The Toyota Prius has spent a decade as the world's preferred hybrid, but now competition is arising from all quarters. A new plug-in version of the Prius is expected soon, but already Toyota is thought to be working on a project to bring solar power to mass production automobiles in an effort to leapfrog the market once again.

The report of Toyota's supposedly secretive effort to build a solar car originates with Japanese business paper The Nikkei, via the AP. According to their sources, Toyota has plans to incorporate solar panels on one of its cars, along with a house-mounted solar charging system. Unfortunately for those ready to hit the road with nothing but sunshine and a smile, the same sources also say it will be years before any such car takes to the streets.

Toyota's motive for pursuing a mass-produced solar-powered people mover? To re-establish its technological dominance and establish a strong foothold in a future that looks primed to be heavy with electric vehicles. It's not an entirely unrealistic vision either - an independent company has already developed a solar conversion kit for the second-gen Prius that enables the car to drive up to 20mi (32km) daily on solar power alone.

The end of 2008 was hard on Toyota, with the company posting its first sales loss, a significant $1.7 billion deficit. Already the company has implemented massive solar panels on the roof of one of its Camry plants, and uses the electricity generated to meet part of the plant's needs.

Previous reports of a solar-panel-equipped Prius being in development could lend some credibility to the rumor of secret solar development, and an avenue for preliminary testing of the technology. The roof-mounted solar panels on a near-term Prius would be for auxiliary systems such as stereo equipment, air conditioning and other relatively low-power features, rather than actual vehicle propulsion.

In the mean time, Toyota's Lexus luxury division is primed to release its new HS 250h hybrid sedan at the Detroit Auto Show, where the next-gen Prius hybrid will also make its debut