Management Q&A

DaimlerChrysler’s Prof. Kohler argues for diesels over hybrids and lays out his views on hydrogen fuel cell vehicles.

An engineering graduate from Stuttgart University, Prof. Dr. Kohler joined Daimler-Benz AG in 1976. As vice president, body and powertrain research, and chief environmental officer, he is responsible for DaimlerChrysler AG’s propulsion, body, materials and production technology, as well as environmental policies.

Q. What is your opinion of hybrid vehicles?

A. Our strategy is that it is a bridging technology from one technology to another, no more, no less. The hybrid is very efficient for traffic situations with a lot of stop-and-go activity. You can reduce fuel consumption very efficiently, but only in those kinds of driving conditions. It is difficult to regain braking energy when driving in the countryside where there is no stop and go. If you compare hybrid and diesel engines on a practical day-to-day use basis, the advantage of hybrids is reduced to a minimum. There is maybe even a slight increase in energy consumption.

Also, if you look at consumer reports coming from the U.S. especially, the reality is that there is disappointment with fuel consumption, which is very different from that touted. Therefore, customers will be aware and there will be a problem in the future to convince people to stay with this technology. On the social side, it is hip to have that kind of a car, but there will be a counter reaction and we have to take this into account. It still makes sense to convince people to use diesel technology, in the U.S. as well.

Q. What are your priorities with powertrain development?

A. We are working very efficiently with conventional powertrains to reduce fuel consumption and emissions. We need to focus on both these topics for competitive reasons. Also, over the last five to eight years we have been thinking about specific fuels for specific technologies. When we introduced a new after-treatment system in the past it was very important to reduce fuel sulphur content. In the last two years we have learned a lot regarding reduced concentration of sulphur or aromatics in fuel. We know much more about how soot is being generated in the combustion process and how sulphur is one of the catalysts for producing soot inside the combustion process. Therefore, one of the future requirements is to have very pure fuels.

There is an opportunity for fuel to be produced from biomass. Progress is very promising with the chance to reduce soot 50 percent, reduce NOx and reduce fuel consumption without any adaptation of the powertrain. We see more and more possibilities behind that kind of technology.

Q. What is your strategy in terms of fuel cell vehicles?

A. Today we are focused on conventional powertrains, but if you look back at the history of energy it is always an evolutionary process from one technology to the next. So we will stay with conventional powertrains and in parallel to that we will have more and more cars with alternative powertrains, with special focus on fuel cell vehicles. As far as meeting the goal of zero-emission vehicles, there is no doubt the fuel cell is the best option and also for using energy most efficiently in comparison to a conventional powertrain.

Q. What progress are you making with the development of hydrogen fuel cell vehicles?

A. Our progress with fuel cell propulsion systems over the past 10 years has been very intensive and very good. On the other hand, we know there are still deficits regarding reliability and cold start. However, we have the technology to solve the cold-start problem. It is feasible to minus 20 degrees, where you can drive the vehicle within one second and have 80 percent of the energy after 30 seconds.

Q. What about the cost problems associated with fuel cells?

A. Cost is always related to the high technology and materials. But if we compare the situation versus three years ago, we have been able to reduce costs by 90 percent. We still have to make further drastic reductions, focusing especially on the platinum we are using as a catalyst in the fuel cells. The intention is to lower costs using thinner layers and better production methods.

Q. What is your opinion of the most promising hydrogen storage methods?

A. Currently we have fuel cell vehicles with 300-400 km range. We’re making progress but it is not good enough. We see technologies that will get us to 500 km, which will be in common with normal propulsion systems.

On the compressed hydrogen side, we are looking at pressures up to 750 bar, and we are looking at the possibilities on the liquid storage side. We know the problems — losses from liquid to gaseous phases — but there is the possibility for greater driving range. This is a game that is not over yet.

As for the storage tanks, it’s important to find a better geometric construction than we have today. A cylinder is not that efficient a shape to accommodate in a car. So we are looking at least to flatten the side of the cylinder in order to package more efficiently.