FG Thermische Energietechnik
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Institute
BTU
District heating dynamic models arise as an alternative approach to in-situ experimental investigations. The main advantage of dynamic modeling and simulation is the possibility to avoid technical and operational risks that might occur during in-situ experimental investigations (e.g. heat demand is not met, damages in the energy systems etc.). Within this study, the authors present two models for an existing district heating system in Cottbus, Germany. One model is developed using the tool EBSILON Professional, while the other one is developed using the Simscape toolbox for physical modeling in Matlab/Simulink. The models were experimentally validated against measured data from the considered district heating system. The results show that the Simscape model has a better fit and better response than the EBSILON model. Yet, some discrepancies were found between the measured and the simulated data and, therefore, the uncertainties of the models were addressed. A comparative study between both tools is presented. The EBSILON models permit only unidirectional flow, whereas the Simscape toolbox permits reverse flow. Nevertheless, the EBSILON model outperforms the Simscape model in computation time. In addition, this study presents an approach for dynamic thermo-hydraulic modeling of district heating networks. This approach is utilized to examine the role of district heating networks as heat storage as an optimization configuration. The numerical results show less start-ups for additional heat sources. Yet, higher heat losses from the network are observed due to the installation of unburied pipelines.
A Lignite Fired Combined Cycle Heat and Power Plant using Presssurized Fluidized Bed Combustion
(1997)
Advancement of circulating pressurized fluidized bed combustion up to plants of the 2nd Generation
(2000)
Alkalische Druckelektrolyse - Schlüsseltechnologie für zukünftige Energie- und Speicherkonzepte
(2012)
ALVA 20 - Eine Laboranlage zur Untersuchung des Verbrennungsverhaltens in einer O2/CO2-Atmosphäre
(2007)
Analyse, Bewertung und Verbesserung der technischen Zuverlässigkeit des Heizkraftwerkes Cottbus
(2003)
Auswirkungen unscharfer Eingangsdaten auf Verfügbarkeitssimulation und Instandhaltungsoptimierung
(2009)
From its foundation of the chair of power plant
technology at Brandenburg University of Technology
Cottbus – Senftenberg, the combustion
research has engaged with current issues of conventional
power plant technology. The focus of
his research activity was starting from development
of technology to maximize the efficiency,
switched to the new research field of oxyfuel
technologies and working currently on questions
about operational flexibility as reaction of
changes in the current energy sector. There are
many concepts for increasing plant flexibility,
but without optimization of flame monitoring
and re-evaluation of existing limits, this potential
for optimization can’t be sufficiently used.
The current research project to increasing thermal
plant flexibility of existing coal-fired power
plants is implementing the necessity for analysis
and optimization research. Therefore, one
goal is a significant progress in the evaluation
of cyclic operation with higher load transients
and load cycles of coal-fired power plants. Furthermore,
a research evaluation about the effects
on the components life of components of
the water-steam cycle is possible.
CCS-Transportsystem - Untersuchung von Pipelinetransport und Injektion von CO2-reichen Fluiden
(2010)
CCT & CCS Technologies
(2009)
PEM water electrolysis is a clean and efficient conversion technology for hydrogen production and energy storage, especially when coupled with renewable energy sources. In spite of its many advantages, the high component and cell manufacturing costs of the conventional PEM electrolysis cell makes the PEM water electrolysis technology commercially less competitive vis-à-vis its peers. An alternative and cost effective cell design has been proposed which has up to a 25 % costs advantage over the conventional cell. In this alternative cell design, the flow channel plate which bears the most material costs in the conventional cell design has been replaced with a 3-D Porous Transport Layer (PTL) structure. While both designs perform comparably the same at low to mid current density (0 – 2 A/cm²), it has been observed that the conventional cell by far out performs the low cost cell at high current density operations, due to increased mass transport limitation in the cell without flow channels. Since industrial and commercial hydrogen production efforts are focused towards high current density operation (> 3 A/cm²), it thus becomes obvious that, in order for the cost effective alternative cell design to establish itself over the conventional cell design, the mass transport issues at high current densities have to be well understood and described.
This research work seeks to understand the source of, and to eliminate the mass transport losses in the cost effective alternative cell design in order to get it performing at least as good as the conventional cell design at current densities up to 5 A/cm². To meet this objective, 2-D non-isothermal semi-empirical fully-coupled models of both cell designs have been developed and experimentally validated. The developed validated models were then used as tools to simulate and predict the best operating conditions, design parameters and micro-structural properties of the PTL at which the mass transport issues in the design without flow channels will be at its minimum, so that both cells can exhibit comparable performance even at high current densities.
The models developed in this work are based on a multi-physics approach in which thermodynamic, electrochemical, thermal and mass transport sub-models are coupled and solved numerically, to predict the cell polarization and individual overpotentials, as well as address heat and water management issues. The most unique aspect of this work however, is the development of own semi-empirical equations for predicting the mass transport overpotential imposed by the gas phase (bubbles) at high current densities. Also, for the very first time, calculated PEM water electrolysis polarization curves up to 5 A/cm² have been validated by own experimental data.
The results show that, the operating temperature and pressure, inlet water flowrate and thickness of the PTL are the critical parameters for mitigating mass transport limitation at high current densities. In fact, it was found that, for the size of the cells studied (25 cm² active area each), when both cells are operating at the same temperature of 60 °C, the low cost cell design will have a comparable performance to the conventional designed cell even at 5 A/cm² current density when; the operating pressure is ≥ 5 bar, the feed water flowrate is ≥ 0.024l/min∙cm², PTL porosity is 50 %, PTL pore size is ≥ 11 µm and PTL thickness is 0.5 mm. At these operating, design and micro-structural conditions, the predicted difference between the polarizations of both cells will be only ~10 mV at 5 A/cm² operating current density.
CO2-freies Kraftwerk ab 2020
(2004)
Corrosion Processes and Carbonisation of Boiler Materials under Air and Oxyfuel Process Conditions
(2011)
Renewable energy sources are becoming a greater component of the electrical mix, while being significantly more volatile than conventional energy sources. As a result, net stability and availability pose significant challenges. Energy-intensive processes, such as chlor-alkali electrolysis, can potentially adjust their consumption to the available power, which is known as demand side management or demand response. In this study, a dynamic model of a chlor-alkali membrane cell is developed to assess the flexible potential of the membrane cell. Several improvements to previously published models were made, making the model more representative of state-of-the-art CA plants. By coupling the model with a wind power profile, the current and potential level over the course of a day was simulated. The simulation results show that the required ramp rates are within the regular operating possibilities of the plant for most of the time and that the electrolyte concentrations in the cell can be kept at the right level by varying inlet flows and concentrations. This means that a CA plant can indeed be flexibly operated in the future energy system.
To increase the efficiency of PEM electrolysis, simulation models are required that accurately describe the system's electrochemical and thermal behavior in a computationally efficient manner and are thus suitable for developing control strategies. Therefore, a pseudo-2D PEM electrolyzer model is presented in this paper, which is a compromise between the previously developed models regarding their model complexity. The electrochemical behavior is described with equations commonly used in the literature and the thermal behavior with correlations for gas-liquid heat transfer. Preliminary validation indicates that the model can describe the electrochemical behavior and thermal dynamics of a PEM electrolysis stack with good accuracy.
Mit der steigenden Erzeugung volatilen Stroms aus erneuerbaren Energien werden die Anforderungen an die Flexibilität der konventionellen Kraftwerke erhöht. Der Einsatz von Stützfeuerungssystemen auf Basis von Trockenbraunkohle (TBK) ermöglicht die Erweiterung des Lastbereiches und der Lastgradienten am Dampferzeuger. Untersuchungen zum Teillastverhalten von TBK-Brennern wurden an der BTU Cottbus – Senftenberg an einem 400 kWth Verbrennungsversuchstand und an dem industriellen 30 MWth TBK-Staubbrenner der Firma BBS (Babcock Borsig Steinmüller GmbH) durchgeführt. Der verfügbare Einsatzbereich des Brenners ist maßgeblich von der Intensität den brennernahen Mischungsvorgang abhängig. Mit der Absenkung der Brennerleistung ist beispielsweise eine signifikante Steigerung der NOx-Emission verbunden. Dieser Effekt ist auf die Veränderung des brennernahen Strömungsprofiles zurückzuführen. Mit Maßnahmen wie der Erhöhung der Drallzahl, Verteilung der Luftimpulsströme und Veränderung des Primärimpulses konnte eine Stabilisierung und Intensivierung der Reaktionszone und somit eine Verbesserte des Teillastverhaltens nachgewiesen werden.
1.
At first I was wondering what the structure of an article about pressurized steam fluidized bed drying could look like. After some thought, I knew that it should be divided into two parts. In order to highlight the creative and inventive spirit of former engineers, as well as their struggle to increase the efficiency of drying machines, a historical outline of the drying technology in general and the concept of steam fluidized bed drying in particular will form the first part of the article. The second part will present the practical and research contribution of Prof. Krautz and his colleagues to the advancement of this field. The article as a whole will be able to provide an overview of the coal/lignite drying, with focus on the pressurized steam fluidized bed drying principle implemented in the Lusatian mining area.
Druckelektrolyse zur Wasserstoffherstellung- eine Kurzübersicht zu energetischen Vor- und Nachteilen
(2015)
Dynamische Modellierung und Verfügbarkeitsmodellierung großer braunkohlegefeuerter Kraftwerke
(2002)