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The Fuel Cell Technology of the GLC F-CELL

This article was originally published in the Daimler blog.

„Ahmet, your car smokes like a shisha bar!” Right, but the GLC F-CELL (GLC F-CELL: Wasserstoffverbrauch kombiniert: 0,34 kg/100 km; CO2-Emissionen kombiniert: 0 g/km; Stromverbrauch kombiniert: 13,7 kWh/100 km.*) doesn’t “smoke”. The emissions are H2O: Water vapor.

For the GLC F-CELL a completely new fuel cell system was developed. What’s special about it?

The GLC F-CELL is the first vehicle worldwide that contains a plug-in hybrid battery. Thereby, two different energy sources are available to drive the electric engine. That’s why it’s not dependent on hydrogen filling stations, but rather can be refueled at any charging station or socket available.

How does the fuel cell system of the GLC F-CELL work?

Everybody knows the electrolysis from chemistry class: Water can be split into hydrogen and oxygen when interfered with electricity. These two gases are used to gain electricity in the reverse process. Thus the fuel cell does nothing else than conducting the reaction between hydrogen and oxygen.

The oxygen needed for the reaction is pulled in from the outside and is provided by an electric turbocharger. The hydrogen necessary for the fuel cell is provided by the hydrogen tanks.

The fuel cell is a PEM fuel cell with Proton Exchange Membrane, meaning that its membrane is only permeable for protons. The hydrogen is split into protons and electrons. Protons migrate from the anode side via the membrane to the cathode side in order to get to the oxygen. The electrons take their way around the membrane, resulting in an electricity flow. This electricity is either used for the electric drive or to charge the battery.

The essential components in the GLC F-CELL are the fuel cell, the hydrogen tanks and the battery. How do they interact in operation?

The Fuel Cell

The fuel cell system mentioned above refers to one PEM fuel cell. In order to maximize the electricity flow, there is a fuel cell stack in the vehicle. This stack contains many single fuel cells. The actual reaction between hydrogen and oxygen takes place in those fuel cell stacks, in which the chemical reaction energy is converted (also known as cold or catalytic combustion). Therefore, in contrast to the battery, the fuel cell is no energy storage but rather an energy converter.

The Hydrogen Tanks

The hydrogen is located in two tanks: one long container and one cross container. The cross container is installed under the rear seat bench, the long container underneath the center tunnel. Both tanks are able to absorb 4.4 kg hydrogen, which can be fully refueled within three minutes at 700 bar.

The Battery

The lithium-ion battery of the GLC F-CELL is located under the car’s trunk. It has a capacity of approximately 13.5 kWh and can be charged while operating: either through the fuel cell or the recuperation, namely the brake energy recovery. The major task of the battery is the buffering of the electric energy and the additional driving power.

The driver has the opportunity to choose between four different operating modes. What does each mode stand for?

In HYBRID operating mode, the power of the vehicle is provided by both energy sources, namely the fuel cell and the battery. BATTERY means that the vehicle is powered purely battery-electric while the fuel cell is switched off. In F- CELL mode, one drives almost exclusively with hydrogen, whereby the energy of the fuel cell holds the charge level of the battery constant. And in CHARGE mode, the battery is charged via the fuel cell. The recuperation should be mentioned as well. It’s available in every operating mode and makes it possible to regain the energy when braking or coasting, and storing it in the battery.

Which mode is used when – and who decides: the system or the driver?

Basically, the driver can decide at any time which operating mode he or she wants to use. But the vehicle is able to make this decision itself: Depending on the gas pedal requirement of the driver, the intelligent system of the GLC F-CELL is able to determine how much energy is currently needed. And from which source this energy has to be provided – without the driver’s notice.

The GLC F-CELL doesn’t know whether you’re driving on a motorway, highway or in a 30 km/h zone. Only the gas pedal requirement of the driver is significant for the vehicle: that’s how the required power is calculated. On this basis, the GLC F-CELL decides whether e.g. 70 percent of the power should be provided by the fuel cell and 30 percent by the battery. Or whether it’s driving exclusively battery-electric in BATTERY mode.

Electric Mobility: Battery vs. Fuel Cell?

Ahmet does not perceive the battery and the fuel cell as competitors. In his opinion, they complement each other perfectly. For short-distance drives, the battery is much more appropriate as the fuel cell. During long-distance drives, the fuel cell technology shows its strengths: a high range and a fast refueling time.

When Ahmet took the GLC F¬-CELL at home for the very first time in order to simulate customer road behavior over several weeks, he didn’t wanted to give it back. Commuting, shopping and travelling: not a problem!

Vivienne Brando

To Vivienne Brando the electrolysis in chemistry class is and always has been a mystery. To shed light in the dark, she met Ahmet at the Mercedes-Benz Fuel Cell GmbH in Nabern. She was fascinated of the fuel cell technology and the complex procedure, which is controlled by the vehicle in a very intelligent and efficient way. A real experience – even in the passenger seat!

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From Blog to Daimler Magazine

Sorry to take you by surprise, but the Daimler Blog has retired on Nov 7, 2019 - after twelve years. Say hello to its successor: the new Daimler Magazine – a magazine for mobility and society.
The original blog article is still available in the magazine. We have therefore forwarded you directly to it.
We hope you’ll enjoy a good read!