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Title: A nature-inspired approach to robust fuel cell design with water management
Author: Cho, In Sung
ISNI:       0000 0004 7965 0750
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2019
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Polymer electrolyte membrane fuel cells (PEMFCs) are a promising alternative source of energy conversion for a wide range of transport, portable, and stationary power applications, due to their high efficiency, low operating temperature, and high power density. However, there remain challenges to broader commercialisation of this technology, including high electrocatalyst cost, performance limitations associated with unoptimised flow-field designs, and water management. Here, a lung-inspired approach is employed to overcome reactant homogeneity issues in PEMFCs. The characteristics of the lung that allow uniform gas distribution via an optimised fractal structure linking bronchi to alveoli, and realising a remarkable combination of minimal entropy production, low pressure drop, and scale-invariant operation, serve as a guide towards the proposed design of fractal flow-fields for PEMFCs. A theoretical model is developed and simulations are conducted to determine the number of generations required to achieve uniform reactant distribution and minimal entropy production. Guided by the simulation results, three flow-fields with N = 3, 4, and 5 generations are fabricated using 3D printing via direct metal laser sintering. The lung-inspired flow-field with N = 4 generations outperforms the conventional serpentine flow-fields while maintaining lower pressure drop. The fractal flow-field with N = 5 generations on the other hand, exhibits excess flooding at high humidity operating conditions. In situ water visualisation via neutron radiography reveals susceptibility to flooding of the fractal flow fields, due to the lack of convective gas flow requisite for effective liquid water removal, resulting in significant water accumulation in the interdigitated outlet channels. Hence, a novel water management strategy is developed that uses capillaries to control liquid water in PEMFCs. The proposed mechanism serves as a simple and effective means of achieving robust and reliable fuel cell operation. Implementation of this water management strategy is expected to circumvent remaining problems of high-generation fractal flow-fields.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available