SciTech

How Things Work: Hybrid Cars

In the recent past, people have payed a much higher price for gasoline than before. Some are even reluctant to fill up the gas tank because they might end up spending $30 or $40.

A gasoline-powered car can usually drive at least 300 miles between refueling, can be refueled quickly and easily, and keep up with traffic on the road.

But gasoline-powered cars also produce a lot of pollution and get subpar gas mileage. On the other hand, electric cars produce almost no pollution, but can only go 50 to 100 miles between charges.

Over the past few years, though, the automotive industry has found its happy medium: A hybrid car is a compromise between the two that can increase gas mileage and reduce emissions.

A hybrid car consists of a gasoline engine, an electric motor, a set of batteries, and a generator. The gasoline engine is much smaller and uses advanced technologies to reduce emissions. The car also uses the engine in order to increase power and efficiency.

Simultaneously, the electric motor can draw energy from the batteries to accelerate the car and return energy to the batteries. This means that the gas pedal and the brake pedal are equally important, because a hybrid car uses “regenerative braking” to recover energy and store it in the battery.

When the hybrid car brakes, energy in the form of heat is given off and stored. The electric motor uses the stored energy to generate a little electricity to charge the batteries, and the cycle continues.

Sometimes, when the vehicle is stopped, at a red light for instance, the hybrid can shut off the gasoline engine because it can rely on its alternate power source — the electric motor and batteries.

Some hybrids, like the Toyota Prius, use a unique power split device that hooks the gasoline engine, generator, and electric motor together.

Once the car reaches a certain speed, the gasoline engine will turn on and settle into a constant speed, while the generator and electric motor work to match the output speed of the car. The gasoline engine and electric motor move the car, and the generator produces all the electricity.

In addition, the forward areas of many hybrid vehicles are designed to reduce aerodynamic drag. Some hybrids are designed using a teardrop shape where the back of the car is narrower than the front. The rear wheels are partially covered by body work to provide a smoother shape.

Even the tires differ on hybrid cars. The tires on most cars are optimized to minimize noise, give smooth rides, and provide good traction, but hybrids use special tires that are optimized for efficiency. They are stiffer and inflated to a higher pressure than regular tires in order to reduce drag.

Lastly, hybrids are built out of lightweight materials, like aluminum, that greatly reduce the amount of energy needed to accelerate the car.

By reducing the weight of the car, manufacturers can use a lighter engine with the same level of performance as regular cars.

For example, the engine in the Honda Insight weighs 124 pounds and is a tiny, 1.0-liter, three-cylinder that produces 67 horsepower at 5700 revolutions per minute (rpm).

In a hybrid, the electric motor works alongside the gasoline engine to produce the same amount of torque as a regular gasoline engine car.

The electric motor adds more torque (the more torque, the greater the acceleration) at lower speed ranges. Without the electric motor, the Insight makes its peak torque of 66 foot-pounds at 4800 rpm. With the electric motor, it makes 79 foot-pounds at 1500 rpm.

Hybrid power is a complex combination of gasoline power and electric power. A hybrid car will squeeze every last mile out of a gallon of gasoline to produce better mileage.

For example, the 2007 Toyota Camry Hybrid has a city mileage of 40 miles per gallon (mpg), while the 2007 Toyota Camry has a city mileage of 22–24 mpg.

Hybrids are also rated as Advanced Technology Partial Zero Emissions Vehicle (AT-PZEV) for emissions. AT-PZEV-rated vehicles are 90 percent cleaner than the average new car and have near-zero evaporative emissions, which escape when gasoline evaporates.