Environmental impacts of hybrid, plug-in hybrid, and battery electric vehicles—what can we learn from life cycle assessment?

PurposeThe purpose of this review article is to investigate the usefulness of different types of life cycle assessment (LCA) studies of electrified vehicles to provide robust and relevant stakeholder information. It presents synthesized conclusions based on 79 papers. Another objective is to search for explanations to divergence and “complexity” of results found by other overviewing papers in the research field, and to compile methodological learnings. The hypothesis was that such divergence could be explained by differences in goal and scope definitions of the reviewed LCA studies.MethodsThe review has set special attention to the goal and scope formulation of all included studies. First, completeness and clarity have been assessed in view of the ISO standard’s (ISO 2006a, b) recommendation for goal definition. Secondly, studies have been categorized based on technical and methodological scope, and searched for coherent conclusions.Results and discussionComprehensive goal formulation according to the ISO standard (ISO 2006a, b) is absent in most reviewed studies. Few give any account of the time scope, indicating the temporal validity of results and conclusions. Furthermore, most studies focus on today’s electric vehicle technology, which is under strong development. Consequently, there is a lack of future time perspective, e.g., to advances in material processing, manufacturing of parts, and changes in electricity production. Nevertheless, robust assessment conclusions may still be identified. Most obvious is that electricity production is the main cause of environmental impact for externally chargeable vehicles. If, and only if, the charging electricity has very low emissions of fossil carbon, electric vehicles can reach their full potential in mitigating global warming. Consequently, it is surprising that almost no studies make this stipulation a main conclusion and try to convey it as a clear message to relevant stakeholders. Also, obtaining resources can be observed as a key area for future research. In mining, leakage of toxic substances from mine tailings has been highlighted. Efficient recycling, which is often assumed in LCA studies of electrified vehicles, may reduce demand for virgin resources and production energy. However, its realization remains a future challenge.ConclusionsLCA studies with clearly stated purposes and time scope are key to stakeholder lessons and guidance. It is also necessary for quality assurance. LCA practitioners studying hybrid and electric vehicles are strongly recommended to provide comprehensive and clear goal and scope formulation in line with the ISO standard (ISO 2006a, b)

Methodological Approaches to End-Of-Life Modelling in Life Cycle Assessments of Lithium-Ion Batteries

This study presents a review of how the end-of-life (EOL) stage is modelled in life cycle assessment (LCA) studies of lithium-ion batteries (LIBs). Twenty-five peer-reviewed journal and conference papers that consider the whole LIB life cycle and describe their EOL modelling approach sufficiently were analyzed. The studies were categorized based on two archetypal EOL modelling approaches in LCA: The cutoff (no material recovery, possibly secondary material input) and EOL recycling (material recovery, only primary material input) approaches. It was found that 19 of the studies followed the EOL recycling approach and 6 the cutoff approach. In addition, almost a third of the studies deviated from the expected setup of the two methods by including both material recovery and secondary material input. Such hybrid approaches may lead to double counting of recycling benefits by both including secondary input (as in the cutoff approach) and substituting primary materials (as in the EOL recycling approach). If the archetypal EOL modelling approaches are not followed, it is imperative that the modelling choices are well-documented and motivated to avoid double counting that leads to over- or underestimations of the environmental impacts of LIBs. Also, 21 studies model hydrometallurgical treatment, and 17 completely omit waste collection

SOFC Modeling in Femlab

This report describes a graduate thesis project for the Master of Science diploma from the Engineering Physics program at Chalmers University of Technology. It has been performed at Volvo Technology Corporation with the primary aim to model a given Solid Oxide Fuel Cell design, the Rutquist cell, in Femlab. The model is intended to provide information on current-voltage characteristics, power development and the temperature profile, both during startup and operation. The secondary purpose was to evaluate the suitability of Femlab for this kind of task. The project was initiated with a bibliographic research, which gave several theories and parameters useful for modeling the different processes in the SOFC design. These models were then implemented in Femlab. Two separate modes were created where the startup and the operation of the cell respectively, were simulated. The cell was assumed to be a part of a larger system and receive hot gases from a fuel reformer. The heating in the startup process was achieved by letting warm gas, 1073 K, enter the electrodes via the gas channels. The chemical reactions were assumed to begin when all parts of the structure had reached 1023 K. The calculations showed that the heating to this temperature takes about one minute, and that most of the heat exchange takes place in the electrodes. The resulting temperature profiles from the operation mode model demonstrate that the temperature is in the same range as other SOFC structures and that the design is very compact. The dimensions of a cubic stack developing 10 kW at maximum power would be less than one cubic decimeter. The computational software Femlab has advantages, but also several shortcomings. Among the advantages are the flexibility in the module based system and the short learning period needed for solving simple problems. The weaknesses include the necessity of good knowledge of numerical solution methods, since many settings have to be adjusted when the models become more complex; especially the error report system is poor and occasionally even missing. The report also presents the theory of the physical and chemical processes ceramic fuel cells. Suggestions for improvements and the effects of the delimitations and approximations used in the modeling work are discussed. Finally, recommendations for future work are put forward

The role of life cycle assessment in evaluating alternatives for electrification of roads and long haul trucks in Sweden

In September 2012, the Swedish Government presented a 1.3 billion SEK investment for the years 2013-2016 targeted on improving the infrastructure for transportation of iron ore powder between the mine in Kaunisvaara and Svappavaara, where it is transferred to train. This decision was preceded by an official report from the Swedish Transport Administration investigating necessary road reconstruction along with alternatives for electrification of the vehicles used. As a result, a new road of 140 kilometers will be constructed and at the same time serve as test project for electric road technologies in Sweden, with the initial focus set on heavy duty trucks. Scania CV AB is the supplier of the 90 ton long haul trucks which will transport the iron ore powder, and also an active part in the rapidly evolving area of electric roads in Sweden. In August 2012, the company’s Hybrid Systems Development Department initiated a life cycle assessment (LCA) on this case, set up in the form of a master’s thesis. The LCA study compares three different drivetrain alternatives for the heavy long haul trucks. In essence, the cradle to grave cycle impact of a set of additional components is compared with the effect of the reduced total energy use of fuel and electricity in the well-to-wheel phase, for a conventional truck, a hybrid (made more efficient by integrating electric propulsion) and a hybrid with external power supply from the road. The aim of the study is to evaluate the environmental impact of the three alternatives and to demonstrate how it changes over the different life cycle phases. The motive of Scania has been to increase their knowledge of the environmental impacts of drivetrain electrification, and also to provide support for internal decisions and future strategies on how to meet energy efficiency targets. The idea is also to present the results within the test project working group and thereby contribute to the overall project evaluation. The aim of this presentation is to point out that the increased governmental focus on electric roads in Sweden and Scania’s need to understand the effect of this technology in an environmental systems perspective, has given LCA a role in the evaulation. Hence, the results and conclusions of the LCA will be presented. Finally, the opportunities and limitations of LCA as a learning tool when applied on this type of emerging technology at a department with no prior LCA experience will be discussed

Life cycle assessment of battery electric buses

Different Li-ion battery technologies and sizes are used in battery electric buses (BEBs), but little is known about the environmental effect of various battery technology and sizing alternatives. In a cradle-to-grave life cycle assessment of seven BEBs, we consider three battery technologies combined with relevant pack sizes to evaluate the size and range effect. The environmental performance of the BEBs was assessed over the typical length of a bus tender of 10 years as well as an extended lifetime of 20 years. Across six environmental impact categories we found that the size and range effect depends to a large extent on the performance of the battery technology and that a smaller battery size of the same technology is not necessarily environmentally preferable. Furthermore, extending the BEB lifetime from 10 to 20 years changes the environmental performance as well as relative contributions to environmental impact potentials for the various BEB alternatives