Austria

Decarbonizing the steel industry will require a shift towards renewable energy. However costs and emissions associated with the long-distance transport of renewable energy carriers may incentivize the relocation of steel production closer to renewable energy sources. This “green relocation” would affect regional economic structures and global trade patterns. Nevertheless the macroeconomic and environmental impacts of alternative industry location options remain underexplored. This study compares the impacts on value-added prices and emissions under two options for decarbonizing the Dutch steel industry: importing green hydrogen from Brazil to produce green steel in the Netherlands versus relocating production to Brazil and transporting green steel to the Netherlands. Impacts are analyzed by combining a price and a quantity model within an environmentally extended multiregional input-output (EE-MRIO) framework. Results suggest that the relocation option brings the greatest synergies between climate and economic goals at the global level as it leads to lower production costs smaller price effects and greater emissions reductions. However relocation also results in stronger distributive impacts across global regions. Higher carbon prices would be insufficient to counteract relocation incentives. This calls for policymakers in industrialized countries to systematically consider the possibility of green relocation when designing decarbonization and industrial competitiveness strategies.

Reducing CO2 emissions is an increasingly important goal in general aviation. The dual-fuel hydrogen–kerosene combustion process has proven to be a suitable technology for use in small aircraft. This robust and reliable technology significantly reduces CO2 emissions due to the carbon-free combustion of hydrogen during operation while pure kerosene or sustainable aviation fuel (SAF) can be used in safety-critical situations or in the event of fuel supply issues. Previous studies have demonstrated the potential of this technology in terms of emissions performance and efficiency while also highlighting challenges related to abnormal combustion phenomena such as knocking and pre-ignition which limit the maximum achievable hydrogen energy share. However the causes of such phenomena—especially regarding the role of lubricating oils—have not yet been sufficiently investigated in hydrogen engines making this a crucial area for further development. In this paper investigations at the TU Wien Institute of Powertrain and Automotive Technology concerning the role of different engine oils in influencing pre-ignition tendencies in a hydrogen–kerosene dual-fuel engine are described. A specialized test procedure was developed to account for the unique combustion characteristics of the dual-fuel process along with a detailed purge procedure to minimize oil carryover. Multiple engine oils with varying compositions were tested to evaluate their influence on pre-ignition tendencies with a particular focus on additives containing calcium magnesium and molybdenum known for their roles in detergent and anti-wear properties. Additionally the study addressed the contribution of particles to pre-ignition occurrences. The results indicate that calcium and magnesium exhibit no notable impact on pre-ignition behavior; however the addition of molybdenum results in a pronounced reduction in pre-ignition events which could enable a higher hydrogen energy share and thus decrease CO2 emissions in the context of hydrogen dual-fuel aviation applications.

Propulsion systems in aircraft using reciprocating engines often face the challenge of managing thermal loads effectively. This problem is similar to the utilisation of polymer electrolyte membrane fuel cell systems which despite their high efficiency emit a high proportion of heat when converting chemical energy into electrical energy. Transfer of the rejected heat to the air is efficiently performed by heat exchangers. Since convective heat transfer is physically linked to fluid friction at the heat exchanger walls a pressure loss occurs. In a high-speed flow regime of the aircraft during cruise the integration of heat exchangers combined with a fan stage inside a nacelle (thus forming an impeller configuration) represents a promising approach for the dual benefit of dissipating excess heat and harnessing it for additional thrust generation through the ram jet effect. Striving for enhanced thrust performance of hydrogen electric commercial aircraft this paper presents the results of a parameter study based on a 1D-modelling approach. The focus is placed on the influence of design and operating parameters (ambient conditions fan pressure ratio diffusion ratio airside temperature difference) on performance and sizing of the proposed propulsion system. It is shown that the proposed system performs best at an altitude of 11 km and with increasing freestream Mach number. Furthermore the main challenges related to the combination of a thrust generation system with a heat exchanger in terms of sizing in particularly the required heat exchanger dimensions under different operating conditions are discussed.