@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} } @inproceedings{KangwanpongpanKlattKrautz, author = {Kangwanpongpan, Tanin and Klatt, Matthias and Krautz, Hans Joachim}, title = {Challenges of oxyfuel combustion modeling for carbon capture}, language = {en} } @inproceedings{KrautzKlattFindeisen, author = {Krautz, Hans Joachim and Klatt, Matthias and Findeisen, Alexander}, title = {CCT \& CCS Technologies}, language = {en} } @inproceedings{ZiemsTannertKrautz, author = {Ziems, Christian and Tannert, Daniel and Krautz, Hans Joachim}, title = {Approaches for simulation of an advanced alkaline water electrolyzer prototype}, series = {Proceedings of the 14th International Symposium on Heat Transfer and Renewable Sources of Energy, Szczecin-Miedzyzdroje, Poland, September 06-09, 2012}, booktitle = {Proceedings of the 14th International Symposium on Heat Transfer and Renewable Sources of Energy, Szczecin-Miedzyzdroje, Poland, September 06-09, 2012}, publisher = {Wydawnistwo Uczelnianie ZUT}, address = {Szczecinie}, isbn = {978-83-7663-121-9}, language = {en} } @inproceedings{ChalupnikKrautzWirtzetal., author = {Chalupnik, Rolf W. and Krautz, Hans Joachim and Wirtz, M. and Stuhlm{\"u}ller, F.}, title = {Applied Research for a New Generation of Lignite-Fired Combined Cycle Power Plant Using Circulating Pressurized Fluidized Bed Combustion}, language = {en} } @inproceedings{Findeisen, author = {Findeisen, Alexander}, title = {Analysis of corrosion behaviour of materials in oxyfuel fired power plants}, language = {en} } @inproceedings{TappeKrautz, author = {Tappe, Stephanie and Krautz, Hans Joachim}, title = {ALVA 20: a 20 kWth atmospheric laboratory test facility to investigate the combustion behaviour under "close-to-reality" conditions}, language = {en} } @phdthesis{Missagia, author = {Missagia, Bruna}, title = {Agricultural and forestry residues for decentralized energy generation in Brazil}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-25180}, pages = {214}, language = {en} } @misc{SharmaRoentzschShahi, author = {Sharma, Prerana and R{\"o}ntzsch, Lars and Shahi, Vinod K.}, title = {Advancements towards optimization of metal-organic framework-based polymer electrolyte membranes for aqueous redox flow batteries}, series = {Journal of materials chemistry : A, materials for energy and sustainability}, volume = {13}, journal = {Journal of materials chemistry : A, materials for energy and sustainability}, number = {17}, publisher = {Royal Society of Chemistry (RSC)}, address = {London}, issn = {2050-7488}, doi = {10.1039/D4TA08720H}, pages = {11952 -- 11988}, abstract = {Aqueous redox flow batteries (ARFBs) are considered a potential technology for large-scale energy storage owing to their eco-friendliness, high current density, and tuneable capacity. Polymer electrolyte membranes (PEMs) are vital components of ARFB, but they suffer from significant capacity/efficiency deterioration due to a lack of advancement in structural framing. To enhance the effectiveness of ARFBs, various membrane types have been optimized. However, the development of an efficient PEM remains a significant problem. Metal-organic frameworks (MOFs) made up of metal sites and organic linkers have gained significant scientific interest. As a result of their large surface area, adjustable pore diameters, and customized functionality, MOF-based PEMs are regarded as effective separators for ARFB. This review covers the state of the art MOF-based PEMs as ARFB separators. In recent years, significant efforts have been made to utilize the unique characteristics of MOFs as they not only improve the conductivity (attributed to their 3D channel structure) and gradient distribution in the polymer framework but also stabilize and mitigate active species cross-over by regulating the effective pore size. The aforementioned tactics can stimulate more research on energy storage technologies and provide future insight into the development and design of size-sieving separators for ARFB.}, language = {en} } @inproceedings{SchierackKrautzPriesmeieretal., author = {Schierack, Frank and Krautz, Hans Joachim and Priesmeier, U. and Nies, T.}, title = {Advancement of circulating pressurized fluidized bed combustion up to plants of the 2nd Generation}, isbn = {3-18-091535-9}, language = {en} }