Smarter and cleaner cars

Hybrid rethink

If you thought that you knew what hybrid vehicles are, then think again. It's no longer enough to know that a hybrid keeps down emissions by combining conventional internal combustion engines with electric propulsion fuelled from batteries. There are now increasingly ingenious ways of uniting those two power sources – frequently keeping carbon dioxide emissions well below 100g CO
2/km and even below 90g CO2/km.

Honda's Insight family saloon, for instance, with its Integrated Motor Assist, is classed as a semi-hybrid, with a small electric motor that is incapable of propelling the car alone. A 1.3-litre petrol engine is assisted when the need arises by a smaller electric motor, which is fed by batteries, fuelled in part by recuperated kinetic energy from braking and deceleration.

The same principle applies – on a rather larger scale - to the Mercedes S400 Hybrid, or to the Lexus Rx 450h, weighing in at 2.2 tonnes, which boasts two auxiliary electric motors to ease the task of the V6 petrol engine, keeping emissions down to 148g CO2/km.

By contrast, the Opel Ampera is driven uniquely by its electric motor, and its combustion engine serves only to charge the batteries, giving the car a range of 500km. The electric motor in the Toyota Prius, powered in part by the combustion engine and part by energy derived from coasting and braking, provides a power boost when needed – such as in rapid acceleration, but can also operate alone to propel the car, although at limited speed. And for those who hunger for prestige as well as propriety, the first Jaguar hybrid is heralded for 2011, in which the petrol engine will be auxiliary to the electric motor.