Charging Electric Vehicles at Night Can Cause More Harm Than Good, Says CMU Study
Carnegie Mellon University’s study, recently published in the journal Environmental Research Letters, poured anxiety on the night charging of electric cars.
So far, we have been accustomed to think that night charging is not only suitable to EVs that sit in garages, but could take advantage of unloaded power plants/grids from a cost perspective.
According to the study there is however question about environment impact of night charging.
Jeremy Michalek, a professor of engineering and public policy and mechanical engineering, and his colleagues modeled the PJM region, which includes Washington, D.C., Philadelphia, Pittsburgh, Cincinnati and Chicago, and whether there is someting wrong in generating electricity at night instead during the day?
CMU’s study concerns coal-fired power plants suggesting that at least in some cases night charging could indeed cause more harm over daytime than good.
“Researchers at Carnegie Mellon University find that while charging electric vehicles at night is more cost-effective, it increases air emissions.
Charging electric vehicles late at night, when demand is low and electricity is cheapest to generate, is preferred by grid operators. However, CMU researchers found that it produces substantially higher greenhouse gas emissions and air pollution than simply charging as soon as the driver returns home.”
“We looked at how power plant operations would change in response to electric vehicle charging load, and we modeled emissions from those plants and their downwind air pollution consequences for human health and the environment. We found that charging late at night reduces power generation costs by a quarter to a third, largely by shifting to cheaper coal-fired power plants. But the extra emissions released as a result can cause 50 percent higher costs to human health and the environment.”
Sounds like just another reason to not like coal-fired power plants.
“According to the study, coal-fired power plants often operate below full capacity at night, so they are available to be dispatched in response to new nighttime load, like electric vehicle charging. These coal-fired power plants produce sulfur dioxide, which is the largest single source of cost to human health resulting from electric vehicle charging.
In a separate study, published in the journal Environmental Science & Technology, Michalek and colleagues looked at greenhouse gas emissions from electric vehicle charging across the United States.
“In nearly all U.S. regions, charging later at night increases greenhouse gas emissions,” he said.”
““For now, if you live in a coal-heavy region like the Chicago, Washington, D.C., Philadelphia area, delaying charging until late at night can cause more harm than good.””
If the findings are right, the only way to not increase environment impact per energy unit produced and delivered would be switch a from coal-fired power plants to some other cleaner sources, but on the other hand we have the costs and time needed to see those gradual improvements in the energy sector.
source: Carnegie Mellon University