WO2003015202A1 - Fuel cell systems with a reaction-gas pressure regulating system or volume flow regulating system in addition to a fuel supply and removal system using a reaction gas volume flow - Google Patents

Abstract

The invention relates to a device and a method enabling the reaction gas pressure in fuel cells of a fuel cell system to remain constant even when high fluctuations of the reaction gas volume flow or high fluctuations occur in the decrease in performance by an electric consumer. A timed reaction gas inlet valve is used in order to guarantee pressure stability. The invention also relates to devices and methods for regulating the economy of fuel cell systems in difficult conditions of unforeseeable changes in reaction gas volume flows and in unforeseeable changes involving the decrease in performance by an electric consumer.

Description

 Fuel cell systems with reaction gas pressure control or volume flow control as well as supply and disposal of operating fluids using a reaction gas volume flow

Fuel cell systems supply electrical consumers with electrical power. The electrical power that can be obtained from the fuel cell system depends on the one hand on the structural design of the fuel cell system, that is, above all on the number and size of the individual fuel cells or the fuel cell stack, and on the other hand on the operating conditions. These primarily include reaction gas pressures or volume flows, operating temperature and water balance in the fuel cells.

The design of the fuel cell system determines the maximum performance that can be achieved. The power that can actually be drawn by an electrical consumer at a specific time varies depending on the operating conditions. If the electrical consumer has high performance requirements, the volume flow to be supplied to the fuel cells must be increased up to the theoretically possible maximum value.

In order to achieve maximum efficiency, the fuel cells must be kept at an optimal moisture content. The membranes of polymer electrolyte membrane fuel cells must always have a high water content in order to ensure good proton conductivity, since otherwise the fuel cell performance drops. However, if there is too much water in the fuel cells, the electrodes will flood and the achievable performance will also decrease.

With constant or only slowly changing power requirements of the electrical consumer to be supplied with electrical power, it is generally unproblematic to determine the reaction gas pressure or volume flow of the fuel cell. len-Systems to adapt to the respective requirements. The supply of dampening water for the membranes and, if necessary, cooling water, as well as the removal of excess water can be solved to some extent satisfactorily with constant or only slowly changing operating states of the fuel cell system.

So far, however, there is no satisfactory solution for cases in which the performance requirements can be subject to unpredictable fluctuations.

In the event of unforeseeable strong fluctuations in the power requirements of the electrical consumer, the reaction gas volume flows of the supplying fuel cell system are also subject to the same fluctuations. Often, when supplying fuel cells in stationary or mobile applications, it must be possible to provide high gas volume flows at partly very low pressures for the supply on the one hand, and on the other hand, this gas volume flow must often be able to be regulated or adjusted in the range of a few milliseconds in order to prevent unacceptable pressure overshoots or pressure undershoots in the system to avoid. In addition, there is a need for powerful, but at the same time compact and light gas supply devices, particularly in mobile applications.

Piston or diaphragm pressure reducers are currently usually used for pressure control, but are unsatisfactory in terms of volume capacity, pressure accuracy, pressure reproducibility and control speed in applications that require rapid changes in the reaction gas volume flow, and are also large and heavy. The latter has a disadvantageous effect in particular in mobile applications, such as in a motor vehicle.

To supply the polymer electrolyte membranes of fuel cells with moisture, it is known to feed water into a reaction gas stream and to have the reaction gas transport it to the polymer electrolyte membranes. On the one hand, there is the problem that the dampening water is often not distributed satisfactorily in the reaction gas volume flow and only an uncontrollable proportion of the dampening water reaches the membranes. On the other hand, the amount of dampening water depends on the operating conditions of the fuel cell system. In particular, when the operating conditions change unpredictably quickly, the change in the humidification state can often not take place quickly enough.

In addition, water is formed on the cathode side in fuel cells. This water and any excess membrane dampening water and / or cooling water must be removed from the fuel cells in order to prevent the electrodes from flooding. There are currently several options for expelling water from the fuel cells, e.g. the mutual charging of the fuel cells with gas in order to achieve an expulsion of water droplets by changing flow conditions. The equipment required consists of one or more valves for gas flow deflection and the necessary control electronics. Another possibility is to cyclically flush the cell with gas (reaction gas) into the environment. Valves and control elements are also required for this. In addition, the loss of gas sometimes leads to a drastic deterioration in the overall efficiency of the fuel cell system. The safety-related problems caused by the release of gas into the environment can also only be solved with additional equipment. An alternative is to create a gas vacuum in a container with a compressor and to flush it cyclically into this container with reaction gas. The purge gas could be returned to the fuel cell using the compressor. Here too, a great deal of equipment is required. In addition, a particular disadvantage in the case of unpredictably changing operating conditions is that the required extent of water removal is difficult to determine and to control.

The object of the present invention is therefore to provide a method for regulating the pressure of a reaction gas in a fuel cell system, which allows the reaction gas pressure to be regulated with high accuracy and to avoid pressure fluctuations in the system even in the case of rapid changes in volume flow. The object of the present invention is also to provide a fuel cell system which is designed for the method according to the invention for regulating the pressure.

It is also an object of the present invention to provide a method for humidifying a fuel cell system in which the humidification water 105 is distributed efficiently in a reaction gas volume flow.

Another object of the present invention is to provide a fuel cell system which is designed for the humidification method according to the invention.

It is also an object of the present invention to provide a method for expelling excess water from a fuel cell system, in which the more hydrogen is automatically used in the fuel cell system, the greater the efficiency of water removal.

Another object of the present invention is to provide a fuel cell system which is designed for the method for expelling water.

It is also an object of the present invention to provide a method for adapting the power of a fuel cell power system to changing power requirements of an electrical consumer, in which the required changes in the reaction gas volume flow do not lead to pressure fluctuations in the fuel cell system.

It is also an object of the present invention to provide a fuel cell power system which is designed for the power adjustment method according to the invention.

The object is achieved by the fuel cell system according to claim 1 and the method for regulating the pressure according to claim 13.

130 The object is further achieved by the fuel cell system according to claim 19 and the method for dispersing water in a reaction gas according to claim 22.

The object is also achieved by the fuel cell power system and the method for adapting the power of a fuel cell power system to changing power requirements of an electrical consumer according to claims 24 and 26.

The dependent claims relate to advantageous developments of the invention, the features specified in the dependent claims, individually or in any combination, representing advantageous developments of each of the subjects specified in the independent claims.

For the pressure control according to the invention, the fuel cell system, preferably polymer electrolyte membrane / fuel cell system, has the following features: at least one fuel cell stack, a reaction gas supply with a high pressure area and a low pressure area to the fuel cell stack, - a device for controlling the pressure in the Low pressure area of the reaction gas supply with a clocked reaction gas inlet valve, ie a two-position reaction gas inlet valve of the type; a measuring point for measuring the pressure or a pressure-correlated measured variable in the low pressure range of the reaction gas

Supply, a control and regulating unit for recording and evaluating the pressure or the pressure-correlated measured variable and for controlling the reaction gas inlet valve depending on the pressure or the pressure-correlated measured variable.

The term "a" should always be understood as "at least one". A fuel cell stack typically has about 5 to 60 fuel cells, although the number can vary within a wide range, and the fuel cell system can have only one or a very large number of fuel cell stacks. In principle, however, the invention can be used for any number of individual fuel cells, for example also for only one individual fuel cell, or for any number of fuel cell stacks.

170 The reaction gas inlet valve is preferably arranged such that it separates the high pressure area and that of the reaction gas supply. If the valve is closed, the fuel cell system is also sealed off from the environment. A separate shut-off valve is not necessary because the reaction gas inlet valve also acts as a shut-off valve.

175

The pressure in the high pressure area is typically up to 200 bar, but can also be higher. As a rule, however, it is below this, for example up to 50 bar, typically about 5 bar. The pressure in the low pressure area of the fuel cell system is system-dependent and is typically in the range from 180 a few 100 mbar to a few bar. A common pressure is about 2 bar.

According to the invention, a reaction gas pressure or a pressure-correlated measured variable is regulated. Pressure-correlated measurement variables are, for example, the reaction gas volume flow or the partial pressure of the reaction gas. The invention is described below on the basis of the measurement of the reaction gas pressure in the low pressure range, but this should not be understood as a limitation of the invention. The measurement of pressure-correlated measured variables and activation of the reaction gas inlet valve depending on the measured value of the pressure-correlated measured variable represents an equivalent alternative.

190

Typically the reaction gas, the pressure of which is measured, is the fuel gas, e.g. Hydrogen, but also in the oxidant supply, the control according to the invention can be carried out, provided the oxidant is supplied under pressure.

195 The pressure and / or volume flow control according to the invention comprises the following steps: continuous or regular measurement of the pressure or a pressure-correlated measurement variable in the low-pressure region of the reaction gas supply,

200 - continuous or regular recording or evaluation of the pressure or the pressure-correlated measured variable by comparing the actual value of the pressure or the pressure-correlated measured variable with a predetermined target value of the pressure or the pressure-correlated measured variable typical of the fuel cell system,

205 - Actuation of the reaction gas inlet valve in dependence on the pressure or the pressure-correlated measured variable in such a way that the reaction gas volume flow per unit of time flowing through the reaction gas inlet valve is increased if the actual value of the pressure or the pressure-correlated measured variable is below the predetermined target value, and is reduced,

210 if the actual value of the pressure or the pressure-correlated measured variable is above the predetermined target value.

The measurement is carried out using conventional sensors known to those skilled in the art for this purpose.

215

The measured value of the, for example, reaction gas pressure is recorded by a conventional control and regulation unit and compared with the predetermined target value. When power is drawn by an electrical consumer, the actual value drops below the target value of the pressure or the pressure-correlated measured variable,

220 and a too low value is measured. If the measured value is too low, it is increased by an increased admission of reaction gas, that is to say an increase in the reaction gas volume flow flowing through the reaction gas inlet valve per unit of time. This is done by a suitable control of the clocked reaction gas inlet valve. However, if the measured value is too high, it will

225 by a reduced admission of reaction gas, that is to say by a reduction in the reaction gas volume flow flowing through the reaction gas inlet valve per unit of time. This is also done by a suitable control of the reaction gas inlet valve. 230 The regulation of the reaction gas volume flow flowing through the clocked reaction gas inlet valve per unit of time into the low pressure range is preferably carried out by pulse-modulated or frequency-modulated control of the reaction gas inlet valve. A two-point controller is used as the control and regulating unit for the pulse-modulated control, and a for the frequency-modulated control

235 continuous controller used.

With pulse modulation, pulse times in which the reaction gas inlet valve is open alternate with pause times in which the reaction gas inlet valve is closed. A constant reaction gas volume flows during the pulse times.

240 flow into the fuel cell system, no reaction gas flows in during the break times. Consequently, the reaction gas volume flow flowing through the reaction gas inlet valve per unit of time is greater, the longer the pulse times and accordingly the shorter the remaining pause times. The reaction gas volume flow is varied here by suitable variation

245 the ratio of pulse times to pause times between the pulse times.

With frequency modulation, on the other hand, the pulse times during which the reaction gas inlet valve is open and a constant reaction gas volume flow flows into the 250 fuel cell system are constant. The pause time between two pulse times is varied, in which the valve is closed and no reaction gas can flow in. The shorter the pause times, the higher the control frequency, the greater the reaction gas volume flow flowing through the reaction gas inlet valve.

255

In addition, a reaction gas outlet valve can be provided in the low-pressure area of the reaction gas supply, which can also be controlled by the control and regulating unit as a function of the pressure or the pressure-correlated measured variable. The reaction gas outlet valve enables a considerably faster pressure reduction in the low pressure range than this by simply keeping the reaction gas inlet valve closed while simultaneously consuming reaction gas through the fuel cells, so it essentially has a safety function. The reaction gas outlet valve can be any valve, for example a continuously controllable valve or a clocked valve such as the reaction gas inlet valve. The control can take place, for example, in such a way that a certain limit value of the pressure in the low pressure range is specified, which may not be exceeded. Should it still be exceeded, the reaction gas outlet valve is activated and opened until the limit is undershot.

'' O

The reaction gas inlet valve is a valve that has very short switching times. Solenoid valves and piezo valves are preferred which, on the one hand, react very quickly and, on the other hand, only have two switch positions, so that when the valve is opened the maximum possible amount of gas can flow through the valve, with this amount of gas flowing until the valve closes. The accuracy and reproducibility of the pressure setting does not depend on the inertia of the valve, but only on the inertia of the control loop elements used in the system. Since the control and regulation takes place electronically, i.e. without inertia, the pressure is also set very quickly.

280

The low-pressure region of the reaction gas supply can be designed as a distributor line for reaction gas, which leads the reaction gas to the fuel cell stacks and finally to the individual fuel cells. Alternatively, the low-pressure area can also be designed as a low-pressure space, from which all individual fuel cells of a stack are supplied with reaction gas. For example, the low-pressure space can be the anode space of a fuel cell stack, from which fuel gas flows into the individual fuel cells of the stack.

The reaction gas inlet valve can be integrated 290 into the reaction gas supply such that its drive is also accommodated in the reaction gas supply. This has the advantage that no additional sealing systems are required. The integrated installation is possible both in the high-pressure area and in the low-pressure area of the reaction gas supply, the low-pressure area being able to be designed both as a distributor line and as a low-pressure space. Is the low 295 pressure area formed as a low pressure space, the reaction gas inlet valve separates the high pressure area from the low pressure space of the fuel cell stack. In the case of a plurality of fuel cell stacks in a fuel cell system, each low-pressure chamber of a fuel cell stack preferably has a reaction gas inlet valve which separates the low-pressure chamber of the fuel cell stack in question

300 high pressure area separates. In the case of a distributor line for the reaction gas, a reaction gas inlet valve can also be integrated directly on each fuel cell stack. In this case, the distribution line represents the high-pressure area, and, as with the variant with low-pressure space, there is a separate control and regulating unit for the respective reaction gas inlet for each fuel cell stack.

305 valve required. The reaction gas inlet valve separates the high pressure area from the low pressure area of a fuel cell stack. Alternatively, the reaction gas inlet valve can also be integrated in such a way that it opens the reaction gas supply for several or all fuel cell stacks together upstream from a low-pressure region (distributor line) common to all fuel cell stacks.

310 net or interrupts.

The reaction gas outlet valve including the drive can also be easily inserted into the reaction gas supply, e.g. in a low pressure room, so that no additional sealing systems are required.

315

For pressure and volume flow control in small applications, i.e. When powering laptops, telephones, flashlights etc., for example, a fuel cell system with a piezo valve as a reaction gas inlet valve is particularly suitable, with a low pressure chamber as a low pressure area of the reaction gas

320 supply and with a reaction gas inlet valve built into the low-pressure chamber including its drive. The system is particularly simple to set up with a high power density. Even if it is an ideal solution especially for miniaturized gas supply systems, it is by no means restricted to this area of application, but can also be used in any other

325 fuel cell system of any size can be used advantageously. Fuel cell systems with pressure control according to the invention have a number of advantages over fuel cell systems with conventional pressure control: they allow extremely fast, precise and reproducible pressure control

330 tion of the reaction gas in the low pressure area of the fuel cell system. High reaction gas volume flows can be provided for supply at low pressures, and this reaction gas volume flow can be opened and closed almost without inertia in order to avoid impermissible pressure overshoots or pressure undershoots in the fuel cell system. Even if

335 very fast changes in the inflowing reaction gas volume flow are required, pressure fluctuations in the low pressure range can be almost avoided.

By using a clocked reaction gas inlet valve, which is comparatively light on the one hand and on the other hand makes the use of a separate shut-off valve unnecessary, as well as possibly by assigning a reaction gas inlet valve to a fuel cell stack and integrating the reaction gas inlet valve its drive in the high or low pressure range can achieve significant weight savings 345 without sacrificing power density.

To ensure efficient moistening of the polymer electrolyte membranes of the fuel cells at any desired output of a fuel cell system, the fuel cell system according to the invention has a reaction gas supply

350 guide to the fuel cell stack or the fuel cell stacks arranged throttle device, which separates the high pressure region and the low pressure region of the reaction gas supply during operation of the fuel cell system, and an upstream from the throttle device or directly into the throttle device opening into the reaction gas supply Water supply on. The throttle device

355 is, for example, a nozzle or an aperture, preferably a convergent nozzle.

The arrangement of the throttle device such that it separates the high-pressure region and the low-pressure region of the reaction gas feed means that the upstream inlet of the throttle device is at a high pressure level. 360 veau pi and the downstream outlet of the throttle device at a lower pressure level p. The flowing reaction gas enters the throttle device at a pressure p1 and is expanded to the pressure of the low-pressure region p2 when it leaves the throttle device. At the narrowest cross section of the throttle device, the reaction gas pressure is preferably at least equal to the critical one

365 pressure or higher.

When a gas flows through a convergent nozzle, its pressure decreases and the flow velocity increases. The pressure of the gas can decrease so far that the critical pressure Pkπt is reached in the narrowest cross section of the nozzle. 370 This is given by:

wobei Pi = der Druck vor der Düse ist. Ist der Druck nach der Düse kleiner als dieser kritische Druck, also pknt > p₂, so wird die restliche im Gasstrahl der Düse enthaltene 380 Druckenergie im Moment des Ausströmens unter Entropiezunahme durch ein Aufweiten des Gasstrahlkegels umgesetzt. Das Gas wird "überkritisch" entspannt.

where Pi = the pressure in front of the nozzle. If the pressure after the nozzle is lower than this critical pressure, i.e. pknt> p ₂ , the remaining 380 pressure energy contained in the gas jet of the nozzle is converted at the moment of the outflow with an increase in entropy by widening the gas jet cone. The gas is expanded "supercritically".

According to the invention, water is in the high-pressure region of the reaction gas supply between reaction gas inlet valve and inlet of the throttle device or in

385 area of the throttle device itself (before its narrowest point) fed into the reaction gas feed. The water is entrained by the flowing reaction gas and exits the throttle device with it. The supercritical expansion of the reaction gas volume flow as it enters the low-pressure region of the reaction gas feed leads to a breakdown of the water carried along

390 droplets, i.e. to disperse the water in the reaction gas. The dispersion is generally carried out more thoroughly the greater the difference between the narrowest cross section of the throttle device and the pressure after the nozzle. Typically, the water entrained in the reaction gas forms a spray cone when it emerges from the throttle device. The humidification 395 tion water is now dispersed in the flowing reaction gas and is distributed by it very evenly to all individual fuel cells of the fuel cell stack or the fuel cell stack. The membranes of all individual fuel cells are moistened very evenly.

400 Due to the arrangement of the throttle device immediately after the reaction gas inlet valve and the supply of water in the high pressure area, an increased supply of reaction gas also leads to an increased supply of dampening water. The humidification of the fuel cells is therefore at an increase in the load with which an increase in the

405 humidification needs, automatically more intensive. Due to its fine distribution, preferably as an aerosol, the dispersed water can also partially evaporate in the reaction gas and thus lead to cooling of the fuel cells.

The metering is preferably carried out via a pump from a water reservoir.

410

The process according to the invention for dispersing water in a reaction gas can be used for any reaction gas which is supplied under pressure. It is independent of the type of reaction gas inlet valve used and the type of pressure control in the low pressure range, so it can be used to advantage in any 415 fuel cell system.

However, it is preferred to use the type of dispersing water according to the invention in a reaction gas in fuel cell systems which have one or more of the features described above in connection with the pressure control 420 according to the invention, or to combine the method for dispersing water with process features as described above for the method for pressure control according to the invention.

It is particularly advantageous to provide the throttle device after a clocked reaction gas inlet valve, not after a continuously regulating reaction gas inlet valve. The clocked reaction gas inlet valve always has the same fluid mechanics during the opening time of the valve Conditions under which the system can be optimized with regard to the efficiency of the atomization and distribution of the water.

430

On the one hand, polymer electrolyte membrane fuel cells have to be moistened in order to always ensure optimum conductivity of the polymer electrolyte membrane, on the other hand, however, water also arises during the fuel cell reaction, which must be removed from the fuel cells in order to flood the electrodes

Prevent 435. According to the invention, the removal of excess water from the fuel cell system is achieved by utilizing the kinetic energy contained in the reaction gas volume flow. For this purpose, the fuel cell system in a reaction gas supply to the fuel cell stack or the fuel cell stacks has a gas jet with a driving nozzle, inlet to the gas

440 suction and trap nozzle, as well as a reaction gas recirculation from the fuel cell stack or the fuel cell stacks. The reaction gas recirculation opens into the inlet for gas intake of the gas emitter.

The reaction gas recirculation is advantageously designed as a manifold for unused reaction gas from the fuel cells.

In the method for expelling water from a fuel cell system, the reaction gas is passed through any reaction gas inlet valve as a propellant jet through the gas jet, which the high pressure area and the low pressure

450 separates the pressure range of the reaction gas supply, fed into the reaction gas supply and passes the fuel cell stack or the fuel cell stack. Unused reaction gas is fed back into the gas jet by a reaction gas return, a pressure which is lower than that being generated in the reaction gas return by the suction effect of the gas jet

455 Pressure in the low pressure area of the reaction gas supply. With the unused reaction gas drawn in, water is also sucked out of the fuel cells and fed into the reaction gas recirculation. A water separator is preferably provided in the reaction gas recirculation in order to prevent the sucked-in water from entering the gas jet and thus the reaction gas supply.

460 tion arrives. Incomplete water separation is not harmful. That still Water contained in the recycled unused reaction gas can be used again to moisten the polymer electrolyte membranes of the fuel cells.

465 The gas jet separates the high-pressure area and the low-pressure area of the fuel cell system and can thus use the entire pressure energy contained in the inflowing reaction gas volume flow for gas suction, whereby theoretically an absolute vacuum can be achieved. External energy or a separate water removal system with moving parts, valves or other control

470 ganen are not necessary. The fuel cell system with gas jet for vacuum generation in the reaction gas return is rather simple and compact in structure and maintenance-free. A particular advantage lies in the synchrony between fuel cell performance and water removal efficiency. With higher performance of the fuel cell system, a higher reaction gas volume flow is required.

475 loaned, and since more hydrogen is consumed, more water is simultaneously formed in the fuel cells. However, a higher reaction gas volume flow means at the same time an increased suction power of the gas jet and thus a more effective removal of excess water from the fuel cells. Flooding of the electrodes is thus reliably avoided even under high loads.

480

Another advantage of this system is that it enables the fuel cells to operate in an open, continuous flow without gas loss, because unused reaction gas is mixed with the newly supplied reaction gas in the gas emitter and used again.

485

The arrangement with reaction gas recirculation and gas jets for expelling water from the fuel cells can be used advantageously in any fuel cell system. It is used with particular advantage in fuel cell systems which have one or more of the features described above in connection with the pressure control according to the invention and / or with the dispersion of water in a reaction gas according to the invention. If the reaction gas inlet valve is a pulsed valve, such as a solenoid valve or 495 a piezo valve, the maximum reaction gas volume flow flows in when the valve is open, so that full pressure is applied to the downstream gas jet when the valve is open. The gas jet can therefore always be operated at optimum operating performance and provide its maximum suction power.

500 The specified water expulsion from the fuel cells can also advantageously be combined with the dispersion of water in a reaction gas according to the invention, regardless of the type of pressure control. In this case, the driving nozzle of the gas jet acts as a throttle device, and the dampening water is fed upstream from the driving nozzle or in the driving nozzle into the reaction gas supply.

505 fed in. The water supplied increases the motive mass flow and therefore leads to an improvement in the vacuum which can be achieved in the reaction gas recirculation.

The systems according to the invention for regulating the reaction gas volume flow or

510 pressure control, for dispersing water in a reaction gas volume flow and for expelling excess water from the fuel cells can also be implemented together in a single system. Such a fuel cell system allows pressure fluctuations in the low-pressure region of the fuel, even with rapidly changing reaction gas volume flows.

515 cell system, so it can react to rapidly changing performance requirements of an electrical consumer without causing excessive or excessive pressure drops in the system. In addition, the fuel cells can be moistened under the conditions of constant oversupply with water and thus guaranteed optimal moistening of the membranes.

520 are driven without the anode side of the membranes being covered with water droplets, since excess water is continuously optimally expelled. This also enables stable operation of the fuel cell system with regard to the water balance, with only a minimum of sensors being required.

525 A change in the electrical power to be supplied by a fuel cell power system, as is required when changing the power requirements of an electrical consumer, for example a motor vehicle traveling at changing speeds, requires a change in the

530 supplying reaction gas volume flow. However, there should be no pressure fluctuations in the fuel cell area. According to the invention, this is achieved by supplying the fuel cells with a certain amount of reaction gas, which is dependent on the desired output of the electrical consumer. With high performance requirements, a high reaction gas volume

535 fed in stream, less reaction gas is fed in if lower power requirements are desired. The reaction gas volume flow is fed in via a reaction gas inlet valve, which can be a clocked valve or a continuously regulating valve. The pressure is regulated by power electronics in such a way that the fuel cells always have so much electrical power

540 stung that the pressure in them is kept constant. The power electronics react very quickly to pressure fluctuations in the system, so that the reaction gas inlet valve does not have to meet high demands regarding pressure accuracy and reproducibility as well as control speed. It is therefore not necessary to use a clocked valve,

545 if such a valve can also be used advantageously.

A fuel cell power system according to the invention, which is designed for variable power requirements of an electrical consumer, has:

550 - at least one fuel cell stack, a consumer electrically connected to the fuel cell stack, a reaction gas supply to the fuel cell stack with a reaction gas inlet valve, a high pressure region and a low pressure region, a device for specifying a target value of a reaction gas Volume-

555 Stroms, a device for detecting the target value of the reaction gas volume flow and for controlling the reaction gas inlet valve in accordance with the target value specification (control unit), a measuring point for continuous or regular measurement of the pressure 560 or a pressure-correlated measured variable in the low-pressure area of the reaction gas supply, a device for recording and evaluating the pressure or the pressure-correlated measured variable and for releasing the fuel cell output corresponding to the pressure or the pressure-correlated measured variable to the electrical Consumers (power controller), and a device for setting the target power of the electrical consumer (power electronics).

The target value specification for the reaction gas volume flow to be supplied takes place in each case

570 in the manner of the electrical consumer by operating a suitable device, for example a step or slide switch, or by operating the accelerator pedal in a motor vehicle. The specified target value is recorded by a control unit which controls the reaction gas inlet valve in accordance with the target value specification, i.e. the reaction gas inlet valve is opened as long as

575 that a reaction gas volume flow corresponding to the predetermined target value can flow into the low-pressure region of the reaction gas supply. In the low-pressure area of the reaction gas supply, the pressure or a pressure-correlated measured variable is measured continuously or regularly and recorded by a power controller. The power controller compares the actual value of the pressure or the pressure

580 measured value with a predetermined target value of the pressure or the pressure-correlated parameter, which is typical of the system, and releases fuel cell power to the electrical consumer until the actual value matches the target value. The setting of the power of the electrical consumer, for example of a motor vehicle engine, is carried out via power electronics which

585 fuel cell system takes the fuel cell power released by the power controller.

Alternatively, the desired power or another electrical quantity, for example the voltage or the current, can also be specified. In this case, the fuel cell power system according to the invention 590 has a device for pre-setting a setpoint value for a reaction gas volume flow. would give a desired target value of the corresponding electrical quantity, and instead of the device for detecting the reaction gas volume flow and for controlling the reaction gas inlet valve according to the target value specification

595 be it has a device for determining the actual value of the electrical variable and a device for comparing the determined actual value with the predetermined target value and for controlling the reaction gas inlet valve in accordance with the target value specification. The actual value of the electrical quantity can be determined by the power electronics or another measuring device. In the control

600 times the determined actual value is compared with the specified target value, e.g. By means of a standard regulator, and the reaction gas inlet valve is controlled accordingly, i.e. the reaction gas inlet valve is opened when the target value is not reached and closed as long as it is reached.

605 In the drawings:

1 shows a fuel cell system with pressure control according to the invention and a low-pressure region of the reaction gas supply formed as a reaction gas distributor line,

610

2 shows a fuel cell system with a fuel cell stack and with the pressure control according to the invention and a low-pressure area of the reaction gas supply designed as a low-pressure chamber,

615 FIG. 3 shows a fuel cell system as in FIG. 2, but with two fuel cell stacks and associated low-pressure spaces,

4 shows a schematic diagram for pulse-modulated reaction gas inlet valve control,

620 FIG. 5 shows a schematic diagram for frequency-modulated reaction gas inlet valve control,

6 shows a partial area of a fuel cell system with water dispersion according to the invention in the reaction gas supply, 625

7 shows a partial area of a fuel cell system with an arrangement for expelling water from the fuel cells,

8 shows a fuel cell system as in FIG. 1, but with an arrangement for expelling 630 water,

9 shows a partial area of a fuel cell system with a water dispersion according to the invention and an arrangement for expelling water,

635 FIG. 10 shows a fuel cell power system according to the invention, which is designed for variable power requirements of an electrical consumer.

1 shows a fuel cell system 1 with pressure control according to the invention. A reaction gas, such as hydrogen, becomes the fuel cell system

640 fed. It flows from a high-pressure area 5 of the reaction gas supply via a reaction gas inlet valve 8 into the low-pressure area 6 of the reaction gas supply. The low-pressure region 6 of the reaction gas supply is designed as a distributor line which distributes the reaction gas to the individual fuel cell stacks and the individual fuel cells 3 which form the stacks. In Fig.

645 1, two fuel cell stacks 2, 2 'are shown, but there may also be more or fewer fuel cell stacks. A measuring point 9 for measuring the pressure of the reaction gas is located in the low pressure region 6 of the fuel cell system. Alternatively, a pressure-correlated measurement variable can also be measured, for example the partial pressure of the reaction gas or the reaction gas volume.

650 menstrom. The measured variable is recorded in a control and regulating unit 10 and the measured value is compared with the target value of the measured variable specified for the system. If the measured value is below the target value, the reaction gas inlet valve 8 or the drive 16 of the reaction gas inlet valve 8 is activated and the reaction gas inlet valve is opened, so that reaction gas from the

655 high pressure area 5 flows into the low pressure area 6. The reaction gas inlet valve 8 is a clocked valve, ie a valve with only two switching positions. Examples include a solenoid valve and a piezo valve. The control of the Onsgas inlet valve can be pulse modulated as shown in FIG. 4 or frequency modulated as shown in FIG. 5. Is the measured at measuring point 9

660 sene value for the pressure or the pressure-correlated measured variable at or above the specified target value of the system, the reaction gas inlet valve remains closed and is only opened again when the measured value drops below the target value of the system due to the consumption of reaction gas. In order to enable rapid pressure reduction, the system shown in FIG. 1 additionally has a

665 onsgas exhaust valve 11 with drive 17, through which reaction gas can be released from the low pressure region 6. The reaction gas outlet valve 11 is also controlled by the control and regulating unit 10. It can be a clocked valve such as the reaction gas inlet valve 8, or it can also be a continuously controlled valve. The reaction gas outlet valve 11 is activated on

670 most expediently such that an upper limit value is specified for the pressure (or partial pressure, etc.) of the reaction gas prevailing in the low pressure region 6 and the reaction gas outlet valve 11 is activated and opened as long as this limit value is exceeded.

675 FIGS. 2 and 3 also show fuel cell systems with pressure control according to the invention. Here, however, the low-pressure region 6 of the reaction gas supply is designed as a gas space into which the reaction gas flows from the high-pressure region 5 when the inlet valve 8 is open. The reaction gas flows from the gas space 6 into the reaction gas flow fields 14 of all individual fuel cells 3 of the

680 fuel cell stack 2. The reaction gas inlet valve 8, which separates the high-pressure region 5 from the low-pressure region 6, is accommodated together with its drive 16 in the low-pressure space, so that no separate sealing is required. The low-pressure space 6 is arranged on a side surface of the fuel cell stack 2. On another side surface, in the embodiment shown on the

685 opposite side surface, a space 18 is provided for the other reaction gas, from which this reaction gas flows into reaction gas flow fields 14 '. The measurement of the reaction gas pressure or the pressure-correlated measured variable at the measuring point 9 and the actuation of the valve 8 via the actuation and control unit 10 is carried out as in FIG. 1. In the embodiment shown in FIG. 690 form, no reaction gas outlet valve 11 is shown, but such a valve can of course also be provided in this embodiment.

FIG. 3 shows a fuel cell system 1 of the same type as shown in FIG. 2, but with two fuel cell stacks 2, 2 each of which has its own low-pressure space.

695 me 6, 6 ', reaction gas inlet valves 8, 8', measuring points 9, 9 'and control and regulating units 10, 10' are assigned. However, they have a common high pressure area 5 of the reaction gas supply. It is also possible to have more than two fuel cell stacks, in which the low-pressure area of the reaction gas supply is designed as a low-pressure area, from a high-pressure area 5 with reaction

700 gas can be supplied.

The arrangement of the reaction gas inlet valve directly on the fuel cell stack and its integrated installation, i.e. Installation including drive, in the reaction gas supply is possible regardless of the presence of a low pressure chamber and also in the case of distribution lines. The reaction gas inlet valve can both in

705 the high pressure area as well as integrated into the low pressure area.

Fig. 4 shows the gas flow through a clocked valve such as the reaction gas inlet valve 8 with pulse-modulated control of the valve. The basic sequence Ti der

710 pulse-modulated control is composed of a pulse time T ₂ during which the valve is open and a pause time T ₃ during which the valve is closed. In the case of a valve with only two switch positions, as is used according to the invention for pressure control as a reaction gas inlet valve, flows during the entire duration of the pulse times, which are shown in FIG.

715 th areas are indicated, the maximum possible reaction gas volume flow through the valve. The reaction gas volume flow is completely interrupted during the pause times. The variation of the volume flow flowing through the valve during the time unit Ti takes place through the variation of the time ratio T ₂ / T ₃ .

720

5 shows the gas flow through a clocked valve such as the reaction gas inlet valve 8 with frequency-modulated control of the valve. The valve is ner control frequency 1 / Tι controlled, where Ti is the sum of the pulse time T ₂ (hatched in Fig. 5) and the pause time T ₃ . During the pulse times

725 the valve is opened, and the maximum possible reaction gas volume flow flows through the valve into the low-pressure region of the reaction gas supply. During the pause times, the valve is closed and no reaction gas can flow in. The duration of the pulse times is constant, but the duration of the pause times is variable. 5 shows a control frequency with long pause times on the left,

730 on the right a control frequency with short pause times. The variant shown on the right therefore has significantly more control pulses per unit time of the valve. The reaction gas volume flow flowing through the reaction gas inlet valve into the low pressure region of the reaction gas supply is therefore significantly higher in the case of frequency-modulated control according to the variant shown on the right than in the case of

735 a control according to the variant shown on the left.

FIG. 6 shows a partial area of a fuel cell system 1 with water according to the invention being dispersed in a reaction gas. The partial area shown shows the path of a reaction gas up to the entry into the low-pressure area

740 reaction gas supply. The reaction gas flows from the high pressure region 5 of the reaction gas supply through the reaction gas inlet valve 8 with the drive unit 16 into the region 5 ′ of the reaction gas supply and from there through a throttle device 20 into the low pressure region 6 of the reaction gas supply. In the case of a continuously regulating reaction gas inlet valve, the area 5 'is a loading

745 richly increased pressure, in the case of a clocked reaction gas inlet valve, a region of variable pressure, in which the same pressure as in region 5 of the reaction gas supply line prevails when the reaction gas inlet valve is open. When the reaction gas inlet valve is closed, the pressure drops somewhat due to the reaction gas flowing out into the low-pressure region until the reaction gas inlet valve is opened again.

750 valves. A water supply 21 opens into the reaction gas supply between the reaction gas inlet valve 8 and the throttle device 20. The water supply 21 feeds water from a water reservoir 27 into the reaction gas supply by means of a pump 28. The water fed in is shown schematically in FIG. 6 by drops. The water feed can also be

755 le between the reaction gas inlet valve and the throttle device, even in the throttle device itself, but upstream from the narrowest cross section of the throttle device. Before passing through the throttling device 20, the reaction gas is at a pressure pi and after passing through the throttling device at a pressure p ₂ that is less than pi. The reaction gas is thus released, a supercritical expansion being preferred, since it ensures a thorough distribution of the water carried by the reaction gas volume flow in the reaction gas volume flow in the form of very fine droplets (mist, aerosol). In order to achieve supercritical relaxation, the throttle device 20 is preferably designed in the form of a convergent nozzle such that the pressure of the reaction gas flowing through the throttle device is equal to the critical pressure at its narrowest cross section. In Fig. 6, the reaction gas inlet valve is shown as a clocked valve. A continuously regulating inlet valve can also be used, but the clocked valve has the advantage that, when open, the pressure pi in the region 5 'of the reaction gas supply is equal to the pressure in the high pressure region 5 of the reaction gas supply. The reaction gas jet impinging on the throttle device 20 therefore has a very high pressure energy, which ensures very fine atomization and distribution of the water fed in after passing through the throttle device 20.

7 shows a partial area of a fuel cell system 1 with an arrangement for expelling water, and the partial area shown shows the section of the reaction gas supply from the reaction gas inlet valve to the beginning of the low-pressure area of the reaction gas supply. The reaction gas (represented by arrows) flows from the high pressure region 5 through the reaction gas inlet valve 8 with the drive unit 16 into the region 5 'of the reaction gas supply. A gas jet 22 is provided between the area 5 'of the reaction gas supply and its low pressure area 6. The gas jet is of conventional construction per se and has a driving nozzle 23, a catching nozzle 25, a gas outlet 29 and an inlet for gas suction 24. The gas jet 22 is arranged in the reaction gas supply in such a way that its area 5 ′ into the driving nozzle 23 of the gas jet opens and the gas outlet 29 opens into the low-pressure area 6 of the reaction gas supply. The reaction gas flowing through the gas jet 22 causes suction at the inlet to the gas intake 24, which is used to draw in excess gas. shot water from the fuel cells 3 can be used. For this purpose, 790 the fuel cells 3 or fuel cell stack 2 must be equipped with a reaction gas return 26, which opens into the inlet for the gas intake 24 of the gas emitter 22.

Such a reaction gas recirculation 26 is shown in FIG. 8. FIG. 8 shows a 795 fuel cell system 1, as shown in FIG. 1, but with gas jet 22 and reaction gas recirculation 26. Before entering the gas jet, the returned reaction gas preferably passes through a water separator (not shown).

The process of expelling water from the fuel cell system does not require the use of a special reaction gas inlet valve. However, the use of a clocked valve 8, as shown in FIG. 7, is preferred, since in this case the reaction gas enters the gas jet with high pressure energy when the valve is open, which ensures excellent suction power and thus efficient water intake from the fuel cells ,

805

FIG. 9 shows the same arrangement as FIG. 7, but with a water supply 21 as shown in FIG. 6. In the embodiment shown in FIG. 9, the driving nozzle 23 of the gas jet 22 takes over the function of the throttle device 20 in FIG. 6. The water supplied, shown in droplet form, which is mixed with the reaction gas

810 volume flow, shown as arrows, increases the motive mass flow through the gas jet 22 and thus its suction effect. After passing through the gas jet in the form of very fine droplets, the water is evenly distributed in the reaction gas. Overdosing of the water is relatively uncritical in large areas, since excess water in the gas channels of the combustion

815 material cell is continuously expelled through the cells by the flushing gas flow generated by the gas jet and separated from the gas flow at the cell outlet by means of a water separator. 9 also shows a valve with two switching positions as the reaction gas inlet valve, which has the advantages already mentioned in the other figures. However, a continuously controlled reaction

820 onsgas inlet valve can be used. 10 shows a fuel cell power system according to the invention, which is designed for variable power requirements of an electrical consumer. The arrangement is identical to the fuel cell system shown in FIG. 1 with regard to the reaction gas supply with reaction gas inlet valve 8, high pressure region 5 and low pressure region 6, as well as with regard to measuring point 9 and fuel cell stack 2, 2 '. A reaction gas outlet valve 11 as a safety valve is not shown in FIG. 10. A setpoint value for a desired reaction gas volume flow or a setpoint value for the power to be supplied or another electrical variable, for example voltage or current, is specified by means of a device 31. When the reaction gas volume flow is specified, the setpoint value is recorded by a control unit 32 which controls the reaction gas inlet valve 8 in such a way that the specified reaction gas volume flow from the high pressure area 5 of the reaction gas supply into the low pressure area 6 of the reaction gas supply is fed. At a measuring point 9, the reaction gas pressure (or a pressure-correlated measured variable) is measured and recorded by a power controller 33, which compares the measured value with the predetermined target value of the system. With an increasing inflow of reaction gas into the low pressure area 6, the reaction gas pressure increases in this area. As a result, the power controller 33 transmits a signal to the power electronics 34 connected to the electrical consumer 30 that fuel cell power can increasingly be drawn. The power electronics 34 then adjust the power of the electrical consumer 30 so that enough electrical power is drawn from the fuel cells that the pressure in the low-pressure region 6 is kept constant.

If the device 31 specifies an electrical variable, this predetermined setpoint value is determined in the control unit 32 using the actual value of the electrical variable determined by the power electronics 34 or another suitable measuring device, e.g. by means of a standard controller. The result of the comparison is used to actuate the reaction gas inlet valve 8, which is actuated whenever the desired value is not reached.

It is pointed out that the pressure control described above, the dispersion of dampening water in the reaction gas volume flow and the removal 855 far from excess water from the fuel cells each represent independent inventions and can advantageously be used in any fuel cell systems, regardless of their other construction.

Preferably, however, the device and the method for dispersing water 860 in the reaction gas volume flow as well as the device and the method for expelling excess water each additionally have one or more of the features described for the pressure control, any combination of features being possible.

865 A method and a system with pressure control according to the invention in combination with the dispersion of water according to the invention and the removal of excess water are particularly preferred. Also a combination of dispersing water according to the invention in the reaction gas volume flow for moistening the fuel cells and expelling excess water

870 the fuel cells for regulating the water balance in conventional pressure control is advantageous.

875

Claims

K 52 198/8880 PATENT REQUIREMENTS 1. Fuel cell system (1) comprising: 885 - at least one fuel cell stack (2), a reaction gas supply with a high pressure area (5, 5 ') and a low pressure area (6) to the fuel cell stack (2), a device for regulating the pressure in the low pressure area (6) the reaction gas supply with 890 - a reaction gas inlet valve (8) of the type with only two switch positions, a measuring point (9) for measuring the pressure or a pressure-correlated measurement variable in the low pressure area (6) of the reaction gas supply, a control and Control unit (10) for recording and evaluating the 895 pressure or the pressure-correlated measured variable and for controlling the Reaction gas inlet valve (8) depending on the pressure or the pressure-correlated measured variable. 2. Fuel cell system (1) according to claim 1, 900 characterized in that the device for regulating the pressure in the low-pressure region (6) of the reaction gas supply has a reaction gas outlet valve (1 1) which can be controlled by the control and regulating unit (10) depending on the pressure or the pressure-correlated measured variable. 905 3. Fuel cell system (1) according to claim 1 or 2, characterized in that the pressure-correlated measurement variable is the reaction gas volume flow or the partial pressure of the reaction gas. 4. Fuel cell system (1) according to one of claims 1 to 3, 910 characterized in that the control and regulating unit (10) a two Point controller or a continuous controller. 5. Fuel cell system (1) according to one of claims 1 to 4, characterized in that the reaction gas inlet valve (8) and / or the 915 reaction gas outlet valve (11) is a solenoid valve or a piezo valve. 6. Fuel cell system (1) according to one of claims 1 to 5, characterized in that the reaction gas inlet valve (8) separates the high-pressure region (5) and the low-pressure region (6) of the reaction gas supply 920. 7. Fuel cell system (1) according to one of claims 1 to 6, characterized in that the reaction gas inlet valve (8) with its drive (16) in the high pressure region (5, 5 ') or the low pressure region (6) of 925 Reaction gas supply is integrated. 8. Fuel cell system (1) according to one of claims 1 to 7, characterized in that the low-pressure region (6) of the reaction gas supply is a distributor line for reaction gas to the individual fuel cells (3) 930 of the fuel cell stack (2). 9. Fuel cell system (1) according to one of claims 1 to 7, characterized in that the low-pressure region (6) of the reaction gas supply is a low-pressure space from which the reaction gas into the reaction gas flow fields (14) of the individual fuel cells (3 ) of the fuel cell stack (2) flows. 10. Fuel cell system (1) according to one of claims 1 to 5, characterized in that there is a throttle device (20) in the reaction gas supply downstream of 940 the reaction gas inlet valve (8), which during operation of the fuel cell system ( 1) separates the high pressure area (5 ') and the low pressure area (6) of the reaction gas supply, and one between the Reaction gas inlet valve (8) and the throttle device (20) or in the throttle device in the reaction gas supply water supply (21) 945. 11. Fuel cell system (1) according to one of claims 1 to 5, characterized in that there is a gas jet (22) with a driving nozzle (23) in the reaction gas supply downstream of the reaction gas inlet valve (8), 950 inlet for gas suction (24) and trap nozzle (25), and one in the gas jet (22) opening reaction gas return (26) from the fuel cell stack (2), the mouth of the reaction gas return (26) forming the inlet for gas suction (24) of the gas jet, and wherein the gas jet (22) during operation the high pressure area (5 ^! ) and the low pressure area 955 rich (6) separates the reaction gas feed. 12. Fuel cell system (1) according to one of claims 1 to 5, characterized in that there is a throttle device in the reaction gas supply downstream of the reaction gas inlet valve (8), which during operation 960 high-pressure region (5 ') and the low-pressure region (6) of the reaction gas supply separates, a water supply (21) opening between the reaction gas inlet valve (8) and the throttle device or in the throttle device, a gas jet (22) with propellant nozzle (23), inlet for gas suction (24) and catch nozzle (25), and one can be 965 has the end of the reaction gas recirculation (26) from the fuel cell stack (2), the driving nozzle (23) of the gas jet forming the throttle device and the mouth of the reaction gas recirculation (26) the inlet for gas suction (24) of the gas jet (22 ) forms. 970 13. Method for regulating the pressure or volume flow of a reaction gas in a fuel cell system (1) with at least one fuel cell stack (2) and a reaction gas supply, which has a high pressure area (5, 5 ') and a low pressure area (6) comprises the following steps for the fuel cell stack: 975 - Providing a reaction gas inlet valve (8) of the type with only two Switching positions, continuous or regular measurement of the pressure or a pressure-correlated measured variable in the low pressure area (6) of the reaction gas supply, 980 - continuous or regular recording and evaluation of the pressure or the pressure-correlated measurement variable by comparing the actual value of the pressure or the pressure-correlated measurement variable with a predetermined setpoint value of the pressure or the pressure-correlated measurement variable, - actuation of the reaction gas inlet valve (8) as a function of the 985 pressure or the pressure-correlated measured variable such that the by the Reaction gas inlet valve (8) in the low pressure region (6) flowing reaction gas volume flow is increased if the actual value of the pressure or the pressure-correlated measured variable is below the predetermined target value, and is reduced if the actual value of the pressure or the pressure-correlated 990 measured variable lies above the predetermined target value, and Feeding the regulated reaction gas volume flow to the fuel cell stack. 14. The method according to claim 13, 995 characterized in that a reaction gas outlet valve (11) is provided in the low-pressure region (6) of the reaction gas supply, which is actuated when the actual value of the pressure or the pressure-correlated measured variable exceeds a predetermined limit value in order to allow reaction gas to fall below the limit value dismiss. 1000 15. The method according to claim 13 or 14, characterized in that the reaction gas volume flow is regulated by pulse modulation or frequency modulation. 1005 16. The method according to any one of claims 13 to 15, in which water is also dispersed in the reaction gas volume flow, characterized in that downstream of the reaction gas inlet valve (8) with only two switch positions 1010 a throttle device (20) is provided in the reaction gas supply, which separates the high pressure region (5 ') and the low pressure region (6) of the reaction gas supply, the pressure in the high pressure region being pi and in the low pressure region p ₂ , which is Reaction gas through the throttle device (20) from the high pressure 1015 rich (5 ') is _flowed into the low pressure region (6), the pressure at the narrowest cross section of the throttle _{device being} at least P _kπ t and

Water is introduced into the high-pressure region (5 ') of the reaction gas supply or into the throttle device (20), the water from the 1020 reaction gas volume flow is entrained, the reaction gas with entrained water as it emerges from the throttle device (20) and enters the low-pressure region (6) of the reaction gas supply is relaxed supercritically, the water being broken down into droplets, and 1025 - the regulated reaction gas volume flow with water dispersed therein is fed to the fuel cell stack (2). 17. The method according to any one of claims 13 to 15, wherein water is also expelled 1030 from the fuel cell system (1), characterized in that a gas jet (22) in with only two switching positions downstream of the reaction gas inlet valve (8) the reaction gas supply is provided, which separates the high pressure region (5 ') and the low pressure region (6) of the reaction gas supply, the reaction gas through the gas striler (22) from the high pressure region (5') into the low pressure region (6 ) the reaction gas supply is flowed into the fuel cell stack (2) and through the fuel cell stack, 1040 - unused reaction gas from the fuel cell stack is fed into a reaction gas return (26) in the reaction gas return (26) by sucking in gas and water from the fuel cell stack (2) of the reaction gas return by means of the gas emitter ( 22) a lower pressure than in the low pressure range 1045 (6) of the reaction gas supply is generated, and the gas sucked in by means of the gas emitter (22) is fed into the reaction gas supply. 18. The method according to any one of claims 13 to 15, 1050 characterized in that downstream of the reaction gas inlet valve (8) with only two switch positions, a throttle device is provided in the reaction gas supply, which separates the high pressure region (5 ') and the low pressure region (6) of the reaction gas supply, the pressure in the high pressure area pi 1055 and in the low pressure range p ₂ , a gas jet (22) with a driving nozzle (23), an inlet for gas suction (24) and a trap nozzle (25) is provided in the reaction gas supply, the driving nozzle (23) being the throttle device forms, the reaction gas through the throttle device (23) from the high pressure 1060 rich (5 ') is flowed into the low-pressure region (6) of the reaction gas supply, the pressure at the narrowest cross section of the throttle device being at least p _k rit and p ₂ <Pknt <Pi, Water is introduced into the high-pressure area (5 ¹ ) of the reaction gas supply or into the throttle device (23), the water being removed from the 1065 onsgas volume flow is entrained, the reaction gas with entrained water as it emerges from the throttle device (23) and enters the low-pressure region (6) of the reaction gas supply is relaxed in a supercritical manner, the water being broken down into droplets, 1070 - the regulated reaction gas volume flow with water dispersed therein is fed to the fuel cell stack (2), unused reaction gas from the fuel cell stack is fed into a reaction gas return (26) in the reaction gas return (26) by sucking in gas and water from the fuel cell stack (2) and the reaction gas return (26) by means of the gas jet (22) a lower pressure is generated than in the low pressure region (6) of the reaction gas supply, and the gas sucked in by means of gas jet (22) is fed into the reaction gas supply. 1080 19. A fuel cell system (1) comprising: at least one fuel cell stack (2), a reaction gas supply to the fuel cell stack, a throttle device (20) arranged in the reaction gas supply, 1085 which when the fuel cell system is in operation ( 1) separates a high-pressure (5 ¹ ) and a low-pressure region (6) of the reaction gas supply, and a water supply (21) opening upstream of the throttle device (20) or in the throttle device (20) into the reaction gas supply. 1090 20. Fuel cell system (1) according to claim 19, characterized in that the throttle device is a convergent nozzle or orifice. 21. Fuel cell system (1) according to claim 19 or 20, 1095 characterized in that it has a gas jet (22) with a driving nozzle (23), inlet for gas suction (24) and capture nozzle (25) and a reaction gas return (26) opening into the gas jet from the fuel cell stack (2), wherein the driving nozzle (23) of the gas jet (22) forms the throttle device and the mouth of the reaction gas recirculation (26) the inlet to 1100 gas intake (24) of the gas jet forms. 1105 22. A method for dispersing water in a reaction gas of a fuel cell system (1) with at least one fuel cell stack (2), a reaction gas supply to the fuel cell stack and a throttle device (20) in the reaction gas supply, the one High pressure area (5 ^! ) 1110 and a low-pressure area (6) of the reaction gas supply, the following Showing steps: Introducing a reaction gas with a pressure pi into the high pressure region (5 ') of the reaction gas feed, allowing the reaction gas to flow through the throttle device (20) into the 1115 low-pressure region (6) of the reaction gas supply with a pressure p ₂ , the pressure at the narrowest cross section of the throttle device (20) being at least pkπt and p ₂ <Pkm <pi, Introducing water into the high-pressure area (5 ') of the reaction gas feed or into the throttle device (20), the water being discharged from the 1120 menden reaction gas is entrained, supercritical expansion of the reaction gas with entrained water as it emerges from the throttle device (20) and entry into the low-pressure region (6) of the reaction gas supply, the water being broken down into droplets. 1125 23. The method according to claim 22, in which water is also expelled from the fuel cell system (1), characterized in that in the reaction gas supply a gas jet (22) with a propelling nozzle (23), 1130 an inlet for gas suction (24) and a trap nozzle (25) is provided, the driving nozzle (23) forming the throttle device, the reaction gas through the driving nozzle (23) of the gas jet (22) from the high pressure area (5 ') to the low pressure area (6) the reaction gas supply, in the fuel cell stack (2) and through the fuel cell 1135 stack is flowed through, unused reaction gas from the fuel cell stack is fed into a reaction gas supply (26), in the reaction gas supply (26) by suction of gas and water from the fuel cell stack (2) and the reaction gas supply (26) 1140 by means of the gas jet (22) a lower pressure than in the low pressure range (6) of the reaction gas supply is generated, and the gas sucked in by means of gas emitter (22) is fed into the reaction gas supply. 24. The fuel cell power system, which is designed for changing electrical requirements of an electrical consumer (30), comprising: at least one fuel cell stack (2), one consumer (30) electrically connected to the fuel cell stack, 1150 - a reaction gas supply to the fuel cell stack with a reaction gas inlet valve (8), a high pressure area (5, 5 ') and a low pressure area (6), a device (31) for specifying a target value of a reaction gas volume flow or a desired target value of an electrical quantity, 1155 - a device (32) for detecting the target value of the reaction gas volume flow and for controlling the reaction gas inlet valve (8) in accordance with the target value specification, or a device for determining the actual value of the electrical variable and a device for comparison the determined actual value with the specified 1160 nominal value and for controlling the reaction gas inlet valve (8) in accordance with the nominal value specification, a measuring point (9) for continuous or regular measurement of the pressure or a pressure-correlated measurement variable in the low pressure area (6) of the reaction gas supply, 1165 - a device (33) for detecting and evaluating the pressure or the pressure-correlated measured variable and for releasing the amount of the electrical variable corresponding to the pressure or the pressure-correlated measured variable to the electrical consumer (30), and a device (34) for setting the desired one Target value of the electrical 1170 size in the electrical consumer. 25. The fuel cell power system according to claim 24, characterized in that the electrical variable is a power or a voltage or a current. 1175 26. Method for adapting a fuel cell power system with at least one fuel cell stack (2), at least one reaction gas supply with a high pressure area (5, 5 ') and a low pressure area (6) and a reaction gas inlet valve (8) to variable electrical requirements 1180 gene of an electrical consumer (30), comprising the following steps: Specification of a target value for a reaction gas volume flow or for an electrical quantity, Detecting the target value of the reaction gas volume flow and actuating the reaction gas inlet valve (8) in such a way that the specified 1185 target value corresponding reaction gas volume flow is fed into the low pressure area (6) of the reaction gas supply, or determining the actual value of the electrical quantity and comparing the determined actual value with the predetermined target value and controlling the reaction gas inlet valve ( 8) according to the target value specification, 1190 - continuous or regular measurement of the pressure or a pressure-correlated measurement variable in the low pressure area (6) of the reaction gas supply, Detecting and evaluating the pressure or the pressure-correlated measured variable by comparing the actual value with a predetermined target value of the 1195 pressure or the pressure-correlated measured variable, Releasing an amount of the electrical variable to the electrical consumer when the actual value exceeds the predetermined target value of the pressure or the pressure-correlated measured variable in the low-pressure region (6) of the reaction gas supply, and 1200 - Extract an amount of the electrical quantity by the electrical Consumer (30) up to the setting of the desired target value of the electrical quantity at the electrical consumer.