Based on the same principle Franklin designed some fireplaces (not stoves) with – passages built into the bottom, around the back, and over the top of the fireplace. The air in the passages would be warmed by the fire and rise, drawing cooler air in from where cold air naturally winds up – the lowest point. This allows the warm air to continue to rise through the passages – becoming increasingly warm – and finally make its way out through the upper openings to warm the room with a gentle air flow; this provides an added (possibly unanticipated) benefit of drying the air and the room (walls, appurtenences, coats, etc).
It is a really nice concept, since it is self-sustaining (as long as the fire is going, anyway), and it does not require a fan to drive the air. Simple physics – basic natural philosophy.
This looks like a great, low-tech heating system for those bitter cold, sunny days. We don’t really get very many of those in Phoenix, but most other places could benefit from this system.
Like BuzzKill says, the system uses simple convection to heat the air from a low lieing inlet that rises, gets heated, and then exits from a higher outlet. Sweet and simple. The only bit of info missing in the video is what was the ambient temp. while he made the video. Judging by his coat, I’d guess it was quite cool.
The only downside is that it won’t do any good at night. For that, some sort of passive heat storage would be needed to augment this system.