One of the many interesting things shown off at the IDF this week was a notebook from Compal with lid cooling:
They call it lid cooling, and it works like this. In a normal laptop, the heatpipes over the CPU pull off energy and transfer it to a heatsink. A fan then sucks in air and blows it at high speed over the heatsink. As laptops get thinner and hotter, this means higher speed air, less efficient heatsinks, and in general, lots of noise. It also takes power to move that air, so it drains battery life in addition to being annoying.
Compal, as you can see above, has a much better solution. The heatpipe pulls the energy off, and that is routed through the hinge and on to a big aluminum or carbon plate that backs the screen. The lid looks like any other, just a normal laptop, and under full load, feels a little warmer.
The big trick here is the hinge, you need something that works like a normal hinge, transfers heat and is totally reliable. This is not a minor engineering challenge, but Compal claims to have done it.
The results are that the system can dissipate the heat from a 17W CPU, about half of the worst case energy from a high end 35W laptop part. Since you almost never pull the full TDP from a CPU, unless you are really pounding it, you will almost always be able to run fan free on this system.