Design, Fabrication and Performance Analysis of Solar Oven

I. INTRODUCTION

Today, every country draws its energy needs from a variety of sources. We broadly classified this source as conventional and non conventional.

1.1] CONVENTIONAL SOURCES

1) Fossil fuels,

2) Hydroelectric power,

3) Nuclear fission,

1.2] NON-CONVENTIONAL SOURCES

1) Solar energy,

2) Wind energy,

3) Bio mass and bio gas,

4) Ocean thermal energy,

5) Tidal energy,

6) Geothermal energy.

Energy is the prime mover of economic growth and is vital to the survival of a modern economy. Future economic growth crucially depends on the long-term availability of energy from sources that are affordable, accessible and environmentally friendly.

In many equatorial regions, native trees and bushes are being cut at an alarming rate to meet the growing demands for agricultural and, industry, and fuel wood and charcoal. The environmental consequences of this deforestation are severe, ranging from soil erosion and climate changes to flooding and the destruction of farmland. Moreover, dwindling supplies of wood mean that people must spend more time and energy in the search for cooking fuel.

One alternative is to use kerosene or liquefied petroleum gas. But these are often imported and transporting them to remote areas is usually difficult. The next alternative is to use the sun, particularly in equatorial regions where solar energy is abundant.

Solar energy has the greatest potential of all the sources of renewable sources and if only a small amount of this form of energy could be used, it will be one of the most important supplies of energy especially when other sources in the country have depleted.

The solar power where sun hits atmosphere is 1017 watts, whereas the solar power on earth surface is 1016 watts. The total world wide power demand of all needs of civilization is 1013 watts. Therefore, the sun gives us 1000 times more power than we need. If we can use 5% of this energy, it will be 50 times what the world will require. the energy radiated by the sun on a bright sunny day is approximately 1kw/m2, attempts have been made to make use of this energy in raising steam which may be used in driving the prime mover for the purpose of generation of electrical energy.

The basic research in solar energy is being carried in universities and educational and research institutions, public sector institution, bharat heavy electrical ltd and central electronic ltd are carrying out co-coordinated program of research in solar energy. Various application of solar energy is:

1) Solar cooking,

2) Solar heating,

3) Solar electric power generation,

4) Solar distillation.

A Solar Oven is a way of harnessing the sun's power to cook food. A metal box and heater forms the simplest solar oven. A set of large mirrors focus sunlight to a single point may also be added. On a sunny day a black baking tray or cooking pot can convert thousands of watts of light directly into heat. Temperatures in the oven can reach 400 degrees F (200oC).

Apart from the obvious need for sunlight and the need to aim the solar oven before use, using a solar oven is not substantially different from a regular oven. Humanitarian organizations are promoting their use worldwide to help slow deforestation and desertification caused by the need for firewood with which to cook.

1.3] HISTORY OF SOLAR COOKER:

The first known western solar cooker was built by Horace de Saussure in 1767. He reported successfully cooking fruits at that time with initial temperatures of 189.5 F (87.5 C). Our solar boxes now successfully reach temperatures between 275 -300 F (135 -149 C), depending on size and location of use. SOLAR BOX COOKERS INTERNATIONAL (SBCI) was formed in 1987 as a non-profit volunteer organization to respond to inquiries and provide central coordination of volunteer donations of time and money, develop educational materials, and promote knowledge of the technology and use of SBCs worldwide.

A solar box cooker is an insulated box with a transparent top and a reflective lid. The top can usually be removed to allow dark pots containing food to be placed inside. The box usually has one or more reflectors with aluminum foil or other reflective material to bounce extra light into the interior of the box. Cooking containers and the inside bottom of the cooker should be dark-colored or black. The inside walls should be reflective to reduce radiative heat loss and bounce the light towards the pots and the dark bottom, which is in contact with the pots.

The inside insulator for the solar box cooker has to be able to withstand temperatures up to 150o C (302 oF) without melting or off-gassing. Crumpled newspapers, wool, rags, dry grass, sheets of cardboard, etc. can be used to insulate the walls of the cooker, but since most of the heat escapes through the top glass or plastic, very little insulation in the walls is necessary. The transparent top is either glass, which is durable but hard to work with, or an oven cooking bag, which is lighter, cheaper, and easier to work with, but less durable. If dark pots and/or bottom tray cannot be located, these can be darkened either with flat-black spray paint (one that is non-toxic when dry) or black tempera paint.

The solar box cooker typically reaches a temperature of 150 oC (302 oF); not as hot as a standard oven, but still hot enough to cook food over a somewhat longer period of time. It should be remembered that food containing moisture cannot get hotter than 100 oC (212 oF) in any case, so it is not necessary to cook at the high temperatures indicated in standard cookbooks. Because the food does not reach too high of a temperature, it can be safely left in the cooker all day without burning. It is best to start cooking before noon, though, depending on the latitude and weather, food can be cooked either early or later in the day. The cooker is also used to warm food and drinks but can also be used to pasteurize water or milk.

Solar box cookers can be made of locally available materials or be manufactured in a factory for sale. They range from small cardboard devices, suitable for cooking a single meal when the sun is shining, to wood and glass boxes built into the sunny side of a house. Although invented by Horace de Saussure, a