General Science: Solar Cooker

:: Solar Cooker

Domestic Solar Cooker

What is Solar Cooker ?

A solar cooker looks like a simple square aluminium suitcase, with five main components with an outer box measuring 500 x 500 x 165 mm with three containers.

Benefits of using the solar cooker

In an age where domestic fuel costs are rising each year, the solar cooker is a real boon.
Reasonably priced, easy-to-use and completely trouble-free, the solar cooker is an ideal supplement to the conventional cooking appliances.
Can be used 300 days a year.
No fuel required for cooking.
All items can be cooked except the fried and chapatis.
Cooking is safe and clean.
Solar cooking is entirely non-polluting and has no ill effects on health.
Food cooked in solar cooker tastes better, is more nutritious and healthy.
No need to keep close watch during cooking as the process is slow.
Cooking time is around 1.30 to 2.30 hours.
Food remains hot as long as the glass assembly is not opened.
Three LPG cylinders can be saved annually as a result of solar cooking.
Pay-back period is around three years.
Life is around 10-15 years.
O & M cost is almost negligible.

Did you know?

The first box type solar cooker was built by Horace de Saussure, a Swiss naturalist, in 1767! He is said to have cooked fruits in it.
That box type solar cookers can be fabricated using just cardboard and aluminum foil? Check out this website for the design http://www.i4at.org/surv/solarbox.htm
In the 1950’s UN and other funding agencies commissioned studies to design solar cookers. The conclusion was encouraging – that solar cooker can cook food thoroughly and nutritiously and was easy to make and use.
Based on the above study, UN sponsored programmes to introduce them in communities where there was a felt need, but this did not meet with much success.
A World Conference on Solar Cooking was held in Stockton, California, in 1992. (http://solarcooking.org/stockton.htm )

THE INDIAN SCENE: Some of the policy initiatives taken by the Indian Government to promote the use of solar energy in general are:

1981 - Recognising the importance of renewable energy sources as the best alternative to conventional fuels, the Government of India set up a Commission for Additional Sources of Energy (CASE) in the Department of Science and Technology
1982 - A full-fledged, independent department, the Department of Non-conventional Energy Sources, is set up.
1992 - This ‘department’ is made into a ‘Ministry’, called the Ministry of Non-conventional Energy Sources (MNES).
Gave subsidy for box type solar cookers from 1984 to 1994.

MNES is the nodal agency of the Government of India for all matters relating to non-conventional/renewable energy.

For more information click on www.mnes.nic.in

As the MNES felt that the use of solar energy for cooking and water heating was on the increase, the subsidy on solar water heaters and solar cookers were withdrawn in 1993-94. It is interesting to note that the Government continues to subsidize cooking gas, at a heavy cost to the exchequer, but is doing little about solar cookers. With over 40manufacturers of different types ofsolar cookers in the India, the combined capacity is to the tune of 75, 000 cookers pre annum. The manufacturers are mostly in the north - Delhi, Gujarat, Himachal Pradesh, Madhya Pradesh, Maharashtra, Punjab, Uttar Pradesh and West Bengal. The cookers have to adhere to the norms recommended by the MNES and the end product needs to be approved by the Bureau of Indian Standards. We understand that an estimated ‘potential’ demand for solar cookers in India is nearly 10 million!

MNES has also opened Aditya Solar Shops across the country,

which serves as convenient consumer points for sales, service and repair of renewable energy devices.

Box Cookers	Panel Cookers	Parabolic Cookers

When a glass covered chamber coated black inside and insulated all around is exposed to sunlight the temperature inside exceeds 100 degree Celsius, which is sufficient to cook food. More heat can be achieved by having an exterior reflector. The solar box cooker incorporates these features.	Roger Bernard in France came up with this design, where various flat panels concentrate the sun's rays on to a pot inside a plastic bag or under a glass bowl. The advantage of this design is that they can be built in an hour or so, from next to nothing. In Kenya, these are being manufactured for the Kakuma Refugee Camp project for US$2 each.	These are usually concave disks that focus the light onto the bottom of a pot. The advantage is that foods cook about as fast as on a conventional stove. Seen above is one model and there are many others possible.
Slow, even cooking of large quantities of food is possible Takes more than 3 hours to cook	Relatively quicker, but can cook only smaller quantities	Food can be cooked in half an hour. The disadvantage is that they are complicated to make, they must be focused often to follow the sun, and they can cause burns and eye injury if not used correctly.
With a single-reflector box cooker, once the food is cooked, it just stays warm and doesn't scorch.You can put in a few pots with different foods and then come back later in the day and each pot will cook to perfection and stay hot until you take it out.	Some people have reported the need to stir food every once in a while when using this kind of cooker, to ensure that the food heats evenly.	Cooking with a parabolic cooker is very similar to cooking on one burner of a conventional stove. Since the concentrated sunlight shines directly on the bottom of a pot, the pot heats up and cooks very quickly. The food will burn though. So you have to stir it and watch it carefully.
Box cookers with one back reflector don't need to be turned unless you are cooking beans, which take up to 5 hours.	Panel cookers need to be turned more often than box cookers, since they have side reflectors that can shade the pot.	Parabolic cookers are the most difficult to keep in focus. These need to be turned every 10 to 30 minutes, depending on the focal length.