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Ask An Environmental Scientist: Do More Electric Vehicles = Less Winter Inversions?

Electric Vehicles

By DEQ Communications

Electric vehicles were first introduced more than 100 years ago, but have currently been on the rise as consumers look for cleaner, more energy-efficient and cost-effective ways to get around.

As our vehicles and energy technology become more advanced, data has shown a reduction in emissions and better air quality as a result. In fact, according to Energy.gov if we transitioned all light-duty vehicles in the U.S to hybrids or plug-in electric vehicles we could lower our carbon pollution from transportation up to 20%.

In today’s question submitted by Val Bennett, environmental scientist Glade Sowards delves into electric vehicles in Utah from how they affect wintertime pollution events to how an increase in electric power demand might affect local pollution levels.

QUESTION: If there were substantially more electric personal vehicles along the Wasatch Front and Cache Valley, would there be significantly less severe inversions in winter?

ANSWER: It would take a fairly substantial number of electric vehicles to have a large impact on local air quality. Among our light-duty passenger car and truck fleet, the largest polluters are Tier 0 and Tier 1 vehicles. Thankfully, traditional gasoline-powered vehicles have gotten dramatically cleaner over the past few decades and many of those vehicles are being replaced by Tier 2 and Tier 3 vehicles.

A Tier 0 vehicle emits 1.41 grams per mile of Nitrogen oxides (NOx) and Volatile Organic Compounds (VOCs) – pollutants that contribute to our wintertime particulate and summertime ozone challenges.  A Tier 3 vehicle, in contrast, emits just 0.030 grams per mile – a 98% reduction.  An electric vehicle, of course, provides a 100% reduction at the tailpipe.  So while EVs are cleaner, they only provide a slight improvement over a Tier 3 vehicle when compared to older, dirtier vehicles.  For this reason, to do much better than the current ongoing replacement of old vehicles with Tier 3 cars, you would really have to have a lot of EVs come into the fleet instead.

So far, we’ve only discussed emissions that cause local air quality issues like summertime ozone and wintertime particulates, but we should also consider greenhouse gas emissions like CO2. Electric vehicles that use renewables for their electricity are dramatically cleaner for CO2 emissions than gasoline-powered cars.

Inversions are essentially weather events that aren’t caused by vehicle choices or humans but an inversion can intensify the impact of human-caused emissions. Gases like NOx and VOCs can dissipate under favorable weather conditions like we see in the fall or spring. But during the stagnant conditions of an inversion, those same emissions can lead to a secondary formation of particulates that are responsible for big wintertime spikes in PM concentrations. Similarly, under hot and sunny conditions in summertime, those same gases can create spikes in ozone that wouldn’t otherwise occur.

How are inversions formed?

QUESTION: Would the increased electrical power demand for EV’s be a pollution problem for those that live close to power plants (Huntington, Delta for example)?

This is a good question.  While EVs have zero tailpipe emissions, we need to be mindful of the emissions associated with electricity generation. Fortunately, the electric generation mix on the Western grid is getting increasingly cleaner as solar, wind, and battery storage prices have decreased. Over the next 10-20 years, coal-fired generation is anticipated to mostly leave the grid and be replaced by renewables and natural gas. For example, the Carbon Power Plant near Helper closed in 2015, the Bonanza Power Plant near Vernal is under the settlement agreement to close around 2030, and the Huntington Power Plant in Emery County is scheduled to close in 2036.

In 2025, our largest coal-fired plant, the 1,800 MW Intermountain Power Plant (IPP) in Delta is going to convert to natural gas, and when that happens coal-fired generation will go way down and natural gas will increase. In addition, several Rocky Mountain Power coal-fired plants in Wyoming which help to provide power to Utah are scheduled to close throughout the 2020s.

When talking about vehicle emissions it is important to acknowledge the upstream emissions that gasoline-powered vehicles have. Oil and gas exploration and development is a significant source of air emissions in Utah. In 2017, oil and gas development emissions were roughly on par with total on-road mobile source emissions statewide.

When compared on a total emissions basis, electric cars, which are already cleaner on a life-cycle basis than gasoline-powered cars, are expected to become markedly cleaner over time.

Utah Energy Landscape
The Utah Geological Survey puts together a periodic energy summary for Utah. Here is a graph representing the net generation of electricity in Utah by energy source. With the initiatives happening now this chart is going to change pretty dramatically over the coming years.
Have your question answered by emailing us at deqinfo@utah.gov or posting your question on Facebook or Twitter.
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