I just monitored the booting process on then console and have seen there two errors
modprobe: FATAL: Module cpufreq_powersave not found in directory /lib/modules/4.14.232-ipfire
modprobe: FATAL: Module cpufreq_userspace not found in directory /lib/modules/4.14.232-ipfire
Also O have seen that my fanless system is quit hot on the surface.
However I can see the cpu_freq diagrams in the gui.
What can I do to slow down the CPU in order to save energy.