Decarbonised Powertrains and Emission Control in Transportation

Dear Colleagues,

In an effort to reduce powertrain systems’ impact on the environment, a significant reduction of CO₂ emissions is required in upcoming years, with the aim of a 15% reduction by 2025 and 37.5% reduction by 2030. In this sense, two main strategies are being pursued. On one hand, powertrain electrification, including purely electrical (battery or fuel-cell based) as well as hybrid powertrains, is currently seen as the main path for light- and medium-duty vehicles. On the other hand, advanced combustion concepts and low- or zero-carbon fuels are being considered for heavier sectors, including long-haul trucks, aircraft and maritime applications.

Each strategy has its own challenges. Battery-electric powertrain development is focused on increasing power density and durability while increasing safety, particularly mitigating the risk of thermal runaway events. In the case of fuel-cell systems, the aims are to reduce cost through reduced Pt content in the catalyst and new materials for the bipolar plates, and also to improve their transient response and mitigate the subsequent degradation mechanisms. For hybrid-electric vehicles, which generally use a gasoline spark-ignition engine, one of the main challenges is related to the aftertreatment deactivation linked to the continuous starting and stopping of the thermal engine, which can lead the aftertreatment to fall below the activation temperature by the time the engine is restarted. Moreover, more frequent operation under near cold-start conditions inside the cylinders can increase the production of unburned hydrocarbons and particulate emissions.

In the case of advanced combustion concepts and fuels, the two main concerns are as follows: on one hand, the new combustion setup must be optimized in order to provide the maximum possible emission control on the combustion side. On the other hand, the composition of the exhaust gases can be dramatically changed, affecting the boundaries for the operation of the aftertreatment system needed to abate the gaseous emissions. For instance, new engine concepts based on hydrogen or ammonia combustion would produce aftertreatment gases mainly composed of nitrogen, water, oxygen, NOx and NH₃. Instead, other concepts such as oxy-fuel combustion would not produce NOx if all N₂ is removed, but HC/CO management would be needed if novel carbon-based (such as e-fuels) were used. In both cases, new a proposals aimed at reducing these emissions for new exhaust-gas compositions (including a highly humid environment) may be required.

This Special Issue encourages works from both industry and academia that focus on the analysis of pollutant emissions formation and control with regard to decarbonized powertrain platforms. Potential topics include (but are not limited to):

• Novel materials for battery and fuel cell electric vehicles.
• Analysis of thermal runaway events for battery-electric powertrains.
• Fuel-cell degradation mechanisms and their mitigation.
• Development and emissions impact of novel combustion strategies.
• Combustion and emissions characterization with alternative fuels (biofuels; e-fuels; H₂; NH₃, etc.)
• Powertrain architecture based on oxy-fuel combustion concepts.
• Hybrid powertrain emissions in driving cycles.
• Emissions characterization in engine cold-start operation.
• Characterization of exhaust aftertreatment systems.
• New modeling approaches in powertrain applications: from system level to component level.
• OBD and control strategies.
• New catalysts formulations for emission control.
• Health and environmental impact of vehicle emissions.
• Life-cycle analysis (LCA) and total ownership cost (TCO) for decarbonized powertrains.

Dr. Pedro Piqueras
Dr. Joaquin de la Morena
Topic Editors