Solar Cookers, Including Parabolic Mirror Solar Stove Oven
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Greetings, my friends and readers,
As long as we’re on the subject of cooking, let’s take a look at some other possible cook wares and what Wikipedia has to say about solar cookers, below:
Using solar cookers
Solar oven in use
The different kinds of solar cookers have somewhat different methods for use, but most follow the same basic principles.
Food is prepared as it would be for an oven or stove top. Because food cooks faster when it is in smaller pieces, solar cookers usually cut the food into smaller pieces than they might otherwise. For example, potatoes are usually cut into bite-sized pieces rather than being roasted whole. For very simple cooking, such as melting butter or cheese, a lid may not be needed and the food may be placed on an uncovered tray or in a bowl. If several foods are to be cooked separately, then they are placed in different containers.
The container of food is placed inside the solar cooker, perhaps elevated on a brick, rocks, metal trivet, or other heat sink, and the solar cooker is placed in direct sunlight. If the solar cooker is entirely in direct sunlight, then the shadow of the solar cooker will not overlap with the shadow of any nearby object. Foods that cook quickly may be added to the solar cooker later. Rice for a mid-day meal might be started early in the morning, with vegetables, cheese, or meat added to the solar cooker in the middle of the morning. Depending on the size of the solar cooker and the number and quantity of cooked foods, a family may use one or more solar cookers.
The solar cooker is turned towards the sun and left until the food is cooked. Unlike cooking on a stove or over a fire, which may require more than an hour of constant supervision, food in a solar cooker is generally not stirred or turned over, both because it is unnecessary and because opening the solar cooker allows the trapped heat to escape and thereby slows the cooking process. If wanted, the solar cooker may be checked every one to two hours, to turn the cooker to face the sun more precisely and to ensure that shadows from nearby buildings or plants have not blocked the sunlight. If the food will be left untended for many hours during the day, then the solar cooker is often turned to face the point where the sun will be when it is higher in the sky, instead of towards its current position.
The cooking time depends primarily on the equipment being used, the amount of sunlight at the time, and the quantity of food that needs to be cooked. Air temperature, wind, and latitude also affect performance. Food cooks faster in the two hours before and after the local solar noon than it does in either the early morning or the late afternoon. Larger quantities of food, and food in larger pieces, take longer to cook. As a result, only general figures can be given for cooking time. With a small solar panel cooker, it might be possible to melt butter in 15 minutes, to bake cookies in 2 hours, and to cook rice for four people in 4 hours. However, depending on the local conditions and the solar cooker type, these projects could take half as long, or twice as long.
A low-cost thermometer has been invented to provide a reliable method for determining when the cooker has reached the temperature for pasteurization of water or milk (65 deg. C or 149 deg. F). This device is called the Water Pasteurization Indicator or WAPI.
It is difficult to burn food in a solar cooker. Food that has been cooked even an hour longer than necessary is usually indistinguishable from minimally cooked food. The exception to this rule is some green vegetables, which quickly change from a perfectly cooked bright green to olive drab, while still retaining the desirable texture.
For most foods, such as rice, the typical person would be unable to tell how it was cooked from looking at the final product. There are some differences, however: Bread and cakes brown on their tops instead of on bottom. Compared to cooking over a fire, the food does not have a smoky flavor.
Advantages
Solar cookers use no fuel, which means that their users do not need to fetch or pay for firewood, gas, electricity, or other fuels. Therefore, over time a solar cooker can pay for itself in reduced fuel costs. Since it reduces firewood use, the solar cooker reduces deforestation and habitat loss. Since there are about 2 billion people who are still cooking on open fires, widespread use of solar cookers could have large economic and environmental benefits.
Solar box cookers attain temperatures of up to about 165 deg. C (325 deg. F), so they can be used to sterilize water or prepare most foods that can be made in a conventional oven or stove, from baked bread to steamed vegetables to roasted meat. When solar ovens are placed outside, they do not contribute unwanted heat inside houses.
Solar cookers do not produce any smoke as a product of combustion. The indoor concentration of health-damaging pollutants from a typical wood-fired cooking stove creates carbon monoxide and other noxious fumes at anywhere between seven and 500 times over the allowable limits. Fire-based cooking also produces ashes and soot, which make the home dirtier. However, any type of cooking, including solar cooking, can evaporate grease, oil, etc., from the food into the air.
Unlike cooking over an open fire, children cannot be burned by touching many types of solar cookers, which are made from cardboard or plastic and do not get hot. Unlike all fuel-based cooking arrangements, these solar cookers are not fire hazards. However, solar cookers that concentrate sunlight, e.g. with paraboloidal reflectors (our chef Dan Rojas in the video clip below believes that it is easier, slower, and allows cover, to cook with a parabolic solar cooker than with the Fresnel lens as in previous post), do produce high temperatures which could cause injury or fire.
Disadvantages
Solar cookers are less usable in cloudy weather and at high latitudes, so some fuel-based backup heat source must still be available in these conditions. Also, solar cooking provides hot food during or shortly after the hottest part of the day, rather than the evening when most people like to eat. The “integrated solar cooking” concept accepts these limitations, and includes a fuel-efficient stove and an insulated heat storage container to provide a complete solution.
Many solar cookers take longer time to cook food than a fuel-based oven. Using these solar cookers therefore requires that food preparation be started several hours before the meal. However, it requires less hands-on time cooking, so this is often considered a reasonable trade-off.
Cooks may need to learn special cooking techniques to fry common foods, such as fried eggs or flat breads like chapatis and tortillas. It may not be possible to safely or completely cook some thick foods, such as large roasts, loaves of bread, or pots of soup, particularly in small panel cookers; the cook may need to divide these into smaller portions before cooking.
Some solar cooker designs are affected by strong winds, which can slow the cooking process, cool the food, and disturb the reflector. In these cases it is necessary to anchor the reflector with string and weights.
posted by sunisthefuture-Susan Sun Nunamaker, sunisthefuture@gmail.com
Homepage: http://www.sunisthefuture.net
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Tags: clean energy, energy, parabolic mirror solar stove oven, renewable energy, solar, solar cooker, Sun, Sun Is The Future, sunisthefuture, sunisthefuture.com, susan sun nunamaker, www.sunisthefuture.net
February 13th, 2012 at 4:44 AM
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