How to improve combustion in a stove

• Make sure there is good draft into the fire.
• Insulate around the fire to help it burn hotter. A hotter fire burns up more of the combustible gases and produces less smoke.
• Avoid using heavy, cold materials like earth and sand around the combustion chamber.
• Lift the burning sticks up off the ground so that air can scrape under the sticks and through the charcoal.
• Placing an insulated short chimney above the fire helps to increase draft and gives smoke, air, and fire a place to combine, reducing emissions.
• Meter the sticks of wood into the combustion chamber to make a hot, fierce, jumpy looking fire that does not make much charcoal. This type of fire will make less dangerous emissions, chimney clogging soot, and creosote. Heat only the burning part of the wood. Do not encourage the non-burning wood to make smoke.
• Limit the cold air entering the fire by using as small an opening as possible. Small openings into the fire also force the cook to use less wood, which can be burnt more efficiently.
• A certain amount of excess air is necessary for complete combustion. Preheating the air helps to maintain clean combustion. How to improve fuel efficiency (get more heat into the pot)
• Increase the temperature of the gas/flame contacting the pot, having the hot air scrape against both the bottom and sides of the pot in a narrow channel.
• Increase the speed of the hot flue gases that scrape against the pot. The fast gases punch through a boundary layer of still air that keeps slower moving gases from scraping against the surface of the pot. Air is a poor heat transfer medium. It takes a lot of hot air to bring heat to the pot.
• Use metal rather than clay pots because metal conducts heat better than clay.
• The size of the fire determines the size of the channel gap in the pot skirt and the maximum efficiency of heat transfer. Smaller fires that can still please cooks but are not too big will be considerably more fuel efficient.
• Use wide pots with large diameters. Using a wide pot creates more surface area to increase the transfer of heat. Make sure that the top of the stove slopes up toward the outer perimeter of the pot.

BENEFITS OF A FUEL-EFFICIENT STOVE

• Due to the reduced need for fuel, there is a decreased impact on the environment, particularly on deforestation in watersheds and habitat, which may also increase soil erosion and mudslides. In addition, they remove dead wood, which otherwise would improve soil fertility and promote healthy ecosystems. All of this combined results in a situation which harms both people and nature.
• The reduced need for fuel also means less time is spent foraging for firewood, a job that frequently falls to women or children. One of the traditional roles for women and girls in the developing world is to collect wood for the cooking fire, and so if less wood is needed to cook then less time will be spent by the women and children collecting wood.
• The traditional household cooking fires produce and fill the cooking area with dense smoke that puts the women and girls that use the stove at serious risk of diseases such as chronic obstructive pulmonary disease and childhood pneumonia.
• In areas where there are tensions between population groups the reduced use of resources can help ease tensions.

MATERIALS AND EQUIPMENT REQUIRED

• 50 standard bricks
• Buckets of clay
• Tape measure
• Old sack cloth
• Reinforcing rods
• Metal sheet 1sqm

THE FOLLOWING PICTURES SHOW THE CONSTRUCTION OF A FUEL-EFFICIENT STOVE BY NKAYI FFA PROFECT PARTICIPANTS SHARED BY EMA

The area required to create the foundation for the stove should be 1100mm by 900mm. A layer of clay approximately 40mm thick must be placed within the foundation area. This type of clay used for pottery for the stove to remain in good condition.

Laying of stove foundation.

Once the clay has been laid then bricks must be placed into the clay in 3 courses using the clay to cement the bricks. A gap is left at the front of the stove that will be the inlet for putting a tray of burning charcoal for the heating of the oven.

Iron rods are held in place using a layer of brick and clay, a baking tray will be placed on the rods with the tray of burning charcoal underneath. A metal sheet is placed above this layer of bricks. On this metal sheet will be the platform for making the fire.

Two more courses of bricks are added leaving two openings in front of the stove as shown in the diagram above the inside of the stove is subdivided in the middle by a single line of 3 courses of bricks.

The pots used to cook with are needed to create the correct sized holes in the top surface of the stove. The pots are placed in the positions shown in the picture. Gaps are left at the back of these openings to allow for the draft of air to leave the burning chamber and out of the house through the chimney.  The chimney opening should be the same diameter as the stove opening and the burning chamber.

Above is a completed fuel- efficient stove that is cover with clay. The stove is lined with clay which is a good insulator.

Conclusion

There are many different fuel-efficient stove models that have been developed such as the Tsotso stove and rocket stove. These models use the same design principles to increase combustion and efficiency of energy transfer to reduce the amount of fuel used.

The fuel-efficient stoves to be constructed in Matobo District will have ovens to add value to the stoves and to increase the use of heat as cooking and baking can be done at the same time using the same heat produced by the fuel. The oven opening can also be used to keep food warm.

The adoption of fuel-efficient stoves is a part of the holistic approach to watershed management as it will be reduce the rate of deforestation in Matobo District.