|Boiling Point No. 12 - April 1987 (ITDG, 1987, 36 p.)|
The paper, dated April 1986, consists of a 3 page general description of the system, followed by 17 pages of technical details and test reports. The following is a brief extract from the description:
"Large peak loading due to lighting and/or cooking is to be avoided in Nepal, as hydro power is one of its major energy sources. This is especially so for stand alone power plants, that are not connected to the national grid.
This paper describes a proposal, in which 200W is sufficient for a rural household's energy needs. Power per household can be limited cheaply and effectively to 200W, which is sufficient for cooking as well as lighting.
Spreading the cooking load is done by a combination of heat storage and low wattage cooking. This technology should prove very beneficial to rural villages with micro hydro schemes in trying to cut back on the use of kerosine and firewood.
As 80% of the energy required for cooking goes into heating up of the water (see Bob Yoder's 'Energy storage for domestic cooking in Nepal'), it seems wise to use water as an energy storage medium. Water can be heated up at off peak times by using a large insulated aluminium pan and a low wattage heating element.
Such a pan (8 ltr. capacity) has been developed at low cost using a double dekshi design. A 200W mica heating element is fitted inside, together with a hermoswitch, which keeps the water temperature at 80 C. Once end temperature is reached, only 100W is needed to keep it up. This hot water will be used for cooking rice, deal, making tea, etc. Besides this, it might find other aplications as well, such sterilising drinking water, cleaning.
Because of its insulated design, heat losses are minimal and 200W is sufficient to keep things softly boiling. When the lid is taken off however, the boiling stops, but water temperature is maintained at 100°C.
The pan can be used for cooking rice, deal, porridge, boiling milk, tea, etc. It can not be used for frying, baking or roasting. This still has to be done above a wood fire. Even though power is very low, cooking times will be as usual when starting off with hot water. When using cold water, cooking times will be extremely long. The cooker will be easily dismissed then.
Time sharing between cooking and lighting in the evening is easily done, as food is kept hot inside the pan, due to its good insulation. The implication, however, is that people have to change their cooking habits. Cooking has to be done in the afternoon before it gets dark."
A possible timetable is discussed of how and hen the cooker is to be used alongside other household activities.
The author acknowledges that the capital and operating costs are high compared with a free fuelwood stove and that it would require major changes in the cooking and social habits of the housewives and so perhaps the whole family. Several stoves have been in use and found satisfactory by project staff and organized field tests are now in progress. We look forward to receiving reports. Ray Holland of ITDG comments as follows:
Ben van Wijhe has done more tests on his 200 watt electric cooker. It seems to me to be a very promising method of using electricity more efficiently for cooking, particularly when used with a micro hydro plant. He envisages using the cooker to store heat as hot water, thus cutting down cooking times and only switching the cooker off when lights are needed (in this case a fixed power supply of 250 W was available).
Technically the system has a lot to recommend it. It overcomes some of the problems of the storage cooker of cost and size, but does require considerable change to existing cooking habits. It offers a very interesting possibility for using a low wattage domestic electric supply efficiently for cooking and lighting. Poorer members of the community would not be able to afford the tariffs or the pans. there are also technical problems of making the pans so that they are durable and safe. 'However, I believe it is very promising and if the social acceptability :an be demonstrated there would be very strong arguments for Government subsidies for electric cooking in a country like Nepal with severe deforestation problems (the Nepal Government already makes a grant of 50% of the electrical generation equipment or Rs 1 Lakh, whichever is lower)·"