir 5, a backflow of the hydrogen H ₂ from the region between the inner shell 6 and the outer shell 7 can be achieved. The backflowing

Hydrogen H ₂ is not lost, but is still available.

In particular, however, a hydrogen cushion between the inner shell 6 and the outer shell 7 is removed or significantly reduced in volume. At a

Pressurization of the inner shell 6 by refueling can then

Pressing this hydrogen cushion through the outer shell 7 can be prevented because this pad is no longer present or is present only in such a small amount that leaking hydrogen triggers no alarm and no

causing safety-critical conditions.

The structure, as described here, thus allows with very simple and thus comparatively inexpensive valve devices 9, an automatic backflow of located in the region between the inner shell 6 and the outer shell 7

Gas cushion immediately before refueling the compressed gas reservoir 5, when the pressure conditions in the interior of the inner shell 6 are so low by an empty in operation pressure gas accumulator 5 that the valve device 9, preferably against a spring force, the flow path releases. The valve devices 9 are integrated either in the region of the connecting element 8 or structurally in the interior of the inner shell 6, so that the outer shell 7, as in conventional inner shells 6 without such internals, can be wound around this, without bulges or recesses in the Outer shell 7 will be necessary. This makes it possible to achieve a simple and safe construction.

In addition, the integration or at least predominantly structural

Integration of the valve means 9 in the interior of the inner shell 6 a very safe construction, as over the interior of the inner shell 6 and the outer shell 7 protruding structures could be very easily damaged, for example, during installation or in particular in the case of accidents or the like, which then to a leaky Pressure gas storage 5 with the appropriate security risk can lead.

Claims

claims

Device for storing low molecular weight gases under high pressure with an inner shell (6) and at least one outer shell (7) surrounding the inner shell (6),

characterized in that

the region located between the inner shell (6) and the outer shell (7) is connected to the region surrounded by the inner shell (6) via at least one valve device (9), so that low molecular weight gas diffused through the inner shell (6) at suitable pressure ratios into the Inner shell (6) can flow back.

Device according to claim 1,

characterized in that

the at least one valve device (9) is biased by a spring means in the closed state.

Apparatus according to claim 1 or 2,

characterized in that

the at least one valve device (9) is designed such that its greatest physical extent is arranged in the interior of the inner shell (6).

Apparatus according to claim 1 or 2,

characterized in that

the at least one valve device (9) is arranged in the region of a connection element (8) for refueling / removal of the low molecular weight gas.

5. Apparatus according to claim 4,

characterized in that

the at least one valve device (9) is designed as a check valve.

6. Device according to one of claims 1 to 3,

characterized in that

the at least one valve device (9) is designed as a flap (10) in the region of a wall of the inner shell (6).

7. Device according to one of claims 1 to 6,

characterized in that

the inner shell (6) is formed from a plastic.

8. Device according to one of claims 1 to 7,

characterized in that

the at least one outer shell (7) is formed of a fiber-reinforced material.

9. Apparatus according to claim 1 to 8,

characterized in that

the low molecular weight gas is hydrogen (H ₂ ).

10. Device according to one of claims 1 to 9,

characterized in that

the low molecular weight gas at a pressure of more than 300 bar, in particular more than 650 bar, is stored.

11. Use of the device according to one of claims 1 to 10, for storing fuel in a vehicle (1).

12. Use according to claim 10,

characterized in that

the vehicle (1) is designed as a fuel cell vehicle.