Ben 2 and Ben 3 Firewood Stoves: Difference between revisions

The Ben 2 and Ben 3 Firewood Stoves serve for cooking in pots up to 28 cm in diameter (Ben 2) or 28 cm to 32 cm or more in diameter (Ben 3). Pans and woks are can also be nested. Dry, thin sticks of firewood of any length are used as fuel.

The thermal efficiency of the cooker is over 40%. Compared to the traditional three-stone fire (with 10% efficiency), firewood consumption is reduced to less than a quarter (75% saving). When the Heat-retention cooking is applied additionally (see: Imma and Dieter Seifert: Notes on Fireless Cooking - Cooking With Retained Heat), the firewood consumption drops to about one-seventh. This small amount of wood can be provided by plantations, which can be harvested annually. Thus, the search of firewood and felling of trees is completely avoided.

If the use of charcoal from kilns is replaced, then the wood saving is even greater because multiples of wood is consumed for the traditional production of charcoal. At the same time, the disease burden by carbon monoxide and nitrogen oxides is inhibited.

For overcoming the firewood crisis it is important on the one hand that the demand for wood is reduced to about one-seventh (demand in a week, which was formerly the daily requirement) and that the remaining needs are covered by plantations, which can be harvested annually.

Simplicity, high efficiency and durability Construction of the stove is very simple. The stove consists of three parts which are placed into one another (see picture).

The operation of the stove is easy, both kindling, as well as the maintenance of the fire on the firewood grate. The stove weighs only about 3 kg; it is portable and can be produced with simple tools (optionally without any machine) of conventional mild steel. In the case of local production especially in developing countries the manufacturing costs are very low (in the order of 10 USD). Thus, the expense can often be saved already in a month. Due to the low costs and high savings, the household may install more than one cooker (or several stove shells), suitable to the pots and pans used.

Only little smoke is produced due to the effective supply of primary and secondary air. The thin steel sheets are not operated at high temperature so that they have a long life.

Net power of the stove is 1.5 kW. Six liters of water can be brought to a boil in less than 30 minutes. For this operation, about 400 g of small, dry wood sticks are required. With a daily consumption per household of 1.4 kg wood, the annual demand is about 500 kg, instead of usual two to four tons of firewood (or more than 7 tons of wood, if charcoal is used).

The efficiency is high due to the proper combustion and the advantageous heat transfer to the pot, caused by the special firewood grate and the adapted stove shell. If solar technology is applied in addition (see e.g. Imma Seifert: Solar Cooking with the Parabolic Cooker), then the demand for wood can be reduced to less than one kg per day per household, even if additional tasks (boiling large quantities of water, conserving fruits etc.) are carried out with the solar cooker.

Advantages of these designs

• Its operation can be learned in less than an hour, because it is probably easier to operate than a three stones fire (much easier to start and maintain the fire, due to effective primary air supply under the grate).

• Thin dry twigs are suitable, which do not harm the tree at harvest or which may be produced in short rotation plantations. Hence the firewood crisis can be completely overcome.

• The stove can be easily produced without requiring special materials or tools because intentionally no insulation is provided and the unhindered primary and secondary air flow enables sufficient low temperature for the thin steel sheets.

• It was expected that therefore the efficiency is not particularly high, but the heat transfer of the Ben stove is obviously very good. Sometimes there is a misconception in efficiency discussions. We should consider that with an efficiency of 10% (= default value from UNFCCC for traditional three stones fire) there is a consumption of 10 kg firewood instead of theoretical 1 kg (at 100% efficiency) , at 25% efficiency the consumption is 1 kg / 0.25 = 4 kg ( i.e.6 kg savings), at 40% efficiency the consumption would be 1 kg / 0.4 = 2.5 kg (7.5 kg savings), and at about 66% efficiency the consumption is 1 kg / 0.666 = 1.5 kg (i.e. 8.5 kg savings). The diagram below shows that the major savings over the three stones fire occur at efficiencies up to 40%.

Efficiency

• Spreadsheet showing efficiency of these stoves in comparison with other woodstoves

Recent news and developments

• April 2016: Dieter Seifert has a new design for the tripod for the Ben 2 and Ben 3 Firewood Stoves, which has several advantages. The tripod consists of three equal parts which are welded together. The parts are made of round steel with a diameter of 6 mm. The documents below show this new tripod.

• May 2015: Dieter Seifert writes: Today I have made tests with the Ben 2 and 3 Ben Firewood Stoves. It is almost unbelievable, but the efficiency is always higher than 40% and if one does not heat up too fast (i.e., the power under 1.5 kW is), the result is almost no smoke and approximately 350 g thin wooden sticks can bring 6 liters of water to a boil in 25 minutes. Of course cooking is much more convenient with a large parabolic solar cooker (We have used the AlSol 1.4 for many years.). The Ben ovens are so easy to prepare (2 sheets provided with holes and bending, drilling a ring and three legs and turn, turn 4 bars hairpin-shaped and assemble everything) that the cost in firewood crisis regions would be well below $10 USD. The combination of heat-retention cooking and Fuel-efficient wood stoves with the solar cooker is ideal. The solar cooker can do much more than just cooking. It is a peace-creating technology that is so urgently needed.

Construction plans

• General description
• Annex A) Drawings and list of parts
• Annex B) Description of serial production
• Annex C) Drawings and list of parts of devices
• Annex D) Photos of devices
• Illustrated instructions for building the tripod stand without welding (también en español)

Contact

Dieter Seifert (Wiki article)
Siedlungsstrasse 12
D-84 524 NEUOTTING
Germany

Email: bdiv.seifert@t-online.de