Life Cycle Assessment of Vehicle Lightweighting: A Physics-Based Model To Estimate Use-Phase Fuel Consumption of Electrified Vehicles

Assessing the life-cycle benefits of vehicle lightweighting requires a quantitative description of mass-induced fuel consumption (MIF) and fuel reduction values (FRVs). We have extended our physics-based model of MIF and FRVs for internal combustion engine vehicles (ICEVs) to electrified vehicles (EVs) including hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles (BEVs). We illustrate the utility of the model by calculating MIFs and FRVs for 37 EVs and 13 ICEVs. BEVs have much smaller MIF and FRVs, both in the range 0.04–0.07 L_e/(100 km 100 kg), than those for ICEVs which are in the ranges 0.19–0.32 and 0.16–0.22 L/(100 km 100 kg), respectively. The MIF and FRVs for HEVs and PHEVs mostly lie between those for ICEVs and BEVs. Powertrain resizing increases the FRVs for ICEVs, HEVs and PHEVs. Lightweighting EVs is less effective in reducing greenhouse gas emissions than lightweighting ICEVs, however the benefits differ substantially for different vehicle models. The physics-based approach outlined here enables model specific assessments for ICEVs, HEVs, PHEVs, and BEVs required to determine the optimal strategy for maximizing the life-cycle benefits of lightweighting the light-duty vehicle fleet

Life Cycle Assessment of Vehicle Lightweighting: A Physics-Based Model of Mass-Induced Fuel Consumption

Lightweighting is a key strategy used to improve vehicle fuel economy. Replacing conventional materials (e.g., steel) with lighter alternatives (e.g., aluminum, magnesium, and composites) decreases energy consumption and greenhouse gas (GHG) emissions during vehicle use, but often increases energy consumption and GHG emissions during materials and vehicle production. Assessing the life-cycle benefits of mass reduction requires a quantitative description of the mass-induced fuel consumption during vehicle use. A new physics-based method for estimating mass-induced fuel consumption (MIF) is proposed. We illustrate the utility of this method by using publicly available data to calculate MIF values in the range of 0.2–0.5 L/(100 km 100 kg) based on 106 records of fuel economy tests by the U.S. Environmental Protection Agency for 2013 model year vehicles. Lightweighting is shown to have the most benefit when applied to vehicles with high fuel consumption and high power. Use of the physics-based model presented here would place future life cycle assessment studies of vehicle lightweighting on a firmer scientific foundation

Strategic Materials in the Automobile: A Comprehensive Assessment of Strategic and Minor Metals Use in Passenger Cars and Light Trucks

A comprehensive component-level assessment of several strategic and minor metals (SaMMs), including copper, manganese, magnesium, nickel, tin, niobium, light rare earth elements (LREEs; lanthanum, cerium, praseodymium, neodymium, promethium, and samarium), cobalt, silver, tungsten, heavy rare earth elements (yttrium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium), and gold, use in the 2013 model year Ford Fiesta, Focus, Fusion, and F-150 is presented. Representative material contents in cars and light-duty trucks are estimated using comprehensive, component-level data reported by suppliers. Statistical methods are used to accommodate possible errors within the database and provide estimate bounds. Results indicate that there is a high degree of variability in SaMM use and that SaMMs are concentrated in electrical, drivetrain, and suspension subsystems. Results suggest that trucks contain greater amounts of aluminum, nickel, niobium, and silver and significantly greater amounts of magnesium, manganese, gold, and LREEs. We find tin and tungsten use in automobiles to be 3–5 times higher than reported by previous studies which have focused on automotive electronics. Automotive use of strategic and minor metals is substantial, with 2013 vehicle production in the United States, Canada, EU15, and Japan alone accounting for approximately 20% of global production of Mg and Ta and approximately 5% of Al, Cu, and Sn. The data and analysis provide researchers, recyclers, and decision-makers additional insight into the vehicle content of strategic and minor metals of current interest

Smoke Point Measurements of Diesel-Range Hydrocarbon–Oxygenate Blends Using a Novel Approach for Fuel Blend Selection

The use of oxygenated fuels decreases particulate matter (PM) emissions from diesel engines. Studies using engines, experimental flames, and modeling have shown that the decrease in soot emissions depends on the oxygenate molecular structure. To provide a better understanding of the complex processes occurring in engines leading to PM emissions, fundamental and systematic studies of the sooting tendency trends for diesel-range hydrocarbon–oxygenate blends are needed. We present a new approach to selecting fuel blends for sooting tendency measurements that minimizes the confounding effect of dilution of highly sooting components in the base fuel by maintaining constant concentrations of those components in the blends. This novel approach is illustrated by sooting tendency (smoke point) measurements in a diffusion flame for a variety of diesel-range hydrocarbon–oxygenate blends with different molecular structures. The oxygenates included primary alcohols (1-butanol, 1-undecanol), diesters (dibutyl succinate, dibutyl maleate), esters (methyl decanoate and methyl oleate), and a glycol triether (tri­(propylene glycol) methyl ether). The hydrocarbons included an aromatic (1,2,4-trimethylbenzene), a straight-chain alkane (<i>n</i>-hexadecane), and a highly branched alkane (2,2,4,4,6,8,8-heptamethylnonane). The fuels were investigated as three-component blends, with an oxygenate in a hydrocarbon base fuel consisting of a highly sooting hydrocarbon component (1,2,4-trimethylbenzene) and a low-sooting hydrocarbon (<i>n</i>-hexadecane). The oxygen-extended sooting index (OESI) provided sooting tendency trends that were generally consistent with expectations for both hydrocarbon-only and oxygenated fuels. The dominant chemical structure factors influencing the sooting tendency of the hydrocarbons were aromaticity and branching. For the oxygenates, the primary alcohols, the saturated monoester, and the glycol triether exhibited the lowest sooting tendency, followed by the shorter-chain diesters, and then the unsaturated monoester, with unsaturation increasing the sooting tendency

Atmospheric Chemistry of (CF₃)₂CHOCH₃, (CF₃)₂CHOCHO, and CF₃C(O)OCH₃

Smog chambers with in situ FTIR detection were used to measure rate coefficients in 700 Torr of air and 296 ± 2 K of: <i>k</i>(Cl+(CF₃)₂CHOCH₃) = (5.41 ± 1.63) × 10^–12, <i>k</i>(Cl+(CF₃)₂CHOCHO) = (9.44 ± 1.81) × 10^–15, <i>k</i>(Cl+CF₃C­(O)­OCH₃) = (6.28 ± 0.98) × 10^–14, <i>k</i>(OH+(CF₃)₂CHOCH₃) = (1.86 ± 0.41) × 10^–13, and <i>k</i>(OH+(CF₃)₂CHOCHO) = (2.08 ± 0.63) × 10^–14 cm³ molecule^–1 s^–1. The Cl atom initiated oxidation of (CF₃)₂CHOCH₃ gives (CF₃)₂CHOCHO in a yield indistinguishable from 100%. The OH radical initiated oxidation of (CF₃)₂CHOCH₃ gives the following products (molar yields): (CF₃)₂CHOCHO (76 ± 8)%, CF₃C­(O)­OCH₃ (16 ± 2)%, CF₃C­(O)­CF₃ (4 ± 1)%, and C­(O)­F₂ (45 ± 5)%. The primary oxidation product (CF₃)₂CHOCHO reacts with Cl atoms to give secondary products (molar yields): CF₃C­(O)­CF₃ (67 ± 7)%, CF₃C­(O)­OCHO (28 ± 3)%, and C­(O)­F₂ (118 ± 12)%. CF₃C­(O)­OCH₃ reacts with Cl atoms to give: CF₃C­(O)­OCHO (80 ± 8)% and C­(O)­F₂ (6 ± 1)%. Atmospheric lifetimes of (CF₃)₂CHOCH₃, (CF₃)₂CHOCHO, and CF₃C­(O)­OCH₃ were estimated to be 62 days, 1.5 years, and 220 days, respectively. The 100-year global warming potentials (GWPs) for (CF₃)₂CHOCH₃, (CF₃)₂CHOCHO, and CF₃C­(O)­OCH₃ are estimated to be 6, 121, and 46, respectively. A comprehensive description of the atmospheric fate of (CF₃)₂CHOCH₃ is presented

Oxidation and Polymerization of Soybean Biodiesel/Petroleum Diesel Blends

Fuels in modern diesel engine fuel systems are exposed to highly oxidizing conditions, thus it is important to understand their degradation mechanisms. A range of chemical and physical properties was monitored during the oxidation and polymerization of soybean methyl ester biodiesel (B100), a diesel fuel (B0), and their blends (B10, B30) at 90 °C with aeration. The initial rapid oxidation of polyunsaturated fatty acid methyl esters (FAMEs) provided a transient pool of peroxides that led to the formation of aldehydes, ketones, and acids as secondary products. Monounsaturated and saturated FAMEs were oxidized concurrently with polyunsaturated FAMEs in B10, B30, and B100, but only B100 showed significant oxidation reactions continuing after the polyunsaturated FAMEs were depleted. New esters were a major oxidation product, eventually comprising 40–60% of the incorporated oxygen. Carboxylic acids and alcohols react to form esters and water, with vaporization of water driving the equilibrium toward ester formation. Polymers with ester linkages are likely contributors to the higher molecular weight materials formed and resulting increase in viscosity under these conditions

Review of the Fuel Saving, Life Cycle GHG Emission, and Ownership Cost Impacts of Lightweighting Vehicles with Different Powertrains

The literature analyzing the fuel saving, life cycle greenhouse gas (GHG) emission, and ownership cost impacts of lightweighting vehicles with different powertrains is reviewed. Vehicles with lower powertrain efficiencies have higher fuel consumption. Thus, fuel savings from lightweighting internal combustion engine vehicles can be higher than those of hybrid electric and battery electric vehicles. However, the impact of fuel savings on life cycle costs and GHG emissions depends on fuel prices, fuel carbon intensities and fuel storage requirements. Battery electric vehicle fuel savings enable reduction of battery size without sacrificing driving range. This reduces the battery production cost and mass, the latter results in further fuel savings. The carbon intensity of electricity varies widely and is a major source of uncertainty when evaluating the benefits of fuel savings. Hybrid electric vehicles use gasoline more efficiently than internal combustion engine vehicles and do not require large plug-in batteries. Therefore, the benefits of lightweighting depend on the vehicle powertrain. We discuss the value proposition of the use of lightweight materials and alternative powertrains. Future assessments of the benefits of vehicle lightweighting should capture the unique characteristics of emerging vehicle powertrains

Atmospheric Chemistry of Benzyl Alcohol: Kinetics and Mechanism of Reaction with OH Radicals

The atmospheric oxidation of benzyl alcohol has been investigated using smog chambers at ICARE, FORD, and EUPHORE. The rate coefficient for reaction with OH radicals was measured and an upper limit for the reaction with ozone was established; <i>k</i>_OH = (2.8 ± 0.4) × 10^–11 at 297 ± 3 K (averaged value including results from Harrison and Wells) and <i>k</i>_O₃ < 2 × 10^–19 cm³ molecule^–1 s^–1 at 299 K. The products of the OH radical initiated oxidation of benzyl alcohol in the presence of NO_X were studied. Benzaldehyde, originating from H-abstraction from the −CH₂OH group, was identified using in situ FTIR spectroscopy, HPLC-UV/FID, and GC-PID and quantified in a yield of (24 ± 5) %. Ring retaining products originating from OH-addition to the aromatic ring such as <i>o</i>-hydroxybenzylalcohol and <i>o</i>-dihydroxybenzene as well as ring-cleavage products such as glyoxal were also identified and quantified with molar yields of (22 ± 2)%, (10 ± 3)%, and (2.7 ± 0.7)%, respectively. Formaldehyde was observed with a molar yield of (27 ± 10)%. The results are discussed with respect to previous studies and the atmospheric oxidation mechanism of benzyl alcohol

Atmospheric Chemistry of Benzyl Alcohol: Kinetics and Mechanism of Reaction with OH Radicals

The atmospheric oxidation of benzyl alcohol has been investigated using smog chambers at ICARE, FORD, and EUPHORE. The rate coefficient for reaction with OH radicals was measured and an upper limit for the reaction with ozone was established; <i>k</i>_OH = (2.8 ± 0.4) × 10^–11 at 297 ± 3 K (averaged value including results from Harrison and Wells) and <i>k</i>_O₃ < 2 × 10^–19 cm³ molecule^–1 s^–1 at 299 K. The products of the OH radical initiated oxidation of benzyl alcohol in the presence of NO_X were studied. Benzaldehyde, originating from H-abstraction from the −CH₂OH group, was identified using in situ FTIR spectroscopy, HPLC-UV/FID, and GC-PID and quantified in a yield of (24 ± 5) %. Ring retaining products originating from OH-addition to the aromatic ring such as <i>o</i>-hydroxybenzylalcohol and <i>o</i>-dihydroxybenzene as well as ring-cleavage products such as glyoxal were also identified and quantified with molar yields of (22 ± 2)%, (10 ± 3)%, and (2.7 ± 0.7)%, respectively. Formaldehyde was observed with a molar yield of (27 ± 10)%. The results are discussed with respect to previous studies and the atmospheric oxidation mechanism of benzyl alcohol

Sustainable Mobility, Future Fuels, and the Periodic Table

Providing sustainable mobility is a major challenge that will require new vehicle and fuel technologies. Alternative and future fuels are the subject of considerable research and public interest. A simple approach is presented that can be used in science education lectures at the high school or undergraduate level to provide students with an understanding of the elemental composition of future fuels. Starting from key fuel requirements and overlaying the chemical trends evident in the periodic table, it can be demonstrated that future chemical fuels will be based on three elements: carbon, hydrogen, and oxygen. Liquid hydrocarbons are the most convenient transportation fuels because of their physical state (easier to handle than gases or solids) and their high gravimetric and volumetric energy densities. Challenges remain for storage of electricity and gaseous fuels. Recognizing the need to address climate change driven by increasing emissions of CO₂, sustainable mobility will be powered by low-CO₂ hydrogen, low-CO₂ hydrocarbons, low-CO₂ oxygenates, low-CO₂ electricity, or a combination of the above