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Solar cooker

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Solar Cookers are simple devices that use mirrors and other reflecting surfaces to concentrate the light and heat from the sun to a small cooking area. Although solar cooker technology has been around for decades but it is only recently that its advantages are beginning to be recognized. The initial resistance, because people were traditionally accustomed to cooking with wood, started breaking down when with the increase in both deforestation and population, the need for an alternative fuel began to be felt. Awareness of health benefits from solar cooking is also beginning to spread gradually. According to a World Health Organization estimate, toxic smoke from cooking fire kills 1.5 million women and children each year.

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[edit] Health Advantage

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Using a solar cooker cuts down on greenhouse emissions from cooking fires. Cooking over a fire is estimated to be as harmful as smoking two packs of cigarettes a day, which can lead to many respiratory illnesses such as pneumonia.

The biomass (wood, animal dung and crop residue) used as fuel gives off toxic smoke at about seven times the safe limit set by the U.S. Environmental Protection Agency, (EPA). According to the WHO, every twenty seconds a person dies from this condition known as Indoor Air Pollution (IAP). IAP can lead to lung cancer, low birth rate, cataracts, bronchitis, TB, higher infant mortality and asthma as well as pneumonia and other respiratory infections which are the biggest killers of children under five years of age in the developing world.

To get a clear idea about solar cookers you can take a look at the You Tube Audio Visuals on Solar Cooking and on Solar oven

[edit] Did You Know?

  • Energy consumption in the Third World countries is only a fraction of that in the developed nations. Yet 90 percent of energy consumption in these countries is used for cooking.
  • Poorer families often spend more on fuel than on food.
  • Fuel for cooking comprises mainly wood, charcoal, dung, leaves. Toxic smoke emanating from such cooking causes chronic respiratory and eye ailments, apart from contributing significantly to greenhouse gases in the atmosphere.

[edit] Reduced Emissions

Unfortunately, there is little available data on the number of solar cookers currently in operation on a global scale. Preliminary estimates place the number of solar cookers in regular use, worldwide, as approximately 1.5 million. Though many more cookers have been produced and sold, most people use the cookers infrequently. Assuming that there are 1.5 million operating solar cookers, globally, and that each one cooks an average of 1 meal per day for 3 people, this results in an emissions reduction of approximately 690 million kilograms (equivalent) of CO2 per year.

Distribution

Distribution and promotion of solar cookers are mostly done by international NGOs. The cookers are partially or fully subsidized by these NGOs who also bear the costs of promotion. Significant contribution is made by Solar Cookers International in spreading awareness and cooking skills. See a list of NGOs working on solar cooker promotions and installation can be found here:

It is not only difficult to produce solar cookers locally because of lack of infrastructure and raw material in developing countries, but repair and maintenance is also a problem. In spite of the subsidy, users still find solar cookers expensive because for them wood and dung, which they use as fuel, are free.

[edit] Basic Principles

The basic principles of solar cookers are:

Concentration of Sunlight:

Light and heat from the sun are directed with the use of some device, usually a mirror, to a small cooking area. This makes the energy concentrated and more potent

Light to Heat Conversion

Coloring the insides of a cooking material black helps absorb almost all the sun’s rays and converts it into heat. This improves the effectiveness of the cooker and speeds up the function of the oven.

Heat Trapping

The inside air and the outside air in the cooker are to be isolated. Using a clear solid, like a plastic bag or a glass cover, will allow light to enter, but once the light is absorbed and converted to heat, a plastic bag or glass cover will trap the light inside using the greenhouse effect. This makes it possible to maintain similar temperatures on cold and windy days as on hot days.

[edit] Types of Solar Cookers

On clear sunny days, it is possible to cook noon meal for 4 to 5 people in a normal Box Solar Cooker and also a full or part evening meal, if one desires. Concentrating Cookers can cook food for a large number of people faster than box solar cookers. A Cardboard Cooker could be useful for high solar insulation areas with fewer winds.

Box Solar Cooker

A Box Solar Cooker is an insulated box with a glass cover and with a mirror inside a top lid to reflect sunlight into the box when the lid is kept open. The inner part of the box is painted black. Up to four black painted vessels are placed inside the box with the food which takes an average of 1 ½ to 2 hours to cook. It is an ideal device for domestic cooking during most of the year except during the monsoon.

Concentrating Dish Solar Cooker

A typical dish solar cooker has anodized aluminum sheet as reflecting material with reflectivity of over 80%. It requires manual tracking and has to be adjusted in 15 to 20 minutes during cooking time. With a delivering power of about 0.6 KW it can boil 2 to 3 liters of water in half an hour. The temperature achieved at the bottom of the vessel could be around 350 to 400o C which is sufficient for roasting, frying and boiling. The cooker can save up to10 LPG cylinders a year on full use at small establishments.

Cardboard Solar Cooker

This is a foldable cooker made up of cardboard material having reflecting foil pasted on its inner portion. The outer body is laminated to protect it from sudden rain and to make it more durable. The weight of the cooker is less than half kg. The cooker is used with a black painted aluminum vessel to be housed in a polythene bag while cooking food. For cooking this cooker, it is unfolded and placed in the sun in such a way that the sun rays reflected from the foil fall on the cooking pot placed at the centre of the cooker. Two items can also be cooked at a time by keeping two vessels one above the other in polythene bag in case the solar radiation is very high.

[edit] Making Solar Cooking a Part of Your Routine

  • Right Pots and Pans

It is essential to have the right pots and pans to get the best results from solar cooking. The most important aspect is the pots should not be shiny and ideally matte black, though dark colors can also do. Shine reflects the sun away. The utensils should be light as heavy ones take lot more time to heat up.

  • Solar Cooking

Solar cooker is ideally suited for those who are pressed for time and those who don’t want to make a big deal of cooking all the time. It helps you carry on with what you are doing while it continues to do its work without your intervention. Try your hand at some of the successful solar recipes like “Stir” Fry and Rice , Solar Pizza , Solar Pie

  • Your own oven

Solar ovens are rather easy to make and takes only a few simple tips which you can find in these websites:

Build your own solar oven

Solar ovens made from Pizza Boxes

Solar Box Cookers from two cardboard boxes

Solar cooking recipes

[edit] Mass Solar Cooking

In India scientists have taken advantage of the country’s abundant renewable energy source and began working on solar cookers five decades ago. Today solar concentrating cookers are put up in several places for mass cooking.

Dish Solar Cookers and the Community Solar Cooker have been installed to cater to 10-15 persons and 35 to 40 persons respectively at a time. There is also the Solar Steam Cooking System, which can cook food for few thousand persons by using steam in the kitchen, has been adopted by a number of institutions. In Shirdi, India, a solar steam cooking system has been installed to cater to 3000 devotees every day. What would probably be the world's largest system with capacity to prepare food for 15000 pilgrims is also set up by the Tirumala Tirupathi Devasthanam


The Solar Kitchen, the collective kitchen of Auroville ,Pondicherry, India, has a huge bowl installed to harness solar energy for cooking

[edit] REFERENCES

  • Parabolic Basket Solar Cooker
  • Development of a Comparative Framework for Evaluating the Performance of Solar Cooking Devices
  • Solar Cooking and Health
  • Cooking with the sun

[edit] Useful sites

  • Solar cooking – Frequently Asked Questions