Electrochemical energy conversion device and method for operating such an electrochemical energy conversion device

Abstract

Electrochemical energy conversion device (1), with - at least one galvanic cell (3) designed to convert chemical energy into electrical energy, - a fuel supply path (7) which is arranged to supply a fuel to the at least one galvanic cell (3), - an oxidizing agent path (9) which is designed to supply the at least one galvanic cell (3) with an oxidizing agent for electrochemical conversion with the fuel, and with - an electric power bus (37), wherein - a first oxidant compressor (11) is arranged along the oxidant path (9) in order to compress the oxidant flowing along the oxidant path (9), wherein - a cooling device (13) is arranged downstream of the first oxidant compressor (11) along the oxidant path (9) in order to cool the compressed oxidant, and wherein - an oxidant turbine (15) is arranged downstream of the cooling device (13) along the oxidant path (9) in order to expand the compressed, cooled oxidant, wherein - the oxidizer turbine (15) is drive-connected to a first electric machine (17), wherein - the first oxidant compressor (11) is drive-connected to a second electric machine (27), wherein - the exhaust gas turbine (23) is operatively connected to a third electric machine (35), wherein - the first electrical machine (17), the second electrical machine (27) and the third electrical machine (35) are each electrically connected to the electrical power bus (37) and thus also - via the electrical power bus - to one another.

Description

[0001] The invention relates to an electrochemical energy conversion device and a method for operating such an electrochemical energy conversion device.

[0002] In such an electrochemical energy conversion device, a fuel and an oxidizing agent, in particular a gaseous one, are supplied to at least one galvanic cell for electrochemical conversion with the fuel in the galvanic cell. The performance of the electrochemical energy conversion device depends in particular on the density of the oxidizing agent present at the galvanic cell and thus, in particular, on the oxidizing agent pressure. To achieve higher performance, the oxidizing agent is therefore generally compressed. However, this reaches its limits where a further increase in pressure could lead to mechanical damage to the galvanic cell. To be able to further increase the density of the oxidizing agent, it can be cooled, especially after compression.This proves problematic because, on the one hand, the temperature of the oxidizing agent is low, while, on the other hand, only a small temperature difference to the existing cooling medium is available for cooling the oxidizing agent. Extensive heat transfer surfaces and thus large cooling devices are required to ensure sufficient cooling. Accordingly, electrochemical energy conversion devices are space-intensive and expensive.

[0003] DE 10 2014 215 480 A1 discloses an electrochemical energy conversion device having at least one galvanic cell configured to convert chemical energy into electrical energy. The electrochemical energy conversion device has a fuel supply path configured to supply a fuel to the at least one galvanic cell. The electrochemical energy conversion device also has an oxidant path configured to supply an oxidant to the at least one galvanic cell for electrochemical reaction with the fuel. An oxidant compressor is arranged along the oxidant path to compress the oxidant flowing along the oxidant path. A heat exchanger is arranged downstream of the oxidant compressor along the oxidant path.Downstream of the heat exchanger along the oxidant path, an oxidant turbine is arranged to expand the oxidant. Further electrochemical energy conversion devices are also known from DE 690 25 496 T2, JP 2005-203 223 A, US 5 811 201 A, DE 10 2015 221 597 A1, and DE 10 2018 214 455 A1.

[0004] The invention is based on the object of creating an electrochemical energy conversion device and a method for operating such an electrochemical energy conversion device, wherein the aforementioned disadvantages are at least reduced, preferably avoided.

[0005] The object is achieved by providing an electrochemical energy conversion device having the features of claim 1 and a method having the features of claim 7. Advantageous embodiments emerge from the dependent claims.

[0006] The electrochemical energy conversion device has at least one galvanic cell configured to convert chemical energy into electrical energy. The electrochemical energy conversion device also has a fuel supply path configured to supply a fuel to the at least one galvanic cell. The electrochemical energy conversion device also has an oxidant path configured to supply an oxidant to the at least one galvanic cell for electrochemical reaction with the fuel. A first oxidant compressor is arranged along the oxidant path to compress the oxidant flowing along the oxidant path. Downstream of the first oxidant compressor along the oxidant path, a cooling device is arranged to cool the compressed oxidant.Downstream of the cooling device along the oxidant path, an oxidant turbine is arranged to expand the compressed, cooled oxidant. In particular, the oxidant turbine is driven by the oxidant. As the oxidant is expanded above the oxidant turbine, it is further cooled so that the temperature ultimately reached by the oxidant is lower than the temperature downstream of the cooling device, but before expansion in the oxidant turbine. Accordingly, the density of the oxidant downstream of the oxidant turbine is higher than upstream of it, whereby in particular a higher density can be achieved than without the use of the oxidant turbine. At the same time, there is no need to increase the oxidant pressure to a value that could potentially be dangerous for the galvanic cell.Compared to an electrochemical energy conversion device that only has the first oxidant compressor and the cooling device, but not the oxidant turbine, the electrochemical energy conversion device proposed here advantageously achieves, in particular, a comparable or identical pressure level at a lower oxidant temperature at the galvanic cell, thus resulting in a higher oxidant density and, at the same time, a higher performance of the electrochemical energy conversion device. However, for this purpose, the oxidant must first be compressed to a higher pressure level in the first oxidant compressor, since it is later expanded again via the oxidant turbine.However, this also advantageously results in an increase in the temperature of the oxidant downstream of the first oxidant compressor and upstream of the cooling device, resulting in a higher temperature difference to the cooling medium, making heat transfer more efficient. This, in turn, allows for a smaller cooling device, thus saving space and costs.

[0007] In a preferred embodiment, the electrochemical energy conversion device is designed as a fuel cell, in particular as a hydrogen-oxygen fuel cell. The at least one galvanic cell is configured, in particular, to electrochemically convert hydrogen as fuel and oxygen or air as oxidizing agent into water and thereby generate electrical power. The oxidizing agent path is preferably an air path or charging path, in particular for supplying ambient air to the at least one galvanic cell.

[0008] Alternatively, the electrochemical energy conversion device is preferably configured to use methane, methanol, butane, butanol, in particular a mixture of at least one of the fuels specifically mentioned above and at least one accompanying substance, in particular natural gas, a mixture of at least two of the fuels specifically mentioned above, or another suitable substance or mixture of substances as the fuel. The oxidizing agent is generally preferably oxygen or an oxygen-containing gas, in particular air.

[0009] In a preferred embodiment, the electrochemical energy conversion device comprises a plurality of galvanic cells, in particular in the form of a so-called cell stack or stack.

[0010] The oxidant turbine is preferably adjustable with respect to a flow resistance for the oxidant. In particular, a minimum flow resistance for the oxidant turbine can preferably be set. In a preferred embodiment, the oxidant turbine has an idle function, or an idle function is assigned to the oxidant turbine. In particular, in the idle function, the oxidant turbine runs load-free or—except for unavoidable friction losses—unbraked. Alternatively or additionally, it is possible for the oxidant turbine to be assigned a turbine bypass path, also referred to as a bypass, which can be blocked or opened as required. By opening the turbine bypass path, flow resistance in the region of the oxidant turbine can be minimized.Preferably, a flow cross-section through the turbine bypass path is adjustable, in particular discretely or continuously adjustable between a blocking state and a release state, so that the flow resistance for the oxidant in the region of the oxidant turbine can be adjusted by varying the flow cross-section of the turbine bypass path.

[0011] According to a further development of the invention, the cooling device is designed as a heat exchanger. A heat exchanger is understood to be a device in which thermal energy is transferred from a first material stream to a second material stream. The first material stream is the oxidizing agent, and the second material stream is also referred to as the cooling medium. In a preferred embodiment, an exhaust gas from the galvanic cell is used as the second material stream or cooling medium, with the term exhaust gas being used in particular to mean a product gas which results from the electrochemical reaction in the galvanic cell and is discharged from the galvanic cell. If the electrochemical energy conversion device is designed as a hydrogen-oxygen fuel cell, the product gas is in particular gaseous water, and the exhaust gas is in particular air containing water vapor.The heat exchanger is preferably arranged along an exhaust gas flow or exhaust gas path of the electrochemical energy conversion device upstream of an exhaust gas turbine. By absorbing thermal energy from the oxidant in the heat exchanger, the exhaust gas can advantageously be supplied with increased enthalpy to the exhaust gas turbine.

[0012] In a preferred embodiment, the cooling device is designed as an indirect heat exchanger. An indirect heat exchanger is understood to be a heat exchanger in which the first material stream and the second material stream are spatially separated, with the first material stream being separated from the second material stream, in particular by a heat-permeable wall. The cooling device is preferably designed as a recuperator.

[0013] According to the invention, the oxidant turbine is drive-connected to a first electrical machine. The first electrical machine can be operated, in particular, as a generator. By means of the first electrical machine, the enthalpy of the oxidant can advantageously be converted into electrical energy. At the same time, it is easily possible to influence the flow resistance of the oxidant turbine by controlling the first electrical machine, in particular by introducing an adjustable braking torque into the oxidant turbine. The idling function can be provided for the oxidant turbine by relieving the load on the first electrical machine, i.e., by operating it in load-free operation. Electrical energy generated by the first electrical machine can advantageously be used to supply current to another electrical machine, operated as a motor, of the electrochemical energy conversion device.

[0014] According to a further development of the invention, in addition to the electrical connection according to the invention described below, the oxidant turbine is drive-connected to the first oxidant compressor—in particular mechanically, in particular via a shaft or a gear. In this way, the enthalpy of the oxidant obtained in the oxidant turbine can be advantageously used to at least support or drive the first oxidant compressor. It is possible for the first oxidant compressor to be additionally driven by a second electric machine and / or an exhaust gas turbine.

[0015] Alternatively, it is preferably provided that the oxidant turbine is drive-connected to a second oxidant compressor—in particular mechanically, in particular via a shaft or a gear, or electrically. In this way, the enthalpy of the oxidant obtained in the oxidant turbine can be advantageously used to at least support or drive the second and thus a further oxidant compressor. It is possible for the second oxidant compressor to be additionally driven by another electric machine. In a preferred embodiment, however, the second oxidant compressor is driven solely by the oxidant turbine.

[0016] The second oxidant compressor is preferably arranged along the oxidant path upstream of the cooling device. With the assistance of the second oxidant compressor, the oxidant is preferably compressed to a higher pressure and temperature level than is possible with the first oxidant compressor alone, or the first oxidant compressor can be designed smaller than if the second oxidant compressor were not present.

[0017] The second oxidant compressor is preferably arranged downstream of the first oxidant compressor along the oxidant path. Thus, the oxidant compressed by the first oxidant compressor is advantageously further compressed by the second oxidant compressor.

[0018] Alternatively, the second oxidant compressor is preferably arranged upstream of the first oxidant compressor. Thus, the oxidant is preferably pre-compressed by the second oxidant compressor before being further compressed in the first oxidant compressor.

[0019] According to a further development of the invention, the electrochemical energy conversion device has an exhaust gas path along which the exhaust gas from the at least one galvanic cell can be discharged. The oxidant turbine is preferably connected to an exhaust gas compressor arranged along the exhaust gas path—in particular mechanically, in particular via a shaft or a gear, or electrically. Thus, the enthalpy of the oxidant obtained in the oxidant turbine can be advantageously utilized in the exhaust gas path.

[0020] In a preferred embodiment, the exhaust gas compressor is arranged upstream of the exhaust gas turbine along the exhaust gas path. Thus, the enthalpy supplied to the exhaust gas in the exhaust gas compressor can be advantageously utilized in the exhaust gas turbine.

[0021] In a preferred embodiment, the exhaust gas compressor is arranged along the exhaust gas path downstream of the cooling device, with the exhaust gas being conducted through the cooling device as a cooling medium; the cooling device is thus also arranged in the exhaust gas path. Thus, additional enthalpy can advantageously be supplied to the exhaust gas heated in the cooling device in the exhaust gas compressor. In particular, the exhaust gas compressor is preferably arranged along the exhaust gas path downstream of the cooling device and upstream of the exhaust gas turbine, so that both the enthalpy obtained in the cooling device and the enthalpy obtained in the exhaust gas compressor can be supplied to the exhaust gas turbine.

[0022] According to the invention, it is provided that the first oxidant compressor is drive-connected to the second electric machine. More generally, it is drive-connected—in a manner not belonging to the invention—to at least one drive device, wherein the at least one drive device can be the exhaust gas turbine arranged along the exhaust gas path. The second electric machine can be operated, in particular, as a motor. The first oxidant compressor can thus be designed, in particular, as an electrically driven compressor or—in a manner not belonging to the invention—as a compressor of an exhaust gas turbocharger. It is also possible for the first oxidant compressor to be drive-connected to both the second electric machine and the exhaust gas turbine, in which case it can then also be designed, in particular in an embodiment of the invention, as a compressor of an electrically assisted exhaust gas turbocharger.

[0023] According to the invention, the exhaust turbine is operatively connected to a third electric machine. The third electric machine can be operated, in particular, as a generator. The enthalpy generated in the exhaust turbine can thus be advantageously converted into electrical energy by the third electric machine.

[0024] The third electric machine is electrically connected to the second electric machine. Thus, the first oxidant compressor can be driven electrically, at least with the assistance of the electrical energy converted from the enthalpy obtained in the exhaust gas turbine. In this case, the first oxidant compressor is preferably not directly connected to an exhaust gas turbine, but rather is designed as an electrically driven compressor.

[0025] According to the invention, the electrochemical energy conversion device has an electrical power bus. In an embodiment not belonging to the invention, at least two electrical components are generally electrically connected to one another via the electrical power bus. The at least two electrical components are then selected from a group consisting of: the first electrical machine assigned to the oxidant turbine, the second electrical machine assigned to the first oxidant compressor, and the third electrical machine assigned to the exhaust gas turbine. The at least two electrical components can advantageously be electrically connected to one another in a particularly simple manner via the electrical power bus.

[0026] In the context of the present technical teaching, an electrical power bus is understood to mean, in particular, an electrical busbar.

[0027] According to the invention, all three electrical components—namely, the first electrical machine, the second electrical machine, and the third electrical machine—are each electrically connected to the electrical power bus and thus also to each other via the electrical power bus. This enables a particularly flexible distribution of the total available electrical energy mediated via the electrical power bus.

[0028] The electrochemical energy conversion device preferably has a control device configured to carry out a method according to the invention described below or a method according to one or more of the embodiments described below. The control device thus enables particularly stable operation of the electrochemical energy conversion device.

[0029] The object is also achieved by providing a method for operating an electrochemical energy conversion device according to the invention or an electrochemical energy conversion device according to one or more of the previously described embodiments with the features of claim 7, wherein, in a first operating mode, a flow resistance for the oxidizing agent in the region of the oxidizing agent turbine is adjusted as a function of at least one operating parameter of the electrochemical energy conversion device. In connection with the method, the advantages already explained in connection with the electrochemical energy conversion device arise in particular. In particular, the method enables particularly stable operation of the electrochemical energy conversion device.

[0030] The first operating mode is, in particular, a control mode. In particular, the first operating mode is an operating mode in which a high power density is provided by the electrochemical energy conversion device.

[0031] The at least one operating parameter is preferably selected from a group consisting of: an oxidant pressure in the oxidant path downstream of the oxidant turbine, and an oxidant temperature in the oxidant path downstream of the oxidant turbine. By adjusting the flow resistance in the region of the oxidant turbine as a function of the at least one operating parameter, a suitable value for the oxidant pressure and / or for the oxidant temperature can preferably be ensured, in particular adjusted, for the galvanic cell.

[0032] In a preferred embodiment, the flow resistance in the region of the oxidant turbine is adjusted by introducing a specific braking torque into the oxidant turbine, in particular into a shaft of the oxidant turbine. Alternatively or additionally, rotational energy is extracted from the oxidant turbine or dissipated from the oxidant turbine depending on the at least one operating parameter. In particular, the braking torque is preferably introduced or the rotational energy is dissipated by suitably controlling the first electrical machine, which is drive-connected to the oxidant turbine—in particular as a generator. For this purpose, the control device of the electrochemical energy conversion device is preferably operatively connected to the first electrical machine and configured to control it.

[0033] Alternatively or additionally, the flow resistance in the region of the oxidant turbine is preferably adjusted by blocking or opening the turbine bypass path that bypasses the oxidant turbine. In particular, when the turbine bypass path is opened, oxidant is diverted via the turbine bypass path. In particular, the flow resistance can preferably be varied by varying the flow cross-section of the turbine bypass path between the blocking position and the opening position—discretely or continuously. For this purpose, the control device of the electrochemical energy conversion device is preferably operatively connected to a controllable actuating device, in particular a valve or flap, arranged in the turbine bypass path and configured to control the latter.

[0034] According to a further development of the invention, the at least one operating parameter in the first operating mode is controlled by setting the flow resistance as a manipulated variable to a predetermined setpoint. In this way, it is advantageously possible to set the at least one operating parameter particularly precisely and to maintain it at the predetermined setpoint. In a preferred embodiment, the oxidizing agent pressure in the first operating mode is controlled by setting the flow resistance as a manipulated variable to a predetermined pressure setpoint. In another preferred embodiment, the oxidizing agent temperature in the first operating mode is controlled by setting the flow resistance as a manipulated variable to a predetermined temperature setpoint.In a particularly preferred embodiment, the oxidant pressure and the oxidant temperature in the first operating mode are controlled by setting the flow resistance as a control variable to a predetermined setpoint value.

[0035] Alternatively, it is preferably provided that the flow resistance in the first operating mode is adjusted as a function of the at least one operating parameter such that the at least one operating parameter does not exceed at least a predetermined limit value. This represents a particularly simple and less computationally intensive embodiment of the method, while at the same time ensuring that the at least one operating parameter does not exceed the predetermined limit value in order to protect the at least one galvanic cell. In a preferred embodiment, the flow resistance is adjusted such that the oxidizing agent pressure does not exceed a predetermined pressure limit value. In another preferred embodiment, the flow resistance is adjusted such that the oxidizing agent temperature does not exceed a predetermined temperature limit value.In a particularly preferred embodiment, the flow resistance is adjusted such that the oxidizing agent pressure and the oxidizing agent temperature do not exceed a predetermined limit value.

[0036] According to a further development of the invention, the flow resistance in the area of ​​the oxidant turbine is set to a minimum value in a second operating mode. This advantageously allows the oxidant to pass through the area of ​​the oxidant turbine with the lowest possible flow resistance.

[0037] The second operating mode is, in particular, an economy operating mode. In particular, the second operating mode is an operating mode in which the electrochemical energy conversion device exhibits high efficiency and thus, in particular, low specific fuel consumption.

[0038] The minimum flow resistance is preferably achieved by operating the oxidizer turbine at idle. In particular, the first electric machine is preferably unloaded, in particular operated without load.

[0039] Alternatively or additionally, the minimum flow resistance is achieved by completely opening the turbine bypass path. This means, in particular, that a maximum flow cross-section is set in the turbine bypass path.

[0040] It is also possible for the electrochemical energy conversion device to have an expander instead of the oxidizer turbine.

[0041] The invention is explained in more detail below with reference to the drawings, which show: Fig. 1 is a schematic representation of a first example of an electrochemical energy conversion device not belonging to the invention; Fig. 2 is a schematic representation of a second example of an electrochemical energy conversion device not belonging to the invention; Fig. 3 is a schematic representation of a third example of an electrochemical energy conversion device not belonging to the invention; Fig. 4 is a schematic representation of a fourth example of an electrochemical energy conversion device not belonging to the invention; Fig. 5 is a schematic representation of a fifth example of an electrochemical energy conversion device not belonging to the invention, and Fig. 6 a schematic representation of an embodiment of an electrochemical energy conversion device.

[0042] Fig. 1 shows a schematic representation of a first example of an electrochemical energy conversion device 1 not belonging to the invention. The electrochemical energy conversion device 1 has at least one galvanic cell 3, in particular a cell stack 5, which is configured to convert chemical energy into electrical energy. During operation of the electrochemical energy conversion device 1, a fuel, in particular hydrogen, methane, methanol, butane, butanol, or natural gas, is supplied to the cell stack 5 via a fuel supply path 7. An oxidizing agent, in particular oxygen or air, is supplied to the cell stack 5 via an oxidizing agent path 9 for electrochemical reaction with the fuel. A first oxidizing agent compressor 11 is arranged along the oxidizing agent path 9 in order to compress the oxidizing agent flowing along the oxidizing agent path 9.Downstream of the first oxidant compressor 11, a cooling device 13 is arranged along the oxidant path 9 to cool the compressed oxidant. Downstream of the cooling device 13, an oxidant turbine 15 is arranged along the oxidant path 9 to expand the compressed, cooled oxidant. The oxidant turbine 15 is driven by the oxidant. In this way, the power, in particular the power density, of the electrical energy conversion device 1 can advantageously be high, since the oxidant can have a high density at a limited pressure at the at least one galvanic cell 3—without risk of damage to the at least one galvanic cell 3.At the same time, the cooling device 13 requires a comparatively small installation space due to the advantageously comparatively high temperature of the oxidant downstream of the first oxidant compressor 11 and upstream of the oxidant turbine 15.

[0043] The cooling device 13 is preferably designed as a heat exchanger, in particular as an indirect heat exchanger, preferably as a recuperator.

[0044] The oxidizer turbine 15 is preferably drive-connected to a first electric machine 17. The first electric machine 17 can be operated, in particular, as a generator. In this way, a braking torque can be introduced into the oxidizer turbine 15, in particular into a shaft 19 of the oxidizer turbine 15, by means of the first electric machine 17.

[0045] The electrochemical energy conversion device 1 also has an exhaust path 21, along which exhaust gas can be discharged from the cell stack 5. Preferably, the cooling device 13 is also arranged in the exhaust path 21; i.e., the exhaust gas flows through the cooling device 13 as a cooling medium. Also arranged in the exhaust path 21 is an exhaust turbine 23, which is driven by the exhaust gas flowing along the exhaust path 21. The exhaust turbine 23 is arranged in particular downstream of the cooling device 13.

[0046] In the first example, the first oxidant compressor 11 is drive-connected to at least one drive device 25, wherein the at least one drive device 25 is selected from a group consisting of a second electric machine 27, which can be operated in particular as a motor, and the exhaust gas turbine 23. In particular, in the first example, the first oxidant compressor 11 is drive-connected to two drive devices 25, namely to the second electric machine 27 as a first drive device 25.1 and to the exhaust gas turbine 23 as a second drive device 25.2. The first oxidant compressor 11 and the exhaust gas turbine 23 are thus in particular part of an electrically assisted exhaust gas turbocharger 29.

[0047] Fig. 2 shows a schematic representation of a second example of an electrochemical energy conversion device 1 not belonging to the invention.

[0048] Identical and functionally identical elements are provided with the same reference symbols in all figures, so that reference is made to the preceding description in each case.

[0049] In the second example of the electrochemical energy conversion device 1, the oxidant turbine 15 is drive-connected to the first oxidant compressor 11. In this way, the oxidant turbine 15 can at least support the drive of the first oxidant compressor 11. In this second example, the first oxidant compressor 11 is also part of the electrically assisted exhaust gas turbocharger 29, so that the drive by the oxidant turbine 15 can be added, in particular, to the drive by the second electric machine 27 and / or the exhaust gas turbine 23.

[0050] Fig. 3 shows a schematic representation of a third example of an electrochemical energy conversion device 1 not belonging to the invention. In the third example of the electrochemical energy conversion device 1, the oxidant turbine 15 is drive-connected to an exhaust gas compressor 31 arranged along the exhaust gas path 21. The exhaust gas compressor 31 is arranged in particular downstream of the cooling device 13 and upstream of the exhaust gas turbine 23 along the exhaust gas path 21. Thus, via the exhaust gas compressor 31, additional enthalpy can advantageously be supplied to the exhaust gas, in addition to the heat supplied in the cooling device 13, which can then be used in the exhaust gas turbine 23.

[0051] Fig. Figure 4 shows a schematic representation of a fourth example of an electrochemical energy conversion device 1 not belonging to the invention. In the fourth example of the electrochemical energy conversion device, the oxidant turbine 15 is drive-connected to a second oxidant compressor 33, which is arranged along the oxidant path 9 downstream of the first oxidant compressor 11 and upstream of the cooling device 13. Thus, enthalpy obtained in the oxidant turbine 15 can be advantageously used to further compress and heat the oxidant upstream of the cooling device 13.

[0052] Fig. 5 shows a schematic representation of a fifth example of an electrochemical energy conversion device 1 not belonging to the invention. In the fifth example of the electrochemical energy conversion device 1, the oxidant turbine 15 is also drive-connected to the second oxidant compressor 33, which now, however - in contrast to the fourth example according to Fig. 4 - is arranged along the oxidant path 9 upstream of the first oxidant compressor 11 and thus simultaneously upstream of the cooling device 13. The enthalpy obtained in the oxidant turbine 15 can thus be advantageously used, in particular, to pre-compress the oxidant upstream of the first oxidant compressor 11.

[0053] Fig.6 shows a schematic representation of an embodiment of an electrochemical energy conversion device 1. In this embodiment, the first oxidant compressor 11 is designed as an electrically driven compressor, with the second electric machine 27 assigned to it as an electric motor drive. The oxidant turbine 15 is drive-connected to the first electric machine 17 without being drive-connected to any other components. The exhaust gas turbine 23 is drive-connected to a third electric machine 35, with the third electric machine 35 operable as a generator. The exhaust gas turbine 23 is also not drive-connected to any other components. Thus, the first oxidant compressor 11, the oxidant turbine 15, and the exhaust gas turbine 23 are each drive-connected only to the electric machines 17, 27, 35 assigned to them.The electrochemical energy conversion device 1 has an electrical power bus 37, in particular in the form of an electrical busbar 39, wherein at least two electrical components are electrically connected to one another via the electrical power bus 37, which are selected from a group consisting of the first electrical machine 17, the second electrical machine 27, and the third electrical machine 35. In particular, each electrical machine 17, 27, 35, i.e. the first electrical machine 17, the second electrical machine 27, and the third electrical machine 35, is each individually connected to the electrical power bus 37, wherein the electrical machines 17, 27, 35 are also electrically connected to one another via the electrical power bus 37. In this way, the total available electrical energy can advantageously be distributed very flexibly between the various electrical machines 17, 27, 35.

[0054] The electrical energy conversion device 1 can optionally also have a turbine bypass path 41, which branches off from the oxidant path 9 upstream of the oxidant turbine 15 and rejoins the oxidant path 9 downstream of the oxidant turbine 15. A controllable actuator 43 is arranged in the turbine bypass path 41, by means of which the turbine bypass path 41 can be selectively blocked or released. In particular, intermediate positions between a blocked position and a released position are also possible, so that a flow cross-section through the turbine bypass path 41 can be variably adjusted by controlling the actuator 43. In a preferred embodiment, the actuator 43 is designed as a valve or flap.

[0055] The electrical energy conversion device 1 also has a control device 45. This is preferably configured—particularly within the scope of an embodiment of a method for operating the electrochemical energy conversion device 1—to adjust, in a first operating mode, a flow resistance for the oxidant in the region of the oxidant turbine 15 as a function of at least one operating parameter of the electrochemical energy conversion device 1. The at least one operating parameter is preferably selected from a group consisting of an oxidant pressure in the oxidant path 9 downstream of the oxidant turbine 15 and an oxidant temperature in the oxidant path 9 downstream of the oxidant turbine 15.

[0056] For this purpose, the control device 45 is preferably operatively connected to at least one sensor 47 arranged downstream of the oxidant turbine 15 and upstream of the cell stack 5, preferably to two sensors 47, namely to a first sensor 47.1 designed as an oxidant pressure sensor 49, and to a second sensor 47.2 designed as an oxidant temperature sensor 51.

[0057] The control device 45 is preferably configured to adjust the flow resistance in the region of the oxidant turbine 15 by controlling the first electric machine 17, in particular by introducing a braking torque into the oxidant turbine 15, in particular into the shaft 19. For this purpose, the control device 45 is operatively connected, in particular, to the first electric machine 17 and configured to control it.

[0058] Alternatively or additionally, the control device 45 is preferably configured to adjust the flow resistance in the region of the oxidizer turbine 15 by controlling the controllable actuating device 43. For this purpose, the control device 45 is in particular operatively connected to the controllable actuating device 43 and configured to control it.

[0059] The control device 45 is preferably configured to regulate the at least one operating parameter in the first operating mode by adjusting the flow resistance as a manipulated variable to a predetermined setpoint. Alternatively, the control device 45 is configured to adjust the flow resistance in the first operating mode as a function of the at least one operating parameter such that the at least one operating parameter does not exceed at least one predetermined limit value.

[0060] The control device 45 is preferably also configured to set the flow resistance in the region of the oxidant turbine 15 to a minimum value in a second operating mode, in particular by controlling the first electric machine 17 to idle operation, and / or by completely opening the turbine bypass path 41 by correspondingly controlling the controllable actuating device 43.

Claims

[1] Electrochemical energy conversion device (1), with - at least one galvanic cell (3) designed to convert chemical energy into electrical energy, - a fuel supply path (7) which is arranged to supply a fuel to the at least one galvanic cell (3), - an oxidizing agent path (9) which is designed to supply the at least one galvanic cell (3) with an oxidizing agent for electrochemical conversion with the fuel, and with - an electric power bus (37), wherein - a first oxidant compressor (11) is arranged along the oxidant path (9) in order to compress the oxidant flowing along the oxidant path (9), wherein - a cooling device (13) is arranged downstream of the first oxidant compressor (11) along the oxidant path (9) in order to cool the compressed oxidant, and wherein - an oxidant turbine (15) is arranged downstream of the cooling device (13) along the oxidant path (9) in order to expand the compressed, cooled oxidant, wherein - the oxidizer turbine (15) is drive-connected to a first electric machine (17), wherein - the first oxidant compressor (11) is drive-connected to a second electric machine (27), wherein - the exhaust gas turbine (23) is operatively connected to a third electric machine (35), wherein - the first electrical machine (17), the second electrical machine (27) and the third electrical machine (35) are each electrically connected to the electrical power bus (37) and thus also - via the electrical power bus - to one another. [2] Electrochemical energy conversion device (1) according to claim 1, wherein the cooling device (13) is designed as a heat exchanger, in particular as an indirect heat exchanger, preferably as a recuperator. [3] Electrochemical energy conversion device (1) according to one of the preceding claims, wherein the first electrical machine (17) is designed as a generator. [4] Electrochemical energy conversion device (1) according to one of the preceding claims, wherein the oxidant turbine (15) is additionally drive-connected to the first oxidant compressor (11) or to a second oxidant compressor (33) arranged along the oxidant path (9) downstream or upstream of the first oxidant compressor (11). [5] Electrochemical energy conversion device (1) according to one of the preceding claims, wherein the electrochemical energy conversion device (1) has an exhaust gas path (21) along which exhaust gas can be discharged from the at least one galvanic cell (3), wherein the oxidant turbine (15) is drive-connected to an exhaust gas compressor (31) arranged along the exhaust gas path (21). [6] Electrochemical energy conversion device (1) according to one of the preceding claims, wherein the first oxidant compressor (11) is additionally drive-connected to an exhaust gas turbine (23), and wherein the second electric machine (27) is designed as a motor. [7] Method for operating an electrochemical energy conversion device (1) according to one of the preceding claims, wherein in a first operating mode a flow resistance for the oxidant in the region of the oxidant turbine (15) is set as a function of at least one operating parameter of the electrochemical energy conversion device (1), wherein the at least one operating parameter is preferably selected from a group consisting of: an oxidant pressure in the oxidant path (9) downstream of the oxidant turbine (15), and an oxidant temperature in the oxidant path (9) downstream of the oxidant turbine (15). [8] Method according to claim 7, wherein in the first operating mode - the at least one operating parameter is controlled by setting the flow resistance as a control variable to a predetermined setpoint, or wherein - the flow resistance is adjusted as a function of the at least one operating parameter such that the at least one operating parameter does not exceed at least one predetermined limit value. [9] Method according to one of claims 7 or 8, wherein in a second operating mode the flow resistance in the region of the oxidant turbine (15) is set to a minimum value.

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