|Boiling Point No. 21 - April 1990 (ITDG - ITDG, 1990, 44 p.)|
Or a Piece of Kitchen Furniture
1 The CAT Experience by Augustine Xavier- Centre for Appropoate Technology, South India
A stove is a necessary piece of kitchen furnishing of every household or institution. Stoves make an entry into kitchen for various reasons. Some people, even the poorest, go in search of a good stove and acquire it whatever the cost and install it in their kitchen as ar. absolute item of their kitchen furnishing and find great pleasure in the use of it. Some others are constrained to permit its entry into the kitchen as a piece of material just to look at. Eventually they may even hate such a stove and demolish it at the earliest opportunity.
In this article, CAT - Centre for Appropriate Technology, a voluntary organisation working in the Kanyakumari District of Tamil Nadu, South India since 1980, shares its own experience in the field of ceramic pottery liner stoves.
In the wake of the energy crisis in India, the Government of India commenced a new department known as Department on Non-conventional Energy Sources (DNES). Improved Chulha is considered as the most immediate means of mitigating the drudgery of women, health hazards and loss of forest cover. By its use the dwindling of the forest cover can be reduced to the minimum possible and limit the ecological damage. However, the biofuels (firewood, twigs, animal and agricultural residues) may have a longer term role and must be considered directly by policy makers if the behaviour of the entire national energy system is to be understood and planned. This requires a substantial change in the wood stoves and appliances used. Though the programme is conceived to be modified from time to time by research and development to make it attractive to the people and used by them, various factors stand in the way.
CAT from its very inception in 1980 tried to solve the problems faced by people on account of energy crisis and depletion of forests. When DNES commenced its improved chulha programme, CAT came forward to implement the same in different parts of Kanyakumari District from the year 1984. By this time we have installed more than 15,000 Mahan (pottery liner smokeless) chulhas in this district.
ITDG stepped forward to collaborate with CAT in funding and research & development on improved stoves. This research & development programme had many objectives. The first objective was to improve the national programme and to make it a grand success by improving manufacture and installation of stoves and motivating people to appreciate improved chulhas. The second objective was to provide employment opportunities to the potters and to enhance their standard of living. (Presently the pottery industry in South India faces serious crises for want of market and the potters seek alterr~ative employment leaving. the pottery industry. CAT's avowed objective is to help potters to improve their own industry). The third and the most important objective was to make various prototypes of improved pottery liner stoves suited to different cooking practices, types of fuel used and the needs of the people.
Our Project Engineer and ITDG engineers, basing on the feedback of our own experience in the stove programme, designed five prototypes of ceramic stoves and tested them (Anagi I, Kumaru, Anagi II, Deepam and Rasi). They possess at least 20~o efficiency. Some are smokeless and some others are not. The design aspects may be seen from Figures I to II.
Fig 1 - Anagi I
We intend to market Anagi I and Rasi. Anagi I is a two pot chimneyless stove; whereas Rasi is a single pot smokeless stove. The common advantages of both stoves are the same. There is no metal part in them. The combustion chamber is designed to use any type of fuel, such as coconut husk, leaves, saw dust etc. available in the locality. The second pot of Anagi I receives the same amount of heat as the first. They cook faster than any traditional stove. On account of the above advantages we expect people to come forward, even the poorest section, to pay for them and see them as essential items of furnishing in the kitchen.
Fig 2 - Rasi Stove
Our research & development wing has not yet concentrated its attention on the use of LPG gas and kerosene for cooking purposes in urban and semi urban areas of the district. We infer that almost 40% of the urban population use LPG stoves. Invariably they have to use kerosene stoves also as supply of LPG gas is limited. The cost of kerosene stoves varies from Rs. 25 to Rs. 150/-. Some of the designs available here in the district are also shown in figures 3, 4, 5, 6.
Heat Pipes for Solar Cooking
In BP.20 we published a letter from E.K.Krishna RAO of the Indian Institution of Engineers referring to a solar, steam cooker. In the following paper extract he describes how a heat pipe can be used to convey the heat from a solar concentrator to a suitable form of cooker such as a slow cooker.
The heat pipe enables heat to be conveyed in quantities and with great efficiency to a point of application separated from the source. This is the equivalent of an electrical conductor for transmission and distribution of electrical energy. The principle of the heat pipe is very simple, and is illustrated in Fig. 1.
Fig 1 & 2 - Principle of Heat Pipe
In its simplest form the heat pipe is an evacuated and totally sealed conduit, in which a fluid is entrained. When placed vertically, the heat transfer fluid flows to the lower end by gravity. Whets heat is applied to the lower end, the heat
flowing in causes the fluid to boil off, and the vaporised fluid condenses at any point along the pipe to abstract the latent heat. In order to maintain intimate contact with the heat source, the input end is internally lined with an absorbent material that can absorb the fluid.
The heat pipe may be topologically modified to serve the purpose in hand. The portion of the heat pipe in between the points of abstraction and the source may be insulated, vacuum jacketed or provided with a reflecting jacket to minimise the losses in transmission. Since the heat pipe interior need not run full of transport fluid, there is considerable saving in weight, and the system would have a low thermal inertia.
The sink may be merely a hot water heater, a steam raising drum or the input end of an absorption type refrigerator system. The system possesses great versatility and is capable of operating processing systems, drive engines to provide mechanical power and provide refrigeration. Depending upon the scale of power, the heat pipe may be made of any size.
Fig. 2 shows a preferred manner of obtaining solar energy through a parabolic concentrator. The heat pipe may be supported along the equatorial axis parallel to the earth axis and the concentrator arrangement swung round to track the sun constantly. Many methods of automatic tracking are available. A water heater marketed in Australia uses the pressure of water controlled by a pneumatic differential heat sensor to achieve automatic tracking. The arrangement is reported to be capable of collecting 39% more energy than a non-tracking collector of same apperture size. This is of interest in making solar energy utilisation effective in rural areas.