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Shaffer, Christian Edward. "Flow system modeling with applications to fuel cell systems." Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4198.
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Thesis (M.S.)--West Virginia University, 2005.Title from document title page. Document formatted into pages; contains xii, 111 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 100-102).
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Bradley, Thomas Heenan. "Modeling, design and energy management of fuel cell systems for aircraft." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26592.
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Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Parekh, David; Committee Member: Fuller, Thomas; Committee Member: Joshi, Yogendra; Committee Member: Mavris, Dimitri; Committee Member: Wepfer, William. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Thomas, Alex S. M. Massachusetts Institute of Technology. "An analysis of distributed solar fuel systems." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76511.
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Thesis (S.M. in Engineering and Management)--Massachusetts Institute of Technology, Engineering Systems Division, System Design and Management Program, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 85-89).
While solar fuel systems offer tremendous potential to address global clean energy needs, most existing analyses have focused on the feasibility of large centralized systems and applications. Not much research exists on the feasibility of distributed solar fuel systems. This thesis is an attempt to understand the larger context of solar fuel systems, to examine the case for going distributed and to critically analyze a distributed solar fuel system available today in the context of a specific application. In doing so, this thesis seeks to a) provide a baseline analysis for the economic feasibility of a distributed solar fuel system based on state-of-the-art technology b) draw some general conclusions about the nature of such systems in order to provide guidance to those engaged in the development of the next generation of solar fuel systems. This study also compares the chosen baseline solar fuel system with a traditional fossil fuel-based alternative and undertakes a cost-to-emissions trade-off analysis. A key finding of this thesis is that for solar fuel systems to be viable, cost and efficiency improvements in individual sub-systems won't be sufficient. Due attention needs to be given to bring down cost of the entire system. Another key finding is that if carbon emissions are considered as a decision-making criterion in addition to cost, even at current cost levels photovoltaic hydrogen systems compare favorably with existing fossil fuel-based alternatives such as diesel generators.
by Alex Thomas.
S.M.in Engineering and Management
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Stutz, Michael Jun. "Hydrocarbon fuel processing of micro solid oxide fuel cell systems." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17455.
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Tesfahunegn, Samson Gebre. "Fuel Cell Assisted PhotoVoltaic Power Systems." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16942.
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Distributed generation (DG) systems as local power sources have great potential to contribute toward energy sustainability, energy efficiency and supply reliability. This thesis deals with DGs that use solar as primary energy input, hydrogen energy storage and conversion technologies (fuel cells and water electrolyzers) as long term backup and energy storage batteries and supercapacitors as short term backup. Standalone power systems isolated from the grid such as those used to power remote area off-grid loads and grid connected systems running in parallel with the main utility grid or a microgrid for local grid support are treated. As cost is the key challenge to the implementation of PV-hydrogen DGs, the main focus is developing sound control methods and operating strategies to help expedite their viability in the near future. The first part of the thesis deals with modeling of system components such as PV generator, fuel cell, lead acid/Li-ion storage batteries, electrolyzer, supercapacitor, power electronic converters and auxiliaries such as hydrogen storage tank and gas compressor. The subsystems are modeled as masked blocks with connectable terminals in Matlab®/Simulink® enabling easy interconnection with other subsystems. The models of main subsystems are fully/partially validated using measurement data or data obtained from data sheets and literature. The second part deals with control and operating strategies in PV hybrid standalone power systems. The models developed in the first part are used to simulate integrated systems. An attempt is made to provide some answers on how the different power sources and energy storages can be integrated and controlled using power electronics and feedback control to enhance improved performance, longer life time, increased supply reliability and minimize fuel use. To this end, new control methods and operating strategies are proposed to mediate near optimal intersubsystem power flows. The third part of the thesis concerns grid connected PV-Fuel cell power systems. Control schemes and operating strategies for integrating PV and fuel cell hybrids into the grid to serve both local demand and weak grids are investigated. How hydrogen energy storage and conversion technologies can be controlled to suppress PV fluctuations in future utility grids are also explored. A smoothing algorithm enhanced by a stepwise constant forecast is developed to enable more smooth and subhourly dispatchable power to be fed to the grid. The proposed methods were verified through longtime simulation based on realistic irradiance data over a number of typical days/weeks using suitably defined performance indices. It was learned that using power electronics and sound control methods, PV-hydrogen DGs can be flexibly controlled to solve lifetime and performance issues which are generally considered economic bottle necks. For example, conventionally in PV-hydrogen hybrids, to improve performance and life time, more battery capacity is added to operate fuel cell and electrolyzer under more stable power conditions in the face of highly fluctuating PV generation to prevent low state of charge (SOC) operation of the battery. Contrarily, in this thesis a sound control method is proposed to achieve the same objectives without oversizing the battery. It is shown that the proposed method can give up to 20% higher battery mean state of charge than conventional operation while PV fluctuation suppression rates up to 40% for the fuel cell and 85% for the electrolyzer are found for three typical days. It is also established that by predictively controlling battery SOC instead of conventional SOC setpoint control, substantial improvements can be obtained (up to 20-30% increase in PV energy utilization and ca. 25% reduction in fuel usage for considered days). Concerning use of hydrogen storage and conversion technologies in PV fluctuation suppression, results obtained from the developed smoothing mechanism and performance indices show that a trade-off should be made between smoothing performance and dispatchability. It was concluded that the right size of fuel cell and electrolyzer needs to be selected to optimize the dispatch interval and smoothing performance. Finally, a PV-hydrogen test facility which can act as show case for standalone, grid-connected and UPS applications was designed and built. The test facility was used to characterize key subsystems from which component models developed were experimentally validated. The facility also acted as a reference system for most of the investigations made in this thesis.
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Barroqueiro, Sergio A. B. "Chromatic sensors for aircraft fuel systems." Thesis, University of Liverpool, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399038.
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Robbie, M. J. "Regenerative pumps for aircraft fuel systems." Thesis, Cranfield University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359572.
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LAMBERTI, THOMAS. "Fuel cell systems for marine applications." Doctoral thesis, Università degli studi di Genova, 2018. http://hdl.handle.net/11567/931185.
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The aim of this work is the assessment of the most suitable hydrogen solution for ship applications and the definition of the role of hydrogen as alternative fuel for shipping. The importance of the “Hydrogen Technologies” for ships comes from the most important social challenge that is driving innovation in the shipping sector: Environmental Challenge.
The PhD research project encountered important development both from the industrial and the academic side that brought to the construction of a joint laboratory between Fincantieri and the Polytechnic School of the University of Genoa, the: HI-SEA laboratory, dedicated to the study of fuel cell system for marine application. Moreover the simulation modelling and experimental results developed during the PhD research on the PEM fuel cell and MH hydrogen storage systems, found an application in the nautical sector. The former brought to a patent and the creation of a dedicated start-up company named H2Boat, that was recognised as University spin-off.
The first part of the study define the role of hydrogen as alternative energy vector (fuel) for marine application, analysing the complex context in which it is supposed to be used. In part 2.1 a detailed assessment of the characteristics of different alternative fuels have been conducted. The complexity of work brought to the construction of comparative models, descripted in part 2.2 that have been used to analyse the characteristic of various alternative solution. An analysis of the PEM FCS state of the art is presented in part 2.3 together with the definition of FCS design for marine application in part 2.4.
The study of the hydrogen technologies considered also the definition of simulation models of fuel cell systems and metal hydride hydrogen storage system 3.2. The former has also been assessed towards experimental tests, presented in part 3.3. The models have been used to develop larger laboratory, to define correct operative parameters and FCS design.
Finally a number of application developed during the PhD study are proposed in part 4 to show the goal of the research that is still under development.
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Pulido, Jon R. (Jon Ramon) 1974. "Modeling hydrogen fuel distribution infrastructure." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/29529.
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Thesis (M. Eng. in Logistics)--Massachusetts Institute of Technology, Engineering Systems Division, 2004.Includes bibliographical references (p. 70-73).
This thesis' fundamental research question is to evaluate the structure of the hydrogen production, distribution, and dispensing infrastructure under various scenarios and to discover if any trends become apparent after sensitivity analysis. After reviewing the literature regarding the production, distribution, and dispensing of hydrogen fuel, a hybrid product pathway and network flow model is created and solved. In the literature review, an extensive analysis is performed of the forthcoming findings of the National Academy of Engineering Board on Energy and Environmental Systems (BEES). Additional considerations from operations research literature and general supply chain theory are applied to the problem under consideration. The second section develops a general model for understanding hydrogen production, distribution, and dispensing systems based on the findings of the BEES committee. The second chapter also frames the analysis that the thesis will review using the model. In the problem formulation chapter, the details of the analytic model at examined at length and heuristics solution methods are proposed. Three heuristic methodologies are described and implemented. An in-depth discussion of the final model solution method is described. In the fourth chapter, the model uses the state of California as a test case for hydrogen consumption in order to generate preliminary results for the model The results of the MIP solutions for certain market penetration scenarios and the heuristic solutions for each scenario are shown and sensitivity analysis is performed. The final chapter summarizes the results of the model, compares the performance of heuristics, and indicates further areas for research, both in terms of developing strong lower bounds
(cont.) for the heuristics, better optimization techniques, and expanded models for consideration.
by Jon R. Pulido.
M.Eng.in Logistics
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Kroll, Douglas M. (Douglas Michael). "Using polymer electrolyte membrane fuel cells in a hybrid surface ship propulsion plant to increase fuel efficiency." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61909.
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Thesis (Nav. E.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (S.M. in Engineering and Management)--Massachusetts Institute of Technology, Engineering Systems Division, System Design and Management Program, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 59).
An increasingly mobile US Navy surface fleet and oil price uncertainty contrast with the Navy's desire to lower the amount of money spent purchasing fuel. Operational restrictions limiting fuel use are temporary and cannot be dependably relied upon. Long term technical research toward improving fuel efficiency is ongoing and includes advanced gas turbines and integrated electric propulsion plants, but these will not be implemented fleet wide in the near future. The focus of this research is to determine if a hybrid fuel cell and gas turbine propulsion plant outweigh the potential ship design disadvantages of physically implementing the system. Based on the potential fuel savings available, the impact on surface ship architecture will be determined by modeling the hybrid fuel cell powered ship and conducting a side by side comparison to one traditionally powered. Another concern that this solution addresses is the trend in the commercial shipping industry of designing more cleanly running propulsion plants.
Douglas M. Kroll.
S.M.in Engineering and Management
Nav.E.
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Shehadi, Charles A. III (Charles Anthony), and Michael R. Witalec. "How to utilize hedging and a fuel surcharge program to stabilize the cost of fuel." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61186.
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Thesis (M. Eng. in Logistics)--Massachusetts Institute of Technology, Engineering Systems Division, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 101-103).
This paper looks at some of these travails as well as the common tools used to approach a volatile priced commodity, diesel fuel. It focuses on the impacts of hedging for companies that are directly impacted through the consumption of diesel fuel in addition to companies that are indirectly impacted because they outsource their transportation. It examines the impact of a fuel surcharge and how it distributes risk throughout the supply chain. To complement the research, analysis was conducted in the form of a survey to benchmark the industry with respect to current practices of hedging and fuel surcharges, a sensitivity test of a fuel surcharge matrix to find its appropriate usage, and a simulation to provide guidance as to the appropriate strategy for hedging. Lessons learned from the survey flowed into the sensitivity testing and simulation. These three segments of analysis highlighted the problem of volatility, increasing cost, and inability to pass on the cost, proving the true pain of fuel in the market. Ultimately, the paper answers: How to utilize hedging and a fuel surcharge program to stabilize the cost of fuel? The survey showed the wide adoption of fuel surcharges, confirming the academic research. The sensitivity test proved the need to keep the escalator variable in line with a carrier's actual fuel efficiency and standardize for all carriers. The simulation recommended longer term derivatives. Putting this together, the fuel surcharge establishes stability for the carrier, at the risk of the shipper. The shipper must maintain that stability through its maintenance of the escalator in the fuel surcharge matrix. Additionally, the shipper should hedge fuel via long term derivatives to establish personal fuel cost stability, creating a competitive advantage and enabling the shipper to compete more effectively.
by Charles A. Shehadi, III and Michael R. Witalec.
M.Eng.in Logistics
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Colella, W. G. "Combined heat and power fuel cell systems." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411153.
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Blanchard, Tina-Louise. "A Systems Engineering Reference Model for Fuel Cell Power Systems Development." Cleveland State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=csu1322713336.
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Saxe, Maria. "Bringing fuel cells to reality and reality to fuel cells : A systems perspective on the use of fuel cells." Doctoral thesis, KTH, Energiprocesser, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9192.
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With growing awareness of global warming and fear of political instability caused by oil depletion, the need for a society with a sustainable energy system has been brought to the fore. A promising technology often mentioned as a key component in such a system is the fuel cell technology, i.e. the energy conversion technology in focus in this thesis. The hopes and expectations on fuel cells are high and sometimes unrealistically positive. However, as an emerging technology, much remains to be proven and the proper use of the technology in terms of suitable applications, integration with society and extent of use is still under debate. This thesis is a contribution to the debate, presenting results from two fuel cell demonstration projects, looking into the introduction of fuel cells on the market, discussing the prospects and concerns for the near-term future and commenting on the potential use in a future sustainable energy system. Bringing fuel cells to reality implies finding near-term niche applications and markets where fuel cell systems may be competitive. In a sense fuel cells are already a reality as they have been demonstrated in various applications world-wide. However, in many of the envisioned applications fuel cells are far from being competitive and sometimes also the environmental benefit of using fuel cells in a given application may be questioned. Bringing reality to fuel cells implies emphasising the need for realistic expectations and pointing out that the first markets have to be based on the currently available technology and not the visions of what fuel cells could be in the future. The results from the demonstration projects show that further development and research on especially the durability for fuel cell systems is crucial and a general recommendation is to design the systems for high reliability and durability rather than striving towards higher energy efficiencies. When reliability and durability are achieved fuel cell systems may be introduced in niche markets where the added values presented by the technology compensate for the initial high cost.QC 20100909
Energy Systems Programme
Clean Urban Transport for Europe
GlashusEtt
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Szakaly, Frank Joseph. "Assessment of uranium-free nitride fuels for spent fuel transmutation in fast reactor systems." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/31.
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The purpose of this work is to investigate the implementation of nitride fuels containing little or no uranium in a fast-spectrum nuclear reactor to reduce the amount of plutonium and minor actinides in spent nuclear fuel destined for the Yucca Mountain Repository. A two tier recycling strategy is proposed. Thermal spectrum transmutation systems converted from the existing LWR fleet were modeled for the first tier, and the Japanese fast reactor MONJU was used for the fast-spectrum transmutation. The modeling was performed with the Monteburns code. Transmutation performance was investigated as well as delayed neutron fraction, heat generation rates, and radioactivity of the spent material in the short and long term for the different transmutation fuel cycles. A two-tier recycling strategy incorporating fast and thermal transmutation with uranium-free nitride fuel was shown to reduce the long-term heat generation rates and radioactivity of the spent nuclear fuel inventory.
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Hines, Anne Michelle. "Characteristics of Active Combustion Control for Liquid-Fuel Systems with Proportional Primary Fuel Modulation." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/32569.
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The first part of this work focuses on control experiments performed on an unstable kerosene-fueled turbulent combustor. Using a phase shift controller and primary fuel modulation stability is successfully gained for a wide band of global equivalence ratios allowing the limitations of the control scheme to be characterized. It is shown that control signal saturation can significantly impact the ability of the control scheme to stabilize the system. Three different regions of controllability are defined based on the degree of saturation. A hysteresis behavior is also found to exist for the controller settings depending on whether stability is being maintained or realized for an unstable system.
The second part of this work focuses on the impact that primary fuel modulation has on the fuel spray. Measurements for a simplex nozzle and an air-assist nozzle are taken under both static and dynamic operating conditions with a Phase Doppler Anemometry system. The dynamic modulation is found to significantly impact the spray properties of both nozzles.
Master of Science
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Neerkaje, Abhijith. "Strategies for the introduction of alternative fuel vehicles in India." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/90697.
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Thesis: S.M. in Engineering and Management, Massachusetts Institute of Technology, Engineering Systems Division, System Design and Management Program, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 42-46).
Rapid growth in population and increase in disposable income has led to a robust increase in automotive sales in India. As in many parts of the world, the internal combustion engines are the dominant vehicle power train in India. This has led to increase in tailpipe emissions in congested cities as well as increased consumption of crude oil. India needs to devise effective strategies to introduce fuel efficient nonpolluting Alternative Fuel Vehicles (AFV) to reduce GHG emissions and reduce oil consumption. In 2013, the Government of India unveiled a National Electric Mobility Mission Plan to promote AFV sales in India in a coordinated manner. Many similar, well-intentioned programs have been tried in the past. However, the creation of sustainable AFV markets has remained a challenge. This work presents the development of a multiplatform system dynamics model that helps one explore the dynamics of adoption of AFVs in Indian context. Using the model we explore three unique policy scenarios where the adoption of AFVs is studied. We show that the successful AFV adoption is dependent not just on providing demand side incentives, but also on promoting the creation of the refueling infrastructure. Results also show that Plug in Hybrid Electric Vehicle has the potential to be the dominant alternative fuel vehicle platform in India provided effective policies are in place.
by Abhijith Neerkaje.
S.M. in Engineering and Management
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Ball, Barbara Jean 1955. "Using geographical information systems and neural networks to predict fuel moisture in homogeneous fuels." Thesis, The University of Arizona, 1994. http://hdl.handle.net/10150/278457.
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Computer models used to predict the pattern and rate of spread of fire in grasslands as well as other vegetation types rely on various inputs for their calculations. Because of the direct effect they have on the quantity of fuel available to carry a fire and the effects of moisture on the potential for fuel available to carry a fire and the effects of moisture on the potential for fuel to begin burning and to sustain a fire, fuel loading measurements, which are similar to production measurements in grasslands, and estimates of fuel moisture are two important variables to be considered when modeling fire behavior. The objective of this project is to determine if there is a relationship between measured environmental variables and the fuel moisture values at the same sample points which can be modeled with GIS data and neural networks. This study was carried out using a combination of field sampled data and common GIS data layers. The results demonstrate the potential for neural network analysis in this type of environmental problem.
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Azolibe, Ifeanyi. "Architecture of a cyber-physical system for aircraft fuel control systems tests." Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/8503/.
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The aircraft fuel control system makes sure an engine has the precise amount of fuel required to generate power and thrust for every stage of flight. It therefore plays a role in determining the economics of flight. In order to maintain the economic equilibrium of performance and flight safety, it undergoes a Maintenance Repair or Overhaul (MRO) service after several hours of operation. A critical aspect of the MRO service is the test performed to validate the airworthiness of a fuel control system before it returns to service. The test of aircraft fuel control systems is human-centric by design. The operator uses a network of test systems to generate in-flight conditions similar to what the Unit-Under-Test (UUT) experiences on-board an aircraft engine, then performs tests to validate and verify its airworthiness. Thereafter, test results are recorded for regulatory compliance reasons after each test is performed successfully. An analysis of the test specification for the UUT involved in this study revealed 90% of an operator’s touch-time is automatable. The functions of control, data processing, data entry and supervision must be achieved automatically if they are to be performed autonomously by a cyber-physical test system. But the automation of these activities at the micro level does not guarantee their autonomous execution at a macro level by such a cyber-physical system composed of the network of test systems. Therefore, knowledge of a multidisciplinary array of fundamental concepts and how they can be fused to execute the test of aircraft fuel control systems autonomously, have been developed as presented in this thesis. For the function of process control, the response of the processes used to set test conditions is ~ 50Hz, five times the rate of process responses reported in typical process industries where automation of process control have been achieved. As a result of this fundamental knowledge, the design of the architectures for the functions of control and data processing is an asynchronous one. Noting that none of the data is fed back through a network like the case of Networked Control Systems or Supervisory Control and Data Acquisition Systems. The realization of the control functions for each process used to set test conditions is based on control laws synthesized through modelling of their respective actuation mechanisms. Of the three models developed, a 2nd order model has been identified as been representative of the dynamic and steady-state characteristics of each actuation mechanism. A typical actuation mechanism contains a high number of masses and springs whose physical modelling resulted in a model of 12th order. This model is highly unrepresentative of the transient and steady-state response observed in the process due to difficulty in estimating the internal parameters of respective actuators. A linear model synthesized from the calibration data of each actuation mechanism has also been investigated and found to be too ideal. Its response is unrepresentative of the dynamic characteristics of the actuation mechanisms. The processes used to generate test conditions have been set simultaneously using a network of PID controllers. The controllers’ gains are an order of ten less than what they were for the sequential set up of test conditions due the fact that there are interactions between the processes inside a UUT. Fundamentally however, this Thesis demonstrates an asynchronous architecture for the control function, which enables a pseudo steady-state execution of tests. In-practice, this has the potential to reduce the time it takes to perform a test by one-third. The function of supervision has been developed in the form of a Fault Detection Isolation and Recovery capability within the cyber-physical test system. The architecture for this function is designed based on minimalizing the constraint of the period of recoverability (PoR), where the deviations from normal operation need to be detected, the outcomes they could result to—diagnosed and recovery strategies executed to prevent test systems or the UUT deviate from normal operation, using measurements acquired in a time < PoR. Oscillations and offsets have been identified as the major causes of deviations in subsystems during the test of the aircraft fuel control system in this study. In order to diagnose a deviation, a fuzzy inference engine has been developed over a Fault Tree Analysis approach because it makes the automation of domain knowledge needed to realize the supervision function effective. Nevertheless, the contributions of this thesis are the knowledge gaps it uncovers and the formalized approaches it proposes in the form of architectures to plug these gaps. It provides a direction on how to actualize not only the concept of automation, but the realization of a cyber-physical system to test an aircraft fuel control systems. It is the architecture of a singular system capable of executing the functions performed by an operator autonomously, and surpassing what can be achieved in the case of simultaneous process control, automated detection and isolation of a critical deviations under the period of recoverability, that is the fundamental contribution of this thesis. So that in the not so distant future the test of aircraft fuel control systems can be performed by machines.
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Skawinski, Grzegorz. "Fuel pump motor-drive systems for more electric aircraft." Thesis, University of Bath, 2010. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.527520.
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The fuel systems fitted to the current generation of civil transport aircraft are rather complicated, due to the presence of multiple tanks, pumps, valves and complex pipeline systems. During fuel transfer between the tanks, when controlling the aircraft centre of gravity or engine feed and refuel operations, a number of pumps and valves are involved resulting in complex pressure and flow interactions. In order to minimise the pressure surges during sudden system changes and flow overshoot during fuel transfer and refuelling, different motor drive system control strategies have been investigated. It is proposed that the current control method of electrically driven centrifugal-type pumps could be replaced by improved open and closed loop strategies where the flow overshoot can be minimised and pressure surges reduced. Steady-state and dynamic models of an AC induction motor drive and typical aircraft fuel system pipework components have been developed. The validation of these models has been performed using experimental data obtained from a fuel test rig constructed at the University of Bath using water as the working fluid. The simulation results have been shown to agree well with those from experimentation. In addition, the induction motor has been modelled based on its physical properties using the Finite Element Method software MEGA. The investigated fuel system has been described in linear terms and its behaviour has been identified. It is shown that the system dynamic behaviour can be controlled/improved using well established closed loop proportional-integral control. An open loop technique of simultaneous pump and valve control has been proposed and validated using experimental results, resulting in a reduction of both the transient pressure surges and flow overshoot during sudden valve closures, showing significant performance improvements. Improved closed loop control strategies for the pump drive system have also been developed in simulation. These are based on adaptive proportional-integral-derivative and fuzzy logic control strategies.
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Swedenborg, Samuel. "Modeling and Simulation of Cooling System for Fuel Cell Vehicle." Thesis, Uppsala universitet, Elektricitetslära, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-326070.
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This report is the result of a master’s thesis project which covers the cooling system in Volvo Cars’ fuel cell test vehicle. The purpose is to investigate if the existing cooling system in the fuel cell test vehicle works with the current fuel cell system of the vehicle, in terms of sufficient heat rejection and thus sustaining acceptable temperature levels for the fuel cell system. The project also aims to investigate if it is possible to implement a more powerful fuel cell system in the vehicle and keep the existing cooling system, with only a few necessary modifications. If improvements in the cooling system are needed, the goal is to suggest improvements on how a suitable cooling system can be accomplished. This was carried out by modeling the cooling system in the simulation software GT-Suite. Then both steady state and transient simulations were performed. It was found that the cooling system is capable of providing sufficient heat rejection for the current fuel cell system, even at demanding driving conditions up to ambient temperatures of at least 45°C. Further, for the more powerful fuel cell system the cooling system can only sustain sufficient heat rejection for less demanding driving conditions, hence it was concluded that improvements were needed. The following improvements are suggested: Increase air mass flow rate through the radiator, increase pump performance and remove the heat exchanger in the cooling system. If these improvements were combined it was found that the cooling system could sustain sufficient heat rejection, for the more powerful fuel cell system, up to the ambient temperature of 32°C.
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Gavel, Hampus. "On aircraft fuel systems : conceptual design and modeling." Doctoral thesis, Linköping : Division of Machine Design, Department of Mechanical Engineering, Linköpings universitet, 2007. http://www.bibl.liu.se/liupubl/disp/disp2007/tek1067s.pdf.
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McFarlane, Alexander. "Biofilm development and management in aircraft fuel systems." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/17655/.
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Tarud, Sofy 1980. "Feasibility of fuel cell systems for building applications." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/27135.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (p. 109-110).
Worldwide electricity consumption will nearly double between 2001 and 2025 but the projects to increase electricity production and transport will not be enough to fulfill the demand. In the future, most of the power demand will be produced by Distributed Generation (DG) systems. DG refers to power generating technologies independent from the electrical grid, located at or near the location where electricity is consumed. Fuel Cells have become very attractive DG systems in recent years, however, Fuel Cells are still in their early stages of deployment and the advantages and disadvantages of such systems for commercial applications are unclear. A study to learn how Fuel Cells perform in commercial buildings was conducted. To compare the effectiveness of fuel cells to other prime movers the study looked at Phosphoric Acid and Molten Carbonate Fuel Cells, microturbines, and lean burning reciprocating engines. First, the hotel's natural gas and electricity load data was analyzed to understand the requirements and adequately size the DG systems. After, the economics and efficiency of the plant was looked at with and without opportunity for cogeneration. Finally, a sensibility analysis was conducted to assess the variability of the plant's savings if some of the assumed parameters changed PAFC and MCFC, in baseload operation, with and without an absorption chiller are both very attractive technologies for a DG installation at the hotel if initial capital costs are reduced. The initial capital investment of fuel cells can and should be reduced, either by government and/or utility incentives or decreases in costs due to economies of scale.
by Sofy Tarud.
S.M.
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DE, CAMPO MARCO. "Analysis and modeling of PEM fuel cell systems." Doctoral thesis, Università degli studi di Genova, 2019. http://hdl.handle.net/11567/945505.
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Analisi e modellazione di sistemi a celle a combustibile di tipo PEMThe purpose of this thesis is to create a transient model of a PEM fuel cell system, based on Matlab Simulink, as general, flexible and adaptable as possible, in order to be easily set on different type of systems. The object of the study is the development of the simulation tool, and its validation against literature and experimental data. An important aim of the developed dynamic semi-empirical model is to try to adopt a theoretical physics-based approach whenever possible, in order to have an accurate scientific correlation between experimental output and theoretical laws, without neglecting the accuracy that could be provided by empirical equations. The major work is focused on the fuel cell stack modeling and involves also a large review of literature analysis concerning the simulation of PEM-FCs. In order to guarantee the adaptability of the model, taking inspiration from the latest studies in this field, a differential evolution algorithm is developed to realize the fitting process of the modeled polarization curve, by means of the stack voltage model, on experimental data. This algorithm has a strategic importance for the choice and the setting of the stack voltage equations on the real static performance of the PEM fuel cell system analyzed, with a proved error of about 2-3%. The transient behaviors captured in the model includes flow characteristics, inertia dynamics, lumped-volume manifold filling dynamics, time evolving-homogeneous reactant pressure or mole fraction, membrane humidity and thermal response of fuel cell and cooling system. From one side, the validation against literature data of Section 4 is realized after the development of a general dynamic PEM-FC system model described in Section 2 and 3, comprising all the components normally present in these systems. The comprehensive dynamic model proposed, usually not presented in literature, perform very well respect to the experimental data, comprising the thermic data and the hydration of the membrane, the most important operative parameters but also the most complex ones to simulate. On the other side, the HI-SEA Joint Laboratory, between Fincantieri S.p.A. and the University of Genoa, allows to study a PEM fuel cell system of 8 stacks sized 33 kW each for a total maximum power of 260 kW. The adaptation and the simplification of the dynamic model to this plant layout helps to study a bigger and more complex PEM-FC system and to validate the model to the experimental data. The simplification of the dynamic model starts form the necessity to set the equations only by the commercially available data, usually limited to the datasheet information. This limitation makes the HI-SEA model less detailed but, at the same time, simpler and able to provide different important results, as the stack and cooling system thermal balances, starting from few easily obtainable data.
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ABRASSI, ALESSIO. "Fuel cell hybrid systems, dynamics and surge analysis." Doctoral thesis, Università degli studi di Genova, 2019. http://hdl.handle.net/11567/945503.
Full textAbstract:
The improvement of energy system performance has led to the development of efficient dynamic compressors able to achieve high compression ratios, high flow rates of fluid and reduced weights. As it normally happens by nature, the higher is the desired performance the more difficult is to achieve it; in the case of dynamic compression, the need to reach increasingly higher compression ratios and larger operational flexibility involves the occurrence of unsteady phenomena such as rotating stall and surge. These two problematic phenomena characterize compressors with violent decrease of performance and severe damage to machines, consequently the topic has been object of several studies over the years. The intensity and behavior of surge are tightly connected to the amount of volumes coupled to the turbo machinery during its operation. For this reason, surge phenomenon is strongly felt in fuel cell gas turbine hybrid system applications, where, primarily the fuel cell, then all the other components (e.g. heat exchangers if present), auxiliaries and connections constitute the vast majority of the volume contained in the system. This work is organized into three macro-chapters, each one is focused on a specific application. The descriptive organization follows the chronological order in which the case studies were addressed and follows the level of maturity of the research object of this program. Therefore, in the following chapters each single case study is presented and discussed separately. The following list anticipates what are the main outcomes and learnings which will be encountered through the text. In this way the candidate wants to clearly summarize what can be considered as primary steps, contribution to the energy systems modeling research field and main outputs of this work:
- Mathematical descriptions for components development with integrations and improvements will be described application by application.
- Description of the proposed steps followed by the methodologies used to extend compressor maps for surge simulation purposes. A mix of analytical
and empirical methods will be suggested through this work.
- A method for dynamic delays characterization of complex piping systems named τ-Flow approach have been proposed and applied to these studies.
- Parametric studies to investigate the effect of different parameters such as volume size, shaft inertia and equivalent lengths, on the surge cycles
characteristics. Impacts of these characteristics will be analyzed in different control configurations where options are applicable.
- Simulation results, experimental comparison and validation will be presented at the end of each macro-chapter as completion of the analysis.
- The possibility to recover from a surge event acting on by pass valves will be also simulated and presented in the context of Hyper facility analysis.
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Bindingnolle, Narasimha Srivatsa. "Predictive modeling of fuel efficiency of trucks." Thesis, State University of New York at Binghamton, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10092244.
Full textAbstract:
This research studied the behavior of several controllable variables that affect the fuel efficiency of trucks. Re-routing is the process of modifying the parameters of the routes for a set of trips to optimize fuel consumption and also to increase customer satisfaction through efficient deliveries. This is an important process undertaken by a food distribution company to modify the trips to adapt to the immediate necessities. A predictive model was developed to calculate the change in Miles per Gallon (MPG) whenever a re-route is performed on a region of a particular distribution area. The data that was used, was from the Dallas center which is one of the distribution centers owned by the company. A consistent model that could provide relatively accurate predictions across five distribution centers had to be developed. It was found that the model built using the data from the Corporate center was the most consistent one. The timeline of the data used to build the model was from May 2013 through December 2013. The predictive model provided predictions of which about 88% of the data that was used, was within the 0-10% error group. This was an improvement on the lesser 43% obtained for the linear regression and K-means clustering models. The model was also validated on the data for January 2014 through the first two weeks of March 2014 and it provided predictions of which about 81% of the data was within the 0-10 % error group. The average overall error was around 10%, which was the least for the approaches explored in this research. Weight, stop count and stop time were identified as the most significant factors which influence the fuel efficiency of the trucks. Further, neural network architecture was built to improve the predictions of the MPG. The model can be used to predict the average change in MPG for a set of trips whenever a re-route is performed. Since the aim of re-routing is to reduce the miles and trips; extra load will be added to the remaining trips. Although, the MPG would decrease because of this extra load, it would be offset by the savings due to the drop in miles and trips. The net savings in the fuel can now be translated into the amount of money saved.
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Johnson, Kyle D. "High Performance Fuels for Water-Cooled Reactor Systems." Doctoral thesis, KTH, Reaktorfysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-201604.
Full textAbstract:
Investigation of nitride fuels and their properties has, for decades, been propelled on the basis of their desirable high metal densities and high thermal conductivities, both of which oer intrinsic advantages to performance, economy, and safety in fast and light water reactor systems. In this time several key obstacles have been identied as impeding the implementation of these fuels for commercial applications; namely chemical interactions with air and steam, the noted diculty in sintering of the material, and the high costs associated with the enrichment of 15N. The combination of these limitations, historically, led to the well founded conclusion that the most appropriate use of nitride fuels was in the fast reactor fuel cycle, where the cost burdens associated with them is substantially less. Indeed, it is within this context that the vast majority of work on nitrides has been and continues to be done. Nevertheless, following the 2011 Fukushima-Daiichi nuclear accident, a concerted governmental-industrial eort was embarked upon to explore the alternatives of so-called \accident tolerant" and \high performance" fuels. These fuels would, at the same time, improve the response of the fuel-clad system to severe accidents and improve the economy of operation for light water reactor systems. Among the various candidates proposed are uranium nitride, uranium silicide, and a third \uranium nitride-silicide" composite featuring a mixture of the former. In this thesis a method has been established for the synthesis, fabrication, and characterization of high purity uranium nitride, and uranium nitride-silicide composites, prepared by the spark plasma sintering (SPS) technique. A specic result has been to isolate the impact of the processing parameters on the microstructure of representative fuel pellets, essentially permitting any conceivable microstructure of interest to be fabricated. This has enabled the development of a highly reproducible technique for the production of pellets with microstructures tailored towards any desired porosity between 88-99.9%TD, any grain size between 6-24 μm, and, in the case of the uranium nitride-silicide composite, a silicide-coated UN matrix. This has permitted the evaluation of these microstructural characteristics on the performance of these materials, specically with respect to their role as accident tolerant fuels. This has generated results which have tightly coupled nitride performance with pellet microstructure, with important implications for the use of nitrides in water-cooled reactors.Under artionden har forskning om nitridbranseln och dess egenskaper bedrivits pa grundval av nitridbransletsatravarda egenskaper avseende dess hoga metall tathet och hog varmeledningsformaga. Dessa egenskaper besitter vasentliga fordelar avseende prestanda, ekonomi och sakerhet for metallkylda som lattvatten reaktorer. Genom forskning har aven centrala begr ansningar identierats for implementering av nitridbranslen for kommersiellt bruk. Begransningar avser den kemiska interaktionen med luft och vattenanga, en uppmarksammad svarighet att sintring av materialet samt hoga kostnader forknippade med den nodvandiga anrikningen av 15-N. Kombinationen av dessa begransningar resulterade, tidigare, i en valgrundad slutsats att nitridbranslet mest andamalsenliga anvandningsomrade var i karnbranslecykeln for snabba reaktorer. Detta da kostnaderna forenade med implementeringen av branslet ar avsevart lagre. Inom detta sammanhang har majoriteten av forskning avseende nitrider bedrivits och fortskrider an idag. Dock, efter karnkraftsolyckan i Fukushima-Daiichi 2011, inleddes en samlad industriell och statlig anstrangning for att undersoka alternativ till sa kallade \olyckstoleranta" och \hogpresterande" branslen. Dessa branslen skulle samtidigt forbattra reaktionstiden for bransleinkapsling systemet mot allvarliga olyckor samt forbattra driftsekonomin av lattvattenreaktorer. Foreslagna kandidater ar urannitrid, uransilicid och en tredje \uran nitrid-silicid", komposit bestaende av en blandning av de foregaende. Genom denna avhandling har en metod faststallts for syntes, tillverkning och karaktarisering av uran nitrid av hog renhet samt uran nitrid-silicid kompositer, forberedda med tekniken SPS (Spark Plasma Sintering). Ett specikt resultat har varit att isolera eekten av processparametrar pa mikrostrukturen pa representativa branslekutsar. Detta mojliggor, i princip, framstallningen av alla tankbara mikrostrukturer utav intresse for tillverkning. Vidare har detta mojliggjort utvecklingen av en hogeligen reproducerbar teknik for framstallningen av branslekutsar med mikrostrukturer skraddarsydda for onskad porositet mellan 88 och 99.9 % TD, och kornstorlek mellan 6 och 24 μm. Dartill har en metod for att belagga en matris av uran nitrid-silicid framarbetats. Detta har mojliggjort utvarderingen av dessa mikrostrukturella parametrars paverkan pa materialens prestanda, sarskilt avseende dess roll som olyckstoleranta branslen. Detta har genererat resultat som ar tatt sammanlankat nitridbranslets prestanda till kutsens mikrostruktur, med viktiga konsekvenser for den potentiella anvandningen av nitrider i lattvatten reaktorer.
QC 20170210
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Hedström, Lars. "Fuel Cells and Biogas." Doctoral thesis, KTH, Energiprocesser, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-13219.
Full textAbstract:
This thesis concerns biogas-operated fuel cells. Fuel cell technology may contribute to more efficient energy use, reduce emissions and also perhaps revolutionize current energy systems. The technology is, however, still immature and has not yet been implemented as dominant in any application or niche market. Research and development is currently being carried out to investigate whether fuel cells can live up to their full potential and to further advance the technology. The research of thesis contributes by exploring the potential of using fuel cells as energy converters of biogas to electricity. The work includes results from four different experimental test facilities and concerns experiments performed at cell, stack and fuel cell system levels. The studies on cell and stack level have focused on the influence of CO, CO2 and air bleed on the current distribution during transient operation. The dynamic response has been evaluated on a single cell, a segmented cell and at stack level. Two fuel cell systems, a 4 kW PEFC system and a 5 kW SOFC system have been operated on upgraded biogas. A significant outcome is that the possibility of operating both PEFCs and SOFCs on biogas has been established. No interruptions or rapid performance loss could be associated with the upgraded biogas during operation. From the studies at cell and stack level, it is clear that CO causes significant changes in the current distribution in a PEFC; air bleed may recover the uneven current distribution and also the drop in cell voltage due to CO and CO2 poisoning. The recovery of cell performance during air bleed occurs evenly over the electrode surface even when the O2 partial pressure is far too low to fully recover the CO poisoning. The O2 supplied to the anode reacts on the anode catalyst and no O2 was measured at the cell outlet for air bleed levels up to 5 %. Reformed biogas and other gases with high CO2 content are thus, from dilution and CO-poisoning perspectives, suitable for PEFC systems. The present work has enhanced our understanding of biogas-operated fuel cells and will serve as basis for future studies.QC20100708
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Shevock, Bryan Wesley. "System Level Modeling of Thermal Transients in PEMFC Systems." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/31079.
Full textAbstract:
Fuel cell system models are key tools for automotive fuel cell system engineers to
properly size components to meet design parameters without compromising efficiency
by over-sizing parasitic components. A transient fuel cell system level model is being
developed that includes a simplified transient thermal and parasitics model. Model
validation is achieved using a small 1.2 kW fuel cell system, due to its availability. While
this is a relatively small stack compared to a full size automotive stack, the power,
general thermal behavior, and compressor parasitics portions of the model can be
scaled to any number of cells with any size membrane area. With flexibility in
membrane size and cell numbers, this model can be easily scaled to match full
automotive stacks of any size.
The electrical model employs a generalized polarization curve to approximate system
performance and efficiency parameters needed for the other components of the model.
General parameters of a stackâ s individual cells must be known to scale the stack
model. These parameters are usually known by the time system level design begins.
The thermal model relies on a lumped capacity approximation of an individual cell
system with convective cooling. From the thermal parameters calculated by the model,
a designer can effectively size thermal components to remove stack thermal loads.
The transient thermal model was found to match experimental data well. The steady
state and transient sections of the curve have good agreement during warm up and cool
down cycles.
In all, the model provides a useful tool for system level engineers in the early stages of
stack system development. The flexibility of this model will be critical for providing
engineers with the ability to look at possible solutions for their fuel cell power
requirements.Master of Science
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De, Roo Guillaume. "Economics of nuclear fuel cycles : option valuation and neutronics simulation of mixed oxide fuels." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/57540.
Full textAbstract:
Thesis (S.M. in Technology and Policy)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 71-73).
In most studies aiming at the economic assessment of nuclear fuel cycles, a primary concern is to keep scenarios economically comparable. For Uranium Oxide (UOX) and Mixed Oxide (MOX) fuels, a traditional way to achieve this is to evaluate both fuels on the deterministic premise that the fuel will be sent to geologic disposal once spent. This methodology often leads to higher costs for cycles using MOX fuel. Geologic disposal is not the sole possible ending for spent LightWater Reactor (LWR) fuel. Fast Reactors (FRs), which feed on transuranics (TRUs) extracted from LWR spent fuel, are seriously considered as a future technology. If it is cheaper to extract TRUs from spent MOX than from UOX, then the relative cost of a fuel cycle using MOX fuel may be less than in the case of their geologic disposal. However, the commercial development of FR cycles is uncertain. The value of UOX and MOX is therefore not the deterministic value in case of geologic disposal or in case of reprocessing into FRs. This thesis develops a method to assess the cost of thermal reactor fuel cycles in the presence of uncertainties in back-end management. The representation of future progress in FR technology through a resulting value of TRUs exhibits the properties of MOX as a financial option on the marginal TRU extraction cost. The framework establishes a significant modification of the back-end costs for countries using MOX, compared to traditional valuations. However, these savings do not completely offset the higher costs of recycling in the reference case.
by Guillaume De Roo.
S.M.
S.M.in Technology and Policy
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Ahlgren, Serina. "Crop production without fossil fuel : production systems for tractor fuel and mineral nitrogen based on biomass /." Uppsala : Dept. of Energy and Technology, Swedish University of Agricultural Sciences, 2009. http://epsilon.slu.se/200978.pdf.
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Feroldi, Diego Hernán. "Control and design of pem fuel cell-based systems." Doctoral thesis, Universitat Politècnica de Catalunya, 2009. http://hdl.handle.net/10803/5958.
Full textAbstract:
Las pilas de combustible son muy ventajosas debido a su alta eficiencia en la conversión de energía y nula contaminación. En esta tesis se realiza un extenso estudio sobre el control y diseño de sistemas de generación eléctrica basados en pilas de combustible. El núcleo principal de la misma son los sistemas híbridos con pilas de combustible y supercapacitores como elementos almacenadores de energía, orientado a aplicaciones automotrices. La determinación del Grado de Hibridización (i.e. la determinación del tamaño de la pila de combustible y del número de supercapacitores) se realiza mediante una metodología propuesta con el objetivo de satisfacer requisitos de conductibilidad y consumiendo la menor cantidad de hidrógeno posible.El proceso de diseño comienza con la determinación de la estructura eléctrica de generación del vehículo y utiliza un modelo detallado realizado en ADVISOR, una herramienta para modelado y estudio de sistemas híbridos. Se analiza el flujo de energía a través de los componentes del vehículo cuando el vehículo sigue diferentes ciclos de conducción estándares, mostrando las pérdidas en cada componente que degradan la eficiencia del sistema y limitan la recuperación de energía de frenado. Con respecto a la recuperación de energía, se ha definido y analizado un parámetro que cuantifica la cantidad de energía que realmente es reaprovechada: el ratio frenado/hidrógeno.
Para controlar el flujo de energía entre la pila de combustible, los almacenadores de energía y la carga eléctrica, se proponen tres Estrategias de Gestión de Energía (EMS) para Vehículos Híbridos con Pila de Combustible (FCHVs) basadas en el mapa de eficiencia de la pila y se validan mediante un montaje experimental desarrollado para emular el sistema híbrido. Los resultados de consumo de hidrógeno son comparados con dos referencias: el consumo correspondiente al caso del vehículo sin hibridización y el caso óptimo con el menor consumo para el vehículo propuesto. El consumo óptimo se calcula mediante una metodología propuesta que, a diferencia de otras, evita la discretización de las variables de estado.
Para operar el sistema eficientemente, la pila de combustible es controlada mediante una metodología de control, basada en Control de Matriz Dinámica (DMC). Esta metodología de control utiliza como variables de control el voltaje de compresor y una nueva variable propuesta: la apertura de una válvula proporcional ubicada a la salida del cátodo. Los objetivos de control son controlar el exceso de oxígeno en el cátodo y el voltaje generado por la pila. Se analiza tanto en régimen estacionario como transitorio las ventajas de emplear esta nueva variable de control y se muestran resultados de funcionamiento por simulación del controlador ante perturbaciones en la corriente de carga.
Por otro lado, se aborda el diagnóstico y el control tolerante a fallos del sistema basado en pila de combustible proponiendo una metodología de diagnóstico basada en las sensibilidades relativas de los fallos y se muestra que la estructura de control con las dos variables propuestas tiene buena capacidad de rechazo a fallos en el compresor cuando se controla el exceso de oxígeno en el cátodo.
The use of fuel cell systems based on hydrogen is advantageous because of their high efficiency in the energy conversion and null emissions. In this thesis, an extensive study about the control and design of electrical generation systems based on fuel cells is performed. The main focus is in hybrid systems composed of fuel cells and supercapacitors as energy storage elements, oriented to automotive applications. The determination of the hybridization degree (i.e. the determination of the fuel cell size and the number of supercapacitors) is performed through a proposed methodology with the objective to fulfil the conductibility requirements and to consume the lowest amount of hydrogen.
The process of design starts with the determination of the electrical structure and utilizes a detail model developed using ADVISOR, a MATLAB toolbox for modelling and studying hybrid vehicles. The energy flow between the vehicle components is analyzed when the vehicle is tested with different Standard Driving Cycles, showing how the losses in each component degrade the efficiency of the system and limit the energy recovery from braking.
With regard to the energy recovery, a parameter to quantify the amount of energy that is actually reused is defined and analyzed: the braking/hydrogen ratio.
To control the energy flow between the fuel cell, the energy storage system, and the electrical load in Fuel Cell Hybrid Vehicles (FCHVs), three Energy Management Strategies (EMSs) based on the fuel cell efficiency map are presented and validated through an experimental setup, which is developed to emulate the FCHV. The resulting hydrogen consumptions are compared with two references: the consumption of the pure fuel cell case, a vehicle without hybridization, and the optimal case with the minimum consumption. The optimal consumption for a given vehicle is determined through a methodology proposed that, unlike other previous methodologies, avoids the discretization of the state variables.
To operate the fuel cell system efficiently, the system is controlled through a proposed control technique, which is based on Dynamic Matrix Control (DMC). This control technique utilizes the compressor voltage as control variable and also a new proposed variable: the opening area of a proportional valve at the cathode outlet. The control objectives are the control of the oxygen excess ratio at the cathode and the fuel cell voltage. The advantages of this new control variable are analyzed both in steady state and transient state. Simulation results show and adequate performance of the controller when a series of step changes in the load current is applied.
On the other hand, the diagnosis and fault-tolerant control of the fuel cell-based system is approached. A diagnosis methodology based on the relative fault sensitivity is proposed. The performance of the methodology to detect and isolate a set of proposed failures is analyzed and simulation results in an environment developed to include the set of faults are given. The fault-tolerant control is approached showing that the proposed control structure with two control variables has good capability against faults in the compressor when the oxygen excess ratio in the cathode is controlled.
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Nilsson, Marita. "Hydrogen Generation for Fuel Cells in Auxiliary Power Systems." Doctoral thesis, KTH, Kemiteknik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10024.
Full textAbstract:
Heavy-duty trucks are in idle operation during long periods of time, providing the vehicles with electricity via the alternator at standstill. Idling trucks contribute to large amounts of emissions and high fuel consumption as a result of the low efficiency from fuel to electricity. Auxiliary power units, which operate independently of the main engine, are promising alternatives for supplying trucks with electricity. Fuel cell-based auxiliary power units could offer high efficiencies and low noise. The hydrogen required for the fuel cell could be generated in an onboard fuel reformer using the existing truck fuel. The work presented in this thesis concerns hydrogen generation from transportation fuels by autothermal reforming focusing on the application of fuel cell auxiliary power units. Diesel and dimethyl ether have been the fuels of main focus. The work includes reactor design aspects, preparation and testing of reforming catalysts including characterization studies and evaluation of operating conditions. The thesis is a summary of five scientific papers. Major issues for succeeding with diesel reforming are fuel injection, reactant mixing and achieving fuel cell quality reformate. The results obtained in this work contribute to the continued research and development of diesel reforming catalysts and processes. A diesel reformer, designed to generate hydrogen to feed a 5 kWe polymer electrolyte fuel cell has been evaluated for autothermal reforming of commercial diesel fuel. The operational results show the feasibility of the design to generate hydrogen-rich gases from complex diesel fuel mixtures and have, together with CFD calculations, been supportive in the development of a new improved reformer design. In addition to diesel, the reforming reactor design was shown to run satisfactorily with other hydrocarbon mixtures, such as gasoline and E85. Rh-based catalysts were used in the studies and exhibit high performance during diesel reforming without coke formation on the catalyst surface. An interesting finding is that the addition of Mn to Rh catalysts appears to improve activity during diesel reforming. Therefore, Mn could be considered to be used to decrease the noble metal loading, and thereby the cost, of diesel reforming catalysts. Dimethyl ether is a potential diesel fuel alternative and has lately been considered as hydrogen carrier for fuel cells in truck auxiliary power units. The studies related to dimethyl ether have been focused on the evaluation of Pd-based catalysts and the influence of operating parameters for autothermal reforming. PdZn-based catalysts were found to be very promising for DME reforming, generating product gases with high selectivity to hydrogen and carbon dioxide. The high product selectivity is correlated to PdZn interactions, leading to decreased activity of decomposition reactions. Auxiliary power systems fueled with DME could, therefore, make possible fuel processors with very low complexity compared to diesel-fueled systems. The work presented in this thesis has enhanced our understanding of diesel and DME reforming and will serve as basis for future studies.QC 20100804
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Baniasad, Mohammad Saeid. "Analysis of fuel injection rate in diesel injection systems." Thesis, Imperial College London, 1994. http://hdl.handle.net/10044/1/7439.
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Tseronis, Konstantinos. "Modelling and Design of Solid Oxide Fuel Cell Systems." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511906.
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Lake, Timothy Hugh. "Gasoline combustion systems for improved fuel economy and emissions." Thesis, University of Brighton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302289.
Full textAbstract:
This document is the statement of independent and original contribution to knowledge represented by the published works in partial fulfilment of the requirements of the University of Brighton for the degree of Doctor of Philosophy (by publication). The thesis reviews the impact of research work conducted between 1992 and 1998 on various concepts to improve the economy and emissions of gasoline engines in order to address environmental and legislative pressures. The research has a common theme, examining the dilution of the intake charge (with either recycled exhaust gas [EGR], excess air, or the two in combination) in both conventional port injected [MPI] and direct injection [G-DI] combustion systems. After establishing the current status of gasoline engine technology before the programme of research was started, the thesis concentrates on seven major pieces of research between 1992 and 1996. These explored a subsequently patented method of applying recycled exhaust gas to conventional port injected gasoline engines to improve their economy and emissions whilst staying compatible with three-way catalyst systems. Nine other studies are reviewed which took place between 1992 and 1999 covering other methods of improving gasoline engines, specifically direct injection and two-stroke operation. Together, all the studies provide a treatise on methods to improve the gasoline engine and the thesis allows a view from a broader perspective than was possible at the time each study was conducted. In particular, the review identifies a range of strategies that use elements of the research that can be used to improve economy and emissions. Four major categories of systems researched include: conventional stoichiometric MPI engines developed to tolerate high EGR rates [CCVS]; two-stroke G-DI engines; G-DI engines operating stoichiometrically with high EGR rates; and G-DI engines operating with high dilution from both excess air and EGR. The findings of the studies illustrate that although good fuel economy improvements and emissions can be obtained with EGR dilution of stoichiometric engines, the highest fuel economy improvements require lean deNOx aftertreatment [LNA] and these, in turn, require new aftertreatment technologies and preferably new fuel specifications. The development of suitable LNA and the cost of implementation of these approaches represents one of the main barriers to improving gasoline engine fuel economy and emissions.
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McCahey, Sharon. "The integration of fuel cells into power generation systems." Thesis, University of Ulster, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284835.
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Garcia, Jorge David S. M. Massachusetts Institute of Technology. "Sodium chlorate oxygen generation for fuel cell power systems." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112489.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 95-97).
In this thesis we experimentally investigated the use of sodium chlorate as an oxygen storage medium for use in underwater fuel cell power systems. Research into improving hydrogen storage systems is the primary concern when designing fuel cell systems with access to atmospheric oxygen. However, in an underwater environment, performance of the oxygen storage system cannot be overlooked. Oxygen candles using sodium chlorate offer gravimetric storage densities similar to compressed gas storage while also offering volumetric storage densities greater than both gas and cryogenic liquid oxygen storage. Unfortunately, this technology does not allow for controllable rates of oxygen production and is known to cause fires and occasionally explosions when contaminated with organic materials or exposed to external sources of heat. Though useful as an emergency source of oxygen, sodium chlorate will not be viable for use in power systems until safer and more controllable methods of releasing its oxygen are implemented. During this project we developed a batch method for releasing oxygen from sodium chlorate. Two grams of sodium chlorate with nanoscale cobalt oxide catalyst were loaded into a reaction chamber and heated until decomposition. Afterwards a piston was used to eject the materials from the reaction chamber. This method proved to be safer and more reliable than similar chlorate-based oxygen systems as the primary modes of failure, those associated with the buildup of solid residue at the inlets and exits of the reaction chamber, were removed. Aside from preventing the flow of oxygen to a fuel cell, the over-pressurization caused by these problems could compromise the reaction chamber and potentially result in catastrophic failures. The achieved rate of oxygen production, 0.21 L/min with a heating rate between 25 W and 33 W, was below the target 1.13 L/min needed to operate a 200 W PEM fuel cell. Further assessment of this method will require the use of a more active cobalt oxide catalyst, a system with a larger reaction chamber capable of decomposing increased amounts sodium chlorate per cycle and a reduction in heat losses through the use of improved insulation and thermal isolation techniques.
by Jorge David Garcia.
S.M.
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Arana, Leonel R. "High-temperature microfluidic systems for thermally-efficient fuel processing." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/7995.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2003.Includes bibliographical references (p. 231-238).
Miniaturized fuel cell systems have the potential to outperform batteries in powering a variety of portable electronics. The key to this technology is the ability to efficiently process an easily-stored, energy-dense fuel. In many cases, use of these fuels requires a fuel processor-a high temperature chemical reactor that generates a hydrogen-rich stream for use by the fuel cell. In high-temperature microfluidic systems, where heat transfer rates are often very high, thermal management is a major challenge. This thesis investigates the use of silicon microfabrication technology to fabricate high-temperature submillimeter-scale fuel processors designed to maximize thermal efficiency. A prototype MicroElectroMechanical Systems (MEMS) chemical reactor/heat exchanger for fuel processing has been designed and fabricated. The fuel processor, measuring 8x 10x 1.5 mm, consists of thin-walled silicon nitride tubes and a suspended silicon reaction zone. This structure couples the energy between catalytic combustion and decomposition or steam reforming reactions to produce hydrogen. The design enables a high level of thermal isolation of the reaction zone while allowing heat exchange between process streams. Thermal management in the fuel processors has been characterized up to 825⁰C through experimental testing using integrated resistive heaters and temperature sensors and through finite element modeling. Catalyst localization, for controlled catalytic combustion of premixed fuels in the reaction zone, has been achieved using passive fluidic stop valves. Ammonia decomposition (cracking) and combustion of various fuels over washcoated supported-metal catalysts have been investigated.
(cont.) Using the energy provided by the integrated heater to drive the reaction, up to 1.6 WLHV (based on the lower heating value) of hydrogen has been produced by catalytic ammonia decomposition at temperatures exceeding 800⁰C. Hydrogen burns stably in stoichiometric mixtures with air to >99% conversion for flow rates of hydrogen between 2 and 12 ml-min-1 and steady-state reactor temperatures between 400 and 930⁰C. At higher hydrogen flow rates and reactor temperatures, homogeneous combustion has been observed. Self-sustained (autothermal) combustion of butane at atmospheric pressure and ammonia under reduced ambient pressure (down to 4 Pa) have also been demonstrated. Hydrogen has been produced via ammonia decomposition using energy from hydrogen, butane, and ammonia combustion to drive the reaction.
by Leonel R. Arana.
Ph.D.
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Sevencan, Suat. "Economic Aspects of Fuel Cell-Based Stationary Energy Systems." Doctoral thesis, KTH, Tillämpad elektrokemi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-179137.
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It is evident that human activity has an important impact on climate. Constantly increasing energy demand is one of the biggest causes of climate change. The fifth assessment report of the Inter-governmental panel on climate change states that decarbonisation of electricity generation is a key component of climate change mitigation. Increased awareness of this fact and escalating concerns around energy security has brought public attention to the energy industry, especially sustainable power generation systems. Future energy systems may need to include hydrogen as an energy carrier in order to achieve necessary levels of CO2 emission reductions, and overcome the challenges renewable energy systems present. Fuel cells could be a corner stone of future hydrogen inclusive energy solutions. New solutions like fuel cells have to compete with existing technologies and overcome the shortcomings of emerging technology. Though these shortcomings are well-recognised, fuel cells also have many advantages which makes continued research and development in the field highly worthwhile and viable. Key to their adoption is the identification of a niche market to utilise their advantages while overcoming their shortcomings with continuous research and development. This thesis aims to evaluate some of the stationary fuel cell applications and determine whether one could become the niche market as an entry point for fuel cells. This is achieved by economic evaluations of real and hypothetical applications. Results of the studies here imply that to decrease the total life cycle impacts of fuel cells to more acceptable levels, resource use in the manufacturing phase and recycling in decommissioning should be shown more attention. Results also present a picture showing that none of the applications investigated are economically feasible, given the current state of technology and energy prices. However, fuel cell-based combined cooling, heating and power systems for data centres show the potential to become the niche market that fuel cells need to grow. A further conclusion is that a broad market, longer stack lifetime, the possibility of selling electricity back to the grid and governmental subsidies are essential components of an environment in which fuel cells can permeate through the niche market to the mainstream markets.QC 20151210
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Khallat, Mohamed Ali. "A methodology for evaluating photovoltaic-fuel hybird energy systems." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/53626.
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A major issue encountered in the large scale use of Photovoltaic (PV) energy sources for the production of electricity is the variability of the resource itself. Extensive fluctuations of the PV generation may cause dynamic operational problems for an electric utility. In order to remedy this situation it is proposed that fuel cell power plants be operated in parallel with PV arrays. This hybrid operation will help to smooth out the fluctuating PV output. Because of its high ramping capability the fuel cell will be able to absorb such fluctuations.
An overall methodology is presented to evaluate the PV system in a large utility. This methodology has two parts-planning and operation. The aim of the planning study is to determine the capacity credit of a PV system based on the loss of load probability (LOLP). Long term SOLMET data is used to determine the nature of available insolation at a particular site. The expected value of hourly insolation is used in the planning study. The aim of the operation study is to validate the results of planning study in the shorter operational time frame, and determine the fuel cell requirements and associated operating cost savings for each penetration level of PV.
A technique to find the maximum penetration level of PV, without causing any economic penalty, is presented. It is found that the penetration level can be increased up to 15.62% of peak load by adding fuel cells to the system under consideration. The annual peak load for this system is taken as 6400 MW. It must be mentioned here that, similar evaluations for other systems may yield somewhat different results. This technique is general enough such that it can be used for other intermittent sources of generation as well.Ph. D.
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Jing, Junbo. "Vehicle Predictive Fuel-Optimal Control for Real-World Systems." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1534506777487814.
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Ang, Sheila Mae Constantino. "Model-based design and operation of fuel cell systems." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1344169/.
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Fuel cells are a promising technology for the production of electricity from hydrogen or other fuels with high efficiency and low emissions. They are suitable for stationary, transportation and portable applications. However, they are still more expensive than existing technologies and there are technical challenges that need to be overcome for their commercialisation. Therefore, accurate and efficient design methodologies for fuel cell systems design are becoming increasingly important. Modelling and optimisation present a great potential to inform fuel cell systems design, which often results in savings in design cycle time and cost, and better design and operation. The purpose of this thesis is to investigate the applicability of model-based design approaches to fuel cell systems design when applied to a single-cell fuel cell, then a fuel cell stack and, ultimately, a system-level fuel cell system, such as a microcogeneration plant. The development of mathematical models for a single-cell fuel cell, a stack and a microcogeneration system is presented in detail. The use of these models in model-based design is then illustrated. For instance, the effectiveness of a conventional humidification design is examined using the single-cell fuel cell model. The fuel cell stack model is used within a multi-objective optimisation framework to investigate how size trades for efficiency. Finally, the micro-cogeneration plant model is used to investigate the trade-off between fuel consumption and electrical power output, compare different micro-cogeneration operating strategies and examine the interaction between operating strategies and electricity network. Overall, when properly formulated and validated, modelling and optimisation are useful tools in fuel cell systems design as they provide means by which engineers can obtain valuable information about the behaviour of the system, make informed decisions, generate different design alternatives and identify good designs even before a prototype is fabricated.
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Bidoggia, Benoit. "Fuel cell and power converter systems : model and design." Thesis, Tours, 2009. http://www.theses.fr/2009TOUR4027/document.
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Les piles à combustible sont des dispositifs qui permettent de transformer directement l’énergie chimique potentielle d’un carburant en énergie électrique. Elle sont presque toujours couplées à un convertisseur de puissance et l’ensemble est ici appellé « système à pile à combustible ». Le comportement de ces systèmes, les interactions entre ses composants, ainsi que leurs réponses aux stimulations extérieures ont été analysés, étudiés et mesurés. A cet effet, un système à pile à combustible complet a été modélisé. Des critères de dimensionnement pour cas où ni la pile à combustible ni le convertisseur de puissance sont à priori connus ont été identifiés et un prototype a été dimensionné et réalisé. D’autres aspects corrélatifs intéressants ont également été développés et étudiés, comme le fonctionnement du convertisseur à la limite entre les modes de conduction continu et discontinu, ainsi que son contrôle à fréquence de commutation variable. Des résultats expérimentaux et de simulation pour le système et pour les différentes parties dont il est composé sont présentésFuel cells are devices in which a fuel’s chemical potential energy is directly converted into electrical energy. They are almost always coupled to a power converter and the ensemble is here called “fuel cell system.” The behaviour of such systems, the interactions between their components,and their responses to external stimulations have been analysed, studied and measured. For this purpose, a complete fuel cell system has been modelled. Sizing criteria for cases where neither the fuel cell nor the power converter are a priori known have been identified, and a prototype has been sized and built. Other interesting correlative aspects have also been developed and studied, like the operation of the power converter on the border between the discontinuousand continuous conduction modes, and its control with a variable switching frequency. Experimental and simulation results for the system and for the different parts that compose it are presented
Le celle a combustibile sono dei dispositivi in cui l’energia chimica potenziale di un combustibile è direttamente convertita in energia elettrica. Quasi sempre le celle a combustibile sono accoppiate a un convertitore di potenza e l’insieme è qui chiamato «sistema a celle a combustibile». Il comportamento di questi sistemi, le interazioni tra i diversi componenti, nonché le loro risposte a stimoli esterni sono stati analizzati, studiati e misurati.A tal fine, un sistema completo a celle a combustibile è stato modellizzato. Sono stati identificati dei criteri di dimensionamento per casi in cui né la cella a combustibile, né il convertitore sono noti a priori, e un prototipo è stato dimensionato e realizzato. Altri interessantiaspetti correlatisonostati sviluppatie studiati,comeil funzionamento del convertitore di potenza al limite fra modo di conduzione discontinuo e continuo, e il suo controllo a frequenza di commutazione variabile. Risultati sperimentali e di simulazione per il sistema e le diverse parti che lo compongono sono presentati
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DRAGO, DAVIDE. "The sulfur issue in Fuel Cell based cogenerative systems." Doctoral thesis, Politecnico di Torino, 2017. http://hdl.handle.net/11583/2676807.
Full textAbstract:
In a context in which climate changes due to the continuous and out of control use of fossil fuels are becoming always more significant, it is very important to try to foster energy conversion systems with a lower environmental impact such as FC-based cogenerative systems.
With the necessary precautions, this kind of systems can be feed with a wide range of fuels, from the most conventional, such as hydrogen and natural gas, to those produced from renewable sources, such as biogas or gasification gas. Unfortunately, most of these fuels contains traces of elements that result to be detrimental for FC-based systems operation.
Among the different damaging substances, in the present work, the focus has been addressed to sulfur and sulfur-based compounds. Referring to this type of contaminant, usually a distinction can be made between the “natural” sulfur that is usually intrinsically present in the fuel adopted, according to its origins and processing procedures, and the “artificial” sulfur that can be added to the fuel depending on the specific use to which it is addressed, such the odorisation of the Natural Gas (NG).
In the prosecution, some scenarios of management of the issues correlated to the presence of sulfur and sulfur-based components (especially H2S) will be presented as examples. For each of them, the current methods adopted in order to guarantee the correct and safe operation of these devices are described. In addition, where existing, some possible alternative solutions are supplied.
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Worley, John Wright. "A systems analysis of sweet sorghum harvest for a Piedmont ethanol industry." Diss., This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-07282008-135608/.
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Kim, Eun Hie, and Michael Nsiah-Gyimah. "The impact of fuel price volatility on transportation mode choice." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/53542.
Full textAbstract:
Thesis (M. Eng. in Logistics)--Massachusetts Institute of Technology, Engineering Systems Division, 2009.Includes bibliographical references (leaves 43-45).
In recent years, the price of oil has driven large fluctuations in the price of diesel fuel, which is an important cost component in freight logistics. This thesis explores the impact of fuel price volatility on supply chains by examining the sensitivity of decisions under various scenarios. Specifically, we analyze the transportation mode choice decision between truckload and intermodal (truck combined with rail) transportation using a model to calculate the total relevant cost, consisting of transportation cost and inventory holding cost. We use input from the North American operations for a global retail company regarding annual demand, product characteristics, load size, lead time, transportation rates, fuel surcharges, inventory policies and holding cost to perform sensitivity analysis of the mode choice decision to fuel price and the value density of the product. For several origin-destination pairs we identify the diesel price at which intermodal offers lower total cost than truckload as well as the magnitude of savings that can be achieved by switching modes. We then generalize the insights from this case by providing an equation to calculate the fuel price for this mode choice tradeoff.
by Eun Hie Kim [and] Michael Nsiah-Gyimah.
M.Eng.in Logistics
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Pierpoint, Lara Marie. "A decision analysis framework for the U.S. nuclear fuel cycle." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68512.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Engineering Systems Division, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 163-168).
If we are willing to pay a premium, we may be able to mitigate some of the long-lasting impacts of nuclear waste. Deciding how to navigate this tradeoff, between cost and waste, is a central challenge for stewards of nuclear power. It is made more difficult by uncertainties that characterize the global future of nuclear electricity generation. The recent increase in concern about climate change has prompted U.S. policymakers to back strategies favorable toward nuclear power, so much so that some experts see a "nuclear renaissance" on the horizon. Whether such a renaissance will come to pass, involving the construction of a vast new fleet of nuclear plants, is unclear - especially in light of the March 2011 nuclear accident at the Fukushima Daiichi reactors in Japan. Even more unclear is what should be done with the commercial U.S. nuclear waste, given an array of technical options and a large amount of uncertainty about how much waste will ultimately need to be managed. This study introduces a framework for analysis of strategies to evolve the nuclear fuel cycle which may be helpful in analyzing decision problems for similarly complex, long-lived technical infrastructure systems. The framework consists of a system dynamics simulation coupled with a decision analysis model. The system dynamics code is developed specifically for this study to be simple, fast-running, and also to echo the results of many previous nuclear fuel cycle simulations in demonstrating how various technical options impact important parameters (like uranium consumed, waste generated, etc.). Code results are benchmarked to more complex fuel cycle simulations for the parameters relevant to the decision space. The decision analysis model takes information from the simulation and makes it useful to policymakers, by allowing the explicit analysis of desirable decision pathways under uncertainty, and also considering tradeoffs among system goals. The framework is applied to three nuclear systems, the light-water reactor (LWR) once through fuel cycle, which represents the status quo, an advanced, traditional, plutonium-fed self sustaining fast reactor fuel cycle, and a fast reactor fuel cycle for which initial fast reactor cores are composed of enriched uranium rather than recycled LWR fuel. Fast reactors are highly likely to cost more than LWRs, but they can produce electricity from some of the elements that most plague the long-term management of a nuclear waste repository. A value function compares how these options fare under different scenarios, incorporating system-wide costs and the system waste burden as the two attributes in the function. The primary result is that the best strategy, under a strong preference for eliminating LWR spent nuclear fuel waste, consists of building a few traditional fast reactors now, and then building a full fleet more rapidly later in the century. This allows both for a significant amount of waste mitigation compared to an all-LWR fuel cycle, and for the costs associated with the more expensive fast reactor technology to be incurred primarily later in the century. On the other hand, if cost is the main consideration, the framework advises moving forward with the once-through LWR fuel cycle and avoiding fast reactors altogether, or at least until later in the century. These results are examined from a traditional decision analysis perspective, and then from one that departs somewhat from the assumption of a fully powerful decision maker. In reality, a government decision maker can only offer incentives to industry in order to induce a strategy change. Changing the decision model to reflect this reality causes the framework to more strongly advise moving forward with traditional fast reactors. This occurs because any single attempt at offering incentives to industry might be unsuccessful, and thus prevent a waste concerned government from achieving any significant mitigation. The most important contribution of the methodology is its ability to illuminate which parameters represent strong drivers of system decisions. Preferences across competing attributes are always important: in general, if decision maker preferences for reducing cost vs. waste were to shift significantly, the framework would show a change in the desirable decision strategy. Decision results are not very sensitive, on the other hand, to the rate of nuclear power growth or to the cost of fast reactor technology. A second contribution comes from the initial foray into studying a more complex decision maker perspective, and shows how a different view can complement results using the traditional decision analysis assumption of an "ideal" decision maker. Ultimately, the system dynamics/decision analysis framework presented here helps identify desirable pathways for complex system evolution, identifies factors that bear strongly on decisions and which are deserving of more study, and begins to show how strategy implementation can be considered within the framework in order to further improve decision-making.
by Lara Marie Pierpoint.
Ph.D.
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Kanteti, Madhavi, and Jordan T. Levine. "Risk sharing in contracts : the use of fuel surcharge programs." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68825.
Full textAbstract:
Thesis (M. Eng. in Logistics)--Massachusetts Institute of Technology, Engineering Systems Division, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 92-93).
Various industries employ risk sharing contracts to manage the risks and volatility associated with commodity prices, inaccurate customer demand forecasts, or unpredictable events. For example commodity futures that enable hedging, vendor buy-back programs, and insurance policies are examples of risk sharing contracts. The volatility in the price of fuel in the latter part of the twentieth century to the present has required the various parties involved in the trucking industry to employ risk-sharing contracts as an addendum to payment for services in the form of fuel surcharges. Fuel surcharges are effective in the sense that their structure transfers risk of fuel price volatility from carrier to shipper, and that industry participants typically understand the implications and reasoning behind the fuel surcharges. That said, there is no universal industry standard, and current fuel surcharge schedules remain based off of legacy diesel fuel prices in the range of $1.10-1.50 per gallon. Through mathematical analysis of a large shipper's annual costs, interviews with large shippers that have recently made transformations in their fuel surcharge schedules, a survey that gathered the thoughts and opinions of approximately one hundred motor carrier representatives, and multiple interviews with motor carrier representatives, the authors conclude that the fuel surcharge system can be improved for industry-wide benefit. Transition to a zero trigger point-based fuel surcharge schedule, the use of a carefully selected escalator, and the use of the national Department of Energy (DOE) retail price of diesel will prevent underbidding on lanes, increase transparency, reduce administration, and further increase the resilience of the United States truckload (TL) industry.
by Madhavi Kanteti and Jordan T. Levine.
M.Eng.in Logistics