| Boiling Point No. 36 - November 1995 |
by Kedar N. Nag and A.N. Mathur; University of Udaipur; India
In India, cooking and water heating consume 43 per cent of the total domestic energy. A recent survey of a rural area of Karnataka State has shown that the domestic sector alone consumes 87 per cent of energy which is comprised mostly of fuel-wood, cow dung, farm waste and oil. In the urban areas of Delhi, Bombay and Calcutta, commercially available energy sources meet 66 per cent of their needs for domestic use and in other rural and urban areas 12-19 per cent.
In order to reduce the use of commercial fuel in urban areas, the technology to harness solar energy through the use of solar cookers and water heaters has been developed. The popularization of solar-based domestic equipment will depend on sociological, technological, political and economical factors. Normally it takes about a decade to shift from one source of energy to another.
A box-type solar cooker, known as an 'Udaipur Cooker', with a metallized polyester reflector on both sides of the box has been fabricated and costs less than a box type solar cooker with flat collector sides. The collector plates of both cookers are made of 25s gauge aluminium sheets painted black. The temperature of the Udaipur cooker was 15°C to 17°C higher than that of the flat-side box cooker with and without food. The maximum temperature during the month of August was 104°C in the Udaipur Cooker in comparison to 87.5°C in the box-type cooker.
The metallized polyester film (90 per cent reflectivity) pasted on parabolic section hardboard has been provided on two side walls to reflect solar radiation on the container. The focus of the parabolic reflector is at the centre of the 'collector'. The double glass cover reduces the heat-convection losses due to wind. The outer box, made of wood, is painted with enamel paint. Rubber strip seals are provided around the lid of the cooker.
The above article was published in 1983 in the Indian journal Agricultural Mechanization in Asia, Africa and Latin America.
The reported design and performance of the 'Udaipur Cooker' seem to be better than that of the many solar box cookers 'invented' and promoted in the subsequent 13 years but it has still not been widely taken up.