|Sustainable Energy News - No. 14 September 1996 (INFORSE, 1996)|
By Per S. Nielsen, Technical University of Denmark Denmark
There are many options for reducing the biomass consumption in the food preparation process. Looking at the total energy chain from biofuel to the final meal, many technical improvements are possible. There are also many options which are non-technical . There are closely related to the cooking performance. In relation to technical options, the choice of fuel, optimisation of heat transfer, and efficient combustion processes are important The non-technical options include, for instance, the use of lid, skills in firing control, and organisation of the food preparation process.
The central problem in obtaining high efficiency for the popular
three stone stove in real life is the firing control. With three-stone stoves,
it is difficult to obtain the optimal distance between fire and pot and to keep
the fire in the optimal combustion state, as heat is lost with large
Peko Pe Tested
The Peko Pe is a newly developed gasifier stove developed by the Norwegian Paal Wendelbo. It is basically a pyrolysis gasifier. (See figure.)
The stove was tested at the Technical University of Denmark and in the Adjumani Refugee Camp in Uganda in 1995
· In Denmark, the stove efficiency was 24-26%burningdry woodchips (10% moisture) with a caloric value of 16MJ/kg of woodchips.
· In Uganda, the tests showed a stove efficiency of 21-23% with a caloric value of 15 MJ/kg of grass.
The idea of the tests with grass in the Adjumani refugee camp in Uganda was to develop the gasifier stove to be able to use as fuel the grass available in the refugee camp, which in any case would be burned in bush-fires.
In the refugee camp, the stove was tested with 20-cm-long grass straw of two different diameters, 3-4 mm and 7-8 mm. Generally, the thinner grass burned better than the thicker grass.
The stove provided heat enough to boil a meal in around 45 minutes after reaching the boiling temperature. The radiated heat made it possible to boil the water for another 25-30 minutes after combustion was stopped. This is a so called charcoal effect. This effect was not seen in the tests on wood chips in Denmark
Further technical options to examine to improve the efficiency of the stove include: changing the number of holes, the height of the chamber, variation of befoul source, and specifying the role of the moisture percentage.
In the camp of 100,000 refugees in Uganda, a workshop was established in cooperation with Accord, a UK NGO and the Norwegian Association for the Disabled.
Technicians, disabled people and women were trained to produce, sell the stoves and cook with the stove. Further aspects to examine are:
· How is it received the cook?
· What kinds of food can be made on the stove?
· Even though the stove is cheap, can people afford to buy it?
· To what extent are people willing to accept preparation of the biomass if necessary?
More info: Per S. Nielsen, Dept. of Buildings & Energy, Bldg. 118, Technical Univ. of Denmark 2800 Lyngby, Denmark. Ph/fax:+45-4525-1949/45934430, e-mail: firstname.lastname@example.org
The Peko Pe gasifier stove. The figure illustrates the pyrolysis in the stove while burninggrass. It shows the combustion 5-10 minutes after ignition where the upper part of the grass is burned. The grass is ignited from the top and placed vertical. The stove is made of 2 fins: an inner combustion chamber and an outer shell. The inner chamber (Ø15cm, 20cm high) has 00.8 cm air-holes in the bottom, in the middle and at the top.