At present, the use of low temperature fuel cells (especially PEMFC) as the power source in zero-emission vehicles (ZEV) is a topic that is discussed intensively against the background of California legislation. To attain a trouble-free running, the polymer fuel cells in these cars need CO-free hydrogen which is today provided by means of a pressure gas reservoir. Due to the low energy density of high pressure hydrogen (GH2), the driving range of cars operated by fuel cells is limited. In order to achieve greater ranges, the hydrogen that is on board the car must be produced out of a suitable storage material. Possible storage media are, for example: liquid hydrogen (LH2), metall hydride (saline or metallic), natural gas or methanol, or base materials (for example Fe). The storage of liquid hydrogen has a very high energy cost due to liquefaction. Furthermore, one has to take into account greater evapoation losses of hydrogen at refuelling places and from the vehicle tank. Low temperature metal hydrides (Ti/Fe-base) generally have a high specific gravity; due to the endothermic reactions when hydrogen is released heat must be supplied by use of a large and expensive heat exchanging system. Expensive high temperature hydrides based on magnesium need very pure hydrogen, besides that the reaction heat demand at temperatures above 300 deg C has to be supplied by combustion of a part of the released H2. The generation of hydrogen from natural gas or methanol through steam reforming or partial oxydation (POX) is a process which is only economical in large scale facilities. When scaling down the technology for vehicle applications, the process step 'removal of CO' in a preferential oxydation (PROX) reactor is causing the greatest difficulties. In addition, the dynamic behaviour of the hydrogen source is still unsatisfactory and its specific weight to high.
Investigations of the kinetics and catalysis of the iron/steam-magnetite/hydrogen-system in low temperature regime with regard of its use to produce and store hydrogen
Kinetik- und Katalyseuntersuchungen eines Eisen/Dampf-Magnetit/Wasserstoffsystems im Niedrigtemperaturbereich unter Beachtung einer Verwendung zur Herstellung und Speicherung von Wasserstoff
1996
9 Seiten, 9 Bilder, 2 Tabellen
Aufsatz (Konferenz)
Englisch
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