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How to make a Parabolic Solar Cooker


A little intro

Solar cookers are a great way to cook food using the energy of the sun.  They can be made from various materials that are available and don't require a fuel source like other cooking devices other than sunlight.  The basic idea behind making a parabolic solar cooker involves concentrating the solar rays to a point or region that food can be warmed at.  Unlike other solar cookers that involve trapping heat in a confined box, parabolic solar cookers just focus the heat onto the food.

Here are some pictures of parabolic solar cookers that may inspire or better explain the process.
Parabolic solar cooker pictures This site has pictures of parabolic solar cookers that have been used all over the world.  Most of the designs are pretty similar but some have distictly different elements that may be more useful for different regions or building materials.  The images can be viewed larger if clicked on.

As one would suspect, parabolic solar cookers are based on a parabolic curve.  This involves relatively basic math skills for those that have finished high school algebra.  This is not always a reality in third world countries where this is likely to be promoted so the basic design can be taught by a volunteer or agency.  This, if the level of education is high enough, can be used as a way to teach math in schools as well.  It is a direct way to show the useful elements of math in everyday life.  

Here is a good site about cookers in India: a great introduction to the idea of solar cookersThis site is from a compilation of site that focus on India.  This site focuses on the logic of using parabolic solar cookers in India.  There is also a breakdown of the different materials and elements important in making a cooker.

Here is another introduction to the different types of solar cooking This is a pdf that goes through the construction and different types of solar cookers for developing countries.

Good site for many of the pros and cons of solar cooking
This site runs through the differnt kinds of solar cookers that can be made and a run down of what kinds are good for different situations.  i.e. how complicated the project should be.  This is a good site to look at before deciding to make one in an area that has not had them before.

Why?

Parabolic solar cookers are not going to use up precious fuel sources and will not pollute the environment with toxic chemicals, green house gases (particularly carbon dioxide) or obnoxious odors.  Parabolic solar cookers are easy to make and can be used to heat food or water.  The time involved is reduced because fuel does not need to be collected and a flame does not need to be maintained.

Carbon dioxide impacts on the environment Site covering the history of carbon dioxide in the atosphere and the problems associated with increased carbon dioxide.

Mona Foundation: rural women making parabolic solar cookers A foundation decdicated to raising the status of women in all countries.

A short math lesson
The basic equation of a parabola is y=x^2
Remember this?!?  Take your x and square it.  If x is 1 then y is 1. Go over one and up one.  If x is 2 then y is 4. Go over two and up four.  It is an exponential increase.  This curve causes the lines from a point source to be focused at one point.  In other words, when the sun's rays hit the sides of the cooker, the shape of the cooker causes all of the rays to focus at one point and allow heating of whatever is there.  Manipulation of the equation can cause a change in the focal point of the rays.

Why use a parabolic shape? Link from HSU showing how the parabolic shape allows for the concentration of solar rays to cook food.  The four graph links on the right side of the page allow for the creation of a parabola that can be printed and traced to make a cooker. TRACE A COOKER HERE

A wonderful website for determining where the focal point will be.
Directions on making a parabolic solar cooker from the CCAT group at Humboldt State University. This site is great for explaining how to create a solar cooker.



Constructing your cooker
Things to remember when collecting materials:

1) the inside will need to be shiny to reflect solar rays
2) the dish will need to be on some sort of platform to angle it in the direction of the sun
3) think about where it will be used and for what (size) and how much it will be moved around (weight)
4) optional: an arm or bar to hold the food or pot
5) cost

A previous example of making a parabolic cooker.
Some more basics about parabolic cookers This is another good site for tracing a parabola.  This site explains how the curvature of the parabola reflects all the sunlight to the same source. TRACE A COOKER HERE

Thinking about (1)
    Anything shiny to line the sides of the cooker will work.  Most often metal is used but when working in a situation with few resources, it is time to get creative.  Snow is quite reflective and the solar rays will be focused not on the snow but above it so a makeshift snow solar cooker is a possibility.  Foil pieced together will work such as gum wrappers or packagings of candy.  

Thinking about (2)
    As most of us have notice, the sun moves across the sky, it doesn't stay in one place.  Therefore, the cooker should be moveable to focus it in the direction of the sun.  

A site that describes a way in which to reduce movement during cooking  This site shows how a cooker can be left for long periods of time without the need to continuously move it to face the sun.

Thinking about (3)
    Start small unless you know what you are doing.  When adding materials together the cooker can become heavy.  Once you know your materials better and the stability of the design you use you can determine how large you want to make your cooker.  Roasting marshmellows and cooking a chicken will involve different amounts of light and therefore different sizes of cookers.  

Simple construction techniques Great site for cheap ways to make a cooker.  This site has a design for using a winebox which is one of the simplest and cheapest ways to create a solar cooker.

Thinking about (4)
    One option is to hold the food using a stick but this may get tiring.  Having an arm that extends over the focal point that is moveable to allow for different sized items is a good possibility.  Another is to have a bar that is attached at both ends.  This may be more feasible.

Great site involving the different materials involved This site goes through set by step how to make a parabolic solar cooker including the materials and how to put the layers of the parabola together.

Thinking about (5)
    The cost of making a solar cooker can vary greatly.  The cheapest way is to make it out of basic materials such as a wine box (also linked under thinking about (3)).  This would require a wine box, some scissors or exacto knife, some paper to give the ridges a little more stability, and a reflective surface (foil).  The box can be picked up free at a grocery store or liquor store and the other materials shouldn't cost more than a few dollars.  More costly cookers can be made or even bought (see the last section).  Of course, the better a cooker is made the better it will work but it is likely to be more expensive to make or the materials will be harder to get ahold of.

Cooking

Depending on how you want to cook your food, a perfect focal point may not be what you want (YEAH! you don't have to be perfect with your construction).  If the focal point is more diffuse then you can cook over a larger area.  If your focal point is very accurate then that one point will get very hot.  So, toss some food on a stick or grab a pan (the darker the better) and start cooking.



Additional LINKS

EcoBusinessLinks An international organization that has a strong focus on the use of solar energy.

A great source of information Runs through some of the costs associated and different ways to tweek a parabolic solar cooker into more uses.

Another site for solar cooking created by another Peace Corps volunteer
This site runs through the main points of solar cooking with a focus on
West Africa.


Solar cooking in Nepal This site includes a manuel on making solar cookers and suggested local materials in Nepal.

Parabolic solar cooking in Ethiopia Site runs through making cookers in Ethiopa including specific projects.

Energy saving in Hawaii This site discusses the future of energy in Hawaii and the pros and cons of solar energy in Hawaiian homes.

a site that looks at the many aspects of solar use This site is a do-it-yourself site for creating a solar home

Not feeling the urge to make one?  then buy one

Here are some sites for buying solar cookers.  They may inspire a design for your own.

ClearDome SolarReflex Parabolic Cookers
   This site sells solar cookers of all shapes and sizes for different uses.  Prices range from $10 to $160.

materials for the more high tech cooker This is a website for alternative energy hobbies.  It contains materials for making parabolic solar cookers that can be used for more high tech cookers.

Created 2/21/2005
Updated 2/26/2005
Armeda VanDam