Results 1 - 10 of 92
Results 1 - 10 of 92. Search took: 0.026 seconds
|Sort by: date | relevance|
[en] Against the background of the long-term goals of the "Energiewende" and the German ratification of the Paris climate protection agreement, both the substitution of fossil fuels like natural gas by renewable energies as well as an increase in energy efficiency in the energy system are indispensable. This requires a radical transformation of the energy system, including the gas system, with associated risks for the actors involved. Political and gas industry decision makers therefore need information on the expected future demand for gas in the German energy mix to plan adequately the expansion of the capital-intensive gas transport infrastructure. These investments often have payback periods of up to several decades. In practice, expansion planning today is carried out regularly with special consideration of import dependency and supply security in network development plans of the responsible transmission system operators. The assumed development of gas demand in the 2016 network development plan, however, does not take into account the objectives of energy system transformation. This thesis develops a methodology to include the “Energiewende” objectives defined well beyond these ten years by 2050 in an assessment of the German gas transport system. Based on a detailed analysis of the current situation of the gas transport system, a scenario analysis is carried out in order to obtain plausible gas demand developments by 2050. From these, relevant grid utilization cases for the gas transport network are derived and investigated using the highly flexible GASOPT load flow model developed within the framework of this work. The suitability of GASOPT for the load flow calculation is demonstrated qualitatively by a back testing calculation of the peak load situation 2015 and quantitatively by a subsequent verification. The results of this thesis show that the gas transport network is only slightly utilized in the long term if the goals of the “Energiewende” are achieved due to a reduction in demand of more than 50 %. The compensation of several failing import routes, e.g. in Eastern Europe or even completely depleted natural gas storage facilities with simultaneous full load operation of gas-fired power plants is technically possible. The full substitution of fossil natural gas by methane produced climate-neutrally using "power-to-gas" is also manageable from the grid side. The long-term economic efficiency of grid sections with low capacity utilization and their rededication to alternative energy sources such as hydrogen can be examined in view of the significant reduction in gas transport demand. Furthermore, the analysis of consequences for the actors involved in the gas transport system shows that the business model of operators of large underground storage facilities in particular will be endangered, as import capacities exceed the required gas withdrawals in the future.
[en] In the course of the ongoing Energy Transition in Germany and Europe, the upcoming trend of decentralized generation leads to a new paradigm: Energy is more and more provided by a huge number of distributed energy resources instead of centralized generation. The share of cogeneration and Power-to-Heat solutions is growing. In combination with temporary electricity oversupply caused by a massive introduction of wind and photovoltaics this leads to a stronger sector coupling, especially regarding heat and power. Electric and thermal storage devices provide additional flexibility at central and decentral level that can be used to support the integration of renewables into the energy system. Whilst decentralization is the dominating trend in power and heat generation, on European level electricity market coupling is evolving leading to one single electricity market in Europe. These two contrary-appearing effects form the main playing field for this thesis: A Fundamental Electricity Market Model is developed, which allows for the simulation of a decentral oriented, but pan-European electricity market. With the developed model a co-simulation of centralized and decentralized generation is possible, considering the individual micro-economic objectives of the different market participants. A new decomposition approach derived from the concept of Lagrangian Relaxation forms the methodical core of the model. Beneath the coordination of the local load coverage within the different market areas, for the first time in parallel the international electricity exchanges are coordinated with Lagrangian Multipliers. This allows for an individual representation of thousands of generation units on central and decentral level, since the system overspanning optimization problem is decomposed into smaller sub-problems and a coordinator-problem. The model is validated against historic real data. A special attention is paid to the simulated electricity prices, the generation patterns of power plants and the results of the international electricity exchange. The correlation of realized and simulated electricity prices is about 90%. The ability of the model to simulate centralized generation in combination with a large amount of decentral energy resources on Prosumer level is demonstrated with scenario simulations for the year 2025. The simulations show that an investment in central Power-to-Heat facilities located at conventional CHP units to decrease (thermal) must-run generation dominates the decentral provision of flexibilities at Prosumer level regarding economic costs and the reduction of CO emissions.
[de]Der im Zuge der fortschreitenden Energiewende vorliegende Trend zu einer kleinteiligen Energieversorgung führt dazu, dass Energie immer weniger durch konventionelle Großkraftwerke, sondern vermehrt durch eine Vielzahl verteilter Energiewandlungseinheiten bereitgestellt wird. Ein zunehmender Einsatz von Kraft-Wärme-Kopplung und elektrischen Wärmeerzeugern führt in Kombination mit einem temporären Überangebot von Elektrizität aus Erneuerbaren Energien auf zentraler und dezentraler Ebene außerdem zu einer stärkeren Kopplung der Energieträger Strom und Wärme. Thermische und elektrische Speicher können in Kombination mit diesen Strom- und Wärmeerzeugern dazu genutzt werden, dem Strommarkt Flexibilität bereitzustellen. Während auf der Erzeugungsseite der Trend zur Kleinteiligkeit dominiert, schreitet auf europäischer Ebene die Ausweitung des internationalen Stromhandels kontinuierlich voran. Diese beiden gegensätzlich erscheinenden Trends bilden das zentrale Spannungsfeld dieser Arbeit. Es wird ein fundamentales Strommarktmodell entwickelt, welches die Simulation eines dezentral geprägten, jedoch europaweit verbundenen Strommarktes ermöglicht. Das entwickelte Modell ermöglicht die detaillierte Abbildung einer Vielzahl von zentralen und dezentralen Erzeugungsanlagen unter Berücksichtigung deren individueller mikroökonomischer Zielfunktionen im internationalen Strommarkt. Den methodischen Kern bildet ein neuartiges Dekompositionsverfahren in enger Anlehnung an die Lagrange Relaxation. Neben der Koordination der lokalen Lastdeckungsaufgabe innerhalb eines Marktgebietes wird erstmals auch die internationale Marktkopplung und mithin die Bestimmung der Austauschleistungen im internationalen Stromhandel in den iterativen Lagrange Koordinationsprozess integriert. Dies ermöglicht die individuelle Abbildung einer sehr großen Anzahl verschiedenster Energiewandlungseinheiten. Das entwickelte Modell wird anhand realer Daten validiert. Dabei liegt der Fokus der Bewertung auf den simulierten Strompreisen, dem Einspeiseverhalten der Kraftwerke und den Ergebnissen des internationalen Stromhandels. Die Korrelation zwischen realen Day-Ahead Spotpreisen und simulierten Strompreisen beträgt ca. 90%. Die Fähigkeit des Modells zur gleichzeitigen Abbildung einer großen Anzahl Prosumer und des zentralen Kraftwerksparks wird anhand von Szenariorechnungen für das Jahr 2025 demonstriert. Diese belegen, dass zentrale Power-to-Heat Lösungen zur Flexibilisierung des zentralen Kraftwerksparks (Reduzierung des sogenannten „Must-Run Sockels“) CO-Einsparungen zu wesentlich geringeren volkswirtschaftlichen Kosten ermöglichen als die dezentrale Bereitstellung von Flexibilitäten im Haushaltssektor.
[en] Lithium-ion batteries are widely used in many applications due to their high energy and power density. However, an important factor here is also the lifetime. During operation there is a loss of capacity as well as an increase of internal resistance. The aim of this work is the identification and quantification of the degradation processes under calendar and cyclical aging and the effect of the electrode microstructure on the ageing behaviour.
[de]Lithium-Ionen Batterien sind aufgrund ihrer hohen Energie- und Leistungsdichte in vielen Anwendungen weit verbreitet. Ein wichtiger Faktor ist hierbei aber auch die Lebensdauer. So kommt es während des Betriebs sowohl zu einem Kapazitätsverlust, als auch zu einem Anstieg des Innenwiderstandes. Ziel der Arbeit ist die Identifikation und Quantifizierung der Degradationsanteile bei kalendarischer und zyklischer Belastung und die Auswirkung der Elektrodenmikrostruktur auf das Alterungsverhalten.
[en] With the increasing participation of renewable energy sources in our energy matrix and the great concern of organizations with energy management, the technical and financial opportunities to reduce energy costs, to increase the competitiveness of organizations, and to promote actions that reduce environmental impacts in the processes involved are increasingly evident. Several aspects are relevant. Among them, it is possible to identify in Brazil a low adherence to the use of new technologies mainly focused on improving energy efficiency, great potential for the expansion of renewable energies, and a notorious technical and financial feasibility for projects developed in the areas of energy and energy efficiency. In this work the current study of the main energy sources is presented, emphasizing the renewable ones and the energy efficiency actions, showing a general scenario of the actions developed by public and private initiatives, along with the other actors involved, whose objective is to disseminate the opportunities that permeate the energy and energy efficiency market in Brazil, as well as to guarantee the benefits that the adoption of these new technologies can bring to the economy, society, environment and development of the country. The results determined in the study, highlight Brazil as one of the cleanest energy matrix in the world, demonstrating an expressive participation of renewable energies, with approximately 43%, but reveal timid initiatives aimed at energy efficiency actions and to improving its performance. (author)
[en] The development of laser technologies and techniques to cool atoms and molecules has opened new possibilities to manipulate and control quantum matter by tailored external fields. In particular, quantum rotors subject to external fields have enjoyed considerable interest of both the physics and chemistry communities. Furthermore, experimental as well as theoretical investigations of the dynamics of driven quantum rotors have provided insight into fundamental aspects of quantum dynamics, such as revival structures, quantum-classical correspondence, and quantum chaos. Herein, we investigate, mostly analytically, the spectral properties as well as the dynamics of a two-dimensional (planar) linear quantum rotor exposed to external orienting and aligning fields. Supplemented by numerical computations that reach beyond what is achievable analytically, we paint quite a complete picture of the physics of the driven planar rotor. The conditionally quasi-exact solvability of the corresponding eigenproblem, termed the generalized planar pendulum, enables obtaining the lower part of the generalized pendulum’s spectrum analytically. However, this is only possible under certain conditions imposed on the parameters that characterize the strengths of orienting and aligning interactions. By making use of Lie-algebraic and group theoretical methods, we calculated all algebraically obtainable eigenvalues and eigenfunctions of the generalized pendulum’s eigenproblem based on the solutions that had been obtained previously via supersymmetric quantum mechanics. Furthermore, an analogous analysis of the hyperbolic counterpart of the generalized planar pendulum, the Razavy problem, confirmed that the normal and hyperbolic pendula are anti-isospectral, but only in the analytic part of their spectra. Moreover, our analysis of the generalized pendulum problem revealed a relationship between its conditional quasi-exact solvability and the topology of eigenenergy surfaces: the intersections (genuine and avoided) of the eigenenergy surfaces spanned by the dimensionless aligning and orienting interaction parameters arise for certain ratios of these parameters. These ratios coincide with those for which analytic solutions to the generalized pendulum eigenproblem exist. Building on our knowledge of the analytic stationary states and aided by our numerical calculations, we investigated the dynamics that arises from the interaction of a rigid rotor with aligning and orienting fields that have particular temporal shapes: an ultra-short pulse (-kick) and rapidly switched-off or switched-on pulses. For these types of pulses, we found analytic expressions for the resulting wavefunctions, kinetic energies, and the evolution of orientation and alignment. In addition, the revival structure of the resulting wavepackets and the quantum-classical correspondence is captured by the space-time dependence of the probability density known as quantum carpets. In the sudden limit, i.e., when the duration of the pulse is much shorter than the rotational period of the rotor, a combination of orienting and aligning interactions produces a unique pattern in post- pulse populations of the rotational states, captured by diagrams termed population quilts. Accordingly, for each of the orienting, aligning and combined interactions, the time- evolutions of the orientation and alignment differ considerably. The analysis conducted in the case of rapidly switched fields revealed a significant influence of the spectral properties and eigensurface topology of the generalized pendulum on the post-switch populations as well as the time-evolution of the expectation values and the corresponding revival structure.
[en] We present extensions and new developments of the in-medium no-core shell model (IMNCSM), which is a novel ab initio many-method that merges the multi-reference in-medium similarity renormalization group (MR-IM-SRG) with the no-core shell model (NCSM) - two complementary and successful ab initio many-body methods. Within the IM-NCSM framework, the MR-IM-SRG employs a correlated NCSM reference state and unitarily transforms observables such that the reference state is decoupled. Consequently, the model-space convergence of a subsequent NCSM calculation is substantially accelerated - demonstrating the power of the IM-SRG decoupling scheme - and the IM-NCSM can treat nuclei that are out of reach for traditional NCSM calculations. In earlier applications we already employed the IM-NCSM for addressing scalar observables w.r.t. ground and excited states in even open-shell nuclei, however, this initial formulation of the IM-NCSM had several restrictions that we eliminate in this work. Due to the spherical formulation of the IM-SRG equations - which is mandatory from a computational point of view - the total angular momentum of the reference state is required to vanish and, thus, the IM-NCSM was restricted to the treatment of even nuclei. The particle-attached/particle-removed extension overcomes this restriction and makes odd nuclei accessible. Furthermore, the spherical formulation of the IM-SRG equations did not account for non-scalar operators and, therefore, the consistent transformation of electromagnetic observables was not possible. By deriving and implementing the IM-SRG equations corresponding to non-scalar observables, we open up the possibility to calculate electromagnetic observables from the IM-NCSM. These observables are sensitive to different aspects of the wave functions and, therefore, ideal for validating theoretical models and new opportunities for fruitful collaborations with experimentalists are opened up. For the transformation of observables we implemented a Magnus-type transformation, which determines the generator for the IM-SRG transformation and greatly reduces the computational effort. Considering numerical applications, we employ the IM-NCSM for the calculation of groundstate energies, excitation energies, radii, magnetic dipole moments, electric quadrupole moments, B(M1) transitions, and B(E2) transitions, where we study various medium-mass nuclei up to calcium isotopes. These calculations are already converged at very small model-space sizes-showing the great advantage of the IM-NCSM - and the results are compatible with large-scale NCSM calculations. These applications demonstrate that the IM-NCSM is now capable of addressing the full range of nuclear structure observables - including spectroscopic and electromagnetic observables - in fully open-shell nuclei.
[en] Hydrogen is considered to become a main energy vector in sustainable energy systems to store large amounts of intermittent wind and solar power. In this work, exergy efficiency and cost analyses are conducted to compare pathways of hydrogen generation (PEM, alkaline or solid oxide electrolysis), storage (compression, liquefaction or methanation), transportation (trailer or pipeline) and utilization (PEMFC, SOFC or combined cycle gas turbine). All processes are simulated with respect to their full and part-load efficiencies and resulting costs. Furthermore, load profiles are estimated to simulate a whole year of operation at varying loads. The results show power-to-power exergy efficiencies varying between about 17.5 and 43 %. The main losses occur at utilization and generation. Methanation features both lower efficiency and higher costs than compressed hydrogen pathways. While gas turbines show very high efficiency at full load, their efficiency drops significantly during load-following operation , while fuel cells (especially solid oxide) can maintain their efficiency and exceed the combined cycle gas turbine full-load efficiency. Overall specific costs between 245 €/MWh and 646 €/MWh are resulting from the simulation. Lower costs are commonly reached in chains with higher overall efficiencies. Installation costs are identified as predominant because of the low amount of full-load hours. To decrease the energy storage overall costs of the process chains, the options to use revenue generated by by-products such as oxygen and heat as well as changing the system application scenario are investigated. While the effect of the oxygen sale is negligible, the revenue generated by heat can significantly decrease overall costs. An increase of full-load by accounting for an electrolysis base-load to provide hydrogen for vehicles also shows a significant decreases in costs per stored energy down to 151 €/MWh at 2337 h/a full-load hours. The optimization of the exergy efficiency is performed by analysing physical and heat exergy recovery options such as expansion machines in the gas grid, the use of additional thermodynamic cycles (both Joule and Clausius-Rankine), as well as providing heat for steam electrolysis from compression inter-cooling, methanation or stored heat from a solid oxide fuel cell. The analysis shows that at full-load, process chains using solid oxide electrolysis, compressed hydrogen and a combined cycle gas turbine or a solid oxide fuel cells with a heat exergy recovery cycle can reach exergy efficiencies of 47 % and 45.5 %, respectively. A reversible solid oxide cell systems with metal-hydride heat and hydrogen storage can also reach 46.5 % exergy efficiency. The energy storage costs for these processes can be as low as 35 to 40 €/MWh at full-load. At load-following operation the efficiency of the fuel cell systems is expected to increase.
[en] In this work, new concepts for solving some of the current challenges of plasma-based acceleration are proposed and explored. These concepts, which rely on a combination of plasma-acceleration stages with a magnetic chicane, show that GeV-range beams with sub-percent energy stability and an unprecedented sub-per-mille energy spread could be produced. Achieving such a low energy spread, which is at least an order of magnitude below current state-of-the-art, has only been possible thanks to an improved understanding of the beam dynamics in this type of accelerators and the subsequent analytical modelling of previously unaccounted sources of energy spread. In addition to proof-of principle simulations and conceptual designs, a comprehensive study of sensitivity and tolerances of the acceleration concept is included here. This systematic study has only been possible thanks to a fast particle tracking code which has been integrally developed within this work. The positive findings presented here provide a new way towards the realization of reliable and high-quality plasma-based accelerators with a broad range of applications. Among these, the outstanding beam properties that can be reached with the presented schemes would allow for the demonstration of compact plasma-driven free-electron lasers. Thanks to these good prospects, the conceptual design of a 6 GeV accelerator based on the presented methods, which has been realized as part of this work, has been selected as a baseline option for the international EuPRAXIA project. Several of the ideas and studies carried out within this thesis have been published in peer-reviewed journals including Physical Review Letters and Scientific Reports.
[en] The requirements for reducing the greenhouse gas emissions of the power sector in Europe will result in a significant increase of generation from variable renewable energy sources (VRES). The presence of such technologies may pose significant challenges to the traditional operation and structure of the existing transmission grid. In this thesis, the integration of VRES into the future European power system is investigated until the year 2050. The introduced challenges translate to challenges of modeling the power system as well. Hence, the numerical modeling as well as the existing European framework of power system operation is described in detail, including the corresponding literature. In this thesis, a novel multi-level methodology for the generation dispatch that respects transmission constraints and includes flexible demand operation is introduced to model the pan-European power system. The final development of the model is completed via the determination of the system’s boundary conditions and technical parameters with respect to grid infrastructure, generation and demand in high spatio temporal resolution. The resulting model is verified for the year 2015 against historical conditions and forms the basis for the implementation of all future European scenarios. The future power system is analyzed for the years 2030, 2040 and 2050 with respect to VRES integration and the impact of demand flexibility. It is found that the main grid congestion occurs between the North and Baltic Sea regions and Central Europe. This congestion becomes responsible for the majority of the resulting VRES curtailments, which are related to wind generation. The total amount of curtailments for the reference case is 88 TWh for Germany and 729 TWh for Europe, out of which it is concluded that the most suitable locations for exploiting the corresponding curtailment energy occurs in western Denmark and western Ireland. Regarding the impact of demand flexibility, it is found that the overall impact is relatively small (7.6% reduction in VRES curtailments) and therefore more flexibility options should be considered. Moreover, it is found that VRES integration is more sensitive to the shifting duration rather than to the available flexibility especially when seasonal flexibility is allowed, while also it is shown that shifting in space can also become very beneficial (27% reduction). However load shifting cannot constitute the only solution for their mitigation but further alternatives may be required as well. Examining all scenarios for 2050, it is found that the average amount of VRES curtailments becomes 592 TWh and that this value approximately doubles every 10 years from 2030 to 2050. Finally, it is shown that the level of the spatial resolution for the transmission grid representation plays a significant role with respect to VRES integration, where even models with 100-200 nodes can underestimate the total curtailments by half.
[en] The increasing energy demand has motivated the research for renewable and sustainable sources for energy generation, such as solar energy. In this aspect, the dye sensitized solar cells (DSSC) are promising due its ability of providing energy over any light intensity. Zinc oxide (ZnO) is a well-studied n type semiconductor for use in these devices because it is a nontoxic material, inexpensive and environmental friendly, besides its physical characteristics, such as: band gap of 3,7 eV. The aim of this work was to synthesize ZnO nanostructured electrodes using the methods: Successive Ionic Layer Adsorption and Reaction (SILAR), for the seeds synthesis; and Chemical Bath Deposition (CBD), for the nanostructures growth. The nanostructures were synthesized using the precursors: zinc acetate dihydrate, zinc chloride, zinc sulfate heptahydrate and zinc nitrate hexahydrate. For each precursor, the photoanodes with distinct morphologies according to the zinc salt studied, 10 µm thick and with preferential orientation along the basal axis <0002> were obtained, and also photoanodes were obtained using the particulate material filtered from the chemical bath. The photoanodes were characterized by scanning electron microscopy, atomic force microscopy, X-ray fluorescence, and X-ray diffraction. The DSSC prepared using ZnO nanostructured photoanodes showed that the charge transport mechanism was influenced by the ZnO morphology. The particulate material from the chloride and nitrate zinc salts showed similar morphology after comminution, which resulted similar DSSCs. The DSSC produced using the de zinc sulfate powder presented the best electric parameters and it was the most efficient (η = 0,71 +-0,02%). (author)