Unlocking a fuel cell

Abstract

Fuel cell system (1) comprising at least one fuel cell (10) having a fuel supply line (11) with a valve (12) controlled via a signal line (13), and a short-circuit line (15) arranged between the positive terminal and the negative terminal of the fuel cell (10), wherein both the signal line (13) and the short-circuit line (15) have open circuits which can be bridged by a short-circuit bridge (14, 14'), wherein a single short-circuit bridge (14, 14') alternately bridges the open circuit in the signal line (13) or the short-circuit line (15).

Description

[0001] The invention relates to a device and a method for unlocking a fuel cell, enabling safe work on the fuel cell during a service or repair operation.

[0002] In order to work on a fuel cell, for example as part of a service or repair procedure, it must be deactivated according to the five safety rules of electrical engineering: 1. Unlock; 2. Secure against accidental reactivation; 3. Verify absence of tension; 4. Ground and short-circuit; 5. Cover or barricade adjacent live parts.

[0003] If step 4 (the short-circuit bridge) is omitted or not carried out correctly, and the system is still supplied with hydrogen, there is a risk of fire. Furthermore, the complete destruction of the fuel cell system is imminent.

[0004] The object of the present invention was therefore to provide a fuel cell system which prevents the risk of fire during a service or repair operation of a fuel cell and ensures safe work on the fuel cell.

[0005] Measures already exist to isolate individual defective fuel cells from a fuel cell stack in order to continue operating the fuel cell system. Fuel cell systems with automatic shutdown in case of overheating have also been proposed.

[0006] From EP 1 517 393 A2, a device and method for assembling a solid-state fuel cell are known. If a defective fuel cell is detected during operation, the individual fuel cell is separated from a group of several fuel cells by a short-circuit bridge. The outer surface of the short-circuit bridge also interrupts the fuel or air supply to the cell.

[0007] US 7 358 005 B2 discloses a device and a method for isolating individual fuel cells in a fuel cell stack, wherein interrupters are arranged in the fuel supply and fuel outlet of the fuel cells, which can be moved by means of an actuator to disconnect individual fuel cells from a fuel supply.

[0008] DE 101 27 600 A1 discloses a method for generating electrical energy using a fuel cell system. If an overtemperature is detected in the fuel cell block, a temperature switch, connected in series with a main switch, shuts down the fuel cell system by interrupting the supply of hydrogen and air to the fuel cell block. A switch can also be used to interrupt the connection between the positive terminal and a control device. This switch is specifically coupled to the main switch, so that the power supply to the control device can be switched on and off by the main switch.

[0009] In JP 2011-228076A, a fuel cell system is described in which the fuel cell stack has a short-circuit line that can be closed mechanically or electrically for servicing the fuel cell. The invention is specified in the independent claims. Advantageous embodiments are specified in the dependent claims.

[0010] The invention relates to a fuel cell system comprising at least one fuel cell. The fuel cell has a fuel supply line through which a fuel, for example hydrogen, can be supplied to the fuel cell. A valve controlled by a signal line is arranged in the fuel supply line. In the open state, the valve allows the flow of fuel to the fuel cell; in the closed state, it blocks this flow. The fuel cell has a short-circuit line arranged between the positive and negative terminals of the fuel cell, with which the terminals of the cell can be short-circuited. Both the signal line and the short-circuit line have breaks that can be bridged by a short-circuiting bridge.

[0011] In one embodiment, the breaks in the signal line and the short-circuit line are configured such that only one of them can be closed at any given time. In one embodiment, this is achieved by having only a single short-circuit bridge that alternately bridges the break in either the signal line or the short-circuit line. In one embodiment, the short-circuit bridge is designed to be manually inserted into or removed from either the signal line or the short-circuit line.

[0012] In another embodiment, the short-circuit bridge is mechanically coded so that it can only be inserted into the signal line or the short-circuit line of a fuel cell with the corresponding code. The codes of the individual fuel cells in the fuel cell system differ from one another, so that a short-circuit bridge cannot be accidentally inserted into a fuel cell other than the one to which it belongs.

[0013] In another embodiment, the interruption in the signal line and the interruption in the short-circuit line are coupled such that closing one interruption triggers the opening of the other. If the interruption in the signal line is closed, the short-circuit line is opened; if the interruption in the short-circuit line is closed, thus short-circuiting the fuel cell, the signal line is opened, and the fuel supply to the fuel cell is stopped. In one embodiment, the opening and closing of the interruptions is accomplished by means of a changeover relay. Both the signal line and the short-circuit line are connected to the relay and are alternately opened and closed by the relay.

[0014] In the operating state, the break in the signal line is bridged by a short-circuit jumper or signal jumper, so that the valve is open; the break in the short-circuit line is unblocked. If the signal line is interrupted, the valve closes and interrupts the fuel flow to the fuel cell.

[0015] A characteristic feature of the present invention is the coupling of the short-circuit bridge for short-circuiting the poles of the fuel cell with the blocking of the shut-off valve for the fuel supply line. The short-circuit bridge also serves as a signal bridge for the shut-off valve; that is, when the bridge is used for short-circuiting, the signal line for the shut-off valve is interrupted.

[0016] The invention also relates to a method for the maintenance or repair of a fuel cell of a fuel cell system according to the invention. At the beginning of a maintenance or repair process on a fuel cell, the signal line to a valve in the fuel supply line of the fuel cell is interrupted and a break in a short-circuit line arranged between the positive and negative terminals of the fuel cell is closed.

[0017] Then the maintenance or repair process can be carried out safely, as the fuel cell is unlocked and the fuel supply is interrupted.

[0018] After the maintenance or repair procedure on the fuel cell has been carried out, the short-circuit line is interrupted again and the break in the signal line is closed. The fuel cell is then ready for operation again.

[0019] In one embodiment of the method, the interruption of the signal line and the closing of the break in the short-circuit line, or the interruption of the short-circuit line and the closing of the break in the signal line, are achieved by moving a single short-circuit bridge that can bridge both the break in the signal line and the break in the short-circuit line. Moving the bridge from the signal line to the short-circuit line disconnects the fuel cell and interrupts the fuel supply; moving it from the short-circuit line to the signal line opens the fuel supply shut-off valve and makes the fuel cell operational again.

[0020] The advantages of the present invention include the effective prevention of fire hazards and damage to the fuel cell system, as well as ensuring safe working on the system's fuel cells. Furthermore, it simplifies repair and maintenance procedures on a fuel cell. Additional advantages will become apparent from the description and the drawing.

[0021] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0022] One embodiment of the invention is schematically illustrated in the drawing and is further described with reference to the drawing. It shows: Fig. 1 a schematic representation of an embodiment of the fuel cell system according to the invention.

[0023] Fig. Figure 1 shows an embodiment of the fuel cell system 1 according to the invention, comprising a fuel cell 10. The fuel cell 10 is supplied with hydrogen via a fuel supply line 11. The hydrogen line 11 contains an electric valve 12, which is controlled via a signal line 13. A signal bridge 14 is arranged in the signal line 13. If the short-circuit bridge 14 is removed, the valve 12 closes and interrupts the flow of hydrogen through line 11. The short-circuit bridge 14 is then inserted into the short-circuit line 15, which is arranged between the positive and negative terminals of the fuel cell 10, as a short-circuit bridge 14' and shorts the terminals of the fuel cell 10.

[0024] This enables fuel cell 10 for a repair or service procedure. After completion of the repair or service procedure, the short-circuit bridge 14' is removed from the short-circuit line 15 and reinserted as signal bridge 14 into the signal line 13 of valve 12. The position changes are indicated by arrows in the figure. Reference symbol list 1 Fuel cell system 10 Fuel cell 11 Hydrogen supply line 12 Shut-off valve 13 Signal line 14 Signal bridge 14' Short-circuit bridge 15 Short-circuit line

Claims

[1] Fuel cell system (1) comprising at least one fuel cell (10) having a fuel supply line (11) with a valve (12) controlled via a signal line (13), and a short-circuit line (15) arranged between the positive terminal and the negative terminal of the fuel cell (10), wherein both the signal line (13) and the short-circuit line (15) have open circuits which can be bridged by a short-circuit bridge (14, 14'), wherein a single short-circuit bridge (14, 14') alternately bridges the open circuit in the signal line (13) or the short-circuit line (15). [2] Fuel cell system (1) according to claim 1, wherein a short-circuit bridge (14, 14') is provided to be manually inserted into or removed from the signal line (13) or the short-circuit line (15). [3] Fuel cell system (1) according to claim 1, wherein the interruption in the signal line (13) and the interruption in the short-circuit line (15) are coupled such that closing one interruption triggers the opening of the other interruption. [4] Fuel cell system (1) according to claim 3, wherein the opening and closing of the interruptions is carried out by means of a switching relay. [5] Fuel cell system (1) comprising at least one fuel cell (10) having a fuel supply line (11) with a valve (12) controlled via a signal line (13), and a short-circuit line (15) arranged between the positive terminal and the negative terminal of the fuel cell (10), wherein both the signal line (13) and the short-circuit line (15) have breaks which can be bridged by a short-circuit bridge (14, 14'), wherein each short-circuit bridge (14, 14') is mechanically coded so that it can only be inserted into the signal line (13) or the short-circuit line (15) of a fuel cell (10) with the corresponding coding. [6] Fuel cell system (1) according to claim 5, wherein a short-circuit bridge (14, 14') is provided to be manually inserted into or removed from the signal line (13) or the short-circuit line (15). [7] Fuel cell system (1) according to claim 5, wherein the interruption in the signal line (13) and the interruption in the short-circuit line (15) are coupled such that closing one interruption triggers the opening of the other interruption. [8] A method for servicing or repairing a fuel cell (10) of a fuel cell system (1) according to one of the preceding claims, comprising interrupting a signal line (13) to a valve (12) in a fuel supply line (11) of the fuel cell (10) and closing an interruption in a short-circuit line (15) arranged between the positive terminal and the negative terminal of the fuel cell (10) by repositioning a short-circuit bridge (14, 14'). [9] Method according to claim 8, further comprising interrupting the short-circuit line (15) and closing the break in the signal line (13) after performing the maintenance or repair procedure on the fuel cell (10) by reconnecting a short-circuit bridge (14, 14').

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