Fuel cell compressor with integrated heat exchanger

Abstract

A system comprising a fuel cell 200 and a rotating assembly comprising: a compressor 100 comprising a compressor wheel 102 and an expander wheel 104 linked by a rotable shaft, and a motor 150 providin

Description

TECHNICAL FIELD

[0001] The technical field generally relates to a fuel cell system that includes a compressor and a heat exchanger, and more particularly relates to a fuel cell system that includes a compressor with a compressor wheel and an expander wheel and a heat exchanger for transferring heat between air exiting from the compressor wheel of the compressor to air entering the expander wheel of the compressor. BACKGROUND

[0002] The automotive industry uses fuel cell technology to provide power for vehicles and for components of vehicles. Other industries also make use of fuel cell technology to provide power for various applications. Fuel cells use hydrogen to produce electricity. Hydrogen is an attractive source of fuel, in particular in view of the continual need for vehicles to generate less emissions.

[0003] A fuel cell typically contains an anode and a cathode, with an electrolyte disposed between the anode and the cathode. The electrolyte may be an electrolyte for use in a solid oxide fuel cell, such as yttria-stabilized zirconia. The electrolyte may be an electrolyte for use in a polymer electrolyte membrane fuel cell, such as a solid polymer electrolyte. Hydrogen is supplied to the anode and oxygen is supplied to the cathode. The hydrogen is ionized in the anode to generate protons and electrons. The protons pass through the electrolyte to the cathode. After reaching the cathode, the protons react with the oxygen in the cathode to generate water. The electrons, which do not pass through the electrolyte, form an electric current which can be used to perform electrical work, such as supplying electrical power to an electric motor. The chemical reaction at the cathode is exothermic, and therefore produces heat energy. As is known, multiple fuel cells can be combined into a fuel cell stack.

[0004] In order to supply oxygen to the cathodes of fuel cells in the fuel cell stack, a compressor may be used. The compressor is used to control the intake of oxygencontaining air to the cathodes of the fuel cell stack. Typically, the compressor includes a compressor wheel and a motor to provide torque to the compressor wheel.

[0005] It is desirable to improve the efficiency and ease of manufacturing of fuel cell systems including compressors, and also to ensure that such fuel cell systems can satisfy the space constraints associated with modern vehicles. Additional advantages and features of the invention will be made apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. SUMMARY

[0006] According to a first aspect, there is provided a system comprising a fuel cell comprising an anode side; a cathode side and an electrolyte disposed between the anode side and the cathode side, wherein the cathode side has an inlet and an outlet; and a compressor. The compressor comprises a rotating assembly comprising a compressor wheel; an expander wheel; and a rotatable shaft connected to each of the compressor wheel and the expander wheel; a motor configured to provide torque to the rotating assembly, a first channel configured to channel air incident upon the compressor wheel from the compressor wheel to the inlet of the cathode side of the fuel cell via a heat exchanger; and a second channel configured to channel air exiting the outlet of the cathode side of the fuel cell to the expander wheel via the heat exchanger, such that heat is transferred from air flowing in the first channel to air flowing in the second channel.

[0007] According to embodiments, the motor is configured to receive electrical power from the fuel cell.

[0008] According to embodiments, the heat exchanger is formed by a section of the second channel enveloping a section of the first channel.

[0009] According to embodiments, an exterior surface of the section of the first channel which is enveloped by the second channel is provided with fins. Optionally, the fins are curved.

[0010] According to embodiments, the system further comprises an air humidifier configured to increase humidity of air entering into the inlet of the cathode side of the fuel cell.

[0011] According to embodiments, the air humidifier is configured to extract moisture from air exiting the outlet of the cathode side of the fuel cell and to transfer extracted moisture to air entering into the inlet of the cathode side of the fuel cell.

[0012] According to embodiments, the system further comprises a water separator configured to remove moisture from air in the second channel, optionally wherein the water separator is integrated into the second channel.

[0013] According to an embodiment, the water separator is integrated into the second channel in a position before the heat exchanger, in a direction of air flow through the second channel.

[0014] According to embodiments, the system further comprises a charge air cooler configured to further cool air flowing in the first channel. The charge air cooler is located between the heat exchanger and the inlet of the cathode side of the fuel cell.

[0015] According to a second aspect, there is provided a compressor comprising a rotating assembly comprising a compressor wheel; an expander wheel; and a rotatable shaft connected to each of the compressor wheel and the expander wheel; a motor configured to provide torque to the rotating assembly, a first channel configured to channel air incident upon the compressor wheel from the compressor wheel to an inlet of a cathode side of the fuel cell via a heat exchanger; and a second channel configured to channel air exiting an outlet of the cathode side of the fuel cell to the expander wheel via the heat exchanger, such that heat is transferred from air flowing in the first channel to air flowing in the second channel.

[0016] According to embodiments, the heat exchanger is formed by a section of the second channel enveloping a section of the first channel.

[0017] According to embodiments, the section of the first channel enveloped by the second channel comprises an exterior surface, wherein the exterior surface is provided with fins. Optionally, the fins are curved.

[0018] According to embodiments, the compressor further includes a water separator configured to remove moisture from air in the second channel, wherein the water separator is integrated into the second channel. Optionally, the water separator is integrated into the second channel in a position before the heat exchanger, in a direction of air flow through the second channel. BRIEF DESCRIPTION OF DRAWINGS

[0019] The various embodiments will hereinafter be described in conjunction with the following drawings, wherein like numerals denote like elements, and wherein:

[0020] FIG. 1 shows a schematic of a fuel cell;

[0021] FIG. 2 shows a schematic of a fuel cell system according to an embodiment;

[0022] FIG. 3 shows a first view of a representation of a compressor according to an embodiment;

[0023] FIG. 4 shows a second view of the compressor of FIG. 3; and

[0024] FIG. 5 shows a view of a compressor and associated fuel cell in accordance with an embodiment. DETAILED DESCRIPTION

[0025] The following detailed description is merely exemplary in nature and is not intended to limit the application and uses of embodiments of the present disclosure. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding introduction, brief summary or the following detailed description. Embodiments of the present disclosure may be described herein in terms of functional and / or logical block components and various method steps. In addition, those skilled in the art will appreciate that embodiments of the present disclosure may be practiced in conjunction with any number of systems, and that the systems described herein is merely exemplary embodiments of the present disclosure.

[0026] For the sake of brevity, conventional techniques related to certain functions of fuel cells and fuel cell compressors (and the individual operating components of fuel cells and fuel cell compressors) may not be described in detail herein. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent example functional relationships and / or physical couplings between the various elements. It should be noted that alternative or additional functional relationships or physical connections may be present in an embodiment of the present disclosure.

[0027] FIG. 1 shows a schematic of a fuel cell 10. The fuel cell includes an anode 12 and a cathode 14. The anode 12 receives anode fuel containing hydrogen gas from a hydrogen source (not shown in this figure) at an anode input 16. The cathode 14 receives charge gas containing oxygen at a cathode input 18. The charge gas may advantageously be compressed air containing oxygen. Protons from the hydrogen in the hydrogen gas traverse an electrolyte 20 from the anode 12 to the cathode 14. The direction of travel of the protons is represented in FIG. 1 with a dashed arrow. The electrolyte may be, for example, a proton exchange membrane (PEM) with a solid polymer electrolyte, such as an ion exchange resin. The protons react with oxygen from the charge gas at the cathode to form water. Free electrons are channeled along a conductor 22 to perform electrical work, for example to power an electric motor 24. As will be explained in more detail below, the electric motor 24 may be associated with a fuel cell compressor. Depleted anode fuel exits the fuel cell via an anode outlet 26, and depleted charge gas exits the fuel cell via a cathode outlet 28.

[0028] Multiple individual fuel cells may be combined together to form a fuel cell stack to increase electrical power capabilities. In a fuel cell stack the same hydrogen source and charge gas source may be used for all of the individual fuel cells in the fuel cell stack.

[0029] Turning to FIG. 2, a schematic of a fuel cell system according to an embodiment is shown. The fuel cell system includes a compressor 100 and a fuel cell stack 200. The compressor may include a housing 101. The compressor 100 includes an electric motor 150 arranged to rotate a compressor wheel 102. The electric motor 150 is arranged to receive electrical power, as will be explained in more detail below. In some embodiments, the electric motor 150 is arranged to receive electrical power from a separate electrical power source. In the embodiment shown in FIG. 2, the electric motor 150 is arranged to receive electrical power from the fuel cell stack 200.

[0030] In order to provide additional power to the electric motor so as to meet power demand requirements that are larger than can be provided by the electric motor alone, the compressor 100 may include a cathode gas expander wheel 104 configured to receive expelled cathode gas and convert the energy associated with the expelled cathode gas into rotational energy. The expander wheel 104 is connected to the compressor wheel 102 through a common rotational shaft. By supplying compressed air exiting from the fuel cell stack to the expander wheel 104 of the compressor 100, the expander wheel 104 provides additional torque to the compressor wheel 102. The size of the electric motor 150 can be therefore reduced whilst still maintaining a desired power output of the compressor 100, or the overall power output of the electric motor 150 can be increased due to this additional torque provided by the expander wheel 104.

[0031] In FIG. 2, air 50 is supplied to the compressor wheel 102 of the compressor 100. Optionally, the air 50 may pass through an air filter 60 prior to reaching the compressor wheel 102. The air filter 60 performs the function of removing contaminants, such as dust and debris, from the air 50 before the air 50 is incident upon the compressor wheel 102. If not removed or reduced, contaminants may reduce the lifespan of the compressor wheel 102. The air filter 60 may include a filtration medium to capture contaminant particles as they pass through the air filter 60.

[0032] As it rotates, the compressor wheel 102 compresses the intake air 50. The air 50 compressed by the compressor wheel 102 is then channeled to a fuel cell stack 200 to act as the cathode charge gas for the fuel cell stack 200, as will be explained in more detail below. The fuel cell stack 200 is configured to receive compressed air, containing oxygen, from the compressor wheel 102, to receive anode fuel from a hydrogen source (not shown in this figure) and to output electrical power in the manner as described above. This electrical power may then be supplied to the electric motor 150 via an electrical connection 210.

[0033] After the compressed air exits the fuel cell stack 200, this air may be channeled to the expander wheel 104 of the compressor 100 so as to drive the expander wheel 104. Such an arrangement allows for the size of the motor 150 required to provide a desired power output level to be reduced, as was explained above.

[0034] When the inventors researched how to design such a fuel cell system, they recognized that the use of a compressor to compress air supplied to the fuel cell stack 200 presents some technical challenges. In particular, during compression of air by the compressor wheel 102, the compressor wheel 102 typically heats air to a higher temperature than the optimal temperature for air entering the fuel cell stack. For example, the compressor wheel 102 could heat air to around 150°C to 180°C, whereas the desired temperature for compressed air entering the cathode of fuel cell would be around 80°C for improved fuel cell efficiency. As such, it was recognized by the inventors that a technique for cooling the compressed air exiting the compressor wheel 102 would be needed before the compressed air enters the fuel cell stack 200.

[0035] Additionally, it was recognized by the present inventors that it would be desirable to increase the energy of the compressed air exiting the fuel cell stack 200 and being supplied to the expander wheel 104 in order to increase the energy supplied to the expander wheel 104.

[0036] In order to overcome both of these technical challenges with a single solution, the present inventors recognized that a heat exchanger 250 could be used to transfer heat energy from the compressed air exiting the compressor wheel 102 to the air being channeled to the expander wheel 104. This arrangement has the benefit of reducing the temperature of the compressed air exiting the compressor 102 to a temperature that is suitable for use with the fuel cell stack, and also has the benefit of increasing the temperature of the air entering the expander wheel 104 to thereby increase the energy supplied to the expander wheel 104 that may be used to provide torque to the compressor wheel. The heat exchanger 250 will be explained in more detail below.

[0037] The fuel cell system may additionally include an air humidifier 110. It is advantageous for the compressed air entering the fuel cell stack 200 to contain moisture in order to improve the transfer of oxygen from the compressed air to the cathodes of the fuel cell stack and also to improve the conductivity of the electrolyte arranged between the anodes and cathodes of fuel cells in the fuel cell stack 200.

[0038] In an embodiment, the air humidifier 110 is configured to transfer water from the compressed air exiting the fuel cell stack 200, which contains water as a byproduct of the fuel cell reaction, to compressed air entering the fuel cell stack 200. The air humidifier 110 therefore improves the humidity of the air entering the fuel cell stack 200 and also reduces the water content of the air exiting the fuel cell stack that is supplied to the expander wheel 104, which is desirable in order to reduce water-based corrosion of the blades of the expander wheel 104. In embodiments, the air humidifier 110 comprises a vapor exchange membrane or a water vapor transport (WVT) device to allow water vapor to transfer from the more humid air exiting the cathode side of the fuel cell to less humid air entering the cathode side of the fuel cell.

[0039] Alternatively, the air humidifier 110 may be arranged to mix the compressed air entering the fuel cell stack 200 with water vapor obtained from a separate water source (not shown) and does not reduce the water content of the air exiting the fuel cell stack 200 that is subsequently supplied to the expander 104.

[0040] In order to further reduce the water content of the air that is supplied to the expander wheel 104 so as to reduce phenomena such as droplet erosion of blade surfaces of the expander wheel 104, the fuel cell system may additionally include a water separator 120. The water separator 120 is configured to separate water from the air supplied to the expander wheel 104. The separated water may be provided to other systems, such as systems that use water for cooling effects. The water separator 120 may function by coalescing moisture within the air flowing towards the expander wheel 104, for example through the use of a coalescing filter or medium. The coalesced water is then extracted, for example through gravitational separation or via a pump. In various embodiments, the water separator 120 is integrated within the compressor 100 and is not provided as a separate unit. By integrating the water separator 120 with the compressor 100, the overall size of the fuel cell system is not overly increased, thereby allowing for space constraints associated with modern vehicles to be satisfied.

[0041] Returning to the function of the heat exchanger 250, after the present inventors recognized that a heat exchanger would be advantageous, the present inventors encountered a technical issue in how to integrate the heat exchanger into the fuel cell system in order to allow for sufficient heat transfer between the air exiting the compressor wheel 102 and the air entering the expander wheel 104 whilst still ensuring that the size of the fuel cell system could satisfy the necessary space constraints to allow the fuel cell system to be used in a vehicle.

[0042] In particular, it was noted by the inventors that the heat exchanger 250 should, for improved efficiency, be able to reduce the temperature of the compressed air exiting the compressor wheel 102 from a temperature of between around 150°C to 180°C to a temperature of around 80°C before the air entered the fuel cell stack 200, and should also be able increase the temperature of the air that has exited the fuel cell stack 200 from a temperature of around 90°C to a temperature of around 120°C to 140°C before entering the expander wheel 104. This required a specific design of heat exchanger, as will be explained in more detail below.

[0043] In embodiments, a charge air cooler 180 may also be located between the heat exchanger 250 and the fuel cell stack 200, for example between the heat exchanger 250 and the air humidifier 110. The charge air cooler 180 is configured to further cool compressed air flowing from the compressor wheel 102 before it enters the fuel cell stack 200 in addition to the cooling provided by the heat exchanger 250. In embodiments, charge air cooler 180 comprises an air-to-liquid cooler, which used liquid coolant to absorb heat from the compressed air. In alternative embodiments, the charge air cooler 180 comprises an air-to-air cooler, in which heat from the compressed air is dissipated to the surrounding environment. It will be appreciated that, through incorporation of the heat exchanger 250, the size of the charge air cooler 180 can be reduced as compared to a hypothetical system which does not include a heat exchanger.

[0044] FIG. 3 shows a compressor 300 with an integrated heat exchanger 350 that can achieve the sufficient level of heat transfer between air exiting a compressor section 304 containing a compressor wheel (not shown) and entering an expander section 305 containing an expander wheel (not shown) whilst still satisfying space constraints.

[0045] As can be seen in FIG. 3, a first channel 360 is provided to guide the flow of air exiting from a compressor section 304 of the compressor 300. The channel 360 has an exterior surface 361 which is at least partly disposed within a second channel 370 configured to guide the flow of air to an expander section 305 of the compressor 300. In embodiments, the exterior surface 361 of the channel 360 which is disposed within the channel 370 is provided with heat exchange fins 365 that increase the surface area available for heat exchange between air flowing through the channel 360 and air flowing through the channel 370. The direction of the flow of air through the first channel 360 and the direction of the flow of air through the second channel 370 are shown in FIG. 3 through the use of dashed arrows. The fuel cell stack associated with the compressor 300 is not shown in this figure.

[0046] It has been recognized by the inventors that the arrangement of the first and second channels 360, 370 as shown in FIG. 3, with the second channel 370 enveloping at least part of the first channel 360, is more efficient at transferring heat between air flowing in the first channel 360 and air flowing the second channel 370 than a reverse configuration where the first channel 360 envelops a section of the second channel 370. It is theorized that the improved heat transfer associated with the second channel 370 enveloping a section of the first channel 360 as compared to the reverse configuration is due to heat from the first channel 360 not being transmitted to the surrounding environment in the section which is enveloped by the second channel 370 as efficiently in the reverse configuration.

[0047] In operation, at least a portion of the air compressed by a compressor wheel (not shown in this figure) within the compressor section 304 flows through the channel 360. Heat is transferred from the compressed air to walls of the channel 360 and is also transferred through the solid material of the fins 365 to heat both the fins 365 and the surface 361 of the channel 360. This heat is then transferred to fluid flowing through the channel 370 which leads to the expander section 305 of the compressor 300. The increased surface area provided by the fins 365 allows for heat to be transferred from fluid flowing within the channel 360 to fluid flowing within the channel 370 at an increased rate. Additionally, the fins 365 disrupt the flow of fluid flowing within the channel 370 and thereby introduce a degree of turbulence into this flow, which promotes mixing of fluid particles in the flow which further increases the heat transfer rate to fluid flowing within channel 370.

[0048] The fins 365 may have various shapes. For example, the fins 365 may be straight, curved, or have a wave-type surface. In embodiments, the fins 365 are curved in order to maximize the surface area of the fins available for heat transfer whilst ensuring that the fins do not extend too far in one particular direction in order to better satisfy space constraints associated with the compressor 300.

[0049] Another view of the compressor 300 is shown in FIG. 4. As can be seen from this figure, through the use of curved fins 365 disposed on an exterior surface of the channel 360, through which flows a portion of air exiting a compressor wheel (not shown) from a compressor section 304, the heat transfer between this air and air flowing through the channel 370 leading to the expander section 305 is improved with only a small increase in the overall size of the compressor 300.

[0050] Operation of the compressor 300 will be described with respect to the view in FIG. 4.

[0051] In operation, air is drawn into the compressor section 304 where it is incident upon a compressor wheel disposed inside the compressor section. The compressor wheel is operably linked to an expander wheel located within the expander section 305 of the compressor 300 via a common rotating assembly shaft to form a rotating assembly, such that the speed of rotation of the compressor wheel matches the speed of rotation of the expander wheel.

[0052] The compressor wheel acts to compress the air, which consequently heats the air. A portion of this compressed, heated air flows into channel 360. The compressed air flowing through the channel 360 is cooled via the heat exchanger 350, as will be explained in more detail below. After being cooled via the heat exchanger 350, the compressed air flows to a cathode side of a fuel cell (not shown in this figure) to act as the oxidant in the fuel cell reaction to produce electricity.

[0053] The electricity generated by the fuel cell may be used to power a motor configured to provide torque to the common rotating assembly shaft of the rotating assembly that includes the compressor wheel and the expander wheel.

[0054] The air exiting from the cathode side of the fuel cell flows through channel 370 and through heat exchanger 350, where it is heated by heat transferred from the air exiting the compressor wheel and flowing through channel 360. The air flowing through channel 360 is consequently cooled by the air flowing through channel 370. After this heat exchange occurs, the air flowing through channel 370 is incident upon the expander wheel in the expander section 305 of the compressor 300 to provide energy to the expander wheel.

[0055] The additional energy provided to the expander wheel may allow for a smaller motor to be used in order to provide the same torque as compared to a hypothetical system in which air flowing through channel 370 was not provided to the expander wheel within the expander section 305. Provision of this additional torque may also allow for a reduction in the amount of hydrogen consumed by the fuel cell stack in order to supply power to the motor.

[0056] As can be seen in FIG. 4, an exterior surface of the channel 360 is provided with fins 365 to increase the surface area available for heat transfer between air flowing in the channel 360 and air flowing in the channel 370, thereby allowing for a reduction in the increase in the size of the compressor 300 necessary to implement the heat exchanger 350. As noted above, the fins 365 may be curved to further reduce the space occupied by the heat exchanger 350 so as to meet space constraints for the compressor 300.

[0057] Embodiments of the invention as described above may be formed from standard manufacturing practices, such as casting, welding etc. For example, at least part of the compressor 300, such as the first and second channels 360, 370, may be cast in aluminum, which has a relatively high heat conductivity so as to further increase the heat transfer between air flowing in the first and second channels, 360, 370.

[0058] Turning to FIG. 5, another embodiment of a compressor 600 is shown together with an associated fuel cell stack 200. The compressor 600 includes a water separator 620 that is integrated into the second channel 670. In the embodiment shown, the water separator 620 is integrated into the second channel 670 in a position before the heat exchanger 650 in the direction of air flow. In such a position, the water separator efficiency is improved due to the higher water content of air in this location, since no water vaporization in the heat exchanger 650 has yet occurred. However, in alternative embodiments the water separator 620 may be integrated into the second channel 670 in a position after the heat exchanger 650 in the direction of air flow.

[0059] By integrating the water separator 620 into the second channel 670 such that it is possible to cast both of the second channel 670 and water separator 620 as a single piece in a single manufacturing step, it is possible to improve the manufacturing efficiency of a fuel cell system containing a water separator. In addition, by integrating the water separator 620 into the second channel 670 such that it is possible to cast both of the second channel 670 and water separator 620 as a single piece, it is possible to reduce the likelihood of water leaks.

[0060] As is shown in FIG. 5, an outer wall of the second channel 670 is contiguous with an outer wall of the water separator 620. In this manner, ease of manufacturing may be improved, for example by allowing both the second channel and the integral water separator to be formed as a single piece, the likelihood of leaks is reduced and the overall size of the compressor and water separator combination is reduced.

[0061] While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the disclosure in any way.

[0062] Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the disclosure as set forth in the appended claims and the legal equivalents thereof.

Claims

1. A system comprising:a fuel cell (200) comprising an anode side; a cathode side and an electrolyte disposed between the anode side and the cathode side, wherein the cathode side has an inlet and an outlet; anda compressor (100, 300, 600), the compressor comprising:a rotating assembly comprising a compressor wheel (102); an expander wheel (104, 390); and a rotatable shaft connected to each of the compressor wheel and the expander wheel;a motor (150) configured to provide torque to the rotating assembly;a first channel (360) configured to channel air incident upon the compressor wheel from the compressor wheel to the inlet of the cathode side of the fuel cell via a heat exchanger (250, 350, 650); anda second channel (670) configured to channel air exiting the outlet of the cathode side of the fuel cell to the expander wheel via the heat exchanger, such that heat is transferred from air flowing in the first channel to air flowing in the second channel.

2. The system of Claim 1, wherein the motor (150) is configured to receive electrical power from the fuel cell (200).

3. The system of Claim 1 or 2, wherein the heat exchanger is formed by a section of the second channel (670) enveloping a section of the first channel (360).

4. The system of Claim 3, wherein the section of the first channel (360) enveloped by the second channel comprises an exterior surface (361), wherein the exterior surface is provided with fins (365), optionally wherein the fins are curved.

5. The system of any preceding claim, wherein the system further comprises an air humidifier (110) configured to increase the humidity of air entering into the inlet of the cathode side of the fuel cell, wherein the air humidifier is configured to extract moisture from air exiting the outlet of the cathode side of the fuel cell and to transfer extracted moisture to air entering into the inlet of the cathode side of the fuel cell.

6. The system of any preceding claim, wherein the system further comprises a water separator (120, 620) configured to remove moisture from air in the second channel, wherein the water separator is integrated into the second channel (670), optionally wherein an outer wall of the second channel is contiguous with an outer wall of the water separator.

7. The system of Claim 6, wherein the water separator is integrated into the second channel in a position before the heat exchanger, in a direction of air flow.

8. The system of any preceding claim, further comprising a charge air cooler (180) configured to further cool air flowing in the first channel.

9. The system of Claim 8, wherein the charge air cooler is located between the heat exchanger and the inlet of the cathode side of the fuel cell.

10. A compressor comprising:a rotating assembly comprising a compressor wheel (102); an expander wheel (104, 390); and a rotatable shaft connected to each of the compressor wheel and the expander wheel;a motor (150) configured to provide torque to the rotating assembly;a first channel (360) configured to channel at least a portion of air incident upon the compressor wheel from the compressor wheel to an inlet of a cathode side of the fuel cell via a heat exchanger (250, 350, 650); anda second channel (670) configured to channel air exiting an outlet of the cathode side of the fuel cell to the expander wheel via the heat exchanger, such that heat is transferred from air flowing in the first channel to air flowing in the second channel.

11. The compressor of Claim 10, wherein the heat exchanger is formed by a section of the second channel enveloping a section of the first channel.

12. The compressor of Claim 11, wherein the section of the first channel enveloped by the second channel comprises an exterior surface (361), wherein the exterior surface isprovided with fins (365).

13. The compressor of Claim 12, wherein the fins are curved.

14. The compressor of any of Claims 10 to 13, further comprising a water separator (120, 620) configured to remove moisture from air in the second channel, wherein the water separator is integrated into the second channel (670), optionally wherein an outer wall of the second channel is contiguous with an outer wall of the water separator.

15. The compressor of Claim 13, wherein the water separator is integrated into the second channel in a position before the heat exchanger, in a direction of air flow.

16. A compressor comprising:a rotating assembly comprising a compressor wheel (102); an expander wheel (104, 390); and a rotatable shaft connected to each of the compressor wheel and the expander wheel;a motor (150) configured to provide torque to the rotating assembly;a first channel (360) configured to channel at least a portion of air incident upon the compressor wheel from the compressor wheel to an inlet of a cathode side of the fuel cell via a heat exchanger (250, 350, 650); anda second channel (670) configured to channel air exiting an outlet of the cathode side of the fuel cell to the expander wheel via the heat exchanger, such that heat is transferred from air flowing in the first channel to air flowing in the second channel, wherein a water separator (120, 620) configured to remove moisture from air in the second channel is integrated into the second channel such that an outer wall of the second channel is contiguous with an outer wall of the water separator.s

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