BTW, to elaborate on the ectool suggestions. The safest method would be to use ectool to set the fan_off temperature to something higher like 65C (and fan_max to something like 80C in case of a runaway): [RESPONDED] Changing the fan temperture points with ectool and to set thermald to limit throttle the CPU at say 60C. In theory, the fan should never turn on in that case, and if you do end up going past it for some reason, the fan table should still automatically turn on.
You can of course use the ectool to simply set the fan duty to 0% and do the same limiting with thermald, but you won’t throttle until PROC_HOT which may get you in trouble.
You may also want to disable turbo for better efficiency as well (there are a few tools, like tlp, auto-cpufreq, or set it directly via sysfs. - tlp is nice since you can easily execute a script to swap whatever profiles you want on ac/battery pretty easily (you could do this via udev as well. You’d have to test yourself in a fully passive situation whether you end up with better overall performance w/ turbo or not (I’d assume off, since turbo tends to go beyond the power/perf sweet spot).