A Systemic Framework for Monitoring Energy Performance of Urban Railways
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A Systemic Framework for Monitoring Energy Performance of Urban Railways Roberto Palacín This thesis is presented for the Degree of Doctor of Philosophy School of Mechanical and Systems Engineering December 2016 ii ABSTRACT Global sustainability challenges are particularly acute in urban conurbations which house the majority of the world’s population and where most of the economic activity takes place. Mobility is at the core of this challenge as transport is one of the highest energy consuming and polluting sectors across the globe. Achieving a low environmental impact transport system fit for all is a clear objective. A modal shift to low energy but highly competitive transport modes is a key target. Urban railway systems have the environmental performance and mass transit capability to be the core provider of mobility in metropolitan areas bringing also other benefits e.g. connectivity, cohesion and social inclusivity. Nevertheless, in a very competitive context where all modes are improving their energy performance, it is crucial that urban rail systems enhance their energy conservation levels without jeopardising their service offer. There is a lack of consensus amongst stakeholders on how to assess energy performance of urban rail systems. This void has been extended to the academic literature, where the issue is largely missing. The overall purpose of this thesis is to contribute to energy conservation of urban rail systems by supporting the decision- making process leading to the deployment of interventions aimed at improving energy efficiency and optimising its usage. A three-phased methodological triangulation approach has been adopted to address three research questions derived from two research objectives. This research has investigated energy usage, interventions and interdependencies that are governed by the complexity of the socio-technical system that are urban railways. A holistic approach has been developed based on an adaptable systemic monitoring framework and associated methodology enabling i) a multilevel analysis of system energy performance using a set of twenty-two hierarchical indicators and four complementing parameters, ii) an appraisal of candidate energy optimisation interventions and iii) the monitoring of the results of implemented measures. To validate and illustrate its execution, the framework has been applied to five different urban rail systems to assess a total of eleven technical and operational interventions. This has resulted in observing up 3.4% or circa 4 GWh usage reduction at system level when considering the influence of the three technical interventions monitored and up to 4.8% or circa 6.6 GWh when the eight operational interventions are evaluated in conjunction. These outcomes have illustrated the universality of the framework and its adaptability to the particularities of each urban rail system. iii iv To Oliver and Anna, you can do it. v vi ACKNOWLEDGMENTS The contents of this thesis have been partly based on my research in the context of the CleanER-D and OSIRIS grants, both co-funded by the European Commission (Grant Contract No GA-2009-234338 and SCP1-GA-2011-284868 respectively). My gratitude goes to the funder and the many international collaborators I worked and engaged with. I also wish to acknowledge and credit my RAs involved in these grants Dr. Arturo Gonzalez, Mr. Paul Batty and Mr. Jonathan Powell for their contributions to the literature review and the fruitful discussions, which have resulted in three excellent manuscripts. I would like to extent my gratitude to Prof. Mark Robinson, my original supervisor, for giving me the opportunity to do this Doctorate and more importantly for his trust and support over the time we have known each other. Thank you for having faith in me all those years ago. I am extremely grateful to Prof. John Mangan, who agreed to be my second supervisor when I needed it the most. I will be forever indebted to him for his kindness and generosity, which goes beyond and above the expected. I have learned so much from you and I only wish I will be able to continue to do so in the future. None of the above would have mattered the slightest if it weren’t for my family. vii viii CONTENTS Abstract ....................................................................................................................... iii Acknowledgments ...................................................................................................... vii List of Figures ............................................................................................................. xii List of Tables ............................................................................................................. xiv Chapter 1-Introduction ................................................................................................ 1 1.1. Background to the Research .......................................................................... 1 1.2. The need for improving energy efficiency ...................................................... 3 1.3. Research purpose ........................................................................................... 5 1.3.1. Research context ....................................................................................... 6 1.3.2. Research objectives and questions .......................................................... 9 1.4. Contributions ................................................................................................. 11 1.5. Thesis structure ............................................................................................. 12 Chapter 2-Energy Aspects of Urban Railway Systems ............................................. 14 2.1. Urban rail systems characterisation .............................................................. 14 2.2. Energy use in urban rail systems .................................................................. 17 2.2.1. Traction energy consumption .................................................................. 18 2.2.2. Non-traction energy consumption ........................................................... 22 2.3. Identification, measurement and monitoring of energy usage ..................... 24 2.4. Performance and the use of indicators for urban rail systems ..................... 28 2.5. Chapter conclusions ..................................................................................... 30 Chapter 3-Research Methodology ............................................................................ 32 3.1. Research design premise ............................................................................. 32 3.2. Research philosophy .................................................................................... 33 3.3. Research methodology considerations ........................................................ 36 3.4. Research framework ..................................................................................... 41 3.5. Research design: Methodology and techniques structure ........................... 45 3.6. Chapter conclusions ..................................................................................... 49 Chapter 4-Strategies and technologies for management of regenerative braking ... 50 4.1. Introduction ................................................................................................... 50 4.2. Regenerative braking: Concept and strategies for deployment ................... 51 4.2.1. Basic considerations ............................................................................... 51 4.3. Strategies for deployment of regenerative braking ....................................... 51 4.4. Strategies for maximising exchange of regenerative energy between vehicles .................................................................................................................. 53 4.5. Energy storage systems for urban rail application ....................................... 55 4.5.1. Energy storage systems characterisation ............................................... 55 ix 4.6. Energy storage technologies for urban rail applications ............................... 57 4.6.1. Electrochemical double layer capacitors ................................................. 57 4.6.2. Flywheels .................................................................................................. 58 4.6.3. Batteries ................................................................................................... 59 4.6.4. Superconducting magnetic energy storage ............................................ 62 4.6.5. Comparison and assessment .................................................................. 62 4.7. On-board energy storage systems ................................................................ 66 4.7.1. Main characteristics of on-board applications ......................................... 66 4.7.2. Technologies for on-board storage systems ........................................... 68 4.7.3. State of the art assessment of systems for on-board application ............ 69 4.8. Stationary energy storage systems ............................................................... 75 4.8.1. Main characteristics of stationary applications ........................................ 75 4.8.2. Technologies for stationary storage ......................................................... 77 4.8.3. State of the art assessment of systems for stationary application ........... 77 4.9. Reversible substations .................................................................................