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article imageHow electric vehicles are charged in China affects air quality

By Karen Graham     May 3, 2018 in Environment
Beijing - Researchers from Harvard University and Tsinghua University in Beijing found that private electric vehicles in China can have a positive effect on CO2 reduction if owners can be incentivized to slowly charge vehicles during off-peak hours.
Electric vehicles play a key role in China's efforts to improve air quality and reduce harmful greenhouse gas emissions. Yet with all the press being given to China's embrace of renewables like wind and solar power, the majority of the country's electricity still comes from coal-fired power plants — leaving many people to question just how effective this strategy is.
The team of researchers investigated the possibility pf electric cars emitting more CO2 and conventional pollutants in China, despite them being greener to drive. The researchers examined the environmental implications of investments in different types of electric vehicles and the different modes (fast or slow) for charging under a range of different wind penetration levels.
The research was published in the journal Nature Energy April 30, 2018.
Last year Beijing enjoyed the best air quality on recent record
Last year Beijing enjoyed the best air quality on recent record
It is important to note that in China, buses and taxis make a significant contribution to nitrous oxide emissions, a major precursor to air pollution. China launched a campaign last October to reduce average concentrations of PM2.5 by between 10-25 percent in 28 northern cities in an effort to hit 2013-2017 air quality targets.
And while the Environmental Ministry has the authority to demand cities reduce traffic, cut industrial output and curb coal use, getting rid of an industry still based on coal has its own problems. And one of these problems is trying to get electric car users to use a slow-charging mode on their EVs.
Slow-charging reduces harmful emissions
The explanation for slow-charges over fast-charges is really quite simple. The research team discovered that to properly maximize the benefits of renewables, it is critical that EV recharging is done properly. To explain, remember that China is a huge country with crowded major cities.
There are 110 12-meter all-electric buses equipped with Microvast fast charge batteries “ready to ...
There are 110 12-meter all-electric buses equipped with Microvast fast charge batteries “ready to go” in Lianyungang, China. Three "fast" combined: "Fast Traffic Track + fast charge + fast charging stations.
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, played a huge roll in the use of wind energy.
The team found that most EV recharging in the fast 30-minute or less mode occurred during the peak hour of electricity 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.
Officials have been under pressure to deliver results in the fight against smog  which has become a ...
Officials have been under pressure to deliver results in the fight against smog, which has become a health hazard across swathes of China
As for Beijing's fleet of public vehicles, like buses and taxis, the city's 30,000 buses and 66,000 taxis are responsible for almost 20 percent of total NOX emissions, equivalent to the contribution from 8.2 million private vehicles. The study notes that electrifying buses and taxis would lead to a significant reduction in NOX emissions while improving air quality.
"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 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.
“This strategy could also be applied to cities across the world that have a significant source of electricity from coal.”
More about China, Harvard research, electric vehicles, CO2 Emissions, slowcharge
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