Gosh, Just my opinion.... I could be wrong.....but.... I'm sorry, but that doesn't look to be the best designed coal burner, not even close. Where are the cast iron grates? Where is the ash pan? How do the ashes shake? And then, he says he's got 110K invested in 18 units.....that's $5,555 per unit in materials? I see about about half that. And, it's not a closed system? I don't care how much insulation it has, it's going to have massive heat loss. Are they ASME? Doubtful. See any reviews? Can you find it on the Internet? No & no. This looks like a home made nightmare & he's trying to get out from under it before anyone wakes up.