Above: Components of a hybrid engine (Peter Welleman)

You've probably seen TV commercials featuring sleek new hybrid cars zooming through fields of green and picturesque scenery, with a narrator praising their fuel efficiency and low environmental impact. But what does it all mean? What makes hybrid cars environmentally friendly? And why are they so fuel-efficient?

What is a hybrid vehicle?

Did you know? A purely electric car produces no direct air pollution, but current technology only allows for a range of 80-160 km on a single charge. Electric-gasoline hybrids can provide many of the advantages of an electric car while overcoming this limitation.A hybrid vehicle uses two or more different sources of power to create movement. These sources can include electricity, gasoline, diesel, nuclear power, and even manual power like pedalling (as in the case of an electric bike)! Even if you don’t own a hybrid car, some vehicles you already use, like ferries and buses, may actually be electric-gasoline or electric-diesel hybrids. Some hybrids, including certain submarines, run on a combination of nuclear power and electricity!

Using both electricity and gasoline

Hybrid cars have a specialized engine that can use both electricity and gasoline. As a result, they use less gasoline than conventional non-hybrid (gasoline-only) cars. In fact, there are two different types of hybrid cars: parallel setup and series setup. They differ in how they use the energy produced from gasoline and electricity.

Structure of a parallel hybrid vehicle. Click image to enlarge (Peter Van den Bossche)

Structure of a series hybrid vehicle. Click image to enlarge (Peter Van den Bossche)

Parallel setup cars have a small gasoline engine alongside an electric motor, which is powered by a battery. The gasoline engine and the electric motor are independently connected to the transmission, which moves the car’s tires. A parallel setup allows the car to be started and operated using either electricity or gasoline. This provides increased fuel savings when only electricity is used, such as when driving at lower speeds.

In a series setup car, all of the components are connected in a line. First, a generator converts the power generated by the gasoline engine into electricity. This electricity is then either used to power an electric motor that drives the transmission or to charge the car’s battery.

The International Organization of Motor Vehicle Manufacturers (OICA) has a diagram comparing parallel and series hybrid cars on its website. Have a look at the bottom of this article on hybrid vehicles:

www.oica.net/category/auto-and-fuels/alternative-fuels/hybrid/

A series setup is less complex than a parallel setup, and its gasoline engine is used more efficiently since it does not directly power the car and is not subjected to the frequent stopping-and-going that occurs during city driving. In addition, because of their smaller, more efficient engine, series hybrids create fewer harmful greenhouse gas emissions than parallel hybrids.

However, series hybrids have larger, more complicated batteries and motors. As a result, they cost more than parallel hybrids. In addition, series hybrids are not as efficient at highway speeds since the gasoline engine is not directly powering the wheels.

What makes hybrids more fuel efficient and environmentally friendly?

There are many reasons why hybrids are more fuel-efficient than conventional cars. The most obvious is that hybrids can use electricity to power the transmission, which decreases the amount of gasoline the car has to burn. Hybrid engines are designed to be smaller and lighter than conventional engines, so less power and fuel is needed to propel the car. Hybrids also tend to be lighter because they are often made from lightweight materials such as carbon fiber or aluminum and magnesium.

Did you know? Some hybrid cars use both series and parallel systems. They operate as series hybrids at lower speeds (for increased efficiency) and as parallel hybrids at higher speeds (for increased power).Hybrids can be designed to turn off the gasoline engine and use only the electric motor while the car is idling or stopped at a red light. They can also retain the energy that would normally be wasted when the driver applies the breaks through a process called regenerative breaking, which slows the car using the electric motor instead of the brakes. This way, the electric motor acts as a generator and charges the battery, storing energy for later use. If conventional brakes were used, this energy would simply be lost through dissipating heat. Furthermore, hybrid cars usually have tires that are stiffer and inflated to higher pressures than tires on conventional cars, reducing both drag and the amount of energy needed to move the car.

Because hybrids are more fuel efficient, they produce fewer greenhouse gas emissions than conventional cars. The difference actually increased along with the size of the car. For example, a hybrid compact car produces 10% fewer emissions that a conventional compact car; a full-sized hybrid SUV produces 21% fewer harmful emissions than a conventional full-sized SUV.

Of course, as the price of gasoline rises, using less fuel will give your wallet a break as well!

References

Comparing Hybrids Side-by-Side (US Department of Energy) Environmental Impact of Hybrid Cars (Timothy Banas, Livestrong.com) How do Hybrids Work (Discovery.com) How Hybrid Cars Work (Karim Nice and Julia Layton, How Stuff Works) Top 10 Hybrid Myths (Brad Berman, HybridCars.com) What Are the Advantages and Disadvantages of Series Hybrid Designs (Carolyn Randall, SFGate.com)

Amy Le

I am currently a student studying pharmacy at the University of British Columbia. In my spare time, I enjoy playing ultimate frisbee, reading, drawing and going on hikes or trails where I can capture the breathtaking scenery on my camera! I love teaching about science through the outreach programs Let's Talk Science provides. As Bill Nye the Science Guy would say,Science Rules!


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