Car features Hybrid cars
Conventional cars are driven by either a petrol or diesel combustion engine.
What do is to add an electric motor to this engine – an extra drive source, which, through intelligent energy management, can support or even substitute for the combustion engine.
Parallel hybrid cars
The Honda Civic IMA is a 'parallel' hybrid
There are two types of hybrid system. The first, a ‘parallel’ hybrid (such as the Honda Civic Hybrid), uses both the engine and the electric motor together to power the wheels.
The electric motor assists the engine, allowing the carmaker to fit a smaller and more economical combustion unit than they might otherwise have done.
Because the motor does some of the work, there’s less load on the engine, which improves fuel consumption, and the motor works as both a starter and an alternator, shutting the engine down while the car is stationary.
Batteries power the electric motor, but they don’t have to be plugged into the mains to recharge. Instead, every time the car slows down or the brakes are applied, the electric motor reverses, turning into a generator to recharge the batteries.
However, a key failing of parallel hybrids is that, as the electrical source is a combined motor and generator, it cannot power the car on its own.
This means ‘zero-emissions’ running, without using the combustion engine, is not possible.
Series hybrid cars
Toyota's Prius can run on its electric motor alone
The alternative is the ‘series’ hybrid car, which gets its name from how power flows to the wheels.
This uses the engine to drive a generator, and the electricity created by it drives an additional electric motor, which then drives the wheels.
The engine is not directly connected to the wheels, and can always operate at the maximum efficiency for the best fuel consumption.
The most effective combine the benefits of both these systems in a series/parallel system.
The Toyota Prius is the most well-known example of this, and it is able to run using its electric motor alone. This can happen at low speeds, for genuine zero-emissions driving in city centres, though the range is very short.
Parallel hybrids use the engine as their main power source, operating it far more than the electric motor.
Series hybrid cars, which use the engine to drive the electric motor, have an even split between the two, but series/parallel hybrids swap continuously between them – with times when they use just the electric motor, just the engine, plus a large period when they work together.
This is because they adapt to the conditions, so they can always find the most efficient solution – when engine efficiency is low, the electric motor is used, and vice-versa.
