Sweden
Zero-emission Propulsion System Featuring, Flettner Rotors, Batteries and Fuel Cells, for a Merchant Ship
Jul 2024
Publication
To meet the International Maritime Organization’s (IMO) goal of decarbonising the shipping sector by 2050 zero-emission ship propulsion systems should be developed to replace conventional fossil fuel-based ones. In this study we propose a zero-emission hybrid hydrogen-wind-powered propulsion system to be retrofitted to a benchmark merchant ship with a conventional propulsion system. The ship and its propulsion systems are modelled using an in-house platform. We analyse power and energy requirements for the ship over a realistic route and one-year schedule factoring in actual sea and weather conditions. Initially we examine the battery-powered propulsion system which proves impractical even with a reduction in the ship’s speed and the addition of a charging station. This retrofitted battery-powered propulsion system will occupy a significant portion of the existing ship’s deadweight due to its substantial weight consequently reducing the ship’s cargo capacity. To address this we evaluate integrating a hydrogen-powered fuel cell system with power equal to the non-propulsive constant load in the ship. We demonstrate that under these conditions and with four Flettner rotors and the charging station positioned mid-port on the ship’s route the size of the zero-emission propulsion system can be approximately 20% of the deadweight rendering such a system feasible.
Prospective Life Cycle Assessment of Future Swedish Hydrogen-powered Aviation Pathways
Jun 2025
Publication
Hydrogen-powered aviation is promoted as a low-carbon alternative for future long-distance air travel but its broader environmental impacts remain unclear. This study evaluates the potential environmental impacts of six future air travel pathways in Sweden including e-kerosene liquid hydrogen and fossil kerosene using prospective life cycle assessment. Results show that hydrogen-powered aviation has lower global warming potential than fossil kerosene but higher impacts on other environmental issues such as toxicity and land use. Key hotspots include resources in energy infrastructure and energy use in fuel production and airport operations however resource substitutions and energy efficiency improvements have limits. This study highlights the potential environmental benefits and tradeoffs of hydrogen-powered aviation and also the dependency of aviation on other sectors. Further research should integrate technological innovations in long-distance air travel pathways with scenarios that account for demand-side measures as well as regulatory political and economic barriers.
Determining Pilot Ignition Delay in Dual-Fuel Medium-Speed Marine Engines Using Methanol or Hydrogen
Jun 2025
Publication
Dual-fuel engines are a way of transitioning the marine sector to carbon-neutral fuels like hydrogen and methanol. For the development of these engines accurate simulation of the combustion process is needed for which calculating the pilot’s ignition delay is essential. The present work investigates novel methodologies for calculating this. This involves the use of chemical kinetic schemes to compute the ignition delay for various operating conditions. Machine learning techniques are used to train models on these data sets. A neural network model is then implemented in a dual-fuel combustion model to calculate the ignition delay time and is compared using a lookup table or a correlation. The numerical results are compared with experimental data from a dual-fuel medium-speed marine engine operating with hydrogen or methanol from which the method with best accuracy and fastest calculation is selected.
Emerging Green Steel Markets Surrounding the EU Emissions Trading System and Carbon Border Adjustment Mechanism
Oct 2025
Publication
The global steel industry accounts for 8–10 % of global CO2 emissions and requires deep decarbonisation for achieving the targets set in the Paris Agreement. However no low-emission primary steel production technology has yet been commercially feasible or deployed. Through analysing revisions and additions of European Union climate policy we show that green hydrogenbased steelmaking in competitive locations achieves cost-competitiveness on the European market starting 2026. If the deployment of competitive lowemission steelmaking is insufficient we show that the European steel industry loses competitiveness vis-à-vis countries with access to low-cost renewable energy. Therefore we assess the options for the European steel industry to relocate the energy-intensive ironmaking step and trade Hot Briquetted Iron for rapid deep decarbonisation of the European steel industry. Lastly we discuss complementing policy options to enhance the Carbon Border Adjustment Mechanism’s strategic value through European Union-lead global climate cooperation and the possibility of sparking an international decarbonisation race.
IEA TCP Task 43 - Recommendations for Safety Distances Methodology for Alkaline and PEM Electrolyzers
Sep 2025
Publication
Elena Vyazmina,
Richard Chang,
Benjamin Truchot,
Katrina M. Groth,
Samantha E. Wismer,
Sebastien Quesnel,
David Torrado,
Nicholas Hart,
Thomas Jordan,
Karen Ramsey-Idem,
Deborah Houssin-Agbomson,
Simon Jallais,
Christophe Bernard,
Lucie Bouchet,
Ricardo Ariel Perez,
Lee Phillips,
Marcus Runefors,
Jerome Hocquet and
Andrei V. Tchouvelev
Currently local regulations governing hydrogen installations vary by geographical region and by country leading to discrepancies in safety and separation distance requirements for similar hydrogen systems. This work carried out in the frame of IEA TCP H2 Task 43 (IEA TCP H2 2022) aims to provide an overview of various methodologies and recommendations established for risk management and consequence assessment in the event of accidental scenarios. It focuses on a case study involving industrial electrolyzers utilizing alkaline and PEM technologies. The research incorporates lessons learned from past incidents offers recommendations for mitigation measures reviews existing methodologies and highlights areas of divergence. Additionally it proposes strategies for harmonization. The study also emphasizes the most significant scenarios and the corresponding leakage sizes
Can Hydrogen-powered Air Travel Grow within the Planetary Limits?
Aug 2025
Publication
Air travel demand is rising rapidly and the aviation sector is relying on technology to decouple environmental impacts from its growth. Using Sweden as a case study we assessed the absolute environmental sustainability of medium-distance air travel in 2050 positioning the aviation sector's environmental impacts in relation to the planetary limits. We employed a novel framework that integrates prospective life cycle assessment and absolute environmental sustainability assessment methodologies. Our findings suggest that projected medium-distance air travel powered by e-kerosene or liquid hydrogen could have life cycle environmental impacts that overshoot global climate change and biodiversity loss thresholds by several orders of magnitude. Based on our case results for Sweden for aviation to develop within the planetary limits we recommend cross-sector collaboration to address environmental impacts from fossil-free energy supplies and the establishment of integrated targets that incorporate broader environmental issues. Given the unlikelihood of decoupling growth from environmental impacts policymakers and the aviation sector should consider concurrently supporting technological development and implementing measures to manage air travel demand.
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