Interview: "The battery and fuel cell form the perfect symbiosis"

Prof. Dr. Christian Mohrdieck (58) heads the Fuel Cell Drive Development department as part of the Group Research and Development Mercedes-Benz Cars unit at Daimler. He is also General Manager of NuCellSys GmbH, a wholly-owned subsidiary of Daimler AG. This company is regarded as the world leader in the development of fuel cell and tanking systems for vehicle applications. Mohrdieck is therefore responsible for the fuel cell drive activities of Daimler AG, including the cooperative ventures. We spoke to him about the pre-series model of the GLC F-CELL and the future of fuel cell technology.

Professor Mohrdieck, the time will come soon: the first GLC F-CELL cars will go to selected customers before the year is out. Unlike numerous competitors, Daimler has shown staying power and remained committed to this technology. Why?

Mohrdieck: Fuel cell technology is an integral part of our drive strategy. The advantages are very clear to us: zero emissions, long ranges and short tanking times, plus a wide range of applications from cars to buses, other large commercial vehicles and not least also for stationary applications.

What is still preventing the breakthrough?

Mohrdieck: The market maturity of automotive fuel cell systems is now undisputed with respect to performance. Undoubtedly the filling station infrastructure is still an uncertainty factor for customers. But the number of filling stations is growing, and not only in Germany. With our new vehicle generation based on the GLC and the integration of plug-in technology, we have achieved an additional increase in range and charging options. Of course, the manufacturing costs are another aspect – but here too, we have made further important progress and can clearly see the next improvement potentials.

For whom are fuel cell cars suitable, and what role do they play in the drive system portfolio of Mercedes-Benz?

Mohrdieck: Fuel cell drive is above all of interest to customers who require a high day-to-day range and have access to hydrogen filling stations. For vehicles in an urban environment, however, purely battery-electric drive is currently a very good solution. The GLC F-CELL is an important step for us, even if we do not account for large production volumes at present. We are greatly looking forward to the feedback from our customers.

The GLC F-CELL is unique worldwide as a plug-in hybrid. Why have you combined fuel cell and battery technology in this way?

Mohrdieck: We wanted to use the advantages of hybridisation, and not have to decide between A or B. The battery has three advantages: we are able to recuperate kinetic energy, additional power is available during acceleration and there is the increased range already mentioned. The plug-in solution helps the customer in the initial phase of the infrastructure, when the filling station network is still "thin": charging for around 50 km can be done at home. In most cases this is enough to reach the next hydrogen filling station.

So is a plug-in fuel cell vehicle the answer for the future of mobility?

Mohrdieck: It could certainly be one of them. The battery and fuel cell form a symbiosis.The two technologies complement each other very well: The power and response of the battery support the long range capability of the quickly refuellable fuel cell, which has its ideal operating state in driving situations requiring constant power delivery. In the future, a combination of scaleable battery and fuel cell modules would be conceivable - depending on the mobility scenario and vehicle type.

At the Geneva Motor Show, Mercedes-Benz has just presented pre-series models of new plug-in diesel hybrids. There must be many areas of technical similarity, right?

Mohrdieck: With our plug-in fuel cell drive system we already benefit from our modular hybrid concept, and especially from the compact design of our fuel cell system. In principle the drive system could be transferred to numerous model series and body variants, as all the other components – the power electronics, electric motor etc. – are part of our modular system and can for the most part be flexibly combined.

The GLC F-CELL pre-series models are produced in Germany. What are the detailed arrangements?

Mohrdieck: For the GLC F-CELL too, we have recourse to our worldwide network of expertise. The vehicle itself is produced in Bremen, in cooperation with our partner EDAG. Assembly of the fuel cell system is carried out in the Kirchheim-Nabern location, an annex of the Mercedes-Benz plant in Untertürkheim. This is where the complete drive unit is produced according to the traditional Mercedes-AMG "one man, one engine" principle. The complex fuel cell system production has an intelligent control system. For example, our technicians receive digital instructions for every working and testing stage, the tool and equipment control system is supplied with the requisite settings and every stage is immediately electronically documented online. The hydrogen tank system is assembled at the Mercedes-Benz plant in Mannheim.

At present the hydrogen for fuel cell drive systems is still mainly obtained from fossil energy sources such as natural gas. This is not really "green" yet, is it?

Mohrdieck: Agree, but this is only a first step to show that locally emission-free driving with fuel cell technology could be a real alternative. Even with hydrogen obtained from natural gas, CO2 emissions in the overall chain can be reduced by a good 25 percent. The important thing is that it can be produced on a "green" basis. There are already plenty of approaches to achieving this. Hydrogen is the ideal energy storage medium for wind and solar power, both of which are not generated continuously. With the constantly growing proportion of renewable energy, hydrogen will play an increasingly important part in the overall energy system and therefore become more and more attractive for the mobility sector.

This is also where your involvement in stationary fuel cell systems comes into play?

Mohrdieck: Precisely. The potential of hydrogen beyond the automobile - e.g. utility, industrial and domestic solutions – is manifold and requires the development of new strategies. Economies of scale and modularisation are important factors in this. Together with our innovation incubator Lab1886 and computer experts, we are currently working on the development of prototype systems for the (emergency) power supply of computer centres and other stationary applications. For this purpose we use the fuel cell systems of the GLC F-CELL pre-series vehicles.

Where will the fuel cell go in the future? When can we expect a breakthrough?

Mohrdieck: We are only at the beginning. I think that by the middle of the next decade – but certainly after 2025 - the relevance of the fuel cell will generally increase, and significantly for the transport sector. By this I don't mean a sudden explosion, as it will still probably only account for a single-figure percentage of the global market. But even moderate volumes will help to create standards that are especially essential for cost reduction. We must never forget: for a technology to achieve a breakthrough, it must be attractive for both sides – the customer and the manufacturer.

What still needs to be done? What are the next steps?

Mohrdieck: We need industrial standards to progress to very large vehicle production volumes. Further development work is particularly necessary to reduce material costs: Factors in this include the further reduction of sizes and components, and also of the proportion of expensive materials. If we compare our present system with that of the B-Class F-CELL, we have already achieved a great deal – alone by reducing the platinum content by 90 percent. But we need to go further. Process optimisations in production will also help to lower costs – but this is more a matter of economies of scale. Cooperation in cross-manufacturer projects such as "Autostack Industrie" and expected worldwide investment in the technology will certainly contribute to this.

Will the fuel cell also be used in other vehicle segments as a next step?

Mohrdieck: To use the fuel cell across other automotive segments and in large volumes in the future, our task is now to develop our basic module further so that it can be even more efficiently integrated into our group-wide electric modular system. This would give us maximum flexibility. The systems could then be variably combined with different battery sizes, and therefore used for any operating profile whatsoever.

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