@phdthesis{Schreiber, author = {Schreiber, Matthias}, title = {Modellierung von Hydrodynamik und W{\"a}rme{\"u}bertragung in blasenbildenden Wirbelschichten zur Trocknung von Braunkohle}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-27263}, language = {de} } @phdthesis{Lechner, author = {Lechner, Stefan}, title = {Untersuchungen zur Berechnung und Optimierung des W{\"a}rme{\"u}bergangs bei der Dampfwirbelschicht-Trocknung am Beispiel von Lausitzer Braunkohlen}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-27120}, language = {de} } @inproceedings{WieseNimtzMoelleretal., author = {Wiese, Bernd and Nimtz, Michael and M{\"o}ller, Fabian and Otto, Christopher and Liebscher, Axel and Schmidt-Hattenberger, Cornelia}, title = {Determination of thermodynamics in a CO2 injection well using pressure and distributed temperature sensing}, series = {Models - repositories of knowledge, proceedings of Model CARE2011 held in Leipzig, Germany, September 2011}, booktitle = {Models - repositories of knowledge, proceedings of Model CARE2011 held in Leipzig, Germany, September 2011}, publisher = {IAHS Publication}, address = {Wallingford}, isbn = {978-1-907161-34-6}, pages = {286 -- 290}, language = {en} } @phdthesis{Hoehne, author = {H{\"o}hne, Olaf}, title = {Grundlagenuntersuchungen zum Einfluss des Systemdrucks auf die Trocknung von Braunkohle in Wasserdampf}, publisher = {Cuvillier}, address = {G{\"o}ttingen}, isbn = {978-3-9540407-6-6}, pages = {XV, 141}, language = {de} } @inproceedings{WiedemannKrautz, author = {Wiedemann, Philipp and Krautz, Hans Joachim}, title = {Numerical study of gas-solid fluidized beds: Analysis of pressure fluctuations for detection of disturbed fluidization}, series = {The 14th International Conference on Fluidization - From Fundamentals to Products}, booktitle = {The 14th International Conference on Fluidization - From Fundamentals to Products}, publisher = {Engineering Conferences International}, address = {New York}, abstract = {Numerical simulations using the Two Fluid Model are performed for gas-solid bubbling fluidized beds. The possibility to detect disturbances in the fluidization process is investigated by common analysis of pressure fluctuations and variation of the computational domain. Additionally the influences of different particle sizes and superficial gas velocities are studied. The results are compared with bubble properties obtained from a digital image analysis technique}, language = {en} } @misc{KrautzNimtz, author = {Krautz, Hans Joachim and Nimtz, Michael}, title = {Flexible Operation of CCS Power Plants to Match Variable Renewable Energies}, series = {Energy Procedia}, volume = {2013}, journal = {Energy Procedia}, number = {40}, issn = {1876-6102}, doi = {10.1016/j.egypro.2013.08.034}, pages = {294 -- 303}, abstract = {The German Energiewende is resulting in high grid load changes caused by renewable energies. Therefore flexibility of power plants is getting more and more important. Future CCS power plants are usually equipped with more components than conventional power plants, resulting in a more complex and inert reaction on changes in power output. Additionally, due to the change in price structures and higher fixed and operational costs for CCS power plants, it is harder for them to be economically efficient. This study will show different options to increase the flexibility of CCS power plants and evaluate their benefits.}, language = {en} } @misc{KrautzCorreadaSilvaKangwanpongpan, author = {Krautz, Hans Joachim and Corr{\^e}a da Silva, Rodrigo and Kangwanpongpan, Tanin}, title = {Flame pattern, temperatures and stability limits of pulverized oxy-coal combustion}, series = {Fuel : the science and technology of fuel and energy}, journal = {Fuel : the science and technology of fuel and energy}, number = {Vol. 115}, issn = {0016-2361}, doi = {10.1016/j.fuel.2013.07.049}, pages = {507 -- 520}, abstract = {The challenges in maintaining a stable oxy-coal flame have been reported in the open literature. In case of pulverized coal combustion, narrower flammable regimes arise not only of differences in the feed gas composition, but also due to changes in the flow dynamics because of reduced volume flow rate through the burners to match similar temperatures and radiative heat transfer within the furnace. The present work focuses on the study of flame structure and stability of pre-dried lignite fired by a staged feed-gas burner. Experimental runs were carried out in a 0.40 MWth laboratory facility, with the objective of investigating the effects of swirl strength and feed gas distribution in the burner registers. To assess the experimental data, a numerical study of the non-reacting flow in the near burner region is performed. Predicted flow pattern and flame images show that the primary fuel jet penetrates the internal recirculation zone, forming an annular doughnut reverse flow region for both firing conditions and resembling a type-1 flame pattern. Temperature measurements indicate that the feed gas distribution among the burner registers control the flame temperature in parallel with the swirl number in both air-fired and oxy-fired environments. The oxy-fuel cases exhibite markedly reduced temperatures on the flame axis. This difference in the core arises not just from the more pronounced penetration depth of the primary jet, but also due to reaction mechanisms including pyrolysis and gasification reactions at the higher concentrations of CO2 and water vapor. Flame stabilization is shown to be strongly dependent on an appropriate distribution of the feed gas and strength of swirling flow in the burner front. The results correlated in terms of swirl number, secondary/tertiary flow ratio and secondary/primary axial momentum point to similarities in the stability limits between air-firing and oxy-firing.}, language = {en} } @misc{AbangLiskKrautz, author = {Abang, Roger Atini and Lisk, Alexander and Krautz, Hans Joachim}, title = {Fireside corrosion of superheater materials under oxy-coal firing conditions}, series = {Energy Procedia}, volume = {40}, journal = {Energy Procedia}, issn = {1876-6102}, doi = {10.1016/j.egypro.2013.08.035}, pages = {304 -- 311}, abstract = {The present study investigates the fireside corrosion behavior of selected superheater materials, namely: T24, P92, VM12-SHC, A800HT, and 7RE10 under oxy-coal combustion atmospheres. Data on mass change, scale thickness, metal loss, surface morphology and micro-structural characteristics of corrosion products were obtained. The alloy specimens were analyzed by SEM-EDX, light microscopy and X-Ray diffraction techniques. The results after 2000 hours of exposure at a metal surface temperature of 600 °C indicate that metal wastage increased with decreasing Cr-content under oxy-coal conditions.}, language = {en} } @misc{LechnerMerzschKrautz, author = {Lechner, Stefan and Merzsch, Matthias and Krautz, Hans Joachim}, title = {Heat-transfer from horizontal tube bundles into fluidized beds with Geldart A lignite particles}, series = {Powder Technology}, journal = {Powder Technology}, number = {253}, doi = {10.1016/j.powtec.2013.10.041}, pages = {14 -- 21}, abstract = {This work investigates the heat transfer mechanism in fluidized beds equipped with horizontal heat exchanger surfaces such as single tubes and especially tube bundles. Previous works were performed for varying operating conditions and solids' material properties, leading to a heterogeneous and therefore not applicable spectrum of derived correlations for the influence of tube diameter and tube bundle geometry on heat transfer. Based on a wide range validation of the correlation for the influence of single tube diameter on heat transfer coefficient, tube bundles with different tube diameters and horizontal and vertical spacings and alignments were investigated. Experiments were carried out using electrical heat transfer probes in a 0.15 m2 fluidized bed test facility at ambient conditions. Geldart A lignite and Geldart D solids were used in order to distinguish between predominant particle-convective and gas-convective heat transfer mechanisms. The tube bundle reduction factor on heat transfer coefficient was derived as a key parameter based on dimensionless geometric numbers. This factor predicts the reduction of the heat transfer coefficient compared to that of the single tube due to the particle and gas flow disturbances caused by the immersed tubes. Tube diameter as well as tube bundle geometry were successfully implemented into useful correlations for predicting tube bundles' heat transfer of gas-solid fluidized bed systems operating with fine particles.}, language = {en} } @incollection{FischerRabannKrautz, author = {Fischer, Ulrich and Rabann, Bernd and Krautz, Hans Joachim}, title = {Wasserstoff - Elektrolyse}, series = {Erneuerbare Energien : VBI-Leitfaden}, booktitle = {Erneuerbare Energien : VBI-Leitfaden}, edition = {1. Auflage}, publisher = {Verband Beratender Ingenieure}, address = {Berlin}, pages = {85 -- 92}, language = {de} } @misc{KatzerKlattLisketal., author = {Katzer, Christian and Klatt, Matthias and Lisk, Alexander and Krautz, Hans Joachim}, title = {Erste Untersuchungsergebnisse an einem elektrisch z{\"u}ndenden Kohlenstaubbrennersystem}, series = {Verbrennung und Feuerung, 27. Deutscher Flammentag, Clausthal-Zellerfeld, 16. und 17. September 2015}, journal = {Verbrennung und Feuerung, 27. Deutscher Flammentag, Clausthal-Zellerfeld, 16. und 17. September 2015}, publisher = {VDI-Verlag}, address = {D{\"u}sseldorf}, isbn = {978-3-18-092267-6}, pages = {17 -- 28}, language = {de} } @misc{KatzerBabulKlattetal., author = {Katzer, Christian and Babul, Konrad and Klatt, Matthias and Krautz, Hans Joachim}, title = {Quantitative und qualitative relationship between swirl burner operating conditions and pulverized coal flame length}, series = {Fuel Processing Technology}, volume = {156}, journal = {Fuel Processing Technology}, issn = {0378-3820}, doi = {10.1016/j.fuproc.2016.10.013}, pages = {138 -- 155}, language = {en} } @inproceedings{ZiemsFischerKrautzetal., author = {Ziems, Christian and Fischer, Ulrich and Krautz, Hans Joachim and Luschtinetz, Thomas and Lehmann, Jochen}, title = {Project presentation-Novel 3D porous electrode materials for more efficient alkaline water electrolysis-AEL3D}, series = {Nutzung regenerativer Energiequellen und Wasserstofftechnik 2016, 23. Symposium Nutzung Regenerativer Energiequellen und Wasserstofftechnik, Stralsund, 3. - 5. November 2016}, booktitle = {Nutzung regenerativer Energiequellen und Wasserstofftechnik 2016, 23. Symposium Nutzung Regenerativer Energiequellen und Wasserstofftechnik, Stralsund, 3. - 5. November 2016}, publisher = {Fachhochschule}, address = {Stralsund}, isbn = {978-3-9817740-1-6}, pages = {175 -- 181}, language = {en} } @inproceedings{FischerTannertVoigtetal., author = {Fischer, Ulrich and Tannert, Daniel and Voigt, Andre and Ziems, Christian and Krautz, Hans Joachim and Barz, Mirko and Dinkler, Konstantin}, title = {Renewable Energy Storage by Hydrogen Production from Water Electrolysis}, series = {Technical and Economic Aspects of Renewable Energies - Know-How Transfer as Development Opportunity for Southern Europe}, booktitle = {Technical and Economic Aspects of Renewable Energies - Know-How Transfer as Development Opportunity for Southern Europe}, publisher = {Mensch und Buch}, address = {Berlin}, isbn = {978-3-86387-721-7}, pages = {118 -- 126}, language = {en} } @incollection{FischerKrautzWenskeetal., author = {Fischer, Ulrich and Krautz, Hans Joachim and Wenske, Michael and Tannert, Daniel and Kr{\"u}ger, Perco and Ziems, Christian and Stolten, Detlef and Emonts, Bernd}, title = {Hydrogen Hybrid Power Plant in Prenzlau, Brandenburg}, series = {Hydrogen Science and Engineering - Materials, Processes, Systems and Technology, Bd. 2}, booktitle = {Hydrogen Science and Engineering - Materials, Processes, Systems and Technology, Bd. 2}, publisher = {Wiley-VCH}, address = {Weinheim}, isbn = {978-3-5273323-8-0}, pages = {1033 -- 1052}, language = {en} } @inproceedings{ZiemsSakkasPosseltetal., author = {Ziems, Christian and Sakkas, Nikolaos Panagiotis and Posselt, Joachim and Krautz, Hans Joachim}, title = {Development of algorithms for the deployment planning and control of power-to-heat systems for the more efficient use of renewable surplus energy - project details}, series = {24. Energiesymposium Symposium - Nutzung regenerativer Energiequellen und Wasserstofftechnik}, booktitle = {24. Energiesymposium Symposium - Nutzung regenerativer Energiequellen und Wasserstofftechnik}, editor = {Luschtinetz, Thomas and Lehmann, Jochen}, publisher = {Stralsund}, address = {Hochschule, Inst. f{\"u}r Regenerative EnergieSysteme}, isbn = {978-3-9817740-3-0}, pages = {194 -- 211}, language = {en} } @inproceedings{GuerreroKlattKrautz, author = {Guerrero, Cinthya and Klatt, Matthias and Krautz, Hans Joachim}, title = {Energy transition in Germany: a case study on renewable energy integration and its impact in the operation and efficiency of coal-fired power plants}, series = {Southern African Energy Efficiency Convention (SAEEC 2017), 14th and 15th November 2017, Gauteng, S{\"u}dafrika}, booktitle = {Southern African Energy Efficiency Convention (SAEEC 2017), 14th and 15th November 2017, Gauteng, S{\"u}dafrika}, isbn = {978-0-6399125-0-9}, pages = {6}, language = {en} } @misc{MieckKrautz, author = {Mieck, Sebastian and Krautz, Hans Joachim}, title = {Systematic analysis and preparation of high resolution in-situ measurements for the estimation of PV module parameters}, series = {VGB PowerTech}, volume = {98}, journal = {VGB PowerTech}, number = {8}, issn = {1435-3199}, pages = {75 -- 81}, abstract = {In the last two decades, a rapid expansion of photovoltaic (PV) power plants of different sizes has taken place. Along with this, the interest from science and industry is growing, exploring the strengths and weaknesses of this technology as well as further developing the efficiency in its production and operation. For planning and operating of PV power plants, valid energy yield forecasts are desirable. These forecasts are also important to draw conclusions for the monitoring of future PV technologies. The analysis, evaluation and processing of meteorological and technical measurement datasets play an essential role. In this article, high-resolution measurement data sets of a mobile, autarkic test system are analyzed firstly. The measured data are checked for plausibility and validity with the corresponding methods. After this observations and phenomena with meteorological cause are described. In a second step, a practicable procedure for the preparation of the measurement data is presented, in order to make it suitable for further calculations, e.g. identification of photovoltaic module parameters for energy yield calculations. The focus is particularly on the flexibility, adaptability and code performance of the processing procedure. Results, evaluations and outlooks on the methods used, measurement data and selected software packages are made.}, language = {en} } @phdthesis{Ojong, author = {Ojong, Emile Tabu}, title = {Characterization of the Performance of PEM Water Electrolysis Cells operating with and without Flow Channels, based on Experimentally Validated Semi-empirical Coupled-Physics Models}, address = {Cottbus ; Senftenberg}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-46504}, pages = {XXV, 146}, abstract = {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-{\`a}-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.}, language = {en} } @techreport{KlattPfeifferBendigetal., author = {Klatt, Matthias and Pfeiffer, Klaus and Bendig, Martin and Platta, Kristian and Matzekat, David}, title = {Betrachtungen zur Mindesterzeugung von Braunkohlekraftwerken im Kontext des Netzbetriebs}, publisher = {Brandenburgische Technische Universit{\"a}t, Fachgebiet Dezentrale Energiesysteme [u.a.]}, address = {Cottbus ; Senftenberg}, language = {de} }