Introduction to solar cooking

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Below you will find an introduction to solar cooking. The Solar Cooking Wiki also provides an individual page for different countries where you will find news, NGOs, manufacturers, and individuals working on solar cooking projects in that country. Links to possible funders are also available:
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Depending on where you live and how you cook, solar cooking can save you time, effort, and fuel. It is also an environmentally friendly and fun way to prepare your meals. All foods can be cooked in some type of solar cooker. 
Cooking with a solar box cooker or solar panel cooker is similar to using a slow cooker (crock-pot). Typically, cooking times for these types of cookers are twice that of conventional cooking methods, however, slower cooking also has its advantages. These cookers provide a moderate, even heat, are only reoriented once towards the sun over several hours of cooking, and the food does not have to be stirred during cooking. This frees the cook up to do other useful tasks while the food cooks independently. Also, a solar cooking recipe usually calls for less added liquid. More of the natural flavors and liquids are retained and not boiled away.
Parabolic solar cookers offer another approach to solar cooking by being able to reach higher temperatures and perform more like a traditional stovetop. As such, they require more attention while cooking to avoid burning the food and they need to be turned periodically to follow the sun, depending on cooking time. 
For areas in the world experiencing deforestation and limited access to clean water, solar cooking is a valuable part of the solution, by providing a safe, smoke-free alternative method of cooking and pasteurizing water. 
==Buy or build a solar cooker?==
 
If you are interested in trying solar cooking for the first time, you may be wondering whether you should build your own solar cooker, or to buy one from a manufacturer. There are advantages to both options:
#Building your own solar cooker can be a fun and cost-effective way to get started.
#A wide variety of solar cookers are available for purchase, and you will often receive a higher-quality cooker than one you might build yourself.
If you would like to build a cooker, visit the build a solar cooker page to choose a design that's right for you. You will find information there comparing the characteristics of each style of cooker. 
If you would like to purchase a cooker, check out the list of manufacturers and vendors on the buy a solar cooker page. Commercial cookers are typically durable and efficient, and offer an easy way for new users to experience solar cooking. As cookers are manufactured globally, consider potential shipping costs when selecting a design.
==How do solar cookers work?==
Solar cookers work on this basic principle: Sunlight reaches a dork colored cooking pot, causing the pot to create heat energy, that is retained with for cooking. 
Many solar panel cookers and solar box cookers are capable of reaching , or higher. The captured solar radiation passes through a greenhouse enclosure enclosing a dark colored cook pot. As it hits the dark surface, the solar radiation is converted to heat, which is contained within the glazing enclosure, and cooking temperatures are achieved. The same principle is often experienced by drivers returning to a hot car that has been parked in the sun. 
Visible light, near-infrared, and a small amount of UV radiation causes a molecular reaction within the dark pot surface to create heat. This energy is reradiated as longer wavelength infrared light. These longer wavelengths have difficulty passing back through glass or other greenhouse materials, and are relfected back at the cook pot and other black surfaces within the cooking chamber. The efficiency of these cookers is typically determined by the amount of reflector area available of the solar cooker to gather sunlight, and the ability of the greenhouse enclosure to receive the available light and help insulate the hot cook pot. Solar box cookers also have insulated walls, some more than others, helping retain heat. Double Pyrex bowls have been shown to work well as greenhouse enclosures for solar panel cookers. See: Glazing for additional enclosure ideas.
	
		
		
Sunlight is the fuel. A solar cooker needs an outdoor spot that is sunny for several hours and protected from strong wind, and where food will be safe. Solar cookers don't work at night or on cloudy days. 
	
Dark surfaces get very hot in sunlight, whereas light surfaces don't. Cooking is typically best done with dark, shallow, thin metal pots with dark lids to hold in heat and moisture. The thin metal cook pots heat up quickly, but thicker pots will retain heat longer and should be preheated before adding the food.
A transparent heat trap around the dark pot lets in sunlight, but keeps in the heat. This is a clear, heat-resistant plastic bag or large inverted glass bowl (panel cookers) or an insulated box with a glass or plastic window (box cookers).
One or more shiny surfaces reflect extra sunlight onto the pot, increasing its cooking potential.
*Parabolic solar cookers use a bowl shaped reflector to focus the light directly onto the cook pot, usually from below. Typically they do not require a greenhouse enclosure to retain the heat. They reach much higher temperatures than the other styles of solar cookers, usually above , and also have the ability to fry and broil foods.
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==Solar cooker types==
The three most common types of solar thermal cookers are box cookers, panel cookers, and parabolic cookers. Hundreds — if not thousands — of variations on these basic types exist. Evacuated tube cookers and trough cookers are two lesser known styles of cooker design. The two approaches are often combined, as the geometry of each is suited to the other. Additionally, several large scale solar cooking systems have been developed to meet the needs of cooking for lerge numbers of people.
===Box cookers===
===Panel cookers===
Panel cookers incorporate elements of box and parabolic cookers. They often have a large reflector area and the cook pot has some form of clear enclosure to retain heat. Panel cookers are capable of cooking at approximately . They are the easiest style to make and relatively inexpensive to buy. 
===Parabolic cookers===
 Parabolic solar cookers use a bowl shaped reflector to focus the light directly onto the cook pot, usually from below, and typically do not require a greenhouse enclosure to retain the heat. The parabolic name refers to the shape of the curve of the reflector cross-section. 
They require more frequent reorientation to the sun, possibly every fifteen minutes, but they cook food more quickly at higher temperatures compared to other solar cookers, often reaching temperatures over . They also have the ability to fry and broil foods. Generally parabolic solar cookers will need to be attended to more than box or panel cookers to avoid possibly burning the food at the bottom of the cook pot. They are especially useful for large-scale institutional solar cooking systems.
===Trough cookers===
For capturing sunlight, trough solar cookers use a reflector with a curved parabolic cross-section, that continues as a straight trough in the other direction. Instead of focusing the light at one spot like a typical bowl-shaped parabolic solar cooker, the light is reflected along what is known as a focal line. These reflectors are easier to fabricate than a parabolic dish, but require a long fairly narrow cooking tray, which is why they work well with evacuated tube enclosures.
===Evacuated tube cookers===
Evacuated tube literally means that the cooking chamber is constructed of two layers of blown glass in the shape of a sealed tube, where the air has been removed between the layers. 
Heat loss often happens by conduction through a medium or by and convection through the air. With no air between the layers of glass, the chamber is nicely insulated, and well suited for retaining cooking heat. The chamber is so effective at insulating it often does not require a large reflector to capture sunlight. A slender cooking tray can be inserted from one end. The opposite end is either sealed with a stopper, or has been sealed during the manufacturing process. Improvements in glass technology is allowing for larger diameter tubes to be fabricated, which will allow larger cooking trays to be inserted inside.
===Other types===
*Fresnel solar cooker designs
*Solar wall oven designs
*In-the-ground solar cooker designs
*Photovoltaic cooker designs
*Hybrid solar cooker designs 
*Institutional solar cooker designs
==Beyond performance ratings==
Various methods of testing are available to evaluate the performance of solar cookers. Solar Cookers International responded to requests from cooks, manufacturers, and organizations to create an objective, scientific process to evaluate the cooking potential of different cookers, and developed the Performance Evaluation Process (PEP). A number of solar cookers have been tested with this method, and can be seen at PEP tested solar cookers.
Beyond cooking performance, other factors should be considered when designing, purchasing, or building a solar cooker.
*Cost: The cost of all supplies needed for the solar cooker - including estimated replacement parts needed within five years, compared to the cost of alternative cooking methods and the fuel used in them over five years. Also to consider: Environmental benefits of solar cooking
*Convenience: The cooker either needs little or no attention during cooking or, the instructions address how often adjustments are needed during a cooking period (for example with parabolic cookers, frequent turning to track the sun or stirring to prevent burning). If movable, is the cooker easy to move and easy to store? What is required to check on the cooking food, and remove it from the cooker when done?
*Safety: The cooker should be incapable of starting an accidental fire inside or outside the cooker. A warning included that the reflectors remain at ambient temperature, but the cook pots become quite hot. In the case of concentrator cookers, warn of risk for accidentally damaging eyes or burning hands at the focal point. Modern designs usually incorporate a deep parabolic reflector to avoid these types of accidents. See also: Health benefits of solar cooking
*Cooking capacity: Can the cooker prepare a meal for at least a small family, and/or specify size of family it is intended to cook for? In some cultures it may be important for the cooker accommodate a variety of covered pots and pans to prepare the local cuisine.
*Durability, maintenance: Repairs should be infrequent, and/or possible to do without special equipment, with replacement parts readily available or easily made DIY. Instructions included for ordinary maintenance or repair as needed (such as wiping off dust from windows and reflective surfaces). Information should indicate expected durability under various weather conditions, and/or guides for protecting it when weather may damage it. 
*Wind stability: The cooker should be reasonably stable in wind to avoid spilling food, or should include instructions to easily make it so (for example; tie-downs or placing rocks in specified places).
*Instructions: Clear guides for estimated length of cooking time and variables that influence cooking time (food quantity, wind, etc.) See: Guidelines and cooking tips
==Using your solar cooker==
The golden rule for solar cooking is get your food on early, and do not worry about overcooking. Most people starting to solar cook will be using a solar panel cooker or solar box cooker. These cookers are oriented to the sun and typically don't need to be turned to follow the sun during a 2-4 hour cooking period, though cooking time can be shortened if the cooker is turned. 
Once you have decided on a cooker, you will need to find appropriate cookware. Thin-walled dark enameled metal cook pots work well. They are good at heating up quickly. Glass jars can also be used, either clear or preferably painted on the outside. Please note that all cooking vessels need to have a lid, but not be completely sealed to avoid steam pressure build-up. Pots that reflect light, such as silver aluminum pots, will not work as well. Paint these first.
When using a solar panel cooker the pot is normally placed inside some sort of clear glass or plastic enclosure to retain heat and make use of the greenhouse effect.
==Introductory manuals==
*Solar Cookers: How to Make, Use, and Enjoy (There are also detailed versions in Arabic (, ), , , and , and .)
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* - Christelle Souriau & David Amelin (This is an excellent overview of solar cooking basics and simple solar cooker and dryer construction methods.)
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==Learn more==
*How solar cookers work
*Where is solar cooking possible?
*Interactive map of known solar cooking projects
*Why solar cooking is important
*Build a solar cooker
*Buy a solar cooker
*Integrated Cooking Method
*Solar cooking tips and tricks
*Cooking guidelines
*Recipes
*Solar cookbooks
*Health and safety
*Solar cooking frequently-asked questions
*Most significant solar cooking projects
*United Nations Sustainable Development Goals
*The history of solar cooking
*Solar cooking and emergency preparedness
*Promoting solar cooking
* - Edward Ortiz
==Audio and video==
*December 2024: Arizona, USA, residents show how solar cooking is part of their everyday lives
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*November 2020:
::thumb|none|400px|DARE to Solar Cook - The Physics of Cooking with Sunshine - Dr. Alan Bigelow, Mary Buchenic, and Jennifer Gasser
*June 2015:
::thumb|none|400 px|Our last series on the STAR-TIDES expo in Washington, DC continues with technology available for emergency crisis and disaster relief. VOA’s Carolyn Turner talked with Solar Cookers International about their exhibit displaying how to cook with only the sun - Voice of America
==External links==
*The Expanding World of Solar Box Cookers - Barbara Kerr (This is the full-text of the book by this solar cooking pioneer)
* - Christelle Souriau & David Amelin (This is an excellent overview of solar cooking basics and simple solar cooker and dryer construction methods.)
*Three part series by Sharon Cousins on practical, humanitarian, and environmental aspects and potential uses for solar cooking: Solar Cooking: Clean, Bright and Accessible, Out of the Smoke, Into the Sun, and Cleaner Cooking, Healthier Planet
==Debunking solar cooking myths==
===You cannot solar cook without sunshine=== 
*Heat-retained baskets allow one to effectively continue solar cooking when the sun dims, is masked by clouds, or at the end of the day. Solar box ovens are insulated and can still work on partly cloudy days. Thermal storage methods exist and research and development groups are pursuing the commercialization of thermal batteries.
===You cannot control the temperature when cooking===
*There are ways to adjust the temperature of a solar cooker. For example, on many different solar cooker models, you can use reflectors (or not), you can change the position of the cooker relative to the sun rays, you can use lids (or not), you can adjust how tight the heat seal is, etc. to adjust the temperature while cooking.
*Solar cooking has zero cost for fuel. When fuel cost is considered for other modes of cooking, solar cooking offers an economical solution, in comparison. You can make your own solar cooker for little to no cost by using materials found locally (maybe even in your own home); here are some open-source designs: http://www.solarcooking.org/plans/
===Most developing countries cannot afford it without government subsidies===
*There are best ways to have solar cookers available and affordable for people with low/limited income without subsidies. If needed, initial external support can help establish new solar cooker entrepreneurs in developing areas (to get up and running) until they are financially sustainable and can produce affordable solar cookers using local materials. This process generates successful models useful for furthering the global solar cooking movement. There have been successful approaches with a “pay as you go” with savings from funds that would otherwise be spent on more expensive types of fuel. Learn more about various funding approaches here https://solarcooking.fandom.com/wiki/Business_development
===Solar cookers are not appropriate in regions that experience monsoon seasons===
*Yes, there are monsoon seasons in East Africa and in other parts of the world. But then there are many more months per year outside of the monsoon seasons with days that are suitable for solar cooking. Also, during the monsoon season, after it rains, it is common for the sun to come out.
===Solar cookers are slow and cannot cook all types of food===
*Parabolic cookers are powerful cookers that can cook food as fast as when using a gas burner.
===Solar cookers are not useful because they do not work when it rains or at night===
*Solar cookers are intended as an integrated solution, to be added to cooking solutions that already exist in one’s home. Using solar cookers can reduce fuel typically used in other cooking systems. Solar cook on sunny days, use other cooking modes at times where there is no sun.
===You have to be outside in the sun when you solar cook===
*For most solar cooking, the solar cooker needs to be in the sun, but the solar cook does not need to stay in the sun. After a solar cook places their solar cooker in the sun in an area next to their home, they can return indoors to continue with daily tasks. When solar cooking while away from home, a solar cook can place their solar cooker in the sun and then seek shade to carry out other tasks while their food cooks in the sun. Some parabolic and Fresnel-lens-based solar cookers have a canopy that shelters the solar cook from direct sunlight when direct cooking attendance is necessary. Institutional roof-top-mounted solar cooking systems use solar-heated fluid to transfer heat to indoor kitchens for cooking
===You cannot solar cook during the wintertime at northern latitudes===
*Solar irradiation can be greater during wintertime in North America, for instance, because cold air is dryer with less humidity – lower humidity means few water particles in the air to scatter light. A well-insulated solar cooker can overcome freezing temperatures for solar cooking on sunny winter days. Even on days with frost-bite warnings, one can solar cook indoors by placing their solar cooker in the sunlight streaming through a South-facing window.
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