I have a Dell XPS 15 laptop (model number l502x). In both windows 7 and windows 8, I have been able to select power options (power saver, high performance, etc.). In the configuration settings for these options, there was a cooling option, where I could choose between passive and active cooling to save power. When I switched to the passive cooling mode, the fan would remain off most of the time, unless I switched to a program that required a lot of cpu/gpu power, during which the cpu and gpu would start working harder, and produce more heat, turning on the fan.
I do not believe that the fan was OS controlled, though. I had previously tried to download and use a program (speed fan) on Windows to see if I could control the fan, and it did not see any fan, so I assume that the fan is BIOS controlled, and that Windows just alerted the BIOS to my current cooling preference.
Is there any way to have a setting on Ubuntu (12.10) to switch to passive cooling to shut off the fan and save battery life?