1997

Prius Hybrid Car

There was a call in the 1990s to reduce automotive emissions. One option: replace gasoline engines with a pure electric car. The technology wasn’t quite there yet. The batteries were too expensive, didn’t have enough range, and took too long to recharge. Engineers looked for some way to improve the efficiency to get much better mileage without compromises. Enter the Prius, the world’s first mainstream hybrid car, made by Toyota. It is a normal-size sedan, introduced in 1997, that gets great gas mileage because of its hybrid drive train. Millions have been sold.

A hybrid car has more than one source of motive power. In the case of the Prius, the car combines a normal gasoline engine with an electric motor and a battery pack. There are three key engineering insights that improve the mileage of the Prius. First, most cars have a much bigger engine than they need for most situations. When the car is cruising on the freeway, it needs only a fraction of the engine’s power. The reason why the engine is so big is for periods of acceleration, which are rare. If an electric motor can help with acceleration, then the gasoline engine can be much smaller and lighter. Second, idling and stop-and-go driving at slow speed wastes gasoline. If the electric motor handles these situations, the engine may not have to run at all. Electricity can also handle accessories like the air conditioner. Third, when the car brakes, the electric motor can become a generator and recharge the batteries. Putting these three things together gives the Prius significantly better gas mileage, especially in city driving.

Once the Prius proved to be so effective and popular, engineers came up with other hybrid flavors. At one end of the spectrum, electric motors and a battery handle accessories like air conditioning and instantly start the gasoline engine. Now the engine never needs to idle. At the other end, plug-in hybrids allow the car to recharge its battery overnight in the garage, and then the car can operate for 20 or 40 miles as a pure electric vehicle.

The hybrid vehicle marketplace is a great example of engineering creativity harnessed to create efficiency.

SEE ALSO Air Conditioning (1902), Internal Combustion Engine (1908), Lithium Ion Battery (1991), Self-Driving Car (2011).

Detail on a Toyota Prius plug-in hybrid on display during the 2012 Brussels Motor Show.