| Boiling Point No. 26 - December 1991 |
Research on Chimneys, Hoods & Inglenooks
by Pete Young, ITDG
In our last issue of Boiling Point (No. 25) Emma Crewe reported on the WHO meeting "Consultation on Indoor Air Pollution". We had hoped to publish a summary of the proceedings in this issue but we regret the full report has yet to be released by WHO. As soon as it is released we will bring you the highlights.
What is clear is that there remains an enormous gap in the knowledge, and experience of applying successful solutions to the problem of smoke removal and/or its reduction to recommended levels.
Our own experiences suggest that chimneys are only effective for closed systems and where the pots are specifically made to fit the stove. Good examples of these include many Chinese stoves and the institutional stoves used in Kenya. However, their very high cost means they are only affordable in certain situations and are not easy to disseminate en-masse through conventional marketing techniques.
Where hoods and inglenooks exist, as in Sri Lanka, the simple 2 pot chimneyless stove has become extremely popular and is proving to be relatively easy to disseminate through normal market channels.
From next year ITDG is planning to take a more active role in researching effective ways of removing smoke. To help us in this role, the British Coal Research Establishment has agreed to provide its technical expertise. In Boiling Point No. 28 we hope to start with a paper presenting some of the theory and scientific principles that have to be met in order for a chimney or inglenook to work successfully.
Please let's have your comments and experiences on the removal of smoke.
by Peter Young, ITDG ITDG is collaborating with the University of Sheffield on testing clays for cooking stoves. This work started in 1988 and was funded for 3 years by ODA. The aims are:
to produce an appropriate methodology for the testing of clays in Asia and Africa for stove production, which will assist potters worldwide to produce more durable œramic cookstoves. The 5 objectives are:
1. To establish the laws governing the performance of earthenware stove clays.
2. To develop recipes for clay mixtures, and methods of preparation and recommendations for firing to manufacture durable ceramic stoves.
3. To produce a methodology suitable for in-country use that will identify clay suitability and provide recommendations for improvement.
4. To test the use of the methodology by at least two independent agencies prior to the production of a manual.
5. To produce a handbook detailing the testing methodology for testing centres and organisations
involved in ceramic stove production.
Research Results The research to date has characterized ceramic stove clays and correlated these with the tendency to crack in use. Cracking is due to a combination of raw material used, thermal and residual stresses. The ratio of clay content to non-clay content should be 1:1 (max) to minimise shrinkage on drying. Thermally-driven cracks are most likely to be arrested in materials containing higher concentrations of coarse particles i.e, non clays.
Residual stress was identified as being equally important and its relationship to stove design and fabrication is being further explored in collaboration with a Dutch funded project being carried out in Thailand. A manual will be produced by ITDG in 1993 and a research/ advice centre established in Sri Lanka in 1992/3
About the Aprovecho Institute
The goal of the Aprovecho Technology Project Group is to design, build and disseminate tools which a) fulfill a basic need as efficiently as possible, b) fulfill that need without damaging the ecosystem and c) can be made in any large town in the world. Each tool or machine should provide obvious benefits, at low cost, to the individual, society, and the world at large.
Who are we? The Aprovecho AT Project Group's members come from diverse backgrounds with diverse skills. Currency involved are an engineer, international consultant, handyperson, solar box cooker enthusiast, dome designer and inventor. We welcome people who have ideas for new tools, interest in construction and experimentation, or skills to assist in dissemination.
Work to date So far, we've developed and built the following devices. We are in the process of preparing detailed plans for each item:
The Downdraught-Downfeed stove - A smokeless, very efficient, low mass, wood fired stove, nicknamed
"The Rocket", used for cooking and baking, built out of natural materials and cement. The Downfeed-Downdraught bread oven - capable of baking 15 loaves. Hayboxes - fireless cookers which retain the heat of a stove in an insulated box. Solar Ovens
Contact us at:
The AT Project Group
Larry Winiarski, PhD
The Aprovecho Institute
80574 Hazelton Rd
Cottage Grove, OR 97424, USA