@article{MikhaeilGadererDawoud, author = {Mikhaeil, Makram and Gaderer, Matthias and Dawoud, Belal}, title = {On the development of an innovative adsorber plate heat exchanger for adsorption heat transformation processes; an experimental and numerical study}, series = {Energy}, volume = {207}, journal = {Energy}, number = {September}, publisher = {Elsevier}, doi = {10.1016/j.energy.2020.118272}, pages = {1 -- 13}, abstract = {An innovative adsorber plate heat exchanger (APHE), which is developed for application in adsorption heat pumps, chillers and thermal energy storage systems, is introduced. A test frame has been constructed as a representative segment of the introduced APHE for applying loose grains of AQSOA-Z02. Adsorption kinetic measurements have been carried out in a volumetric large-temperature-jump setup under typical operating conditions of adsorption processes. A transient 2-D model is developed for the tested sample inside the setup. The measured temporal uptake variations with time have been fed to the model, through which a micro-pore diffusion coefficient at infinite temperature of 2 E-4 [m2s-1] and an activation energy of 42.1 [kJ mol-1] have been estimated. A 3-D model is developed to simulate the combined heat and mass transfer inside the APHE and implemented in a commercial software. Comparing the obtained results with the literature values for an extruded aluminium adsorber heat exchanger coated with a 500 μm layer of the same adsorbent, the differential water uptake obtained after 300 s of adsorption (8.2 g/100 g) implies a sound enhancement of 310\%. This result proves the great potential of the introduced APHE to remarkably enhance the performance of adsorption heat transformation appliances.}, language = {en} } @article{HuberHeindlSchlosseretal., author = {Huber, Lea and Heindl, Melanie and Schlosser, Marc and Pfitzner, Arno and Dawoud, Belal}, title = {On the Cycle Stability and Macroscopic Structure of Iron Oxide Pellets for Thermochemical Hydrogen Storage: Influence of Water Content during the Pelletizing Process}, series = {Applied Sciences}, volume = {13}, journal = {Applied Sciences}, number = {11}, publisher = {MDPI}, address = {16}, doi = {10.3390/app13116408}, abstract = {Hydrogen storage based on the repeated reduction and oxidation (redox) reactions of iron oxide/iron composites represents a promising technology. This work is dedicated to studying the influence of the amount of water added during the pelletizing process on the cycle stability and structure of iron oxide pellets. The storage composites were prepared from iron oxide (Fe2O3) and 10 wt.-\% support material (cement) with different amounts of water (18 and 33 wt.-\%) in a laboratory-scale pelletizing disk. To evaluate the cycle stability of the composites, the kinetics of the redox reactions were experimentally measured at 800 ∘ C in an atmosphere of 50\% N2 and 50\% H2 (reduction) or 50\% steam (oxidation), respectively. Moreover, the structure of the pellets was analyzed by micro-computed tomography scans. It turned out that pellets with higher water contents attained faster kinetics and a higher cycle stability. The sample with the least water content (18 wt.-\%) needed about 26 min and 19 min to reach a conversion rate of 80\% during the reduction and oxidation reactions of the sixth redox cycle, respectively. In contrast, the sample with the highest water content (33 wt.-\%) could achieve the same conversion rate after 18 min (reduction) and 13 min (oxidation) during the ninth redox cycle.}, language = {en} } @article{SteiningerGadererDawoud, author = {Steininger, Peter and Gaderer, Matthias and Dawoud, Belal}, title = {Assessment of the Annual Transmission Heat Loss Reduction of a Refurbished Existing Building with an Advanced Solar Selective Thermal Insulation System}, series = {Sustainability}, volume = {13}, journal = {Sustainability}, number = {13}, publisher = {MDPI}, address = {Basel}, doi = {10.3390/su13137336}, pages = {1 -- 19}, abstract = {A numerical parameter sensitivity analysis of the design parameters of the recently published solar selective thermal insulation system (SATIS) has been carried out to enhance its thermal and optical properties. It turned out that the insulation properties of SATIS can be effectively improved by reducing the length of the glass closure element. Increasing the area share of the light conducting elements (LCEs) and decreasing their length-to-diameter (L/D) ratio were identified as key parameters in order to increase the solar gain. Two SATIS variants were compared with the same wall insulation without SATIS in a yearly energetic performance assessment. The SATIS variant with 10 mm length of the closure element, 44.2\% area share of LCE, as well as front and rear diameters of 12 mm/9 mm shows an 11.8\% lower transmission heat loss over the heating period than the wall insulation without SATIS. A new methodology was developed to enable the implementation of the computed solar gains of SATIS in 1D simulation tools. The result is a radiant heat flow map for integration as a heat source in 1D simulation models. A comparison between the 1D and 3D models of the inside wall heat fluxes showed an integral yearly agreement of 98\%.}, language = {en} } @article{BringoutErbFrikel, author = {Bringout, Ga{\"e}l and Erb, Wolfgang and Frikel, J{\"u}rgen}, title = {A new 3D model for Magnetic Particle Imaging using realistic magnetic field topologies for algebraic reconstruction}, series = {Inverse Problems}, volume = {36}, journal = {Inverse Problems}, number = {12}, publisher = {IOP Publishing}, doi = {10.1088/1361-6420/abb446}, abstract = {We derive a new 3D model for magnetic particle imaging (MPI) that is able to incorporate realistic magnetic fields in the reconstruction process. In real MPI scanners, the generated magnetic fields have distortions that lead to deformed magnetic low-field volumes with the shapes of ellipsoids or bananas instead of ideal field-free points (FFP) or lines (FFL), respectively. Most of the common model-based reconstruction schemes in MPI use however the idealized assumption of an ideal FFP or FFL topology and, thus, generate artifacts in the reconstruction. Our model-based approach is able to deal with these distortions and can generally be applied to dynamic magnetic fields that are approximately parallel to their velocity field. We show how this new 3D model can be discretized and inverted algebraically in order to recover the magnetic particle concentration. To model and describe the magnetic fields, we use decompositions of the fields in spherical harmonics. We complement the description of the new model with several simulations and experiments, exploring the effects of magnetic fields distortion and reconstruction parameters on the reconstruction.}, language = {en} } @article{FrazzicaBrancatoDawoud, author = {Frazzica, Andrea and Brancato, Vincenza and Dawoud, Belal}, title = {Unified Methodology to Identify the Potential Application of Seasonal Sorption Storage Technology}, series = {Energies}, volume = {13}, journal = {Energies}, number = {5}, publisher = {MPDI}, address = {Basel}, doi = {10.3390/en13051037}, pages = {1 -- 17}, abstract = {In this study, the definition of a new methodology for a preliminary evaluation of the working boundary conditions under which a seasonal thermal energy storage (STES) system operates is described. The approach starts by considering the building features as well as the reference heating system in terms of solar thermal collectors' technology, ambient heat sinks/source, and space heating distribution systems employed. Furthermore, it is based on a deep climatic analysis of the place where the STES needs to be installed, to identify both winter and summer operating conditions. In particular, the STES energy density is evaluated considering different space heating demands covered by the STES (ranging from 10\% up to 60\%). The obtained results demonstrate that this approach allows for the careful estimation of the achievable STES density, which is varies significantly both with the space heating coverage guaranteed by the STES as well as with the ambient heat source/sink that is employed in the system. This confirms the need for careful preliminary analysis to avoid the overestimation of the STES material volume. The proposed approach was then applied for different climatic conditions (e.g., Germany and Sweden) and the volume of one of the most attractive composite sorbent materials reported in the literature, i.e., multi-wall carbon nanotubes (MWCNT)-LiCl, using water as the working fluid, needed for covering the variable space heating demand in a Nearly Zero Energy Building (NZEB) was calculated. In the case of Swedish buildings, it ranges from about 3.5 m3 when 10\% of the space heating demand is provided by the STES, up to 11.1 m3 when 30\% of the space heating demand is provided by the STES.}, language = {en} } @article{ChatzitakisDawoud, author = {Chatzitakis, Paris and Dawoud, Belal}, title = {An alternative approach towards absorption heat pump working pair screening}, series = {Renewable Energy}, volume = {110}, journal = {Renewable Energy}, publisher = {Pergamon-Elsevier}, organization = {PERGAMON-ELSEVIER SCIENCE LTD}, doi = {10.1016/j.renene.2016.08.014}, pages = {47 -- 58}, abstract = {The successful market penetration of modern absorption heat pumps (AHP) today is critically dependent on their thermodynamic performance as well as other key factors like cost, reliability and inherent safety. Conventional AHPs have a proven record in the first two aspects but crucial shortcomings in the last two. For this reason it has been imperative to search for alternative working pairs that could potentially provide comparable performance while also satisfying the rest of the conditions to the best extent possible. As part of a systematic approach towards this direction, a detailed cycle analysis was performed, utilizing an idealized AHP system containing a real working pair, which enabled the identification of five dimensionless parameters and key thermophysical properties that influence the system's thermodynamic efficiency and the circulation ratio. In order to validate those findings, these parameters were calculated and compared between conventional and alternative AHP refrigerants. It turned out that low molecular weight ratios between absorbent and refrigerant have a beneficial effect on both coefficient of performance and the circulation ratio. Furthermore, both the refrigerant acentric factor and the absorbent vaporization enthalpy shall be minimized to obtain better performance. (C) 2016 Elsevier Ltd. All rights reserved.}, language = {en} } @inproceedings{KrausBrueckl, author = {Kraus, Hermann and Br{\"u}ckl, Oliver}, title = {Automated use of wired measures in grid planning for solving current and voltage band problems}, series = {Power and Energy Student Summit (PESS) 2019, Magdeburg}, volume = {77}, booktitle = {Power and Energy Student Summit (PESS) 2019, Magdeburg}, publisher = {Otto-von-Guericke-Universit{\"a}t, Institut f{\"u}r Elektrische Energiesysteme}, address = {Magdeburg}, isbn = {978-3-944722-84-9}, doi = {10.24352/UB.OVGU-2019-086}, pages = {207 -- 211}, abstract = {This work deals with the use of cable exchange and parallel cabling as network expansion measures in the context of an automated grid planning for the elimination of current and voltage band problems in a distribution network. Inter alia, reference is made to a higher-level program, which is being developed in the EU project "CrossEnergy", and the procedures for remedying the limit value violations are presented.}, subject = {Netzplanung}, language = {en} } @inproceedings{MiedlBraun, author = {Miedl, Christian and Braun, J{\"u}rgen}, title = {Powertrain and electric system design of a 800-volt all-electric car}, series = {European Conference on Nanoelectronics and Embedded Systems for Electric Mobility, eMotion in Smart Cities, 24.-28. September, 2012, Bologna, Italy}, booktitle = {European Conference on Nanoelectronics and Embedded Systems for Electric Mobility, eMotion in Smart Cities, 24.-28. September, 2012, Bologna, Italy}, language = {en} } @article{OstermeierMottokKnorretal., author = {Ostermeier, Daniel and Mottok, J{\"u}rgen and Knorr, Christine and Huber, Michael}, title = {Competence Atlas for Save and Green Road Vehicles in the Electro Mobility Cluster Regensburg}, series = {Applied Research Conference 2012 (ARC 2012) 25./26. June 2012, Nuremberg}, journal = {Applied Research Conference 2012 (ARC 2012) 25./26. June 2012, Nuremberg}, editor = {Mottok, J{\"u}rgen and Ziemann, Olaf}, pages = {86 -- 92}, language = {en} } @inproceedings{Mottok, author = {Mottok, J{\"u}rgen}, title = {Migration path for secure and economic smart power grid devices with transitional smart metering support}, series = {2nd Applied Research Conference 2012 (ARC 2012), 25./26. June 2012, Nuremberg}, booktitle = {2nd Applied Research Conference 2012 (ARC 2012), 25./26. June 2012, Nuremberg}, pages = {64 -- 70}, language = {en} }