I like the idea of using a thermal siphon, I'll have to look into the design. Even without using a thermal siphon, flowing the water through the flue gas, instead of the other way around, really does simplify the engineering.
I'm thinking of two rectangular plates three or four centimeters...
I've been lurking on these forums for years now; so much of my idea-seeking brings me here, it's remarkable, even to me, that I've never created an account. Here I am now though, so let's jump in shall we?
Background:
I'm designing an off-grid house for myself. I have most of the details...