Hybrid vehicles are obviously better for the environment. Right?

Electric motors don’t produce emissions, so it makes sense that it would be better to utilize electric power to minimize the power needed from emissions-producing gasoline engines.

And since electric motors are very efficient at low speeds (which happens to be the least efficient operating conditions for gasoline engines) it seems reasonable that the electric motor in a hybrid vehicle should carry all the load during city driving (which is typically done at low speeds) and the gasoline engine should take over on the highway, or in other situations in which driving speed is relatively high and consistent.

But it’s not that simple.

Gasoline engines are far worse for the environment at cold temperatures than they are at higher temperatures.

Your car’s catalyst is responsible for absorbing harmful pollutants before they reach the air. But these catalysts are essentially useless at cold temperatures. They have to warm up before the necessary reactions can take place fast enough to be effective.

So when we do our urban driving using just an electric motor and then transition to the engine for highway driving, the engine emits pollutants at a much faster rate than it would have if it been slowly heated during city driving like it is in a conventional vehicle. Add in the huge power draw needed to accelerate from 0-70 mph to merge on the highway, and you quickly get in a situation that could actually produce more emissions than a conventional gasoline-powered car would.

Ultimately, this is just one challenge with various potential solutions (heating the engine before it is needed, saving battery power to handle early highway driving, etc.) but it highlights a key aspect of the development cycle:

There are rarely simple solutions. The obvious slam-dunk answers we come up with tend to become more complicated as we try implementing them in the real-world.

It’s part of what makes engineering so demanding. And also what makes it so interesting.

-Brandon