Last updated: December 20, 2013
Panel-style solar cookers are the first solar cookers that are truly affordable to the world’s neediest. In 1994, a volunteer group of engineers and solar cooks associated with Solar Cookers International developed and produced the CooKit, based on a design by French scientist Roger Bernard. Elegant and deceptively simple looking, it is an affordable, effective and convenient solar cooker. With a few hours of sunshine, the CooKit makes tasty meals for 5-6 people at gentle temperatures, cooking food and preserving nutrients without burning or drying out. Larger families use two or more cookers (See: Cooking for large groups).
The CooKit is made of cardboard and foil shaped to reflect maximum sunlight onto a black cooking pot that converts sunlight into thermal (heat) energy. A heat-resistant bag (or similar tranparent cover) surrounds the pot, acting like a greenhouse by allowing sunlight to hit the pot and preventing heat from escaping. It weighs half a kilogram and folds to the size of a big book for easy transport.CooKits are now produced independently in dozens of countries from a wide variety of materials at a cost of $3 - $7 US. Note that you can either build your own CooKit using the plans below or you can order a pre-built Cookit from Solar Cookers International. Your purchase helps support SCI's work around the world.
CooKits complement other cooking methods needed at night and on cloudy days. Coming about twenty years after the first efforts to replace open fires with improved cooking stoves, the CooKit uses no fuel at all. The CooKit is both user-friendly and environmentally friendly. Families can save scarce, expensive fuel for when they cannot solar cook and when economically capable, add other, higher cost cooking improvements such as modern biomass, smoke hoods, biogas, or liquefied petroleum gas. A single CooKit of normal dimensions (see below) is not able to cook a pot of food large enough to feed a large family. To cook larger amounts of food a box-style cooker may be a better choice.
Addressing fuelwood scarcities:
- The CooKit saves more than four times its value in fuelwood each year. With careful use and storage, a CooKit can be used for two years, reducing fuelwood consumption by two tonnes.
- Reduces pressure on forests for firewood and charcoal.
- The CooKit can pasteurize household drinking water, making it safe to drink.
- The solar cooking process is smokeless, reducing respiratory diseases and eye irritation
- Solar cooked foods retain vitamins, nutrients and their natural flavors; there is no smoky taste; the foods cook slowly in their own juices. Nutritious, slow-cooking traditional foods (beans, root crops, and some grains) are restored to the family diet
- Clean up is easy as the food never burns or sticks to the cooking pot.
- Solar cooks frequently report that the money they save on cooking fuel purchases is used to for many essentials, such as extra food, school supplies, and medical care.
- Without having to gather wood or dung, breathe smoke, and tend a fire – all associated with traditional cooking – solar cooking is easy and safe for people with AIDS and other illnesses, the elderly, disabled and young orphans.
Enhancing household and women’s economic status:
- The CooKit repesents a new opportunity for women to capitalize on an underserved market and better meet their own cooking energy needs
- Solar cooking saves time as there is less need to tend a fire or collect firewood. A person can cook while at work, at the market, or tending crops. Young girls can attend school instead of searching for fuelwood.
- Solar energy is free and abundant in many areas of Kenya, providing a safe, clean, healthy supplement to traditional fuels.
Co-developers are Roger Bernard of France and Barbara Kerr of the USA, with work also by me n Ed Pejack, Jay Campbell, and Bev Blum of Solar Cookers International. Extensive field tests in the USA and in many developing countries confirm its performance, convenience, low cost, acceptance, and adaptability to diverse needs.
NGOs using CooKits
- Solar Cookers: How to Make, Use, and Enjoy. This is a handbook published by Solar Cookers International that includes detailed plans for building a CooKit solar panel cooker. (There are also detailed versions in Arabic (Standard, Variation), French, Spanish, and English for Kenya, and Galician.)
- 35-minute instruction video of how to build a CooKit solar cooker, how to use it, and why Girl Guides and Girl Scouts are teaching the technology in fuel-short countries around the world. It's yours for a donation of $20.00 (US) to the Girl Scout Solar Cooker Fund (postage included). To order...
- Simple plans in other languages: German, Indonesian, Luo, Persian, Portuguese, Russian, Spanish, Italian
Creating a template by enlarging the diagram using MS PaintPrinting the plans to size avoids the need to measure any lengths or angles since you merely have to cut out the plans and trace around it on your material. This is done by a "poster print" and most computer printers and image programs allow you to create a poster print.
The process is to determine how much larger the measurements on the plan are compared to what is printed. Then the plan is enlarged so that it prints the actual size - where all displayed measurements match actual lengths.
For MS Paint, which is installed with Windows, the steps are:
- Copy and paste the image into the program. Right click the image to "Copy"
- Select Page Setup from the file menu and change the page layout to Landscape.
- Print - this should print the details out in the "normal" plan size which is reduced from the full size plan.
- Find distance on the printout, such as the width (122 cm, or 48 in) and measure with a ruler. Divide the distance on the plan by your measurement. For instance, if you measured 19.7 cm (7 3/4 in) the ratio would be approximately 6.19. This means the image should be magnified 6.19 times (619%) to match the values in the plans.
- Select Page Setup menu item again. This time adjust the scaling to the percent calculated in the last step (619% based on the values shown in step 4). MS Paint will now automatically enlarge the plans so that they roughly match the original plans cm for cm (or inch for inch).
- A number of pages will be printed. These pages need to be joined together. Printers normally require a margin, so make sure you overlap one page with another and fold appropriately so that printed lines are continuous.
- Cut out the plan/template.
You now have a template with no need to measure a single line nor angle. Place it on your material to mark cut lines and fold lines.
PDF file for printing out a full-size template
You can download this PDF file to print out a full-size template at a copy center. You can then trace this template onto cardboard to make a CooKit with the exact dimensions and angles as the model sold by SCI. This eliminates having to lay out the pattern manually, or printing the template out in sections, and will simplify the construction process: Full-size CooKit template for printout
You can also download this PDF file to print out the full-size template on 25 pages of 8.5 x 11 in (standard US Letter size) paper. No resizing necessary - just open and print, then tape the pages together. Each page overlaps the next page by 10 mm (3/4 inch) and has guide marks in each corner to help with alignment. Full-size CooKit template for printout - Tiled.
Tips and tricks
- To make clean straight folds in cardboard, first make a crease along the line with a blunt edge such as a spoon handle, then fold against a firm straight edge.
- Make the slots a little too small and narrow so that they fit snugly to hold up the front panel.
- To set up, lay panel flat with shiny side up. Fold up front and back parts and fit back corners into the slots in front.
- Arbitrary size can be obtained when creating the template. Choose a limiting dimension and use this size in the calculations in Step 4 rather than the size shown on the plan. Therefore, if you have a 110 cm (43 in) wide pice of material you would divide the measured width on the plan by 110 instead of 122 (48 in). This will scale the plan up or down based on your needs.
Put your food into a dark-colored pot with a dark-colored or clear lid.
Plastic bags and other glazings
See tips below for using normal (non heat-resistant) plastic bags. Note that when solar cooking conditions are very good, you may be able to cook without the use of a plastic bag around the pot.
Choosing a cooking location
Set the Cookit on a dry, level surface in direct sunshine away from potential shadows. For best results, solar cooking requires continuous, direct sunshine throughout the cooking period.
Orienting the CooKit
(Note: Directions below are valid for the Northern Hemisphere)
- TO COOK A NOONTIME MEAL orient cooker so that it faces to the southeast, approximately where the sun will be mid-morning. In general, it is good to get the food out early: for most dishes it is best to start cooking by 9:00 or 10:00 a.m.
- TO COOK A EVENING MEAL orient cooker so that it faces to the southwest, approximately where the sun will be mid-afternoon. For most dishes it is best to start cooking by 1:00 or 2:00 p.m.
- FOR ALL-DAY COOKING orient cooker so that it faces where the sun will be at noon or early afternoon. Food will be ready and waiting for the evening meal.
For recommendations of cooking times for specific foods, see Foods.
Adjusting the front flap
Cooking on windy days
Care and Storage
Store the CooKit in a safe place away from moisture and animals, preferably indoors. Allow plastic bags to air-dry or gently wipe dry with a towel. The CooKit is compact and portable. When not in use, it can be simply folded lengthwise into thirds or folded flat into a 33 centimeter (13 inch) square.
Tips and Tricks
|Dr. Steven Jones found that raising the pot on a wire frame improved cooking in a panel cooker. It is also possible to set the pot on a clear glass bowl.|
|Glass bowls and pie pans can be used to raise the pot off of the bottom of the cooker (note that the pot would normally be enclosed in an oven cooking bag when using a panel cooker). In some cases, they may provide more stability used upside-down.|
|Wietske Jongbloed created a simple frame to allow the use of normal plastic bags (instead of heat-resistant oven cooking bags).|
|Jose Albano created this frame to protect normal plastic bags (photo shows frame with bag removed).|
|Dr. Ashok Kundapur has suggested a way to make a housing out of flat plastic sheeting. A bottom cylinder is supported by wire frame while a transparent cover, made of the same plastic material, makes access to the food very easy. This arrangement can also be used for retained-heat cooking.|
|Stephen Harrigan found that discarded plastic phone cards, which are readily available in Africa, worked well to strengthen CooKits in their most vulnerable areas. See also Making the CooKit more durable.|
|To remedy the moisture problem inherent in a product made of cardboard, the Solar Cookers International East Africa Office and colleagues have added notebook binding tape, also readily available in large cities or capitals to seal steno notebooks for students.|
|Nikwax has been used to waterproof and increase the durability of CooKits, reportedly extending the life of a CooKit by 50%. It's early use was in refugee camps in Chad as a result of a collaboration between Nikwax and TchadSolaire.|
- Stephen Pearson reports: "We build CooKits in pieces use eleven small panels of cardboard. Shops even in rural areas have thin cardstock available as scrap. These can be laminated together using local cassava glue (cassava is grown all over Africa) to form stiff panels, thus avoiding the need to import thicker cardboard. Join the eleven panels together with [5 cm] 2 in strips of worn out dress or shirt (using the cassava glue). Protect the perimeter of the 11 panels with more [5 cm] 2 in strips ([2.5 cm] 1 in front and 1 in back to stop delamination of the cardboard). Let each panel dry properly. Then turn it over and glue on the aluminum foil to the side with no cloth hinge strips."
- CooKits are available through the New Internationalist shop.
- See NGOs using CooKits to possibly purchase from one of these groups.
Manos Unidas variation
Solar Cookers International's standard CooKit calls for a lot of curves, which can be hard to make with a hand held blade. Juan Urrutia Sanz of the Manos Unidas organization in Spain writes that his group promotes a variation on the CooKit shape that is easier for many people to make at home. The Manos Unidas version, called Cocinsol II. Señor Urrutia y Sanz reports that it cooks as well as the CooKit and actually has more reflective surface area. SCI's Jay Campbell agrees. Jay is an engineer who has chaired the SCI Research Committee and who worked on engineering the CooKit for manufacture in Kenya. (One key advantage of the CooKit's curved shape is that it is easier to figure out a way to fold it into an album-sized package for easy storage and transport.) To make your own Cocinsol II, use the shape and dimensions shown in the graphic. Cardboard is an inexpensive material to use which holds its shape and is also easy to fold. However, woven mats or baskets, molded plastics or wood can be used. The solid lines in the design show where to cut; the dotted lines show where to fold. Cover the surfaces of one side with shiny material such as aluminum foil or shiny gift wrap (which will reflect light to the pot at the center of the cooker).
As part of their testing, Florida Solar Energy Center engineers redesigned the CooKit into a new geometry. The new design simply takes the same amount and type of material that makes up today’s CooKit and reconfigures it into a different shape. They dubbed it the “High Back reflector” because it has a back reflector that is much higher (i.e., taller) than the one in the standard CooKit.
Mr. Gnibouwa Diassana, of Bla, Mali has been able to find sources for all the materials in or near Bla. “Cardboard is available in big towns,” he writes. “Plywood, glass, aluminum foil, sheet metal and plastic bags are available in Bla and neighboring towns.”
Mr. Diassana also applies creative thinking to obtain low-cost materials. He notes that tea, a very popular beverage in Mali, is shipped from China in boxes lined with aluminum foil which can be recovered and reused for making reflectors for solar cookers. “It works well,” he says.
What is lacking in Bla, however, are large pieces of cardboard. To adapt to this problem, Mr. Diassana makes solar CooKits from five pieces of cardboard (see figure 1), which he patches together using small thin pieces of cardboard or pieces of satin fabric (glued or sewn into place to hold the large CooKit parts together, see figure 2).
Philip King writes of his variation:
I've made one CooKit and wanted to make more, but each time I've looked at the published plans I've found that they don't suit my way of thinking. I also find them difficult to scale to suit an arbitrary size of material. So, and in case there are others like me who get dizzy looking at all those angles and inches and centimetres, I've drawn my own design with the following intentions:
- to use as few measurements as possible
- to use an arbitrary unit
- to find all angles automatically
- to use straight-line cuts throughout
- to use as few cuts as possible (I could still lose a few)
- to derive details easily without a template
- to eliminate guesswork or fudging
- to reduce the need for written instructions
I also wanted it to be as close as possible to SCI's classic and well-proven CooKit design but have some distinctive features of its own.
Of course, the production-line cookers are quite quickly made using templates, so this new plan has no advantage there. It is really intended to help those who are making a one-off cooker out of whatever randomly-sized material they happen to get hold of.The design which follows is really meant for heavy corrugated board and not intended to fold to a small size (that's not to say it wouldn't if thin enough, I just haven't worked out yet how to derive the folds) and although the back angles are pretty close to the classic design they are different to a couple of degrees. The front panel is deeper and the back lower than in the classic, but not by much.
The chevron cuts in the ends of the side wings are to retain some surface area while also making the tabs narrower to fit the slots. I had an earlier design with a wider base and front panel to accommodate longer slots, but I like this one better, even though it adds a couple of cuts. The chevrons also satisfy my desire for a distinctive feature. The snips off the corners of the wings are to help with very stiff material when fitting the points into the slots; they don't really have to be measured, just a bit snipped off.
The basic unit is the orange block, and a unit size of 1.5 inches gives a sheet size of 48 in x 36 in. Clearly, a unit size of 1" makes a sheet size of 32 in x 24 in. Working in metric, a unit size of 4 cm yields a sheet size of 128 cm x 96 cm, which is about five per cent larger than the 48 in x 36 in sheet.
I have also made this plan available as a PDF file.
Having just made a full-sized example from this plan I can confirm that it is fast and accurate. However, I know how it's supposed to work, so I would welcome comments from anyone who tries to follow this plan to build a cooker.
- Scalable CooKit design simplifies measurements - Solar Cooker Review
- Full-resolution PDF file showing this design - Philip King
In February 2008, Stephen and Sheila Harrigan shipped 275 of these durable plastic CooKits to the Sakali Refugee Camp in Sudan. The Poly-Furnace is a cut down model of the Cookit made by Solar Cookers International. Because of the adverse living conditions of the refugees in Darfur, Sudan the cardboard Cookit will not last much more than 6 months to a year. The need to have a durable Cookit has prompted us to develop one made of plastic polypropylene flute board. Reflective aluminum polyester is attached to the surface before it is cut and formed. A local group of volunteers have begun to make these for introduction into Sudan 2008.
See also Making the CooKit More Durable.
The Eagle Solar Cooker was designed in 2007 by Manda specifically for Americans. It is made of eleven pieces which begin as 21.5 cm x 28 cm (8 1/2 in X 11 in, U.S. standard letter size) paper. Intended for students and beginners, it is easy to construct; no protractor or compass is used. An optional twelfth piece, of a whimsical eagle head, can be added at the top.
Aluminum panel variation
Hans and Petty Heerebout founders of Solar Cooking Project Zambia, have experimented with an aluminum panel version of the CooKit. They feel the cooker is able to reflect more light than the standard CooKit, and more weather resistant.
Teong Tan variation
Here are several ideas for the modifying CooKit. First, the size of
the cooker can be reduced so that more cookers can be made from the same
amount of construction material. Secondly, the panel locking feature can be
relocated so that the two sides of the front reflector can be tilted to reflect more sunlight towards the desired direction. The modified CooKit is structurally more robust, and can be positioned upside down to cook when the sun angle is low. The cooking pot receives more reflected sunlight under the normal operating range of the cooker. The modified CooKit can be folded down into a small package for easy transportation and storage just like the original design. Review more of Teong's description at:
Teong Tan variation layout diagrams
An enthusiast has submitted photos of the Teong Tan variation positioned to capture low sun angles, and in the standard overhead orientation. He was able to do some winter cooking in Ottawa, Ontario, Canada (latitude 45°) and had the cooker reach 180 °C (285 °F) in the vertical position, using a pot inside clear pyrex container.
Matthew Rollins has made a quick scale model of a CooKit using mirror card, shown in the adjacent photos. He deliberately left off the folds and creases that are necessary for the outdoor leisure market minimum package size scenario. He feels there are at least two distinct markets for solar powered cookers and other devices. The Developing World does not need a cooker that has been creased and folded in such manner as to cripple its capabilities. The normal fold away CooKit delivers only 184 watts equivalent of power according to scientific tests carried out by Ed Pejack. Leaving off the fold and creases on the back panel increases the CooKit power to over 400 watts, and costs nothing more. This variation doesn't fold down as small as the standard design however.
Haines Solar Cooker variation
The Haines Solar Cooker uses design aspects of the Funnel cooker and the CooKit, and is made from mylar-coated bubble insulation material, which is unaffected by boiling water, and should be more durable than a cardboard design. It requires only two cuts for cooker assembly. Testing has shown it to maintain hotter temperatures than the CooKit.
Two-pot CooKit variation
This simple idea was suggested by a soldier serving in Afganistan, Colin Hoskins. Using only 10% more material, the cooker doubles the cooking area.
Gasy Nahandro variation
This CooKit variation makes use of local materials to create a very affordable cooker. It was designed by Dominique Dutoit for use in Madagascar. The panels are constructed from woven grass mats, and then covered in reflective material. The target is to be make to make the cooker for less than $2.00 USD, and be able to offer them through local retail stores.
Quickie Demonstration CooKit
You can make this “quickie” version of the CooKit on-the-spot for teaching purposes. It only cooks small quantities of food, but it can be used to demonstrate solar cooking concepts by warming foods, melting cheese and chocolate, heating water, etc. It is not intended as a substitute for a standard solar cooker.
It involves cutting a typical cardboard box (about 0.6 x 0.6 x 0.3 meters, or 2 x 2 x 1 feet) in half diagonally. Then add a cardboard flap in front and cover the inside with tinfoil.
One Sheet variation
This is another multi-pot variation of the CooKit, designed and tested by the Proyecto Olla Solar in cooperation with the Mexico Fund for the Conservation of Nature. Initially tested using a mylar reflective material, the Xuni reached a temperature of 85 °C (185 °F) in three hours.
The Cook-n-go variation has been designed and is manufactured by the Aftarkeia Network located in Greece. The panels are made of wood and are hinged together. When folded the package is quite compact.
A Simple CooKit
Audio and video
|April 2008: The solar cooker students from last year are training their neighbors in the Sakali Refugee Camp near Nyala South Darfur, Sudan|
|Local Fabrication of the Cookit in Africa, Eritrea|
|September 2007: The CooKit being used in Chad refugee camp|
|Video showing how to make the Solar Cookers International version of the CooKit|
- The link below shows the animated result of a Simulation of a cross section of a CooKit. It does not include the power from the side reflectors.
- This video shows the power contributed by the side reflectors. The display picture shows a view of each reflector. Each reflector is divided into pixels. Each pixel corresponds to an elemental area of the reflector. Black pixels define the extent of the reflector with a white line representing the boiundary between the rear and front portion of the reflector. Pixels corresponding to elemental areas from which reflected sun rays hit the pot are shaded. Rays from the white pixels hit the top of the pot. Rays from dark gray pixels hit the side of the pot. Rays from light gray pixels hit the bottom of the pot.
- Solar Cookers: How to Make, Use, and Enjoy - A handbook published by Solar Cookers International that includes detailed plans for build a CooKit solar panel cooker. (There is also a French version, an Arabic version, and a Kenyan-English version.)
- Instructions for using the CooKit solar panel cooker
- November 2009: Manual: How to make a CooKit and a WAPI - Solar Cooking Netherlands and the KoZon Foundation.
- June 2007: Research Study on Improvements to the CooKit Solar Panel Cooker Carried Out by Dr. Dale Andreatta and His Students in 2007 - Dale Andreatta
- May 2007: Making the CooKit More Durable - Stephen Harrigan
- July 2006: Optical Properties of the CooKit Solar Cooker - Ed Pejack
- 2006: A Report on the Evaluation of the KoZon Foundation Cookit Projects in Northern Burkina Faso - Jantje Struif Bontkes and Wietske Jongbloed
- February 2002: Tests of the CooKit conducted by the Florida Solar Energy Center
- Greenhouse enclosure comparison - Teong Tan
- The Fun-Panel solar cooker, which is similar to the CooKit, but can be made from a single cardboard box.
- Nikwax homepage
- CooKit Simulation and New Simulation Tools - Earthbound Technology
- Buy from Solar Cookers International in Sacramento, California
- Plans for the CooKit in many other languages
- April 2008: Interview with Linda Frederick Yaffe discussing what it's like to cook with a CooKit - Wildebeat
- The Big Adventure of a Little Solar Cooker - Roger Bernard (In French La Grande Aventure d'un Petit Cuiseur)
- Greenhouse Enclosures Comparison Tests - Teong Tan