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PETROL-ELECTRIC HYBRIDS
The system was popularised by Honda and Toyota but General Motors is fast-tracking hybrids now. The car combines an internal combustion engine with a battery that recharges from energy released by the car.
PLUSES: No special recharging or refuelling requirements.
MINUSES: Not very fuel-efficient at highway speeds for long distances. Current price up to $10,000 more than an equivalent-sized vehicle.
PLUG-IN HYBRIDS
A hybrid or pure electric car with batteries that can be recharged via a plug, like a mobile phone. Being developed by all key global manufacturers.
PLUSES: New generation lithium-ion batteries give plug-in cars a longer range.
MINUSES: Still in its infancy. Car makers and battery component suppliers are working through issues with costs, design and driving range.
HYDROGEN FUEL CELLS
Electric cars powered by hydrogen fuel cells. Honda, GM, Ford and Daimler are among carmakers developing them. The BMW Hydrogen 7 model uses liquid hydrogen.
PLUSES: No exhaust emissions and fewer moving parts than conventional engines.
MINUSES: Refuelling infrastructure limited; greenhouse gases are released when hydrogen is derived for fuel.
ELECTRIC VEHICLES
Newer, lighter and faster recharging batteries are driving development.
PLUSES: No emissions. Instant torque. Quietness.
MINUSES: Battery cooling, particularly with new lithium-ion batteries. Cost. Limited range. IN-WHEEL ELECTRIC
Michelin has entered a joint venture deal with a Chinese manufacturer to produce in-wheel electric motors, pictured. They are scheduled to appear on Chinese small cars in 18 months. The system mates the suspension and motor inside the wheel hub. It works with electric or fuel cell-powered electric cars and dispenses with the gearbox, clutch and drive shaft.
PLUSES: Revolutionises car design. All-wheel or two-wheel power choice. Instant torque. Versatile.
MINUSES: Weight of in-wheel motor. Unproven technology in mass production.
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