FUEL CELL DEVICE AND METHOD FOR COOLING A FUEL CELL SYSTEM

Abstract

A fuel cell device for a vehicle has a fuel cell system comprising a fuel cell stack and has a first cooling circuit for cooling the fuel cell system and a second cooling circuit for cooling an electronic unit and/or an energy storage. The first cooling circuit and the second cooling circuit are thermally connected to each other, wherein only the second cooling circuit has a cooler for cooling the cooling water flowing in the second cooling circuit. A method for cooling a fuel cell device using such components is also provided.

Claims

1. A fuel cell device for a vehicle including a fuel cell system, comprising: a fuel cell stack; a first cooling circuit for cooling the fuel cell system; and a second cooling circuit for cooling an electronic unit and/or an energy storage, wherein the first cooling circuit and the second cooling circuit are thermally connected to one another, wherein the second cooling circuit has a cooler for cooling a cooling water flowing in the second cooling circuit, wherein the first cooling circuit is cooler-free, and wherein the first cooling circuit consists of the fuel cell stack, a heat exchanger, and a pump.

2. The fuel cell device according to claim 1, wherein the first cooling circuit and the second cooling circuit are thermally connected by a heat exchanger for transferring waste heat produced in the first cooling circuit through the fuel cell system to the second cooling circuit at a first temperature level.

3. The fuel cell device according to claim 2, wherein the heat exchanger is a water-water heat exchanger.

4. The fuel cell device according to claim 2, wherein an air conditioning circuit thermally connected to the second cooling circuit by a second heat exchanger is provided for transferring waste heat produced in the first cooling circuit and in the second cooling circuit to the air conditioning circuit at a second temperature level that is increased with respect to the first temperature level.

5. The fuel cell device according to claim 4, wherein the air conditioning circuit has a third heat exchanger for increasing the temperature of a vehicle interior.

6. The fuel cell device according to claim 1, wherein the second cooling circuit comprises several subcircuits, the subcircuits are flow-connected to one another at an opening point, and the mass flow of the cooling water in the subcircuits can be regulated by an actuator arranged at the opening point or coupled into it.

7. The fuel cell device according to claim 6, wherein the subcircuits comprise a cooler circuit, and a drive circuit leading to the electronic unit and/or to the energy storage.

8. The fuel cell device according to claim 7, wherein the drive circuit comprises several sub-circuits flow-connected to one another, and the sub-circuits are formed as an energy storage circuit for cooling the energy storage and as an electronic unit circuit for cooling the electronic unit, as well as a connection circuit connecting the energy storage circuit and the electronic unit circuit to one another in flow connection.

9. A method for cooling a fuel cell device in a vehicle including a fuel cell system, the fuel ceil device including a fuel cell stack, a first cooling circuit for cooling the fuel cell system, and a second cooling circuit for cooling an electronic unit and/or an energy storage, wherein the first cooling circuit and the second cooling circuit are thermally connected to one another, wherein the second cooling circuit has a cooler for cooling a cooling water flowing in the second cooling circuit, and wherein the first cooling circuit is cooler-free, the method comprising: transferring waste heat produced in the fuel cell system from the first cooling circuit to the second cooling circuit by a first heat exchanger at a first temperature level and thereby heating a coolant circulating in the second cooling circuit.

10. The method according to claim 9, further comprising: transferring heat generated by the electronic unit and/or by the energy storage, as well as by the heat transfer from the first fuel cell system from the second cooling circuit to an air conditioning circuit at a second temperature level higher with respect to the first temperature level and thereby heating a refrigerant circulating in the air conditioning circuit; and transferring heat from the heated refrigerant to air located in a vehicle interior by a second heat exchanger and thereby raising a temperature in the vehicle interior.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0021] Further advantages, features and details are provided in the claims, the following description and the drawing.

[0022] FIG. 1 illustrates a schematic representation of the fuel cell device with the first cooling circuit, the second cooling circuit, and the air conditioning circuit.

DETAILED DESCRIPTION

[0023] FIG. 1 shows a fuel cell device 1 for a vehicle with a fuel cell system 2 having a fuel cell stack and with a first cooling circuit 3 for cooling the fuel cell system 2, as well as with a second cooling circuit 4 for cooling an electronic unit 5 and/or an energy storage 6, wherein the first cooling circuit 3 and the second cooling circuit 4 are thermally connected to one another. In doing so, only the second cooling circuit 4 has a cooler 7 for cooling cooling water flowing in the second cooling circuit 4. In contrast, the first cooling circuit 3 is formed cooler-free, i.e., a separate cooler in the first cooling circuit 3 is foregone.

[0024] The first cooling circuit 3 and the second cooling circuit 4 are thermally connected by means of a heat exchanger 8, which is formed as a water-water heat exchanger. By means of the heat exchanger 8, the waste heat produced in the first cooling circuit 3 by the fuel cell system 2 can be transferred to the second cooling circuit 4 at a first temperature level. The cooling water circulating in the first cooling circuit 3 is thereby conveyed by a pump 22. By forming the heat exchanger 8 as a water-water heat exchanger, the entry of ions in the first cooling circuit 3 is reduced by omitting a water-air front-end cooler normally used, as a water-water heat exchanger has a significantly smaller surface in contact with the coolant.

[0025] The second cooling circuit 4 comprises several subcircuits 12. In the present embodiment, the subcircuits 12 are formed as a cooling circuit 13, in which the coolant is guided from the cooler 7 and to the cooler 7, thus circulates around the cooler 7, and is formed as a drive circuit 14 leading to the electronic unit 5 and the energy storage 6. The two subcircuits 12 thereby open into one another at an opening point 20, wherein an actuator 19 is arranged at the opening point 20 or is coupled into it. Thus, the mass flow of the cooling water in the respective subcircuits 12 and thereby the cooling of the energy storage 6 and the electronic unit 5 can be regulated. The actuator 19 is thereby formed as a multivalve, so that exactly one actuator 19 formed as a multivalve is sufficient for regulating the mass flows in the subcircuits 12, while foregoing further actuators in the subcircuits 12.

[0026] The drive circuit 14 thereby comprises several sub-circuits 15 that are flow-connected to one another. The sub-circuits 15 are thereby formed as an energy storage circuit 17 for cooling the energy storage 6 and as an electronic unit circuit 16 for cooling the electronic unit 6, as well as a connection circuit 18 connecting the energy storage circuit 17 and the electronic unit circuit 16 to one another in flow connection. By means of this arrangement of subcircuits and sub-circuits, the fuel cell device, in particular the first cooling circuit 3, can be retrofitted or converted easily. In the present embodiment, the heat exchanger 8 thermally connects the first cooling circuit 3 to the electronic unit circuit 16. The actuator 19 is arranged at the opening point 20 between the second cooling circuit 4 and the connection circuit 18. Downstream of the heat exchanger 8, the electronic unit circuit 16 is connected to the cooler circuit 13 in a flow-mechanical manner.

[0027] Furthermore, an air conditioning circuit 10 thermally connected to the second cooling circuit 4 by means of a second heat exchanger 9 is provided for transferring the waste heat produced in the first cooling circuit 3 and in the second cooling circuit 4 to the air conditioning circuit 10 at a second temperature level that is increased with respect to the first temperature level. In the present embodiment, the second heat exchanger 9 is formed as a chiller which thermally connects the energy storage circuit 17 to the air conditioning circuit 10. In the present embodiment, the air conditioning circuit 10 is also cooler-free, i.e., formed without a further cooler 7. The air conditioning circuit 10 also comprises a compressor 24, an evaporator not shown in detail, expansion valves and a condenser. To control the mass flow in the air conditioning circuit 10, a second actuator 21 is also provided, which may be formed as a controllable throttle valve.

[0028] The energy storage circuit 17 furthermore comprises a pump 22 arranged or coupled downstream of the second heat exchanger 9 for conveying the coolant within the energy storage circuit 17. In addition, a check valve 23 is arranged in the energy storage circuit 17 downstream of the pump 22 or is coupled into it in order to prevent a backflow of the coolant.

[0029] In the present embodiment, two electronic units 5 are provided, which are connected in parallel in the second cooling circuit 4, more precisely in the electronic unit circuit 16 of the drive circuit 14.

[0030] The method for cooling the fuel cell device thereby comprises the following steps: Initially, the waste heat produced in the fuel cell system 2 from the first cooling circuit 3 is transferred to the second cooling circuit 4 by means of the heat exchanger 8 at a first temperature level and thereby the coolant circulating in the second cooling circuit 4 is heated. The heat is thereby withdrawn from the coolant in the first cooling circuit 3 and this is cooled thereby. Furthermore, the coolant already heated by the fuel cell system 2 is further heated by the waste heat produced by the electronic units 5 and the energy storage 6. By means of the second heat exchanger 9, the heat generated by the electronic units 5 and the energy storage 6 and by the heat transfer from the first fuel cell system 2 is transferred from the second cooling circuit 4 to the air conditioning circuit 10 at a second temperature level higher compared to first temperature level. As a result, the refrigerant circulating in the air conditioning circuit 10 is heated in that the heat is withdrawn from the coolant of the second cooling circuit 4 and the coolant in the second cooling circuit 4 is cooled thereby. The heated refrigerant of the air conditioning circuit 10 is in turn used to transfer heat by means of the third heat exchanger 11 to air located in the vehicle interior, so that the temperature in the vehicle interior is raised from a first temperature value to a second temperature value that is increased with respect to the first temperature value. Consequently, heating of the vehicle interior takes place only by the waste heat generated by the fuel cell system, the electronic unit, and the energy storage and does not require any additional electrical heating.

[0031] In doing so, the advantage of the present fuel cell device 1 and the corresponding method is that the first cooling circuit 3 for cooling the fuel cell system 2 can be designed very small and only includes the heat exchanger 8 and the pump 22. An additional cooler 7 can be foregone, so that the installation space to be provided for the fuel cell device 1 can be reduced. By means of the thermal connection of the air conditioning circuit 10 to the second cooling circuit 4, heat transfer can take place from the second cooling circuit 4 to the air conditioning circuit 10 at a comparatively high temperature level. In contrast to the prior art, not only the waste heat generated by the fuel cell system 2, but also the waste heat generated by the energy storage 6 and the electronic units 5 is transferred to the air conditioning circuit 10 by means of the second heat exchanger 9. Additional electrical heating can be dispensed with, as the heat transfer takes place at a significantly higher temperature level compared to the prior art. At the same time, due to the improved dissipation of the waste heat generated by the fuel cell system 2, by the electronic units 5 and by the energy storage 6, it is better possible to cool the corresponding components. In that the air conditioning circuit 10 is thermally connected to the second cooling circuit 4 and not to the first cooling circuit 3, the first cooling circuit can be designed much smaller. An otherwise usual heating heat exchanger in the first cooling circuit 3 can be foregone. Due to the omission of a further cooler 7 in the first cooling circuit 3, the entry of ions into the coolant is also reduced, as the water-water heat exchanger is much smaller and therefore has a smaller surface in contact with the coolant than the water-air front-end cooler usually built into the first cooling circuit 3.

[0032] In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled.