During the dog days of summer, it can get so hot that you might think you could fry an egg on the sidewalk. If you're a budding scientist, you may have even tried it. But have you ever WONDERed if you could really cook food using the Sun?
Guess what? You can! And many people around the world do so every day. For example, people who live in rural areas of India, China, and Sudan rely heavily on the Sun, because they don't always have electricity in their homes.
To cook effectively using the Sun's rays, you need a special piece of cooking equipment called a solar oven or solar cooker. Solar cookers work by focusing sunlight onto a small area. That area is used as the cooking surface and it can become very hot when the Sun's heat energy is concentrated upon it.
Solar cookers have reflective panels on top that are usually made of a shiny metal, like aluminum, silver, or chromium. The panels are built at an angle or are curved so that, when sunshine hits these metal surfaces, the sunlight gets reflected downward. In this way, the panels focus the sunlight in a small area to concentrate the Sun's heat energy.
If you've ever walked barefoot on blacktop on a hot summer day, you know that asphalt can feel a lot hotter than the air. That's because of its color. Darker colors absorb light which converts to heat, so any dark surface sitting out in the Sun will be a lot hotter than a lighter one.
Solar cookers use this scientific principle to cook food, too. Underneath the reflective panels, solar cookers usually have a box where the food goes. The walls and floor of the box are painted black, and the cook uses a black dish or pot. The dark color makes the food get hotter than it would in other cookware.
Have you ever noticed that your home stays warm even when it's cold outside? That's because of the scientific principle of heat retention. Your home is insulated, and the insulation keeps the heated air inside.
Solar cookers rely upon heat retention, too. The box holding the food has insulated walls and a clear lid that allows concentrated sunlight in but keeps the heat from escaping. These features improve heat retention and make the temperatures inside the box stay high. How high? A solar cooker can reach temperatures as high as 250º Fahrenheit (121º Celcius).
Have you ever been told to wash your hands before and after handling food? That's because uncooked food can sometimes carry bacteria that can make us sick. Bacteria like temperatures that are nice and warm — around 140º Fahrenheit (60º Celcius).
Cooks use ovens to raise the temperature of food in order to eliminate harmful bacteria. For example, most meats need to reach an internal temperature between 145-165º Fahrenheit (about 63-74º Celcius) in order to be safe to eat.
Most people who use solar cookers use them to cook foods that are less likely to contain bacteria, such as beans, rice, soups, and stews. Solar cookers aren't like the microwave or the oven in your kitchen. They don't get as hot and they need a long time to cook food. However, in many places in the world, solar cookers are an important tool for cooking food.