An experimental and modelling approach to study the performance and degradation of low temperature electrolyzers

L'abstract è presente nell'allegato / the abstract is in the attachmen

Selected Papers from the 9th World Congress on Industrial Process Tomography

Industrial process tomography (IPT) is becoming an important tool for Industry 4.0. It consists of multidimensional sensor technologies and methods that aim to provide unparalleled internal information on industrial processes used in many sectors. This book showcases a selection of papers at the forefront of the latest developments in such technologies

Electrochemical Safety Studies of Cochlear Implant Electrodes Using the Finite Element Method

Cochlear implants, amongst other neural prostheses, utilise platinum electrodes as an interface between the synthetic implant and the biological tissue environment. If excessive electrical charge is injected via these electrodes, injury to the tissue may result. Empirically derived stimulation limits have been defined to prevent tissue damage, however the injurious mechanisms are still unclear. Evidence suggests that the non-uniform distribution of charge on electrodes influences the electrochemical generation of toxic by-products. However, in vivo and in vitro techniques are limited in their ability to systematically explore the factors and mechanisms that contribute to stimulation-induced tissue injury. To this end, an in silico approach was used to develop a time-domain model of cochlear implant stimulation electrodes. A constant phase angle impedance was used to model the reversible processes on the electrode surface, and Butler-Volmer reaction kinetics were used to define the behaviour of the water window irreversible electrochemical reactions. The resulting model provided time-domain responses of the current density distributions, and net charge consumed by the hydrolysis reactions. This model was then used to perform systematic evaluations of various electrode geometries and stimulation parameters. The modelling results showed the current associated with irreversible reactions was non-uniform and tended towards the periphery of the electrode. A comparison of electrode geometries revealed interactions between electrode size, shape and recess depth. Stimulation mode, electrode position, and electrolyte conductivity were found to impact the shape of the electric field and the extent of irreversible reactions. This emphasised the influence of the physiological environment on the stimulation safety. In vitro experiments were conducted to validate the model. The implications of the results described in this thesis can be used to inform the design of safer electrodes

Protonics of perovskite electrocatalysts for energy conversion and storage systems

Department of Energy EngineeringWith the exponential growth in energy consumption and with finite fossil fuel resources, environmentally-friendly and sustainable energy conversion and storage (ECS) devices have received great attention from the industrial and academic communities. Ceramic electrochemical cells such as solid oxide fuel cells(SOFCs) and solid oxide electrolysis cells (SOECs), are considered as promising ECS applications because of their high-energy conversion efficiency and low pollutant emission. Solid oxide fuel cells are high-efficiency energy generation devices that convert chemical energy directly into electricity. As a reverse reaction of the fuel cell reaction, the SOEC is a device capable of producing hydrogen without any pollutants by water electrolysis. Despite these advantages, there are many problems due to the high activation energy of oxygen ion transfer, which requires a very high operating temperature. (e.g., degradation of performance, costly insulation, harsh thermos-cycle environment, slow start-up) In recent years, protonic ceramic fuel cells (PCFC) using a proton conducting oxide (PCO) as an electrolyte, have been attracting attention to solve the drawbacks of high-temperature operation because the PCOs have shown high ionic conductivity and low activation energy of the H+ transport compared with the O2- transport. To operate the PCFC efficiently, the PCFC cathode materials should have the property of electrochemical activity not only for O2- and e??? but also for H+ (so-called triple conducting oxide, TCO). However, due to the difficulties of its characterization, the proton properties of the TCOs are not fully understood yet. In this regard, the characterization of protonics in the TCO is important to understanding applications based on proton conducting oxides. This paper mainly focuses on the understanding and development of perovskite catalysts for ceramic electrochemical cells. In particular, to solve the problems mentioned above, I have comprehensively investigated the thermodynamic and kinetic properties of the oxygen ion, electron, and proton in the perovskite materials. I started with basic principles and theory of overall PCFCs and solid oxide ceramic cell in chapter 1, and then my research papers studying solid oxide fuel cell cathode material and protonic ceramic fuel cell for intermediate to low temperature ceramic fuel cells are presented as follows, 1. Effect of Fe Doping on Layered GdBa0.5Sr0.5Co2O5+?? Perovskite Cathodes for Intermediate Temperature Solid Oxide Fuel Cells 2. Chemically Stable Perovskites as Cathode Materials for Solid Oxide Fuel Cells: La-Doped Ba0.5Sr0.5Co0.8Fe0.2O3-?? 3. Triple-Conducting Layered Perovskites as Cathode Materials for Proton-Conducting Solid Oxide Fuel Cells 4. Hybrid-solid oxide electrolysis cell: A new strategy for efficient hydrogen production 5. The First Observation of Proton Trace in Triple Conducting Oxides: Thermodynamics and Kinetics of Protonope

An adaptive Cartesian embedded boundary approach for fluid simulations of two- and three-dimensional low temperature plasma filaments in complex geometries

We review a scalable two- and three-dimensional computer code for low-temperature plasma simulations in multi-material complex geometries. Our approach is based on embedded boundary (EB) finite volume discretizations of the minimal fluid-plasma model on adaptive Cartesian grids, extended to also account for charging of insulating surfaces. We discuss the spatial and temporal discretization methods, and show that the resulting overall method is second order convergent, monotone, and conservative (for smooth solutions). Weak scalability with parallel efficiencies over 70\% are demonstrated up to 8192 cores and more than one billion cells. We then demonstrate the use of adaptive mesh refinement in multiple two- and three-dimensional simulation examples at modest cores counts. The examples include two-dimensional simulations of surface streamers along insulators with surface roughness; fully three-dimensional simulations of filaments in experimentally realizable pin-plane geometries, and three-dimensional simulations of positive plasma discharges in multi-material complex geometries. The largest computational example uses up to $800$ million mesh cells with billions of unknowns on $4096$ computing cores. Our use of computer-aided design (CAD) and constructive solid geometry (CSG) combined with capabilities for parallel computing offers possibilities for performing three-dimensional transient plasma-fluid simulations, also in multi-material complex geometries at moderate pressures and comparatively large scale.Comment: 40 pages, 21 figure

Analysing and evaluating a thermal management solution via heat pipes for lithium-ion batteries in electric vehicles

Thermal management is crucial in many engineering applications because it affects the electrical, material, and other properties of the system. A recent study focuses on the use of heat pipes for battery thermal management in electric vehicles, which explores a new area for heat pipe applications. The battery, as one and only energy source in an EV, establishes a vital barrier for automotive industry because it can make the car more expensive and less reliable. The modelling methodology developed in this thesis is a one-dimensional electrochemical model, decoupled and coupled with a three-dimensional flow and heat transfer model. A prototype for 2-cell prismatic battery cooling and preheating using heat pipes is developed, and a full experimental characterisation has been performed. The experimental results characterised system thermal performance as well as validating material properties/parameters for simulation inputs. Two surrogate cells filled with atonal 324 were used in this experiment. The eligibility of substituting atonal 324 for lithium-ion battery electrolytes has been assessed and confirmed. The consistency demonstrated between the finite element analysis and the experiment facilitates BTM simulation at pack level, which is a scale-up model containing 30 lithium-ion batteries. The study shows that heat pipes can be very beneficial to reduce thermal stress on batteries leading to thermally homogenous packs. Additionally, an attempt of integrating biomimetic wicks for ultra-thin flat plate heat pipes is made in response to space limitations in microelectronics cooling. To date, no one has devised an ultra-thin FPHP with enough vapour space by constructing different wicks for each heat pipe segment, especially under anti-gravity condition. It is thus interesting to see whether a new type of wick structure can be made to achieve an optimum heat transfer potential

Surface Modification and Metal Printing Using Atmospheric Pressure Plasma

Non-thermal atmospheric plasma sources are at the centre of a growing new field of research that promises significant benefits in areas ranging from catalysis to medicine. The main value of atmospheric pressure sources lie in their ability to generate highly energetic and reactive species under near-ambient conditions. This characteristic makes atmospheric plasma an appealing alternative to well-established vacuum plasma processes. In this study, radio frequency atmospheric pressure plasma sources are used for modification of metal oxide surfaces and direct metal deposition. In atmospheric pressure plasma afterglow, plasma electrons are shown to be capable of reducing Cu2O films, this is proven by applying an external electric field to collect or to retard plasma electrons and observing the evolution of the oxide film. Using a micro-plasma jet, Cu2O and SnO2 are demonstrated to be completely reduced to their parent metals when exposed to helium plasma. A reducing plasma is required to induce partial reduction in TiO2, WO3 and ZnO, generating oxygen deficiencies. Oxygen deficient TiO2, also known as black titania is a well-known defective metal oxide photocatalyst. In this work, a facile method for producing black titania is developed using reducing plasma jets. This method improves photocatalyic efficiencies of nano-porous anatase up to sixfold while dispensing the need for vacuum or high pressure equipment. Deposition of conductive metals is a topic of ongoing research, with an aim to develop techniques and precursors that can enable printing of electrical circuits onto unconventional substrates. In this work, a novel technique for metal printing using plasma jets is developed. The method developed in this work enables single-step deposition of conductors from lowcost metal salt based precursors. Using aerosolized CuSO4 in the plasma jet stream, it is shown that metallic traces can be deposited on a large variety surfaces with fine spatial control