A solar cooker, also known as a solar oven, is a device that uses sunlight as its energy source to cook food. It harnesses the heat energy from the sun and concentrates it on a cooking area, allowing food to be cooked or heated without the need for traditional fuel sources such as gas or electricity. Solar cookers are an environmentally friendly and sustainable alternative to conventional cooking methods in many parts of the world. In this blog post we will learn about Solar Cooker: Definition, Working, Types and benefits.
A solar cooker, or solar oven is a device which uses the energy of sunlight to heat food /drink to cook it or sterilize (to make free from micro-organisms) it. Thermal energy requirement for cooking purpose forms a major share of total- energy consumed, especially in rural area. Using solar energy for cooking purposes is an attractive and relevant option.
Three design of solar cooker
1 Flat plate box type
-With reflector
– Without reflector
2 Multi reflector box type
3 Parabolic disc concentrator type solar cooker
Working principle of Solar Cooker
Concentrating sunlight: Increasing its heating power.
Converting light to heat :Light absorption converts the sun’s visible light into heat, substantially improving the effectiveness of the cooker.
Trapping heat :The convection heat transfer from inside the cooker to atmosphere can be- reduced by isolating the air inside the cooker from the air outside the cooker. A plastic bag or tightly sealed glass cover will trap the hot air inside. This makes it possible to reach similar temperatures on cold and windy days as on hot days.
Greenhouse effect :Glass transmits visible light but blocks infrared thermal radiation from escaping.This amplifies the heat trapping effect.
Box type solar cooker
A box cooker consists
- Rectangular enclosure made up of inner and outer metal or wooden box with double glass sheet on it and insulated on bottom and sides
- Top transparent glass covers of each 3 mm thick plain glass,
- Reflector mirror
- Cooking pots made from aluminum with blackened coating on outer surface,
- Mechanism for adjusting reflector mirror
- Handle to carry the cooker
The extern dimensions of a typical model are 60cm x 60cm x 20cm height. The temperature inside the solar cooker is maintained from 70°to 110°c. This temperature is sufficient to cook food slowly steadily and surely with delicious taste and preservation of nutrients. Maximum temperature obtained is 140°C in winter and 160°C in summer.
Solar direct radiation and also reflected radiation (from a reflector mirror) enters through the top transparent glass cover and absorbed by aluminum blackened tray kept inside the solar box. The solar radiation entering the cooker is short wavelength.
The glass cover reduces re-radiation losses from absorber surface to outside solar cooker. The solar re-radiation (solar energy leaving from absorber surface) has higher wavelength which is not able to pass through the top glass cover. The blackened surface starts absorbing sun rays and temperature inside the box starts rising.
The cooking pots gets heat energy and food will be cooked in a certain period of time depending upon actual temperature attained inside. The temperature attained depends upon the intensity of solar radiation. Depending on the latitude and weather, time of cooking with this cooker ranges from 1 hr to 4 hrs.
Box type solar Cooker - reflector type
A box type solar oven was designed by Central Arid Zone Research Institute Jodhpur. The solar box type solar oven typically reaches a temperature of 250°C in winter and- 350°C in summer.
In this cooker, practically all types of food preparation like cooking, roasting, baking and boiling can be done within 25 to 75 minutes under clear sky conditions. This solar cooker is ideal for baking purposes. A box type solar cooker consists of a well-insulated semi-cylindrical box made of sheet aluminum and wood.
Two shells are made and the space between them, 7.5cm, is filled with fiber glass insulation. The interior sheet is painted black. A door of a same insulating material is also made for keeping and taking out food.
The window of the oven consists of two transparent glass sheets. Eight reflectors are provided on the oven, four of square shape and four of triangular shape. The reflectors are made from silver glass mirrors. The oven can be manually tilted and oriented toward sun.
The main advantage of this solar cooker is that its efficiency is high because its performance is not affected by wind and there are no chances of dust falling in the cooking spots which is problem in the arid zone of India. Moreover, the food remains warm if kept inside the oven for hours together even after sunset.
Parabolic disc concentrator type solar cooker
Parabolic disc concentrator type solar cooker consists of parabolic reflecting surface as shown in Fig, through which the radiation is concentrated. In this cooker cooking pot is placed at focus of parabolic mirror and is thus directly heated. Maximum temperature obtained 450°C.
It can be used for cooking food items requiring roasting, frying or boiling. It can save on fuel for up to 10 LPG cylinders per year for family having 10-15 persons. Cooking time 20-30 minutes.Approximate cost is about Rs.10, 000.
They generate high temperatures and cook quickly, but require frequent adjustment and supervision for safe operation. Also it requires manual tracking every 15 or 20 minutes. Used for large scale institutional cooking.
Benefits of Solar Cookers
Environmentally friendly: Solar cookers reduce the need for traditional fuels, such as wood or charcoal, which helps reduce deforestation and carbon emissions.
Cost-effective: Solar cookers use free sunlight as their energy source, making them a cost-effective cooking solution, especially in sunny regions.
Healthier: Solar cookers produce no smoke or harmful emissions, which can improve indoor air quality and reduce respiratory diseases associated with traditional cooking methods.
Frequently Asked Question (FAQ)
- How long does it take to cook?
Cooking takes 1.25 to 2 hours. Cooking time depends on intensity of sunshine and the nature and quantity of material to be cooked. Hard meat and pulses take some more time to cook.
2.Are solar cookers safe to use?
Yes, solar cookers are safe to use. They do not produce any smoke or harmful emissions, making them a safe and healthy cooking option. However, as with any cooking device, it is important to follow safety guidelines and precautions when using a solar cooker.
- Does Solar cooker need constant tracking?
If the cooker is placed at the average position of the sun’s transit over the sky, tracking may not be necessary. However, if the cooker is aimed at the sun at start a couple of nudges to reposition it over the 1-3 hour period would be desirable.
- Does Solar cooker require maintenance?
Solar cooker is virtually maintenance free but the glass requires to be carefully handled. Even if it breaks it can be easily replaced. The only other maintenance required is Re-anodizing of black selective coating if it wears off.
- Does food require constant stirring?
Solar cooker requires no stirring because there are no hot spots. The temperature rise is gradual. It is difficult to burn food in Solar cooker, which is well loaded.
- How does the cooked-food taste?
Food cooked in Solar cooker tastes much better than food cooked over conventional stoves. In slow cooking, natural flavors and fiber retains its shape. Cooked food rises to its full volume and is fluffy. The food is always tender and more palatable.
- Are solar cookers cost-effective?
Yes, solar cookers are cost-effective, especially in the long run. They use free sunlight as an energy source, which can help reduce cooking costs over time. Additionally, they require minimal maintenance and have a long lifespan, making them a cost-effective cooking solution.
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Feel free to contact me for tips to improve your article, add three other types of solar cookers and correct many misimpressions. While the text is good in general, it is completely inadequate for inspiring people to cook with sunlight. For example, stating that “Cooking takes 1.25 to 2 hours” shorts the very powerful parabolic cookers which can stir fry many items within minutes, and boil within 20 minutes stews and soups. I would like to help revise the many all-too-brief articles on solar cooking that have flooded the web, some constructed with AI which include contradictory and harmful suggestions.
A solar cooker, or solar oven, is an eco-friendly device that utilizes sunlight to cook or sterilize food, making it a sustainable alternative to traditional cooking methods. By concentrating solar energy, solar cookers can reach high temperatures without relying on gas or electricity, significantly reducing carbon emissions and energy costs, especially in sunny regions. The key types include flat plate box types, multi reflector box types, and parabolic disc concentrators, each designed to enhance efficiency and cooking speed. With minimal maintenance and no harmful emissions, solar cookers not only improve indoor air quality but also offer a healthier cooking option.