@article{VolpatodeSouzaPintoPereiraNeumeieretal.2025, author = {Volpato, Guilherme and de Souza Pinto Pereira, Adriano and Neumeier, Steffen and Hotza, Dachamir and G{\"o}ken, Mathias and Tetzlaff, Ulrich and Fredel, M{\´a}rcio Celso}, title = {Influence of a Standard Heat Treatment on the Microstructure and Properties of Inconel X-750 Produced by Laser Powder Bed Fusion}, volume = {27}, pages = {2500306}, journal = {Advanced Engineering Materials}, number = {24}, publisher = {Wiley}, address = {Weinheim}, issn = {1527-2648}, doi = {https://doi.org/10.1002/adem.202500306}, year = {2025}, abstract = {The production of nickel-base superalloys through powder bed fusion using a laser beam (PBF-LB) offers a promising method for reducing the cost of aeronautical components, especially those with complex geometries. However, when these materials are processed using PBF-LB, the standard heat treatments developed for conventional manufacturing routes do not consistently yield predictable microstructures or mechanical properties. Thus, this study analyzes how PBF-LB affects the microstructure and mechanical behavior of Inconel alloy X-750 when compared to a hot-rolled counterpart after undergoing a standard precipitation-hardening heat treatment (solution annealing, stabilization, and precipitation). Microstructure is examined using analytical electron microscopy and high-energy X-ray diffraction, while mechanical behavior is assessed through microhardness. Significant differences between both manufacturing routes are detected, so that PBF-LB processing led to an increase in grain size, anisotropy, fraction of low-angle grain boundaries, mean angle of misorientation, and dislocation density. Moreover, PBF-LB promoted the formation of γ′-Ni3(Al,Ti) and η-Ni3Ti phases during solution annealing and stabilization, respectively. Notably, the formation of γ′ contributes to an anomalous microhardness increase observed between these steps. These findings suggest that PBF-LB may inhibit recrystallization and facilitate precipitation during heat treatment, thereby affecting the performance of components produced using this technology.}, language = {en} } @article{AgricolaBaertlLandesbergeretal.2026, author = {Agricola, Barbara and B{\"a}rtl, Marko and Landesberger, Martin and Zhao, Huan and Palm, Frank and Kerschenlohr, Annegret and J{\"a}gle, Eric A.}, title = {The columnar to bimodal transition of Al-Cr-Mo-Sc-Zr alloys during laser powder bed fusion}, volume = {2026}, pages = {115770}, journal = {Materials \& Design}, number = {264}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0264-1275}, doi = {https://doi.org/10.1016/j.matdes.2026.115770}, year = {2026}, abstract = {Aluminium alloys processed via Powder Bed Fusion using a Laser Beam (PBF-LB) enable complex and lightweight components. Especially high-strength and heat-resistant Al alloys are in high demand for aerospace and motorsports applications, but the processability of these alloys remains critical due to hot-cracking along columnar grains. Therefore, the microstructural control of PBF-LB alloys is under increasing consideration. Al-Cr alloys have shown promising high-temperature properties and good processability in previous studies despite having a coarse and fully columnar grain structure. In this study, Al-Cr-Mo-Sc-Zr alloys with different compositions are subjected to phase analysis to understand the transition from fully columnar to bimodal grain structures. Synchrotron diffraction, electron dispersive spectroscopy, and atom probe tomography results have shown that three phases are present, irrespective of the alloys' composition: 𝛼-Al, Al45Cr7, and Al3(Sc,Zr). The introduction of Cr increases the lattice mismatch between 𝛼-Al and Al3(Sc,Zr) and is suspected to hinder grain refinement by Sc and Zr. Various thermodynamic simulations revealed the effect of grain refining elements (Sc+Zr) and Cr on the solidification path. The combination of simulation and experimental investigations led to three hypotheses on the columnar to bimodal transition in Al-Cr alloys. These results will help to further enable the microstructural control of PBF-LB processed alloys.}, language = {en} } @article{NgetunyBaldaufZoerner2026, author = {Ngetuny, Joshua Kiplagat and Baldauf, Tobias and Z{\"o}rner, Wilfried}, title = {Evaluating Feedstock Pretreatment Methods to Unlock Co-Digestion in Small-Scale Biogas Systems: A Multi-Criteria Approach to System Integration and Decision Making}, volume = {19}, pages = {1303}, journal = {Energies}, number = {5}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en19051303}, year = {2026}, abstract = {Small-scale biogas plants in developing countries present a viable alternative to traditional polluting energy sources, particularly in rural and underserved communities. These systems typically rely on locally sourced livestock manure; however, inconsistent supply often results in underfeeding, reduced biogas production, and, in many cases, system abandonment. Co-digestion with crop residues presents a promising strategy to enhance feedstock availability and system resilience. However, the recalcitrant nature of lignocellulosic biomass and limited access to suitable pretreatment technologies have constrained its adoption. This paper evaluates feasible pretreatment methods for integrating crop residues, especially straw, into small-scale biogas systems. Using the Analytic Hierarchy Process (AHP), pretreatment methods are assessed based on five criteria: (i) technology simplicity, (ii) energy requirements, (iii) capital and operational costs, (iv) effectiveness, and (v) environmental impact. The analysis identifies microbial pretreatment using the liquid fraction of digestate, combined with mechanical size reduction, as the most suitable approach for small-scale implementation, utilizing low-cost, simplified mechanical devices adaptable to various crop residues with minimal energy input. A conceptual design of a demonstration plant is proposed to validate this integrated pretreatment approach and assess its impact on biogas yield, system performance, and technology adoption. The design incorporates an on-site digestate separation unit to supply microbial inoculum and emphasizes simplicity and cost-effectiveness in material handling and energy use. Pilot trials are proposed to evaluate key performance indicators, including specific methane yield (LCH4/gVS added), volatile solids reduction (\%), and methane content increase (\%), ensuring evidence-based adoption and practical applicability of the design.}, language = {en} } @inproceedings{MuellerStrobelFaigletal.2024, author = {M{\"u}ller, Simon Nikolaus and Strobel, Rainer and Faigl, Markus and Schrag, Tobias}, title = {Analysis of Industrial 5GDHC System in Ingolstadt}, booktitle = {International Sustainable Energy Conference - Proceedings}, subtitle = {A Step Towards CO2-Neutral Industry}, editor = {Fink, Christian and Brunner, Christoph}, publisher = {TIB Open Publishing}, address = {Hannover}, issn = {2976-2030}, doi = {https://doi.org/10.52825/isec.v1i.1152}, year = {2024}, abstract = {This study comprehensively examines the technical manifestation and planning process for a shared thermal energy network at a 75-hectare industrial area in Ingolstadt. Unlike traditional systems, this (5GDHC) network showcases a smart integration of energy flows across 70 buildings with a yearly heating demand of around 17 GWh and a yearly cooling demand of around 35 GWh. The network spans over 9,100 meters of piping with diameters up to 800 mm. With thermal power from various sources including 1.8 MW waste heat from a data centre and potential for 10 MW from the Danube River, the system epitomizes a dynamic balance of heating and cooling demands. The paper itself examines the planning process of the system and encompasses topics such as defining energy requirements and load profiles, assessing potential energy sources and sinks for enhanced system efficiency, and analysing pipe and network design. Through this investigation, the study provides valuable insights towards a methodology to facilitate the successful implementation of future industrial 5GDHC systems, furthering the cause of sustainable energy.}, language = {en} } @article{SalamatMatternOlzemetal.2026, author = {Salamat, Babak and Mattern, Dominik and Olzem, Sebastian-Sven and Elsbacher, Gerhard and Seidel, Christian and Tonello, Andrea M.}, title = {GMP3: Learning-Driven, Bellman-Guided Trajectory Planning for AAVs in Real-Time on SE(3)}, volume = {14}, journal = {IEEE Access}, publisher = {IEEE}, address = {New York}, issn = {2169-3536}, doi = {https://doi.org/10.1109/ACCESS.2026.3661193}, pages = {22720 -- 22733}, year = {2026}, abstract = {We propose GMP3, a multiphase global path planning framework that generates dynamically feasible three-dimensional trajectories for unmanned aerial vehicles (UAVs) operating in cluttered environments. The framework extends traditional path planning from Euclidean position spaces to the Lie group SE(3), allowing joint learning of translational motion and rotational dynamics. A modified Bellman-based operator is introduced to support reinforcement learning (RL) policy updates while leveraging prior trajectory information for improved convergence. GMP3 is designed as a distributed framework in which agents influence each other and share policy information along the trajectory: each agent refines its assigned segment and shares with its neighbors via a consensus-based scheme, enabling cooperative policy updates and convergence toward a path shaped globally even under kinematic constraints.We also propose DroneManager, a modular ground control software that interfaces the planner with real UAVs platforms via the Micro Air Vehicle Link (MAVLink) protocol, supporting real-time deployment and feedback. Simulation studies and indoor flight experiments validate the effectiveness of the proposed method in constrained 3D environments, demonstrating reliable obstacle avoidance and smooth, feasible trajectories across both position and orientation.}, language = {en} } @article{HussenetherRufinoJuniorSelaibePiresetal.2026, author = {Hußenether, Thomas and Rufino J{\´u}nior, Carlos Ant{\^o}nio and Selaibe Pires, Tom{\´a}s and Mishra, Tarani and Nahar, Jinesh and Vaghani, Akash and Polzer, Richard and Diel, Sergej and Schweiger, Hans-Georg}, title = {Analysis of the Measurement Uncertainties in the Characterization Tests of Lithium-Ion Cells}, volume = {19}, pages = {825}, journal = {Energies}, number = {3}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en19030825}, year = {2026}, abstract = {The transition to renewable energy systems and electric mobility depends on the effectiveness, reliability, and durability of lithium-ion battery technology. Accurate modeling and control of battery systems are essential to ensure safety, efficiency, and cost-effectiveness in electric vehicles and grid storage. In engineering and materials science, battery models depend on physical parameters such as capacity, energy, state of charge (SOC), internal resistance, power, and self-discharge rate. These parameters are affected by measurement uncertainty. Despite the widespread use of lithium-ion cells, few studies quantify how measurement uncertainty propagates to derived battery parameters and affects predictive modeling. This study quantifies how uncertainty in voltage, current, and temperature measurements reduces the accuracy of derived parameters used for simulation and control. This work presents a comprehensive uncertainty analysis of 18650 format lithium-ion cells with nickel cobalt aluminum oxide (NCA), nickel manganese cobalt oxide (NMC), and lithium iron phosphate (LFP) cathodes. It applies the law of error propagation to quantify uncertainty in key battery parameters. The main result shows that small variations in voltage, current, and temperature measurements can produce measurable deviations in internal resistance and SOC. These findings challenge the common assumption that such uncertainties are negligible in practice. The results also highlight a risk for battery management systems that rely on these parameters for control and diagnostics. The results show that propagated uncertainty depends on chemistry because of differences in voltage profiles, kinetic limitations, and temperature sensitivity. This observation informs cell selection and testing for specific applications. Improved quantification and control of measurement uncertainty can improve model calibration and reduce lifetime and cost risks in battery systems. These results support more robust diagnostic strategies and more defensible warranty thresholds. This study shows that battery testing and modeling should report and propagate measurement uncertainty explicitly. This is important for data-driven and physics-informed models used in industry and research.}, language = {en} } @article{JamesKillingerMutangaetal.2025, author = {James, Stuart Daniel and Killinger, Markus and Mutanga, Chiedza Ngonidzashe and Pirard, Romain and Einax, Mario and Huber, Matthias and Bader, Tobias}, title = {The hybrid renewable energy community approach (HyRECA): Synergising electricity access with bush encroachment mitigation in rural Southern Africa}, volume = {2026}, pages = {100136}, journal = {Renewable and Sustainable Energy Transition}, number = {9}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2667-095X}, doi = {https://doi.org/10.1016/j.rset.2025.100136}, year = {2025}, abstract = {Rural electrification and bush encroachment in Southern Africa have long been studied separately. Research shows that hybrid renewable energy systems (HRES) offer viable solutions for off-grid communities, and bush encroachment mitigation is widely recognised as an ecological priority. Using Jamataka, Botswana, as a case study, this study integrates both, asking under which conditions encroacher bush-based HRES are economically viable, which electricity access levels local populations can afford, and whether biomass utilisation contributes to mitigation. Findings indicate strong potential for bush-based HRES in off-grid areas, but competitiveness declines where low-cost grid electricity is available. Economic viability is examined through levelised cost of electricity (LCOE) across alternative HRES configurations. HOMER Pro® simulations indicate PV/biomass/battery systems are most cost-effective off-grid, achieving 100 \% renewable fractions, near zero CO₂ emissions, and LCOE of 0.246 \$/kWh. In grid-connected contexts without feed-in, PV/diesel/grid combinations dominate (LCOE 0.117 \$/kWh) due to low tariffs, but with higher emissions. A novel affordability analysis using household willingness to pay and the World Bank Multi-Tier Framework indicates that all households reach at least Tier 3 electricity access under grid-connected systems and >70 \% off-grid, supporting household-use of medium-power appliances. Sustainable biomass extraction clears ∼12 ha annually (∼120 t) in Jamataka, aiding bush encroachment mitigation. Upscaling indicates potential to electrify 1.35 million people in >900 bush-encroached villages across Botswana, Namibia, and South Africa, using <1 \% of encroached land - highlighting significant untapped potential. Future research should validate findings through geospatial modelling with high-resolution biomass data and spatially sensitive biomass cost models for region-wide planning.}, language = {en} } @article{BienertRegnet2025, author = {Bienert, J{\"o}rg and Regnet, Simon}, title = {Stability Analysis for an Ultra-Lightweight Glider Airplane with Electric Driven Two-Blade Propeller}, volume = {9}, pages = {3}, journal = {Vibration}, number = {1}, publisher = {MDPI}, address = {Basel}, issn = {2571-631X}, doi = {https://doi.org/10.3390/vibration9010003}, year = {2025}, abstract = {Safety is the most important requirement in flight operations. This also affects the application for an extreme lightweight glider in this paper. Essential properties are the target weight below 120 kgand the electric propulsion. The unsymmetric inertia from the two-blade propeller at the rear in combination with the light and flexible aluminium tube support makes it necessary to investigate the risk of mechanical instability. Starting from the equations of motion, the time-variant system matrices are set up. The simulation of Floquet multiplier and Hill's hyper-eigenvalue problem provide the necessary information about the system stability. The conclusion is that the potential instability due to structural damping in the observed system can be avoided in the range of operation. The damping, experimentally determined by approximately 2\%, is sufficient.}, language = {en} } @article{MehtaLwakatareZoerneretal.2025, author = {Mehta, Kedar and Lwakatare, Bertha and Z{\"o}rner, Wilfried and Ehrenwirth, Mathias}, title = {Mini-grid performance in Sub-Saharan Africa: case studies from Tsumkwe and Gam, Namibia}, volume = {12}, pages = {30}, journal = {Sustainable Energy Research}, number = {1}, publisher = {SpringerOpen}, address = {Singapore}, issn = {2731-9237}, doi = {https://doi.org/10.1186/s40807-025-00174-y}, year = {2025}, abstract = {This paper investigates the performance analysis and operational challenges of mini-grids in Sub-Saharan Africa, focusing on the Tsumkwe and Gam mini-grids, the only officially recognized mini-grids in Namibia. The study addresses a critical gap in understanding mini-grid efficiency, technical difficulties, and future potential. The key research questions focus on assessing mini-grid performance, identifying technical and operational challenges, quantifying the relationship between electricity demand and supply, and providing recommendations for enhancing rural electrification through mini-grids. These insights are crucial for evaluating the effectiveness of mini-grids in the African context and understanding their role in advancing rural electrification. By using a mixed-method approach, the research combines quantitative and qualitative data to offer a comprehensive analysis of these two mini-grid systems of Namibia. The data collected from 2017 to 2022 include metrics on energy supply, consumption, photovoltaic generation, community load, and meteorological conditions. Qualitative insights were gathered through field visits, surveys, and interviews with mini-grid operators, allowing for a thorough examination of community perspectives, operational issues, and technical performance. The findings reveal that the Tsumkwe mini-grid has seen a decline in efficiency due to maintenance problems and battery overheating, while the Gam mini-grid, initially oversized, now struggles with increased demand and new connections. This study provides the first detailed technical insights, identifies consumer archetypes, and evaluates the energy dynamics of mini-grids in Namibia. Recommendations include improved maintenance protocols, advanced battery management, and enhanced data monitoring. By analyzing Tsumkwe and Gam, this paper offers valuable lessons for mini-grid development in Sub-Saharan Africa, stressing the need for continuous evaluation and strategic improvements to achieve sustainable rural electrification.}, language = {en} } @article{MehtaJainZoerner2025, author = {Mehta, Kedar and Jain, Rushabh Bansilal and Z{\"o}rner, Wilfried}, title = {Agrivoltaics Around the World: Potential, Technology, Crops and Policies to Address the Energy-Agriculture Nexus for Sustainable and Climate-Resilient Land Use}, volume = {18}, pages = {6417}, journal = {Energies}, number = {24}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en18246417}, year = {2025}, abstract = {The urgent pursuit of climate-resilient agriculture and clean energy systems, central to the Energy-Agriculture Nexus and the UN Sustainable Development Goals, has accelerated global interest in agrivoltaic (Agri-PV) technologies. This paper presents a global systematic review and meta-analysis of 160 peer-reviewed studies, structured through a five-stage thematic synthesis: (1) mapping global and regional Agri-PV deployment and potential, (2) analyzing system design and modeling methodologies, (3) evaluating crop suitability under partial shading, (4) reviewing enabling policies and regulatory frameworks, and (5) assessing techno-economic feasibility and investment barriers. Results reveal that Europe and Asia lead Agri-PV development, driven by incentive-based policies and national tenders, while limited regulatory clarity and high capital costs constrain wider adoption. Despite technological progress, no integrated model fully captures the coupled energy, water, and crop dynamics essential for holistic assessment. Strengthening economic valuation, policy coherence, and standardized modeling approaches will be critical to scale Agri-PV systems as a cornerstone of sustainable and climate-resilient land use.}, language = {en} }