CHM333 Hybrid and Electric Cars

By combining elements of conventional and electric cars, hybrid cars obtain advantages from both. The picture below displays the routes by which energy is lost for a car.

Hybrid cars operate more efficiently than conventional cars by minimizing this energy loss. By using a battery, the engine itself of a hybrid car works more efficiently than a combustion engine alone. This is partly because the combustion engine of a hybrid is much smaller than that of a conventional one. Conventional engines are large in order to perform sufficiently during high power situations such as climbing steep hills or accelerating dramatically. These situations, however, are fairly rare in a vehicle's day to day operation. In a hybrid the battery supplies additional power to the combustion engine when a lot of power is needed. In this way a hybrid can use a smaller engine and still meet all power demands.

Hybrid cars also employ a clever technique known as "regenerative braking," whereby the kinetic energy of a car is converted into electrical energy in recharging the battery via the electric motor when the car brakes. This conserves energy that is normally dissipated as heat when a car stops. Since a hybrid car does not depend wholly on its combustion engine for propulsion, the combustion engine in a hybrid can be shut off during temporary stops to conserve gas. The data table below displays the superior efficiency of hybrid cars. The first three models are hybrids, and the rest are conventional.

	City/Hwy/Combined
Honda Insight	61/68/64 mpg
Toyota Prius	52/45/48 mpg
Honda Civic Hybrid	46/51/48 mpg
Volkswagen Jetta Wagon TDI	42/50/45 mpg
VW New Beetle TDI	42/49/45 mpg
Volkswagen Golf TDI	42/49/45 mpg
Volkswagen Jetta TDI	42/49/45 mpg
Toyota ECHO	35/43/38 mpg
Toyota Corolla	32/40/35 mpg
MINI Cooper	28/40/32 mpg

Recent designs of hybrid cars also increase efficiency through general techniques not inherently limited to hybrid vehicles. These designs reduce the overall weight of the car. They also use tires that are more stiff and inflated to a higher pressure than those of conventional cars, thereby reducing aerodynamic drag on the vehicle.

Relative to electric cars specifically, hybrids offer several key advantages. Current designs of hybrid cars are more lightweight and affordable than the electric ones. Unlike electric cars, hybrid vehicles require no inconvenient recharging and are refueled in the conventional manner. Thus hybrids offer the option of long-range travel that electric cars cannot. Because of the presence of the combustion engine, hybrid cars also can achieve greater speeds than most electric ones can.

Because they are more efficient than conventional vehicles, hybrid cars cut down emissions. A well designed hybrid can reduce smog pollution by 90% or more and greenhouse gases by a third to a half compared with the cleanest available conventional cars.

Hybrid Cars

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