CONSTANT-PRESSURE STORAGE UNIT

Abstract

A constant-pressure storage unit and a method for operating a constant-pressure storage unit, for storing and dispensing hydrogen under constant pressure are disclosed. The constant-pressure storage unit has at least one constant-pressure store, which is divided into two regions by a movable separating piston, at least one liquid pump for conveying a liquid, and at least one liquid store, wherein a measuring device measures the liquid level in the liquid store and sends a signal to the liquid pump by means of a control unit. In this way, the liquid pump can be stopped in time when the constant-pressure storage unit is empty.

Claims

1. A method for operating a constant-pressure storage unit for storing and dispensing hydrogen under constant pressure, wherein said constant-pressure storage unit comprises at least one constant-pressure store, which is divided into two regions by a movable separating piston, at least one liquid pump for conveying a liquid and at least one liquid store, characterized in that a measuring device measures a liquid level in the liquid store and delivers a signal to the liquid pump by a control unit.

2. The method according to claim 1, characterized in that the liquid supply or liquid discharge into or from the at least one constant-pressure store is stopped when the measuring device measures a minimum or maximum liquid level in the liquid store.

3. The method according to claim 1, characterized in that the constant-pressure storage unit uses fluids selected from the group consisting of hardly inflammable hydraulic fluids comprising water and polyglycol, and hydraulic fluids comprising mineral oil as liquid in the second region.

4. The method according to claim 1, characterized in that the hydrogen in the first region is stored at a pressure of 235 to 5000 bar.

5. The method according to claim 1, characterized in that the measuring device used consists of a filling level sensor.

6. A constant-pressure storage unit for storing a gas under constant pressure, comprising at least one constant-pressure store, which is divided into two regions by a movable separating piston, at least one liquid pump for conveying a liquid and at least one liquid store, characterized in that the liquid store contains a measuring device, which serves for determining the level of the liquid and is connected to the liquid pump by a control unit.

7. The constant-pressure storage unit according to claim 6, characterized in that multiple constant-pressure stores are connected to a liquid pump and only one liquid store.

8. The constant-pressure storage unit according to claim 6, characterized in that the measuring device for determining the level of the liquid is selected from the group consisting of a level sensor, which detects the changes in the filling level of the liquid store, a pressure sensor and a position measuring system with floats.

9. The constant-pressure storage unit according to claim 6, characterized in that the constant-pressure storage unit stores is a gas in the form of hydrogen.

10. The constant-pressure storage unit according to claim 6, characterized in that the constant-pressure storage unit is at a pressure of 235 to 5000 bar.

11. The constant-pressure storage unit according to claim 8, characterized in that the level sensor is an ultrasonic sensor.

12. The constant-pressure storage unit according to claim 10, characterized in that the constant-pressure unit is at a pressure of 301 to 1200 bar.

13. The constant-pressure storage unit according to claim 10, characterized in that the constant-pressure unit is at a pressure selected from the group consisting of 620, 850, 900 and 1000 bar.

Description

[0022] An exemplary embodiment of the invention is described below with reference to a schematic figure. Valves, control and sensor units, which a person skilled in the art would usually provide for the operation of the system, are not illustrated in order to provide a better overview.

[0023] FIG. 1 schematically shows the configuration of a constant-pressure storage unit.

[0024] FIG. 1 shows a potential design variation of a constant-pressure storage unit. This constant-pressure storage unit comprises a liquid store 4, in which a liquid 1, in this case a hardly inflammable hydraulic fluid, is stored. The liquid store 4 also contains a measuring device 2, which is particularly realized in the form of an ultrasonic sensor or ultrasonic level sensor, in order to detect the quantity of liquid 1 remaining in the liquid store 4. The liquid store 4 furthermore comprises a safety valve 3, which may be realized in the form of a bursting disk, an overflow valve or other pressure relief devices familiar to a person skilled in the art. The measuring device 2 is connected to a control unit 5 and a liquid pump 9 by means of electrical connections 6 and 7. The liquid pump 9 for conveying the liquid 1 is furthermore connected to the liquid store 4 by means of the liquid line 8.

[0025] The liquid 1 is stored in the liquid store 4 with the ambient temperature, i.e. in a range between 40 C. and +80 C., and a pressure of 301 to 1200 bar. The liquid 1 is conveyed into the constant-pressure stores A to D by means of the liquid pump 9 and the liquid line 10 (or 10A, 10B, 10C, 10D) in order to move the separating piston 11 (A to D) therein and to thereby keep the pressure of the gas, in this example hydrogen 12 (12A and 12C), constant.

[0026] In the exemplary embodiment shown, all constant-pressure stores share a liquid store 4 for the liquid 1. The gas, particularly hydrogen 12, is injected and withdrawn into: from the constant-pressure stores by means of the transport line 13 (or 13A, 13B, 13C, 13D) and the shutoff valve 14. The pressure of the hydrogen 12 lies between 301 and 1200 bar.

[0027] In the injection phase, the constant-pressure stores A to D are filled with the gas, i.e. with hydrogen 12, by means of the transport lines 13. During this process, the separating pistons 11A, 11B, 11C, 11D are displaced in such a way that the region for the liquid 1 is minimal and the region for the hydrogen 12 is maximal. The liquid 1 is stored in the liquid store 4.

[0028] In the withdrawal phase, hydrogen is dispensed from the constant-pressure storage unit. In this case, liquid 1 is conveyed from the liquid store 4 into the constant-pressure stores A, B, C and/or D by means of the liquid line 8, the liquid pump 9 and the transport lines 10 (or 10A, 10B, 10C, 10D). In this case, the separating pistons 11A, 11B, 11C and/or 11D are displaced in such a way such that the region for the liquid 1 is maximal and the region for the hydrogen 12 is minimal. In the exemplary embodiment shown, the liquid level in the liquid store 4 is measured by means of a measuring device 2, namely an ultrasonic sensor. Once the liquid level reaches a minimum value, the liquid pump 9 is stopped by means of the control unit 5 and the electrical connections 7 and 6. At this point, the separating pistons 11A, 11B, 11C and 11D have reached their end position within the constant-pressure stores A, B, C, D, in which the constant-pressure stores are filled with a maximum quantity of liquid 1 (1A, 1B, 1C, 1D) and the gas has been completely or almost completely dispensed. A pressure peak within the constant-pressure stores can be prevented by stopping the liquid pump 9, i.e. the liquid supply.

[0029] In other embodiments, different measuring principles and different measuring devices may be used for stopping the liquid supply.

LIST OF REFERENCE SYMBOLS

[0030] 1 Liquid in liquid store [0031] 1A, 1B, 1C, 1D Liquid in constant-pressure store [0032] 2 Measuring device [0033] 3 Safety valve [0034] 4 Liquid store [0035] 5 Control unit [0036] 6, 7 Electrical connection [0037] 8 Liquid line [0038] 9 Liquid pump [0039] 10, 10A, 10B, 10C, 10D Liquid line [0040] 11A, 11B, 11C, 11D Separating piston in constant-pressure store [0041] 12A, 12C Gas in constant-pressure store [0042] 13, 13A, 13B, 13C, 13D Transport line for gas [0043] 14 Shutoff valve [0044] A, B, C, D Constant-pressure store