Where I live in Western Mass the DEP and Local BOHs have cracked down on the year round operation of Wood Burning Outdoor Boilers. I've been contemplating adding a solar component to these units to allow for them to be used year round for not only DHW but also space heating early and late in the season. Anybody else explore this option? Any input is appreciated.
The Simple Drainback system (www.simpledrainback.com) has been used a number of times for solar/wood/radiant combi-systems. I've attached a diagram of a system that even has pool heat added! And, to add further simplicity in the design, these are plumbed in thermosiphon so no pumps or controls are needed to move and store heat!
For indoor systems, try www.hilkoil.com for a stainless heat exchanger for indoor wood stoves.
For heating applications, evacuated tubes are hands-down the way to go. I tested tubes verses flat plated during winter conditions. Tubes work a longer day, ran hotter, didn't falter in a cold wind, and actually cost less than comparable sized flat plates. Bottom line, tubes are better.