Effect of startup modes on cold start performance of PEM fuel cells with different cathode flow fields

TL;DR

This study compares the cold start performance of PEM fuel cells with metal foam and serpentine flow fields, highlighting the benefits of variable current modes and specific flow field designs for improved cold start behavior.

Contribution

It introduces a variable current mode considering heat and water production, demonstrating improved cold start performance of PEMFCs with metal foam flow fields.

Findings

Metal foam flow fields outperform serpentine flow fields at 0.3 V in cold start.

Increasing current density during unsaturated stages enhances heat production.

Variable current mode improves cold start by balancing heat and water management.

Abstract

Proton Exchange Membrane Fuel Cell (PEMFC) is widely recognized for its cleanliness and high efficiency, but is still facing challenges in cold environments. At low temperatures, the formation of ice and repeated freezing/thawing cycles may cause cell performance reduction and irreversible degradation. The cathode flow field of PEMFCs has a significant effect on the performance. In contrast to the conventional ``channel-ridge'' flow field, the metal foam has the advantages of excellent pre-distribution of gases and water drainage, which make it a promising candidate for the cold start. This paper examines the cold start of PEMFCs with metal foam flow field (MFFF) and serpentine flow field (SFF), and the influence of constant current mode, constant voltage mode, and ramping current mode is investigated experimentally through performance test and electrochemical characterization. The results show that lowering the voltage and increasing the current can enhance the cold-start performance of fuel cells. The MFFF fuel cell has superior cold start performance compared to the SFF fuel cell under the constant voltage mode of 0.3 V. Furthermore, the variable current mode is developed by considering the distinct properties of heat and water production during various phases, and the results indicate that increasing the current density at the unsaturated stage leads to an elevated rate of heat production and a reduced rate of water production, which can improve the cold start of PEMFCs.