Featured-Publications Q4-2025

Smart Energy | Volume 20 | November 2025 | 100188

Theda Zoschke , Christian Wolff, Armin Nurkanović, Gregor Rohbogner, Daniel Weiß, Lilli Frison, Moritz Diehl, Axel Oliva

In today's energy supply with district heating networks, decentralized heat generators are becoming increasingly important as networks grow and waste heat sources or renewable sources are integrated. Model predictive control (MPC) is a promising solution for optimizing dispatch planning in such multi-source heating networks. Trough anticipatory operation, MPC enables efficient use of available resources, thereby contributing significantly to cost reductions. While a linear formulation is sufficient for the integrated optimization problem at supply level, the consideration of thermohydraulic restrictions requires a nonlinear formulation, which can often lead to convergence problems in the solution.

In this study, the district heating network in Weil am Rhein was used as an example to analyze which thermohydraulic effects are actually required in an MPC formulation in order to reduce the number of equations to a minimum. A heat-based linear approach was compared with hydraulic simulations (pandapipes) and monitoring data in order to derive minimum requirements for the optimization problem.

The results show significant cost reductions through the implementation of MPC. Expected savings are around 17.8% under ideal conditions and 14.3% with a forecast error of ±20%. These savings result primarily from a reduction in fossil fuel usage though better storage utilization for peak load shaving and increased use of CHP units.

The importance of hydraulics was identified as critical: The maximum pump head can physically limit certain production unit combinations at high loads, so pressure losses and pump limits should be integrated into the MPC. While pump energy costs play a minor role in the order of operation, flow temperature optimization proves to be an additional lever that can enable moderate savings of around 1.8%.

For the implementation of MPC, it is recommended to first integrate pressure loss constraints and pump limits to ensure reliable operation. Considering the flow temperature as a decision variable provides additional savings potential. Overall, the study shows that predictive, heat-based MPC is of considerable value, especially in a changing energy market where decentralized heat generators are playing an increasingly important role.

Progress in Photovoltaics: Research and Applications | Volume 33, Issue 8 | Aug 2025 | Pages 813-922

David Chojniak, Alexandra Schmid, Jochen Hohl-Ebinger, Gerald Siefer, Stefan W. Glunz

Perovskite silicon tandem solar cells combine low production costs with high efficiencies and thus have the potential to replace the silicon solar cell that currently dominates the photovoltaic market. In recent years this has led to a rapid and successful development of the perovskite silicon tandem technology.

Nevertheless, there are still various challenges that oppose a successful market entry of this new solar cell technology. An aspect rarely considered in this context is the lack of suitable measurement setups and the corresponding measurement methods that enable reliable and traceable efficiency determination for perovskite silicon tandem modules of industrially relevant sizes.

In this work, this challenge is addressed with the help of a large-area LED-based solar simulator. It is shown how a complete calibration of large-area perovskite silicon tandem modules can be enabled by a consistent use of the spectral variability of the solar simulator. In addition to efficiency determination under precisely tailored spectral conditions, this also includes the measurement of external quantum efficiency, the determination of temperature coefficients, and a characterization of module properties under different spectral conditions. The different measurement methods are exemplarily applied to a large-area perovskite silicon tandem module provided by the company Oxford PV, which achieves an efficiency of 25%. This measurement thus represents the first fully traceable calibration of a large-area perovskite silicon tandem module.

Sustainable Energy Fuels | 2025 | 9, 5151

Ali Elwalily, Emma Verkama, Franz Mantei, Adiya Kaliyeva, Andrew Pounder, Jörg Sauer and Florian Nestler  

Sustainable aviation fuels (SAF) will play an increasingly important role in achieving the EU's sustainability goals in the coming years. The production of synthetic aviation fuels based on CO2-neutral methanol offers advantages over other processes, such as high SAF yield, lower land use, the possibility of dynamic process operation in case of fluctuating electricity supply, and potentially low costs.

This review article comprehensively analyzes the process chain SAF production from hydrogen and CO2 via methanol in order to identify potential for increasing efficiency and product yield to derive open research questions.

Future studies should focus on the interaction between the sub-processes of methanol synthesis, methanol-to-olefins (MTO) synthesis, oligomerization, and hydrogenation. An improved kinetic understanding of the MTO synthesis was identified as key to further process optimization, as it significantly influences the downstream process chain and the yield of aviation fuels.

As part of the SAFari project, measurements are currently carried out in the Fraunhofer ISE laboratories to understand the influences of the educt composition on the complex reaction network before optimizing the overall process with the help of detailed process simulations.

SCIENCE | Volume 390 | Issue 6772 | 30 Oct 2025 | DOI: 10.1126/science.adx1745

Oussama Er-raji, Christoph Messmer, Rakesh R. Pradhan, Oliver Fischer, Vladyslav Hnapovskyi, Sofiia Kosar, Marco Marengo, Mathias List, Jared Faisst, José P. Jurado, Oleksandr Matiash, Hannu Pasanen, Adi Prasetio, Badri Vishal, Shynggys Zhumagali, Anil R. Pininti, Yashika Gupta, Clemens Baretzky, Esma Ugur, Christopher E. Petoukhoff, Martin Bivour, Erkan Aydin, Randi Azmi, Jonas Schön, Florian Schindler, Martin C. Schubert, Udo Schwingenschlögl, Frédéric Laquai, Ahmed A. Said, Juliane Borchert, Patricia S. C. Schulze, Stefaan De Wolf, Stefan W. Glunz

Achieving terawatt-scale deployment of photovoltaic technologies necessitates both cost-effectiveness and resource efficiency. Perovskite/silicon tandem solar cells represent a highly promising avenue, offering power conversion efficiencies (PCE) of up to 34.85% with minimal additional manufacturing costs. Their commercial viability depends on the integration of industry-compatible architectures, such as monolithic fully-textured tandems employing standard silicon pyramid sizes (>1 μm). In this configuration, the perovskite layer is deposited via a hybrid evaporation/spin-coating process, forming a structured interface that effectively minimizes optical reflection losses. Nevertheless, the PCE of these devices remains constrained by photovoltage and charge transport losses at the perovskite/electron transport layer (ETL) interface.

To mitigate these limitations, an optoelectrical simulation study guided the exploration of two interfacial passivation strategies: chemical passivation and field-effect passivation. The latter demonstrated a unique advantage in perovskite systems, where electron accumulation extends beyond the interface into the bulk absorber, enhancing conductivity and reducing transport losses. Experimentally, the application of 1,3-diaminopropane dihydroiodide (PDAI) at the perovskite/ETL interface yielded a PCE of 33.1%, an open-circuit voltage of 2.01 V, and improved operational stability of the devices, as tested in the Red Sea Coast. These findings affirm that large pyramid textures do not impede effective passivation, thereby supporting the industrialization of high-efficiency fully-textured perovskite/silicon tandem solar cells.