I saw this picture and thought I would link it here.
The two vent pipes come from a mass heater in another room. There is an air space from top to bottom in the mass which heats the air which thermo cycles though the circuit. The metal panel radiates heat into this room too.
Here is the rest of the web page.
Edit: It looks like they use inline fans to move the air because the two panels are some distance from the heater.
