Effizienz und Performance elektrischer und hybridisierter Fahrzeugantriebe im Vergleich

Im Zuge dieser Arbeit wurden die Effizienz und Performance elektrischer und hybridisierter Fahrzeuge untersucht, um ihr Potential bzw. ihre Vor- und Nachteile für zukünftige Verkehrssysteme aufzuzeigen. Dazu wurden jeweils während der Winter- und Sommermonate 2014/2015 der Realverbrauch verschiedener elektrifizierter Fahrzeugkonzepte unter realitätsnahen Bedingungen und in alltäglichen Fahrszenarien, während dynamischen und auch stationären Fahrprofilen in Wien und Umgebung bestimmt. Auch der Betrieb und die Nutzung der Fahrzeuge selbst und ihre energetisch relevanten Komponenten und Funktionen wurden hinsichtlich Performance qualitativ und nach Möglichkeit quantitativ betrachtet. Die ermittelten real-world Daten sollten, neben der Verwendung in diesem Werk, außerdem auch als Referenzdaten für zukünftige Arbeiten, Gegenüberstellungen und Simulationen dienen.In the course of this thesis, the efficiency and performance of electric and hybridized vehicles were examined in order to show their potential and their advantages and disadvantages for future transportation systems. For this purpose, during the winter and summer months of 2014/2015 the real-world consumption of various electrified vehicle concepts was measured under realistic conditions and in everyday driving scenarios on-road while driving both dynamic as well as steady speed profiles in Vienna and its surroundings. Also, the operation and use of the vehicles themselves and their energy-relevant components and functions were considered in terms of performance, both qualitatively and as far as possible quantitatively. The resulting real-world data should, in addition to its use in this thesis, also serve as reference data for future works, comparisons and simulations

Experimental and computational studies on combustion of surrogate and alternative fuel components at atmospheric and elevated pressures

Mit dem Ziel den Wissensstand der Verbrennungswissenschaft und -technik zu erweitern, werden im Zuge dieser Dissertation experimentelle und rechnerische Untersuchungen ausgeführt. Der Fokus der Betrachtungen liegt auf der Verbrennung bei erhöhten Drücken und beinhaltet Messungen und numerische Berechnungen fundamentaler Grenzphänomene der Flammbarkeit und kritischer Bedingungen. Die Entwicklung sowohl der experimentellen als auch der computergestützten Methodologie werden zusammen mit der Erweiterung der Kapazitäten der experimentellen Anlage hierin protokolliert. Ergebnisse vorangehender und zusätzlicher Untersuchungen bei atmosphärischem Druck werden angeführt und diskutiert, um im Bedarfsfall die Betrachtungen im Hauptaugenmerk zu ergänzen und die entwickelten rechnerischen Methoden und Modelle auf ihre Zuverlässigkeit und Effizienz zu prüfen. Die experimentelle Anlage, welche während der Untersuchungen angewendet und für die Simulationen modelliert wird, ist der Gegenstrombrenner in verschiedenen Konfigurationen für gasförmige und flüssige Brennstoffe. Die Messungen wurden in UC San Diego's Verbrennungslabor unternommen, in welchem sowohl ein modulares Brennersystem für Experimente bei atmosphärischem Druck als auch die einzigartige High Pressure Combustion Experimental Facility (HPCEF) zur Untersuchung von Verbrennungsprozessen und Flammen bei erhöhten Drücken zur Verfügung stehen. Bei atmosphärischem Druck wurden Auslöschungs- und Selbstzündungsexperimente zur Ermittlung der Auslöschungsströmungsgeschwindigkeiten und Selbstentzündungstemperaturen bei gasförmigen, vorverdampft flüssigen und angestaut kondensierten Brennstoffen durchgeführt, während am HPCEF ausschließlich kondensiert flüssige Brennstoffe untersucht wurden, um deren Selbstentzündungstemperaturen unter variierenden Randbedingungen bei Drücken von 5 bar bis zu 25 bar zu bestimmen. Die während der Versuche untersuchten Brennstoffe sind die gasförmigen Alternativkraftstoffkomponenten Dimethyl Ether (DME) und Propan und die flüssigen Referenzkraftstoffe und Surrogatkomponenten n-Heptan, n-Decan, and n-Dodecan. Graphische Darstellungen der experimentellen Daten und numerischen Berechnungen, zusammen mit den vorherrschenden Randbedingungen, befinden sich in den jeweiligen Kapiteln, während die individuellen Datenpunkte der Messungen, inklusive ihrer dazugehörigen Standardfehler, zur Referenz in tabellarischer Form im Anhang angeführt sind. Für die Berechnungen und computergestützten Simulationen dieser Arbeit kam das open source Software Toolkit Cantera zum Einsatz. Während sein Löser, welcher in der Lage ist thermodynamische, chemische und transporttechnische Phänomene zu lösen, um Strömungsprobleme mit chemischen Reaktionen und Flammen zu simulieren, unverändert verwendet wurde, wurden die Basisimplementierung und das Modell der Gegenstromkonfiguration angepasst und signifikant erweitert, um den Anforderungen der Untersuchungen dieser Arbeit gerecht zu werden. Als Resultat entstand ein Python Modul namens "UCSDComLab", welches durch die Implementierung zahlreicher Objekte und Funktionen zur Modellierung, Simulation und Evaluierung der Experimente, die im Zuge dieser Dissertation durchgeführt wurden, eine Schnittstelle zu Cantera bietet, um die Berechnungen und nummerischen Prozesse zu erleichtern und zu beschleunigen. Für die Bereitstellung der benötigten physikalischen und reaktionskinetischen Parameter der auftretenden Stoffe, welche zur Simulation der Systeme und Prozesse notwendig sind, wurden verschiedene vollständige, vereinfachte und spezialisierte Versionen des San Diego und des PoliMi Mechanismus eingesetzt.Experimental and computational investigations are carried out with the goal to expand the body of knowledge of combustion science and engineering. The dissertation's focus is set on combustion at elevated pressures and encompasses measurements and numerical calculations of fundamental limit phenomena and critical conditions. Development of the methodology and computational framework, as well as the expansion of capabilities of the experimental setup are documented herein. Results of preliminary and additional studies at atmospheric pressure are given and discussed to complement the key investigations where necessary, and to test the developed computational methods and models for their reliability and efficiency. The experimental device used for the investigations and modeled for the simulations is the counterflow burner in various configuration for gaseous and liquid fuels. The measurements were taken at UC San Diego's Combustion Laboratory where a modular burner for experiments at atmospheric pressure as well as the unique High Pressure Combustion Experimental Facility (HPCEF) for investigations of combustion processes and flames at elevated pressures are housed. At atmospheric pressure, extinction and autoignition experiments to measure extinction strain rates and autoignition temperatures of gaseous, prevaporized liquid and pools of condensed fuels were conducted, while at the HPCEF, exclusively condensed liquid fuels were studied to determine autoignition temperatures under varying boundary conditions at pressures from 5 bar up to 25 bar. The tested fuels for the investigations were the gaseous alternative fuel components dimethyl ether (DME) and propane, and the liquid primary reference fuel (PRF) and surrogate components n-heptane, n-decane, and n-dodecane. Graphical representations of the experimental data and numerical calculations including the imposed boundary conditions are given in the respective chapters, while the individual data points of the measurements together with their standard errors are given in tabulated form in the appendix for reference. For the computations and simulations of this thesis, the open source software toolkit Cantera was used. While its solver, capable of handling thermodynamic, chemical kinetic, and transport phenomena to numerically solve chemically reacting flow problems and simulate flames, was left unmodified, the basic implementation and model of the counterflow configuration was adapted and vastly expanded to fit the needs of the investigations presented in this thesis. Eventually, a Python module interfacing with Cantera named "UCSDComLab" was developed to facilitate and streamline the computations and numerical processes by implementing several objects and functions to model, simulate, and evaluate experiments conducted in the course of this dissertation. To provide the required property and reaction data for all the relevant species in the simulated systems and processes, various complete, reduced, and specialized versions of the San Diego and PoliMi Mechanisms were used

Agrivoltaics, Opportunities for Hydrogen Generation, and Market Developments

To achieve deep decarbonization, renewable energy generation must be substantially increased. The technologies with the lowest levelized cost of electricity (LCOE) are land-based photovoltaics (PVs) and wind energy. Agri-PVs offer the potential for dual land use, combining energy generation with agricultural activities. However, the costs of agri-PVs are higher than those of ground-mounted PV. To enhance the competitiveness of agri-PV, we investigate the synergies between agri-PVs and hydrogen electrolysis through process simulation. Additionally, we analyse current technological developments in agri-PVs based on a market analysis of start-up companies. Our results indicate that the levelized cost of hydrogen (LCOH) can be comparable for agri-PVs and ground-mounted PVs due to the somewhat smoother electricity generation for the same installed capacity. The market analysis reveals the emergence of a technology ecosystem that integrates agri-PVs with next-generation agricultural technologies, such as sensors, robotics, and artificial intelligence (AI) agents, along with localized electricity generation forecasting. The integrated agri-PV and hydrogen generation system has significant global scaling potential for renewable energy generation. Furthermore, it positively impacts local economies and energy resilience, may reduce water scarcity in agriculture, and leverages advancements in AI, robotics, PV, and hydrogen generation technologies

Wind–Photovoltaic–Electrolyzer-Underground Hydrogen Storage System for Cost-Effective Seasonal Energy Storage

Photovoltaic (PV) and wind energy generation result in low greenhouse gas footprints and can supply electricity to the grid or generate hydrogen for various applications, including seasonal energy storage. Designing integrated wind–PV–electrolyzer underground hydrogen storage (UHS) projects is complex due to the interactions between components. Additionally, the capacities of PV and wind relative to the electrolyzer capacity and fluctuating electricity prices must be considered in the project design. To address these challenges, process modelling was applied using cost components and parameters from a project in Austria. The hydrogen storage part was derived from an Austrian hydrocarbon gas field considered for UHS. The results highlight the impact of the renewable energy source (RES) sizing relative to the electrolyzer capacity, the influence of different wind-to-PV ratios, and the benefits of selling electricity and hydrogen. For the case study, the levelized cost of hydrogen (LCOH) is EUR 6.26/kg for a RES-to-electrolyzer capacity ratio of 0.88. Oversizing reduces the LCOH to 2.61 €/kg when including electricity sales revenues, or EUR 4.40/kg when excluding them. Introducing annually fluctuating electricity prices linked to RES generation results in an optimal RES-to-electrolyzer capacity ratio. The RES-to-electrolyzer capacity can be dynamically adjusted in response to market developments. UHS provides seasonal energy storage in areas with mismatches between RES production and consumption. The main cost components are compression, gas conditioning, wells, and cushion gas. For the Austrian project, the levelized cost of underground hydrogen storage (LCHS) is 0.80 €/kg, with facilities contributing EUR 0.33/kg, wells EUR 0.09/kg, cushion gas EUR 0.23/kg, and OPEX EUR 0.16/kg. Overall, the analysis demonstrates the feasibility of integrated RES–hydrogen generation-seasonal energy storage projects in regions like Austria, with systems that can be dynamically adjusted to market conditions

Experimental and computational investigation of the influence of stoichiometric mixture fraction on structure and extinction of laminar, nonpremixed dimethyl ether flames

Experimental and computational investigation is carried out to elucidate the influence of stoichiometric mixture fraction, ξst, on the structure and critical conditions of extinction of nonpremixed dimethyl ether (DME) flames. The stoichiometric mixture fraction represents the location of a thin reaction zone in terms of a conserved scalar quantity. The counterflow configuration is employed, wherein two reactant streams flow towards a stagnation plane. One stream is made up of DME and nitrogen (N2) and the other stream is oxygen and N2. Previous studies have shown that critical conditions of extinction depend on ξst and the adiabatic temperature Tst. Therefore, the present investigation is carried out with the composition of the reactants in the counterflowing streams so chosen that the adiabatic temperature is the same for different values of ξst. The strain rate at extinction, aq, is measured for values of ξst up to 0.8. Computations are performed using detailed kinetic mechanisms and critical conditions of extinction and flame structures are predicted. The measurements and predictions show that, with increasing ξst, the strain rate at extinction first decreases and then increases. The predictions agree with measurements for ξst0.4, but significant deviations between measurements and predictions are observed at higher values of ξst. The scalar dissipation rate at extinction, χst,q is calculated using measured and predicted values of aq. With increasing ξst, the measured and predicted values of χst,q first increase and then decrease. It is noteworthy that changes in values of χst,q with ξst for dimethyl ether flames are similar to those for methane flames, while the changes in values of aq with ξst are remarkably different. Flame structures are predicted and they are found to be qualitatively similar to those for hydrocarbon fuels.</p