Farewell Combustion Engines – Or Maybe Not?

The vehicle drive systems of the future

One of the first vehicles ever developed by Ferdinand Porsche, the Lohner-Porsche, was an electric car with batteries weighing around 1.8 tons. The tires were so overloaded that they burst and the driving range was so poor that the inventor developed the Mixte Hybrid, which combined a combustion engine with an electric motor. This hybrid was too expensive, however, so that Porsche also eventually moved on entirely to drives using combustion engines. With the introduction of the VW Beetle, Porsche succeeded in developing a reliable mass-market product and the combustion engine became the dominant drive technology throughout the world. So what will happen in the future?

The automobile has become an indispensible part of modern life in industrial nations and it is central to our standard of living, resulting in “worldwide mass-motorization.” But as pollutant emissions have led to environmental problems, especially in urban areas with smog, and as the belief has intensified that carbon emissions are causing global warming, the powers that be have introduced radical legislation to reduce fuel consumption and emissions, laws that can only be addressed through huge investments in classic combustion engine technology. With each round of tighter legislation, the outlay on technology rises, so, as a result, the experts are now developing alternative vehicle drives.

Electric drives use fuel cells and convert hydrogen (H2) or methanol, the energy sources, into electric current. Using hydrogen results in no harmful gas emissions and storing H2 is technically complex but this issue has since been resolved and the first promising prototypes do now exist. The driving range and duration on a full charge are also not a problem. Producing H2 using regenerative electricity is currently under development and appears to be technically feasible.

Another interesting option is the electric drive using electrochemical storage (rechargeable batteries). This makes many of the electric cars that have been introduced in recent years an appealing option, with rapid acceleration, no sudden jolting into motion, a scarcely significant engine noise and no pollutants at the point of source. On the downside, this option offers limited driving range, the batteries add significant weight, it takes a long time to “fill up” and it’s expensive. These drawbacks will quite possibly be reduced to reasonable levels within a matter of years, so it could become possible to travel outside of cities on battery power alone. But this does not solve the problem with the primary energy consumption (including vehicle production and power generation) which in all probability will not go down one iota versus comparable vehicle drives based on petrol or diesel engines. Because electricity has to be available at all times, it is not possible to produce electrical energy through 100% renewable sources, so this also causes carbon emissions. Even with an optimistic assumption that a large share of renewable sources can be used to generate energy, in comparison to classic combustion systems, purely electric drives will still create more carbon emissions for a long time to come [1].

Combining a combustion engine with an electric drive and thus creating a hybrid engine requires much smaller battery storage. In fact, batteries can be downsized because they use braking energy and only drive short distances. As a result, the cost and added weight of storage units are significantly lower than with a purely electric drive. The combustion engine can also be made smaller because both drives click into action when accelerating and their output is added up. Hybrid drives can cut fuel consumption and emissions because they use braking energy and some driving – for example in urban areas – can be completely emission- free by switching off the combustion engine. This makes this option an attractive way to combine two types of drives. The only drawback is the complex nature of the technology and the correspondingly high cost.

Combustion engines must not be overlooked in discussion regarding the future. The potential of the piston engine, based on the four strokes of a petrol or diesel engine, has yet to be fully exploited. There is still room to make significant improvements in terms of efficiency and emissions. With commercial vehicles, using gas (LNG, CNG) can be particularly advantageous in terms of emissions, energy consumption and costs. Also, new types of synthetic fuels are being developed and this offers ways to reduce emissions and consumption. As a result, the vehicle drive of the future will still be dominated for some time by the combustion engine. But looking back, thermodynamic hydrogen combustion turned out to be a false lead.

Vehicle drives such as gas turbines, the Sterling engine, combustion engines based on two-stroke processes, and eccentric rotary engines (the Wankel engine) could not fulfill expectations for vehicle engines, despite intensive research, so these will have no more role to play in the future.

So what does the future hold for engines? For the next 20 years, the combustion engine will continue to dominate – sometimes in combination with the electric engine, as a hybrid. New types of synthetic fuels will galvanize the position of the combustion engine. The purely electric engine will become established for short-range driving for journeys of up to 200km, but their market share will not be more than 10%. As things stand now, the purely electric engine for vehicles with longer ranges does not make sense from an energy point of view, and because of the manufacturing costs.

If our affluence remains intact – as well as the conviction that carbon emissions are having a negative impact on the global climate – then there will be an opportunity for fuel cell cars in industrialized countries. The technical feasibility is proven and there are some appealing prototypes. But this will all depend on us shifting energy generation to renewable sources, the setting up of a suitable infrastructure for hydrogen and a suitable legal framework to promote the technology. The developing countries – which is where the majority of the world’s population lives – will not be able to afford such expensive technologies, and in those places, the combustion engine will continue to dominate for decades to come.

Contact

Professor Dr.-Ing. Günter Willmerding und Dipl.-Ing. (FH) M. Sc. Jakob Häckh are co-directors of the Steinbeis Transfer Centers for New Technologies in Traffic Engineering and the center Traffic Engineering.Simulation. Software in Ulm. At both Steinbeis Enterprises, most of their work revolves around traffic flow analysis and simulation, drive chain simulation, fuel consumption, emissions, vibration and the design and calculation of new kinds of vehicle components based on R&D methods and service- life forecasting. In 2004, the Steinbeis Transfer Center for New Technologies in Traffic Engineering was awarded the Steinbeis Foundation Transfer Award together with Voith Turbo GmbH & Co. KG.

Professor Dr.-Ing. Günter Willmerding, Jakob Häckh
Steinbeis Transfer Center New Technologies in Traffic Engineering (Ulm)
su0089@stw.de

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