Solar Cooking
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Last edited: 29 November 2021      

Dark-color pots with a dark or clear lid work best

The best solar cooking pots are typically made of thin, dark metal with a lid. Pots with polished finishes, which reflect light away from the pot instead of absorbing it should be avoided. Unless you're cooking with a parabolic solar cooker where the light is being focused on the bottom of the pot, it's very important to use dark-colored pots that absorb light and transform it into heat.

Clear pots will also work, especially with dark colored food ingredients, and pot lids can be either dark or clear. It is important to always cook with the lid in place so that the moisture from the food doesn't escape and fog the plastic bag or other glazing.

The material that the pot is made from will also affect how quickly it heats up and how well it retains the heat. Here are a few points to keep in mind:

  • Pots made from thin material heat faster than thicker ones
  • Metal pots will heat faster than ceramic or earthenware
  • Cast iron is slow to heat initially, but will hold heat better than thinner metals. Cast iron should be preheated in the cooker and be used during good solar cooking conditions, as it requires strong sunlight to achieve the best results
  • Foil is not generally recommended to wrap food for solar cooking because shiny foil insulates by reflecting sunlight and heat away from the food.

Ideally, the pot/cooker combination should be able to cook a large enough meal to feed the entire family, which can have many members in some cultures. Some introductory projects have not succeeded because the amount of food cooked was not enough to meet the needs of the families who participated.

Glass jars[]

Solar_cooking_food_in_jars_to_put_in_solar_ovens

Solar cooking food in jars to put in solar ovens

Solar cooking with glass jars

Glass jars make good pots either clear or painted out the outside. They may cook slightly better darkened. Also, darkening the outside of food containers will protect some of the B Vitamins. When painting the jars, a strip of masking tape placed from top to bottom before painting can be removed when the paint is dry to leave a tidy strip of clear glass for visual inspection of the inside.

When using jars for cooking, make a hole in the lid of any non-canning jar, such as mayonnaise jars, peanut butter jars, etc., to prevent steam buildup. Dome and ring canning jar lids that are designed for food preservation automatically release excess steam pressure yet are safe only when used on canning strength, food preservation jars. The thickness and strength of non-canning glass jars is not intended to take the strain of steam under pressure and could break explosively unless vented.

Earthenware pots[]

Some low-fired earthenware pots do not initially cook well although dark colored, hard-fired earthenware pots with glazing work very well. Perhaps the poor performance of some earthenware is due to liquid soaking through and evaporating on the outside, or perhaps it is due to the thickness and porous nature of low-fired clay pot sides. Experimentally, in the efforts to use low-fired, unglazed earthenware, the goal has been to approximate the hard-fired pots by filling the pores and to providing a form of glazing. On a homecraft basis, this has been done by saturating the pot with food-type oil, fat or natural resin which both closes the pores and changes the surface. Oil also will conduct heat rather well and this may be part of what improves cooking in low-fired, earthenware pots following oil treatment. Light colored earthenware needs to be darkened on the outside only, perhaps by rubbing a dark food, nontoxic dark powder or soot from clean wood into the oil coating. Even so, there may be forms of low fired earthenware that are difficult to use.

Paints to use[]

Main article: Paint

Buying pots[]

  • The classic Granite Ware 3qt. cook pot with lid, which fits nicely inside of two 3qt. clear Pyrex bowls, is available on Amazon intermittently. To use the Pyrex bowls as a greenhouse enclosure, avoid the 3 qt. pots with side handles.
  • It can be difficult finding smaller covered cook pots in a Graniteware option. A dark colored covered bread pan size has been found from a Hong Kong vendor. Note that this pot has three small holes in the bottom of it apparently to allow steam to escape while baking bread. It is available in quantities of 50+ from Banggood.

Pot lids[]

Pot lids can be homemade by turning the pot upside down on a flattened piece of metal and drawing an outline. Cut the metal about ¼ inch (.6 cm) outside the line. File or sand the sharp edges to dull the cut surfaces and protect the fingers. This may be done simply by rubbing a rock along the cuts. Working regularly around the lid piece with pliers, bend the edge down at the line. Sometimes the fluting looks nice. If necessary, cut from the edge into the line to allow the pieces of edge to overlap. Darken the outside of the lid and heat it for several hours before using it with food. Temporary lids made be made by the same method using a brown paper bag and creasing the paper at the line. These also need to be heated alone for several hours before being used with food. Sometimes small holes are punched in a lid to allow moisture to escape and produce a drier crust on foods such as breads or breadcrumb toppings, cakes and cookies.

Nutritional research in great detail has been done by Professor George Hammons and others at Philander Smith College in Little Rock, Arkansas, USA. After analysis of many different nutrients in food cooked equal times by conventional methods and by solar box cookers using dark pots with lids they concluded that solar cooked foods retained nutrition as well as or better than foods cooked by conventional methods in spite of the longer cooking times required.

Metal pots can be painted black for use in a solar cooker.

Clear lids[]

Teong Tan found that a black pot with a clear lid without a plastic bag (left) heated faster than a normal dark pot with a dark lid inside a plastic bag (right). See Greenhouse enclosure comparisons.

Teong Tan did side-by-side controlled tests using various pot/glazing configurations. What was not expected was that the pot with a clear glass lid had outperformed the pot with a metal lid plus oven bag. He states that this could be due to:

  • The metal lid had prevented sunlight from reaching the inside of the pot, where it mattered the most.
  • The downward conduction and convection of heat, from the hot metal lid to the lower part of the pot, were not efficient.
  • The amount of sunlight coming in from the top was significant, and this had helped to rapidly raise the temperature of the pot with the clear glass lid.
  • A dark opaque lid may help with browning the top of bread.

Read the report...

It should be remembered that using a pane of either float or plate glass that is too thin runs the risk of breakage while handling or when cooking. Tempered glass, like that used in manufactured pot lids, is a better option. Read more about glass properties

The EuroSolarPot (prototype ESP-28) is an innovation of Andrew Kotowski

. Built by Andrew and Margot, it has been tested successfully in France and Poland. The pot is designed for use in solar panel cookers, especially in the Nordic countries. Thanks to the greenhouse effect, its thermal properties are improved compared to traditional solar pot. Click here for more information.

Tips and tricks[]

Dr. Steven Jones found that raising the pot on a wire frame improved cooking greatly when cooking in a Panel cooker.

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.

Alternatives to plastic oven bag pot covers — L. to R. — Clear plastic/acrylic bowl (cheap seasonal purchase) over 4 qt. Pyrex bowl, straight-sided glass vase (from Michael's Craft Store) cover with candle-plate base (holds up to a half-gallon cooking jar), glass apothecary jar, plastic canister over glass candle-plate. In cold or windy conditions, solid pot covers give a definite advantage over oven bags.

A dark bowl placed inside a glass casserole dish works very well for solar cooking. No plastic bag is necessary.

A double Pyrex style bowl enclosure with clips.

In certain cookers, such as the Lightoven III shown here, pots can be stacked.

When cooking with a pot that is only partially full, put the lid on upside-down. This moves the pot lid (heated by the sun) closer to the food. Im some cases, the upside-down lid will even be in contact with the food and will thus transfer the heat to the food even better.

Pots can also be stacked to allow more than one dish to cook at a time.

Sophie Brock Lyman demonstrates her successful trial using a typical broiler pan to roast vegetables, with the drip tray as the lid.

Matteo Muccioli has designed a cook pot/greenhouse 'bowl-in-bowl' combination for his Kimono Solar Cooker, Photo credit: Matteo Muccioli

Pot risers[]

November 2016: 

SunLife, working in Ghana, has developed a simple wood and wire harness to elevate a cook pot, as well as, provide a way to lift the hot pot either with or without the cooking bag enclosure. The wire frame also maintains an efficient shape for the enclosure.

Covering reflective pots with a dark cloth[]

The NG cooking method.

When cookware with a black surface is not available, it may still be possible to effectively use reflective or colored cookware with your solar cooker. Basically, it involves using a black cloth to cover the cookware after placing it in the cooker. Place the cloth as close to the pot surface as possible to minimize heat loss. Neelaratna Geekiyanage, from Sri Lanka, reports that he has used this technique to cook, pasteurize water, and make copra from scraped coconut to extract high quality coconut oil. He calls it the NG method.

Some alternative cooking pots[]

  • Smoked-glass casserole dishes. Pyrex makes a low-cost model available for $5 - $10 in stores in the US.
  • Rough up glass jars with sandpaper and paint these black. Use masking tape to leave one clear strip for viewing.
  • Cook in gourds with a small sheet of glass for a lid.
  • Put shiny pots in a brown paper sack.
  • Paint a shallow cake pan black and fashion a lid from a sheet of black-painted aluminum flashing with its edges folded down.
  • Buy dark baking pans in matched pairs and use one upside-down as a lid for the other. Metal binder clips of the right size—medium to large range, depending on the pan rims—work well for holding them securely together.
Arezki Harmim finned pot 2009.jpg
  • Finned pots: Arezki Harmim writes in February 2009: "Within the framework of a project of development and popularization of solar cooking in Algerian Sahara, registered in the program of the Unit of research in renewable energies in Saharan medium installed in Adrar (located at the south of Algeria), our team of research proposed the use of a finned cooking vessel with an aim of improving the solar cookers performances. Fins attached to the external surface of the cooking vessel increase the heat transfer surface area. This improves the heat transfer from the internal hot air of the cooker towards the interior of the vessel where the food to be cooked is placed. Indeed the various experimental tests carried out with the help of a double exposure solar cooker and a finned cooking vessel showed that there is a clear reduction of the cooking time in comparison with the same cooker tested under the same conditions but with an ordinary cooking vessel. The same results were also recorded with a simple box type solar cooker. An example of the finned cooking vessel is shown in the figure."

Jar-in-jar cooking chamber[]

Glass jar inside of another glass jar cooking chamber

Bernhard Müller has created a small cooking chamber and pot combination by inserting a black painted glass jar, with metal top, inside of a slightly larger clear glass jar with a similar top. The two metal tops should be either riveted or screwed together with stainless screws.

An extremely important feature is to punch a pressure relief hole through both tops. Without it, there is danger of explosion if the lids are sealed too tightly. Care should be taken when cooking with glass jars to avoid accidental breakage. Some jars, like the Mason style used for food canning, are made with heavier glass than is typically used in commercial food sales. While stronger, it does not compare to the strength of Pyrex cookware. The inner jar painted black will become quite hot.

Blackened coffee can with glass lid[]

Here, a blackened coffee can with a glass cover is used as a pot. Under ideal conditions cooking can be done without a glass or plastic enclosure.

Build your own HotPot bowl[]

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HotPot homemade2.jpg

A few creative solar enthusiasts have been working on ideas to make a HotPot bowl that is inexpensive and easy to use. They incorporate a black pot inside of a larger Pyrex style bowl and lid with an insulated handle. As seen in photos, the addition of a wooden spacer ring has helped provide a seal between pots of slightly different sizes.

Candidates for components include:

  • Pyrex® Sculptured 4-3/4-qt Bowl
  • Pyrex® 2-qt Casserole w/ Cover <--(only large one sold w/cover)
  • Pyrex® 4-qt Mixing Bowl
  • Granite Ware 4 quart beanpot
  • Granite Ware 4 Quart Stockpot with Steamer Insert
  • Granite Ware 4 Quart Covered Sauce Pot
  • Global Sun Oven, Granite Ware, Enamel, 3-quart Pot


Reports[]

Audio and video[]

  • May 2020: Cooking with multiple pots stack on each other:

See also[]