Some commentators responded to the Prime Minister’s recent announcement of the government’s intention to introduce a clean air act that the key to improving urban air quality is to mandate stricter requirements for improved fuel efficiency in automobiles. Who could argue with wanting to improve fuel efficiency? But does fuel efficiency refer to how much power is generated per litre, or to how many miles per litre the vehicle can travel, or to minimizing the car’s exhaust or harmful exhaust? The answer is all three.
The internal combustion engine burns petroleum products (gasoline or diesel fuel), and this fuel when burned produces carbon monoxide, nitrogen oxides, hydrocarbons and greenhouse gases. All of these emission products are harmful, and in sufficient quantity, deadly, so it makes sense to limit or get rid of the emissions problem.
Hybrid cars have the best mileage ratings of all conventional-sized cars on the market today and produce the least harmful exhaust. The hybrid technology addresses all the pollution issues, “power per litre”, mileage and low emissions. An excellent explanation of hybrid car performance can be found at www.auto.howstuffworks.com/hybrid-car1.htm.
In hybrid cars the gasoline engine is 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 is improved by using smaller, lighter parts, by reducing the number of cylinders and by operating the engine closer to its maximum load.”
Smaller engines are more efficient for several reasons. Bigger, heavier engines use extra energy every time the vehicle they power accelerates or drives up a hill. Bigger engines usually have more cylinders, and each cylinder uses fuel every time the engine fires, even if the car isn’t moving. The displacement of the cylinders is larger, so each cylinder requires more fuel. This means that two of the same model cars with different size 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.
The smaller engine in the hybrid provides the needed power 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 gets help from the electric motor and battery. The gas engine on a conventional car is sized for peak power requirements but these are generally required less than one 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. And because the hybrid uses less gasoline per mile it also emits less harmful emissions per mile compounded by the fact that some of its power comes from a clean energy source, electricity.