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A Heat Retention Solar Oven uses energy from the sun to do heat-retention cooking. This type of solar oven is capable of cooking anytime, day or night.

The HR Solar Oven uses the principles of heat retention cooking. A traditional New England Clambake is an example of heat retention cooking. In order to cook clams, lobster, etc. at the beach, you dig a pit in the sand and line the bottom with rocks. You then build a fire in the pit, over the rocks, and let the fire die down. The rocks retain a considerable amount of heat from the fire. You then cover the rocks with wet seaweed, then chickenwire, then layer the food on top of the wire (clams, lobster, potatoes, corn). The final layer consists of more wet seaweed covered by a layer of canvas. The heat from the rocks produces steam (from the seaweed) which cooks the food.

Heat retention cooking involves using stored heat (the hot rocks) to slow cook food in an insulated container (the pit covered with seaweed). The Heat Retention Solar Oven uses the sun's energy to heat a material that retains heat well; this stored heat can then be used to cook anytime, day or night. However, unlike typical heat retention cooking, the HR Solar Oven can cook at oven temperatures ranging from 300 to 400 degrees Fahrenheit. This temperature range is higher than most solar ovens, which are usually only capable of slow cooking at low to moderate temperatures.

A typical solar oven consists of an insulated box with a transparent window on top. Inside the box is a black metal surface or container. The sunlight enters the box and is turned into heat when it strikes the black metal surface. The metal releases the heat to the air inside the box and to the food. As the interior heats up, the temperature of the metal increases. When the sunlight strikes the heated metal, it raises its temperature even higher. This in turn raises the temperature of the whole interior of the oven, including the food.

Unfortunately, most solar ovens are poorly insulated. The heat loss from any insulated container depends in large part on the temperature difference between the interior and exterior of the container. As the typical solar oven heats up, it loses more and more energy, until just as much energy is lost through poor insulation as is gained through sunlight. The top of the solar oven must be transparent, but it is hard to combine transparency with insulation. And heat rises to the top of the oven, exactly where you would want to have more insulation, not less. This limits the maximum cooking temperature of the typical solar oven.

Another limitation to the cooking temperature of most solar ovens is the length of time that energy from the sun can be used to heat the oven. Once the late afternoon is reached, even though there are hours of daylight left, there is not enough energy to cook effectively in a solar oven. You cannot begin cooking with a typical solar oven in the late afternoon or early evening, when many people begin cooking their evening meal. You cannot cook breakfast in the early morning with a solar oven. You are limited to cooking lunch or cooking dinner early. And the cooking temperature of some solar ovens is fairly low, in the range of 250 to 300 degrees F.

If is is rainy or very cloudy, you cannot cook using a solar oven even during the middle of the day. There is not enough energy from the sun on cloudy days to cook using a typical solar oven. And solar ovens generally cannot cook at night when there is even less light.

Many solar oven designs are very successful, in locations near the equator, where the average daily solar radiation is well above 5,000 Watt-hours per square meter per day. Such locations have plenty of sunlight for solar cooking year round, because the sun is not low in the sky during winter. But such a solar oven is used at a higher latitude, (e.g. 40 degrees North), especially in winter, they do not work as well, if they work at all.

A Heat Retention Solar Oven solves the problems of other solar ovens:  low cooking temperature, slow cooking, limited cooking hours, and the inability to cook at night or during cloudy or rainy days. Properly designed, it should work at almost any latitude, all or most of the year.

A Heat Retention Solar Oven cooks at normal oven temperatures (300 - 400 F) and can cook as quickly as a typical electric or gas oven at those temperatures. A Heat Retention Solar Oven can cook anytime, day or night, even during days when it is cloudy or rainy. Furthermore, this type of Solar Oven, once it goes through an initial warm-up period, requires no preheating time since it maintains its temperature range (300 - 400 F) 24 hours a day, seven days a week.

How Does It Work? Read On....

Disclaimer: The drawings, procedures, and words on this site are for information purposes only. No claims are expressed or implied as to the safety, usefulness, or accuracy of this information. This site does not contain recommendations or actual plans for building a Heat Retention Solar Oven. This particular solar oven design is theoretical and experimental.

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