One for a Friday. Think of speeding cars, racing round a track. Not exactly green, or environmentally friendly, is it? More Jeremy Clarkson than Jonathon Porritt...

But what if you throw more than a little photovoltaic technology into the mix - harnessing sunlight to drive those racing devices? We take a look at the use of Solar Cells to power some interesting racing machines. And just in case, you think people don't take this seriously, just check out the work of the Dutch racing team, Nuon Solar Team and their Nuna racing machine.

Moving down the size-scale, how about a "display of raw solar drag racing power". This is how, somewhat tongue in cheek, this video is described by one DrSkippy, featuring Solar-rollers and their "1381 Solar Engines" - a race between "FlatTop" and "2-Cell" versions.

Note that you can build these engines yourself. Instructions on constructing these slow-motion devices can be found on a Solarbotoics website called Beam Online. A schematic, parts list, and circuit notes can be found for the "1381 Solar Engine". See www.beam-online.com/Robots/Circuits/1381.html

Finally, we feature the work of South Australian college students and a road race from Ceduna to Adelaide, aimed at promoting renewable transport alternatives, including solar... Details of Damascus College's efforts can be found at http://dcebt.com

That one moves at a fair lick, even if we wouldn't fancy taking it round Staples Corner on a Monday morning. But hey, we salute their ingenious efforts. If there were more solar-powered devices on the road, and less Chelsea Tractors, the world would be a better place...