<p>Syftet med studien var att undersöka rederiernas syn på bränslecellen och framförallt försöka avgöra förutsättningarna för när bränslecellen kan få sitt genombrott till sjöss.</p><p>Datainsamlingen skedde med en internationellt distribuerad enkät i elektroniskt format. Urvalet bestämdes till att omfatta de fem största rederierna i de tjugo största flaggstaterna och även de fem största svenska rederierna.</p><p>Svarsfrekvensen blev tyvärr för låg för att möjliggöra några säkra slutsatser. Resultatet tyder ändå på att sjöfartsnäringen inte är beredda att betala mer för en bränslecell än för ett konventionellt system. Därför kommer ett genombrott troligen inte att ske utan ökade miljöavgifter, införsel av handel med utsläppsrätter eller drastiskt höjda bränslepriser.</p> / <p>The purpose with this thesis was to investigate the prospects of the fuel cell technology within the shipping industry and also to evaluate when the fuel cell could get a breakthrough in shipping.</p><p>The data was collected via an internationally distributed questionnaire. The selection of shipping companies for the survey consisted of the five largest shipping companies in the twenty largest maritime countries. The five largest Swedish shipping companies were also included.</p><p>The number of answers was unfortunately too low to be able to deduce any reliable conclusions. The results still indicate that shipping companies are not interested in paying more for a fuel cell than for a more conventional system. Because of this there will probably not be a breakthrough for the fuel cell, until there is an increase in environmental fees, a trade with emissions or drastically higher fuel prices.</p>

<p>The purpose of this paper is to identify the current status of fuel cell technology and to establish whether said technology is mature enough to be implemented into the Swedish Armed Forces. The question to be answered in this paper is as follows: Can hydrogen gas and fuel cells be used as an alternative source of energy within the Swedish Armed Forces?</p><p>This paper is based on theoretical studies and reports from prior research done on fuel cells. By studying these facts a predictive answer has been obtained. The answer I have come to, is that the maturity of fuel cell technology is currently inadequate for the Swedish Armed Forces to implement, especially considering its harsh working conditions.</p>

A numerical model of the steady state and alternating current behaviour of a solid-oxide fuel cell is presented to explore the possibilities to diagnose and identify degradation mechanisms in a minimally invasive way using impedance spectroscopy. This is the first report of an SOFC impedance model to incorporate degradation, as well as the first one to include the ribbed interconnect geometry, using a 2-D approximation. Simulated degradation modes include: electrode/electrolyte delamination, interconnect oxidation, interconnect/electrode interface detachment, and anode sulfur poisoning. Detailed electrode-level simulation replaces the traditional equivalent circuit approach, allowing the simulation of degradation mechanisms that alter the shape of the current path. The SOFC impedance results from calculating the cell response to a small oscillatory perturbation in potential. Starting from the general equations for mass and charge transport, and assuming isothermal and isobaric conditions, the system variables are decomposed into a steady-state component and a small perturbation around the operating point. On account of the small size of the imposed perturbation, the time dependence is eliminated, and the original equations are converted to a new linear, time independent, complex-valued system, which is very convenient from a numerical viewpoint. Geometrical and physical modifications of the model simulate the aforementioned degradation modes, causing variations in the impedance. The possibility to detect unique impedance signatures is discussed, along with a study of the impact of input parameter inaccuracies and parameter interaction on the presented results. Finally, a study of pairs of concurrent degradation modes reveals the method’s strengths and limitations in terms of its diagnosis capabilities.

Solid oxide fuel cells with graded electrodes consisting of multiple composite layers yield generally lower polarization resistances than single layer composite electrodes. Optimization of the performance of solid oxide fuel cells with graded electrode composition and/or microstructure requires an evaluation of both the three phase boundary length per unit volume and the effective diffusion coefficient in order to provide insight into how these properties vary over the design space. A numerical methodology for studying the three phase boundary length and effective diffusivity in composite electrode layers with controlled properties is developed. A three dimensional solid model of a sintered composite electrode is generated for which the mean particle diameter, composition, and total porosity may be specified as independent variables. The total three phase boundary length for the modeled electrode is calculated and tomographic methods are used to estimate the fraction of this length over which the electrochemical reactions can theoretically occur. Furthermore, the open porosity of the modeled electrode is identified and the effective diffusion coefficient is extracted from the solution of the concentration of the diffusing species within the open porosity. Selected example electrode models are used to illustrate the application of the methods developed, and the resulting connected three phase boundary length and diffusion coefficients are compared. A significant result is the need for thickness-specific effective diffusivity to be determined, rather than the general volume averaged property, for electrodes with porosity between the upper and lower percolation thresholds. As the demand for current increases, more of the connected three phase boundaries become active, and therefore a greater fraction of the electrode layer is utilized for a given geometry, resulting in a higher apparent effective diffusivity compared to the same electrode geometry operating at a lower current. The methods developed in this work may be used within a macroscopic electrode performance model to investigate optimal designs for solid oxide fuel cell electrodes with stepwise graded composition and/or microstructure.

The purpose of this paper is to identify the current status of fuel cell technology and to establish whether said technology is mature enough to be implemented into the Swedish Armed Forces. The question to be answered in this paper is as follows: Can hydrogen gas and fuel cells be used as an alternative source of energy within the Swedish Armed Forces? This paper is based on theoretical studies and reports from prior research done on fuel cells. By studying these facts a predictive answer has been obtained. The answer I have come to, is that the maturity of fuel cell technology is currently inadequate for the Swedish Armed Forces to implement, especially considering its harsh working conditions.

Syftet med studien var att undersöka rederiernas syn på bränslecellen och framförallt försöka avgöra förutsättningarna för när bränslecellen kan få sitt genombrott till sjöss. Datainsamlingen skedde med en internationellt distribuerad enkät i elektroniskt format. Urvalet bestämdes till att omfatta de fem största rederierna i de tjugo största flaggstaterna och även de fem största svenska rederierna. Svarsfrekvensen blev tyvärr för låg för att möjliggöra några säkra slutsatser. Resultatet tyder ändå på att sjöfartsnäringen inte är beredda att betala mer för en bränslecell än för ett konventionellt system. Därför kommer ett genombrott troligen inte att ske utan ökade miljöavgifter, införsel av handel med utsläppsrätter eller drastiskt höjda bränslepriser. / The purpose with this thesis was to investigate the prospects of the fuel cell technology within the shipping industry and also to evaluate when the fuel cell could get a breakthrough in shipping. The data was collected via an internationally distributed questionnaire. The selection of shipping companies for the survey consisted of the five largest shipping companies in the twenty largest maritime countries. The five largest Swedish shipping companies were also included. The number of answers was unfortunately too low to be able to deduce any reliable conclusions. The results still indicate that shipping companies are not interested in paying more for a fuel cell than for a more conventional system. Because of this there will probably not be a breakthrough for the fuel cell, until there is an increase in environmental fees, a trade with emissions or drastically higher fuel prices.

Metal alloy honeycomb structures were fabricated using a paste extrusion technique and characterized for potential application as interconnects in solid oxide fuel cells. Thermal expansion characteristics of Fe-Cr, Fe-Ni, Ni-Cr, Fe-Ni-Cr, and similar alloys containing an oxide dispersion were determined and compared with the thermal expansion behavior of yttria-stabilized zirconia (YSZ). A method was developed to calculate thermal expansion mismatch between two materials under a variety of heating and cooling conditions. It was shown that Fe 20 wt% Cr and Fe 47.5 wt% Ni alloys have low expansion mismatch with YSZ under a wide range of heating and cooling conditions. Oxidation experiments showed that Fe-Cr alloys have superior oxidation resistance in air at 700℃compared with Fe-Ni-Cr alloys with similar chromium contents. The inclusion of oxide dispersions (Y₂O₃ and CaO) into an alloy honeycomb was shown to improve oxidation resistance without affecting thermal expansion behavior. The honeycomb extrusion process provides a method by which experimental alloys can be produced and characterized rapidly to develop an alloy suitable for use as an interconnect in a solid oxide fuel cell.

An intermediate temperature solid oxide fuel cell (SOFC) is developed and its performance is investigated experimentally and theoretically. In the experimental program, a gadolinium doped ceria based membrane electrode group is developed with the tape casting and screen printing methodology and characterized. An experimental setup is devised for the performance measurement of SOFCs and the performance of produced cells is investigated over a range of parameters including the electrolyte thickness, the sintering temperature, the operation temperature etc. The experimental setup is then further modified to measure the temperature distribution in the large SOFC single cells. The effects of operating parameters on the temperature distribution are investigated and the parameter spaces leading high efficiency without cracking the ceramic membrane are identified. In theoretical study a mathematical model is developed to represent the fluid flow, the heat transfer, the species transport and the electrochemical reaction in intermediate temperature of solid oxide fuel cells.The differential equations are solved numerically with a commercial CFD code which employs a control volume based approach. The temperature distribution and species distribution during theSOFC operation is analyzed. The effects of operation parameters on critical SOFC characteristics and the performance are numerically investigated over a range of parameter space. The experimental and numerical results are compared to validate the mathematical model. The mathematical model is found to agree reasonable with experimental data.

Solid oxide fuel cells with graded electrodes consisting of multiple composite layers yield generally lower polarization resistances than single layer composite electrodes. Optimization of the performance of solid oxide fuel cells with graded electrode composition and/or microstructure requires an evaluation of both the three phase boundary length per unit volume and the effective diffusion coefficient in order to provide insight into how these properties vary over the design space. A numerical methodology for studying the three phase boundary length and effective diffusivity in composite electrode layers with controlled properties is developed. A three dimensional solid model of a sintered composite electrode is generated for which the mean particle diameter, composition, and total porosity may be specified as independent variables. The total three phase boundary length for the modeled electrode is calculated and tomographic methods are used to estimate the fraction of this length over which the electrochemical reactions can theoretically occur. Furthermore, the open porosity of the modeled electrode is identified and the effective diffusion coefficient is extracted from the solution of the concentration of the diffusing species within the open porosity. Selected example electrode models are used to illustrate the application of the methods developed, and the resulting connected three phase boundary length and diffusion coefficients are compared. A significant result is the need for thickness-specific effective diffusivity to be determined, rather than the general volume averaged property, for electrodes with porosity between the upper and lower percolation thresholds. As the demand for current increases, more of the connected three phase boundaries become active, and therefore a greater fraction of the electrode layer is utilized for a given geometry, resulting in a higher apparent effective diffusivity compared to the same electrode geometry operating at a lower current. The methods developed in this work may be used within a macroscopic electrode performance model to investigate optimal designs for solid oxide fuel cell electrodes with stepwise graded composition and/or microstructure.

A numerical model of the steady state and alternating current behaviour of a solid-oxide fuel cell is presented to explore the possibilities to diagnose and identify degradation mechanisms in a minimally invasive way using impedance spectroscopy. This is the first report of an SOFC impedance model to incorporate degradation, as well as the first one to include the ribbed interconnect geometry, using a 2-D approximation. Simulated degradation modes include: electrode/electrolyte delamination, interconnect oxidation, interconnect/electrode interface detachment, and anode sulfur poisoning. Detailed electrode-level simulation replaces the traditional equivalent circuit approach, allowing the simulation of degradation mechanisms that alter the shape of the current path. The SOFC impedance results from calculating the cell response to a small oscillatory perturbation in potential. Starting from the general equations for mass and charge transport, and assuming isothermal and isobaric conditions, the system variables are decomposed into a steady-state component and a small perturbation around the operating point. On account of the small size of the imposed perturbation, the time dependence is eliminated, and the original equations are converted to a new linear, time independent, complex-valued system, which is very convenient from a numerical viewpoint. Geometrical and physical modifications of the model simulate the aforementioned degradation modes, causing variations in the impedance. The possibility to detect unique impedance signatures is discussed, along with a study of the impact of input parameter inaccuracies and parameter interaction on the presented results. Finally, a study of pairs of concurrent degradation modes reveals the method’s strengths and limitations in terms of its diagnosis capabilities.