Open Access

PV and wind systems with PEM electrolysis offer great potential for producing hydrogen with low emissions. Our research has identified the ecologically optimal size of PEM in relation to fixed PV/wind capacities. We calculate efficiencies and production volumes for PEM with 240 capacity and site variations. We analyse the global warming potential of all systems and draw conclusions about the optimal system design. The lowest GWP is achieved at the site with the highest full load hours with 1.32 kg CO2-eq/kg H2 (Wind, 28 MW electrolysis) and 4.24 kg CO2-eq/kg H2 (PV, 23 MW electrolysis). We have identified a clear trend: increasing PV/wind full load hours leads to higher ideal PEM capacities. However, there is a significant discrepancy between the ideal economic and ecological capacity. Furthermore, higher electrolysis capacities can achieve lower emissions as they increasingly operate at a more efficient partial load.

The ramp-up of the hydrogen and Power-to-X economy in the EU and Germany is supported by a diverse mix of instruments. Existing research primarily examines individual support mechanisms or their interactions with energy markets and does not provide a comprehensive comparison of the wide range of EU and national instruments shaping the hydrogen and Power-to-X landscape. The objective of this study is to address these gaps by conducting a comprehensive, system-level analysis of how EU and national instruments collectively shape the ramp up of H2 and Power-to-X markets within the evolving legal framework of the Renewable Energy Directive III. To this end, this paper systematically analyses and compares key instruments - including the EU Emissions Trading System, Important Projects of Common European Interest, Carbon Contracts for Difference, H2Global and the European Hydrogen Bank - and evaluates their structure and impact across the hydrogen and Power-to-X value chain, encompassing production, transport and consumption. The analysis is based on a systematic literature review, through which relevant information is collected, structured, and organised into datasets using clearly defined criteria. This approach enables a transparent comparison and further analysis of the instruments while also providing the quantitative basis for the calculation of CO2 mitigation costs of expenditure-based instruments. Positive synergies can be obtained when they complement one another, such as when market mechanisms like H2Global are combined with investment subsidies like the Important Projects of Common European Interest. However, significant structural challenges remain. There are high bureaucratic hurdles for funding instruments like the Important Projects of Common European Interest and Carbon Contracts for Difference. The EU regulatory framework, particularly strict Renewable Fuels of Non-Biological Origin criteria, provides clear sustainability goals but can be a curse, limiting funding eligibility for viable, emission-free projects while other technologies like electromobility face no such restrictions. Furthermore, Renewable Fuels of Non-Biological Origin criteria on CO2 origin hinder the import of carbon-based Power-to-X products, putting the EU at a disadvantage. Our calculations on CO2 mitigation costs show that the European Hydrogen Bank and H2Global have lower greenhouse gas mitigation costs than Carbon Contracts for Difference by making use of existing infrastructure and green drop-in fuels. In conclusion, while the current instrument architecture offers a foundation, its potential is limited by incoherence, bureaucratic complexity, and regulatory contradictions. To fully unlock the new hydrogen and Power-to-X economy, greater coordination among instruments, more pragmatic Renewable Fuels of Non-Biological Origin criteria, and a reevaluation of rules on CO2 origin are needed. Ultimately, the most effective approach combines fraud-free, strictly enforced quotas with efficient instruments like the European Hydrogen Bank and H2Global.

Sector coupling is expected to play a decisive role as a key technology to realize the energy transition towards green energy supply. This work introduces, therefore, a comprehensive experimental study on a new power-to-heat system based on the continuous-flow, ohmic heating principle, which aims at utilizing renewable electricity in green processes. The ohmic heating technology, which is widely applied in the food industry, has been adapted and evaluated for delivering heat and domestic hot water to a single-family house. The introduced prototype is designed to convert renewable electricity into heat in the power range between 1000 and 3000 W with a typical electrical household installation (230 V, 50 Hz and 16 A fuse). A dedicated test rig has been developed and a comprehensive experimental campaign has been carried out to investigate the performance of the introduced system under typical operating conditions of a single-family house. Both the conversion efficiency and the dynamics of the thermal response of the introduced system have been assessed. It turned out that, the temperature lift between the return and supply of the reactor, and consequently, the conversion efficiency of electrical into thermal energy, are independent on the return temperature, for a fixed value of the volume flow rate of the electrolyte solution. A remarkable steady-state conversion efficiency of 97.5% has been measured. In addition, the dynamic response of the ohmic heating system has been found to be strongly dependent on the desired temperature lift. By an implemented controller, 95% of the steady state temperature lift of 44.5 K can be realized in 50 s, which marks an exceptionally rapid thermal response. The obtained results pave the way towards a field test study of the developed technology in a real household installation as well as to extend the focus on new fields such as green chemical processes.

Reliable recognition and localization of surgical instruments in endoscopic video recordings are foundational for a wide range of applications in computer- and robot-assisted minimally invasive surgery (RAMIS), including surgical training, skill assessment, and autonomous assistance. However, robust performance under real-world conditions remains a significant challenge. Incorporating surgical context – such as the current procedural phase – has emerged as a promising strategy to improve robustness and interpretability. To address these challenges, we organized the Surgical Procedure Phase, Keypoint, and Instrument Recognition (PhaKIR) sub-challenge as part of the Endoscopic Vision (EndoVis) challenge at MICCAI 2024. We introduced a novel, multi-center dataset comprising thirteen full-length laparoscopic cholecystectomy videos collected from three distinct medical institutions, with unified annotations for three interrelated tasks: surgical phase recognition, instrument keypoint estimation, and instrument instance segmentation. Unlike existing datasets, ours enables joint investigation of instrument localization and procedural context within the same data while supporting the integration of temporal information across entire procedures. We report results and findings in accordance with the BIAS guidelines for biomedical image analysis challenges. The PhaKIR sub-challenge advances the field by providing a unique benchmark for developing temporally aware, context-driven methods in RAMIS and offers a high-quality resource to support future research in surgical scene understanding.

In this study, the effect of post-synthetic ball milling on the structural and functional properties of as-synthesized nanoparticles of the copper-based metal-organic framework (MOF) HKUST-1 was investigated for the first time. Nanoparticles were synthesized using sodium formate as a capping agent. The crystalline particles were subjected to a controlled ball milling process, which induced significant structural changes. Powder X-ray diffraction (PXRD) revealed a reduction in crystallite size from 91 nm to 21 nm and the introduction of microstrain, partially disrupting the MOF's long-range crystalline order, as evidenced by peak broadening and the diminished intensity of high-angle reflections. Particle morphology pre- and post-milling was further studied with scanning electron microscopy (SEM) imaging, verifying a narrow particle size distribution of ± 22 nm after milling. Fourier-transform infrared spectroscopy (FTIR) indicated protonation of carboxylate groups in the larger pores of the framework, likely due to moisture incorporation during milling. Brunauer-Emmett-Teller (BET) surface area analysis showed a substantial decrease in specific surface area from 521 m²/g to 226 m²/g, suggesting a partial collapse of the porous framework. We discuss the applicability of ball milling as a versatile means of post-synthetic approach to reduce MOF particle sizes, a key element in the preparation of MOF-based thin films using inks or polymers.