Electric vehicles from Australia, Germany and Switzerland set off Monday on the "longest and greenest" round-the-world drive to promote emissions free transport and November's world climate conference.

The UN-backed "Zero Race" is organised by Swiss schoolteacher Louis Palmer, who made headlines with his 18-month pioneering world tour in a solar-powered "taxi" two years ago, picking up celebrities on the way.

"With this race we want to show that seven billion people on this planet need renewable energy and clean mobility," said Palmer.

"Petrol is running out and the climate crisis is coming, and we are all running against time."

A South Korean vehicle failed to reach the start line at the United Nations in Geneva in time after it broke down with "a minor battery problem" some 60 kilometres (37.3 miles) up the road, Palmer said.

It was due to join the other three teams later in the day.

The Zero Race is planning to stop off at the World Climate Conference in Cancun, Mexico, after touring through Europe, Russia, China, Canada and the United States before heading back to Geneva in January 2011.

Each plug-in electric vehicle can travel at least 250 kilometres on a single charge, with 80 days of driving time ahead of them.

They are obliged to consume no more electricity than each team has generated or purchased from clean energy sources such as wind, solar and hydroelectric power.

Australian team TREV, run by Jason Jones and his 24-year-old son Nick, an electrical engineer from Adelaide, told AFP the trip through 16 countries would cost them about 400 Australian dollars (360 US dollars) in fuel.

"We've already bought the power and put it back in the grid," 57-year-old Jones senior explained, standing next to their plastic-bodied two-seat three wheeler.

"We thought it just a great way to show what this car is capable of. The future of automotive transport is not a one-and-a-half tonne gas guzzler."

The vehicles, which also include the Vectrix scooter from Germany and a Swiss Zerotracer two wheeler claiming a top speed of 240 kilometres per hour (150 mph), will be followed by Palmer in a repair van with a trailer.

Palmer said emissions from the the van as well as ship crossings across the Pacific and Atlantic oceans would be carbon offset.