By Jonny Lupsha, Wondrium Staff Writer
Auto giants like GM and Volvo plan to phase out gas-powered vehicles by 2036. Meanwhile, Tesla’s automobiles have always been electric and startups like Rivian are supplying electric-powered pickups to Amazon. Electric vehicles are far more power-efficient.
It took a while for electric vehicles, or EVs, to catch on. The 2010 Nissan Leaf was one of the first electric cars, if not the first. Since that time, interest in EVs snowballed, with success stories like Tesla ensuring that there was ample room in the market for cars not powered by gas. Now, many major auto manufacturers are eschewing gas-powered vehicles entirely. Jaguar recently announced a full shift to an EV lineup, in just five years.
Electric cars are often touted for their reduced emissions, smaller carbon footprints, and other environmentally friendly benefits. However, what about their batteries? In terms of energy efficiency, how does an EV stack up to a gasoline engine?
It Keeps Going, and Going, and Going…
In his video series The Science of Energy: Resources and Power Explained, Dr. Michael E. Wysession, Professor of Earth and Planetary Sciences at Washington University in St. Louis, explained the insides of electric vehicles.
“The low energy needs of electric cars are largely because of the high efficiencies of rechargeable batteries,” Dr. Wysession said. “For example, lithium-ion batteries have very high energy densities. They’re costlier than other batteries, but they can be discharged and recharged many thousands of times with just a small drop in efficiency.”
According to Dr. Wysession, the battery pack for a Tesla Model S contained over 7,000 lithium-ion batteries. It can store 806 megajoules of energy and drive over 250 miles on a single charge. On the other hand, some EVs are intended for driving around town. The 2015 Nissan Leaf was released with such a purpose; it can drive just 75 miles on a charge.
A Word on Efficiency
“In examining the energy efficiency of an electric car, you have to take into account not just the efficiency of the batteries, but the original source of the energy as well,” Dr. Wysession said. “If it’s coal or nuclear supplying the electricity, then you have to reduce the total efficiency by two-thirds because coal and nuclear are only about 35% efficient.
“But once you have electricity, the grid-to-motor efficiency for electric cars is about 75%, which is really very good.”
When it comes to the separate components, he said, the motor and drivetrain are about 90% efficient, while the inverter and the charger are each about 95% and the battery is 93%. Multiplying them together arrives at 75% or so. Is this more efficient than gas-powered cars?
“Electricity transmission is about 93%, on average,” Dr. Wysession said. “The efficiency of power plants range from about 35% for coal and nuclear to up to 60% for natural gas combined cycle. Combined with the 75% for the electric car itself, that gives total energy efficiencies of 24% to 42% or so.
“On the other hand, a conventional car gets an efficiency of about 15% of the energy of the gasoline for the actual running in the car.”
Even on an EV’s worst day, it’s more energy efficient than a gas-powered car. This is just one of many reasons manufacturers of electric vehicles tout their products over gas-powered cars. Conventional automobiles may soon be a thing of the past.