I've constructed a smokeless outdoor wood boiler for heating my house this winter. It is designed to work as is, but I am actively modifying it to achieve better efficiencies. Here's what it looked like right after I installed it:
Here's a close up on the door:
The firebox is fairly small, but due to heavy insulation and adequate air supply, combustion is smokeless. The drawback is 4 hours between load times for now:
The boiler is an inside out design. Instead of a firebox surrounded by a water jacket, I placed a vented tank in the back of the firebox:
Here's some numbers on the initial design:
Max inside temperature measured at 1246 *F and rising. My thermocouple is only rated to 1400, so I removed it before seeing how high it really gets in there.
Max outside temperature is 255 *F, most of it is 190 *F. This is an obvious place for improvement. I am very pleased with the effectiveness of the homemade insulation, however.
Max exhaust temperature is 343 *F. My goal is to get this down to 275.
Planned improvements:
1. Install a baffle on the top back portion of the tank. This was just done this morning and I will be testing its effectiveness throughout the day. Preliminary observations show it forces the flames to swirl around the tank better.
2. Install a heat reclaimer. This will use the heat from the body of the stove to preheat combustion air, putting that waste heat back into the fire.
3. Install a secondary air injection system. I'm getting smoke free combustion and a lot of blue flame in there, but I think adding preheated air at the end of the grate will boost things further.
4. Install firetubes in the boiler tank. I'm teaching myself how to weld, and I felt this was out of my reach at the time. I've got another tank that I will do this with when my skills improve.
5. Insulate the hydronic lines and possibly the heat reclaimer.
I hope you find this project entertaining. Let me know if you have other improvements you can think of. Questions are welcome too.