Featured Publications Q3-2026

Energy and AI | Volume 25, September 2026 | 100871

Sahil Vishram Vadadkar, Beatrice Rodenbücher, Michael Kropp, Katharina Morawietz, Hans-Martin Henning, Manuel Lämmle, Andreas Velte-Schäfer

This study demonstrates the application of TabPFN, a transformer-based Tabular Foundation Model, to predict performance maps of variable-speed heat pumps and compressors. Led by PhD researcher Sahil Vishram Vadadkar at the Albert-Ludwigs-Universität Freiburg, the work evaluates prediction quality in low-data regimes compared to conventional machine learning methods and commonly applied polynomial models.

Polynomial models are limited to single variants and require recalibration for each new application. Physics-based models require a large number of parameters that are often not known and difficult to obtain. In contrast, TabPFN enables knowledge transfer across different heat pump variants and manufacturers. The model achieved highly accurate performance map predictions for both heat pumps and compressors, with reliable predictions possible using as few as one or two data points from the target variant. TabPFN consistently outperformed state-of-the-art methods including XGBoost, Random Forest, and Gradient Boost.

This data efficiency will reduce measurement requirements and accelerate modelling workflows for new component variants. The results indicate that TabPFN learns inherent relationships between input features and successfully transfers them to unknown compressor or heat pump variants through group indices in training datasets. This advanced training strategy paves the way for creating a transferable "learning environment" for building energy components.

While physics-based models remain necessary for transient state analysis, this data-driven approach offers a competitive alternative for steady-state performance prediction. The methodology may prove particularly valuable in practical engineering contexts during the design phase, where extensive measurement data is unavailable or costly to obtain.

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Energy Efficiency 18, 14 (2025).

Jessica Berneiser, Diana Maier, Sebastian Gölz, Sven Auerswald & Arnulf Dinkel

Mechanical ventilation systems are a key component of energy-efficient buildings: they ensure good indoor air quality, protect building structures, and prevent heat losses from uncontrolled window opening. Their importance is growing especially in increasingly airtight, renovated buildings, where natural ventilation through gaps and cracks in the façade is barely sufficient anymore. However, their real-world benefit strongly depends on how occupants actually accept and operate these systems in daily life. A study by Fraunhofer ISE investigated, based on a nationwide survey of 189 users of ventilation systems, which factors shape attitudes toward and satisfaction with mechanical ventilation.

Key findings: Perceived usefulness and ease of use are the strongest predictors of positive attitudes toward mechanical ventilation systems. For user satisfaction, perceived cleanliness and hygiene of the system also play an important role. Surprisingly, control options, noise level, and energy efficiency showed no statistically significant association with positive attitudes toward ventilation systems, despite being highlighted as relevant in an earlier qualitative pre-study. An intriguing contradiction emerged regarding control interfaces: although app-based control had previously been rated as less important, many respondents actually preferred touch displays and apps when choosing among concrete options, particularly younger and tech-savvy users, while older users favored simple switches for their clarity. Overall, respondents reported predominantly high satisfaction with their systems, though with some variability in individual experiences.

The study offers concrete implications for manufacturers and installers: clearly communicating the benefits and functioning of these systems, ensuring intuitive and target-group-specific operation, and providing targeted guidance on hygiene maintenance are likely to increase user acceptance and thereby support long-term, real-world energy efficiency in buildings.

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Applied Catalysis A: General | 5 January 2026 | 120616 | Volume 709

Miranda Guci, Markus Knäbbeler-Buß, Emma Verkama, Michael Günthel, Md Redwanul Islam, Lorenz Kienle, Erisa Saraçi, Jan-Dierk Grunwaldt, Florian Nestler

Sustainable carbon from chitosan: a new support material for ammonia cracking

Sustainably produced Ammonia is considered one of the most promising chemical hydrogen carriers for a global H₂ trade. Recovering hydrogen produced with lower carbon footprint from it, however, requires sustainable catalysts that crack ammonia at the lowest possible temperatures. For the first time, a team from Fraunhofer ISE together with KIT and Kiel University demonstrates that carbon supports derived from the renewable biopolymer chitosan are well suited for this purpose – sourced from chitin, which is available at roughly 6 million tonnes per year as biomass waste.

The supports were produced by hydrothermal carbonisation (HTC) followed by pyrolysis at 600 °C and 1000 °C, and loaded with only 1 wt% ruthenium. The key to performance lies in surface chemistry: the pyrolysis temperature controls the type and amount of oxygen and nitrogen surface groups – and thereby the distribution, reducibility and crystallinity of the Ru nanoparticles. Whereas untreated HTC-based carbon causes pronounced Ru agglomeration, the pyrolysed supports achieve uniform metal distribution and up to a 14-fold higher conversion rate in ammonia decomposition: more than 50 % NH₃ conversion already at 450 °C, outperforming a catalyst based on commercial activated carbon. The support pyrolysed at 1000 °C also excels in stability, maintaining constant conversion close to the reaction maximum/equilibrium for 72 hours at 500 °C with significantly lower mass loss due to suppressed side reactions, i.e., methanation of the support material.

The work was carried out within the AmmoCatCoat project, funded by the German Federal Ministry of Research, Technology and Space (BMFTR).

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Applied Physics Reviews | Volume 13, Issue 3 | September 2026

Andreas Lorenz, Baljeet Singh Goraya, Sebastian Pingel, Sebastian Nold, Florian Clement, Ralf Preu

Metallization is a decisive determinant of the efficiency, material demand, and cost of silicon solar cells. It involves the formation of metallic electrodes on the front and rear surfaces of the cell to collect and transport photogenerated charge carriers. Since the 1980s, screen printing has been the dominant industrial metallization technology because it is robust, cost-effective, and readily scalable for mass production. Over just a few decades, industrial contact-finger widths have decreased from approximately 100 µm to only 10–15 µm.

As the photovoltaic industry expands toward terawatt-scale production, silver consumption has emerged as a major technological, economic, and sustainability challenge. Silver remains a key component of metallization pastes; however, its consumption and price volatility substantially affect the economic viability and resource efficiency of photovoltaic manufacturing. High-efficiency cell architectures such as TOPCon, in particular, require comparatively high silver loadings because both cell surfaces must be contacted. In the long term, reducing silver consumption to below 2 mg Wp⁻¹ is widely regarded as a critical target for sustainable PV production.

In this review, we examine the technological evolution of screen printing for silicon solar cells and the economic and technical forces that have shaped it over recent decades. Our assessment of published data reveals that the pace of innovation in fine-line printing has accelerated markedly since 2013. Key drivers include rising silver prices, the transition from three-busbar designs to multi-busbar and multiwire interconnection concepts, and advances in screen-printing technologies and laser-assisted contact optimization (LECO).

Furthermore, this review identifies promising pathways toward silver-reduced metallization. These include advanced fine-line screen-printing processes, the renewed potential of stencil printing, and contact pastes incorporating alternative metals such as copper, nickel, and aluminum. The findings demonstrate that continued innovation in metallization and cell interconnection will be pivotal to enabling high-performance, resource-efficient silicon photovoltaics at the terawatt scale.

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