The system is called "thermophotovoltaics". Briefly, a gasoline engine heats a light-emitting material which causes a photovoltaic (aka solar) cell to emit electricity. The electricity is then used to power the car's systems. While the idea has been around since the '60s, materials of that era were too weak. Now, new technologies have made light-emitting substances more sustainable. MIT is currently developing a prototype that, depending on the results, could lead to the replacement of the engine alternator. Also, thermophotovoltaics systems may be used in hybrid vehicles in lieu of heavy batteries.
[Source: Technology Review]