Hochschule Bremen - University of Applied Sciences

Hochschule Bremen

Dynamic Response of the PEM Fuel Cell to Step Change Load

Beitrag auf Tagung

Natur und Technik

Smolen, Slawomir, Prof. Dr.-Ing.


Name(n), Titel

Weitere Informationen zur Veranstaltung
XIX International Symposium, Research - Education - Technology,
Special Session: Low Temperature and Waste Heat Use in Communal and Industrial Energy Supply Systems, Proceedings,
Hochschule Bremen, September 2009

Haus der Wissenschaft, Bremen

September 2009

Dynamic Response of the PEM Fuel Cell to Step Change Load
PEM fuel cells are viewed as one of the most environmentally friendly propulsion systems for automotive travel in the future. However, the output load and environmental conditions under which PEMFC operates are not constant. Thus, in order to provide references for the practical manufacture and operation of PEMFC, it is necessary to know the dynamic response of the PEMFC under variable loading and different operating conditions.
In the present paper dynamic characteristics of a single PEMFC under step change load are reported.
The system tested is based on two fuel cell units (1.2 kW each), methanol reformer (Genesis Fueltech 20L), DC/DC converter, DC/AC inverter, microprocessor control unit, electronic load, gas cylinder hydrogen supply system and set of measurement instruments.
The Nexa power module produces unregulated DC power for interfacing with external power conditioning equipment. A single fuel cell element produces about 1 volt at open-circuit and about 0.6 volts at full current output. The Nexa fuel cell stack has a total of 47 fuel cells in series. The geometric area of the single cell is equal to 120 cm2.
Scheme of the tested PEMFC system is shown in Fig. 1.

Figure 1: Scheme of the PEMFC system; 1 – FC system, 2 – filter, 3- IGBT DC–DC converter, 4 – resistive load

To observe the dynamic behavior of the FC the following types of loads were used: resistive and resistive-inductive. The load was provided with the aid of an in-house-developed electronic load unit, which was fully computer controlled.
The fuel cell can be operated in the stand-alone or in the grid parallel mode. In this study, experimental results are obtained when the fuel cell was operated in the stand-alone mode.
As an example Fig. 2 shows stack voltage response under step change load of different amplitudes and Fig. 3 time needed to reach a steady-state performance after load application.
Voltage Response
Figure 2: Stack voltage response under step change load of different amplitudes
Response Time
Figure 3: Response time for step change load of different amplitudes

As can be seen in Fig. 2 for step change load with amplitudes up to 45 A current output, after some time (response time) stabilizes displaying only small disturbances. However, for step change load with amplitude equal to 50 A stack has displayed almost sinusoidal course.



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