Well , i am a Long Time friend of those , my First one was a canadian product Working as an hot Air engine (Stirling),Same priciple Like a steamengine ) called Freebreeze with Piston , crankshaft etc.... Huge and , i will ad a Link in a while ...
Anyway since years it seems a welcome Idea to give to Friends with woodburners as a gift , for Sure there are plenty Others now Working with Teg (Thermal Energy Generator) ideas .... Well Long storry short now ... never thought about it until today , but it might not be a bad idea to Blow the warm Air against a Solid Wall , instead of the room Air , (in my case with bad Insulation and Windows ) , but those solid brick walls seem to act now like a masonry stove , but will see, what is prefarable to blow the warm air into the air on /into a brick .... all the best from silli billi