Featured-Publications Q3-2025

Applied Thermal Engineering | Volume 278, Part A | 1 November 2025 | 127078

Matthieu Chaigneau, Timo Hennemann, Björn Nienborg

Energy savings through efficiency improvements make a significant contribution to achieving climate protection goals. Since cooling processes account for around 15% of electricity consumption in Germany, it is essential to investigate optimization potential in this area. In addition, fluctuating electricity prices are putting considerable pressure on cooling-dependent industries to strive for efficiency measures.

This study examines the energy-saving potential of dry-cooled refrigeration machines using a simple but robust control approach: The three controllable actuators (compressor, coolant pump, and dry cooler fan) are controlled proportionally over their permissible range to meet the cooling demand under the specific boundary conditions, treating them as flow machines with similar behavior. The effects of this control method are compared with two conventional control strategies on the one hand and with optimal control on the other. In the latter case, a model-based controller calculates the setpoints for the three actuators for each time step under changing operating conditions, minimizing total power consumption while meeting load requirements. Evaluation through simulations and experiments in a laboratory test facility shows that the proposed proportional control strategy with this simple approach achieves a reduction in seasonal electricity consumption of up to 14%. This corresponds to about two-thirds of the savings that could be achieved with a model-based approach, which is, however, much more complex and difficult to implement in practice.

Climate Policy | June 2025 | 1-18

Patrick Jürgens, Markus Kaiser, Charlotte Senkpiel, Connor Thelen, Christoph Kost & Hans-Martin Henning

To limit global warming to 1.5°C , rapid and significant reductions in greenhouse gas emissions are essential. However, there is a lack of analyses considering transition pathways using sector-coupled energy system models that limit national emissions to a 1.5°C  per capita carbon budget. This paper uses the REMod energy system model to derive a possible transition pathway within this budget.

The model results show that immediate action in all aspects of the energy system is required, together with fundamental changes in energy policy and society, in order to stay within the remaining carbon budget. A crisis response that induces substantial and immediate demand reduction through societal behaviour change is essential. Furthermore, annual capacity additions of renewable energy sources such as wind and solar need to increase at rates four to seven times higher than historical maxima and the direct electrification of all sectors should be accelerated by replacing technologies even before they reach the end of their life (e.g. gas boilers and internal combustion engine vehicles).

International Journal of Hydrogen Energy | Volume 138 | 16 June 2025 | Pages 985-1003

Friedrich Mendler, Nikolas Müller, Christopher Voglstätter, Tom Smolinka, Christopher Hebling, Barbara Koch

The study addresses the question of how regional hydrogen infrastructures can be developed and established in such a way that technical expansion meets market requirements, hydrogen supply meets the demand from the customers, and hydrogen costs are kept as low as possible. To answer this question, this work introduces a new spatially resolved, nonlinear, dynamic modeling framework and examines possible transformation pathways under changing boundary conditions and we are using new KPIs and statistics to highlight various aspects of the results. An important finding from the case studies is that, due to the limited local potential for renewable energies in the investigated region, expansion mainly depends on hydrogen imports. In the future, hydrogen pipelines are used for short distances and large volumes, while trucks are used for flexibility.

Advanced Energy Materials | Volume 15, Issue 32 | August 26, 2025 | e2500106

Oliver John, Andreas Nägele, Gernot Emanuel, Jan Nekarda, Ralf Preu

With the continuous global expansion of photovoltaics, sustainable production processes are becoming increasingly important. The focus is on reducing or fully substituting materials that are considered critical in terms of cost, environmental impact, or availability. In conventional manufacturing of solar cells and modules, these materials—aside from silicon—are primarily silver, copper, and lead-containing solders used for contacting and interconnection. Since 2007, Fraunhofer ISE has been developing a laser-based joining technology for bonding or welding ultra-thin aluminum foils to various joining partners, which can now be used in different variants for cell contacting and interconnection. These applications enable silver savings of around 50% as well as the complete substitution of copper and solder.

The paper describes the scientific foundations of this technology development, whose distinguishing feature is also the very small thickness of the aluminum foil (5–15 µm). The findings are relevant not only to photovoltaic applications. Laser welding of ultra-thin aluminum foil has a wide range of other applications and is already used commercially, for example in battery manufacturing.