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Materials and designs for improved freeze-start capability and prevention of freezing damage in fuel cells

Applicant Boillat Pierre
Number 185085
Funding scheme Project funding (Div. I-III)
Research institution Paul Scherrer Institut
Institution of higher education Paul Scherrer Institute - PSI
Main discipline Chemical Engineering
Start/End 01.07.2019 - 31.12.2022
Approved amount 606'671.00
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All Disciplines (2)

Discipline
Chemical Engineering
Physical Chemistry

Keywords (5)

Freeze damage; Fuel cell; Super-cooled water; Durability; Electrochemistry

Lay Summary (French)

Lead
Prévention et réduction des dommages liés au gel dans les piles à combustibles
Lay summary
Les véhicules électrique ont récemment attiré l'attention du public comme un élément clé de la dé-carbonisation du secteur des transports. La plupart des véhicules utilisent une batterie comme source principale d'énergie, mais des modèles de véhicules fonctionnant à l'aide d'une pile à combustible ont récemment été mis sur le marché. Cette dernière solution offre d'importants avantages comme une plus grande autonomie et le fait que la source d'énergie n'est pas une batterie que l'on doit recharger, mais un combustible - l'hydrogène - dont le réservoir peut être rempli en quelques minutes. Dans le cadre de ce projet, nous nous attaquons au défis présentés par le démarrage et le fonctionnement des piles à combustible à des températures négatives. Bien que des constructeurs aient démontré que le démarrage à des températures aussi basses que -30°C est possible, la question des dommages encourus par la pile dus au gel de l'eau sont toujours inconnus. Notre approche consiste a développer des matériaux et des architectures de piles permettant d'éviter le gel, ou de le confiner dans certaines régions de la pile.
Direct link to Lay Summary Last update: 03.07.2019

Lay Summary (English)

Lead
Freezing damage prevention and mitigation in fuel cells
Lay summary
Recently, the introduction of electric vehicles has experienced a significant leap forward and attracted public attention, and are considered a key element in the de-carbonization of the transportation sector. Besides the well known battery powered vehicles, fuel cell powered vehicles have recently be made commercially available. The latter offer interesting advantages due to their larger autonomy and the fact that they operated on a fuel - hydrogen - allowing refill in a few minutes. In this project, we address the challenge of starting and operating fuel cells at minus temperatures. While startup from -30°C has been demonstrated by vendors, the damage induced to the cells by sub-zero startup or by repetitive excursions to minus temperatures with a shut down car is still unknown. Our approach consists in developing materials and cell designs which will delay the freezing of water or mitigate its effect by confining it in defined regions.
Direct link to Lay Summary Last update: 03.07.2019

Responsible applicant and co-applicants

Employees

Name Institute

Associated projects

Number Title Start Funding scheme
143432 Synthesis and characterization of porous materials with patterned wettabillity for advanced fuel cell water management strategies 01.04.2013 Project funding (Div. I-III)
172474 Porous materials with patterned wettability for advanced fuel cell water management strategies: improvement of durability and in situ performance 01.04.2017 Project funding (Div. I-III)

Abstract

Polymer electrolyte fuel cells (PEFCs) are electrochemical energy converters characterized by their high efficiency and by the absence of pollutant emissions at the point of use. As such, they provide an interesting alternative to internal combustion engines in automotive applications. The product of the electrochemical reaction is water. Therefore, starting up PEFCs at temperatures below the freezing point poses several challenges. Frost accumulating in the electrodes can block the access of gaseous reactants, and freezing of liquid water can induce damage by volume expansion. The latter is not only a concern during the startup, but also for the withstanding of sub-freezing temperatures in the presence of residual water from previous operation. While the ability to start at temperatures as low as 30°C is reported in car specifications [1], there are still important unknowns about the behavior of water in fuel cells below the freezing point. In particular, the presence of super-cooled water has been identified and is increasingly being taken into account in scientific studies, but the exact role it plays during sub-zero degree startups and in particular its impact on fuel cell durability is yet to be unraveled. The proposed project aims not only at obtaining a better understanding of the behavior of super-cooled water in fuel cells, but also at identifying how materials can be selected or modified to improve the stability of the super-cooled state to prevent freezing. A further important aspect which will be considered is the prevention of freezing propagation: our previous research did show that cells with a small active area (e.g. 1 cm2) can operate at temperatures below the freezing point for long times (e.g. more than 1 hour) before freezing. The reason why this is not possible in larger cells is attributed to the higher probability of freezing initiation due to the larger amount of water, and to the fact that, once initiated in a random location in the cell, freezing will propagate to the entire cell. Materials and designs promoting the disruption of the liquid water network will be studied in order to avoid the propagation and thus strongly reduce the probability of freezing for a given location in the cell - and thus avoid freezing damage during either startup or passive freeze-thaw cycles in presence of residual water. The proposed studies will be supported not only by state-of-the art commercial test equipment, but by with our custom test cell for in situ calorimetry studies as well as by the recent developments realized in neutron imaging for the in situ distinction of liquid and ice distribution.
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