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All About Solar Cookers 5

Solar cooking tips

Safety:

· Solar cookers may not look hot, but temperatures of 120 to 425 degrees will certainly burn your fingers. Use potholders.

· Intense reflected light could permanently damage your eyes. Children in particular have a tendency to stand in the brightness of reflected light and should be carefully watched around solar cookers.

· Keep the lid closed so that appetizing fumes, do not escape into the air and attract animals and insects. If a curious animal does approach the cooker, a closed lid prevents unwanted dinner guests. 

Foods:

Solar chefs are limited only by their imagination. Almost any dish becomes a delicious treat when cooked in a solar cooker –beans, bread, cookies, roasts, vegetables and many others. 
Most standard recipes translate favorably to solar cookers but require less water or liquid. Solar chefs also find they need less salt and sugar in solar-cooked foods because of the gentle cooking process.

Temperature and Timing:

Solar cookers should be placed in the sun and preheated for at least one hour before placing food inside. Many, high-quality solar cookers reach temperatures of 350 to 425 degrees or more and cook dinner in the same amount of time as conventional ovens. Other models reach temperatures of only 150 degrees. A barbecue thermometer is a useful tool. 

To reach maximum temperature and fastest cooking time, the cooker should be aimed directly at the sun. It should be turned every 20-30 minutes to maintain a direct angle. Some solar chefs setout cookers in the morning, aiming them toward the sun’s midday position. By late afternoon, dinner is ready to eat without ever refocusing the cooker.  

Cooking between the hours of 10 a.m. to 2 p.m. is best in Arizona’s winter months. In summer, the sky’s the limit!

Weather:

Clear weather is essential. On partially cloudy days, solar cooking takes longer. On extremely cloudy days, we suggest that you rely on the old energy-consumer standbys like house ovens or barbecues.

Outside temperature has little effect on solar cooking; if the sky is clear, you can cook on a snowbank high in the mountains.

Pots and other utensils:

Use either dark, or clear glass pots when cooking in solar cookers. Dark pots absorb light readily and clear glass allows light to directly reach the food. Avoid foil or aluminum containers that reflect light away.

Closed containers hold-in heat and will cook food more quickly. Some people even use canning jars. Brown-in bags are excellent for cooking meat.

Cooking times: (NOTE: 450g = 1 lb)

Potatoes (300g + 1 spoonful water) 2 hours
Carrots (250g + 1 onion, no water) 2 hours
2 eggs (+ 1 spoonful water) 1 hour
Lentils (100g + 250g water) 1.5 hours
White rice (80g + 160g water) 1.25 hours
Brown rice (80g + 160g water) 2 hours
Red beans (100g + 200g water) 2.5 hours

Next Article: All About Solar Cookers 6 - Overcoming fuel shortages in developing nations 

All About Solar Cookers 4

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.

Next Article: All About Solar Cookers 5 - Solar cooking tips

All About Solar Cookers 3

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.

Next Article: All About Solar Cookers 4 - Design of Solar Cookers

All About Solar Cookers 2

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.

Next Article: All About Solar Cookers 3 - Costs: Cooking while reducing summer cooling bills