Air quality trade-offs of a rapid expansion of personal electric vehicles in China.

Abstract:

Electric vehicles (EVs) have long been touted as an effective way to reduce the environmental impacts of road transportation. In China, they are at the center of a large program of subsidies and incentives to promote rapid adoption. However, while substituting gasoline cars with EVs reduces CO₂ and air pollutant emissions from transportation and refineries, it requires increased power generation. To quantify the resulting climate and air quality trade-off in China, we develop a high-resolution power grid model that estimates, for each unit, hourly generation and emissions under four EV charging scenarios in 2020. We use the GEOS-Chem atmospheric chemistry transport model to quantify regional changes in air pollution (PM_2.5 and ozone) and resulting health impacts.

We find that under the projected penetration of EVs in China by the end of 2020, the effect of reduced on-road and refineries emissions outweighs that of increased power emissions. This results in 1,900 fewer early deaths per year, and decreases CO₂ emissions by 2.4 Mtons per year for the current grid composition. Nonetheless, EV deployment has a detrimental impact on air quality in 9 provinces, particularly in Southern China. In addition, smart charging is estimated to enhance the air quality improvements by 26% nationally but has no significant impacts on CO₂ emissions (<1% difference with slow charging). Smart charging with a carbon price for the EV load would increase the net air quality benefit to 3,800 avoided premature mortalities per year and a 4.4 Mtons decrease in annual CO₂ emissions.

Additionally, the air quality and climate benefits associated with EV deployment are increasing. By 2022, the positive impacts of EVs on premature mortalities would be increased by 26% in the slow charging scenario, while net CO₂ emissions would further reduce by 4% compared to 2017. Recent policy developments aimed at reducing refineries emissions would however reduce the benefits of EV deployment on air quality and CO₂ emissions, unless cleaner power generation is deployed to match the EV load, in which case EVs will continue to be net beneficial to air quality and climate, and an asset for transportation sustainability.