Geoscience Reference
In-Depth Information
and cooking, and have earned numerous humanitarian awards for the improvements they have
brought to the lives of poor people in places like Honduras, Ethiopia, Malawi, and Uganda. The
use of rocket-stove principles has expanded into efforts to provide low-cost high-efficient space
and hot-water heating.
So, if you wish to burn a fuel efficiently and cleanly for cooking and/or heating, here are
Larry Winiarski's rocket-stove design principles (Still 2002):
1. Insulate, particularly the combustion chamber, with low-mass, heat-resistant materials, such as
perlite or rock wool, in order to keep the fire as hot as possible and not to heat the higher mass of
the stove body.
2. Within the stove body, above the combustion chamber, use an insulated, upright chimney of a
height that is about two or three times the diameter of the chimney before directing heat to any
active surface (griddle, pots, etc.).
3.Heatonlythefuelthatisburning,i.e.,leavethebulkofthefuelstickingoutofthestove'scombus-
tion area and burn just the tips of sticks (or other materials) as they enter the combustion chamber.
The object is to
not
produce more gases or charcoal than can be cleanly burned at the power level
desired.
4. Maintain a good air velocity through the fuel. The primary rocket stove principle and feature is
using a hot, insulated, vertical chimney within the stove body that increases draft.
5. Do not allow too much or too little air to enter the combustion chamber. We strive to have stoi-
chiometric (chemically ideal) combustion: in practice there should be the minimum excess of air
supporting clean burning. In other words, there should be enough air to burn cleanly (essentially
zero smoke), but not too much to burn the fuel more rapidly than necessary, or to cool the heating
surface with excessive air flow, so you may wish to choke the draft to the point where the fire
smokes a little, then open it up just until the smoke disappears.
6. The cross-sectional area (perpendicular to the flow) of the combustion chamber should be sized
within the range of power level of the stove. Experience has shown that roughly 25 square inches
will suffice for home use (6 inches in diameter or 5 inches square). Commercial size is larger and
depends on usage.
7. Elevate the fuel and distribute airflow around the fuel surfaces. When burning sticks of wood, it is
best to have several sticks close together, not touching, leaving air spaces between them. Particle
fuels should be arranged on a grate.
8. Arrange the fuel so that air largely flows through the glowing coals. Too much air passing above
the coals cools the flames and condenses oil vapors.
9. Throughout the stove, any place where hot gases flow, insulate (use rock wool, perlite, or
something similar) fromthe higher mass ofthe stove body,onlyexposing pots,etc., todirect heat.
10. Transfer the heat efficiently by making the gaps as narrow as possible between the insulation
covering the stove body and surfaces to be heated, but do this without choking the fire. Estimate
the size of the gap by keeping the cross-sectional area of the flow of hot flue gases constant.
Ex-
ception:
When using an external chimney or fan the gaps can be substantially reduced as long as
adequate space has been left at the top of the internal short chimney for the gases to turn smoothly
