Easy Tech: Fuell Cell Technology


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.

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by Einfach Technik / Easy Tech, Editor
published on March 19, 2019

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 PEM fuel cell conducts the reaction between hydrogen and oxygen, resulting in an electricity flow.
The PEM fuel cell conducts the reaction between hydrogen and oxygen, resulting in an electricity flow.

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 GLC F-CELL drivetrain with fuel cell stack, hydrogen tanks and battery.
The GLC F-CELL drivetrain with fuel cell stack, hydrogen tanks and battery.

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.

The driver can choose four different operating modes.
The driver can choose four different operating modes.

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.

Based on the driver’s gas pedal requirement, the car automatically selects the ideal operating mode.
Based on the driver’s gas pedal requirement, the car automatically selects the ideal operating mode.

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!

Einfach Technik / Easy Tech

Many have us have become used to them in everyday traffic: cameras, sensors and other technical assistants recognize and evaluate situations, making our journey safer and more comfortable. But how do all these safety, assistance, and comfort systems interact? And how do they actually work? With Easy Tech, we provide the answers to these and similar questions. Our assitants: the company’s tech experts. Furthermore, we take a closer look at the technology of new drive systems.

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