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Design of Solar Cookers

The Box Cooker

The seemingly simple design is actually a family-sized cooker that can handle an entire meal on a sunny day. It features an insulated box with a glass or heat-resistant plastic cover that also serves as an oven door. Sunlight passes through the glass or plastic into a dark cooking area.

Additional sunlight is reflected into the box cooker by a shiny lid attached to the box. 

When in use, supports made of cord and wood hold the reflector above the cooking area.

Cardboard box cookers are light, compact, and easy to store or move. Heavier wooden models are more useful for the backyard or patio. Depending upon their construction, these cookers typically reach temperatures of 120 to 225 degrees.

Slant-Faced Solar Cooker

Many do-it yourself buffs choose the slant-faced solar cooker. These are often highly efficient cookers and very portable, folding to a size of a suitcase.

Hinged reflectors direct the sun’s rays through a slanted glass lid. Some reflectors are made of shiny aluminum; others are mirrored or use aluminum foil glued to a sturdy backing. The reflectors are usually collapsible, folding and clamping onto the top of the cooker for easy carrying

To use, the slant-cooker-face is pointed toward the sun and the reflectors are secured in the open position. Some cookers feature built-in height adjusters for more direct aim at the sun.

Multi-Mirrored, Cone-Shaped Cooker
The cooker style features many small mirrors, curved in a cone-shape around the cooking area. This reflector often spans four feet in diameter and with a lid can double as a patio table.

These cookers reach temperatures, of 300 to 450 degrees and cook food in the same time as a conventional cooker. The cooking area is large enough for a turkey.

Concentrating Cookers

Concentrating cookers, or “hot plates,” employ dish-shaped reflectors aimed at the sky like radio receivers. The reflector is designed so that direct light bounces on to a single point. At this point, a cooking stand holds a pot of food or water. The stand can be attached to the collector or be separate.

Concentrating cookers can generate temperatures of 600 degrees Fahrenheit or more and must be constantly attended as the sun moves across the sky. The reflector must be repositioned to follow the sun and keep the focal point on the food being cooked. When left unattended, concentrating cookers have been known to set wood on fire and even burn the ear of a curious dog unlucky enough to be in the wrong place at the wrong time. These cookers also have a dangerous tendency to tip in windy weather.

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Costs: Cooking while reducing summer cooling bills

Solar cookers can dramatically reduce a home’s cooling needs during hot Arizona summers. For every dollar spent on indoor cooking fuel, electricity costing about $.50 is required to cool and dehumidify an air conditioned home. Solar cookers not only use no electricity or natural gas, but they don’t heat-up the house.

The initial cost of a solar cooker depends upon its size manufacturer and sophistication. Store bought models range in cost from $100 for camping sizes and up to $250 for larger versions.

The cost of homemade cookers depends largely on the builder’s resourcefulness – new materials, for example, cost more than used. Some do-it-your–selfers use only cardboard box, newspaper for insulation, aluminum foil and a piece of glass or plastic. Others include hinged aluminum reflectors, spray in insulation, and tools for cutting metal to make the inside box. Other builders even place their cookers on old rotating television stands for easy adjustment as the sun moves across the sky.

Generally plan on spending $25 to $100 in materials to make a solar cooker that reaches adequate temperatures.


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How Solar Cookers Work

In 1764, French inventor Horace de Saussure produced temperatures of 225 degrees Fahrenheit in glass-covered boxes lined with black cork. Another Frenchman, Augustin Muchot, designed a solar cooker in the 1870’s that was used for many years by the French Foreign Legion.

These solar cookers operated on the same principles as cookers of today. An insulated box is covered with a clear window allowing access to light. The light rays are absorbed by the cooker’s inside surface and are transformed into heat energy. Heat radiates out from the surface and collects inside the cooker. Some of it escapes back through the window or “cracks” in the cooker, but not as quickly as additional light enters.

This process is similar to the greenhouse effect heard about so often in the news today. On a global scale, sunlight is absorbed by the earth and is transformed to heat. The heat radiates into the atmosphere. It either escapes or is reflected back toward earth by carbon dioxide and water vapor in the air. More carbon dioxide in the air means that heat is more likely to build-up around the planet.

Unlike the earth, solar cookers are deliberately designed to keep hot air inside. The cooking area is well insulated and the opening is often surrounded by rubber to seal it when the window is closed. 

These simple cookers also encompass a collector, storage and controls. The collector is a glass or heat-resistant plastic cover that lets sunlight inside. Storage occurs because insulation prevents heat from escaping. Storage is also provided by the food itself, which absorbs heat. 

Controls for a solar cooker are the reflectors. Reflectors help control the temperature by concentrating the sun’s rays onto the cooking area. Temperatures can also be adjusted by repositioning a solar cooker in relation to the sun. If lower temperatures are needed, the cooker can merely be pointed a bit away from the sun’s direct rays.


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The delicious way to save energy and money

As many as 500 people gather each year for an annual potluck near Tucson. They eat vegetables, bread, pie and lasagna – typical foods at many such gatherings. This potluck, however, is vastly different from most because all the food, even the pizza, is cooked on-location by the sun

The group Citizens for Solar sponsors this cookoff each year to focus attention on one device: the solar cooker. These cookers use no electricity or natural gas, consume no firewood, and produce no smoke or pollutants. In the meantime, they gently cook almost any food to tasty, juicy perfection.

Some solar chefs setout their cookers in the morning and return in the evening to a well-cooked meal. Tiny “backpack” solar cookers have been provided Himalayan mountain climbers with hot food among the snowdrifts – it’s the amount of sunshine that counts, not the outside temperature.

To some people in developing nations, Solar cookers have become important to their very survival. Solar energy cooks food where firewood is scarce, and purifies water where bacteria and dangerous diseases are rampant. Solar cookers are used in Bolivia, Guatemala, South Africa, West Africa, Haiti, the Dominican Republic and many other developing countries. 

In Arizona’s abundant sunshine, solar cookers cook meals year-round without heating up the kitchen or the cook.


Next Article: All About Solar Cookers 2 - How Solar Cookers Work