Refuelling method and tank system

Abstract

The proposed invention relates to a refuelling method (100) for refuelling a hydrogen tank (201). The refuelling method (100) comprises: - supplying (101) hydrogen into the hydrogen tank (201) via a refuelling path (207) of a tank valve (203) of the hydrogen tank (201), - opening (103) a pilot valve (217) of a shut-off valve (213) arranged in the withdrawal path (209) of the tank valve (203), while a pressure in the hydrogen tank (201) increases. The invention further relates to a tank system for storing hydrogen.

Description

[0001] Description

[0002] title

[0003] Refueling procedure and tank system

[0004] The presented invention relates to a refueling method for refueling a hydrogen tank and a tank system for storing hydrogen according to the appended claims.

[0005] State of the art

[0006] Tank valves for hydrogen tanks typically comprise a refueling path through which hydrogen is fed into a gas storage unit or a hydrogen tank during refueling, and a withdrawal path through which hydrogen is fed from the hydrogen tank to one or more consuming systems during normal operation.

[0007] A main check valve can be located in the refueling path, which only allows gas flow in the direction of the hydrogen tank and closes in the opposite direction.

[0008] An electrically operated shut-off valve (SOV) can be located in the extraction path, which is electrically activated during normal operation and therefore remains open. Since a large opening cross-section must usually be released, a very powerful actuator would be required to open the shut-off valve, the installation space of which would normally significantly exceed the available space. Therefore, such shut-off valves are usually designed as a two-stage valve. This means that a pilot valve is provided with a small seat diameter and stroke. The pilot valve is loaded by a spring with a preload force acting in the closing direction.

[0009] In the resting state, the pilot valve is supported by a valve element on a main valve, i.e., a second valve stage, so that the preload force acts equally on the valve elements of the pilot and the main valve in their closing direction.

[0010] In addition to this spring force, three additional pneumatic forces act on the valve element of the main valve. A control chamber pressure exists on an upstream face of the main valve element. This pressure exerts a closing force on the main valve element.

[0011] The control chamber is connected to an inflow side of the shut-off valve via a very narrow first throttle.

[0012] When the pilot valve is closed, the pressure in the control chamber is the same as on the upstream side of the shut-off valve. The downstream area is divided into two sections by the main valve's sealing seat. The pressure upstream of the shut-off valve acts on the section outside the sealing seat, exerting an opening force on the valve element. In contrast, the pressure downstream of the shut-off valve acts on the section inside the sealing seat, exerting a further opening force on the valve element.

[0013] If the pressure upstream of the shut-off valve is greater than downstream and the pilot valve is not actuated, the closing force outweighs the opening force and the main valve is pressed into its sealing seat and remains closed.

[0014] If the pressure on both sides of the shut-off valve is the same and the pilot valve is not activated, the pneumatic forces in the closing and opening directions cancel each other out, but the preload force of the spring continues to act on both valve elements in the closing direction and keeps the valves closed.

[0015] When the pilot valve is activated and opened, the control chamber is connected to the downstream side of the shut-off valve via the open valve and a second throttle. The flow cross-section of the second throttle is usually significantly larger than that of the first throttle.

[0016] If the pressure on the downstream side of the shut-off valve is lower than on the upstream side, the pressure in the control chamber drops significantly below the pressure on the upstream side of the shut-off valve, so that with this pressure, the pneumatic closing force on the main valve element also decreases. The main valve opens, and gas can now flow from the hydrogen tank to the consuming systems via the open main valve seat.

[0017] If the pilot valve is closed again, the control chamber pressure rises again to the pressure on the inflow side of the shut-off valve and the spring force subsequently causes the main valve to close.

[0018] During refueling, the shut-off valve is not activated and external pressure is applied to the downstream side of the shut-off valve. If this pressure exceeds the pressure in the hydrogen tank, the main check valve in the refueling path opens. Since a significant mass flow of hydrogen is passed through the main check valve during refueling, a significant pressure drop occurs at this valve. The pressure downstream of the shut-off valve is therefore greater than that upstream of the shut-off valve and in the control chamber. This creates a resulting pneumatic force on the main valve element in the opening direction. If this force exceeds the closing spring force, the main valve opens slightly without the shut-off valve being activated. As a result, part of the hydrogen mass flow supplied during refueling can flow backwards via the shut-off valve.

[0019] Since the medium supplied during refueling can also contain portions of liquid water and, in addition, the hydrogen cools down significantly locally in the narrow flow cross-sections of the slightly opened shut-off valve, water in the shut-off valve can freeze into ice and subsequently block the shut-off valve.

[0020] To prevent this, an additional check valve can be installed in series with the shut-off valve downstream of the shut-off valve. This additional check valve prevents flow through the withdrawal path in the refueling direction, but allows flow in the withdrawal direction without significant pressure loss.

[0021] Before a refueling process, the system is in a resting state, and a starting pressure prevails everywhere. To initiate the refueling process, a pressure greater than the starting pressure is applied from the outside to the downstream side of the additional check valve and to the upstream side of the main check valve, causing the main check valve in the refueling path to open. A hydrogen mass flow specified by the filling station is then directed to the hydrogen tank via the open main check valve, increasing the pressure in the hydrogen tank. This mass flow causes a pressure drop at the open main check valve, so that the pressure on the upstream side of the main check valve and thus on the downstream side of the additional check valve is even higher than the pressure in the hydrogen tank.

[0022] The refueling process continues until the pressure on the upstream side of the main check valve reaches a target value. Since both the auxiliary check valve and the shut-off valve are closed during the refueling process, the initial low starting pressure is maintained on the downstream side of the shut-off valve and thus also on the upstream side of the auxiliary check valve. Consequently, both the main valve element of the shut-off valve and the valve element of the auxiliary check valve are pressed into their respective sealing seats with very high and ever-increasing forces during the refueling process. This places a very high load on these sealing seats, for which they are generally designed, but which, if occurring frequently, can nevertheless negatively affect the permissible operating life of the tank valve.A known solution to avoid this high seat load is to replace the additional check valve with a throttle check valve. This makes it a throttle valve rather than a check valve. Such a valve no longer seals in the reverse direction, but rather acts as a throttle, while allowing the gas flow to pass largely unhindered in the forward direction. Such a bypass throttle can be integrated into the valve element of the throttle check valve, thus eliminating the need for additional components.

[0023] During refueling, the pressure downstream of the shut-off valve is the same as upstream of the main check valve. If the pressure drop across the main check valve is so great that the main valve of the shut-off valve opens, it only opens wide enough to allow a very small gas flow through the series connection of the throttle check valve and the shut-off valve.

[0024] Due to the pressure drop at the throttle of the throttle check valve, the gas pressure at the outlet of the shut-off valve decreases with increasing

[0025] The volume flow decreases more and more, so that with a low gas flow, which is essentially determined by the throttle of the throttle check valve, an equilibrium is established backwards via the shut-off valve.

[0026] Accordingly, the throttle check valve does not prevent the flow of gas through the shut-off valve in the reverse direction, but it does significantly reduce it. This significantly reduces the risk of liquid water penetrating the shut-off valve and subsequently freezing it. However, a residual risk remains with this state-of-the-art solution.

[0027] Disclosure of the invention

[0028] Within the scope of the invention presented, a refueling method and a tank system are presented. Further features and details of the invention emerge from the respective subclaims, the description, and the drawings. Features and details described in connection with the refueling method according to the invention naturally also apply in connection with the tank system according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is always made to each other.

[0029] The invention presented serves, in particular, to completely prevent reverse flow through a shut-off valve of a tank system during refueling, without causing high seat loads in the main valve of the shut-off valve and the additional check valve. In particular, the invention presented serves to protect the respective seals or sealing seats of a tank system and, as a result, to provide a particularly robust tank system.

[0030] Thus, according to a first aspect of the invention presented, a refueling method for refueling a hydrogen tank is presented.

[0031] The presented refueling method comprises supplying hydrogen into the hydrogen tank via a refueling path of a tank valve of the hydrogen tank and opening a pilot valve of a shut-off valve arranged in the withdrawal path of the tank valve while a pressure in the hydrogen tank increases.

[0032] The refueling process presented here is based on the opening of a pilot valve of a shut-off valve located in the tank valve's discharge path. When the pilot valve opens, gas flows from the shut-off valve's control chamber through its outlet throttle into the gas volume between the shut-off valve and the auxiliary check valve. This causes the pressure in this gas volume to equalize with the pressure in the hydrogen tank. However, since the pressure is slightly lower than the pressure on the downstream side of the auxiliary check valve due to a pressure drop at a main check valve, the auxiliary check valve remains closed at all times, preventing gas from entering the shut-off valve's pilot valve and thus the shut-off valve itself via the downstream side.It can be provided that the pilot valve is opened in such a way that fluid flows from a first space between the hydrogen tank and the pilot valve into a second space after the pilot valve and before an additional check valve arranged in the extraction path, so that the fluid minimizes a pressure difference between the second space and a third space, wherein the third space is located between the additional check valve and a main check valve arranged in the extraction path.

[0033] It may further be provided that the pilot valve is opened for a period of between 50 milliseconds and 5 seconds, in particular between 100 milliseconds and 500 milliseconds.

[0034] Briefly and repeatedly opening and closing the pilot valve during the entire hydrogen tank filling process, especially for a duration of 200 ms each, does not cause the main valve of the shut-off valve to open. Even if the main valve of the shut-off valve were to open because a pilot valve control pulse was selected to be somewhat longer and / or because the volume between the shut-off valve and the auxiliary check valve is somewhat larger than usual, which would cause a prolonged pressure drop in the shut-off valve's control chamber, the auxiliary check valve would remain closed.

[0035] Even when the main valve of the shut-off valve is open, the pressure between the shut-off valve and the additional check valve can never exceed that in the hydrogen tank, while a slightly higher refueling pressure is present on one downstream side of the additional check valve.

[0036] It may also be provided that the pilot valve is opened and closed repeatedly.

[0037] Repeating the short control pulses for the pilot valve of the shut-off valve throughout the entire hydrogen tank filling process ensures that a maximum pressure difference can build up across the shut-off valve and the additional check valve that is equal to the pressure increase in the hydrogen tank during the time interval between two control pulses. The seat load for a sealing seat of the main valve of the shut-off valve and a sealing seat of the additional check valve during the hydrogen tank filling process is reduced significantly compared to filling the hydrogen tank with hydrogen without opening the pilot valve. Accordingly, the service life of the sealing seats is significantly extended.

[0038] It may further be provided that the pilot valve is opened in such a way that a main valve of the shut-off valve does not open.

[0039] To prevent the main valve of the shut-off valve from opening, the duration of a control pulse for the pilot valve can be selected such that the pilot valve opens, but the main valve of the shut-off valve does not move. A duration of 200 ms has proven particularly suitable for this purpose.

[0040] It may also be provided that the pilot valve is permanently open while the hydrogen tank is being filled with hydrogen.

[0041] By continuously opening the pilot valve while filling the hydrogen tank with hydrogen, the pressure in the volume between the shut-off valve and the additional check valve continuously follows a slowly increasing pressure in the hydrogen tank. Although the main valve of the shut-off valve may also open in this case, the additional check valve remains closed in all cases, so that 100% of the refueling gas flow is directed via the refueling path with a main check valve. Accordingly, only a forward gas flow flows via the pilot valve and, if necessary, partially via a main valve of the shut-off valve, which is required for the slow pressure build-up between the shut-off valve and the additional check valve. This gas flow is not branched off from the refueling gas flow, but rather taken from the hydrogen tank.It bears the same relationship to the refueling gas flow as the gas volume between the shut-off valve and the additional check valve bears to the gas volume in the hydrogen tank. There is no risk of icing in this case. Furthermore, the pilot valve can be set to open at a predetermined time after the start of hydrogen supply to the hydrogen tank.

[0042] A predetermined period of time, such as 200 ms, which elapses after the start of supplying hydrogen into the hydrogen tank until the pilot valve is opened, allows a build-up of pressure in the refueling path of the tank valve so that the pilot valve closes again after a control pulse.

[0043] According to a second aspect, the presented invention relates to a tank system for storing hydrogen.

[0044] The presented tank system comprises a hydrogen tank, a tank valve and a computing unit, wherein the tank valve comprises a refueling path and a withdrawal path, wherein a main check valve is arranged in the refueling path, wherein a shut-off valve and an additional check valve are arranged in the withdrawal path, wherein the shut-off valve comprises a pilot valve and a main valve, and wherein the computing unit is configured to open the pilot valve during a refueling process for filling the hydrogen tank with hydrogen while a pressure in the hydrogen tank increases.

[0045] The tank system presented is used in particular to carry out the refueling process presented.

[0046] Accordingly, it can be provided that the computing unit is configured to open the pilot valve according to a possible embodiment of the presented refueling method.

[0047] It can further be provided that the computing unit is configured to enable a closing movement of the pilot valve as soon as the filling of the hydrogen tank with hydrogen is complete. To enable a closing movement of the pilot valve, for example, a control pulse for controlling the pilot valve can be interrupted.

[0048] Advantages that are described in detail for the refueling method for refueling a hydrogen tank according to the first aspect of the invention apply equally to the tank system for storing hydrogen according to the second aspect of the invention.

[0049] Further advantages, features, and details of the invention will become apparent from the following description, which describes exemplary embodiments of the invention in detail with reference to the drawings. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination.

[0050] Drawings

[0051] They show:

[0052] Figure 1 shows a possible design of the presented refueling process,

[0053] Figure 2 shows a possible design of the presented tank system.

[0054] Description of the embodiments

[0055] Figure 1 shows a refueling method 100 for refueling a hydrogen tank.

[0056] The refueling method 100 includes a refueling step 101 in which hydrogen is introduced into the hydrogen tank via a refueling path of a tank valve of the hydrogen tank.

[0057] Furthermore, the refueling method 100 includes an opening step 103, in which a pilot valve of a shut-off valve arranged in the withdrawal path of the tank valve is opened while pressure in the hydrogen tank increases. Figure 2 shows a tank system 200 for storing hydrogen.

[0058] The tank system 200 comprises a hydrogen tank 201, a tank valve 203 and a computing unit 205.

[0059] The tank valve 203 in turn comprises a refueling path 207 and a removal path 209, wherein a main check valve 211 is arranged in the refueling path 207 and a shut-off valve 213 and an additional check valve 215 are arranged in the removal path 209.

[0060] The shut-off valve 213 comprises a pilot valve 217 and a main valve 219.

[0061] The computing unit 205 is configured to open the pilot valve 217 during a refueling process for filling the hydrogen tank 201 with hydrogen while the pressure in the hydrogen tank 201 increases. As a result, gas flows from a control chamber of the shut-off valve 213 via its outlet throttle into a gas volume between the shut-off valve 213 and the additional check valve 215. As a result, the pressure in this gas volume equalizes to the pressure in the hydrogen tank 201. Since this pressure is somewhat lower than a pressure on the downstream side of the additional check valve 215 due to a pressure drop at the main check valve 211, the additional check valve 215 always remains closed, and no gas can penetrate the pilot valve 217 of the shut-off valve 213 via the downstream side and thus into the shut-off valve 213 itself. Accordingly, icing of the shut-off valve 213 is prevented when filling the hydrogen tank 201 with hydrogen.

Claims

Claims 1. A refueling method (100) for refueling a hydrogen tank (201), the refueling method (100) comprising: Supplying (101) hydrogen into the hydrogen tank (201) via a refueling path (207) of a tank valve (203) of the hydrogen tank (201), Opening (103) a pilot valve (217) of a shut-off valve (213) arranged in the withdrawal path (209) of the tank valve (203) while a pressure in the hydrogen tank (201) increases.

2. The refueling method (100) according to claim 1, characterized in that the pilot valve (217) is opened such that fluid flows from a first space between the hydrogen tank (201) and the pilot valve (217) into a second space downstream of the pilot valve (217) and upstream of an additional check valve (215) arranged in the withdrawal path (209), such that the fluid minimizes a pressure difference between the second space and a third space, the third space being located between the additional check valve (215) and a main check valve (211) arranged in the withdrawal path (209).

3. Refueling method (100) according to claim 1 or 2, characterized in that the pilot valve (217) is opened for a period of time between 50 milliseconds and 5 seconds, in particular between 100 milliseconds and 500 milliseconds.

4. Refueling method (100) according to one of the preceding claims, characterized in that the pilot valve (217) is repeatedly opened and closed.

5. The refueling method (100) according to any one of the preceding claims, characterized in that the pilot valve (217) is opened in such a way that a main valve (219) of the shut-off valve (213) does not open.

6. The refueling method (100) according to claim 1 or 2, characterized in that the pilot valve (217) is permanently opened during the filling of the hydrogen tank (201) with hydrogen.

7. The refueling method (100) according to any one of the preceding claims, characterized in that the pilot valve (217) is opened at a predetermined time after the start of supplying hydrogen into the hydrogen tank (201).

8. Tank system (200) for storing hydrogen, wherein the tank system (201) comprises: a hydrogen tank (201), a tank valve (203), a computing unit (205), wherein the tank valve (203) comprises a refueling path (207) and a withdrawal path (209), wherein a main check valve (211) is arranged in the refueling path (207), wherein a shut-off valve (213) and an additional check valve (215) are arranged in the withdrawal path (209), wherein the shut-off valve (213) comprises a pilot valve (217) and a main valve (219), and wherein the computing unit (205) is configured to open the pilot valve (217) during a refueling process for filling the hydrogen tank (201) with hydrogen, while a pressure in the hydrogen tank (201) increases.

9. Tank system (200) according to claim 8, characterized in that that the computing unit (205) is configured to open the pilot valve (217) according to one of claims 2 to 7.

10. Tank system (200) according to claim 8 or 9, characterized in that the computing unit (205) is configured to enable a closing movement of the pilot valve (217) as soon as the filling of the hydrogen tank (201) with hydrogen is completed.

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