Solar Cooker – Working Principles and Types.

We must have tried to cook food or not cooked to boil water under the sun. It does get warm, but it takes time. A solar cooker is one approach. It may be used to assist cut fuel costs and air pollution and prevent deforestation and desertification.

We prepare our food with a solar cooker, which uses the energy emitted by the sun. The solar cooker works on the principle that the sun heats the pot in which food is cooked. The pot’s heating is now accomplished by converting light energy to heat energy. Because concave mirrors reflect sunlight into a single focus point, they are utilised in these sorts of cookers.

In this case, the mirror directs sunlight onto a receiving device, such as a cooking pan. A solar cooker admits UV light rays, but they are converted into longer infrared light beams that cannot escape. Infrared radiations contain enough energy to cause water, fat, and protein molecules in the food to vibrate and heat up. 

Conduction is the mechanism by which light energy interacts with the receiver material and converts light to heat. We can optimise this transition by employing heat-conducting and heat-retaining materials.

Working Principle

The concentration of sunlight: Sunlight is concentrated and directed into a small cooking area using a mirror surface with a strong specular reflection. Concentrating sunlight by multiple orders of magnitude makes it possible to create magnitudes powerful enough to melt metal and salt. Such high temperatures are not necessary for solar cooking applications used in homes. Market-available solar cookers are made to reach temperatures between 650C and 4000C.

Light Energy to Heat Energy Conversion: Concentrated sunlight is directed at a receiving device, such as a frying pan. The contact between the light energy and the receiver material aids in the conversion of light to heat via a process known as conduction. The conversion rate is increased by using materials that conduct and hold heat. To maximise absorption, the pots and pans of the solar cooker should be matte black.

Heat Energy Capture: Convection is decreased by isolating the air within the cooker from the air outside. Using a glass cover on the pot improves the absorption of light from the top of the pan, reduces convective energy loss, and increases the heat storage capacity of the cooker. Glass allows light to pass through while blocking infrared thermal radiation.

Types of Solar Cooker

Solar Box Cookers

Solar Box cookers (box ovens) can cook the same food as a normal oven or slow cooker. They have an internal chamber (“box”), as the name implies, even though it does not have to be square. Reflectors are used to focus glazing to let more sunshine into the box is used to let sunlight into the box, trapping heat, and insulating is used to keep as much heat as possible. On a bright sunny day, commercially produced box ovens may achieve 400o. Box ovens are suited for classroom building and cooking and may be quickly created from inexpensive or recyclable materials.

Solar Box Cooker

Stuff required

• Storage box for files or equivalent box approximately 12′′ x 15′′ x 10′′
• 1/2  sheet foil-backed foam insulation board per oven
• 12″ x 15″ pre-cut plexiglass
• 20 feet of aluminium duct tape
• Aluminium foil, 18″ x 21″
• a wooden stick, dowel, or pencil
• A pair of scissors
• Construction paper in black, 12″ x 15″

Box solar cooker DIY

1. Cut insulation material. Every oven needs:
   • 12″ x 15″ (1 piece) 
   • 12″ x 9 1/2″(2 pieces)
   • 15″ x 9 1/2″(2 pieces)
2. A piece of insulation should be placed at the bottom of the box.
3. Put insulation pieces all the way around the box’s inside walls.
4. Tape all seams, including those at the box’s bottom, sides, and top.
5. For a reflector, line the interior of the box lid with foil.
6. Use black construction paper to line the oven’s inside bottom.
7. Put the glaze on the oven’s top.
8. Utilising an aluminium tape “hinge,” fasten the box lid to the oven along one long side. The rod or stick is used to tilt this top in order to let in more light.

Outcome:

In order to heat up the box before the food can be cooked in the solar cooker, the glass sheet helps to trap heat inside the box, and the mirror concentrates light onto the box.

Parabolic Reflector Cookers

Parabolic cookers achieve the greatest temperatures and may be used to fry or grill food without the need for cooking bags or pot covers. Reflectors are used in parabolic cookers to focus a significant quantity of sunlight onto a single point of focus, where temperatures can approach 500o. Parabolic-shaped cookers may be created in the classroom using discarded satellite dishes or huge umbrellas. But the temperature is at the focus point and can reach extremely high levels. While cooking, certain safety precautions should be used.

Parabolic umbrella cooker

Materials

• huge umbrella (minimum diameter: 120 cm)
• (From an emergency “space” blanket) Mylar
• aluminium duct tape
• hacksaw
• handmade paper
• White glue or spray-on adhesive
• A pair of scissors
• a pot holder (metal plant stand, small tripod, etc.)

Parabolic solar cooker DIY

1. Open umbrella. Using one of the triangle templates, portions of the interior of the umbrella are out of craft paper.
2. Trace enough pieces to cover onto the mylar the interior of your umbrella made from the template you created. Sections should be cut out.
3. Working outside or in a well-ventilated environment, spray glue one portion at a time to the interior of the umbrella (putting the mylar pieces after spraying the umbrella). Try to get rid of as many wrinkles and bubbles as you can. A rubber roller or a plastic card (such as a credit card or driver’s licence) might be useful. If you’re White glue is used to thin it with a paintbrush until it spreads freely.
4. Wrap the aluminium tape over the outer edges.
5. Use aluminium tape to seal up any exposed or slack seams between pieces.
6. On a sunny day, take the umbrella outside, cut the stick, and handle where the pot stand will be. Set the umbrella on the ground and direct the stick at the Sun. Mark the location on the handle where the Sun’s rays reflect the most.
7. 3″ below your target, cut the stick (shorter). This will allow you to position your pot at the umbrella’s focal point.
8. When cooking, place your cooker on the ground, facing the Sun. To keep your cooker pointing toward the Sun, you may need to put something behind it.
9. Because you want the bottom of your pot to be in the focus point (3′′ above the top of your stick), the plant stand or tripod must rest on top of a portion of the cooker. Make tiny slits with scissors to allow the legs to pass through the cooker and rest securely on the ground below.

How to prepare food in a parabolic cooker

1. Following the recipe, mix or prepare the food for the cooker.
2. Put the cooker in a position such that the umbrella faces the Sun. Set up your pot stand, so the pot is the centre of attention. Keep in mind that anything at the centre of your cooker will heat up quickly! Additionally, it is suggested that you put on sunglasses when using a parabolic cooker.
3. You may use open frying pans with parabolic cookers; fill your pot or pan with your food.
4. The pot holder should be situated on top of the frying pan. Monitor what you eat. You may burn it using a parabolic cooker.
5. Move the cooker periodically for 10 minutes and observe the Sun as it crosses the sky if you’re cooking for a long period.

Solar Pressure Cooker

To explain how solar pressure works, let’s build a parabolic solar cooker.

Materials needed:

1. Take an old TataSky receiver’s parabolic dish.
2. Cut solar reflective film into small equal-sized pieces.

Construction:

1. Now, sanitise the dish’s outside.
2. Apply the reflective films to the full receiver’s surface, as shown below:
3. Make sure there are no bubbles caught inside the films.
4. Connect the reflector to the stand now.
5. Place the cooker on a holder that has been set up in front of this place.

We may prepare food in a pressure cooker using the parabolic solar cooker in this manner.

Result

The sun’s energy is concentrated using parabolic solar cookers.

This tip may quickly heat the bottom of a pressure cooker to exceptionally high temperatures if it is pointed towards it.

Frequently Asked Questions

1. What are Solar Cookers and their importance?

Solar cookers are among the most basic cooking tools. It is also safe because it does not utilise fire and is environmentally beneficial because it does not need fuel. It cooks meals by harnessing the force of the sun. It is often constructed as a basic box into which you serve your food. The box has a lining made of reflective metal and is topped with glass. Then it employs the sun’s energy to cook your meal according to the specified temperature. The meal was prepared completely. Solar cookers are so economical, environmentally benign, and simple to operate.

2. What are the advantages of a Solar cooker?

Advantages are

• Pollution-free.
• They are fuel-free.
• Solar power is a free resource.
• low cost of management.

3. What are the disadvantages of a Solar cooker?

Disadvantages are:

• At a specific period of the day, we may use solar energy.
• We are unable to utilise it at night, during inclement weather, or in the winter when it is foggy.
• Compared to conventional cookers, it takes longer.