I dug around a bit, and the reason behind your "LCD cooler" turned out to be incredibly interesting, in my opinion:
First off all, apparently LCD devices being listed as coolers under acpi are a thing, and not just a strange feature of your laptop - there are some more examples of those floating around online. If you do
acpi -c yourself, you can list your coolers' states.
After some googling, it turns out that the
sysfs driver is responsible for the thermal management. From its documentation:
The generic thermal sysfs provides a set of interfaces for thermal
zone devices (sensors) and thermal cooling devices (fan, processor...)
to register with the thermal management solution and to be a part of
So we're looking at a driver that can both read thermal information from sensors, and control the cooling devices.
The documentation explains what the possible types for cooling devices are:
String which represents the type of device, e.g:
- for generic ACPI: should be "Fan", "Processor" or "LCD"
Now that's quite interesting. Apparently "LCD" somehow is a type of cooling device.
Doing some more digging, I managed to find a paper by the developers of
sysfs. It describes that finding a good thermal management solution became increasingly more necessary, due to handheld devices popping up. This ultimately lead to the development of
In section 6 of the paper, they talk about Intel's Menlow Platform, which is a handheld platform (~5 inches screen size). The paper states that "relying only on the ACPI standards was not enough because sensors available in the platform were capable of doing more things than in ACPI 2.0."
There we have it.
sysfs was invented, with its first practical use being on Menlow. The authors list multiple components of the
sysfs thermal management, one of which is:
ACPI thermal management, which has its thermal zone driver (ACPI
thermal driver) and cooling device drivers (processor, fan, and
video driver) registered with the thermal sysfs driver
The most important part follows in section 6.5:
The following cooling devices are registered with the thermal sysfs
driver on Menlow:
ACPI video throttles the LCD device by reducing the backlight brightness levels.
ACPI can reduce the backlight brightness of your screen, to make it produce less heat. Therefore, what does this make your screen? A cooling device! Weeell, sort of.
So here's the solution to your mystery ;)
If you have the time and interest for it, I'd suggest reading the paper. It's written in a nicely understandable fashion, so there's lots to learn.