Stack-fed, Heat Exchanging, Biomass Briquette Stove
By: Harold Westerich, Redwood City, CA
Please contact Harold directly for questions about this stove.  e-mail
Click Pictures to Expand 

ALSO, see another home heating person, Norman Desrosiers, and what he has done to heat his home. download his PowerPoint, 4 Meg, pptx   Norm has done a lot of experimenting and developed meaningful enhancements to the process.

The stove is located outside the house and acts as a heat exchanger through a double wrapped flue pipe. It is indeed vertically -stack-loaded directly from the top (the fuel is fed in through the top of that front vertical tube below which is about 6 ft tall). The stack is then sealed.

The hot exhaust is then directly ducted /sucked up through a stainless steel flue/chimney/heat exchanger, about 16 ft straight up in fact. Around this core chimney, he has wrapped a larger sheet metal outer pipe.  He then attached smaller conventional sheet metal tubes onto the 10' tall heat exchanger pipe near its upper and lower end. These serve to feed exhaust air from the house into the annular space between the chimney and the larger sheet metal tube- DOWN and out from that tube back into the house, as heated air, acting as a heat exchanger in effect.

The system is positively charged in that air is force fed by fan into the upper duct so that if any leaks occurred it would vent off to the atmosphere and not into the house.

Harold next to vertical stack-fed cross draft heat exchanging stove. Stack feeder is the shorter vertical rusty, creosote caked, square, heavy walled steel tube ( he is planning to resolve this with a better design of the top cap). The sheet metal halfway up this rusty tube was used as heat shield during tests       

The rusty but very hefty square steel pipe, with a loosely positioned galvanized sheet steel heat baffle around its lower half which he is pointing at, is the feed tube for the briquettes.

The tall galvanized stack in back is a heat exchanger for his flue.. The whole issue is of course regulating flash back up the feed tube while keeping moving parts to the minimum..

The taller tube of sheet metal is the heat exchanger. Core tube inside this is stainless. The larger exterior tube acts as a heat shroud.. The air inlet tube (coming from the house ceiling /  attic) is the upper horizontal sheet metal tube. Air is blown in and down the annulus of this larger vertical tube to be ducted into the house at floor level from the base

Grate in Combustion chamber. Briquettes fall down thru the rusty vertical air sealed stack to rest on the upper grate. Ashes fall off to lower pan. Heat is ducted to rear and up and out the chimney (behind the front feed stack /tube shown). Air flow is coming in through the front door:

Stove core box is square heavy walled steel tube same size as stack a baffle surrounds this fire box. Secondary air fed in thru channels in side wall and into back of stove just beyond the combustion zone.

Last night I lit the fire and left the air damper open a little wider than usual. As you can see in the picture I had to jam a triangular piece of metal into the damper so that it would not slide open. The stove body was entirely glowing red and to look into the air inlet was like looking at a welding arc.

The mixture is a combination of paper, sawdust and leaves

The flue contains a 5/8" shaft 16' long that has many pieces of expanded metal welded to it. The expanded metal scrapes the inside of the flue so that soot and ash does not build up an insulating surface. this expanded metal also acts as heat transfer fins that are in contact with the inner flue wall.

This is an extrusion press with a 60" handle and 2" work end. It produces a 4" x 4" extrusion with a 1.25" hole. The output is about one inch per minute but has a very simple operation; Load the hopper, force material into the piston, pull the large lever down. Finished material extrudes out the end onto a board for cutting into various lengths.

12" long logs stacked to dry. These logs are of various combinations of paper/cardboard pulp, saw dust, and coffee grounds. So far the best recipe for pressing a nice looking log is about 50% paper/card pulp with 40% sawdust and 10% coffee.

This is the wide open piston loading chamber. It holds about two cups of wet material. the hopper holds about 5 gallons of material.

This is a side view of the lever action. As the lever is pressed down, the pressure applied to the piston increases until it locks in the fully compressed position.

Thanks to Richard Stanley from the Legacy Foundation for authoring some of this page.