Technology Status of Hydrogen Road Vehicles

In vehicular applications, the FC system must supply power on demand in a highly variable load profile e.g.
zero to full power in seconds. The FC itself has a response time of milliseconds; the H 2 supply is passive by
static pressure; but the oxidant (usually air) must flow through the stack to remove the inerts (usually nitrogen)
and product water. Although high air pressure and flow are beneficial to FC performance, the compressor
power reduces overall performance.
Three air control strategies were simulated: constant pressure and flow; constant pressure and variable flow;
and variable pressure and flow.
The first strategy is the simplest, and was adopted for the car of Item 13 Table 1, but gives considerably lower
efficiency especially at low loads (the fuel consumption is at least doubled up to 12.5% load) compared to the
other two strategies, which are essentially equivalent. From 50% load up, all three strategies have similar fuel
consumptions, the slightly better one of the third strategy being compensated by the disadvantage of special
compressor development specific to this application.
The second strategy is therefore the most indicated one, giving an overall efficiency higher than 37% at full
load compared to about 22% for the first one.
Wurster, R., et al., “Feasibility Study on Fuel Cell Propulsion for Urban City Buses and Delivery
Trucks,” LBST, Neoplan, MAN, Magnet-Motor, Daimler-Benz, Siemens, ESTW, Linde, SWB, all in
Bavaria, Germany, pp. 1707-1716.
Two PEM FC buses are apparently now decided on the basis of the feasibility study and concepts reported
here. Hardware procurement started early 1996. Two buses--one each from Neoplan and MAN--should be
ready by early 1999; a delivery van from MAN may be decided at a later date. The city of Erlangen in
Bavaria, where the MAN bus of Item 3 Table 1 is now in regular operation, is a probable choice for the
demonstration. The state government of Bavaria and the federal government of Bonn have been asked to cofinance
50% of the entire activity.
The costs of the project (including the two demonstration buses, the peripheral equipment, and a 6-month test
phase) will be about 20 million DM, the most costly component being the fuel cell system.
A selected summary of the most important characteristics follows:
1. The MAN bus will have a 120-180-kW PEM-FC powering a central drive motor.
2. The Neoplan bus will have a 60-90-kW Siemens PEM FC in hybrid combination with magneto-dynamic
flywheel of Magnet-Motor (2 kWh, 150 kW short-term average), powering two wheel-mounted drive
motors.
3. Both buses will have a passenger capacity of 100 persons, a length of 12 m, a total weight of 18 tonnes,
and low floor layout (100% in the Neoplan case because of wheel-mounted drive motors).
4. GH 2 at 25 MPa in 12 fully composite roof-top cylinders (total 2.2 m 3 ) gives each bus a range of 120-300
km/d with daily refueling.
5. The FC module in each case is expected to have an overall net efficiency (based on the lhv of H 2) of ~55%
at full power, and a maximum of ~63% at ~20% power. Air will be supplied at 0.15 MPa.
Schmidt, V.M.; U. Stimming, “Hydrogen and Methanol Proton Exchange Membrane Fuel Cells,”
Forschungszentrum Jülich, Germany, pp. 1717-1725.
This paper presents concept studies, as well as test results, on CO-tolerant catalysts.
The PEM and A FCs are the only ones for relatively low-temperature operation (60º-100ºC), so good for
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