Experimental Studies on the Influence of Operational Parameters on the Cold Start of a 2 kW Fuel Cell

Abstract

Abstract In this paper, experimental investigations on the influence of operational parameters on PEM fuel cell cold start are presented. The effect of current density, stack impedance at 1 kHz prior to start, as well as gas flow rate, gas pressure, coolant flow rate and surrounding subfreezing temperature are studied. The experimental apparatus is briefly described. It includes a main unit at room temperature and a smaller separate unit in a climatic chamber. Low current density, high impedance prior to start, moderate subfreezing temperature (–5 °C), high gas flow rate, low gas pressure and low coolant flow rate are found to have a positive impact on the cold start performance. Combining these parameters, self start‐up of the fuel cell without additional energy is achieved at –5 °C in 30 min. The whole set of observations leads to the following hypotheses on freeze mechanism: in the first phase, dry membranes and low current lead to a transient phase of membrane humidification. Then, in the second phase, ice clogging of the active layers occurs. In the third phase, a variable quantity of the produced water reaches the gas diffusion layers and channels.

Key findings

• ▸Low current density improves cold start performance.
• ▸High impedance prior to start has a positive impact on cold start performance.
• ▸Combining optimal parameters enables self-start-up without additional energy.

Keywords

Identifiers

DOI

10.1002/fuce.200700067

Journal

Fuel Cells

Year

2008