We've already seen desktop PC cases that use their side panels as heatsinks thanks to an elaborate network of heat pipes. According to The Inquirer, notebook contract manufacturer Compal has now developed a notebook cooling system based on a similar concept

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. Where current notebooks rely on conventional heatsinks as well as noisy, high-speed fans to cool their processors, Compal's design makes use of the display lid (a big aluminum or carbon plate that backs the screen) to dissipate heat. 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.