If as I believe Daniel intimated, he has cold (tap temperature) water available behind a water valve and a fan to circulate the oven air through a heat exchanger
I still do not understand what he has. I don't go with intimations. They often turn out to be wrong. Mine do, anyway. Let's discuss this after we see a schematic and description. Perhaps there was one during his presentation but I did not take screen shots, and I don't recall the details.