Energy Consumption and Carbon Emissions of Electric Vehicles Under Real Driving Conditions

Abstract

This thesis investigates the energy consumption of electric vehicles (EVs) under realworld driving conditions and the associated carbon emissions during charging, which are influenced by electricity grid mix, travel demand and energy consumption. Existing methods of road measurements of EVs used unscheduled trips, making the results particular to the test location and difficult to compare. Besides shifting to EVs, additional actions enable further decarbonisation of road transport resulting from changes in travel demand and charging flexibility. The analysis uses data collected from an EV operated on UK roads for almost four years, and the evaluation of the energy consumption was carried out following a real driving cycle (RDC) schedule. The results show EV specific energy consumption (SEC) is highly influenced by changes in ambient temperature, nearly doubling from operation at moderate temperatures of around 20°C to operation at temperatures as low as 0°C due to the corresponding loads required by heating and air conditioning systems. Short trips below 16 km caused nearly 10% SEC average increase in comparison with longer ones, showing more awkward effects in motorway operation with SEC rise up to 29%. Traffic conditions and driving behaviour also demonstrated a high influence on SEC, increasing it by 40% and 16%, respectively, from the most favourable to the most unfavourable condition. A model was developed to investigate carbon emissions projections of passenger vehicles considering the expected large EV market penetration and the impact of changes in road traffic using a set of scenarios based on vehicle ownership and usage. A reduction of 22% in EVs cumulative carbon emissions by 2050 can be achieved by targeting 23% lower vehicle number and 17% usage, while an opposite scenario increases EV cumulative carbon emissions by 28%. The regional differences in energy consumption and carbon emissions were modelled under different charging scenarios, showing carbon emission reduction varies from 4% to 33% between the regions when switching to delayed charging, shifting the charging outside peak hours. An optimised charging that moves charging events to periods of low grid carbon intensity reduces carbon emissions from 6% to 55%, affected by region grid carbon intensity and energy consumption.