The impact of lightweighting and battery technologies on the sustainability of electric vehicles: A comprehensive life cycle assessment

Abstract

We present a comprehensive analysis of the greenhouse gas (GHG) emissions of two battery electric vehicles (BEVs) using detailed teardown data and contrast them with those of four internal combustion engine vehicles (ICEVs). We used the teardown data to calculate the production and recycling phases as well as for the vehicle dynamics modeling and estimating the utilization phase GHGs. After validating the models and establishing a baseline, we analyzed the effect of new trends on their net carbon footprint. Specifically, we considered lightweighting, battery technology, and charging technologies and showed the tradeoff between longer-range BEVs and their sustainability as a green alternative to ICEVs. The GHGs were calculated based on a life cycle assessment, including the vehicles' production, utilization, and disposal/recycling life. The GHGs of the production phase were calculated using detailed vehicle teardown data rather than general assumptions about the vehicles' material composition. Similarly, the utilization phase GHGs were estimated by first creating accurate dynamic models of the vehicles and validating them against vehicle test data. Then, we analyzed the effect of charging type and electricity source on the sustainability of these technologies. These studies showed that the average (mixed) US electricity source accounts for about 50 % of GHGs, and changing charging from household to station or supercharging can save about 8 % of GHG emissions. Next, we studied the effect of battery technology and lightweighting on EVs' net GHGs. OEMs have exploited both of these options to reduce the car's weight and improve its electrical consumption during the utilization phase (driving). Our study showed that while the higher energy density of battery technologies like NMC and NCAs is attractive for reducing the vehicle's weight and increasing its range, the use of rare materials significantly increases GHG emissions during production. Similarly, we showed that lightweighting by substituting steel with aluminum alloys (such as giga-casting) adds more production GHGs that significantly offset the savings in electrical consumption achieved during the vehicle's lifetime. Therefore, this study proposes three pivotal considerations in the design and utilization of electric vehicles: battery material selection, trade-off analysis for vehicle lightweighting, and adoption of efficient charging methods and energy sources, all of which aim to reduce their overall global carbon footprint.