|Boiling Point No. 12 - April 1987 (ITDG Boiling Point, 1987)|
GTZ Special Energy Programme summary report 1985.
This is a 65 page report of a survey of wood and charcoal stoves for communal and institutional use, i.e. for 20 to 200 litre pots. The following extracts indicate its Aims and some of its conclusions.
"The survey attempts to support the Women and Energy Project in its efforts to conserve woodfuels in Kenya by compiling and analysing data on:
- the energy and stove mix in Kenyan institutions,
- the wood and charcoal community stove models which are presently manufactured in Kenya, and
- the various groups, private enterprises and experts who are developing or manufacturing improved community stoves. "
"The vast majority of institutions are equipped with two or three different cooking systems in which gas, fuel oil or electricity are the principal cooking fuels, while wood and charcoal play the role of stand-by or emergency energies. The importance of wood and charcoal as emergency energies is based on the higher supply security (decentralized supply structure) in comparison to gas, electricity or fuel oil (central supply structure). In some institutions wood is used because of its lower costs. The cost advantage of wood in comparison to gas is partly offset by the higher efficiency of gas cookers and also by the higher storage, preparation, charging and maintenance costs of wood using kitchens."
"For Kenyan institutions woodfuel energy as well as woodfuel community stoves are commercial items. Excessive woodfuel consumption in institutions is a financial problem, rather than an energy problem. The improvement,production, sale and application of community stoves should, therefore, always be considered under rentability aspects. This will best be achieved, if development funds are spent to support and make use of the existing structure of commercial stove production instead of initiating primary research from scratch."
''Conventional Charcoal Stove
The conventional charcoal stoves, which are widely used in institutional kitchens for Dots up to 50 liters, are simple, portable metal stoves, just like the family size jikos but in a larger size. They are mace out of discarded drums or sheet metal, usually on the order of customers, and they cost between KSh. 300/- and KSh. 500/-, depending on size, quality and location."
"The portability of the stove is appreciated since it allows it to be placed in different locations. In particular, lighting is done outside the kitchen so that the smoke does not cause any discomfort to the cooks.
Since the large pots sit on top of the conventional stoves, to prepare ugali, it needs one cook to stir the maize pap and another cook to hold the pot with both hands so that it is not playing around on the stove or slipping over its edges."
"This conventional stove design features some advantages which is the reason why it is the most widely applied community charcoal stove in Kenya. The advantages are:
Low material requirements (discarded sheet metal) and simple production techniques (like cutting, punching, folding and riveting) make this model available at a reasonable price in all urban centres in Kenya;
Weighing around 15 kg and being made of metal parts only, the conventional model causes no problems of transportation from the artisan's workplace to the location of use;
A great range of pot sizes above 25 cm in diameter can be used on the stove without any alterations or extra expenditure;
The stove is simple to handle just like the common conventional charcoal stove;
Repair or replacemant is possible at any time in all urban centres and even in rural areas when sheet metal is available."
"The stove's lifespan depends very much on the quality of sheet metal and the periods of use. Conventional charcoal stoves with an age of eight years can be seen in some institutions as well as worn out stoves with an age of six months or less."
"Looking at the fuel consumption, five shortcomings can be identified. The stove's energy efficiency is low because:
heat is lost through the single metal wall, heat is lost through the open combustion chamber, particularly when the stove is exposed to wind, it lacks an adjustable air control for the combustion, the cooking vessel is placed on top of the fire bed without an insulating wall at the sides of the pot, and because of a wide and deep combustion chamber which makes it easy to overcharge the stove with excessive amounts of charcoal."
Improved versions of charcoal stove are cement/vermiculite charcoal ,grate, around the combustion chamber
Versions of the popular clay liner, charcoal, domestic stove have been produced in the community sizes, 58 cm diameter, selling at about KShs 500/-.
The report then goes on to look at the larger stoves for pots of capacity 50 to 200 litres. It compares the Alpha Laval, steel tipping stove; the Bellerive/UNEP clay, brick and metal stove; the Italproduct steel and cast iron stove, the Specialised Engineering Co stainless steel stove and the multipot brick stoves of the Ministry of Social Security. Their dimensions, prices etc. are set out in the table, but performance or efficiency figures are not given.
The report stresses the vital importance of studying the requirements of the institution e.g. need for hot water, and all aspects of the kitchen situation before attempting to choose a stove design. Case Studies are given to show the results of ailing to do this. It concludes that for any large insttution, professional energy advice is needed to choose the best combination of fuels - gas, charcoal, wood and of stove types. Wood fuels are usually standby energies, used for cooking in a share of 10-15% of the total energy consumption.
The survey showed that "the offer of improved community charcoal stoves is poor in comparison to that of wood stoves which have only recently been developed". "Very little field experience is available so far and the models still have a wide area for efficiency improvements". "Wood saving through further design improvements of the tees' models of wood burning stoves is very limited".
An appendix considers some of the Problems b) of energy loss in wood fired community stoves.