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Solar Cooker Essay

A solar cooker is a device which uses the energy of direct sunlight to heat, cook or pasteurise drink. Many solar cookers currently in use are relatively inexpensive, low-tech devices, although some are as powerful or as expensive as traditional stoves,[1] and advanced, large-scale solar cookers can cook for hundreds of people.[2] Because they use no fuel and cost nothing to operate, many nonprofit organizations are promoting their use worldwide in order to help reduce fuel costs (especially where monetary reciprocity is low) and air pollution, and to slow down the deforestation and desertification caused by gathering firewood for cooking.

Principles[edit]

1) Concentrating sunlight: A mirrored surface with high specular reflectivity is used to concentrate light from the sun on to a small cooking area. Depending on the geometry of the surface, sunlight can be concentrated by several orders of magnitude producing temperatures high enough to melt salt and smelt metal. For most household solar cooking applications, such high temperatures are not really required. Solar cooking products, thus, are typically designed to achieve temperatures of 150 °F (65 °C) (baking temperatures) to 750 °F (400 °C) (grilling/searing temperatures) on a sunny day.

2) Converting light energy to heat energy: Solar cookers concentrate sunlight onto a receiver such as a cooking pan. The interaction between the light energy and the receiver material converts light to heat. This conversion is maximized by using materials that conduct and retain heat. Pots and pans used on solar cookers should be matte black in color to maximize the absorption.

3) Trapping heat energy: It is important to reduce convection by isolating the air inside the cooker from the air outside the cooker. Simply using a glass lid on your pot enhances light absorption from the top of the pan and provides a greenhouse effect that improves heat retention and minimizes convection loss. This "glazing" transmits incoming visible sunlight but is opaque to escaping infrared thermal radiation. In resource constrained settings, a high-temperature plastic bag can serve a similar function, trapping air inside and making it possible to reach temperatures on cold and windy days similar to those possible on hot days.

Operation[edit]

Different kinds of solar cookers use somewhat different methods of cooking, but most follow the same basic principles.

Food is prepared as if for an oven or stove top. However, because food cooks faster when it is in smaller pieces, food placed inside a solar cooker is usually cut into smaller pieces than it might otherwise be.[3] For example, potatoes are usually cut into bite-sized pieces rather than roasted whole.[4] 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, which may be elevated on a brick, rock, metal trivet, or other heat sink, and the solar cooker is placed in direct sunlight.[3] 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 soup 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.

A solar oven 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 oven is generally not stirred or turned over, both because it is unnecessary and because opening the solar oven allows the trapped heat to escape and thereby slows the cooking process. If wanted, the solar oven may be checked every one to two hours, to turn the oven to face the sun more precisely and to ensure that shadows from nearby buildings or plants have not blocked the sunlight. If the food is to be left untended for many hours during the day, then the solar oven is often turned to face the point where the sun will be when it is highest in the sky, instead of towards its current position.[5]

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. Large quantities of food, and food in large 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. With a high performing parabolic solar cooker, you may be able to grill a steak in minutes. However, depending on local conditions and the solar cooker type, these projects could take half as long, or twice as long.

It is difficult to burn food in a solar cooker.[4] 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 the bottom. Compared to cooking over a fire, the food does not have a smoky flavor.

Box and Panel designs[edit]

A box cooker has a transparent glass or plastic top, and it may have additional reflectors to concentrate sunlight into the box. The top can usually be removed to allow dark pots containing food to be placed inside. One or more reflectors of shiny metal or foil-lined material may be positioned to bounce extra light into the interior of the oven chamber. Cooking containers and the inside bottom of the cooker should be dark-colored or black. Inside walls should be reflective to reduce radiative heat loss and bounce the light towards the pots and the dark bottom, which is in contact with the pots. The box should have insulated sides. Thermal insulation for the solar box cooker must be able to withstand temperatures up to 150 °C (300 °F) without melting or out-gassing. Crumpled newspaper, wool, rags, dry grass, sheets of cardboard, etc. can be used to insulate the walls of the cooker. Metal pots and/or bottom trays can be darkened either with flat-black spray paint (one that is non-toxic when warmed), black tempera paint, or soot from a fire. The solar box cooker typically reaches a temperature of 150 °C (300 °F). This is not as hot as a standard oven, but still hot enough to cook food over a somewhat longer period of time.

Panel solar cookers are inexpensive solar cookers that use reflective panels to direct sunlight to a cooking pot that is enclosed in a clear plastic bag.

Solar Oven science experiments are regularly done as projects in high schools and colleges, such as the "Solar Oven Throwdown" at the University of Arizona.[6] These projects prove that it is possible to both achieve high temperatures, as well as predict the high temperatures using mathematical models.

Parabolic reflectors[edit]

Main article: parabolic reflector

Parabolic solar cookers concentrate sunlight to a single point. When this point is focused on the bottom of a pot, it can heat the pot quickly to very high temperatures which can often be comparable with the temperatures achieved in gas and charcoal grills. These types of solar cookers are widely used in several regions of the world, most notably in China and India where hundreds of thousands of families currently use parabolic solar cookers for preparing food and heating water. Some parabolic solar cooker projects in China abate between 1-4 tons of carbon dioxide per year and receive carbon credits through the Clean Development Mechanism (CDM) and Gold Standard.

Some parabolic solar cookers incorporate cutting edge materials and designs which lead to solar energy efficiencies >90%. Others are large enough to feed thousands of people each day, such as the solar bowl at Auroville in India, which makes 2 meals per day for 1,000 people.[7]

If a reflector is axially symmetrical and shaped so its cross-section is a parabola, it has the property of bringing parallel rays of light (such as sunlight) to a point focus. If the axis of symmetry is aimed at the sun, any object that is located at the focus receives highly concentrated sunlight, and therefore becomes very hot. This is the basis for the use of this kind of reflector for solar cooking.

Paraboloidal reflectors[edit]

Paraboloids are compound curves, which are more difficult to make with simple equipment than single curves. Although paraboloidal solar cookers can cook as well as or better than a conventional stove, they are difficult to construct by hand. Frequently, these reflectors are made using many small segments that are all single curves which together approximate compound curves.

Although paraboloids are difficult to make from flat sheets of solid material, they can be made quite simply by rotating open-topped containers which hold liquids. The top surface of a liquid which is being rotated at constant speed around a vertical axis naturally takes the form of a paraboloid. Centrifugal force causes material to move outward from the axis of rotation until a deep enough depression is formed in the surface for the force to be balanced by the levelling effect of gravity. It turns out that the depression is an exact paraboloid. (See Liquid mirror telescope.) If the material solidifies while it is rotating, the paraboloidal shape is maintained after the rotation stops, and can be used to make a reflector.[citation needed] This rotation technique is sometimes used to make paraboloidal mirrors for astronomical telescopes, and has also been used for solar cookers. Devices for constructing such paraboloids are known as rotating furnaces.

Paraboloidal reflectors generate high temperatures and cook quickly, but require frequent adjustment and supervision for safe operation. Several hundred thousand exist, mainly in China.[citation needed] They are especially useful for individual household and large-scale institutional cooking.

A Scheffler cooker (named after its inventor, Wolfgang Scheffler) uses a large ideally paraboloidal reflector which is rotated around an axis that is parallel with the earth's using a mechanical mechanism, turning at 15 degrees per hour to compensate for the earth's rotation. The axis passes through the reflector's centre of mass, allowing the reflector to be turned easily. The cooking vessel is located at the focus which is on the axis of rotation, so the mirror concentrates sunlight onto it all day. The mirror has to be occasionally tilted about a perpendicular axis to compensate for the seasonal variation in the sun's declination. This perpendicular axis does not pass through the cooking vessel. Therefore, if the reflector were a rigid paraboloid, its focus would not remain stationary at the cooking vessel as the reflector tilts. To keep the focus stationary, the reflector's shape has to vary. It remains paraboloidal, but its focal length and other parameters change as it tilts. The Scheffler reflector is therefore flexible, and can be bent to adjust its shape. It is often made up of a large number of small plane sections, such as glass mirrors, joined together by flexible plastic. A framework that supports the reflector includes a mechanism that can be used to tilt it and also bend it appropriately. The mirror is never exactly paraboloidal, but it is always close enough for cooking purposes.[citation needed]

Sometimes the rotating reflector is located outdoors and the reflected sunlight passes through an opening in a wall into an indoor kitchen, often a large communal one, where the cooking is done.[citation needed]

Paraboloidal reflectors that have their centres of mass coincident with their focal points are useful. They can be easily turned to follow the sun's motions in the sky, rotating about any axis that passes through the focus. Two perpendicular axes can be used, intersecting at the focus, to allow the paraboloid to follow both the sun's daily motion and its seasonal one. The cooking pot stays stationary at the focus. If the paraboloidal reflector is axially symmetrical and is made of material of uniform thickness, its centre of mass coincides with its focus if the depth of the reflector, measured along its axis of symmetry from the vertex to the plane of the rim, is 1.8478 times its focal length. The radius of the rim of the reflector is 2.7187 times the focal length. The angular radius of the rim, as seen from the focal point, is 72.68 degrees.[citation needed]

Parabolic troughs[edit]

Parabolic troughs are used to concentrate sunlight for solar-energy purposes. Some solar cookers have been built that use them in the same way.[citation needed] Generally, the trough is aligned with its focal line horizontal and east-west. The food to be cooked is arranged along this line. The trough is pointed so its axis of symmetry aims at the sun at noon. This requires the trough to be tilted up and down as the seasons progress. At the equinoxes, no movement of the trough is needed during the day to track the sun.[9] At other times of year, there is a period of several hours around noon each day when no tracking is needed. Usually, the cooker is used only during this period, so no automatic sun tracking is incorporated into it. This simplicity makes the design attractive, compared with using a paraboloid. Also, being a single curve, the trough reflector is simpler to construct. However, it suffers from lower efficiency.

It is possible to use two parabolic troughs, curved in perpendicular directions, to bring sunlight to a point focus as does a paraboloidal reflector.[citation needed]The incoming light strikes one of the troughs, which sends it toward a line focus. The second trough intercepts the converging light and focuses it to a point.[citation needed]

Compared with a single paraboloid, using two partial troughs has important advantages. Each trough is a single curve, which can be made simply by bending a flat sheet of metal. Also, the light that reaches the targeted cooking pot is directed approximately downward, which reduces the danger of damage to the eyes of anyone nearby. On the other hand, there are disadvantages. More mirror material is needed, increasing the cost, and the light is reflected by two surfaces instead of one, which inevitably increases the amount that is lost.

The two troughs are held in a fixed orientation relative to each other by being both fixed to a frame.[citation needed] The whole assembly of frame and troughs has to be moved to track the sun as it moves in the sky. Commercially made cookers that use this method are available.In practical applications (like in car-headlights), concave mirrors are of parabolic shape

Spherical reflectors[edit]

Spherical reflectors operate much like paraboloidal reflectors, such that the axis of symmetry is pointed towards the sun so that light is concentrated to a focus. However, the focus of a spherical reflector will not be a point focus because it suffers from a phenomenon known as spherical aberration. Some concentrating dishes (such as satellite dishes) that do not require a precise focus opt for a spherical curvature over a paraboloid. If the radius of the rim of spherical reflector is small compared with the radius of curvature of its surface (the radius of the sphere of which the reflector is a part), the reflector approximates a paraboloidal one with focal length equal to half of the radius of curvature.[10]

Vacuum Tube Technology[edit]

Evacuated tube solar cookers are essentially a vacuum sealed between two layers of glass. The vacuum allows the tube to act both as a "super" greenhouse and an insulator. The central cooking tube is made from borosilicate glass, which is resistant to thermal shock, and has a vacuum beneath the surface to insulate the interior. The inside of the tube is lined with copper, stainless steel, and aluminum nitrile to better absorb and conduct heat from the sun's rays. Some vacuum tube solar cookers incorporate lightweight designs which allow great portability (such as the GoSun stove) [11] Portable vacuum tube cookers such as the GoSun allow users to cook freshly caught fish on the beach without needing to light a fire.[12]

Advantages and disadvantages[edit]

Advantages

  • High-performance parabolic solar cookers can attain temperatures above 290 °C (550 °F). They can be used to grill meats, stir-fry vegetables, make soup, bake bread, and boil water in minutes.
  • Conventional solar box cookers attain temperatures up to 165 °C (325 °F). They can sterilize water or prepare most foods that can be made in a conventional oven or stove, including bread, vegetables and meat over a period of hours.
  • Solar cookers use no fuel. This saves cost as well as reducing environmental damage caused by fuel use. Since 2.5 billion people cook on open fires using biomass fuels, solar cookers could have large economic and environmental benefits by reducing deforestation.[13]
  • When solar cookers are used outside, they do not contribute inside heat, potentially saving fuel costs for cooling as well. Any type of cooking may evaporate grease, oil, and other material into the air, hence there may be less cleanup.

Disadvantages

  • Solar cookers are less useful in cloudy weather and near the poles (where the sun is low in the sky or below the horizon), so an alternative cooking source is still required in these conditions. Solar cooking advocates suggest three devices for an integrated cooking solution: a) a solar cooker; b) a fuel-efficient cookstove; c) an insulated storage container such as a basket filled with straw to store heated food. Very hot food may continue to cook for hours in a well-insulated container. With this three-part solution, fuel use is minimized while still providing hot meals at any hour, reliably.
  • Some solar cookers, especially solar ovens, take longer to cook food than a conventional stove or oven. Using solar cookers may require food preparation start hours before the meal. However, it requires less hands-on time during the 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 flatbreads 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 due to convective losses, and disturb the reflector. It may be necessary to anchor the reflector, such as with string and weighted objects like bricks.

Projects[edit]

Cardboard, aluminium foil, and plastic bags for well over 10,000 solar cookers have been donated to the Iridimi refugee camp and Touloum refugee camps in Chad by the combined efforts of the Jewish World Watch, the Dutch foundation KoZon, and Solar Cookers International. The refugees construct the cookers themselves, using the donated supplies and locally purchased Arabic gum.[14] It has also significantly reduced the amount of time women spend tending open fires each day, with the results that they are healthier and they have more time to grow vegetables for their families and make handicrafts for export.[14] By 2007, the Jewish World Watch had trained 4,500 women and had provided 10,000 solar cookers to refugees. The project has also reduced the number of foraging trips by as much as 70 percent, thus reducing the number of attacks.[citation needed]

Some Gazans have started to make solar cookers made from cement bricks and mud mixed with straw and two sheets of glass. About 40 to 45 Palestinian households reportedly have started using these solar cookers.[15], including some made with mirrors.

Bysanivaripalle, a silk-producing village that is 125 km (78 mi) northwest of Tirupati in the Indian state of in Andhra Pradesh, is the first of its kind: an entire village that uses only solar cooking.

Thousands of parabolic solar cookers produced by One Earth Designs are used on the Himalayan Plateau in China to reduce dependence on biomass fuel like wood and yak dung.[16]

See also[edit]

References[edit]

  1. ^"Solar Cookers: Varieties and Styles". CantinaWest. Retrieved 4 June 2014. 
  2. ^"World's Largest 38500-meal Solar Kitchen in India". inhabitat. Retrieved 4 June 2014. 
  3. ^ abLinda Frederick Yaffe (2007). Solar Cooking for Home and Camp. Mechanicsburg, PA: Stackpole Books. pp. 16–20. ISBN 0-8117-3402-1. 
  4. ^ abHalacy, D. S.; Halacy, Beth (1992). Cooking with the sun. La Fayette, CA: Morning Sun Press. pp. 46–47. ISBN 0-9629069-2-1. 
  5. ^Halacy, D. S.; Halacy, Beth (1992). Cooking with the sun. La Fayette, CA: Morning Sun Press. p. 89. ISBN 0-9629069-2-1. 
  6. ^"Solar Oven Throwdown Heats Up UA Mall". UANews. Retrieved 2016-03-18. 
  7. ^"The solar bowl". archive.org. 22 December 2014. Archived from the original on 22 December 2014. 
  8. ^Solar cooker pictures Solar Cooking Atlas official website
  9. ^Prinsloo, GJ & Dobson, RT (572). "Solar Tracking (eBook)": 1. doi:10.13140/RG.2.1.4265.6329/1. ISBN 978-0-620-61576-1. 
  10. ^See Parabola#Focal length and radius of curvature at the vertex
  11. ^Fincher, Johnathan. "GoSun:Portable solar oven cooks food in as little as 10 minutes". Retrieved September 16, 2013. 
  12. ^Twmffat, Tecwyn. "Solar cooked mackerel on the rocks". Retrieved September 26, 2016. 
  13. ^"WHO: Household Air Pollution and Health". World Health Organization. Retrieved 15 May 2014. 
  14. ^ ab"Solar lifeline saves Darfur women". CNN. 2007-09-17. Retrieved 2008-03-06. 
  15. ^"Electricity has Become Less Available or Affordable for Many". Retrieved 25 November 2017. 
  16. ^"Cooking up innovation". MITnews. 2013-06-24. Retrieved 2014-05-09. 

External links[edit]

Hot dogs being cooked with a solar funnel cooker
HotPot panel solar cooker
A Solar Oven made of cardboard, newspapers, and reflective tape
Solar tea kettle in Tibet
A parabolic solar cooker with segmented construction .[8]
A Scheffler cooker. This reflector has an area of 16 m2 (170 sq ft), and concentrates 3 kW of heat
Students perform an experiment using a solar cooker built out of an umbrella

Solar Cookers

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Solar Cookers

Jewish families celebrate Passover to commemorate the freedom and exodus of the Israelites (Jewish slaves) from Egypt during the reign of the Pharaoh Ramses II. When the Pharaoh Ramses II freed the Israelites, they fled so quickly that there wasn't time to bake their breads. Instead the Israelites packed the raw dough, which they quickly baked in the hot sun into hard crackers called Matzohs as they fled through the desert. The exodus of the Israelites took place over 3000 years ago, but the Israelites were not the first to harness solar power for cooking, neither were they the last. Solar cooking has had a long rich history and has important implication for the future. Solar cooking is an important link in understanding the sun’s power, is a sink of innovation and technology, is widely applicable around the world, has social, economic and ecological benefits, and is the answer to some of the world’s biggest natural resource shortages. Although, solar cooking is an industry that has yet to be revolutionized into an efficient home appliance, therefore, there are many avenues for innovation and technological advancement to be explored.

Horace de Saussure coincidently created the first solar box cooker, although, because cooking food was not his objective he failed to revolutionize the solar cooking as an efficient home appliance. Horace de Saussure, “set out to determine how effectively glass heat traps could collect the energy of the sun.” Horace de Saussure placed five consecutively smaller open bottomed glass boxes within each other on a black table, in which he placed a piece of fruit. When this miniature five walled green house was exposed to the sun, each consecutive glass chamber trapped warm air and thermal radiation, which are by products of light energy being turned into heat. Consequently the innermost glass box became the hottest, a recorded 189.5 degrees Fahrenheit and Horace de Saussure successfully cooked fruit within this box. Cooking was only an experiment used by Horace de Saussure to understand his greater goal, which was how effectively glass heat traps could collect the energy of the sun. Although, Horace de Saussure realized the practical application of his heat trap. Horace de Saussure stated, “someday some usefulness might be drawn from this device . . . [for it] is actually quite small, inexpensive, [and] easy to make.” Horace de Saussure was correct in stating that solar cooking is useful, but contrary to his advice the solar cooker failed to be revolutionized into an efficient home appliance.

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In 1976 Barbara Kerr and Sherry Cole developed the simple cardboard solar box cooker, which ultimately led to the creation of Solar Cookers International, one hundred years after the end of the industrial revolution. Although, examples of active and passive solar systems like Kerr and Cole’s, were present at conventions known as “World’s Fairs” during the Guilded Age and Progressive Era, these designs have only begun to be revolutionized in the mid 20th century. Kerr and Cole set out to create solar box cookers to emphasize simplicity in design and construction, to use appropriate and available materials, to be dependable under a wide variety of conditions, and to utilize recycled materials and minimal costs. Although, they understand why the solar cooker did not benefit from the industrial revolution, according to Kerr and Cole,
Engineering approaches and available literature often emphasize maximum solar collection at the expense of simplicity, functionality, appropriate materials and ease of use. Such designs do not lend themselves to being used as routine home appliances, nor can they be built without special tools and skills.

According to Kerr and Cole, solar cookers have not been revolutionized because engineers have ruled out the possibility of solar cooking being utilized as an efficient home appliance.

The contemporaneousness of Kerr and Cole’s invention tells us that the revolution of the solar cooker is only just beginning, that there are many technological innovations to be explored before solar cooking can be ruled out as an efficient home appliance. Currently there are three types of solar cookers that are being used today, the box cooker, the panel cooker and the parabolic cooker. As Horace de Saussure documented, a solar box cooker works because the sunlight entering the solar box through the glass or plastic top is transformed into heat energy when it is absorbed by the dark absorber plate and cooking pots. This heat input causes the temperature inside of the solar box cooker to rise until the heat loss of the cooker is equal to the solar heat gain. Temperatures sufficient for cooking food and pasteurizing water are easily achieved. Roger Bernard developed the panel cooker, which reflects light into a glass jar containing a cooking pot. Unlike the box cooker the solar panel cooker does not trap as much thermal radiation or heat energy, although, the direct heat from the sun is more intensely focused on the cooking pot. The solar panel cooker is a middle ground between the solar box cooker and the parabolic cooker. Parabolic cookers are large concave discs that reflect and focus large amounts of light directly onto the bottom of a cooking pot, but they must be in direct sunlight.

Modern engineers understand why solar cookers work and some of their limitations, but there remains room for innovating an efficient home appliance. Solar cookers utilize three basic natural laws: (1) when solar radiation (sunlight) strikes a dark surface it changes to infrared radiation (heat), (2) when light falls on light-colored or shiny surfaces it reflects and so can be directed to where it is needed. (3) Solar radiation (sunlight) passes through a transparent window easily, but infrared radiation (heat) does not, so heat can be trapped. Using these three natural laws solar cookers can maintain temperatures between 250 and 300 degrees Fahrenheit. Food cooks at a mere 190 degrees Fahrenheit and water boils at 212 degrees Fahrenheit, therefore, solar cookers are capable of producing the same effects of much less efficient, but more popular home appliances such as ovens and stoves. As we approach the next millennium, such resources as coal, oil and gas, which is formed from solar grown organic matter and are not renewable, will be consumed in a tiny fraction of the millions of years required for their formation leading to resource depletion. Although, solar cookers will always remain a diffuse resource that will outlast all the fuel resources we now rely on. Therefore, much more innovative and technological energy must be put into solar cooking to make it more efficient as a home appliance.

Advocates of solar cooking argue that solar cookers are efficient home appliances and therefore deserve technological revolutionization. These advocates believe the efficiency of the solar cookers is tied to their economic, social and ecological benefits. Although the economic impact of solar cookers varies between regions, solar cookers save wood and are an alternative to cooking fuel shortages. Socially families benefit from solar cooking because they can leave food in the solar cooker for an infinite amount of time in order to do more economically productive activities, such as working farming or housework. Solar cookers also allowing families to reduce the amount of time and energy spent collecting or working for fuel and also encourages health by pasteurizing water making it more sanitary for consumption and cleansing. And furthermore, solar cookers have an ecologically beneficial impact by allowing more trees to grow and straw that might have been cooking fuel to become fertilizer.

Why has solar cooking not been revolutionized? Historically, solar cooking advocates think of solar cooking as a simple, low-tech, inexpensive cooking strategy. These advocates support this stance by stating that,

Millions of poor people around the world, however, still cook over a smoky fire everyday. To find wood for the fire, they have to walk many hours everyday. Other poor city dwellers don't have access to wood, so they have to spend up to half of their income on cooking fuel. These people could never afford an oven made of high-tech materials.

Contrarily, solar cooking needs to become more high-tech and revolutionized, in order to replace conventional cooking appliances. This is important because in some places simple, low-tech, inexpensive solar cookers may help to offset the expense of fuelwood collection and cooking fuel costs, but it does little to cut down on the use of non-renewable resources in developed countries, like the United States. The United States consumes the majority of the world cooking fuel and therefore produces a majority of the pollution. But if solar cookers were revolutionized into high-tech efficient cookers able to compete with contemporary oven and stoves, that would make a huge difference in the United States’ overall consumption of natural resources.