DE102013218092A1 - Method for heating a battery - Google Patents

Abstract

A method for heating a battery, in particular during a freeze start, wherein a first coolant flowing through a first coolant system, the battery tempered, and a second coolant flowing through a second coolant system, a fuel cell stack temperature. Object of the present invention is that the second coolant heats the first coolant in a heat exchanger, so that the first coolant heats the battery.

Description

The invention relates to a method for heating a battery, in particular during a freeze start, wherein a first coolant flowing through a first coolant system, the battery tempered, and a second coolant flowing through a second coolant system, a fuel cell stack tempered, according to the preamble The invention further relates to a power generation system for generating an electric current according to the preamble of independent patent claim 7.

STATE OF THE ART

The DE 11 2010 002 093 T5 discloses a fuel cell hybrid vehicle having a coolant system for a fuel cell. According to this document, a coolant flow of the coolant system of the fuel cell is controlled at low temperatures in order to avoid freezing of the water chemically generated in the fuel cell and damage to an electrolyte membrane.

However, temperatures around the freezing point and below the freezing point are also problematic for a battery of a fuel cell hybrid vehicle or a fuel cell range extender. Thus, the performance of a battery at temperatures around the freezing point and below the freezing point is very limited. Therefore, acceleration of the fuel cell range extender is reduced and brake energy recovery is limited. For the battery to be powerful again, the battery must be heated. For this purpose, electrical heaters can be used, which draw electricity from the battery. This reduces the state of charge of the battery and thus the range of the fuel cell range extender.

DISCLOSURE OF THE INVENTION

It is the object of the invention to provide a method for heating a battery and a power generation system for generating an electric current, in which at least one of the mentioned disadvantages is avoided. In particular, the battery should be able to be heated without reducing its state of charge.

To solve the problem, a method with all features of claim 1, in particular the characterizing part proposed. Advantageous developments of the method are specified in the dependent method claims. The object is further achieved by a power generation system having all the features of independent claim 7, in particular the characterizing part. Advantageous developments of the power generation system are given in the dependent device claims. Features and details described in connection with the method according to the invention also apply in connection with the power generation system according to the invention and vice versa. The features mentioned in the claims and in the description may each be essential to the invention individually or in combination.

According to the invention, it is provided that the second coolant heats the first coolant in a heat exchanger, so that the first coolant heats the battery.

The core of the invention is that the second coolant heats the first coolant. In this way, the first coolant in turn can heat the battery, so that the battery reaches full capacity even at temperatures around a freezing point or below the freezing point again. Further eliminates an electric heater for heating the first coolant. This avoids that the state of charge of the battery decreases. The method may, for. B. for heating a battery of a fuel cell range extender or fuel cell hybrid vehicle. A fuel cell range extender is a vehicle in which the charged battery provides electric power to an electric motor, and only in the event that the battery is discharged, provides the electric power to the fuel cell stack to the electric motor. Is sufficient the state of charge of the battery z. Example, not for a longer drive, the electric power is provided for operation of the electric motor of the fuel cell stack. A fuel cell hybrid vehicle is a vehicle in which the fuel cell stack provides the electrical power for the electric motor of the vehicle and the battery supports the fuel cell stack, for. B. to allow a dynamic driving style. In particular, the method is suitable for heating a battery during a freeze start, in particular during a freeze start of a fuel cell range extender or a fuel cell hybrid vehicle. During a freeze start, the battery has a temperature around the freezing point and / or below the freezing point. However, the method according to the invention is also suitable for other freeze starts, for example for a freeze start in a stationary application.

The first coolant system and the second coolant system are in particular independent of each other. That is, the first coolant and the second coolant are materially separated from each other. Thus, the first coolant flows through a separate from the second coolant line system. The first and second coolants are in thermal contact in the heat exchanger.

In particular, the second coolant is heated by the fuel cell stack so that the second coolant can heat the first coolant in the heat exchanger during the process according to the invention.

Advantageously, the fuel cell stack is short-circuited by closing a short-circuit switch and the electric short-circuit current thus generated heats the fuel cell stack. As a result, sufficient heat is generated to heat the second coolant, so that this in turn can heat the first coolant. By providing the heat to heat the battery, the fuel cell stack uses a fuel, particularly hydrogen, to heat the battery.

In order for an electrical short-circuit current to flow after the closing of the short circuit switch, the educts of the electrochemical reaction taking place in the fuel cell stack are advantageously fed to the fuel cell stack after the short circuit switch has been closed. In particular, a fuel, for. As hydrogen, anodes of the fuel cell stack and an oxidizing agent, in particular oxygen-containing air, cathodes supplied to the fuel cell stack. In particular, it can be provided that the educts of the electrochemical reaction of the fuel cell stack for generating the electrical short-circuit current are supplied such that in a normal operation of the fuel cell stack, the nominal electric power would be generated. The nominal electrical power is understood to be the maximum electrical power for which the fuel cell stack is designed. This produces a thermal power that is approximately twice the nominal power rating. For example, the nominal electrical power can be 30 kW, so that when the fuel cell stack is short-circuited, a thermal power of 60 kW is produced. The short-circuit switch can be designed for an electrical current of 200 A or 500 A in this case.

Before closing the short-circuit switch, in particular, it is checked whether an electrical voltage prevails, and the short-circuit switch is closed only in the absence of an electrical voltage. This can ensure that no arc arises. In particular, the educts of the electrochemical reaction are supplied to the fuel cell stack only after closing the short-circuit switch.

If the battery has reached the desired temperature, in particular the short-circuit switch is opened. Previously, the supply of at least one educt of the electrochemical reaction of the fuel cell stack is reduced and / or terminated. In particular, the air supply to the cathode of the fuel cell stack is reduced and / or terminated. In particular, the supply of the at least one educt, in particular the air supply, is initially reduced and then terminated. If the oxygen is almost consumed as a reactant at the cathodes, the electric current decreases so much that the electric current is almost 0 A. Only after the electric current is reduced, the short-circuit switch is opened.

In particular, it may be provided that the short-circuit switch is opened only when the electrical current is below a value of 10% of the electrical current for which the short-circuit switch is designed. In the case of the above examples, the short-circuit switch is opened below an electrical current of 20 A or 50 A.

It can be provided that the battery during the process provides electrical power for operating the first and / or the second coolant system. In the first coolant system, a first coolant pump for the first coolant system may be arranged. Be arranged in the second coolant pump for the second coolant system. In particular, the battery provides electrical power for operating the first and / or second coolant pump. Further, the battery may provide electrical power to other devices necessary for the operation of the fuel cell stack. This may be z. Example, to a recirculation fan, with which the fuel is supplied to the anodes of the fuel cell stack again, and / or an intake valve, the supply of the fuel from a fuel tank allows act. Also, a compressor for supplying air to the cathodes may draw electric power from the battery.

It may be that the first coolant in the first coolant system is circulated and / or the second coolant in the second coolant system is circulated. In each case different coolant paths may be present in the first and / or second coolant system, so that the first and / or the second coolant can pass through different cycles. It may be that in each case a first coolant path exists in the first and / or second coolant system, which is arranged fluidically parallel to a second coolant path, wherein in the second coolant path, a radiator is arranged. The first coolant path, however, does not contain a radiator. The radiator serves to deliver heat to a means outside the first and second coolant systems. That is, a first radiator of the first coolant system serves to dissipate heat without supplying heat to the second coolant system. Accordingly, a second radiator of the second coolant system serves to dissipate heat without supplying heat to the first coolant system. For example, the heat can be released to the ambient air. Alternatively, the heat z. B. are delivered to an air conditioner. By means of the first and second fluidically parallel coolant path can, for. Example, by a 3/2 way valve, are set, whether the first and / or second coolant is cooled when passing through the respective coolant system in the respective radiator or not.

It can be provided that, during the method, the first and / or the second coolant flows through the respectively first coolant path, which is fluidically parallel to the respective second coolant path that contains the radiator. This avoids that the first and / or second coolant loses heat during the flow through the respective radiator during the process. In the first coolant path, the heat exchanger can be arranged.

In one embodiment, the method according to the invention can proceed as follows: first, the battery is connected to an electrical network so that the battery can supply electrical power to the devices which are necessary for carrying out the method. In particular, during the process, the battery supplies the first and second coolant pumps, the recirculation fan, the intake valve, and the compressor. Second, the 3/2-way valves in the first and second coolant systems are set such that the respective first coolant path and not the respective second coolant path respectively flows through the first and the second coolant. Furthermore, it is checked whether the voltage of the fuel cell is 0 V. If this is the case, the short-circuit switch is closed. After that, the compressor is switched on and the cathodes are supplied with air. Furthermore, the inlet valve is opened to supply a hydrogen to the anodes and the recirculation fan is turned on. As much hydrogen and oxygen is supplied to the anodes and the cathodes as to produce a thermal power approximately twice the nominal electric power in a normal operation of the fuel cell. Thereafter, it is checked whether the battery has reached the desired temperature. If the battery reaches the desired temperature, the air supply is reduced, thus reducing the electric current of the fuel cell stack. Thereafter, the air supply is stopped by the compressor is turned off. Optionally, the recirculation fan is also switched off. If the electrical current is close to 0 A, the short-circuit switch is opened. Thereafter, the educts are again supplied to the fuel stack in order to discharge reaction water and / or to provide electrical power. If the method is used in a fuel cell range extender, then with a charged battery, the compressor is turned off. Thereafter, the process for heating the battery is completed. The process duration can only take a few seconds.

The object of the invention is also achieved by a power generation system for generating an electric current with a battery, with a fuel cell stack, with a first coolant system and a second coolant system. In this case, the battery is arranged in the first coolant system in order to be tempered. In the first coolant system, a first coolant can be arranged. The fuel cell stack is arranged in the second coolant system, in which a second coolant can be arranged to be tempered. It is provided that a heat exchanger is arranged in the first and the second coolant system, so that heat between the first and the second coolant is transferable.

The power generation system has an electrical network. It is conceivable that the fuel cell stack is arranged in the electrical network, and that the electrical network has a short-circuit switch for closing the fuel cell stack. In the electrical network of the power generation system may further be arranged a DC-DC converter, the electric motor, the battery and / or other electrical loads.

Furthermore, it may be provided that the heat exchanger in the first and / or in the second coolant system is arranged fluidically parallel to the radiator of the respective coolant system. In particular, the heat exchanger can be located in the first coolant path of the first and / or second coolant system.

Furthermore, the power generation system can have a control unit in which a method according to the invention is stored.

Further, measures improving the invention will become apparent from the following description of an embodiment of the invention, which is shown schematically in the figures. All from the claims of the description or drawing of the given features or advantages including constructive Details, spatial arrangement and method steps can be essential to the invention both for themselves and in the most diverse combinations.

Show it:

1 a first part of a power generation system according to the invention, wherein a first and a second coolant system are shown,

2 a second part of the power generation system according to the invention 1 , wherein in particular the supply of the starting materials to a fuel cell stack is shown,

3 a third part of the power generation system according to the invention, wherein an electrical network is shown and

4 a method according to the invention.

Identical elements are designated by the same reference numerals in the figures.

In the 1 to 3 is in each case a part of a single power generation system according to the invention 10 shown. Here are in 1 Coolant Systems 12 . 22 of the power generation system 10 , in 2 the supply of the educts to a fuel cell stack 21 of the power generation system 10 and in 3 an electrical network 41 (Label is not in 3 to find, please add) of the power generation system 10 shown.

In 1 is the cooling of the power generation system 10 with a first coolant system 12 for tempering a battery 11 and with a second coolant system 22 for tempering a fuel cell stack 21 shown. According to the invention, the first coolant system is used 12 in addition to cooling also for heating the battery 11 , In the first coolant system 12 is a first coolant can be arranged using a first coolant pump 17 the first coolant system 12 can flow through. In the second coolant system 22 a second coolant can be arranged by means of a second coolant pump 27 the second coolant system 22 can flow through.

In the first coolant system 12 are a first coolant path 14 of the first coolant system 12 and a second coolant path 15 of the first coolant system 12 fluidically arranged in parallel. This can, depending on the position of a first 3/2-way valve 16 in each case the first coolant path 14 or the second coolant path 15 flowed through by the first coolant.

In the second coolant system 22 is a second 3/2 way valve 26 arranged, through which in turn a first coolant path 24 of the second coolant system 22 and a fluidically parallel second coolant path 25 of the coolant system 22 are selectable.

In the second coolant path 15 of the first coolant system 12 is a first cooler 13 arranged for cooling the first coolant. In the second coolant path 25 of the second coolant system 22 is a second cooler 23 arranged for cooling the second coolant. In the first coolant path 14 of the first coolant system 12 and the first coolant path 24 of the second coolant system 22 is a heat exchanger 20 arranged, on the one hand by the first coolant and on the other by the second coolant can be flowed through. Here, the first coolant and the second coolant can exchange heat. The first and the second coolant are materially separated.

Through the heat exchanger 20 it is possible to heat the first coolant, for. B. by first by a short-circuit current of the fuel cell stack 21 is heated, which then heats the second coolant. In the heat exchanger 20 For example, the second coolant may transfer heat to the first coolant. The first coolant can turn the battery 11 heat. Thus, it is possible the battery 11 To heat and thus to make completely efficient, without using an electric heater or the state of charge of the battery 11 to reduce. By the fuel cell stack 21 generated short-circuit current, only hydrogen is consumed.

In the power generation system is a control unit 30 arranged, which is the first coolant pump 17 and the second coolant pump 27 controls and / or regulates. Further, by the control unit 30 the first and the second 3/2-way valve 16 . 26 controlled and / or regulated.

In 2 are an example of an anode 33 and a cathode 37 a fuel cell of the fuel cell stack 21 represented by a membrane 39 (Label is not in 2 to be found, please add) are separated from each other. Hydrogen from a hydrogen tank 31 is via an inlet valve 32 the anode 33 supplied as fuel. An exhaust valve 34 is designed as a 3/2-way valve so that unused hydrogen can be recirculated. This is done by a recirculation fan 35 , A compressor 36 carries oxygen-containing air from an environment 38 the cathode 37 to. The control unit 30 can determine the position of the intake and exhaust valves 32 . 34 control and / or regulate. The control unit 30 can also reduce the electrical power consumption of the compressor 36 and the recirculation fan 35 control and / or regulate.

In 3 is an electrical network 41 of the power generation system 10 shown. In the electrical network 41 is the fuel cell 21 via a DC-DC converter 29 with the battery 11 , the electric motor 28 and other consumers electrically connected. Other consumers include the first coolant pump 17 , the second coolant pump 27 , the recirculation fan 35 , the inlet valve 32 and the compressor 36 , The battery 11 , the electric motor 28 and the consumers are each electrically connected in parallel. At the fuel cell 21 there is a short-circuit switch 40 , The control unit 30 may cause the shorting switch 40 is closed.

The power generation system according to the invention 10 is part of a fuel cell range extender or a fuel cell hybrid vehicle.

The electric engine 28 serves as a drive motor for the fuel cell range extender or the fuel cell hybrid vehicle.

In 4 is an embodiment of a method according to the invention 50 shown. In a first process step 51 becomes the battery 11 with the electrical network 41 connected by a switch, not shown. This can cause the battery 11 the first coolant pump 17 , the second coolant pump 27 , the recirculation fan 35 , the inlet valve 32 and the compressor 36 supply with electrical power.

In a second process step 52 become the first and the second 3/2-way valve 16 . 26 adjusted, or their settings checked, so that the first and the second coolant respectively through the first Kühlmittelpad 14 . 24 flows. In a third process step 53 it is checked whether the voltage of the fuel cell 21 is 0 V, so that the short-circuit switch 40 can be closed. In a fourth process step 54 becomes the short-circuit switch 40 closed. In a fifth process step 55 becomes the fuel cell 21 Hydrogen and oxygen-containing air supplied as starting materials of the electrochemical reaction. It is supplied so much hydrogen and oxygen, so that in a normal operation of the fuel cell 21 the nominal electrical power is achievable. As a result, a thermal power that is about twice as high as nominal electric power is achieved.

In a sixth process step 56 It checks if a target temperature of the battery 11 has been achieved. If not, what is in 4 is marked with a "-", so will step 56 repeated. Is the target temperature of the battery 11 achieves what is in 4 represented by a "+", the air supply is in a seventh process step 57 so far reduced and finally that the electrical current is close to 0 A. In an eighth process step 58 now becomes the electrical shorting switch 40 opened and in a ninth procedural step 59 becomes the compressor 36 switched back on. This is the procedure 50 finished and the power generation system 10 is now ready. The procedure for heating the battery 11 can be completed within a few seconds.

The inventive method 50 is in the control unit 30 saved.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 112010002093 T5 [0002]

Claims (10)

Procedure ( 50 ) for heating a battery ( 11 ), in particular at a freeze start, wherein a first coolant, which through a first coolant system ( 12 ), the battery ( 11 ), and a second coolant, which is cooled by a second coolant system ( 22 ), a fuel cell stack ( 21 ), characterized in that the second coolant, the first coolant in a heat exchanger ( 20 ), so that the first coolant is the battery ( 11 ) is heated. Procedure ( 50 ) according to claim 1, characterized in that the fuel cell stack ( 21 ) by closing a short-circuit switch ( 40 ) and the electrical short-circuit current generated in this way causes the fuel cell stack ( 21 ) is heated. Procedure ( 50 ) according to claim 1 or 2, characterized in that the educts of an electrochemical reaction of the fuel cell stack ( 21 ) for generating the electrical short-circuit current to the fuel cell stack ( 21 ) are supplied in such a way that in a normal operation, the nominal electric power from the fuel cell stack ( 21 ) is producible. Procedure ( 50 ) according to one of claims 1 to 3, characterized in that before closing the short-circuit switch ( 40 ) is checked, whether an electrical voltage prevails, and the short circuit switch ( 40 ) is closed only in the absence of an electrical voltage and / or the supply of a reactant of the electrochemical reaction of the fuel cell stack ( 21 ) is reduced and / or terminated before the short-circuit switch ( 40 ) is opened. Procedure ( 50 ) according to one of the preceding claims, characterized in that the battery ( 11 ) during the process electrical power for operating the first and / or second coolant system ( 12 . 22 ). Procedure ( 50 ) according to one of the preceding claims, characterized in that the first and / or the second coolant in the respective coolant system ( 12 . 22 ) a first coolant path ( 14 . 24 ), which is fluidically parallel to a second coolant path ( 15 . 25 ), a cooler ( 13 . 23 ) is arranged, flows through. Power generation system ( 10 ) for generating an electric current with a battery ( 11 ), with a fuel cell stack ( 21 ), with a first coolant system ( 12 ) and with a second coolant system ( 22 ), whereby the battery ( 11 ) in the first coolant system ( 12 ), in which a first coolant can be arranged, is arranged to be tempered, and the fuel cell stack ( 21 ) in the second coolant system ( 22 ), in which a second coolant can be arranged, is arranged to be tempered, characterized in that a heat exchanger ( 20 ) in the first and second coolant systems ( 12 . 21 ) is arranged so that heat between the first and the second coolant is transferable. Power generation system ( 10 ) according to claim 7, characterized in that the fuel cell stack ( 21 ) in an electrical network ( 41 ) and the electrical network ( 41 ) a short-circuit switch ( 40 ) for shorting the fuel cell stack ( 21 ) having. Power generation system ( 10 ) according to claim 7 or 8, characterized in that the heat exchanger ( 20 ) in the first and / or second coolant system ( 12 . 22 ) fluidically parallel to a cooler ( 13 . 23 ) is arranged. Power generation system ( 10 ) according to one of claims 7 to 9, characterized in that the power generation system ( 10 ) is constructed so that a procedure ( 50 ) according to one of claims 1 to 6 in the power generation system ( 10 ) is feasible.

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