Over the past few years, millions of new electric vehicles have hit the roads in China, with the majority adopted in its richer cities.
While electric vehicles have huge benefits compared with the carbon emissions from petrol- and diesel-fueled cars, the total amount of electricity needed to run so many vehicles is significant.
This drives up total electricity generation across the shared grid network, affecting poorer, fossil fuel-dependent cities—which in turn endure higher pollution from the carbon emissions created in generating that power, as well as the additional cost of measures to mitigate that pollution.
The researchers say their findings, published in Nature Cities, could apply to richer and poorer cities in countries worldwide.
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Senior author Professor Zhifu Mi (UCL Bartlett School of Sustainable Construction) said, "Electric vehicles are one of the most important pathways for decarbonizing transport, and their rapid growth in China is a major opportunity to reduce national emissions.
"However, our study shows that the carbon benefits of electric vehicles depend strongly on the power system.
"Decarbonizing the grid must go hand in hand with promoting electric vehicles, while policies should ensure that less developed cities do not bear disproportionate carbon burdens."
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The researchers found that the growing popularity of electric vehicles is increasing power demand in the richest cities that have been the biggest adopters.
However, through the interconnected power grid, much of their surging electricity demand is met by power produced in nearby less developed cities that still rely on coal or other fossil fuels, minimizing the carbon-reduction impact of electric vehicles and putting a greater environmental and economic burden on these poorer cities.
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The researchers found that while it appeared the country's 20 most economically advanced cities accounted for 80% of carbon emission reductions, 136 of the cities they analyzed (nearly 50%) have become 'carbon importers'—cities that have increased their carbon footprint by shouldering the power generation burden for electric vehicles used elsewhere.
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There have been significant economic disparities in the adoption of electric vehicles. About 75% of China's electric vehicles were concentrated in just 10% of cities in 2020, predominantly those with the highest GDP per capita. This means the cities adopting electric vehicles fastest are generally not the same cities producing the electricity and carbon emissions.
Mi said, "Electric vehicles are necessary, but not sufficient on their own. To maximize their climate benefits, we need cleaner power grids, better carbon accounting, and compensation or support mechanisms for cities that bear transferred emissions."
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