Investigation of Mass Transport Phenomena in Polymer Electrolyte Membrane Water Electrolysers PDF Download
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Author: Jude Olaoluwa Majasan
Publisher:
ISBN:
Category :
Languages : en
Pages : 199
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Book Description
Polymer Electrolyte Membrane Water Electrolysers (PEMWEs) are considered a promising candidate for large-scale renewable energy storage and green hydrogen production. To improve efficiency and minimize cost for large-scale deployment, operation at high current densities is necessary. However, a consequence of high current density operation is increased mass transport hindrance which degrades performance. Two components are critical to mass transport in PEMWEs, namely the porous transport layer (PTL) and the flow-field plates. Both are expected to transport liquid water, product gases, electrons, and heat with minimal fluidic, thermal and voltage losses. However, the influence of morphology and configuration of both these components and operating conditions on cell performance are not well understood. This research investigates the mass transport phenomena in the PTL and in the flow-field channels in relation to performance in PEMWEs. The influence of flow-field configuration and two-phase flow characteristics in the flow channels on performance was studied by combined high-speed optical imaging and electrochemical characterization at various operating conditions. Results showed a strong correlation of performance with the flow path length and flow regime. Further, a correlative ex-situ X-ray tomography and in-situ electrochemical characterization approach was used to investigate the influence of PTL microstructural parameters such as mean pore diameter, pore size distribution, porosity, tortuosity, and porosity distribution on performance. Results indicated that minimizing contact resistance is most beneficial for improved performance over the range of current density studied. The influence of flow channel depth on performance was investigated by electrochemical impedance spectroscopy and a design of experiment (DoE) approach was employed to investigate the relative importance and interaction effects of mass transport factors on cell performance. Results showed the water feed rate and two-way interaction between the flow-field and PTL are most significant. This study provides enhanced understanding of the mass transport characteristics in PEMWEs for optimized design and improved performance.
Author: Jude Olaoluwa Majasan
Publisher:
ISBN:
Category :
Languages : en
Pages : 199
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Book Description
Polymer Electrolyte Membrane Water Electrolysers (PEMWEs) are considered a promising candidate for large-scale renewable energy storage and green hydrogen production. To improve efficiency and minimize cost for large-scale deployment, operation at high current densities is necessary. However, a consequence of high current density operation is increased mass transport hindrance which degrades performance. Two components are critical to mass transport in PEMWEs, namely the porous transport layer (PTL) and the flow-field plates. Both are expected to transport liquid water, product gases, electrons, and heat with minimal fluidic, thermal and voltage losses. However, the influence of morphology and configuration of both these components and operating conditions on cell performance are not well understood. This research investigates the mass transport phenomena in the PTL and in the flow-field channels in relation to performance in PEMWEs. The influence of flow-field configuration and two-phase flow characteristics in the flow channels on performance was studied by combined high-speed optical imaging and electrochemical characterization at various operating conditions. Results showed a strong correlation of performance with the flow path length and flow regime. Further, a correlative ex-situ X-ray tomography and in-situ electrochemical characterization approach was used to investigate the influence of PTL microstructural parameters such as mean pore diameter, pore size distribution, porosity, tortuosity, and porosity distribution on performance. Results indicated that minimizing contact resistance is most beneficial for improved performance over the range of current density studied. The influence of flow channel depth on performance was investigated by electrochemical impedance spectroscopy and a design of experiment (DoE) approach was employed to investigate the relative importance and interaction effects of mass transport factors on cell performance. Results showed the water feed rate and two-way interaction between the flow-field and PTL are most significant. This study provides enhanced understanding of the mass transport characteristics in PEMWEs for optimized design and improved performance.
Author: Zhongying Shi
Publisher:
ISBN:
Category : Proton exchange membrane fuel cells
Languages : en
Pages : 404
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Book Description
Author: Gabriel A. Goenaga
Publisher:
ISBN:
Category : Nuclear magnetic resonance
Languages : en
Pages : 168
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Book Description
Author: Dmitri Bessarabov
Publisher: Academic Press
ISBN: 0081028318
Category : Science
Languages : en
Pages : 140
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Book Description
PEM Water Electrolysis, a volume in the Hydrogen Energy and Fuel Cell Primers series presents the most recent advances in the field. It brings together information that has thus far been scattered in many different sources under one single title, making it a useful reference for industry professionals, researchers and graduate students. Volumes One and Two allow readers to identify technology gaps for commercially viable PEM electrolysis systems for energy applications and examine the fundamentals of PEM electrolysis and selected research topics that are top of mind for the academic and industry community, such as gas cross-over and AST protocols. The book lays the foundation for the exploration of the current industrial trends for PEM electrolysis, such as power to gas application and a strong focus on the current trends in the application of PEM electrolysis associated with energy storage. - Presents the fundamentals and most current knowledge in proton exchange membrane water electrolyzers - Explores the technology gaps and challenges for commercial deployment of PEM water electrolysis technologies - Includes unconventional systems, such as ozone generators - Brings together information from many different sources under one single title, making it a useful reference for industry professionals, researchers and graduate students alike
Author: Jin-Soo Park
Publisher: MDPI
ISBN: 303650690X
Category : Science
Languages : en
Pages : 128
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Book Description
This book consists of the nine sections: i) the first three sections are related to polymeric electrolyte composites; ii) the next two sections relate to gas diffusion layers (GDLs); iii) the next two sections relate to membrane¬–electrode assembly (MEA); iv) and the final two sections deal with the numerical simulation of flow fields for polymer electrolyte fuel cells (PEFCs). All sections describe recent results of the study of the main components of PEFC stacks. The studies provide the underlying material, electrochemical, and/or mechanical aspects that enhance the mass transport of gas, ions (liquid), and electrons for a better performance of PEFCs and the electrochemical reactions at the triple-phase boundary in electrodes. Each study offers the fundamentals, a comprehensive background, and cutting-edge technology on the aforementioned materials and mass transport phenomena.
Author: Keonhag Lee
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The design of a porous transport layer (PTL) that exhibits effective two-phase transport characteristics and rigid contact at the catalyst layer (CL)-PTL interface is a prerequisite for improving the efficiency of polymer electrolyte membrane (PEM) water electrolyzers at high current densities (i > 4 A/cm2). In this thesis, key design considerations were presented based on extensive investigations performed via comprehensive numerical models and in operando imaging. A numerical investigation was performed to determine the impact of PTL structures on reactant liquid water delivery to reaction sites. A comprehensive model for designing PTLs was presented, where a stochastic model was used to numerically generate PTLs with realistic morphologies and tunable PTL structures, and a pore network model was used to perform two-phase flow calculations and determine their transport properties. A trade-off relationship was observed between achieving an effective CL-PTL interfacial contact and favourable reactant transport behaviour. Finer powder diameters and lower porosities improved the CL-PTL interfacial contact but led to the reduced permeability of liquid water. Conversely, increasing either powder diameter or porosity improved permeability but deteriorated the CL-PTL interfacial contact. Therefore, it is crucial to consider the operating conditions of an electrolyzer when designing PTLs. Mass transport behaviour in an electrolyzer operating at high current densities was studied using in operando imaging techniques. A sufficient reactant flow rate was essential for mitigating electrolyzer cell failures at high current densities. Specifically, the critical current density was observed when inadequate reactant water was supplied at high current densities. Both gas content in the PTL and mass transport overpotential significantly increased at the critical current density, and the electrolyzer failed to operate beyond the critical current density. Moreover, mass transport in the PTL surprisingly improved when patterned through-pores (PTPs) were implemented with a commercial PTL. The usage of a novel PTP PTL led to the reduced accumulation of product gas at the CL-PTL interface by 43.5%. Furthermore, PTPs led to more frequent gas removal, which subsequently improved water intake to the reaction sites. The findings in this thesis provide valuable insights for designing novel PTLs in PEM electrolyzers operating at high current densities.
Author: Nada Zamel
Publisher:
ISBN: 9780494353677
Category :
Languages : en
Pages : 179
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Book Description
The need for alternative sources of energy with low to zero emissions has led to the development of polymer electrolyte membrane fuel cells. PEM fuel cells are electro-chemical devices that convert chemical energy to electricity by using hydrogen as the fuel and oxygen as the oxidant with water as the byproduct of this reaction. One of the major barriers to the commercialization of these cells is the losses that occur at the cathode due to the slow oxygen diffusion and sluggish electrochemical reaction, which are further amplified by the presence of liquid water. Numerous numerical and mathematical models are found in the literature, which investigate the transport phenomena in the cathode and their effects on the cell performance. In this thesis, the discussion of a two-dimensional, steady state, half cell model is put forward. The conservation equations for mass, momentum, species charge and energy are solved using the commercial software COMSOL Multiphysics. The conservation equations are applied to the cathode bipolar plate, gas diffusion layer and catalyst layer. The flow of gaseous species are assumed to be uniform in the channel. The catalyst layer is assumed to be composed of a uniform distribution of catalyst, liquid water, electrolyte, and void space. The Stefan-Maxwell equation is used to model the multi-species diffusion in the gas diffusion and catalyst layers. Due to the low relative species' velocity, the Darcy law is used to describe the transport of gas and liquid phases in the gas diffusion and catalyst layers. A serpentine flow field is used to distribute the oxidant over the active cathode electrode surface, with pressure loss in the flow direction along the channel. A sensitivity analysis is carried out to investigate the effects of pressure drop in the channel, permeability, inlet relative humidity and shoulder/channel ratio on the performance of the cell. Electron transport is shown to play an important role in determining the overall performance of the cathode. With a serpentine flow field, the oxygen consumption occurs more aggressively at the areas under the land since electrons are readily available at these areas. In addition, the reaction increases along the catalyst layer thickness and occurs more rapidly at the catalyst layer/membrane interface. The losses due to electron transport are much higher than those due to the proton transport. The sensitivity analysis put forward illustrated that with the increase of pressure drop along the channel flow field, the performance of the cell and liquid water removal are enhanced. Similarly, an increase in permeability of the porous material results in an increase in liquid water removal and cell performance. Further, the investigation of the inlet relative humidity effects revealed that the electrolyte conductivity has a significant effect on the performance up to a point. On a similar fashion, a decrease in shoulder/channel width ratio leads to an increase in performance and an increase in the leakage between neighboring channels. Finally, the addition of heat is shown to have a negative effect on the cell performance. Some recommendations can be drawn from the results of this thesis. It is recommended to develop a model to study the flow in the channel flow field in order to investigate the effects of the channel flow on the transport of species in the cell. Further, the geometry of the channel should be studied. Finally, the production of water should be analyzed. The analysis should be extended to investigate its production in vapor form only and its production as a mixture of vapor and liquid.
Author: Maximilian Maier
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: ChungHyuk Lee
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Effective two-phase transport is a prerequisite for achieving high efficiency operation for polymer electrolyte membrane electrolyzers since the undesired accumulation of gaseous oxygen leads to mass transport losses. In this thesis, two-phase flow in the PTL and flow channels were investigated via experimental and numerical techniques to inform new designs and optimize operating conditions. The effect of gas compressibility on displacement behaviour in the PTL was elucidated by studying gas invasion in liquid-saturated microfluidic cells. Smaller pore throat sizes led to larger pore burst velocities, which inspired a new PTL design with engineered pore throat sizes for enhanced gas removal. Next, the gas transport behaviour in the PTL was investigated via a custom microfluidic cell that was based on a realistic PTL microstructure. A unique pore throat was identified where gas snap-off occurred, and the location of this pore throat governed the average gas saturation in the PTL. Next, the temperature-dependent gas saturation in the PTL was investigated using in operando neutron imaging. Increasing the operating temperature led to lower gas saturation near the catalyst layer and PTL interface, resulting in a decrease in mass transport overpotential. To increase the accuracy of anode flow channel visualizations, the nitrogen purging rate was optimized to minimize the impact of purging on cell performance. Excessive cathode purging led to undesired changes in performance, and a minimal purge rate was recommended to achieve accurate through-plane imaging. Lastly, temperature effects on two-phase quality in the anode flow channels were investigated via neutron imaging. A more uniform reactant distribution across the flow channels was observed at higher temperatures, enabling a uniform operating current density across the active area. The main findings in this thesis inform the design of novel PTL microstructure and explain the benefits of higher operating temperature for enhanced mass transport in PEM electrolyzers.
Author: Dmitri Bessarabov
Publisher: CRC Press
ISBN: 1482252325
Category : Science
Languages : en
Pages : 401
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Book Description
An ever-increasing dependence on green energy has brought on a renewed interest in polymer electrolyte membrane (PEM) electrolysis as a viable solution for hydrogen production. While alkaline water electrolyzers have been used in the production of hydrogen for many years, there are certain advantages associated with PEM electrolysis and its relevan
