Put together the best solar panels money can buy, superefficient batteries and decades of carmaking know-how and, theoretically, a vehicle might run forever.

That's the audacious motivation behind a project by Toyota Motor Corp., Sharp Corp. and the New Energy and Industrial Technology Development Organization of Japan, or NEDO, to test a Prius that could revolutionize transportation.

"The solar car's advantage is that — while it can't drive for a long range — it's really independent of charging facilities," said Koji Makino, a project manager at Toyota.