Optimierung von Brennstoffzellen-Hybridfahrzeugen

The limited fossil fuel resources and the environmental concerns associated with burning those fossil fuels lie behind the increasing interest in hydrogen as a clean and sustainable alternative to fossil fuels, and in fuel cells as a clean converter of hydrogen into electrical energy especially in the transportation sector. Fuel cell hybrid vehicles (FCHVs) are characterized by the use of a fuel cell system (FCS) as the main power source and a battery, a supercapacitor or both as an energy storage system (ESS). Hybridizing the FCS with an ESS significantly improves the hydrogen economy, helps downsize the FCS, and resolves the issues related the long start-up time and slow dynamics of the FCS. The existence of multiple power sources in the powertrain gives rise to two important questions: How to coordinate the power contribution of the sources (i.e., power management strategy (PMS)), and how to size these sources in order to exploit the advantages of hybridization. The goal of this thesis is to develop a comprehensive framework for the optimization of PMS and size of FCHV powertrains. Depending on the type of ESS, three topologies are considered: fuel cell/ battery, fuel cell/ supercapacitor, and fuel cell/ battery/ supercapacitor. The PMS optimization is investigated on two levels; i.e., the vehicle level by simulation and the developed optimization algorithms are then validated on a small-scale test bench. When the driving cycle is known a priori, the off-line optimal PMS that globally minimizes the hydrogen consumption is calculated by two algorithms, namely, Dynamic Programming (DP) and Pontryagin’s Minimum Principle (PMP), and the two algorithms are compared. It has been found that PMP can be a superior approach for off-line optimization since it requires negligible computation resources without sacrificing the global optimality. The off-line optimal strategy is not real-time capable; hence, real-time strategies are designed and optimized while using the off-line optimal PMS as a benchmark. Special emphasize is put on the inclusion of multiple driving cycles, of different nature, in the optimization of the real-time PMS to increase its robustness. The sizing of the power sources of fuel cell/ battery and fuel cell/ supercapacitor hybrids considers hydrogen consumption and powertrain cost as two objectives and takes into account the drivability constraints such as top speed, gradeablity and acceleration time. The interesting designs (i.e., FCS size and ESS size), which represent the most efficient trade-off between the objectives, are then extracted and analyzed. The effect of battery aging on the optimal powertrain size is investigated by an Ampere-hour throughput model. It has been found that the battery aging leads to less efficient powertrain designs and the supercapacitor can become a more efficient option in comparison to batteries of poor lifetime.Die begrenzten fossilen Ressourcen und die Umweltsorgen, die mit der Verbrennung dieser fossilen Brennstoffe verbunden sind, stecken hinter dem steigenden Interesse am Wasserstoff als sauberer und nachhaltiger Alternative, und an Brennstoffzellen als sauberen Wandlern des Wasserstoffs in elektrische Energie, vor allem im Verkehrssektor. Ein Brennstoffzellen-Hybridfahrzeug (FCHV) verwendet ein Brennstoffzellensystem (FCS) als eine Hauptenergiequelle und eine Batterie, einen Superkondensator oder beide als Energiespeichersystem (ESS). Hybridisierung des FCS mit einem ESS verringert erheblich den Wasserstoffverbrauch, hilft das FCS zu verkleinern, und behebt das Problem der langen Anlaufzeit und der langsamen Dynamik des FCS. Die Existenz von mehreren Stromquellen im Antriebsstrang wirft zwei wichtige Fragen auf: Wie ist die Leistungsanforderung des Fahrzeugs zwischen den Quellen zu verteilen (d.h. Power-Management-Strategie (PMS)) und wie sind diese Quellen zu dimensionieren, um die Hybridisierung auszunutzen. Das Ziel dieser Arbeit ist es, einen umfassenden Rahmen für die Optimierung der PMS und Dimensionierung der Brennstoffzellen-basierten hybriden Antriebsstränge zu entwickeln. Abhängig von der Art des ESS werden drei Topologien berücksichtigt: Brennstoffzelle/ Batterie, Brennstoffzelle/ Superkondensator und Brennstoffzelle/ Batterie/ Superkondensator. Die PMS-Optimierung wird auf zwei Ebenen untersucht, und zwar die Fahrzeugebene durch Simulation und die Prüfstandsebene, worauf die entwickelten Optimierungsalgorithmen experimentell validiert werden. Wenn der Lastzyklus im Voraus bekannt ist, kann die offline optimale PMS, die den Wasserstoffverbrauch global minimiert, berechnet werden. Dazu werden die zwei Algorithmen, Dynamische Programmierung (DP) und Pontryagins Minimumprinzip (PMP), verglichen. Es wurde herausgefunden, dass das PMP ein überlegener Ansatz für die offline-Optimierung sein kann, da es viel weniger Rechenressourcen braucht, ohne die globale Optimalität zu opfern. Die offline optimale Strategie ist nicht echtzeitfähig, und deshalb werden Echtzeit-Strategien entworfen und optimiert, indem die offline optimale PMS als Maßstab verwendet wird. Beim Designen der echtzeitfähigen Strategien werden mehrere Fahrzyklen unterschiedlicher Natur beachtet, um die Robustheit der Strategien zu erhöhen. Die Dimensionierung der Stromquellen der Brennstoffzelle/ Batterie und Brennstoffzelle/ Superkondensator Hybriden betrachtet den Wasserstoffverbrauch und die Kosten des Antriebsstrangs als zwei Ziele. Es wird dabei die Fahrbarkeit, d.h. Höchstgeschwindigkeit, Steigfähigkeit und Beschleunigungszeit, berücksichtigt. Die interessanten Konfigurationen (FCS-Größe und ESS-Größe), die den effizientesten Kompromiss zwischen den Zielen darstellen, werden dann herausgefunden und analysiert. Die Wirkung der Batteriealterung auf die optimale Antriebsstrang-Größe wird durch ein Ampere-Stunden-Durchsatzmodell untersucht. Es wurde herausgefunden, dass die Batterie-Alterung weniger effiziente Antriebsstrang-Konfigurationen ergibt, und dass der Superkondensator eine effizientere Alternative zur Batterie sein kann, wenn er mit Batterien von schlechter Lebensdauer verglichen wird

Developments of electric cars and fuel cell hydrogen electric cars

The world continues to strive in the search for clean power sources to run the millions of different vehicles on the road on daily basis as they are the main contributors to toxic emissions releases from internal combustion engines to the atmosphere. These toxic emissions contribute to climate change and air pollution and impact negatively on people's health. Fuel cell devices are gradually replacing the internal combustion engines in the transport industry. Some notable challenges of the PEMFC technology are discussed in this paper. High costs, low durability and hydrogen storage problems are some of the major obstacles being examined in this investigation. The paper explores the latest advances in electric cars technology and their design specifications. The study also compares the characteristics and the technologies of the three types of electric cars now available in the market.interna

Power Management Optimization of an Experimental Fuel Cell/Battery/Supercapacitor Hybrid System

In this paper, an experimental fuel cell/battery/supercapacitor hybrid system is investigated in terms of modeling and power management design and optimization. The power management strategy is designed based on the role that should be played by each component of the hybrid power source. The supercapacitor is responsible for the peak power demands. The battery assists the supercapacitor in fulfilling the transient power demand by controlling its state-of-energy, whereas the fuel cell system, with its slow dynamics, controls the state-of-charge of the battery. The parameters of the power management strategy are optimized by a genetic algorithm and Pareto front analysis in a framework of multi-objective optimization, taking into account the hydrogen consumption, the battery loading and the acceleration performance. The optimization results are validated on a test bench composed of a fuel cell system (1.2 kW, 26 V), lithium polymer battery (30 Ah, 37 V), and a supercapacitor (167 F, 48 V)

Power Management Optimization of an Experimental Fuel Cell/Battery/Supercapacitor Hybrid System

In this paper, an experimental fuel cell/battery/supercapacitor hybrid system is investigated in terms of modeling and power management design and optimization. The power management strategy is designed based on the role that should be played by each component of the hybrid power source. The supercapacitor is responsible for the peak power demands. The battery assists the supercapacitor in fulfilling the transient power demand by controlling its state-of-energy, whereas the fuel cell system, with its slow dynamics, controls the state-of-charge of the battery. The parameters of the power management strategy are optimized by a genetic algorithm and Pareto front analysis in a framework of multi-objective optimization, taking into account the hydrogen consumption, the battery loading and the acceleration performance. The optimization results are validated on a test bench composed of a fuel cell system (1.2 kW, 26 V), lithium polymer battery (30 Ah, 37 V), and a supercapacitor (167 F, 48 V)