The long-lasting paradigm that cars run on gasoline and trucks run on diesel has been challenged by various hypes over the past two decades. These included electric, natural gas and hybrid vehicles, yet conventional engines still dominate on the road. Why?

Ultimately, this is due to basic principles of physics: gasoline and diesel (and compressed natural gas) can be stored on-board with a high energy density allowing for long-range travel. Contrarily, batteries have a much lower energy density (by a factor of 20), so that they are favorable especially for traveling shorter distances.

Of these past hypes, only hybrid vehicles have become established thus far, as they combine the advantages of electric and conventional motors for covering both short and long journeys. Hydrogen and fuel cells have the potential to cause the next wave of excitement. However, efficiency losses due to multiple conversion steps may favor the direct utilization of electricity, a requisite for hydrogen production.

Regardless of the energy carrier, it is important to take into consideration the energy input and CO₂ emissions not only of operating the vehicle (tank-to-wheel), but also of producing its energy carrier (well-to-wheel). Using the well-to-wheel approach, electric cars or fuel cell vehicles are only more climate-friendly if electricity from renewable sources is used. In the future, all energy carriers may be based on renewable sources so that the total CO₂ footprint of the vehicle should be the essential criterion.

Read the entire eco2friendly article (in German). The article is based on an excerpt from the book Energiewende published by EBP, vdf Hochschulverlag an der ETH Zürich (ISBN: 978-3-7281-3827-9).

Konstantinos Boulouchos is Head of SCCER Mobility and Professor for Aerothermochemistry and Combustion Systems at ETH Zurich. Peter de Haan heads the Resources, Energy + Climate Division at EBP.

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