In the cavity of the fermenter between the outer body and cone sits a 30 Watt 12V heating element.
Unlike standard heating element/sources that directly heat liquid, this is designed to heat the environment in between the walls of the fermenter, which in turn heats the liquid.
It is similar to controlling the temperature in a temperature controlled room. This way, the beer is not heating at a single small point, it is evenly and ‘calmly’ heated.