Solar cookers are powered by direct sunlight. They don't use fossil fuels like oil or coal. In the past, people only made solar cookers as science experiments. No one really believed that solar cookers could actually be used to make food. Now that technology has become more advanced, people can use solar cookers to make several dishes such as macaroni and cheese, paella, and chili.
A solar cooker works by concentrating the sun's rays in one location to maximize heat and energy. It then insulates and retains the heat for sustained cooking at high temperatures. Conductive materials allow the heat to pass to the food and convection currents move the heat to cooler areas that need it.
Mirrors and other reflective materials are used to direct the sun's rays into a specific area. The heat and energy are all concentrated in one place and make the cooker more efficient. Ray tracing is the science of following the path of rays and calculating where rays are likely to hit. Combining ray tracing with reflective materials is a basic element of solar cookers.
The Greenhouse Effect is the phenomenon by which the Earth's atmospheric layers trap carbon dioxide and other greenhouse gases. These gases absorb the sun's heat and raise the earth's temperature. The same effect can be applied to solar cooking. Solar cooking reduces the release of harmful greenhouse gases, so you help the environment when you use a solar cooker. Many solar cookers use vacuum technology to insulate and retain heat because glass is not a good insulator.
Cooking is a heat-powered system. Thermodynamics is the study of how heat, work and energy interact in a closed system. Therefore, the principles of thermodynamics are essential to successful solar cooking.
Radiation is the sun's most powerful component. Solar cookers capture infrared radiation, which is the element of the sun's radiation that carries heat. 53% percent of sunlight is infrared radiation. Solar cooker efficiency hovers at around 80% which means that solar cookers are not yet capable of harnessing 100% of the sun's infrared radiation.
Conduction is heat transfer through contact. Heat forces atoms to move faster and generate energy, transferring it to the particles that it makes contact with. Heat transfer in the solar cooker's pot area happens via conduction. Metals such as stainless steel conduct heat better than wood.
Convection currents are the result of the rise of warm liquid or air and the corresponding descent of cold air. The cold air is heated when it falls to the bottom and rises again in a circulation pattern.
Simple panel solar cookers are the cheapest solar cookers to make and help people reduce energy costs. The pot is made from a cardboard box lined with foil and the reflective panel can be made from plastic wrap. The simple panel solar cooker is portable and easy to construct, but not some models are more durable than others. Also, it's not possible to fry food with a simple panel solar cooker.
Basic box solar cookers also harness solar energy to cook food. They're better than simple solar cookers because they reach higher maximum temperatures due to the improved insulation that protects the contents from the elements. The plastic or glass top keeps heat inside. The pot is placed inside the insulated box.
Advanced panel solar cookers rely on the creation of a dead air zone that surrounds the pot. This gives the pot additional insulation. Two options for creating the dead air are to cover the pot with a glass bowl or with heat-resistant plastic. The pot is surrounded by a circle of collapsible reflectors. Advanced panel solar cookers are easier to maintain and can reach higher temperatures than simple panel cookers. In comparison with parabolic solar cookers. they don't absorb sunlight as well and it may take some time for the food to cook.
Parabolic dish solar cookers rely mostly on reflection instead of insulation, which differentiates them from panel solar cookers and box solar cookers. Parabolic solar cooker temperatures can get higher than 250 Celsius, allowing the user to fry eggs and bacon with the solar cooker. Other solar cookers don't reach temperatures hot enough for frying.
Advanced box solar cookers have a better reflective system and a rack for the cooking pot, which keeps heat off the floor of the solar cooker. Its size makes it difficult to carry, but it can be used for baking and the chef doesn't have to keep tracking the sun and turning the cooker.