The EVolution #5: Asphalt and battery
An overview of the technology that makes EVs possible, and how that compares to gas-powered cars
Automobiles powered by an internal combustion engine (“ICE”) have been around for over a century. Few of us know much about the mechanics of their operation. The advent of a new technology, though, gives us a good occasion to ask: how do electric vehicles work?
Owning the LIBs
EVs obtain electricity from the grid when they are plugged into an outlet or charging station. They store that energy in the car’s battery—specifically, a rechargeable lithium-ion battery (LIB).
“Lithium-ion batteries have revolutionised our lives since they first entered the market in 1991. They have laid the foundation of a wireless, fossil fuel-free society, and are of the greatest benefit to humankind.” — 2019 Nobel Prize in Chemistry citation
Yep, the same thing that powers your cellphone or laptop also powers electric cars. And there is an ongoing, incredible technological progression that is producing increasingly energy-dense batteries at ever-cheaper prices (down 79% over the past seven years).
Cheaper, better batteries translate directly to cheaper electric vehicles with longer driving ranges. Circa 2012, the Nissan Leaf could take you just 73 miles, and if you paid big bucks, the Tesla Model S had a range of 265 miles. The latter feat is matched today by many mass-market competitors, like the Chevy Bolt and Hyundai Kona, while the current Model S can go 412 miles. Improvements continue apace—BloombergNEF forecasts $100/kWh in 2023 (-27% from 2020 prices).
To any readers with a particular bent for science, I recommend a primer by David Roberts on LIB chemistry and battery pack structure. At some point the cost and energy-density curves will level off—and this has implications beyond just electric cars. For example, to what extent could electric planes and ships become viable?
Joby Aviation is one moonshot startup counting on this:
‘E’ is for efficiency
But back to cars! So we’ve got, like, an iPhone battery on steroids, instead of a fuel tank. What next?
The EV’s battery is used, in conjunction with an inverter, to power the car’s electric motor(s)—what’s responsible for rotating the wheels. It also has a drivetrain, which, like in an ICE car, distributes power from the motor to the wheels. In an EV, though, this is done with just a single-speed transmission—no clutch and no gears are required since electric motors generate torque at far lower speeds than their ICE equivalents.
Another unique feature of EVs is regenerative braking — the heat generated from the car’s brakes is captured and returned to the battery where it is stored for usage. What that means is when you pump the brakes on an electric car, you can actually add to your driving range!
EV vs. ICE
Given how widespread the usage of gasoline is, and for how long that has been the case, it must be an incredibly efficient fuel, right? Not exactly:
“EVs convert over 77% of the electrical energy from the grid to power at the wheels. Conventional gasoline vehicles only convert about 12%–30% of the energy stored in gasoline to power at the wheels.” — DOE/EPA
Burning gasoline generates energy through heat. But over half of that energy isn’t captured by the internal combustion engine and is simply lost. It’s akin to building a campfire to toast a marshmallow—some of the fire’s heat goes toward the intended purpose, but far more heat “escapes”. EVs are much more efficient at using the energy generated, and their regenerative braking captures some heat that would otherwise be lost and turns that into more energy.
Moreover, electric vehicles drivetrains are much simpler—around 20 moving parts, compared to 2,000+ in ICE cars. EVs don’t have spark plugs, catalytic converters, nor ignition coils. There are no engine pistons and valves. There is no oil or coolant to change. And there are no exhaust fumes to be emitted from a tailpipe.
That last point is the reason why EVs are often referred to as “zero-emissions vehicles”. While that’s true for direct emissions, there are of course some emissions involved in the production of the electricity that charges EVs. Different electricity sources (e.g. natural gas, coal, renewables) mean there is a widely varying amount of indirect emissions involved. Even so, on net they are still usually better:
“EVs typically produce fewer life cycle emissions than conventional vehicles because most emissions are lower for electricity generation than burning gasoline or diesel.” — DOE
More to come on this topic in a future edition of The EVolution!