(Sorry for bad English, if someone would correct it, I'll edit and change it) Thin tubes with fluid are located under parts of the car that are exposed to direct sun: Under the roof, under the dashboard cover, front seats, back seat baggage panel, motor hood, and maybe even inside the steering wheel
The fluid is circulated with low power or possibly passive solar power from hot absorbance location of car to external underside of car, the heat leavs the car to the surrounding air via a heat sink (small spikes on the underside of the car, with a bit of insulation between it and the car floor).
If there's a breeze or when car in motion, this works extremely well. Even in regular parking conditions, the car will be cooled to the external temperature.
If a bit of evaporation is allowed, this can even cool the car, to lower temperatures than the outside.-- pashute, Jun 16 2009 Former art used in this idea Chilled SeatsChilled Seats HBI (Halfbakery Idea) [pashute, Jun 16 2009] More prior art used in this idea Passive AirconUsing water evaporation for chilling, (but unbaked problem recovering evaporated...) Similar name but different idea [pashute, Jun 16 2009] And another idea used here Passive Heatsink Car Bodywell I'm also talking about a heatsink, but not the whole car body, and using a radiation system in interal parts of the car which gather heat, moving it to the passive sink. [pashute, Jun 16 2009] If the tubes are anything else then existing structural elements converted to heat-pipes, the additional weight & bulk would surpass the benefits. If the tubes are indeed heat pipes, there might be some problems with low external temperatures and the hands freezing to the steering wheel. But if only external elements are cooled [+].-- loonquawl, Jun 16 2009 or you could open the windows....-- WcW, Jun 17 2009 opening the windows doesn't help cool the steering wheel. covering it does. and very thin tubelets with a tiny bit of liquid can do a good job of heat conducting and moving.-- pashute, Jun 17 2009 yes, opening the windows will eventually cool the steering wheel.-- WcW, Jun 18 2009 somehow the phrase "hundreds of tiny tubes" just doesn't appeal to me from a maintenance/repair perspective.-- WcW, Jun 18 2009 Given that the car has a free heat source (engine cooling system) why wouldn't you use an absorbtion AC system (similar to the gas powered refrigerators used in camper vans).
To move heat with a passive system requires a large area of pipework, because the temperature difference is small. An evaporative system increases the temperature difference at both the cold end (in the car) and the hot end (outside) and requires much less area, so could use a small radiator under the boot floor.
As an added bonus, the system would continue to work for some time after the engine was switched off.-- Twizz, Jun 18 2009 Simply have a roof- or- dash-mounted solar panel power the vehicle's heater/AC fan when the engine is off. This would reduce heat buildup inside the car. Of course, the fan motor will burn out quicker than normal.-- whlanteigne, Jan 12 2013 whlanteigne, I have that in my '97 Chevy pickup. I use a marine battery, 2 CPU fans (cleverly hidden in the doors) and a household thermostat converted to operate on 12 V DC.(thanks to David K.!) The marine battery performs double duty in camping season, as it runs my stereo as well. (and everything in any trailer I might bring.)
//small spikes on the underside of the car// If you accidentally run over a pedestrian, spikes ensure you don't get sued by survivor.-- Brian the Painter, Jan 12 2013 random, halfbakery