Here is the basic concept for the thermal circuit:
The heat source feeds a heat pipe to a Peltier based thermo electric generator. There are two heatsinks: one on the Peltier and one in between the Peltier and the heat source to prevent extreme temperatures from reaching the Peltier device. A fan turns on when the temperature starts getting too hot as determined by the voltage across the Peltier.
The low input voltage LTC3106 buck-boost regulator converts the voltage from the Peltier to 3.3V to power the PIXL.js board which monitors the BBQ temperature by reading a thermocouple with the MAX31855K.