Changes: Introduction to solar cooking

Revision as of 23:07, 28 March 2016

Last edited: 1 March 2016

Solar_Cooking_in_Africa_-_A_Remarkable_Technology_Transfer

Depending on where you live and how you cook, solar cooking can save you time, work, and fuel. It is also environmentally friendly, and a fun way to prepare your meals. All foods can be cooked in some type of solar cooker.

Solar cooking is often associated with crockpot, or slow cooking. Cooking times for most solar cookers are typically twice that for conventional cooking methods. Slower cooking has its advantages however. Less water is used than with conventional cooking and foods retain more flavor and nutrients, rather than being steamed or boiled off.

Basic solar cookers do not require stirring the food while cooking. By leading the sun orientation a little and adding a bit more cooking time, box cookers and panel cookers can be set and left to cook unattended. Parabolic solar cookers reach higher temperatures requiring more attention to the cooking food. They need to be reoriented to the sun approximately every fifteen minutes, which can be done automatically if they are equipped with a solar tracking device. They are also able to fry and broil foods, which box and panel cookers are unable to do.

For areas in the world experiencing deforestation and limited access to clean water, solar cooking is proving to be a valuable part of the solution, by providing a safe smoke-free alternative to cooking and boiling water over open fires.

Buy or build a solar cooker?

Solar Cookers International sells the CooKit solar panel cooker for $39.00 USD online here.

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.
Purchasing a solar cooker is simple and you will often receive a higher-quality cooker than one you might build yourself.

If you want to build a cooker, visit the build a solar cooker page to choose a design that's right for you. You will find information comparing the advantages and disadvantages 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 is converted to heat energy, that is retained for cooking.

Most basic solar panel cookers and solar box cookers can reach 120°C (250°F). The captured sunlight passes through a greenhouse enclosure enclosing a dark colored cook pot. As it hits the dark surface, the sunlight is converted to heat, which can not escape the enclosure, and cooking temperatures are achieved. This principle is often experienced by drivers returning to a closed car that has been parked in the sun.

Solar Cooking basics, SCI 2004, pg. 1, 12-9-14

Solar Cooking basics, SCI 2004, pg. 2, 12-19-14

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 and also have the ability to fry and broil foods.

SolSource Solar Stove with Cookware — SolSource is an example of a parabolic solar cooker shown with cookware. The light is focussed at the bottom of the cook pot.

Industrial scale cooking, Solare Brucke, 6-10-15 — Institutional solar cooking can employ many large parabolic reflectors to generate steam, and cook for thousands of people daily. Many of these systems are in use in India. This example, was built with technology from Solare Brücke.

Main article: How solar cookers work

Solar cooker types

The three most common types of solar 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 institutions worldwide.

Box cookers

Box cookers typically cook food at temperatures between 110°C(230°F) and 150°C(300°F). They can often accommodate multiple pots, and usually take between one and three hours to cook various foods. The sides and bottom are insulated to retain cooking heat. Worldwide, they are the most widespread. There are several hundred thousand in India alone.

Main article: Solar box cooker designs

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 enclosure to retain heat. Panel cookers are capable of cooking at approximately 120°C(250°F). They are the easiest style to make and relatively inexpensive to buy. Solar Cookers International's "CooKit" is the most widely used panel cooker.

Main article: Solar panel cooker designs

Parabolic cookers

The AlSol 1.4 parabolic cooker demonstrates how the cook pot is supported to receive the focussed light from below from the reflector.

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 200°C(400°F). 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.

Main article: Parabolic solar cooker designs

Trough cookers

Early GoSun cooker, 2-29-16 — The GoSun is an example of a trough solar cooker that also uses an evacuated tube cooking chamber.

Trough solar cookers use a reflector to capture light that has a curved parabolic cross-section, but continues as a straight trough in the other direction. Instead of focussing 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.

Main article: Trough solar cooker designs

Evacuated tube cookers

SLiCK SM70 photo, 8-19-15 — The SLiCK SM70 is an example of an evacuated tube style solar cooker.

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 happens primarily by conduction and convection through a medium. With no air between the layers of glass the chamber is nicely insulated, well suited for retaining cooking heat. The chamber is so effective it often does not require a large reflector to capture sunlight. The ends of the tube are open so a slender cooking tray can be inserted. Improvements in glass technology is allowing for larger diameter tubes to be fabricated, which will allow larger cook pots to be inserted inside.

Main article: Evacuated tube solar cooker designs

See also information on pots, glazing enclosures, and reflective material, used to gather additional sunlight.

Cooking with 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 3-4 hour cooking period. Less water is added to recipes than you use cooking with more conventional stoves and ovens.

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. Cast iron pots also work, and are typically preheated in the solar cooker before cooking. The advantage of the heavier pots is that they will help maintain an even cooking temperature if the sun is occasionally blocked by clouds, but most solar cooks seem to use the enamel pots. Because dark cooking pots work the best in solar cookers, it is important to remember to use a nontoxic paint for the exterior cook pot surface if you choose to darken your own pots.

Main article: Guidelines and cooking tips

Getting started

Learn more

Why solar cooking is important
Most significant solar cooking projects
United Nations Millennium Development Goals
The history of solar cooking
Solar cooking and emergency preparedness
Promoting solar cooking
Problems helped by solar cooking

Introductory manuals

Solar Cookers: How to Make, Use, and Enjoy (There are also detailed versions in Arabic (Standard, Variation), French, Spanish, and English for Kenya, and Galician.)

Construction of solar cookers and driers - Christelle Souriau & David Amelin (This is an excellent overview of solar cooking basics and simple solar cooker and dryer construction methods.)

Solar orientation, Construction of solar cookers and driers, Souriau & Amelin, 6-9-15 — Solar orientation, Construction of solar cookers and driers, *Souriau & Amelin*

Audio and video

June 2015:

Star_Tides_4_Solar_Cookers — Star Tides 4 Solar Cookers

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)
Construction of solar cookers and driers - 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 potentials of solar cooking: Solar Cooking: Clean, Bright and Accessible, Out of the Smoke, Into the Sun, and Cleaner Cooking, Healthier Planet

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 [[File:Solar_Cooking_basics,_SCI_2004,_pg._2,_12-19-14.png|none|600px]]
-*[[Parabolic solar cooker]]s 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 and have the ability to fry and broil foods.
+*[[Parabolic solar cooker]]s 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 and also have the ability to fry and broil foods.
 ::[[File:SolSource_Solar_Stove_with_Cookware.gif|thumb|left|250px|[[SolSource]] is an example of a [[parabolic solar cooker]] shown with cookware. The light is focussed at the bottom of the cook pot.]]