Decarbonization potential of future sustainable propulsion-A review of road transportation

Modern automotive propulsion technologies must achieve the highest CO2 reduction potential quickly to abide by the requirements of the Paris Climate Agreement. A collective utilization of renewable fuels, e-fuels, hydrogen, and electrical energy will be able to meet different mobility and transport requirements in an optimal and CO2-neutral approach. The well-to-wheel greenhouse gas emissions of a propulsion system are determined by two factors, that is, the energy efficiency of the system and the carbon intensity of the energy source. Regardless of the CO2 emission generated during the battery manufacturing and recycling process, the carbon intensity of the battery electric vehicles during operation is mainly decided by the carbon intensity of the electricity being consumed. The relatively low fleet ratios of battery electric and hydrogen-powered vehicles and the massive remaining useful life of current internal combustion engine vehicle stock limit their impact on decarbonization in the near term. The expansion of charging infrastructure requires significant acceleration for the success of large-scale and rapid electric vehicle adoption. For internal combustion engines, the focus is to further improve energy efficiency and the adoption of low-to-zero carbon renewable fuels. Hybrid and plug-in hybrid vehicles are demonstrating the advantages of combining state-of-the-art technologies to reduce both energy consumption and carbon emissions. In this review, the present status of propulsion systems is reviewed in detail, considering both the market penetration and well-to-wheel carbon emissions. The decarbonization potentials of various propulsion systems are then discussed.