Researchers say federal subsidies should reflect EVs’ impact on specific environments.
Researchers say federal subsidies should reflect EVs’ impact on specific environments.

Study: EV Incentives Should Consider Shades of Green

Researchers found the “green” value of EVs can vary dramatically across the U.S. due to climate differences, whether producing the electricity to recharge them relies on fossil fuels, and how far the vehicles are driven each day.

Case Western Reserve University researchers recommend scrapping the standard $7,500 federal incentive to buy electric vehicles in favor of a sliding scale favoring states where EVs least harm the environment.

This after their research found the “green” value of EVs can vary dramatically across the U.S. due to climate differences, whether producing the electricity to recharge them relies on fossil fuels, and how far the vehicles are driven each day.

Lead researcher Chris Yuan, an associate professor in Mechanical and Aerospace Engineering at Case Western Reserve, says the study concludes that how environmentally friendly EVs are as alternative to fuel-burning vehicles actually may depend on where you live.

“EV batteries degrade so differently in each state that the battery life and the greenhouse-gas emissions should both factor in EV incentives,” Yuan says in a statement.

“This research provides the facts for our policymakers to think about the strategies to do it better,” he says. “It may not be a good option to offer the same financial incentive to EV drivers in all states.”

The study finds EVs sometimes can contribute as much in greenhouse-gas emissions (GHG) as their internal-combustion-engine-powered counterparts – even if indirectly from the electricity consumed by the battery in powering the vehicle.

The study, published in the journal Nature Communications, was conducted in collaboration with researchers from Argonne National Laboratory in Illinois and the University of Wisconsin-Milwaukee.

The research concludes not all EVs have desired results in all U.S. states.

Recharging EV batteries in states which rely heavily on coal or natural gas to generate electricity produces more GHGs. Conversely, batteries recharged in states with a large share of hydropower or renewable energies – such as wind and solar – produce less GHG emissions.

Warmer weather and more driving miles wear out EV batteries faster, requiring more frequent recharging, which gradually increases an EV’s energy consumption and GHG emissions.

For their research, the scientists developed mathematical models to quantify the battery degradation and its effects on increasing energy consumption and GHG emissions from a midsize EV in average driving conditions in all 50 states.

They factored in several technical and environmental parameters for the vehicle operations – from hourly ambient temperature to average driving distance – to predict the life of a typical battery pack.

They found the life expectancy of EV batteries ranges nationally from about five years in Florida to more than 13 years in Alaska.

GHG emissions from EV operations also vary by state, ranging from 18.7 lbs. (8.5 kg) in Vermont to 5,654 lbs. (2,570 kg) in Indiana, when a battery is new and at full strength.

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