http://www.solarbotics.net/bestiary/pix/2420_solarrollers/2420_slotcar.jpg

ummm,
is that supposed to be solar powered?

Almost looks like a solar cell.

IS a solar cell.

http://www.solarbotics.net/bestiary/pix/2420_solarrollers/2420_slotcar.jpg

I only found a picture, the write up seemed to have been removed as the link was dead.

I also googled and found a few refrences to solar powered slot car tracks....

http://web.archive.org/web/20021225093924/http://www.geocities.com/SoHo/Exhibit/8281/slotcar.html

there you go...