I'm the author. I've updated the article to clarify. It's powered by a 220/110V USB power supply outside the fridge, USB micro cable in through the door seal,

I'm the author. I've updated the article to clarify. It's powered by a 220/110V USB power supply outside the fridge, USB micro cable in through the door seal, and then the 5V/12V-converter lives inside the fridge. The converter is also used to adjust the speed of the fan.