Toyota won't just be adding solar panels to its popular Prius gas-electric hybrid car—like the solar electric conversion kit seen at left—it'll be powering a version of it exclusively via sunshine, according to The Nikkei, Japan's business newspaper. In fact, Toyota will be relying on the solar-electric car to "turn around its struggling business," which resulted in its first operating loss in more than 70 years, the Associated Press reports.

ScientificAmerican.com and other media outlets reported last summer that Toyota was planning to begin selling a Prius with some solar panels as early as May of this year. But the latest reports are that the Japanese automaker is seeking to build a totally solar-driven vehicle.

Toyota declined to comment—and denied the existence of such a vehicle to All Cars Electric—but, in any event, such a car would not be ready for sale for years. That may be because it would be tough to keep the price down— not to mention to draw enough power to fully fuel a car—with photovoltaics spread across its body, even if manufacturers used the superefficient, super-expensive ones employed on satellites.

Still, the news is a possible ray of sunshine for an alternative-fuel car market deflated by word that hybrids led the decline in U.S. vehicle sales last year and that the Challenge Bibendum—an alternative car show sponsored by Michelin—set to be held in Rio de Janeiro this year will be delayed until at least 2010 because of "increasing financial constraints of several of Challenge Bibendum's traditional partners."

Despite the setbacks, however, interest and enthusiasm for new energy efficient and environmentally friendly transportation modes remains strong among automakers and governments. And some enterprising folks have used Toyota Prius's as emergency generators this winter or tiny Tango EVs (for electric vehicle) to plow their driveway:

It certainly seems that electric propulsion is vying to regain the power it ceded to gasoline engines a century ago. Major manufacturers such as 3M and Johnson Controls have formed a consortium with U.S. government labs to develop longer lasting, more powerful batteries for such vehicles and innovative start-ups, such as U.S.-based Better Place and China's BYD Motor are working on both the infrastructure and the cars themselves (though Warren Buffett-backed BYD won't begin selling its F3DM electric car, already available in China, until 2011 in the U.S.).

So the question remains: how will these cars get their juice? Electricity direct from the sun via photovoltaics or intermediaries like the wind? Or electricity produced by burning fossilized sunshine in the form of coal? Either way you look at it, really, the Toyota Prius is already largely fueled by solar energy, just a much dirtier form.

Credit: Courtesy of Solar Electric Vehicles