Three-Dimensional Modelling of a Microtubular SOFC: A Multiphysics Approach

Microtubular Solid Oxide Fuel Cells (µ-SOFC) are suited to a broad spectrum of applications with power demands ranging from a few watts to several hundred watts. µ-SOFC’s possess inherently favourable characteristics over alternate configurations such as high thermo-mechanical stability, high volumetric power density and rapid start-up times. Computational modelling at the design level minimises cost and maximises productivity, giving critical insight into complex SOFC phenomena and their interrelationships. To date, models have been limited by oversimplified geometries, often failing to account for oxidant supply complexities, gas distribution within pores and radiative heating effects (1-3). Here, a three-dimensional Computational Fluid Dynamics (CFD) model of electrodes, electrolyte, current collectors and furnace is considered using COMSOL Multiphysics. The distribution of temperature, current density, electrical potential, pressure and gas concentrations throughout the cell are simulated. Results show good correlation with experimental data and the model is reliable for prediction of fuel cell performance within set parameters

Types of hydrogen use in transportation and hydrogen refuelling stations

Hydrogen has immense potential as an energy vector. Once produced and stored the energy contained can be exploited in energy generation. This exploitation is thought to be able to rival more traditional methods of energy generation such as coal and gas powered power stations. Typically, hydrogen is expected to be deployed in fuel cells; however, there exist options in combusting the hydrogen to release the stored energy. Early markets and economic demand will force the first steps of hydrogen technology. At present road vehicles are seen as the technology of choice, with early adopters keen to take up this technology as the authors move forward to a low carbon future. Parallel to this is the need to have such an infrastructure to support deployment. In this article, they look at a few of the key areas where hydrogen is in transportation and discuss the infrastructure that is required to support the technology.Published versio

Production methods of stacks and hydrogen with associated costs

There are currently approximately 50 million tonnes of hydrogen produced annually. This figure is expected to rise over the coming decades with the growth of a hydrogen economy. Hydrogen is currently and predominately used in industry to produce ammonia, hydrogenation of fats and pharmaceutical manufacture. All of these industries will continue to use hydrogen gas, so there will be an increased demand on the volume of hydrogen produced each year if the hydrogen economy is to succeed as an alternative form of energy. Consequently, hydrogen would need to be sourced from more than a single production pathway, and yet be sustainable. Each production pathway has unique benefits and disadvantages, such as cost of production and the purity of hydrogen produced. As a result, new sustainable methods of producing hydrogen are being researched for optimisation and commercialisation. In this article, the authors examine traditional and new routes to production techniques and costs that are associated with them.Published versio

Cost-effective design of the alkaline electrolyser for enhanced electrochemical performance and reduced electrode degradation

An alkaline electrolyser was developed and characterized. Three different metals, working as the electrode, were analysed using electrochemical methods to determine the best electrochemical performance. The performance of the Stainless Steel (SS316) electrode and the nickel electrode is much better than that of the conventional iron electrode. Degradation analysis of the electrode materials highlighted the need for the material to be durable and resistant to corrosion from an alkaline environment. Through SEM and mass analysis, it is shown that Nickel exhibits the strongest long-term resistance to surface and electrochemical performance degradation, when compared with Mild Steel (Iron) and SS316

Performance measurement of the upgraded Microcab-H4 with academic drive cycle

The original Microcab-H4, a hybrid fuel cell car, was tested with Academic drive cycle. After several years, the car was upgraded and tested with the ECE 15 drive cycle. The result showed the car has higher energy efficiency. However, the result could not be compared to the original car due to different drive cycle test. This research was done to measure the performance and energy efficiency of the Upgraded Microcab-H4 with Academic drive cycle. The measure of car energy efficiency was done through four tests: Run on battery, run on battery and Ballard fuel cell, and run on battery, Ballard, and Horizon fuel cell. The energy efficiency was calculated based on the hydrogen consumption after 5 cycles. The lowest energy efficiency was run on battery and Ballard fuel cell with (1.01 km/MJ). The highest energy efficiency was run on battery, Ballard, and Horizon fuel cells (1.10 km/MJ), which is higher than previous tests

Feasibility of an oxygen-getter with nickel electrodes in alkaline electrolysers

Alkaline electrolysis is the long-established technology for water splitting to produce hydrogen and has been industrially used since the nineteenth century. The most common materials used for the electrodes are nickel and derivatives of nickel (e.g. Raney nickel). Nickel represents a cost-effective electrode material due to its low cost (compared to platinum group metals), good electrical conductivity and exhibits good resistance to corrosive solutions. The steady degradation of the nickel electrodes over time is known as a result of oxide layer formation on the electrode surface. Reducing oxide layer growth on the electrode surface will increase the efficiency and lifetime of the electrolyser. Titanium has a higher affinity to oxygen than nickel so has been introduced to the electrolyser as a sacrificial metal to reduce oxide layer formation on the nickel. Two identical electrolysers were tested with one difference: Cell B had titanium chips present in the electrolyte solution, whilst Cell A did not have titanium present. SEM results show a reduction of 16 % in the thickness of the Cell B oxide layer on nickel compared to the Cell A nickel, which is supported by the large increase in oxide layer build-up on the titanium in Cell B. EDX on the same samples showed on average a 59 % decrease in oxygen on the Cell B nickel compared to Cell A. XPS surface analysis of the same samples showed a 17 % decrease in the oxygen on Cell B nickel. These results support the hypothesis that adding titanium to an alkaline electrolyser system with nickel electrodes can reduce the oxide layer formation on the nickel

Internal current collection in microtubular SOFCs: Minimisation of contact resistance via brazing and plating

Paper presented at the Sixteenth International Symposium on Solid Oxide Fuel Cells (SOFC-XVI), held in Kyoto, Japan, September 8–13, 2019.Microtubular Solid Oxide Fuel Cells (µ-SOFC) are aptly suited for powering devices with demands ranging from the order of mW to few kW. The rapid start-up time, high thermo-mechanical stability, and excellent power density by volume lend them favour over alternate configurations, particularly for portable applications (1). Interconnecting the micro-tubes, though, is a persistent issue and minimisation of conduction pathway lengths and their contribution to stack ohmic resistance is a key parameter for maximising overall performance from a tubular cell stack (2). Contacting of each electrode is most simply and typically achieved from the cell exterior at the expense of available active electrode area. Exposing the cell support, interior electrode (anode or cathode, depending on cell configuration) from the exterior can lead to fuel crossover, decreasing fuel utilisation and giving rise to accelerated degradation from local thermal ‘hot spots’ as a result of hydrogen combustion (3). In this paper a novel method of internal current collection is proposed to collect current from multiple points along the inner wall of an anode-supported tubular cell. The current collector will also act as a flow turbuliser, enhancing the flow and reducing thermal gradients within the fuel cell. Ensuring an intimate contact of the many current collection nodes to the anode and hence minimisation of contact resistance is achieved by use of brazing, depositing braze material via electroless plating. Interconnection proficiency has been studied using electrochemical performance testing, impedance spectroscopy, optical microscopy and mechanical testing.Published versio

The development of current collection in micro-tubular solid oxide fuel cells—a review

© 2021 The Authors. Published by MDPI. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.3390/app11031077Micro-tubular solid oxide fuel cells (µT-SOFCs) are suited to a broad range of applications with power demands ranging from a few watts to several hundred watts. µT-SOFCs possess inherently favourable characteristics over alternate configurations such as high thermo-mechanical stability, high volumetric power density and rapid start-up times, lending them particular value for use in portable applications. Efficient current collection and interconnection constitute a bottleneck in the progression of the technology. The development of current collector designs and configuration reported in the literature since the inception of the technology are the focus of this study.This research was funded by the EPSRC, grant number EP/L015749/1, through the CDT in Fuel Cells and their Fuels, led by the University of Birmingham.Published onlin

Design for On-Site Hydrogen Production for Hydrogen Fuel Cell Vehicle Refueling Station at University of Birmingham, U.K.

In April 2008, the University of Birmingham launched the first permanent Hydrogen Refuelling Station in the UK. This enabled the refuelling of the only at the time fleet of Hydrogen Hybrid Fuel Cell Vehicles (HHFCV) in the UK. To maintain the low emissions ethos, the ultra-high purity “Green” hydrogen for the refuelling station was supplied off site, from a third party contractor. The University aims to be the first campus in the UK that is carbon neutral and this project scopes to produce “Green” hydrogen on-site to power the fleet of HHFCVs. Electrolysis is currently the only commercial method for producing ultra-high purity hydrogen without the need for, what could prove to be very costly, additional purification steps. Working in collaboration with ITM Power, a HPac Model electrolyser has been installed to produce electrolytic hydrogen on-site (up to 1.25 kgH2/day). The HPac uses PEM technology, which eliminates the need for hazardous alkaline substances, to produce hydrogen. The input requirements are ASTM Type 2 de-ionised (DI), water and 240 V power supply. Hydrogen is produced at pressures up to 15 bar [1]. However, there is a need to incorporate this unit within the existing hydrogen infrastructure incorporating 350 bar Air Product refuelling station. An integrated delivery system has been designed and initial results are presented herein

High temperature (HT) polymer electrolyte membrande fuel cells (PEMFC) - A review

One possible solution of combating issues posed by climate change is the use of the High Temperature (HT) Polymer Electrolyte Membrane (PEM) Fuel Cell (FC) in some applications. The typical HT-PEMFC operating temperatures are in the range of 100e200 o C which allows for co-generation of heat and power, high tolerance to fuel impurities and simpler system design. This paper reviews the current literature concerning the HT-PEMFC, ranging from cell materials to stack and stack testing. Only acid doped PBI membranes meet the US DOE (Department of Energy) targets for high temperature membranes operating under no humidification on both anode and cathode sides (barring the durability). This eliminates the stringent requirement for humidity however, they have many potential drawbacks including increased degradation, leaching of acid and incompatibility with current state-of-the-art fuel cell materials. In this type of fuel cell, the choice of membrane material determines the other fuel cell component material composition, for example when using an acid doped system, the flow field plate material must be carefully selected to take into account the advanced degradation. Novel research is required in all aspects of the fuel cell components in order to ensure that they meet stringent durability requirements for mobile applications.Web of Scienc