DE102007007934A1 - Vehicle i.e. bus, has compressor connectable with vehicle wheels such that vehicle wheels drive compressor, and heat exchanger arranged downstream to compressor for cooling compressed air - Google Patents

Abstract

The vehicle has an electric drive (3) supplied by a fuel cell (8) with an electric energy for driving vehicle wheels (2). An air supply device connected with the fuel cell has an air reservoir (7) for storing compressed air, and a compressor (4) is connected with a cathode (8.1) of the fuel cell and with the air reservoir for producing the compressed air. The compressor is connectable with the vehicle wheels such that the vehicle wheels drive the compressor. A heat exchanger (11) is arranged downstream to the compressor for cooling the compressed air.

Description

The The invention relates to a vehicle having a fuel cell drive, comprising a powered by a fuel cell with electric power Electric drive for driving the vehicle wheels and one with the fuel cell connected air supply device, the one Air storage for storing compressed air and one with the cathode connectable to the fuel cell and connectable to the air reservoir first compressor for generating compressed air comprises.

at Vehicles with fuel cell drive is the electric drive to Driving the vehicle wheels through a fuel cell supplied with electrical energy. The fuel cell in turn becomes generally by a compressor that works with the fuel cell constantly connected, supplied with air. The compressor usually has its own drive device, which in turn supplies electricity from the fuel cell becomes. The needed for the drive of the compressor Energy is therefore no longer for the electric drive Available. Especially with temporarily high performance requirements to the electric drive also increases the power requirement for the drive of the compressor, so that for the electric drive provided electric energy with increasing power requirement reduced by the likewise increasing power requirements of the compressor becomes. This conflict of objectives must be resolved.

It are vehicles, such as buses, fuel cell powered known that without hybridization, d. H. without any intermediate storage (flywheel, Battery, supercaps). These vehicles have one correspondingly high consumption, since all performance requirements including the associated dynamics of the fuel cell system or have to be covered by the fuel cell stack. Furthermore, vehicles are known (for example, combustion engine Hybrid and fuel cell hybrid), in which the drive partly via an internal combustion engine or a fuel cell system, on the other hand via a corresponding Cached storage such as battery, supercaps or a flywheel becomes. These buffers are usually downhill or charged with energy during braking (recuperation, brake energy recovery) and if necessary (ie power requirement) unloaded, or act supporting the drive. A disadvantage of These caches are the relatively high cost and the relative high weight, partly complex construction and the corresponding at Operation limited life. The described Caches have the further disadvantage that they only for the caching of energy can be used and can not take on any additional "additional functions", which would be beneficial in any other way.

From the German patent application DE 100 13 660 A1 For example, a vehicle having a fuel cell connected to an air supply means having an air compressor and an air reservoir connectable to the air compressor is known. The air compressor is constantly connected to the fuel cell. The air reservoir can be connected by opening a valve with the air compressor and filled in this way with compressed air. In the same way, the compressed air can be supplied from the air reservoir, if necessary, the fuel cell. In the proposed solution, a partial flow is removed from the air mass flow generated by the air compressor when the air reservoir is filled. This partial flow is no longer available for supplying the fuel cell. Although the increased fuel demand of the fuel cell due to the supplementation of the air mass flow generated by the air compressor can be operated by the compressed air stored in the air reservoir at temporary high power requirements of the electric drive, the problem still remains that the power required for the drive of the air compressor is no longer the electric drive is available.

From the German patent application DE 101 54 047 A1 is a vehicle with a pneumatic motor, a compressed air reservoir and a means for braking is known in which when braking the vehicle, the compressed air motor is operable as a compressor that compresses ambient air, and further wherein a means for feeding the compressed air is provided in the compressed air reservoir. Here, the compressed air generated during braking is temporarily stored in order to subsequently use it again to drive the vehicle.

outgoing From this prior art it is an object of the present invention Invention to provide a fuel cell powered vehicle in which the air mass flow required for the fuel cell at least partially using recovered energy can be generated.

According to the invention These tasks are solved by a vehicle with the features of claim 1

advantageous Embodiments and developments of the invention are in the dependent Claims described.

The fuel cell powered vehicle of the present invention includes an electric power supplied by a fuel cell with electric power powered to drive the vehicle wheels and an air supply device connected to the fuel cell, which comprises an air reservoir for storing compressed air and connectable to the cathode of the fuel cell and connectable to the air storage first compressor for generating compressed air and is characterized in that the first compressor with at least one vehicle wheel is connectable so that the vehicle wheel drives the first compressor while driving. This makes it possible to supply compressed air as needed for the supply of the fuel cell. In addition, in this case preferably a small proportion of the energy generated by the fuel cell is consumed to generate the compressed air. Furthermore, the recovery of a portion of the energy used for driving the vehicle and thus the saving of fuel are possible.

at the vehicle according to the invention is when braking recoverable energy used at least partially by that at least one compressor (air compressor) during braking, for example by an intermediate gear and / or a clutch with a vehicle wheel or an axle of the vehicle so in operative connection can be brought that from the compressor air from the environment sucked, compaction tet and cached in an air storage becomes. The compressor and the air reservoir are preferably off Compressed air brake systems in commercial vehicles known components, since These are inexpensive.

The can be stored in one or more air tanks stored compressed air used repeatedly and / or for different purposes become. The air stored in the air reservoir and pressurized air For example, when starting up, it may relieve the load Compressor (the fuel cell system) take over what to a lower necessary performance of the fuel cell and thus leading to fuel savings. This is why particularly advantageous because the compressor in fuel cell systems the secondary consumer with the largest necessary Performance is (can be about 10% to 15% of a fuel cell stack performance be). Because when load changes (upward, d. H. more load) the necessary air mass flow partly from the or the air reservoirs, the compressor is resulting in fuel savings and improved fuel economy d. H. higher dynamics of the fuel cell system leads, without additional (energetic) effort.

Furthermore Let's go through the addition to that from the compressor of the fuel cell system derived air stream and that of the or the air reservoirs derived airflow so-called boost functions, d. H. the fulfillment of a short-term performance requirement, the above the actual maximum continuous power of the fuel cell system is, without this a compressor (the Fuel cell system) can cover this "additional power" got to. This boost function is also relatively easy realize low consumption, since the short-term necessary additional air flow for the boost function by compressed air from the air reservoir can be removed. The power characteristic or the power peaks the compressor of the fuel cell system can be through the Thus stored in the air storage compressed air thus cut off, resulting in a improved dynamic behavior and fuel savings leads.

A another option to use the stored in the air storage Compressed air results in improved startability (also cold start capability) or for related standing start-up and shutdown processes of the fuel cell system (Startup / shutdown) or rinsing (purge) procedures, as described in more detail below.

One Another advantage is that even when the air reservoir is full is, the full braking deceleration is ensured, for example by removing compressed air from the air reservoir or directly after compression is blown off. Unlike hybrid drives with power storage is independent to achieve full braking deceleration from a filling level of the memory, no special braking system necessary (mechanical / hydraulic), which in the power storage breaks down the part of the braking energy that passes through the full store no longer taken over by the electrical (regenerative) braking device can be.

outgoing from a known fuel cell powered vehicle in which a compressor is permanently connected to the fuel cell can an improvement in terms of the objectives of the present invention be achieved in that in the vehicle described above Furthermore, a switching unit is provided, through which the first Compressor either at all times only with the cathode of the fuel cell o which is connectable only to the air storage and that a second Compressor is provided, which is constantly connected to the cathode Fuel cell is connected.

Here, the air compressor referred to here as the second compressor is the already existing, constantly connected to the fuel cell compressor, while the first compressor is an additional air compressor, which is always connected via the switching unit only one of the components air storage or fuel cell, so that either the air reservoir is used to store energy, or that of the second compressor Fuel cell supplied mass air flow is amplified by the first compressor, for example, to cover peaks in the power requirement of the electric drive.

Should the first compressor without additional fuel consumption be operated to - as described above - energy temporarily store or the air mass flow of the second compressor can be advantageous provided that the Operative connection between the first compressor and the vehicle wheel or an axle of the vehicle is made only during braking, by, for example, an operative connection between the braking device and the first compressor is provided. This way will simultaneously with the operation of the service brake of Vehicle the first compressor driven and so the otherwise used lost braking energy.

Around generally a high braking effect with low spatial and to ensure weight requirement of the air reservoir, it is advantageous in the first compressor connectable to the drive axle, a multi-stage compressor, vorzugswei se with respective intermediate cooling to use. Due to the achievable high pressure levels leaves more air mass with the same geometric dimensions in the air reservoir accommodate than with single-stage compression. Further advantageous can be provided that before and / or after the air storage (ie input and / or output side) a filter (activated carbon filter) is attached, the potential contamination and particles from the Air mass flow filters out. The coupling of the first compressor to the electric drive or to a vehicle wheel of the vehicle or For example, a drive axle can be made such that the air compressor depending on the air pressure required for the above processes and applications is switched on. This brings no fuel saving in this mode of operation, but secures if necessary the adequate compressed air supply for the above mentioned Processes and applications from, without this a very large air storage volume must be installed.

at the fuel cell system described with stored in the air storage, by compressed air generated by compressed air, it is possible during the Startup process to support the second compressor, so that this requires less energy and more energy the fuel cell system the drive available can be made.

In An embodiment of the invention can be provided that downstream at least one heat exchanger behind the first compressor is provided for cooling the compressed air. These heat exchangers can be advantageously exploited by the Secondary side of a heat exchanger in the cooling circuit the fuel cell or in a circuit for preheating of fluid flows is involved.

The Waste heat generated during compression can over a heat exchanger to the cooling circuit of the fuel cell be supplied. Since the operation of the compressor, i. H. the compression, especially takes place when delayed or braked, the fuel cell system runs in low load range and carries only a minimum heat output in the cooling circuit, so that during compression resulting waste heat without the risk of overloading the cooling circuit can be recorded; this carries more likely to keep the cooling circuit at temperature and the fuel cell system does not cool or the with required heating of the vehicle interior still enough heating heat is available. Alternatively, in the compression resulting waste heat in vehicles with fuel cell system with reforming / gas generation also for preheating fluid streams used in the reforming / gas generation heated Need to become.

Farther can be provided that at least one with the air reservoir connectable atomizing device for atomization of fluids is provided. In this case, for example, a sputtering device as moistening device for moistening the air mass flow with water and / or to atomize a fuel be carried out the gas generation. Continue with the im Compressed air is a gas generating or reforming unit are supplied. In particular, a (catalytic) Burner, a gas purification unit (eg partial oxidation) or other components within or at the gas generating unit compressed air can be added.

In this embodiment of the invention, the compressed air stored in the air reservoir is used in a first embodiment for the realization of a moistening device. The high pressure level of the stored compressed air makes it possible, for example, to realize a two-substance nozzle for atomising water. The atomization of fluids other than water, especially in connection with a fuel cell system with gas generation and reforming, for example, by the atomization of methanol and ethanol (also in admixture with water) together with the stored air in a two-fluid nozzle, can be used advantageously. Another way of using the stored compressed air is in the operation of a (catalytic) burner within a gas generating system, so that in total for fuel cell systems with gas generation to achieve improved dynamics.

In a development of the invention is provided that continue a switching unit arranged in front of the cathode of the fuel cell for the division of the air mass flow into two partial flows and for supplying a partial flow to the anode of the fuel cell is provided.

The stored compressed air can in this embodiment of the invention also be used before starting the boot process (that is, without a compressor) in the fuel cell and piping accumulated and the startup obstructing water with relative high pressure by compressed air from the air reservoir to blow out what a faster and better start possible. The saved Compressed air can also be used for flushing or shutdown (= so-called purge or shutdown procedures) can be used, to dry the fuel cell system and the fuel cell stack blow. Next there is the possibility that within of the fuel cell system by cooling after the Parking the vehicle condensed water (in cold temperatures associated with the risk of freezing or freezing) successively (for example following the cooling curve while the night without starting the compressor) and thereby blow to prevent the freezing of water in the system.

In Another embodiment of the invention is provided that downstream behind the fuel cell at least one throttle element for generating an adjustable dynamic pressure is provided.

Thereby can store the air stored in the air storage at vehicle standstill (at the fuel cell bus, for example, stopping at a bus stop) be used for the sole supply of the fuel cell, wherein then the fuel cell to minimum load, d. H. very small Mass flows of the fluids air and fuel, is located. This has the advantage that when the vehicle is stationary (fuel cell system running) no disturbing compressor noise can be heard. The fuel cell system runs practically silent with the pressures from the air reservoir and the hydrogen tank.

in this connection there is still the possibility that in this operating condition the entire pressure level (anode and cathode), by increasing closing the throttle elements located on the output side of the fuel cell is raised, resulting in a significant increase in the U-I characteristic and thus leading to improved efficiency. The raising the entire pressure level is possible because both Fluid streams, ie hydrogen and air, come from tanks, their pressure level is much higher than the usual Operating pressure of the fuel cell, or air at a pressure level can be made that much higher as that which is the compressor of the fuel cell system can provide.

According to one Another embodiment of the invention is the second compressor is in operative connection with an expansion machine, that the Expansion engine in the operation of the vehicle the second compressor drives. It can be provided that the expansion machine downstream of the fuel cell is arranged so that the gases leaving the fuel cell are the expansion engine drive. Alternatively, it is provided that the expansion machine between the air reservoir and the fuel cell so arranged is that the compressed air emerging from the air reservoir, the expansion machine drives. In the latter alternative is also advantageous to bypass the air reservoir bypass to bypass The expansion machine provided a trouble-free To ensure operation.

at the described vehicle according to the invention it is possible using stored compressed air, the fuel cell system without battery or other power storage unit to start. This can be realized simply by the fact that the stored compressed air and stored in the hydrogen tanks Hydrogen via a switchable valve (at the start to be actuated) is released for the fuel cell is and in each case the cathode or anode is supplied. At the fuel cell itself can then be removed electrical power Be the start of the second compressor of the fuel cell system is used and this then after some time the complete supply the cathode of the fuel cell takes over. This means, that the vehicle in which installed such a system with compressed air storage is, could do without any kind of electricity storage, which saves a considerable amount of money (and possibly weight) Episode has.

The entire system is seen as a kind of "low-cost" hybrid system for fuel cell buses (also for rail vehicles), where you do not want to go the way of complex and expensive energy storage in brake energy reclamation, but still have the potential to use fuel (with Help of brake energy recuperation) and to use the stored energy in a different way than is the case with systems with electrical brake energy recuperation. As already described, such a system can in principle be constructed from components such as are used in the compressed air system of commercial vehicles (reciprocating compressor, air storage). It could theoretically also be provided, the air brake system or another To couple on the vehicle existing pneumatic system with the brake energy recovery system, ie that, for example, air masses can be exchanged with each other.

following The invention is based on an embodiment and associated drawings explained in more detail. Showing:

1 1 is a schematic view of a fuel cell powered vehicle having an air reservoir;

2 a schematic view of the vehicle 1 with an air flow during the filling of the air reservoir,

3 1 is a schematic view of the vehicle, wherein the fuel cell is supplied with air alone from the air reservoir,

4 FIG. 1 shows a schematic view of the vehicle from FIG. 1, wherein the supply of air to the fuel cell takes place from the air reservoir and through the second compressor,

5 1 is a schematic view of the vehicle of Figure 1, wherein the fuel cell is purged with air from the air reservoir,

6 a schematic view of the vehicle 1 during a startup process without compressors,

7 a schematic view of a vehicle with fuel cell drive and an expansion engine between the air reservoir and the fuel cell,

8th a schematic view of a fuel cell powered vehicle and an expansion engine behind the fuel cell,

9 another embodiment of a fuel cell vehicle with a gas generating unit and a catalytic burner, and

10 a further embodiment of a fuel cell vehicle with a gas generating unit.

each other corresponding parts are in all figures with the same reference numerals Mistake.

The embodiment in 1 shows a schematic representation of the on a common axis 1 sitting vehicle wheels 2 that with the electric drive 3 are connected. The first compressor 4 passing through a suction tract 5 With an integrated air filter sucks in and compressed outside air, is via a (not shown) coupling to the electric drive 3 with the vehicle wheels 2 connectable. The operative connection between the first compressor 4 and the vehicle wheels 2 is established when the (not shown) service brake of the vehicle is operated, so that the braking energy is used to generate compressed air. The first compressor 4 generated compressed air is via a first switching unit 6 an air storage 7 or the cathode 8.1 the fuel cell 8th fed. The first switching unit 6 can be designed so that a simultaneous line from the first compressor 4 incoming air mass flow to the air reservoir 7 and the fuel cell 8th not possible. Before the first switching unit 6 is a heat exchanger 11 to dissipate the heat generated during the compression of the compressed air in the cooling circuit of the fuel cell 8th arranged.

A second compressor 9 that by a compressor drive 17 , For example, an electric motor, is powered constantly with the fuel cell 8th connected and ensures their supply of air in normal operation. Between the second compressor 9 and the fuel cell 8th is a second switching unit 10 arranged, which makes it possible to divide the air mass flow and a partial current of the anode 8.2 and a partial flow of the cathode 8.1 the fuel cell 8th zuzulei th. Output side of the anode 8.2 and the cathode 8.1 the fuel cell 8th is a first throttle element 14 or a second throttle element 15 arranged to generate a dynamic pressure. It is also between the second compressor 9 and the second switching unit 10 an atomizing device 12 arranged, which is designed in the embodiment as humidifying. The anode 8.2 the fuel cell 8th is through a supply line 13 supplied with hydrogen.

2 shows the air flow when filling the air reservoir 7 , The from the intake tract 5 sucked air mass flow is through the first compressor 4 compressed and then over the heat exchanger 11 and the first switching unit 6 the air storage 7 fed.

3 shows the supply of the fuel cell 8th alone from the air storage 7 in which the compressed air from the air reservoir 7 over the first switching unit 6 , the atomizer 12 in which the air mass flow is humidified, and the second switching unit 10 the cathode 8.1 the fuel cell 8th is fed from the exhaust gases through the throttle elements 14 and 15 escape.

4 shows the supply of the fuel cell 8th from the air storage 7 and through the second compressor 9 , where the compressed air from the air Storage 7 over the first switching unit 6 and those through the second compressor 9 compressed air led together and then on the atomizer 12 in which the air mass flow is humidified, and the second switching unit 10 the cathode 8.1 the fuel cell 8th is fed from the exhaust gases via the throttle or the elements 14 and 15 escape.

In 5 become the anode 8.2 and the cathode 8.1 the fuel cell 8th with the compressed air from the air reservoir 7 flushed, with the compressed air from the air reservoir 7 first the first switching unit 6 and the atomizer 12 and then split into two sub-streams, one of which is the cathode 8.1 and one of the anode 8.2 the fuel cell 8th is forwarded. Subsequently, the exhaust gases escape via the throttle elements 14 . 15 from the anode 8.2 and the cathode 8.1 , In the atomizer 12 In this case, it is not mandatory for water atomization / humidification to take place.

6 shows a starting process without compressors, in which the anode 8.2 the fuel cell 8th solely from the pressure of the hydrogen tank (not shown) and the cathode 8.1 solely from the pressure of the air reservoir 7 over the first throttle element 14 , the atomizer 12 and the second throttle element 15 be fed. Here, the back pressure by appropriate adjustment of the throttle elements 14 and 15 which also causes a system pressure on the anode ( 8.2 ) and the cathode ( 8.1 ) of the fuel cell ( 8th ) is set.

7 shows a vehicle with a between air storage 7 and fuel cell 8th arranged expansion machine 16 that with the second compressor 9 so is in operative connection that the expansion machine 16 during operation of the vehicle, the second compressor 9 at least partially (supportive) drives.

8th shows a vehicle with one behind the fuel cell 8th arranged expansion machine 16 that with the second compressor 9 is so operatively connected that the expansion machine 16 during operation of the vehicle, the second compressor 9 at least partially (supportive) drives.

9 shows a further embodiment of a fuel cell vehicle with a gas generating unit 18 and a catalytic burner 19 , The catalytic burner 19 is compressed air from the air reservoir 7 fed. In the catalytic burner 19 For example, a retentate produced in the reforming of methanol to hydrogen can be catalytically combusted with air. The released heat can be used in various ways.

10 shows a further embodiment of a fuel cell vehicle with a gas generating unit 18 , The gas generating unit 18 or a component not shown here within the gas generating unit, such as a gas cleaning unit, compressed air from the air reservoir 7 fed.

The described storage system (air storage) is with other types of memories used in hybrid and fuel cell vehicles combinable (eg power storage and air storage).

At the air storage 7 may be provided a foreign refueling port, by means of which the air reservoir 7 can be loaded at standstill to z. B. one from the compressor 9 initiate independent startup.

1

axis

2

vehicle wheels

3

electric drive

4

first compressor

5

intake system

6

First switching

7

air storage

8th

fuel cell

8.1

cathode

8.2

anode

9

second compressor

10

Second switching

11

heat exchangers

12

atomizing

13

supply

14

first throttle element

15

second throttle element

16

expander

17

compressor drive

18

Gas generation unit

19

catalytic burner

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10013660 A1 [0004]
• - DE 10154047 A1 [0005]

Claims (15)

A fuel cell powered vehicle comprising a fuel cell powered by a fuel cell (10). 8th ) electric power supplied electric drive ( 3 ) for driving vehicle wheels ( 2 ) and one with the fuel cell ( 8th ) connected air supply device, the an air storage ( 7 ) for storing compressed air and one with a cathode ( 8.1 ) of the fuel cell ( 8th ) and with the air storage ( 7 ) connectable first compressor ( 4 ) for generating compressed air, characterized in that the first compressor ( 4 ) with at least one vehicle wheel ( 2 ) is connectable so that the vehicle wheel ( 2 ) the first compressor ( 4 ) while driving. Vehicle according to claim 1, characterized in that a first switching unit ( 6 ) is provided, through which the first compressor ( 4 ) at any time either with the cathode only ( 8.1 ) of the fuel cell ( 8th ) or only with the air storage ( 7 ) and that a second compressor ( 9 ), which is constantly connected to the cathode ( 8.1 ) of the fuel cell ( 8th ) connected is. Vehicle according to claim 1 or 2, characterized in that downstream of the first compressor ( 4 ) at least one heat exchanger ( 11 ) is arranged for cooling the compressed air. Vehicle according to claim 3, characterized in that a secondary side of the heat exchanger ( 11 ) in a cooling circuit of the fuel cell ( 8th ) is included. Vehicle according to claim 3 or 4, characterized in that a secondary side of the heat exchanger ( 11 ) is included in a circuit for preheating fluid streams. Vehicle according to one of the preceding claims, characterized in that at least one with the air reservoir ( 7 ) connectable atomizing device ( 12 ) is provided for atomization of fluids. Vehicle according to claim 6, characterized in that the atomizing device ( 12 ) is designed as a moistening device for moistening the air mass flow with water. Vehicle according to claim 6 or 7, characterized in that the atomizing device ( 12 ) for atomizing a fuel in gas production. Vehicle according to one of claims 6 to 8, characterized in that a gas generating unit or a catalytic burner provided on the gas generating unit Compressed air from the air reservoir can be fed. Vehicle according to one of the preceding claims, characterized in that one in front of the cathode ( 8.1 ) of the fuel cell ( 8th ) arranged second switching unit ( 10 ) for dividing the air mass flow into two partial flows and for supplying a partial flow to an anode ( 8.2 ) of the fuel cell ( 8th ) is provided. Vehicle according to one of the preceding claims, characterized in that downstream of the fuel cell ( 8th ) at least one throttle element ( 14 . 15 ) is provided for generating an adjustable dynamic pressure. Vehicle according to one of claims 2 to 11, characterized in that the second compressor ( 9 ) with an expansion machine ( 16 ) is operatively connected in such a way that the expansion machine ( 16 ) during operation of the vehicle the second compressor ( 9 ) drives. Vehicle according to claim 12, characterized in that the expansion engine ( 16 ) downstream of the fuel cell ( 8th ) is arranged so that from the fuel cell ( 8th ) escaping gases the expansion machine ( 16 ). Vehicle according to claim 12, characterized in that the expansion engine ( 16 ) between the air storage ( 7 ) and the fuel cell ( 8th ) is arranged so that from the air reservoir ( 7 ) escaping compressed air the expansion machine ( 16 ) drives. Vehicle according to claim 14, characterized in that for filling the air reservoir ( 7 ) a bypass for bypassing the expansion machine ( 16 ) is provided.