Environmental impact of electric vehicles in China? It depends on how they are charged

Environmental impact of electric vehicles in China? It depends on how they are charged
Traffic and smog in Beijing. Credit: Harvard John A. Paulson School of Engineering and Applied Sciences

Electric vehicles play a key role in China's plan to improve air quality and reduce CO2 emissions but, with the majority of China's electricity still coming from coal-fired power plants, many question just how effective this strategy will be.

Now, researchers from Harvard University and Tsinghua University in Beijing found that private in China can have a positive effect on CO2 reduction if owners can be incentivized to slowly charge vehicles during off-peak hours, allowing for more effective use of wind-generated . Quickly charging vehicles in the higher energy "fast mode", on the other hand, can be counterproductive.

Meanwhile, buses and taxis In China make a significant contribution to NOX emissions, a major precursor for . The team determined that electrifying the bus and taxi fleet offers the most effective option for improving air quality.

The research is published in Nature Energy.

"This research offers a more nuanced strategy for reducing CO2 emissions and improving air quality in China," said Michael B. McElroy, the Gilbert Butler Professor of Environmental Studies at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Department of Earth and Planetary Sciences and co-author of the research.

"It is critically important that electric charging is managed properly to maximize the benefits of renewables," said Xinyu Chen, Research Associate in Environmental Science and Engineering at SEAS and co-author of the study.

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 how electric vehicles are charged—whether in the low-energy slow mode or high-energy fast mode—plays a significant role in the integration of wind energy. Typically, vehicle charging in the 30-minutes or less fast mode occurs during hours of peak power demand. As a result, peak power demand is increased, triggering additional coal generators to come online. With these generators operational at night, the opportunity to take advantage of available wind power is reduced.

"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," said Chris P. Nielsen, Executive Director of the Harvard China Project and co-author of the study.

In terms of lowering air pollution, the researchers found that the gas- or diesel-fueled fleet of public vehicles—about 30,000 buses and 66,000 taxis—is responsible for nearly 20 percent of total NOX emissions, equivalent to the contribution from 8.2 million private vehicles. Electrifying the fleet of buses and taxis in Beijing would significantly reduce total NOX emissions and increase .

"Electrifying the public fleet and introducing incentives to charge personal electric vehicles at off-peak times would be the most effective strategy to reduce NOX and CO2 emissions in Beijing," said McElroy. "This strategy could also be applied to cities across the world that have a significant source of electricity from coal."


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More information: Xinyu Chen et al, Impacts of fleet types and charging modes for electric vehicles on emissions under different penetrations of wind power, Nature Energy (2018). DOI: 10.1038/s41560-018-0133-0
Provided by Harvard John A. Paulson School of Engineering and Applied Sciences
Citation: Environmental impact of electric vehicles in China? It depends on how they are charged (2018, May 1) retrieved 23 October 2018 from https://techxplore.com/news/2018-05-environmental-impact-electric-vehicles-china.html
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User comments

May 01, 2018
Yeah zero impact since they are going to use coal. They are building a coal plant per week while America is dumped on by liberal hate groups and we are left begging for enough energy for our needs. we have enough coal reserves for 900 years. We need to begin to see how we can use them safely. Not build coal plants is not the right move. The left is so sick and wrong on this issue.

May 01, 2018
How was the 'lectric generated for the freaking mining, milling, processing, and creating the steel, aluminum, battery, electrical components, et. al.

Coal.

Carry on.

May 01, 2018
It is a good step forward. If anything, the coal stack can be filtered on industrial scale. But amount of toxic smoke on the street where people breath is much improved. In long run, the electric cars will be charged by a few hundreds nuclear power plants in works.
While you two coal miners will still dig coal. And ride a horse carriage to the dump.

May 02, 2018
At some point all of the coal and oil burning plants will be dismantled, then all of these cars will get there power from the sun. People will then realize that this whole fossil fuel business was one long scam.

May 02, 2018
Lol georgie porgie (aka antigoracle sockpuppet)and his other sockpuppet shoot the potty miss) is already black (swinging trees in the local park) but the coal they digging puts on that extra tint.

May 02, 2018
"
While you two coal miners will still dig coal. And ride a horse carriage to the dump.
"
lol

May 14, 2018
Putting the electric car before the low emissions electricity to charge it!

The scale of investment in low emissions electricity by China continues to grow - and by the time significant numbers of EV's (lots of e-bikes as well as cars) are in use the proportion of RE in the mix will have grown. The overall emissions reductions will occur when they are both in high use but having a lot of EV's already in place first won't hurt.

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