Large solar Cooker. photo credit: Akuppa
How do Solar Ovens Work?
Solar Ovens work by focusing sunlight on a point. Concentrated sunlight is quite capable of boiling water and cooking food, and solar cookers can do just that.
There are three basic types of solar cookers: box cookers, curved concentrators and panel cookers.
Box Cookers
This simply designed cooker is a box with either black or reflective insides. Food is placed inside the box, usually in a pot. The box walls are insulated to prevent heat from escaping. The insides are reflective to direct sunlight at the pot sitting in the box.
picture credit: Annie&John
If the insides are black, this is so the sun's heat will be absorbed and radiated back to the pot inside the box. There are several hundred thousand of these kinds of solar ovens in India alone.
The solar box cooker usually reaches temperatures of 150 °C (300 °F). This is hot enough to cook food, though it will take slightly longer than a conventional oven.
Curved Concentrators
These can cook as fast as a conventional oven. This type of oven can reach high temperatures. They work by having large reflectors or mirrors that direct sunlight at a pot or kettle. There are many shapes for the reflectors, but the most common are parabolic, bowl or cone shapped.
There are several hundred thousand of these cookers in China. Unlike box cookers, cuved concentrators require frequent adjustment, as they need to follow the path of the sun to work properly.
image credit: rangorang
Panel Cookers
These are very inexpensive solar cookers that use shiny panels to direct sunlight to a cooking pot that is enclosed in a clear plastic bag. These ovens can be made from old cardboard boxes and the aluminium foil from cigarrette boxes.
They can be made for about $5 USD. The most common design for this type of oven is called a Cookit.
Photo Credit: Coconino
These two Cookit cookers can reach temperatures high enough to cook rice and pastuarize water.
The plastic bag keeps the warm air close to the pot and the tin foil reflects heat onto the pot.
It's important to keep the plasic bag from touching the pot, as it will melt onto the sides of the pot. Food will take several hours to cook in this type of oven.
Benefits of Solar Ovens Around the World
Solar ovens have been instrumental in improving quality of life around the world. They help prevent deforestation because people no longer need to chop wood for fires. Solar cookers can also solve health problems. This because it requires less effort for people to boil water for sanitation in a solar oven.
A very exciting area of solar cooking is being explored right now. This is solar desalination. In areas of water shortage, solar cookers are being developed to extract salt from the ocean and make drinking water from the sea.
Instructions to build a Solar Ovens