Clean Traffic with Hydrogen

Traffic accounts for about a third of the entire energy consumption in Germany. Currently, fuels originate from fossil sources and contribute largely to the emission of gases harmful to the environment and human health. In the future, technologies that do not or nearly do not emit carbon dioxide and which save the finite resources will be needed.

Hydrogen as a fuel is the most viable option to realise a sustainable mobility. It can be used in modified internal combustion engines (ICE) as well as in fuel cells that produce electricity for an electric motor. Here, neither pollutants like sulphur oxide nor greenhouse gases are emitted. Water vapour is the only "exhaust fume" (and nitrogen oxides in ICEs respectively).

Hydrogen driven fuel cell cars have a higher energy-efficiency than normal ICE due to a better degree of efficiency during partial load operation (see right figure). In addition, fuel cell based engines are quieter and, therefore, enhance local air and living quality - especially in urban areas.

When thinking on a global scale it has to be remarked, though, that hydrogen itself is not a primary energy carrier and needs to be produced by using energy. Hence, the environmental effects of both the production and use of hydrogen have to be assessed along the entire production chain and be compared to those of petrol, diesel or natural gas. Such "well to wheel"-analyses have shown that from the environmental perspective the use of hydrogen only makes sense when the hydrogen is solely or at least largely being produced from renewable energies. If not, the emission of gases harmful to the environment and human health is only relocated from the exhaust to the production place of the hydrogen.

Another advantage of the environmental friendly production of hydrogen is the long-term independence from mineral oil.

However, hydrogen has only a very low energy density per volume under normal conditions. In order to achieve a driving range of several hundred kilometres for vehicles, the gas needs to be compressed ("compressed hydrogen (CH2)" up to ca. 700 bar) or to be cooled down and liquefied. To offer the driver the same driving range, hydrogen as a fuel still takes up more than three times the space of petrol or diesel.

All large car manufacturers are testing cars using hydrogen and fuel cell technologies. PLANET is involved in the CUTE project (Clean Urban Transport for Europe). It features the world largest trial of a fuel cell bus fleet and its hydrogen refuelling infrastructures in day to day operation in nine European cities.

Diagram of a fuel cell bus (photo: DaimlerChrysler)

Qualitative comparison of efficiencies of ICE and fuel cell drives

Selected publications on this topic

Th. Feck, R. Steinberger-Wilckens, K. Stolzenburg
Wasserstoff - Zündschlüssel für den nachhaltigen Verkehr?
Sonne Wind & Wärme, Heft 4/2002.

R. Steinberger-Wilckens
Wasserstoff - Grundlage für schadstofffreien Fahrzeugverkehr
GWF Gas Erdgas, 142 (2001) Nr. 7.

R. Steinberger-Wilckens:
Der Aufbau einer Infrastruktur für Wasserstoff als Treibstoff - Wie kann es gehen?
VDI-Bericht 1704 „Innovative Fahrzeugantriebe“ (2002), 315 - 328, VDI-Verlag, Düsseldorf, ISBN 3-18-091704-0.

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