@misc{ZiemsTannertKrautz, author = {Ziems, Christian and Tannert, Daniel and Krautz, Hans Joachim}, title = {Project presentation: Design and installation of advanced high pressure alkaline electrolyzer-prototypes}, series = {Energy Procedia}, volume = {29}, journal = {Energy Procedia}, issn = {1876-6102}, doi = {10.1016/j.egypro.2012.09.087}, pages = {744 -- 753}, language = {en} } @misc{ThummarAbangMenzeletal., author = {Thummar, Krunalkumar and Abang, Roger Atini and Menzel, Katharina and Groot, Matheus Theodorus de}, title = {Coupling a Chlor-Alkali Membrane Electrolyzer Cell to a Wind Energy Source: Dynamic Modeling and Simulations}, series = {Energies}, volume = {15}, journal = {Energies}, number = {2}, issn = {1996-1073}, doi = {10.3390/en15020606}, pages = {1 -- 26}, abstract = {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.}, 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} } @misc{SchreiberAsegehegnKrautz, author = {Schreiber, Matthias and Asegehegn, Teklay Weldeabzgi and Krautz, Hans Joachim}, title = {Numerical and Experimental Investigation of Bubbling Gas-Solid Fluidized Beds with Dense Immersed Tube Bundles}, language = {en} } @misc{SakkasAbang, author = {Sakkas, Nikolaos Panagiotis and Abang, Roger Atini}, title = {Thermal load prediction of communal district heating systems by applying data-driven machine learning methods}, series = {Energy Reports}, volume = {8}, journal = {Energy Reports}, issn = {2352-4847}, doi = {10.1016/j.egyr.2021.12.082}, pages = {1883 -- 1895}, abstract = {Load forecasting is an essential part of the operational management of combined heat and electrical power units, since a reliable hour- and day-ahead estimation of their thermal and electrical load can significantly improve their technical and economic performance, as well as their reliability. Among different types of prediction techniques, data-driven machine learning methods appear to be more suitable for load estimation in operational systems, compared to the classical forward approach. Research so far has been concentrated mainly on the magnitude of buildings with single load types. It has only been extended to a limited degree on the level of a district heating network where several end users with different characteristics merge into one bigger scale heat consumer (city or group of communities). In this study, artificial neural networks are utilized, to develop a load prediction model for district heating networks. A segmented analytical multi-phase approach is employed, to gradually optimize the predictor by varying the characteristics of the input variables and the structure of the neural network. The comparison against the load prediction time series generated by a local communal energy supplier using a commercial software reveals that, although the latter is enhanced by manual human corrections, the optimized fully automatic predictors developed in the present study generate a more reliable load forecast.}, language = {en} } @misc{SakkasGillungThummaretal., author = {Sakkas, Nikolaos P. and Gillung, Frank and Thummar, Krunalkumar and Abang, Roger and R{\"o}ntzsch, Lars}, title = {Advanced pressurized alkaline water electrolysis at high temperatures up to 130 °C}, series = {International journal of hydrogen energy}, volume = {149}, journal = {International journal of hydrogen energy}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {0360-3199}, doi = {10.1016/j.ijhydene.2025.150075}, pages = {1 -- 12}, abstract = {Operating alkaline water electrolysers above 100 °C improves electrolyte conductivity and reaction kinetics significantly. To examine alkaline water electrolysis in this area in more detail a high-temperature pressurized test rig is designed and constructed. Nickel (Ni) foam electrodes coated with Raney nickel (Raney Ni) or nickel manganese (NiMn) and expanded Ni mesh electrodes coated with nickel(II) oxide (NiO) are utilized and the effect of electrolyte flow rate, electrode structure, pressure and temperature variation on the cell performance at temperatures up to 130 °C and pressures up to 16 bar are investigated. At the maximum current density of 1.67 A/cm2, 110 °C and 16 bar the electrode combination of Raney Ni coated Ni foam as cathode and NiO coated expanded Ni mesh electrode as anode attain the best outcome with a cell voltage of 2.29 V. In a 70 h duration test three-dimensional (3D) Ni foam electrodes with Raney Ni cathode and NiMn anode catalyst show a moderate cell degradation of 9.26 μV/h.}, language = {en} } @misc{NimtzKlattWieseetal., author = {Nimtz, Michael and Klatt, Matthias and Wiese, Bernd and K{\"u}hn, Michael and Krautz, Hans Joachim}, title = {Modelling of the CO2 process- and transport chain in CCS systems - Examination of transport and storage processes}, series = {Chemie der Erde - Geochemistry}, volume = {70}, journal = {Chemie der Erde - Geochemistry}, number = {3}, issn = {0009-2819}, doi = {10.1016/j.chemer.2010.05.011}, pages = {185 -- 192}, language = {en} } @misc{MissagiaGuerreroNarraetal., author = {Missagia, Bruna and Guerrero, Cinthya and Narra, Satyanarayana and Sun, Yaoming and Ay, Peter and Krautz, Hans Joachim}, title = {Physicomechanical properties of rice husk pellets for energy generation}, language = {en} } @misc{MerzschLechnerKrautz, author = {Merzsch, Matthias and Lechner, Stefan and Krautz, Hans Joachim}, title = {Heat-transfer from single horizontal tubes in fluidized beds: Influence of tube diameter, moisture and diameter-definition by Geldart C fines content}, series = {Powder Technology}, journal = {Powder Technology}, issn = {1873-328X}, doi = {10.1016/j.powtec.2012.12.002}, 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} }