The stove body and interior (including the combustion chamber) is low mass and insulated. The heat from the fire goes into the cooking process and is not diverted into the stove.
The heat transfer efficiency is close to optimal resulting in over 40% thermal efficiency. One successful technique is to combine moderate firepower (2.5kW) with very small channel gaps (6mm) around the pot. Burning less wood results in fewer emissions.
Use a clean burning fuel.
An appropriate amount of wood gas is made. The rate of reactions (solid to gas) is controlled by adjusting the primary air or by metering the fuel.
A zone of mixing of air, wood gas, and flame is created using jets of secondary air. The secondary air jets can be powered by natural draft in a TLUD stove or by forced air in both Rocket and TLUD stoves.
The velocity of the jets of air is generally increased to improve the effectiveness of the zone of mixing. However, the cooling effect of the secondary air jets is not allowed to decrease thermal efficiency below 40%.
The amount of flame, air, and wood gas entering the zone of mixing is adjusted until close to optimal combustion efficiency is obtained.
Emissions in the exhaust stream can be further reduced with a catalyst.
Remove the emissions from the living space in a chimney when possible.
The prototype stove moves through an iterative development process by testing one change at a time using the emissions hood. The Water Boiling Test and the Controlled Cooking Test are both used to evolve a stove that is clean burning, fuel efficient, and cooks as well or better than the local model.
The cooking function of the stove is designed by local users. The market viability of the product is determined by field testing involving stakeholders such as distributors, manufacturers, funders, consumers, etc. Market testing precedes and informs manufacturing.
Reducing adverse health effects requires the new stove to be a successful intervention. The intervention involves many infield factors that influence the effectiveness of the whole package. Identifying these factors begins the process of creating the successful intervention.
