Saturday, 9 June 2018

DAIMLER: The end of a long wait

Source: DAIMLER, 1st June 2018, Illustration: Pietari Posti, Text: Walther Wuttke

In 2018 Daimler will be launching the GLC F-CELL, the next generation of fuel cell vehicles by Mercedes-Benz. More about the potential of this technology.

For several decades, fuel cells have been the “green” beacon of hope among alternative power-train technologies. But it has taken a long time to develop the first fuel cell prototypes into series production vehicles.

Toward the end of the 1990s, there were optimistic announcements that this technology would be ready for series production in the near future. However, back then “no one had yet figured out how to give fuel cells a cold start capability,” explains Professor Christian Mohrdieck, Head of the Fuel Cell unit at Daimler AG. “After all, the fuel cell produces water, and the water can freeze, thus destroying the membrane structures of the fuel cell.” That’s why it took so long for this beacon of hope to actually reach market maturity. Besides, Mohrdieck adds in retrospect, “Back then the automotive engineers underestimated the chemistry that was involved. Conversely, the fuel cell experts, who came from the field of electrochemistry, had no idea how to develop a solution that was appropriate for automobiles.”

But now the waiting has come to an end after a long interval followed the unveiling of the B Class F-CELL in 2010. This year the next-generation fuel cell vehicle from Mercedes-Benz, the GLC F-CELL, will be delivered to selected customers. The developers have succeeded in fitting the fuel cell system into the engine compartment of a series-produced vehicle, just like a conventional combustion engine. “We have thus granted ourselves the option of freely deciding which models could follow the GLC F-CELL,” Mohrdieck says. “We will forge ahead with fuel cell development, because we are convinced that we need alternative power-train technologies in order to cover all possible solutions, from hybrids to fuel cell vehicles. That’s because our range of models is so broad, ranging from very small cars to 40-ton trucks. This is the only way we can further reduce fuel consumption and emissions.”

According to Mohrdieck, in order to be able to use fuel cells in other automobile segments in the future, the Daimler developers now have to “develop a basic model that can be used for as many application profiles as possible.” He develops his future vision as follows: “The vehicle architecture of the GLC F-CELL, for example, is ideally suited to house a fuel cell drive system. We can use the traditional engine tunnel, which we don’t need for the fuel cell drive system, for the hydrogen tanks. However, if we want to expand the range of fuel cell vehicles, we have to make greater changes in the vehicle architecture, especially in the underbody.”

In the GLC F-CELL Daimler is using a unique combination of a plug-in hybrid and a fuel cell because, as Mohrdieck puts it, “We don’t want to do without the advantages of hybridization. Moreover, the network of hydrogen filling stations has not yet been comprehensively expanded to the point where our customers can charge their GLC F-CELL vehicles overnight for a range of about 50 kilometers so that they can safely reach the next filling station.”

When he considers the possible future scenarios of alternative drive systems, Mohrdieck envisions a division of labor, with battery-electric vehicles primary used in local urban traffic and fuel cell models used for long-distance driving. “I envision the fuel cell being primarily used in large, heavy vehicles and in those that need to travel long distances every day,” he says. “For vehicles in urban environments that don’t require a long range, the battery is a very good solution.”

In addition to their use in vehicles, fuel cells also work well as stationary energy sources. The Hewlett-Packard computer company, for example, is using fuel cell technology for a data center in Colorado. The fuel cell produces energy for the computers, and in addition the cooling circuits of the computers and the fuel cell are connected. “The temperature of the cooling water emerging from the data center is exactly the right input temperature for cooling the fuel cell. That further improves the system’s efficiency,” Mohrdieck says. The cooling water emerging from the fuel cell “has a temperature between 60 and 70°C. It can be used to heat sidewalks in Colorado in the winter, for example,” he adds. Daimler, HPE, and Power Innovations are currently cooperating with the National Renewable Energy Lab on a pilot project in this area of technology. They are using the fuel cell systems from the GLC F-CELL — but instead of powering a vehicle, in the project the fuel cells are used in a stationary system that utilizes energy from renewable sources to provide data centers with electricity around the clock.

At the moment, the hydrogen for operating the fuel cells is still gained primarily from fossil energy sources such as natural gas. All the same, the system generates approximately 25 percent less CO2 than gasoline engines. “But this is only the first step,” Mohrdieck predicts. “In the medium term we want to produce hydrogen in renewable ways. Wind and solar energy offers many opportunities to use hydrogen as a storage medium.” Fuel cells are also environment-friendly in their production stage. The carbon footprint of fuel cell production is very good, because no valuable materials are required except for platinum. “In the future, the proportion of platinum used here will be about the same as the proportion in the catalytic converter of a combustion engine,” Mohrdieck explains. Moreover, just like the steel that is used, almost 100 percent of the platinum can be reused in new drive systems. As a result, a closed circuit is formed.

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