Investigating the potential to influence the electric vehicle users' recharging behaviour to reduce well to wheel carbon emissions

Abstract

The need to cut carbon emissions from cars and small vans is becoming an increasingly important issue. In the UK, it is anticipated that the electric vehicle (EV) will play a key role in meeting the 80% emissions reduction target in the Climate Change Act 2008. Although there are no emissions at their point of use, the equivalent emissions from an electric vehicle are dependent on the electricity used to recharge the EV's battery. This electricity is generated from coal (910gCO2/kWh), natural gas (400gCO2/kWh), nuclear (zero emissions) and renewables (zero emissions). The contribution of these power sources to the overall energy mix varies depending on the time of day; meaning that the average carbon content varies from an 'off peak' minimum of 366gCO2/kWh at 03:00am to an 'on peak' 466gCO2/kWh at 18:00pm. Therefore, depending on when an EV is recharged, the effective carbon content of the electricity stored in the battery varies. This study aims to quantify the carbon emissions and power demands of electric vehicles when in everyday use, by correlating the times of day when drivers recharge their cars with the carbon content of electricity at that time. Data was collected through the Switch EV trial in North East England, which see 44 electric vehicles employed in the region for three years. Analysis of the behaviour of these drivers over a six month period indicates that the average carbon content of the electricity transferred into an EV during recharging is 436gCO2/kWh. Changes in charging behaviour could lead to a 70gCO2/kWh reduction in emissions.