Known as the Global Green Challenge, solar-powered and fuel-efficient cars are racing 3,000 kilometers through Australia's tropical rainforests, desert and coastal plains, all in the name of the environment.

A fleet of nearly 40 solar powered cars from 17 countries, designed mainly by engineering students, will take about a week to race from Darwin to Adelaide in an event staged every two years since 1987. For the first time, there is also a second category, the Eco Challenge, in which 17 cars from 10 manufacturers compete in eco-friendly vehicles now or soon to go on sale, to prove which is the most fuel-efficient.

Organizers expect most attention to focus on the Global Green Challenge, with its fleet of unique and quirky vehicles highlighting research and development progress.