Hyung Chul Kim
Ford
Hyung Chul Kim is a LCA Specialist at Ford Motor Company investigating broad range of topics related to life cycle assessment and sustainability engineering on automobiles. Recent topics include life cycle benefits of lightweight and bio-based materials, LCA of EV traction batteries, and life cycle water use of ICEVs and EVs. He received a PhD in Natural Resources and Environment at the University of Michigan, Ann Arbor, MI.
Vehicle lightweighting is regarded as a key strategy to improve fuel economy and reduce climate change impact. The most common lightweight materials include aluminum, advanced high strength steel, carbon fiber composites, and magnesium that often require more energy and emissions than conventional steel during the material production stage. A life cycle assessment (LCA) based approach is necessary to determine the net benefits of substituting lightweight materials for conventional steel.
Vehicle LCAs indicate that the use phase accounts for the greatest amount, i.e., 60-90% of energy and greenhouse gas (GHG) emissions in the life cycle. Estimating the reduced use-phase energy consumption upon vehicle lightweighting presents an ultimate challenge for LCA practitioners. Lacking comprehensive tools, most literature LCAs rely on a heuristic approach to determine mass-related fuel reduction values (FRVs). As a result, LCAs of vehicle lightweighting often embed a substantial degree of uncertainties by ignoring vehicle characteristics such as power, type, and class.
To reduce uncertainties in lightweighting LCAs, we recently introduced a physics-based model to estimate mass-induced fuel consumption (MIF) and fuel reduction values (FRVs) that can be applied to specific vehicle models of internal combustion engine vehicles (ICEVs) and electrified vehicles (EVs) (Kim and Wallington 2016). Our model utilizes public domain coast-down data, i.e., rolling, rotating, and aerodynamic coefficients along with fuel economy values in the EPA database to estimate MIF values of 0.22−0.43, 0.09-0.24, 0.07-0.21, and 0.04-0.07 L/(100 km 100kg), for ICEVs, Hybrid Electric Vehicles (HEVs), Plug-in Hybrid Electric Vehicles (PHEVs), and Battery Electric Vehicles (BEVs), respectively. Model specific evaluations are necessary for accurate assessment.
In this study, we use our mass induced fuel consumption (MIF) model to compare the potential life cycle GHG emissions benefits of lightweighting across vehicle types and characteristics. First, we will identify key technical factors of determining MIF/FRVs such as powertrain efficiency and rolling resistance. This will allow us to assess MIF/FRVs across vehicle types and characteristics including class, engine size, and powertrain type. Then, the values will be evaluated for exogenous factors such as utility factors and driving patterns. Preliminary results indicate that vehicles with a large engine or high rolling coefficient have a greater potential of fuel reduction per kg of lightweighting. For PHEVs, utility factor is a key parameter determining MIF/FRVs.
In the next step, we will evaluate the potential life cycle benefits of model year 2017 ICEVs and EVs based on the MIFs/FRVs and lightweighting scenarios for a grille opening reinforcement (GOR) with magnesium, carbon-fiber composites, or glass-fiber composites replacing conventional steel. The life cycle GHG emissions from these material selection options will be evaluated across vehicle types and characteristics discussed above. Additional variables such as electric grid mixture will be considered. Finally, on the basis of modeling results, we will present optimal lightweighting strategies by identifying vehicle models that maximize the life cycle environmental benefits per unit mass reduction.
