Fuel Cell Systems & Hydrogen

Graduate Student Master's Thesis 2009 The reports are not to be duplicated or printed without written consent by the author and RES. Formation of Lanthanum Zirconates in Solid Oxide Electrolysis Cells [PDF] Experimental Studies © Pedro Miguel da Costa Almeida (Fuel Cell Systems & Hydrogen Specialization) Abstract Versa Power Systems solid oxide cells were tested with the objective of performing long term electrolysis testing and studying their degradation and, more specifically, the creation of insulating phases of lanthanum zirconates. Three cells were tested but only one sustained long term electrolysis testing. The other two fractured due to excessive fuel flow and lack of heating in inlet tubes. A different sealing method and bubbler were used in the third tested cell. This cell showed good initial performance with power densities around 0.32 W/cm2 and with an ASR of 0.59 Ω.cm2 running on 175sccm H2 / 175sccm H20. The cell ran in electrolysis mode for 290 hours showing a steady degradation that eventually stabilized and even recovered in the last tens of hours. These are thought to be passivation and activation processes due to the silica based sealant (Hauch A. E., 2008). Scanning electron microscopy (SEM) and x-ray diffraction (XRD) measurements were performed after cell testing. They showed no significant microstructural changes and no presence of the insulating phase. A previous report on another VPS cell showed the possibility of the presence of this phase in an XRD test. Yet when a second XRD test was done these phases were not found. This might be explained if we consider that these phases form under the places where platinum paste is present, which conforms to the two different microstructural areas found in the SEM images in the previous tested cell. Hydrogen Fuel Cell Emergency Power System [PDF] Installation and Performance of Plug Power GenCore 5B48 Unit © Lech Birek & Stanisław Molitorys (Fuel Cell Systems & Hydrogen Specialization) Abstract Backup systems are crucial elements of modern electrical grids. They are used in places where an interruption in power supply can cause significant damage, e.g. in hospitals, banks or telecommunication towers. There are many solutions for how emergency power can be delivered. Hydrogen fuel cells are an emerging technology with great potential for the future. Fuel cells combine the advantages of batteries and diesel generators, and eliminate some of their significant disadvantages. They can work as long as they are supplied with fuel via a simple and efficient electrochemical reaction and at the same time they are quiet, produce no emissions and require minimum maintenance. The aim of this thesis is to present the idea of hydrogen fuel cells as reliable backup power systems. The work consisted of two parts: one practical, the other theoretical. The first part includes the background of energy security, emergency power sources, fuel cell systems backup power market, as well as an introduction to fuel cell technology, principles of operation and hydrogen safety. The practical part of this project is focused on the Plug Power GenCore 5B48 fuel cell backup power unit, its description, installation, operation, safety precautions and performance characteristics. The necessary hydrogen infrastructure was built according to safety codes and standards. The performance and reliability of the system was assessed. The system’s behavior was stable except for several minor problems during start-up which required intervention. The measured efficiency of the fuel cell stack and the whole system at the maximum available load of 1.65kW was 42.5% and 35.8% respectively. It was noted that the auxiliary load of the system has great influence on the overall performance of the system, especially at low output power. Noted fuel consumption was 13slm at 1kW and fuel utilization efficiency was estimated at around 99%. A cold start-up analysis was conducted and described based on the output data. During the first few minutes of operation the system required additional power to warm the fuel cell stack. The transition analysis focused on the ability of the system to provide power in case of a sudden outage. It was working well with batteries, as the fuel cell needed approximately 15 seconds to be ready to completely take over the power demand. Reliability and availability were assessed to be 96.8% and 79.9% respectively. It has to be pointed out that it was not possible to completely determine the system’s performance during some of the failure scenario and operation under different load because of the limitations of time and budget. Modeling of IGFC System [PDF] CO2 removal from gas streams, using membrane reactors © Raido Huberg, 2009 (Fuel Cell Systems & Hydrogen) Abstract In the following work, the different capture concepts of carbon dioxide from an IGFC power plant have been considered and analyzed. The main objective was to compare the net power output according to the different tail-gas processing concepts (oxy-combustion, H2- and O2-conducting membranes) and to compare the difference of output when CO2 is vented. The first concept considered is an IGFC plant (integrated gasification gas combined cycle plant with a fuel cell) with oxy-combustion for oxidizing the remaining fuel in the anode tail-gas. The second and third concepts are H2-conducting membranes, one with N2 and the other with air as sweep gas. The fourth concept involves an O2-conducting membrane in which O2 permeates from the cathode side to the anode side without mixing the two streams with each other. Also a fifth concept was developed, where the anode and cathode flows are mixed and no CO2 capture takes place. In the presented dissertation, a model with zero- and one-dimensional (membrane model) computational parts was created to simulate and evaluate the capability of the IGFC plant using different means to capture carbon dioxide. The efficiency and net power of the different tail-gas concepts were compared, assuming an IGFC plant with oxy-combustion for carbon dioxide capture as the baseline. The capture of carbon dioxide proved to have an efficiency and probably an investment cost penalty. A Carbon Tax (adopted in some countries like Sweden) proportional to the number of kilograms of carbon dioxide released in the environment is necessary to make the carbon dioxide capture economically feasible.   Considerations regarding modeling of MW-scale IG-SOFC Hybrid Power System [PDF] © Jakub Kupecki (Fuel Cell Systems & Hydrogen Specialization) Abstract The main objective of this thesis is to evaluate various modeling approaches for large systems employing high temperature fuel cell (particularly SOFC) modeling. It also includes a brief discussion of current trends and various designs. This thesis will review recently published papers investigating the hundred MWe scale SOFC hybrid Brayton-Rankine power systems. It goes into details discussing the crucial parameters influencing the cycle’s operation and performance. For better understanding, the basics of the fuel cell operation, involved processes and all phenonena are provided in Chapter 2. In the next chapter the SOFC based systems with integrated gasification reactors are widely described. Current state-of-the-art trends and their background are presented. Finaly the desired system configuration is proposed and investigated. These particular arragements correspond to the U.S. Department of Energy (DoE) baseline for systems employing high temperature fuel cells, hence certain design solutions are involved. The SOFC stack feedstock is provided by the gasification of coal, however different fuel can also be gasified (biomass for example). In the last chapter, the modeling and optimisation in the software are extensively described. Because of the fact that ASPEN Plus and Hysys are comonly used in the majority of cases when cycles involing high temperature fuel cells are analyzed, the attention will be focused on these two programs. Both of them have built-in tools allowing the modeling of heat exchangers, compressors and expanders (i.e. gas and steam turbines) by available units. ASPEN Plus is Fortran based software and the SOFC stack can be modeled as a user unit using this programming code. The modeling approach to the electrochemical and chemical processes within the SOFC stack will be delivered, since it is important for the modeling of the entire power cycle. Analysis of the whole system with the proposed tools allows the determination of the overall system thermal efficiency with high fidelity, thus the biggest effort must be made to correctly determine all input parameters and define the proper assumptions as well as simplifications. The final discussion emphasises the most crucial parameters. The proposed system represents a clean energy source, which substantialy reduces the polutants flow associated with the power generation. Desulphurisation and gases clean-up processes are also involved in the cycle, therefore it meets all environmental requirements. Solid Oxide Fuel Cell System Control [PDF] Modeling and Control Study of a Catalytic Partial Oxidation (CPOX) Reactor © Tomasz Szczęsny Miklis (Fuel Cell Systems & Hydrogen Specialization) Abstract An advanced thermodynamic model of a catalytic partial oxidation (CPOX) reactor was developed. The dynamics of the reactor were simulated using differential algebraic equations (DAEs). The aim of the project was to create a reliable and fast model that will be used, for control purposes, to maximize the hydrogen yield from the CPOX reaction. The composition of the output flow and species concentration is controlled by the input mass flows of fuel (Dodecane) and air. The state variables of the reactor considered in this model are temperature and total internal energy of the reactor. There are many options with which to customize the reactor model, from the geometry and materials used to build the reactor shell to different compositions of the gases fed to the reactor (fuel and air). The Cantera toolbox was used to simulate chemistry and the whole project was completed the in MATLAB programming environment. Renewable heat and electricity supply to residential settlements [PDF] Gas versus heat transport for low-energy housing © Tomasz Sasin (Fuel Cell System & Hydrogen Specializtion) Abstract The use of energy in the residential sector is among the most significant causes of global warming and greenhouse gas emissions. The majority of energy consumed in households accounts for space heating and the preparation of warm water. The key to decreasing energy consumption is increasing energy efficiency. The most progress in energy efficiency in the residential sector is expected to be made by improving the insulation of buildings and using low-energy equipment. However, in settlements with very high insulation standards, transport of heat becomes senseless as heat losses may be higher than delivered energy. The easiest way to eliminate losses in this case is generating heat directly at the consumer’s location. In the thesis seven ideas are proposed which eliminate heat transport and involve a switch to gas transport or direct electrical energy delivery. In the presented scenarios, all the energy delivered to the settlement comes from renewable energy sources. Four of the concepts were taken into further consideration and an energy efficiency analysis was performed for them. The thesis also presents an up-to-date overview of concepts regarding district heating, efficiency standards for buildings and statistics of renewable energy resources in Germany and the European Union. The main conclusion reached from this research is that energy distribution by electricity and gases is more efficient than heat distribution and with the use of distributed generation it is possible to completely avoid losses that are present in heat delivery. The biggest problem concerning switching to renewable energy sources is storage of energy during periods of lack of energy delivery from primary sources. In terms of energy efficiency and environmental impacts, the use of biogas reformed in solid oxide fuel cells seems to have the least environmental footprint. Setup of a test bench and testing the single solid oxide fuel cell at various temperatures [PDF] © Marek Skrzypkiewicz (Fuel Cell Systems & Hydrogen Specialization) Abstract Solid Oxide Fuel Cells (SOFCs) are a promising source of electricity. They are efficient devices that allow direct harnessing the Gibbs free energy of reactions between fuel and an oxidant. The ongoing project in the Fuel Cell laboratory in Perugia, Italy is a part of their coordination with the Energy Research Center of Netherlands (ECN). This project was devoted to single SOFCs testing, which helps in understanding the influence of different circumstances on the SOFC performance. In this thesis is a detailed outline of the testing procedures and an expanded discussion of the results. The main objectives of this work were to: finish building the single SOFC test bench, create a model that allowed time and gas consumption forecasting for different tests, design the sulphur tolerance system, create a model for cell temperature evaluation, study recent scientific achievements in SOFC with special emphasis on single cells testing, prepare the laboratory testing procedures, perform the tests of the ASC2 Cell by InDEC B.V. The results are presented in graphs in the body of the work and in detailed tables as an appendix. The measurements gave results worse than expected, but the temperature dependence is clear. The conclusions for future development of the test bench are that the temperature measuring should be improved and software development should continue. A wind-power fuel cell hybrid system study [PDF] Model of energy conversion for wind energy system with hydrogen storage © Katarzyna Sobotka (Fuel Cell Systems & Hydrogen Specialization) Abstract Hydrogen, as a form of long term storage for the excess energy from renewable sources, is a technically and economically viable option. However, the technology is not mature enough to compete with the other renewable energy possibilities. In this thesis, a study based on coupling a wind-turbine with a fuel cell to improve the utilization of wind power is presented. A part of the energy produced by the wind-turbine is stored in the form of hydrogen and is then delivered for consumption at variable power through a fuel cell. A model was developed to determine the key technical parameters influencing the operation of a wind energy system with hydrogen storage. The model incorporates the simulation results of a 600 kW wind energy system with a 100 kW Proton Exchange Membrane Fuel Cell (PEMFC) and an electrolyzer. Dynamic modeling of various components of this small isolated system is presented for the period from 1.1.2006 to 31.1.2006. In this way, the energy availability can be estimated and is presented for hybrid installations. The study presents the technology of the system for each particular element. This study is a general introduction for the wind energy system with hydrogen storage. Future studies should be more complex and detailed in order to understand and model the system with greater accuracy and to increase the possibility for the utilization of wind energy to generate hydrogen. This would enhance wind power competitiveness and sustain the continuously changing world energy demand.