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close this bookGATE - 2/96 - Renewable Energy and Solar Energy Use (GTZ GATE, 1996, 52 p.)
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AT Activities

- Efficient and economical: New cookers for Cuban schools
- Thai government supports the dissemination of biogas plants in livestock farms

Efficient and economical: New cookers for Cuban schools
Eschborn - Energy supplies in Cuba have suffered since the collapse of Soviet economic aid. Since 1990 the Caribbean state has had to buy its most important energy raw material, oil, at world market prices. The consequence has been that the consumption of oil had to be reduced to a fifth of its former level.

The impact of the scarcity of oil can be felt everywhere. In factories, productivity is decreasing and in farming animals are again used to pull carts. Also, in many of the island's large-scale kitchens the situation is dramatic.

In many households, but also in school kitchens and factory canteens kerosene and gas were traditionally used for cooking, even in better times. As a consequence of the lack of oil, one goes back to wood as burning material. The cutting of wood leaves visible marks in parks, alleys and in the rare forests.

For the NGO "Eurosolar" this was reason enough to support the Cuban Ministry for Education (MINED) since the beginning of last year to increase energy efficiency in school kitchens. The German Consultancy HEAT (Household -Energy -Appropriate Technologies) advised the ministry on the introduction of efficient cookers which were heated with wood and sugar cane 'bagasse'.
Large-scale kitchens have a special importance in Cuba. Every bigger factory, state institution and school has its own canteen for workers and school children who have a meal in the mornings, at lunchtime and in the evenings. The complete transfer of the cooking from the factories, authorities and schools back into private households would particularly affect working women who would have more duties at home. On the other hand, during times of scarce ressources, the provision of meals through canteens is much more sensible than individual cooking.

In Cuban schools meals for between 300 to 1,000 school children are cooked. Overall, about 850,000 school children have meals at school. The consumption of wood of these schools stands at 100,000 tons of wood per year. This equals the consumption of 30,000 tons of kerosene.

In a two week workshop ten employees of the ministry and the schools were infor-med about the opportunities of more efficient wood burning in school kitchens. Under the supervision of HEAT locally appropriate prototypes of cookers were developed; these can be produced from Cuba's own resources.

But technical problems were not the only topic of the workshop. Also, the irregular supply and bad storage of wood leads to inefficiency. In addition, co-operation between school administrations and cooks was not without problems. There was a need to reduce misunderstandings. And the introduction of wood-saving cookers alone will only lead to marginal improvements, unless at the same time the cooks have a more sensitive approach to cookers, wood and instruments and their awareness towards greater efficiency is sharpened.

Regarding the technology used, it is important that the new cookers are adjusted to the economic and personel conditions in the schools. And finally, everything should be achieved by self-help, without additional help from outside. This was of special importance when designing the three prototype cookers.

Three models of cookers were selected for a pilot test. Two are based on a one-pot-firing system which were adjusted to one special pot. This method is the cheapest and the most efficient. The two only differ regarding the material they use: one is built with bricks and the other one is made of oil barrels.

The third model is based on existing Kerosene cookers. The rings and parts of the cooker were used for the new model, which functions in a way similar to the old Kerosene cookers. Therefore, old cooking habits can be kept and different pots can be used. This type of cooker is not as efficient as the other two models. The effectiveness can however be increased when using the rest heat in the cooker.

The biggest problem when designing cookers was getting the material. Therefore, all the prototypes are made of materials which are available in the country. This means mud and saw dust and recycling products such as old parts of lorries. The construction of the cookers is straight-forward and after a short training it can easily be copied. Maintenance is carried out by porters.

The technical effectiveness of the old open fireplaces stands at between 2 and 8 per cent. The new one pot cookers have a level of effectiveness of 50%. The several-pot cookers have an effectiveness of 25%. Therefore, energy saving ranges between 50 and 90%. In practical terms this depends on the correct use and preparation of the wood.

In another course in January this year, twelve technicians from the Education Ministry developed, with the assistance of the German Consultancy, two prototypes of cookers which can be fired with sugar cane bagasse.

The leftovers of sugar cane are only used as burning material in sugar factories. Since it does not burn fast, it has as yet not been used in canteens. The use of sugar cane bagasse only makes sense in regions of the country where it is directly accessible. This is the case in Sancti Spiritus. This town with 120,000 inhabitants is situated about 400 km away from the capital Havanna in the middle of the island's sugar cane belt.

The emphasis of the course was on experiments with the burning material.Two models were developed. One of the cookers had a ramp and crooked grill, so that the sugar cane bagasse pieces burn more slowly. The second model was specially made for burning the two metre long squeezed sugar cane pipes. Both models have a technical effectiveness of 30% and are particularly simple to use and are clean burning.

The cookers which were developed as part of the project have found a broad range of users. In the course of the last 16 months more than 1,000 cookers in 500 schools were built using these principles. The acceptance for the new cookers is generally very high. The Cuban Education Ministry has made the cookers popular in courses throughout the country. The cookers are now also used in kindergardens. It is foreseeable that they will be used not only in schools, but also in many other large-scale kitchens.

For further information:

JUsinger/Dirk Legatis
Household -Energy -Appropriate Technologies
Limburger Str. 29
61479 GlashBR>Tel. + 49 6174 964077
Fax + 49 6174 61209

Thai government supports the dissemination of biogas plants in livestock farms
Chiang Mai -Since last August the Thai government has been promoting the dissemination of biogas plants developed and tested in the scope of the Thai-German biogas programme at Chiang Mai University. The Energy Policy Office of the Royal Thai Government is supporting the Biogas Advisory Unit (BAU) at Chiang Mai University in the further extension of medium-sized biogas plants. The programme chiefly addresses the pig farms in this region.

Due to uncontrolled handling of manure livestock farms, especially pig farms have caused much nuisance.

Neighbours often complain about the strong smell and water contamination from the farm. On the other side, manure is a valuable raw product and can be utilized to generate renewable energy and festilizer.

Ten medium and large-scale pig farms, in the North and also in Central Thailand, have been using anaerobic fermentation technology in the form of a biogas system developed during 1989-1994 by the Thai-German Biogas Programme in Chiang Mai.

Livestock farms that are not under pressure from the local community can choose a biogas plant of any size in line with their energy demands. But farms which already affect their neighbours' welfare are recommended to adopt treatment systems which ensure a largely odour-free waste treatment.

In the initial phase of the national programme the National Energy Policy Office (NEPO) will reimburse a maximum of 47% of the construction costs to the farm owner of the biogas system, whose design and construction is closely supervised by the BAU. Under the extension programme NEPO gives financial support to BAU to provide the supervision free of service charge to the farms. Farm owners can also access credit for the remaining 53% of the construction and installation costs from the national Bank of Agriculture and Agricultural Cooperatives (BAAC).

The BAU aims to construct 3,000 m3 of biogas systems -about four plants -in 1996 and another 7,000 m3 in 1997. From 1998 to 2001 an annual expansion of 10,000 cbm/year is planned, so that in all plants with a capacity of 50,000 cbm will be installed.

The advantages of these plants became apparent in the five-year Thai-German programme. A relatively complete biogas system which is soundly managed generates energy and ready-to-use fertilizer, and also helps control wide-spread odour, disturbing flies and waste water.

The investments needed for the biogas system depend on the energy utility components. Biogas piglet brooders are becoming very common on the pig farms and an engine-generator set is frequently installed in situations where excess biogas is on hand. If only a limited space is available for the post treatment of anaerobic digester which usually requires a sandbed filter, a mechanical solid separator may be added. Pig farms with sufficient land can integrate wetland with plants to take up nitrogen and salts. The treated water can be used to better exploit drier areas.

It is assumed that 70% of the biogas yield is used to generate electricity mainly for on-farm consumption (electricity driven lighting and pumps). 30% of the biogas yield is used as a substitute for Liquid Petroleum Gas (LPG). The Financial Internal Rate of Return (FIRR) would be 4.8% without NEPO support, and 17% with NEPO support for the farmers.

Related to the 50,000 m3 programme for medium and large biogas systems the project calculated an Economic Internal Rate of Return (EIRR) of nearly 12%. The benefits are mainly the substitution of LPG and electricity, the provision of a valuable organic fertilizer, savings related to the aerobic treatment of agricultural wastewaters and employment opportunities. The analysis is based on the substitution of Liquid Petroleum Gas (30%) and electricity (70%) by biogas.

For further information please contact:

The National Biogas Extension Program in Livestock Farms
from BAU, the Formerly Partner in the TG-BP
Nirandorn Potikanond, Weerapan Kiatpakdee and Ulrich Stoehr-Grabowski
Biogas Advisory Unit
Institute for Science and Technology Research and Development
Chiang Mai University
P.O. Box 111
Chiang Mai 50200