2006 Paris Auto Show: alternative-fuel vehicles

A hybrid concept car with zero fossil-fuel emissions, the Saab BioPower 9-3 uses a bioethanol-powered turbo engine coupled with three electric motors to produce 260 horsepower, which is more than the gasoline-only 9-3. Saab designers say that a future version of the car will incorporate a button enabling the driver to manually select electric-only mode in speeds of less than 50mph.

Renault is another manufacturer showcasing a flex-fuel vehicle in the shape of an E85 version of its popular Megane hatchback. Renault will begin selling a production version of the Megane Bioethanol in 2007. This will take advantage of the initiative announced by the French government last month to begin deploying a bioethanol distribution network in France in 2007.

The strikingly designed Aero X from Saab was first unveiled at the Geneva Motor Show earlier this year, and was on display again in Paris. Aside from its eye-catching exterior design, the Aero X features a V-6 twin turbo engine that runs solely on bioethanol (E100). Without the creation of the any carbon dioxide emissions, the Aero X delivers a healthy 400 horsepower, and will go from standing to 60mph in less than 5 seconds.

Last month, BMW announced that it was going to release the Hydrogen 7 model, a 7-series BMW with the ability to run either on gasoline or hydrogen. The Hydrogen 7 was based on bifuel technology that BMW developed in its 6-liter V-12 H2R, which has set nine speed world records for a hydrogen-powered car. To date, the H2R has been the flagship of BMW's Clean Energy program, which aims to use hydrogen produced from renewable sources to power its cars, thus creating a net-zero-emissions vehicle.

The Epure uses a GENEPAC proton exchange membrane fuel cell made from thin stainless-steel plates, which generates 20kW of electricity. According to Peugeot, the fuel cell provides efficiency of more than 50 percent, compared to 25 to 30 percent for an internal-combustion engine.

Building on previous iterations of its flagship fuel-cell vehicle, Honda used the Paris show as the platform to unveil its FCX Concept. The new FCX is all but indistinguishable from its predecessor (the FCX Cell): gone is the two-door hatchback, which Honda has replaced with an aerodynamic, low-riding sedan. One of the reasons that Honda has been able to make its latest fuel-cell vehicle roomier and more aesthetically appealing is a reduction in the size and orientation of its fuel-cell stack, which is now around 25 percent smaller and is aligned vertically along the car's length in a dedicated tunnel.

Fiat's alternative fuel offering came in the shape of its Multipla Multi-Eco, a "tri-fuel" concept car that can run on gasoline, E85 (a mixture of gasoline and ethanol), or methane. Software in the car's engine monitors and regulates the mixture of gasoline and ethanol, which can both be added into the same tank.

Citroën's C4 Hybrid HDi combines a diesel combustion engine with a 16kW electric motor, which can power the car by itself at speeds of up to 50kmh. The electric motor also acts as an inverter to capture the car's braking energy, which is then stored in a high-voltage nickel-metal-hydride battery pack. To further increase fuel efficiency, the C4 Hdi Hybrid includes a feature called Start and Stop, which cuts the engine just before the car comes to a stop, then restarts it when the brake pedal is released following a period of idling.

Based on the gasoline-powered Peugeot 207, the zero-emissions 207 Epure is PSA Peugeot Citroën group's latest fuel-cell concept car. The Epure is powered by an electric motor, which in turn gets its charge from the car's onboard hydrogen fuel cell. With enough capacity for 3kg of hydrogen compressed to 10,000psi in its five storage cylinders, the Epure has a range of around 220 miles and a top speed of 80mph.

Alternative-fuel vehicles are the car tech story of the new millenium. Whether it's hydrogen fuel cells, hybrids, electric power trains, or ethanol-based fuels, the auto world is catching on to the idea that green is for go. Here's our roundup of cars at the 2006 Paris Auto Show that will never have to fill up with gasoline.