The State of the Art in Fuel Cell Condition Monitoring and Maintenance

Fuel cell vehicles are considered to be a viable solution to problems such as carbon emissions and fuel shortages for road transport. Proton Exchange Membrane (PEM) Fuel Cells are mainly used in this purpose because they can run at low temperatures and have a simple structure. Yet to make this technology commercially viable, there are still many hurdles to overcome. Apart from the high cost of fuel cell systems, high maintenance costs and short lifecycle are two main issues need to be addressed. The main purpose of this paper is to review the issues affecting the reliability and lifespan of fuel cells and present the state of the art in fuel cell condition monitoring and maintenance. The Structure of PEM fuel cell is introduced and examples of its application in a variety of applications are presented. The fault modes including membrane flooding/drying, fuel/gas starvation, physical defects of membrane, and catalyst poisoning are listed and assessed for their impact. Then the relationship between causes, faults, symptoms and long term implications of fault conditions are summarized. Finally the state of the art in PEM fuel cell condition monitoring and maintenance is reviewed and conclusions are drawn regarding suggested maintenance strategies and the optimal structure for an integrated, cost effective condition monitoring and maintenance management system

Roadmap on semiconductor-cell biointerfaces.

This roadmap outlines the role semiconductor-based materials play in understanding the complex biophysical dynamics at multiple length scales, as well as the design and implementation of next-generation electronic, optoelectronic, and mechanical devices for biointerfaces. The roadmap emphasizes the advantages of semiconductor building blocks in interfacing, monitoring, and manipulating the activity of biological components, and discusses the possibility of using active semiconductor-cell interfaces for discovering new signaling processes in the biological world

Enhancing fuel cell lifetime performance through effective health management

Hydrogen fuel cells, and notably the polymer electrolyte fuel cell (PEFC), present an important opportunity to reduce greenhouse gas emissions within a range of sectors of society, particularly for transportation and portable products. Despite several decades of research and development, there exist three main hurdles to full commercialisation; namely infrastructure, costs, and durability. This thesis considers the latter of these. The lifetime target for an automotive fuel cell power plant is to survive 5000 hours of usage before significant performance loss; current demonstration projects have only accomplished half of this target, often due to PEFC stack component degradation. Health management techniques have been identified as an opportunity to overcome the durability limitations. By monitoring the PEFC for faulty operation, it is hoped that control actions can be made to restore or maintain performance, and achieve the desired lifetime durability. This thesis presents fault detection and diagnosis approaches with the goal of isolating a range of component degradation modes from within the PEFC construction. Fault detection is achieved through residual analysis against an electrochemical model of healthy stack condition. An expert knowledge-based diagnostic approach is developed for fault isolation. This analysis is enabled through fuzzy logic calculations, which allows for computational reasoning against linguistic terminology and expert understanding of degradation phenomena. An experimental test bench has been utilised to test the health management processes, and demonstrate functionality. Through different steady-state and dynamic loading conditions, including a simulation of automotive application, diagnosis results can be observed for PEFC degradation cases. This research contributes to the areas of reliability analysis and health management of PEFC fuel cells. Established PEFC models have been updated to represent more accurately an application PEFC. The fuzzy logic knowledge-based diagnostic is the greatest novel contribution, with no examples of this application in the literature

The development and fabrication of miniaturized direct methanol fuel cells and thin-film lithium ion battery hybrid system for portable applications

In this work, a hybrid power module comprising of a direct methanol fuel cell (DMFC) and a Li-ion battery has been proposed for low power applications. The challenges associated with low power and small DMFCs were investigated and the performance of commercial Li-ion batteries was evaluated. At low current demand (or low power), methanol leakage through the proton exchange membrane (PEM) reduces the efficiency of a DMFC. Consequently, a proton conducting methanol barrier layer made from phospho-silica glass(PSG) was developed. At optimized deposition conditions, the PSG layers had low methanol permeability and moderate conductivity. The accumulation of CO2 inside the fuel tank was addressed by fabricating CO2 vents. Poly (dimethyl siloxane) (PDMS) and poly (1-trimethyl silyl propyne) (PTMSP) base polymers were used as the backbone material for these vents. The selectivity of CO2 transport through the vent was further enhanced by using additives like 1, 6-divinylperfluorohexane. Finally, the effects of self-discharge and voltage loss were evaluated for Panasonic coin cells and thin film LiPON cells. It was observed that the thin film battery outperformed the others in terms of low energy loss. Nonetheless, the performance of small Panasonic coin cells with vanadium oxide cathode was comparable at low discharge rates of less than 0.01% depth of discharge. Lastly, it was also observed that the batteries have stable cycles at low discharge rates.Ph.D.Committee Chair: Kohl, Paul; Committee Member: Fuller, Tom; Committee Member: Gray, Gary; Committee Member: Liu, Meilin; Committee Member: Meredith, Carson; Committee Member: Rincon-Mora, Gabrie

Thermal Analysis For The Purpose Of Fault Diagnosis of Commercial Proton Exchange Membrane Fuel Cells (PEMFC)

The world\u27s awareness towards the amount of destruction that our extensive and ignorant lifestyles in the past few decades have imposed on the environment is growing day after day. This resulted in an increased governmental and research interest towards the development and use of green technology. Fuel Cells are one of the green technologies that received a major share of research interest in the past decade. However, despite their promising features, Fuel Cell systems still lack a solid fault diagnosis and predictive maintenance study. There are numerous faults that have to be detected and diagnosed on a fuel cell power generator system, ranging from chemical faults, to electrical and power electronics faults such as: reactant leakages inside the Fuel Cell, Fuel Cell flooding and membrane drying out, membrane humidification and reactive gas feeding, the accumulation of nitrogen and/or water in the anode compartment, etc. The aim of this dissertation work is to develop and implement a model based fault diagnostic scheme for a commercial Proton Exchange Membrane Fuel Cell (PEMFC) system in order to improve its safety and reliability; despite the lack of important system information. To achieve this aim, a diagnosis-oriented model of a fuel cell power generator is developed and validated using actual experimental data. Genetic Algorithms (GA) and Particle Swarm Optimization (PSO) were both utilized in the parameter identification of two commercial PEMFC systems\u27 models. GA and PSO were used to extract the correct parameter values of the fuel cell system to minimize differences between experimental and simulated results. Furthermore, PSO was found to outperform GA in the identification process. The effect of severe environmental conditions of hot climate countries such as the UAE on a commercial PEMFC system is then studied and analyzed in simulation using MATLAB/SIMULINK through the developed dynamic system model. The thermal analysis results suggested that the fuel cell system under study would fail to start properly at ambient temperatures of 40°C and higher. Moreover, the faults that may affect the PEM fuel cell system are listed and their severity is analyzed. In a next step, a more comprehensive system model is developed and validated in LMS AMESim software using actual experimental data, and an appropriate fault diagnostic technique using residual generation is developed, tested and validated in LMS AMESim in order to detect and identify five potential abrupt faults, namely: drying of the membrane, flooding of the membrane, air leakage, hydrogen leakage in the supply manifold and cooling system failure. The use of LMS AMESim in the proposed modeling and fault diagnosis approach of this dissertation makes it possible to develop a fault diagnosis oriented model for any commercial PEMFC system despite the lack of crucial system information that are usually considered essential for modeling PEMFCs

PVDF as a Biocompatible Substrate for Microfluidic Fuel Cells

A reliable, flexible, and biocompatible power source for implantable and wearable devices has always been one of the biggest challenges for medical device design engineers. Microfluidic fuel cells (MFCs) are one of the candidates to generate a constant and reliable energy. However, the aspects of this approach, such as use of expensive materials, limitation of achievable power density and biocompatibility, have not yet been fully addressed. These challenges have restricted the application of MFCs to lab-on-chip systems that are deemed to be promising for implantable medical devices. Recently, porous materials such as natural papers and synthetic polymers (in the form of either nanofibers or porous membranes), when used as the MFC substrate, have shown that they can address the above-mentioned challenges. More importantly, these porous materials induce an inherent capillary flow in the fuel, eliminating the need of a pump. This may lead to an increased fuel efficiency and miniaturization of MFCs. However, the search for a porous biomaterial that displays high mechanical strength but remains flexible without degrading in a biological environment is not straightforward. In this research, Polyvinylidene Fluoride (PVDF), a non-biodegradable, biocompatible, flexible, and inexpensive material, was investigated for the first time as a channel substrate in a dynamic state MFC. To achieve the desired porosity, flexibility, and material strength of the substrate, PVDF nanofibers were fabricated using the electrospinning technique. Furthermore, hydrophilic PVDF nanofibers were successfully achieved by oxygen plasma surface treatment. The desired PVDF-based MFC was conceptualized using Axiomatic Design Theory (ADT) and FCBPSS (F: function, C: context, B: behavior, P: principle, SS: structure-state) methods. To investigate the electrochemical output of the designed PVDF-based MFC, a hydrophilic porous PVDF membrane was used as the substrate to induce a capillary action in the fuel (hydrogen peroxide). The PVDF-based MFC studied here successfully produced a power density of 0.158 mW/cm^2 at 0.08 V that is ~60% higher compared to the previous dynamic state paper-based biofuel cell reported in the literature. Moreover, the power density of MFC studied here is comparable to previous studies of static state single compartment MFCs using the same fuel type and concentration. Therefore, the results from this work demonstrate, for the first time, that the porous PVDF is a suitable material for the channel substrate in a dynamic state MFC. The potential application of this cell, in medicine, is utilizing the hydrophilic porous PVDF in electrochemical, implantable, and wearable medical devices. This approach can also be applied to any self-powered point-of-care diagnostic system

A Preventive Medicine Framework for Wearable Abiotic Glucose Detection System

In this work, we present a novel abiotic glucose fuel cell with battery-less remote access. In the presence of a glucose analyte, we characterized the power generation and biosensing capabilities. This system is developed on a flexible substrate in bacterial nanocellulose with gold nanoparticles used as a conductive ink for piezoelectric deposition based printing. The abiotic glucose fuel cell is constructed using colloidal platinum on gold (Au-co-Pt) and a composite of silver oxide nanoparticles and carbon nanotubes as the anodic and cathodic materials. At a concentration of 20 mM glucose, the glucose fuel cell produced a maximum open circuit voltage of 0.57 V and supplied a maximum short circuit current density of 0.581 mA/cm2 with a peak power density of 0.087 mW/cm2 . The system was characterized by testing its performance using electrochemical techniques like linear sweep voltammetry, cyclic voltammetry, chronoamperometry in the presence of various glucose level at the physiological temperatures. An open circuit voltage (Voc) of 0.43 V, short circuit current density (Isc) of 0.405 mA/cm2 , and maximum power density (Pmax) of 0.055 mW/cm2 at 0.23 V were achieved in the presence of 5 mM physiologic glucose. The results indicate that glucose fuel cells can be employed for the development of a self-powered glucose sensor. The glucose monitoring device demonstrated sensitivity of 1.87 uA/mMcm2 and a linear dynamic range of 1 mM to 45 mM with a correlation coefficient of 0.989 when utilized as a self-powered glucose sensor. For wireless communication, the incoming voltage from the abiotic fuel cell was fed to a low power microcontroller that enables battery less communication using NFC technology. The voltage translates to the NFC module as the digital signals, which are displayed on a custom-built android application. The digital signals are converted to respective glucose concentration using a correlation algorithm that allows data to be processed and recorded for further analysis. The android application is designed to record the time, date stamp, and other independent features (e.g. age, height, weight) with the glucose measurement to allow the end-user to keep track of their glucose levels regularly. Analytics based on in-vitro testing were conducted to build a machine learning model that enables future glucose prediction for 15, 30 or 60 minutes

Sustainable Transportation Program 2011 Annual Report

Highlights of selected research and development efforts at Oak Ridge National Laboratory funded by the Vehicle Technologies Program, Biomass Program, and Hydrogen and Fuel Cells Program of the Department of Energy, Office of Energy Efficiency and Renewable Energy; and the Department of Transportation

Sensing water accumulation and transport in proton exchange membrane fuel cells with terahertz radiation

Fuel cells are like batteries in the sense that they are electrochemical cells whose main components are two electrodes (anode and cathode) and an electrolyte material. They differ from most batteries as they require a continuous stream of fuel and oxidant, generating electricity and heat for as long as these are supplied. Perfluorinated sulfonic-acid ionomers such as Nafion are the most common proton exchange membrane material (solid electrolyte) whose structure underpins its unique water and chemical/mechanical stability properties. Pure hydrogen and air are typically used as the fuel and oxidant, respectively, and by-products are water and waste heat. Due to their high efficiency, low temperature operation and capacity to quickly vary their output to meet shifting demands, these fuel cells are attractive to the automobile industry, although they can also be used for stationary power production. Water management is a prominent issue in proton exchange membrane fuel cell technology. Strategies in this topic must maintain a delicate balance between adequate hydration levels in the Nafion proton electrolyte membrane to maximise proton conductivity, and minimal flooding, which hinders mass transport to active sites. The complex nature of water transport in these fuel cells can be investigated via in situ or ex situ diagnostics with visualisation techniques such as neutron imaging or optical diagnostics. Despite the wealth of information provided by these techniques, they suffer from issues such as limited availability, excessive cost, limited sensitivity, and penetration depth. Terahertz radiation has been growing in popularity for contactless and non-destructive testing across various industrial sectors, including pharmaceutical coating analysis, defect identification, and gas pipeline monitoring. The ability of terahertz waves to penetrate through dielectric materials such as plastics or ceramics combined with strong attenuation by liquid water provides the necessary contrast to image water presence in proton exchange membrane fuel cells and their components. Motivated by the recent commercial availability of a compact terahertz source and video-rate terahertz camera, a simple terahertz imaging system in transmission geometry was realised. First, as a first step towards flooding inspection in an operating fuel cell, the feasibility of the imaging system for visualising and quantifying liquid water during an ambient air desorption process for Nafion membranes of a wide range of thicknesses – NRE-212 (50 µm), N-115 (127µm), N-117 (180 µm) and N-1110 (254 µm) was investigated. It was demonstrated that the imaging system was able to quantify liquid water in the 25-500 µm thickness range, estimate membrane weight change related to liquid water desorption, which correlated well against simultaneous gravimetric analysis and visualise the room temperature liquid water desorption process of a partially hydrated Nafion N-117 membrane. Further work consisted in imaging water build-up inside an operating proton exchange membrane fuel cell using the terahertz imaging system, combined with high-resolution optical imaging. Using a custom-built, laboratory-scale, terahertz, and optically transparent fuel cell, two-phase flow phenomena of water accumulation and transport, such as membrane hydration, main droplet occurrence, water pool formation, growth, and eventual flush out by gases were imaged. Results of the terahertz agree with simultaneous optical imaging and electrochemical readings. To demonstrate the potential used of the proposed imaging modality, the effect of air gas flow rates on flooding was demonstrated