Method for starting a fuel cell system and a fuel cell system

Patent metadata

Field	Value
Publication number	US-2017352901-A1
Application number	US-201715615689-A
Country	US
Kind code	A1
Filing date	Jun 6, 2017
Priority date	Jun 7, 2016
Publication date	Dec 7, 2017
Grant date	—

Abstract

The invention relates to a starting method for a fuel cell system ( 100 ), particularly for an air/air start of the fuel cell system ( 100 ). The method enables the reduction of damaging half-cell voltages in the fuel cell stack ( 10 ) through voltage limitation by means of a DC voltage converter. The homogeneous flushing of the fuel cell stack ( 10 ) required for this takes place by means of introduction of an anode operating medium into an anode inlet channel ( 17 ) of the otherwise sealed fuel cell stack ( 10 ) until a predetermined pressure is reached and flushing of the active areas of the fuel cells ( 11 ) of the stack ( 10 ) after said pressure is reached through opening of an anode discharge adjusting aid ( 26 ), preferably arranged in an exhaust coupling ( 29 ) connecting the anode exhaust line ( 22 ) and the cathode exhaust line ( 31 ). In preferred embodiments of the method according to the invention, a provision is to improve the mass flow of the anode operating medium in an anode supply ( 20 ) of the fuel cell stack ( 10 ) through suitable operation of a recirculation conveying mechanism ( 27 ). Another subject matter of the invention is also a fuel cell system ( 100 ) with a control unit ( 70 ) for implementing the method according to the invention.

First claim

1 . A method comprising:
starting a fuel cell system, the fuel cell system including a plurality of fuel cells, the starting including:
blocking an anode discharge adjusting means in an anode exhaust line of an anode supply;
detecting a pressure in an anode inlet channel of the fuel cell stack of the fuel cell system;
introducing an anode operating medium into an anode supply line until reaching a threshold pressure in the anode inlet channel;
evenly distributing the anode operating medium in the anode inlet channel;
preventing the anode operating medium from entering the plurality of fuel cells;
opening of the anode discharge adjusting means after reaching the threshold pressure in the anode inlet channel
introducing of the anode operating medium by means of subcritical operation of an operating medium conveying mechanism; and
converting to a supercritical operation of the operating medium conveying mechanism before or at the same time as the opening of the anode discharge adjusting means.

2 . The method according to claim 1 further comprising:
setting a voltage limit of a DC voltage converter and establishing an electrical connection between the DC voltage converter and at least one fuel cell of the plurality of fuel cells before the introducing of the anode operating medium into the anode supply line.

3 . The method according to claim 1 , further comprising creating an electrical current with depletion of oxygen by evenly flowing the anode operating medium into an active area of the plurality of fuel cells after the opening of the anode discharge adjusting means.

4 . The method according to of claim 1 , further comprising:
activating of a recirculation conveying mechanism arranged in a recirculation line connecting the anode supply line and the anode exhaust line before or at the same time as the opening of the anode discharge adjusting means.

5 . (canceled)

6 . The method according to claim 4 , further comprising:
blocking the recirculation line or operating the recirculation conveying mechanism in reverse mode during the introducing of the anode operating medium; and unblocking the recirculation line or converting the recirculation conveying mechanism to normal mode before or at the same time as the opening of the anode discharge adjusting means.

7 . The method according to claim 1 , further comprising:
recording a stack voltage according to a predetermined first time frame; determining a second time frame by means of the recorded stack voltage; and closing the anode discharge adjusting means after the first time frame and the second time frame.

8 . The method according to claim 1 , further comprising:
blocking a first cathode separator, a second cathode separator, the first cathode separator in a cathode supply line and the second cathode separator in a cathode exhaust line; and activating of a compressor in the cathode supply line in response to a wastegate adjusting means opening before opening of the anode discharging adjusting means.

9 . The method according to claim 8 , further comprising:
closing of the wastegate adjusting means by means of a control process; opening of the first cathode separator and of the second cathode separator; and converting to a controlled operation of the wastegate adjusting means.

10 . A fuel cell system comprising:
a fuel cell stack with an anode inlet channel for supplying an anode operating medium to a plurality of fuel cells; an anode supply with an anode supply line for supplying the anode operating medium to the anode inlet channel and with an anode exhaust line; a cathode supply with a first cathode separating means arranged in a cathode supply line and with a second cathode separating means arranged in a cathode exhaust line; an exhaust coupling connecting the anode exhaust line and the cathode exhaust line, the exhaust coupling comprising an anode discharge adjusting means; a recirculation line connecting the anode supply line and the anode exhaust line, the recirculation line comprising a recirculation conveying mechanism; a compressor arranged in the cathode supply line; a wastegate line connecting the cathode supply line and the cathode exhaust line, the wastegate line comprising a wastegate adjusting means; a conveying mechanism arranged in the anode supply line; a sensor for detecting a pressure in the anode inlet channel; a voltage sensor for recording an electrical stack voltage; and a control unit that in operation:
blocks the anode discharge adjusting means;
detects a pressure in the anode inlet channel;
introduces the anode operating medium into the anode supply line until a threshold pressure in the anode inlet channel is reached, the anode operating medium being evenly distributed in the anode inlet channel and the plurality of fuel cells being remaining free of the anode operating medium; and
opens the anode discharge adjusting means after the threshold pressure in the anode inlet channel is reached.

11 . The fuel cell system of claim 10 wherein the control unit in operation sets a voltage limit of a DC voltage converter that can be connected to the fuel cell stack and establishes an electrical connection between the DC voltage converter and at least one fuel cell of the plurality of fuel cells before the anode operating medium is introduced into the anode supply line.

12 . The fuel cell system of claim 10 wherein the control unit activates the conveying mechanism before or at the same time as the anode discharge adjusting means is opened.

13 . The method according to claim 1 , further comprising:
recording a stack voltage according to a predetermined first time frame; determining a second time frame by means of the recorded stack voltage; and closing the anode discharge adjusting means in response to exceeding a threshold concentration of the anode operating medium in the fuel cell stack, the anode exhaust line, or a cathode exhaust line.

14 . The method according to claim 1 , further comprising:
recording a stack voltage according to a predetermined first time frame; determining a second time frame by means of the recorded stack voltage; and closing the anode discharge adjusting means in response to a voltage or current plateau.

Assignees

• Volkswagen Ag

Inventors

• Hartung Ingmar
• Kirchhoff Maren Ramona
• Arendt Martin
• Turner Heiko

Classifications

• H01M8/04559

  of fuel cell stacks · CPC title

• H01M8/04302 Primary

  applied during start-up · CPC title

• H01M8/04097

  with recycling of the reactants (H01M8/04119, H01M8/04104 take precedence) · CPC title

• H01M2008/1095

  Fuel cells with polymeric electrolytes · CPC title

• H01M8/04388

  of anode reactants at the inlet or inside the fuel cell · CPC title