Geographical Differences of Electricity Supply in Environmental Impact Assessment of Electric Vehicles

Electric vehicles (EVs) are developed to address the global issues of fossil fuel depletion and environmental deterioration from the transportation sector. While EVs are much more environmentally benign than conventional vehicles, they still generate some environmental impacts throughout their life cycle from raw material extraction to end of life. Among various life cycle phases, the environmental impacts of EVs are mainly generated during their usage phase. Since EVs are driven by rechargeable batteries, the sources of environmental impacts of EVs in usage phase are mainly from the electricity consumed by battery charging. However, different regions in the U.S. employ different energy technologies for electricity generation and accordingly the environmental impacts of EVs in their operations at different regions can be largely different. In this study, we report our preliminary investigations on the geographical factor in evaluating the greenhouse gas emissions from EVs operations. Four cities are selected as representatives of different U.S. regions, including Washington D.C., Los Angeles, Pittsburgh and Phoenix. The study is conducted on two representative EVs models: Nissan Leaf and Chevrolet Volt. The results demonstrate that geographical factor plays an important role in the GHG emission generation of EVs. The highest amount of GHG emission as demonstrated on Chevrolet Volt is 3,869 kg CO₂ eq per year in Pittsburgh, while the smallest GHG emission is only 2,125 kg CO₂ eq per year with Nissan Leaf in Los Angeles, based on the averaged U.S. annual driving mileages.