"Double burn tile fire" from New Zealand--anyone know about these?

Met a guy from NZ who says these are fairly standard there, and he considered them very efficient and better than wood stoves.  I couldn't get a lot of clarity about how they actually work when he tried to describe it, and googling around I haven't found a schematic that I could readily understand.  I didn't look that much though, but did search permies.com and found no hits for "double burn tile fire".  (Try saying that five times fast).

Off topic of my own thread, but this was interesting -- he also said that Habitat for Humanity uses vernacular (indigenous) styles of building in their international relief work (which they just started in recent years, after mostly being domestic in the USA).  They seem to be open to appropriate tech.  Used a rocket stove that he said burned with amazing efficiency, built from local clay.  

Well I live in NZ and have not heard of this terminology being used.

The only double burners I know of are the ULEB or ultra low emissions burners which externally look like Peter's double shoe box riserless core but inverted.  My one is rated to produce 0.2 g/Kg of emissions in its double burning mode.

The most common type of woodburner in NZ is a steel box with fireboard inserts and controlled air intake. If you did a survey on all the homes heated with wood in this country, you'd find a lot of old Kent fires and similar. Clean air regulations introduced since 2000 now limit wetbacks and slow-burning designs in urban areas, but on sections over 2 hectares in rural areas there are no restrictions.

I've lived here since 2005 and have never seen or heard of a "double burn tile fire."

The double burn phrasing was bandied about in advertising decades back for some models. Efficient burners in NZ probably arose due to Christchurch smog. The ads or early efficient models described in the ads are likely the origin of what the guy told you. It had to do with the conversion to charcoal and burning of gases, then the burning of the charcoal itself. The tile referred to is likely the internal firebrick, which is far more efficient than old style cast iron pot bellied models re: insulative purposes, helping to achieve the high heat for the gas burn.

The coal range with wetback design I'd love to see a comeback for.

Heating, hot water, 2 x a typical stove-top plus an oven for cooking, all in one. The steam the water system threw out could have driven a small turbine easily. Fuel efficiency, no idea... But with what we've learned since the 60's... bring back the (new highly efficient) coal range!

Edit: For marketing purposes, might have to rethink the whole 'coal' thing