Fast EV Charging is Linked to Higher Carbon Emissions

A study by the Harvard School of Engineering and Applied Sciences and Tsinghua University in Beijing finds a link between fast charging and higher carbon emissions, The study focuses on China, which still derives much of its electricity from coal, but the lessons learned have global implications.

The research demonstrates that private electric vehicles in China can have a positive effect on CO2 reduction if they are charged slowly during off-peak hours when renewable energy from renewables like wind turbines is available. On the other hand, fast charging during peak demand periods uses more electricity from coal-fired generating plants, which negates many of the benefits of driving an electric car. The researchers recommend a system of incentives to encourage off-peak charging.

The researchers used real time power demand data and driving patterns for Beijing and its suburbs to develop a comprehensive model of the energy system. They found that fast charging often occurs during peak demand hours.

That, in turn, causes more coal-fired plants to come online. Once they are fired up, it is not easy to shut them down, so they stay online longer then necessary, which constrains the benefits of renewables like wind power.

If people were incentivized to wait until evening and charge their vehicles in the slow-charge mode, which takes hours, the power load could take advantage of wind energy available during off-peak hours. The problem, of course, is human nature. People want fast.

This study has a clear message for other nations that it is critically important to manage electric vehicle charging properly or else the benefits of renewables will be lost.