In many sunny countries, the roads are far hotter than their surroundings, and in any case take in large amounts of heat.
There are several ways in which you should be able to harness the energy in daily heating roads. One is to use the temperature difference between the scortching hot roads in the summer, and the plants around them. (Did I hear "stirling"?)
If you could attach a long water pipe alongside a road, it would probably be able to gather a lot of heat. Or putting small motors along the way, each storing a bit of energy...
Or I can think of various other ways. Will be happy to hear your ideas.-- pashute, May 15 2008 [+] run stainless steel piping under the surface of the road like a reverse radiant heating floor: on urban/suburban streets it could replace/supplement hot water heaters... keep an eye on the ashphalt depth though; the closer to the surface the pipes are, the more effective it is but you don't want them getting broken/mangled.-- FlyingToaster, May 15 2008 Wonder how many cars you could power slot racer style....-- rascalraidex, May 16 2008 Laudable effort, but another reason to dig up roads [-]-- AbsintheWithoutLeave, May 16 2008 I suspect that due to the low efficiency of extracting heat from a maximum 100F temperature difference, this will only become cost-effective if/when robots can build it for essentially free. Good try though.-- sninctown, May 16 2008 I know this is used in sustainable building design: when roads or parking space are part of the same structure (eg car park on the roof) you place a tube system in the tarmac or its foundation. water is pumped trough the tubes and the heated water (a few degrees warmer is enough) is used to power the airconditioning of the building. This principle is also considered for airports; airplanes generate a lot of heat when taking off.-- nutty professor, May 16 2008 I gotta go with AWOL on this one. Either the roads would be getting torn up to work on the systems inside, or the systems would be getting torn up by roadwork.-- Noexit, May 16 2008 [NuT and NoXT] no need to pull up roads. It works in the middle section of main roads where there's a garden "island" (big temperature diff there). Also at the end of long interstate roads where there's no pavement. A small pipe along the edge would do the job!-- pashute, May 18 2008 In parts of south east asia, such as Vietnam paved roads having sunshine are often used to spread harvested rice to dry before dehusking.
el dueno-- el dueno, May 21 2008 Every 5 miles or so, there could be instant soup stations, where we can get some Ramen or tea.-- plynthe, May 21 2008 random, halfbakery