CN-115769404-B - Method for frost starting a fuel cell device, fuel cell device and motor vehicle having a fuel cell device

Abstract

The invention relates to a method for frost starting a fuel cell device (1) having a fuel cell stack (3), wherein a plurality of fuel cells (2) connected electrically in series are compressed between two end plates (22) with a compression force of a tensioning device (23), comprising the steps of determining the presence of a frost starting condition, reducing the compression force by means of the tensioning device (23), and operating the fuel cells (2) in a frost starting operation, in which the compression force acting on the fuel cells (2) of the fuel cell stack (3) and reduced relative to the compression force of normal operation is maintained. The invention further relates to a fuel cell device (1) and a motor vehicle having a fuel cell device (1).

Inventors

• O. Cage
• A. Siebel
• S. Woyt

Assignees

• 奥迪股份公司

Dates

Publication Date

20260508

Application Date

20211025

Priority Date

20201028

Claims (9)

1. 1. A method for a frost start fuel cell arrangement (1) having a fuel cell stack (3) in which a plurality of fuel cells (2) electrically connected in series are compressed between two end plates (22) with a compression force of a tensioning device (23), the method comprising the steps of determining the presence of a frost start condition, reducing the compression force by means of the tensioning device (23) such that each individual contact resistance between the fuel cells (2) of the fuel cell stack (3) increases, operating the fuel cells (2) in a frost start operation in which a compression force acting on the fuel cells (2) of the fuel cell stack (3) and reduced relative to a normal operation is maintained, detecting the temperature of the fuel cell stack (3) continuously or in a clock pulse manner, and adjusting the compression force by means of the tensioning device (23) depending on the detected temperature.
2. 2. A method according to claim 1, characterized in that the compression force is increased continuously or in stages by the tensioning device (23) until a predetermined normal temperature of the fuel cell stack (3) is reached.
3. 3. Method according to claim 2, characterized in that upon reaching the normal temperature the fuel cell arrangement (1) is shifted into the normal operation, in which normal operation an increased compression force compared to the compression force of the frost start operation is applied to the fuel cell (2).
4. 4. A method according to any one of claims 1-3, characterized in that the fuel cell (2) is additionally operated in an oxygen-consuming manner under the frost start-up operation.
5. 5. A method according to any one of claims 1-3, characterized in that the fuel cell (2) is also operated at a reduced voltage relative to the normal operation voltage in the frost start operation.
6. 6. A method according to any one of claims 1-3, characterized in that the tensioning device (23) is formed with a tensioning belt, the tension of which is adjusted with an electric actuator.
7. 7. A method according to any one of claims 1-3, characterized in that the tensioning device (23) is formed with a tie rod, the tension of which is adjusted with an electric actuator.
8. 8. Fuel cell device (1) with adjustable tensioning means (23) for adjusting the compression force on a fuel cell (2) stacked between two end plates (22), and with control means arranged to perform the method according to any one of claims 1 to 7.
9. 9. A motor vehicle having a fuel cell device (1) according to claim 8.

Description

Method for frost starting a fuel cell device, fuel cell device and motor vehicle having a fuel cell device Technical Field The invention relates to a method for a frost start fuel cell arrangement having a fuel cell stack in which a plurality of fuel cells connected electrically in series are compressed between two end plates with a compression force of a tensioning device, comprising the steps of determining the presence of a frost start condition, reducing the compression force by means of the tensioning device, and operating the fuel cells in a frost start operation in which the compression force acting on the fuel cells of the fuel cell stack and reduced relative to the compression force of a normal operation is maintained. The invention further relates to a fuel cell device and a motor vehicle having a fuel cell device. Background Fuel cell devices are used to chemically convert fuel and oxygen into water to produce electrical energy. For this purpose, the fuel cell comprises as a core component a so-called membrane electrode unit, which is a composite of a proton-conducting membrane and electrodes (anode and cathode) arranged on both sides of the membrane, respectively. Furthermore, a Gas Diffusion Layer (GDL) may be arranged at the side of the electrode facing away from the membrane on both sides of the membrane electrode unit. In the operation of a fuel cell arrangement having a plurality of fuel cells combined to form a fuel cell stack, a fuel, in particular hydrogen (H 2) or a hydrogen-containing gas mixture, is supplied to the anode, where electrochemical oxidation of H 2 to H + takes place with the evolution of electrons. Proton H + is transported (with or without water) from the anode chamber to the cathode chamber through a membrane that separates the reaction chambers from each other in a gas-tight manner and electrically insulates them. Electrons provided at the anode are transported to the cathode through an electrically conductive line. Oxygen or an oxygen-containing mixed gas is supplied to the cathode so that the reduction of O 2 to O 2- is performed while receiving electrons. At the same time, these oxyanions react with the protons transported across the membrane in the cathode compartment, forming water. This water must be drawn out of the fuel cell and fuel cell stack until the desired humidity level for operation of the fuel cell system is reached. Thus, the fuel cell device requires careful water management, since on the one hand it is necessary to prevent the presence of excessive water in the fuel cell or fuel cell stack, which leads to blockage of the flow channels for supplying the reactants. On the other hand, if too little water is present in the fuel cell, the proton conductivity of the membrane is limited, so that attention must be paid to sufficient humidity and water supply of the membrane. In order to supply sufficient oxygen from the air to a large number of fuel cells combined in a fuel cell stack, the air in order to supply the cathode space of the fuel cell stack to have oxygen contained therein is compressed by means of a compressor, whereby there is relatively warm and dry compressed air whose humidity is insufficient for use in the fuel cell stack for the membrane electrode unit. Thus, humidifiers are used which facilitate the transfer of humidity to a drier medium in the case of two gaseous media having different water contents in such a way that the dry air supplied by the compressor is led through a humidifier membrane permeable to water vapor, the other side of which is swept with moist exhaust gases from the fuel cell stack. This is problematic if there are frost conditions, i.e. conditions in which water freezes, at the time of starting the fuel cell system. This can result in the necessary flow channels for the reactant gases and product water being blocked by ice, so it is known to perform a drying procedure when the fuel cell device is shut down. Problems can likewise occur when starting up the fuel cell system, since in the preheating operation of the fuel cell system up to its operating temperature, there is and may occur a temperature difference in the fuel cell stack, which is related to the supply of the medium, i.e. the gaseous reactants and the cooling medium for the temperature control of the fuel cell stack, which is usually composed of a cooling fluid with a higher heat capacity than the reactants. In mobile applications, it is of interest to pay attention in a targeted manner that the start-up of the fuel cell arrangement can be performed as quickly as possible, wherein however the start-up is limited or delayed by the thermal mass of the fuel cell stack and the coolant, by possible ice cubes in the flow channels and by the maximum power consumption of the vehicle. In US 2005/058 865a 1a fuel cell stack is described in which the fuel cells integrate an electrical heating element between the surrounding end plates, if frost conditions are present