What Is a Hybrid Car? Learn How Hybrid Vehicles Work

Have you pulled your car up to the gas pump lately and been shocked by the high price of gasoline? Maybe you've thought about trading in your car for something that gets better mileage — or maybe you're worried that your car is contributing to the greenhouse effect, but you're not ready to go fully electric.

Enter the hybrid car. But how do hybrid electric vehicles work?

What goes on under the hood to give you 20 or 30 more miles per gallon than the standard gas-powered automobile? And does it pollute less just because it gets better gas mileage? Also, where does the plug-in hybrid come in?

In this article, we'll help you understand how this technology works, and we'll even give you some tips on how to drive a hybrid car for maximum efficiency.

Gasoline Power vs. Electric Power

The gasoline-electric hybrid car is just what it sounds like — a cross between a gasoline-powered car and an electric car. Let's start with a few differences between a gasoline-powered car and a typical electric car.

A gas-powered car has a fuel tank supplies gasoline to the internal combustion engine. The engine then turns a transmission, which turns the wheels.

An electric car, on the other hand, has a set of batteries that provides electricity to an electric motor. The motor turns a transmission, and the transmission turns the wheels.

The hybrid is a compromise. It attempts to significantly increase the mileage and reduce the emissions of a gas-powered car while providing the convenience of refueling at the gas station.

Gasoline-electric Hybrid Structure

Gasoline-electric hybrid cars contain the following parts:

• Gasoline engine: The hybrid car has a gasoline engine much like the one you will find on most cars. However, the engine on a hybrid is smaller and uses advanced technologies to reduce emissions and increase efficiency.

• Fuel tank: The fuel tank in a hybrid is the energy storage device for the gasoline engine. Gasoline has a much higher energy density than batteries do. For example, it takes about 1,000 pounds (454 kg) of batteries to store as much energy as 1 gallon (3.8 liters) of gasoline.

• Electric motor: The electric motors on hybrid cars are very sophisticated. Advanced electronics allow it to act as a motor as well as a generator. For example, when it needs to, it can draw energy from the batteries to accelerate the car. But acting as a generator, it can slow the car down and return energy to the batteries.

• Generator: The generator is similar to an electric motor, but it acts only to produce electrical power. It is used mostly on series hybrids.

• Batteries: The batteries in a hybrid car are the energy-storage device for the electric motor. Unlike the gasoline in the fuel tank, which can only power the gasoline engine, the electric motor on a hybrid car can put energy into the batteries as well as draw energy from them.

• Transmission: The transmission on a hybrid car performs the same basic function as the transmission on a conventional car. Some hybrids, like the Honda Insight, have conventional transmissions. Others, like the Toyota Prius, have radically different ones.

Parallel Hybrids

You can combine the two power sources found in a hybrid car in different ways. One way, known as a parallel hybrid, has a fuel tank that supplies gasoline to the engine and a set of batteries that supplies power to the electric motor.

Both the engine and the electric motor can turn the transmission at the same time, and the transmission then turns the wheels.

Series Hybrids

In a series hybrid, the gasoline engine turns a generator, and the generator can either charge the batteries or power an electric motor that drives the transmission. Thus, the gasoline engine never directly powers the vehicle.

Hybrid Car Performance

The key to a hybrid car is that the gasoline engine can be much smaller than the one in a conventional car and therefore more efficient. Most cars require a relatively big engine to produce enough power to accelerate the car quickly.

In a small engine, however, the efficiency can be improved by using smaller, lighter parts, by reducing the number of cylinders and by operating the engine closer to its maximum load.

Why Are Smaller Engines More Efficient?

There are several reasons why smaller engines are more efficient than bigger ones.

• The big engine is heavier than the small engine, so the car uses extra energy every time it accelerates or drives up a hill.

• The pistons and other internal components are heavier, requiring more energy each time they go up and down in the cylinder.

• The displacement of the cylinders is larger, so more fuel is required by each cylinder.

• Bigger engines usually have more cylinders, and each cylinder uses fuel every time the engine fires, even if the car isn't moving.

This explains why two of the same model cars with different engines can get different mileage. If both cars are driving along the freeway at the same speed, the one with the smaller engine uses less energy.

Both engines have to output the same amount of power to drive the car, but the small engine uses less power to drive itself.

Getting Enough Power

How can this smaller engine provide the power your car needs to keep up with the more powerful cars on the road?

Let's compare a car like the Chevy Camaro, with its big V-8 engine, to our hybrid car with its small gas engine and electric motor. The engine in the Camaro has more than enough power to handle any driving situation.

The engine in the hybrid car is powerful enough to move the car along on the freeway, but when it needs to get the car moving in a hurry, or go up a steep hill, it needs help. That "help" comes from the electric motor and battery — and this system steps in to provide the necessary extra power.

The gas engine on a conventional car is sized for the peak power requirement (those few times when you floor the accelerator pedal). In fact, most drivers use the peak power of their engines less than 1 percent of the time.

The hybrid car uses a much smaller engine, one that is sized closer to the average power requirement than to the peak power.

Improving Fuel Economy in 5 Different Ways

Besides a smaller, more efficient engine, today's hybrids use many other tricks to increase fuel efficiency. Some of those tricks will help any type of car get improved fuel economy, and some only apply to a hybrid.

1. Recovering Energy and Storing It in the Battery

Whenever you step on the brake pedal in your car, you are removing energy from the car. The faster a car is going, the more kinetic energy it has.

The brakes of a car remove this energy and dissipate it in the form of heat. A hybrid car can capture some of this energy and store it in the battery to use later.

It does this by using a "regenerative braking" system. That is, instead of just using the brakes to stop the car, the electric motor that drives the hybrid can also slow the car. In this mode, the electric motor acts as a generator and charges the batteries while the car is slowing down.

2. Sometimes Shutting Off the Engine

A hybrid car does not need to rely on the gasoline engine all of the time because it has an alternate power source: the electric motor and batteries. So the hybrid car can sometimes turn off the gasoline engine — for example when the vehicle is stopped at a red light.

3. Using Advanced Aerodynamics to Reduce Drag

When you are driving on the freeway, most of the work your engine does goes into pushing the car through the air. This force is known as aerodynamic drag.

This drag force can be reduced in a variety of ways. One sure way is to reduce the frontal area of the car. Think of how a big SUV has to push a much greater area through the air than a tiny sports car.