Range Extension for Hybrid Electric Vehicles through Fuel Cell Technology

Jörg Karstedt

Dr. J÷rg Karstedt works with ZBT GmbH where he is the Coordinator of E-mobility. The mass market example of a hybrid electric vehicles is that of a battery matched to a traditional gasoline engine. In this interview, we explore an alternative version of the hybrid electric vehicle; one that would allow for a truly green energy vehicle with the range of a traditional car.

"The combination of fuel cells and batteries enables long distance emission free e-mobility without any range anxiety."

Automotive IQ: Dr. Karstedt, what is your background and how did you get into fuel cell technology?

J÷rg Karstedt: I studied mechanical engineering at RWTH Aachen in Germany and UC Davis in California and did my PhD on automotive fuel cell system development at the Institute for Combustion Engines of RWTH Aachen. Afterwards I was team leader for battery and fuel cell system development at FEV GmbH, which is an international engine and powertrain engineering company. Currently, I’m coordinator for automotive fuel cell system development at ZBT GmbH which is one of the leading German fuel cell research centers.

Automotive IQ: Many people are aware of the potential benefits for vehicle emissions by utilizing fuel cells. One concern has been in the hydrogen production. Are there some strategies for minimizing the energy required to manufacture and store usable hydrogen?

J.K.: Today the established technology for large scale production of hydrogen is steam reforming of natural gas, e.g. for the petrochemical industry. Using hydrogen from steam reforming in fuel cell vehicles still generates carbon dioxide emissions, however, on a well-to-wheel basis, significant emission reductions can be achieved compared to using fossil fuels in internal combustion engines.
In the mid-term, however, hydrogen should be used that is generated via electrolysis from green, renewable energy. This especially makes sense if a large amount of fluctuating renewable energy is available that can’t be stored otherwise e.g. as pumped hydro or in battery electric vehicles.
In order to optimize the well-to-tank efficiencies, not only the electrolyzers but also the hydrogen refueling station designs still have significant potential.

Automotive IQ: Can you give some of the possibilities for fuel cell range extender systems for electric vehicles?

J.K.: Our concept for the fuel cell range extender system is a plug-in hybrid vehicle architecture with a downsized fuel cell system and a reduced battery capacity that minimizes the system cost and also the operating cost. The idea is that the size of the battery system is reduced compared to purely battery electric vehicles in a way that most of the everyday short-distance trips can still be covered by the battery system. In addition, a downsized, low cost fuel cell system is able to provide the average power requirement during highway driving, so that the customer can be offered an emission free e-mobility solution without any range anxiety problems.
With the combination of fuel cells and batteries, a fully long-distance capable and highly efficient electric vehicle can be realized that can be refueled within three to five minutes with hydrogen or - if more time is available - can also be recharged from the grid.

Automotive IQ: That’s exciting. You’ve already started to explain this but how could fuel cells be used in hybrid electric vehicle applications?

J.K.: The alternative to the fuel cell range extender plug-in concept is the "conventional" fuel cell hybrid electric vehicle with a fuel cell system in the power range of 100 kW and a small battery system mainly for regenerative braking.
There are pros and cons for the different concepts.
Fuel cell range extender plug-ins with small fuel cell systems could be a bridging technology in the short- to midterm when no dense hydrogen refueling station network is available and stations are mainly located along the main arteries. From a cost perspective they are especially interesting when battery costs are initially going down faster than fuel cell costs.
With increasing numbers of fuel cell electric vehicles, economies of scale will significantly reduce fuel cell system costs which might then favor fuel cell hybrid electric vehicles with a high power output fuel cell and a small battery system.

Automotive IQ: In terms of weight savings, if you have a big fuel cell tank versus a small battery or a big battery versus a small fuel cell tank, are they comparable in that sense?

J.K.: The combination of fuel cells and batteries enables long distance emission free emobility without any range anxiety. The different OEMs state that fuel cell hybrid electric vehicles become more weight efficient at ranges above approx. 150 kilometers compared to purely battery electric vehicles.

Automotive IQ: So continuing on packaging, you don’t really see a need or necessity to completely redesign the chassis to accommodate the design of the fuel cell?

J.K.: The fuel cell definitely opens up new possibilities in the future because the fuel cell stack itself has become very compact. Some manufacturers are integrating the stack in the tunnel region which opens up the possibility for new vehicle designs. Individual chassis designs are also useful for an easier integration of the hydrogen tanks. However, today the approach of most OEMs concentrates on using existing chassis designs for their fuel cell vehicles to keep costs down especially at low volume production during market introduction.

Automotive IQ: Personally, I can’t wait to see some of the concepts when they come out. This could be really interesting. Shifting a little bit toward policy, what policies might you envision or recommend to help implement fuel cell systems in vehicles?

J.K.: A significant number of fuel cell hybrid electric vehicles in field trials of the various OEMs have proven that the technology meets the customer expectations in every day operation. Fuel cells enable long-distance emission free e-mobility; ranges up to 700 km and short refueling times of 3-5 minutes are achieved. And with the electric powertrain, the vehicles are also fun to drive.
The next important step is to get the infrastructure into place. Increasing the number of stations to 50 as it is planned in Germany until 2015 is a good first step, but some more support for the infrastructure buildup from governments as well as from the involved industries would help.

Automotive IQ: As you know, a few years ago there was a lot of eagerness at some of the auto shows around fuel cell technology and the potential of them. Some of that enthusiasm seems to have worn off in the media. How do you think public perception can be revived to rally around this technology?

J.K.: Public perception that rallies around a technology can turn into disappointment very fast if the vehicles can’t be brought to the market fast enough. A good example was the public hype around battery electric vehicles – the technological progress of purely battery electric vehicles is really impressive, but some of the public enthusiasm has worn off because the people can’t go out and buy vehicles that meet all their requirements. Nevertheless with hybrids, plug-in hybrids and battery electric vehicles the electrification of the powertrain has taken important steps, and meanwhile also fuel cell technology has made significant progress and plays an important role as the emission free long-distance e-mobility solution for the OEMs. For public perception however, the right timing will be crucial. Special attention should now be paid to the infrastructure buildup as it is important to have sufficient refueling stations in place before people can start to go out and buy fuel cell vehicles.

Automotive IQ: Thank you for the interview and for your insight.

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