Toyota Motor is trying to figure out how to make a car run forever

A Prius plug-in hybrid that sells for more than 3 million yen offers solar panels as an option

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

That’s the audacious motivation behind a project by Toyota Motor, Sharp and New Energy and Industrial Technology Development Organisation of Japan, or NEDO, to test a Prius that could revolutionise 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 Toyota project manager.

Even if fully electric cars overtake petroleum-powered cars in sales, they still need to be plugged in, which means