Material and energy impacts of passenger vehicle weight reduction in the U.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Engineering Systems Division, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 117-121).Vehicle weight reduction is a known strategy to address growing concerns about greenhouse gas emissions and fuel use by passenger vehicles. We find that every 10% reduction in vehicle weight can cut fuel consumption by about 7%. In the U.S., vehicle weight reduction is essential for meeting future, more stringent fuel economy standards. New vehicles are required on average to achieve at least 34.1 miles per gallon (MPG) by year 2016, up from 28.8 MPG today. Scenarios of future vehicle characteristics and sales mix indicate that the target is aggressive. New vehicles must not only become lighter, but also forgo horsepower improvements, and progressively use advanced, more fuel-efficient powertrains, such as hybrid-electric drives. We can reduce weight by substituting some of the iron and steel used in vehicles with lighter-weight high-strength steel or aluminum, redesigning the vehicle, and/or downsizing the vehicle. Using these approaches, it is possible to achieve up to 40% (690 kg) vehicle weight reduction. However, the cost associated with manufacturing lighter-weight vehicles is a nontrivial $3 to$4 per kilogram of total weight saved. In addition, the life-cycle energy impacts of using alternative lightweight materials, which tend to be more energy-intensive to process, must also be considered. In this dissertation, the energy implications of pursuing this lightweighting strategy are explored on a vehicle life-cycle- and vehicle fleet system-level basis. A model of the energy and material flows through the evolving vehicle fleet system over time has been developed, which accounts for potential changes in future vehicle weight and material composition. The resultant changes in material production energy and fleet fuel savings, which are the main energy burdens for the entire product system - the vehicle fleet - are estimated. The new 2016 fuel economy standards and more stringent standards beyond can realize significant fuel savings of 1,550 billion liters through year 2030. However, the advanced powertrains that are expected to enter the marketplace are heavier and require more energy to produce. Their production impact may be offset by efforts to use less energy-intensive high-strength steel to lightweight new vehicles, as well as efficiency gains in material processing.by Lynette W. Cheah.Ph.D

Applying optimal choices for real powertrain and lightweighting technology options to passenger vehicles under uncertainty

This paper illustrates how cost-constrained optimization based on a set of real lightweighting and powertrain efficiency options can be used to guide decision-making for automotive manufacturers. The paper provides a method for answering the question posed by Original Equipment Manufacturers (OEMs): ‘given a maximum amount additional cost which can be passed on to consumers for fuel-saving technology with uncertain manufacturing cost, to what degree should it be spent on lightweighting versus powertrain efficiency improving technology’. The optimization is formulated as a 0–1 knapsack problem, and dynamic programming is used to find the global optimum technology combination at various levels of maximum up-front technology cost. This paper builds on previous work, which showed that for continuous marginal cost functions under uncertainty, a decision heuristic to either implement lightweighting technology or efficiency technology but not both under cost constraints was preferable. This work extends that result to provide more quantitative strategies for dealing with uncertainty, and finds that, despite uncertainty, optimum lightweighting and efficiency technology selections can be made for the real discrete cases studied. It is found that while the optimum efficiency technology set is highly sensitive to the up-front cost a consumer is willing to pay for future operational savings, lightweighting options are often selected preferentially to efficiency reduction measures. In the same sense, although both technologies are very sensitive to discount rate, lightweighting technologies are less sensitive. Fully hybridized vehicles emerge as a robust option, and, surprisingly, rank highly together with fully electric powertrains

Manufacturing-focused emissions reductions in footwear production

What is the burden upon your feet? With sales of running and jogging shoes in the world averaging a nontrivial 25 billion shoes per year, or 34 million per day, the impact of the footwear industry represents a significant portion of the apparel sector's environmental burden. A single shoe can contain 65 discrete parts that require 360 processing steps for assembly. While brand name companies dictate product design and material specifications, the actual manufacturing of footwear is typically contracted to manufacturers based in emerging economies. Using life cycle assessment methodology in accordance with the ISO 14040/14044 standards, this effort quantifies the life cycle greenhouse gas emissions, often referred to as a carbon footprint, of a pair of running shoes. Furthermore, mitigation strategies are proposed focusing on high leverage aspects of the life cycle. Using this approach, it is estimated that the carbon footprint of a typical pair of running shoes made of synthetic materials is 14 ± 2.7 kg CO[subscript 2]-equivalent. The vast majority of this impact is incurred during the materials processing and manufacturing stages, which make up around 29% and 68% of the total impact, respectively. Other similar studies in the apparel industry have reported carbon footprints of running shoes ranging between 18 and 41 kg CO[subscript 2]-equivalent/pair (PUMA, 2008; Timberland, 2009). For consumer products not requiring electricity during use, the intensity of emissions in the manufacturing phase is atypical; most commonly, materials make up the biggest percentage of impact. This distinction highlights the importance of identifying mitigation strategies within the manufacturing process, and the need to evaluate the emissions reduction efficacy of each potential strategy. By suggesting a few of the causes of manufacturing dominance in the global warming potential assessment of this product, this study hypothesizes the characteristics of a product that could lead to high manufacturing impact. Some of these characteristics include the source of energy in manufacturing and the form of manufacturing, in other words the complexity of processes used and the area over which these process are performed (particularly when a product involves numerous parts and light materials). Thereby, the work provides an example when relying solely on the bill of materials information for product greenhouse gas emissions assessment may underestimate life cycle burden and ignore potentially high impact mitigation strategies

A simulation-based evaluation of a Cargo-Hitching service for E-commerce using mobility-on-demand vehicles

Time-sensitive parcel deliveries, shipments requested for delivery in a day or less, are an increasingly important research subject. It is challenging to deal with these deliveries from a carrier perspective since it entails additional planning constraints, preventing an efficient consolidation of deliveries which is possible when demand is well known in advance. Furthermore, such time-sensitive deliveries are requested to a wider spatial scope than retail centers, including homes and offices. Therefore, an increase in such deliveries is considered to exacerbate negative externalities such as congestion and emissions. One of the solutions is to leverage spare capacity in passenger transport modes. This concept is often denominated as cargo-hitching. While there are various possible system designs, it is crucial that such solution does not deteriorate the quality of service of passenger trips. This research aims to evaluate the use of Mobility-On-Demand services to perform same-day parcel deliveries. For this purpose, we use SimMobility, a high-resolution agent-based simulation platform of passenger and freight flows, applied in Singapore. E-commerce demand carrier data are used to characterize simulated parcel delivery demand. Operational scenarios that aim to minimize the adverse effect of fulfilling deliveries with Mobility-On-Demand vehicles on Mobility-On-Demand passenger flows (fulfillment, wait and travel times) are explored. Results indicate that the Mobility-On-Demand services have potential to fulfill a considerable amount of parcel deliveries and decrease freight vehicle traffic and total vehicle-kilometers-travelled without compromising the quality of Mobility On-Demand for passenger travel.Comment: 19 pages, 4 tables, 7 figures. Submitted to Transportation (Springer

Pf7: an open dataset of Plasmodium falciparum genome variation in 20,000 worldwide samples

We describe the MalariaGEN Pf7 data resource, the seventh release of Plasmodium falciparum genome variation data from the MalariaGEN network.  It comprises over 20,000 samples from 82 partner studies in 33 countries, including several malaria endemic regions that were previously underrepresented.  For the first time we include dried blood spot samples that were sequenced after selective whole genome amplification, necessitating new methods to genotype copy number variations.  We identify a large number of newly emerging crt mutations in parts of Southeast Asia, and show examples of heterogeneities in patterns of drug resistance within Africa and within the Indian subcontinent.  We describe the profile of variations in the C-terminal of the csp gene and relate this to the sequence used in the RTS,S and R21 malaria vaccines.  Pf7 provides high-quality data on genotype calls for 6 million SNPs and short indels, analysis of large deletions that cause failure of rapid diagnostic tests, and systematic characterisation of six major drug resistance loci, all of which can be freely downloaded from the MalariaGEN website

Factor of 2 : halving the fuel consumption of new United States Automobiles by 2035

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 63-64).This thesis examines the vehicle design and sales mix changes necessary to double the average fuel economy of new U.S. cars and light-trucks by model year 2035. To achieve this factor of two target, three technology options that are available and can be implemented on a large scale are evaluated: (1) channeling future vehicle technical efficiency improvements to reducing fuel consumption rather than improving vehicle performance, (2) increasing the market share of diesel, turbocharged gasoline and hybrid electric gasoline propulsion systems,and (3) reducing vehicle weight and size.The illustrative scenarios demonstrate the challenges of this factor-of-two improvement -- major changes in all these three options would need to be implemented before the target is met. Over the next three decades, consumers will have to accept little further improvements in acceleration performance, a large fraction of new light-duty vehicles sold must be propelled by alternative powertrains trains, and vehicle weight must be reduced by 20-35% from today. Theadditional cost of achieving this factor-of-two target would be about 20% more than a baseline scenario where fuel consumption does not change from today's values, although these additional costs would be recouped within 4 to 5 years from the resulting fuel savings.Thus, while it is technically feasible to halve the fuel consumption of new vehicles in 2035, aggressive changes are needed and additional costs will be incurred.Results from this study imply that continuing the current trend of ever increasing performance and size will have to be reversed if significantly lower vehicle fuel consumption is to be achieved.by Lynette W. Cheah.S.M

Supporting Information - Ross and Cheah 2018.xlsx

Tables and supplementary information for Ross, S.A. and L. Cheah (2018) Uncertainty quantification in life cycle assessments: Exploring distribution choice and greater data granularity to characterize product use, Journal of Industrial Ecology

Materials Flow Analysis and Dynamic Life-cycle Assessment of Lightweight Automotive Materials in the US Passenger Vehicle Fleet

To achieve better fuel economy, automakers are seriously considering vehicle weight and size reduction. This is achieved by using lighter-weight materials like high-strength steel and aluminum, better vehicle design, and offering smaller vehicle models. To consider the effectiveness of these approaches, it is important to take into account the dynamic life-cycle energy and environmental impacts. For instance, primary aluminum requires almost four times more energy to produce than steel today. Expected efficiency improvements in material processing would modify this ratio over time. Examining the impact of lightweighting on the overall vehicle fleet system- level, as opposed to a single vehicle-level, also reveals insights on the timing and degree of the impact reduction achieved

Meeting U.S. passenger vehicle fuel economy standards in 2016 and beyond

New fuel economy standards require new U.S. passenger vehicles to achieve at least 34.1 miles per gallon (MPG) on average by model year 2016, up from 28.8 MPG today. In this paper, the magnitude, combinations and timings of the changes required in U.S. vehicles that are necessary in order to meet the new standards, as well as a target of doubling the fuel economy within the next two decades are explored. Scenarios of future vehicle characteristics and sales mix indicate that the 2016 mandate is aggressive, requiring significant changes starting from today. New vehicles must forgo horsepower improvements, become lighter, and a greater number will use advanced, more fuel-efficient powertrains, such as smaller turbocharged engines, hybrid-electric drives. Achieving a factor-of-two increase in fuel economy by 2030 is also challenging, but more feasible since the auto industry will have more lead time to respond. A discussion on the feasibility of meeting the new fuel economy mandate is included, considering vehicle production planning realities and challenges in deploying new vehicle technologies into the market.Energy efficiency Technology diffusion CAFE standards