[en] Railway is an essential transportation mode in nowadays society, both for passengers and goods. Considering that the relation between the carried passenger activity and the derived pollutant emissions is lower than in road transport, railway becomes an essential stakeholder in the path towards transport decarbonization. During the last decades, a significant effort to electrify railway lines has been carried out globally. However, due to its high cost, electrification is not always cost-efficient. Consequently, 65% of rail tracks are not electrified yet, and diesel still accounts for 53% of the global railway sector energy use. This demonstrates the importance of searching for cleaner alternatives also in the railway sector. Recent techno-economic developments have pushed the use of greener technologies such as batteries and fuel cells in various transport applications, including railway vehicles. Due to their technical limitations, hybrid architectures such as the diesel-battery or the fuel cellbattery become the most promising options, or even the only feasible ones, in many cases. This hybridization involves additional complexity compared to traditional architectures. In essence, the main challenge consists of obtaining a cost-efficient solution compared to conventional vehicles, which will also enable a cleaner transportation. With the aim of obtaining that cost-efficient solution, this Ph.D. Thesis focuses on the design of the powertrain of railway vehicles. Important features to be considered during the powertrain design include the selection of the technologies to be integrated into the powertrain, the size of the powertrain elements, and the energy management strategy. Traditionally, these features are defined ad-hoc for a specific context (i.e., for a particular driving cycle or economic framework), but this is a time-consuming process, and the replicability of the conclusions is limited. Therefore, evaluating the impact that the different features of the specific context have on the optimal powertrain design can help simplify the efforts of the design approach. In order to overcome all these challenges, this Ph.D. Thesis proposes and implements a holistic design methodology to achieve a cost-optimal integration of fuel cell and battery systems in railway vehicles. The holistic design methodology is based on a complete analysis of the Life Cycle Cost, which is composed of several steps. Firstly, the cost of integrating different powertrain sizes, battery technologies and energy management strategies is compared. Secondly, the obtained conclusions are evaluated in different frameworks, including multiple railway routes and economic contexts. For the development of this analysis, a power flow-based simulation model is set. This model is based on the Itiner tool previously developed by CAF I+D, and it is fed with the data provided by CAF Power & Automation. This will allow using realistic vehicle and route data to develop the mentioned Life Cycle Cost analysis. Moreover, within the development of this analysis, this Ph.D. Thesis also proposes several innovative energy management strategies and a novel chemistry-dependent battery lifetime estimation model. Once the holistic design methodology is explained in detail, the methodology and the whole Life Cycle Cost analysis are implemented in two case studies. Each of the case studies of this Ph.D. Thesis is based on one of the railway vehicle topologies mentioned above: (1) the diesel-battery hybrid topology, and (2) the fuel cell-battery hybrid topology. The development of the two case studies will provide valuable conclusions for the design of railway vehicle powertrains that integrate battery and fuel cell systems. These conclusions are claimed to be especially helpful for railway manufacturers to make decisions regarding the powertrain design of hybrid diesel-battery or fuel-cell battery vehicles.

[eu] Trenbidea funtsezko garraio mota da gaur egungo gizartean, bai pertsonen mugimendurako zein merkataritzarako. Errepideko garraioarekin konparatuz, trenbideek eragiten duten kutsadura bidaiari bakoitzeko baxuagoa da. Beraz, trenbidea funtsezko elementua bihurtzen da garraioaren dekarbonizazio bidean. Azken hamarkadetan trenbideak elektrifikatzeko ahalegin garrantzitsua egin da mundu mailan. Hala ere, bere kostu altuaren ondorioz, elektrifikazioa ez da beti errentagarria. Ondorioz, gaur egun trenbideen %65-a ez dago elektrifikatuta oraindik, eta sektorearen oinarrizko energia erabileraren %53-a dieselaren bidez egiten da. Honek erakusten du trenbidearen sektorean ere alternatiba garbiagoak bilatu behar direla. Azken urteetako garapen tekno-ekonomikoen eraginez, hainbat garraio aplikazioetan (trenbide ibilgailuetan ere) bateriak eta erregai pilak bezalako teknologia garbien integrazioa bultzatu da. Teknologia hauen muga teknikoak direla eta, diesel-bateria edo erregai pila-bateria bezalako arkitektura hibridoak aukerarik egokienak, edo aukera bakarrak, dira kasu askotan. Hibridazioak konplexutasun gehigarria eragiten du arkitektura tradizionalen aldean. Funtsean, erronka nagusiena aukera tradizionalekin konparatuz irtenbide errentagarri bat lortzea da, zeinak garraio garbiago baten bidea irekitzea ahalbidetuko luke. Irtenbide eraginkor hori lortzeko helburuarekin, Tesi Doktoral hau trenbide ibilgailuen potentzia-trenaren diseinuan zentratzen da. Diseinu honetan kontuan hartu beharreko aspektu garrantzitsuak honakoak dira: potentzia-trenean integratuko diren teknologien hautaketa, potentzia-treneko elementuen tamaina, eta energia kudeaketarako estrategia. Tradizionalki, ezaugarri hauek ad-hoc definitzen dira testuinguru jakin baterako (hau da, ibilibide edo tesituinguru ekonomiko jakin baterako), baina hau prozesu oso luzea da, eta lortzen diren ondorioen erreplikagarritasuna mugatua da. Hori dela eta, testuinguru espezifikoaren ezaugarriek potentzia trenaren diseinuan duten inpaktua ebaluatzeak diseinu prozesuan jarri beharreko esfortzua gutxitzen lagundu dezake. Erronka guzti hauek gainditzeko, Tesi Doktoral honek tren ibilgailuetan erregai pila eta bateria sistemen integrazio errentagarria lortzeko diseinu metodo holistiko bat proposatu eta inplementatzen du. Diseinu holistikoaren metodologia "Life Cycle Cost" edo bizitza-ziklo kostuaren analisi integral batean oinarritzen da, zeina urrats desberdinez osatzen den. Lehenik, potentziatrenaren elementuen tamaina desberdinek, bateria teknologia desberdinek, eta energia kudeaketa estrategia desberdinek duten kostua alderatzen da. Ondoren, lortutako ondorioak hainbat kontextuetan ebaluatzen dira, besteak beste, hainbat ibilbide edo testuinguru ekonomikoetan. Analisi hau garatzeko, potentzia fluxuetan oinarritutako simulazio eredu bat ezarri da. Eredu hau CAF I+D enpresak lehendik garatutako Itiner simulazio tresnan oinarritzen da, eta CAF Power & Automation enpresak emandako datuekin elikatu da. Honek bizitza-ziklo kostuaren analisia garatzerako orduan ibilgailu eta ibilbide errealistak erabiltzea ahalbidetu du. Gainera, aipatutako analisiaren garapenan, Tesi Doktoral honek energia kudeaketarako hainbat estrategia proposatzen ditu, eta baita baterien bizitza estimatzeko modelo berritzaile bat ere, zeina hainbat kimiketarako parametrizatu den. Behin diseinu holistikoaren metodologia xehetasunez azalduta, metodologia eta bizitzaziklo kostuaren analisi osoa ikerketa-kasu bietan aplikatzen da. Tesi Doktoral honen ikerketa-kasu bakoitza lehen aiptautako trenbide ibilgailu topologia batean oinarritzen da: (1) diesel-bateria arkitektura hibridoa, eta (2) erregai pila-bateria arkitektura hibridoa. Bi ikerketa-kasuen garapenak bateria eta erregai pilak integratzen dituzten trenbide ibilgailuen diseinurako ondorio baliagarriak emango ditu. Ondorio hauek lagungarriak izan daitezke trenbide ibilgailuen fabrikatzaileentzat, bereziki diesel-bateria edo erregai pila-bateria ibilgailuen diseinurako erabakiak hartzerako orduan.