A fuel cell system model has been developed to predict the performance of a methanol reformer fuel cell vehicle, including warm-up operation. This model includes a methanol steam reformer, catalytic burner, gas clean-up unit, 75 kW PEM fuel cell stack and auxiliaries such as a blower to supply air to the burner and a compressor to supply air at 300 kPa to the fuel cell. The model has been used to simulate a four-door passenger car, weighing 1500 to 1800 kg, operating over the FTP drive cycle from a cold start. The resulting fuel economy has been predicted in terms of ltr/100 km (and miles per US gallon). During the FTP cycle, the reformer and gas clean-up unit took over one minute to warm up, depending on the system characteristics. Therefore, in order to provide acceptable cold start performance, an energy storage device is needed to power the vehicle before the fuel cell stack can be switched on. In this study, the energy storage device chosen was a nickel metal hydride battery. The minimum battery capacity was found to be 1 Ah at 280 V. Effects of the reformer thermal capacity and of the variation of the methanol flow rate to the burner were examined with respect to the reformer warm-up time. For example, reduction in the thermal capacity from 72 kJ/K to 27 kJ/K was found to decrease the warm-up time by 50 % at a constant burner methanol flow rate. This has the beneficial effect of reducing fuel consumption over the FTP drive cycle by 17 %. Increasing the burner capacity and hence the burner methanol flow rate, had a small effect on the fuel consumption but gave a significant reduction in the battery size required. The best fuel consumption figure, 27 miles per US gallon, is poor when compared to the PNGV (partnership for a new generation of vehicles) target of 80 miles per US gallon. The fuel cell itself may be more efficient than an IC (internal combustion) engine but it is compromised by the energy required to warm up the reformer and the size and weight of the complete powertrain and auxiliaries. The efficiency of fuel cell vehicles will be improved considerably by developments such as improved fuel processor units and transient control strategies, which can be optimised using a model such as the one presented.
Warm-up strategies for a methanol reformer fuel cell vehicle
Warmfahrstrategien für ein Brennstoffzellenfahrzeug mit Methanolreformer
2000
6 Seiten, 8 Bilder, 7 Quellen
Conference paper
English
Betriebstemperatur , Brennstoffzelle , Dauerfestigkeit , dynamisches System , Fahrzeugantriebsart , Gewicht , Hilfseinrichtung , Kaltstart , komplexes System , mathematisches Modell , Methanol , Reformer , Reinigung von Gasen , Simulationsmodell , Systemvergleich , Treibstoffverbrauch , Wärmekapazität , Wasserstoff , Wirkungsgrad , Zuverlässigkeit
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