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The main purpose of this compilation is to present all possible major designs and their variations so as to prevent the solar cooker designer from wasting time creating a design which has already been under the sun.
Concentrator cookers offer several advantages, including a mode of cooking very similar to day to day cooking. They come in many designs, classed according to whether they concentrate light from above or from below.
Solar cookers that concentrate light from below
Heat coming from below is most convenient for routine cooking, hence, many designers have focused on this type of cooker. There are many designs in this category, and they are classified on the basis of the type of reflectors used:
|Spherical solar reflectors|
Spherical mirrors are the simplest type of reflectors, very easy to build and use.
|Parabolic solar reflectors|
Parabolic geometry is well known, and it was probably the very first type of solar cooker. There are many designs for parabolic cookers. The reason for its popularity is the focus, which is much better and sharper than that of other types of reflectors. At the same time it is very sensitive to even a slight change in the position of the sun and hence the use of such reflectors means constant tracking.
|Fresnel solar reflectors|
Though the parabolic reflector was a perfect design, even good technicians, and even more the villagers, found it difficult to construct parabolic reflectors even with the help of templates. This is how the Fresnel reflectors gained importance.
|Cylindro-parabolic solar cookers|
This design was common in water heating, but was later tried out for cooking as well, so as to cook food in more vessels.
|Solar plane mirrors|
Plane mirrors, especially small pieces, yield very well to form various shapes, be it parabola, or cylindrical configurations.
Solar cookers that concentrate light from above
In this type of solar cooker, the light is concentrated from above. Though this approach is not the most efficient for cooking, there are several old designs and many new designs that have used this method. One of the most interesting and popular design in this category is the CooKit created by Professor Roger Bernard of France.
These cookers use one or more lenses (often a fresnel lens) to concentrate light instead of reflectors.
|Solar panel cookers
Simple, cheap, effective - most panel cookers are just a packet of interconnected reflectors. They unfold into a small bracket of reflectors around a central space where a cooking vessel sits in a transparent container of a heat resistant plastic. The simple cooker works well and is one of the most popular solar cookers on the planet.
|Solar funnel cookers
The funnel cooker has several advantages: it is simple to construct, and also store, and there is hardly any wastage of sheet. Supporting the funnel may pose problem in the beginning but you can easily solve the problem with, for example, a small hole in the ground to hold the base of the funnel.
- For more details on this topic, see Solar concentrators that concentrate light from above.
Solar box cookers
Box cookers are another group of old but popular solar cookers. The very first box cooker design was probably that of Nicholas de Saussure (1740-1799). It was simply an insulated box with glazing; this design forms the basis of all present designs of box-type cookers including Warenham’s (1995) ‘Sunstove’.
The box cookers presented here are classified on the basis of the presence or absence of reflectors, i.e., those without or with mirrors boosters.
See also Principles of Solar Box Cooker Design.
|Box cookers without reflectors|
One of the first cooker types designed on this planet. They are still on the scene.
|Box cookers with reflectors|
The Box cooker work well, but to improve the performance reflector boosters are added. Further classification of this type of cooker is based on number of reflectors.
- For more details on this topic, see Solar box cookers.
Indirect cookers generally use water or oil for heating and storing energy, and then use the resulting energy to cook the food. The water is heated by direct solar radiation through, for example, a cylindro-parabolic concentrator. This category includes 'chemical' cookers, biogas digesters, and solar hot water heaters, to name a few.
- For more details on this topic, see Indirect solar cookers.
Selecting the best design
Evaluation of cookers
See also Testing.
Suggested criteria for evaluation:
Ease of use
This has to be the primary criterion. No matter how good a design is in other respects, if it is difficult to use it will not succeed.
Capacity can be measured by the volume of food that can be cooked at one time, or by the mass of that food.
Power measures the amount of heat the cooker can produce in a specified time. Power may be measured in watts, or in Btu per second, or kilogram-calories per second. Maximum power depends on the angle of the sun, the ambient temperature, wind speed, air clarity and other factors that should be specified in describing the cooking power. This is the criterion that allows us to identify regions of the world where a particular design is appropriate.
Maximum temperature achieved
In addition to cooking power, the maximum temperature achievable should be defined. This also will depend on angle of the sun, ambient air temperature, wind speed and air clarity. Since different foods require different cooking temperatures, it is important to identify this criterion as well as cooking power.
Cost of materials
Since it is often the case that solar cookers will be used by the poor, cost is an extremely important criterion. Even minor differences in cost can make a significant difference in comparisons of designs.
Availability of materials
Even very low cost materials, such as the shiny wrapping paper that is discarded in developed countries, may be difficult to obtain in developing countries. Indigenous materials in a given location may be important benefits to the overall design.
Ease of construction
It is desirable that solar cookers be assembled by local unskilled labor in order to save cost and reduce training requirements.
Cookers should be able to fold in some way to make them more compact for storage and shipping. They should be light in weight.
Cookers should last a long time without need for repair. Reflective surfaces should not require frequent cleaning.
Cooker temperature should be moderate, never burn food or cause smoke or fire, pots should have cool handles and be stable against spills, etc. Protection of children should be considered in the overall design.
Designs should not infringe on any patented technologies without proper licensing. "Open source" implies that the design is unencumbered and released under the GNU free documentation license. ( Author totally agree with the above suggestions. With reference to 'cooking Power, lot of thought has gone into and group of International experts led by Prof Paul Funk have formulated detailed procedure for testing performance of the solar cookers. The test procedure has been accepted by American Department of Agriculture and termed as S 580. Author wishes to have email IDs of contributors to this page, so that he can continue useful dialog with them, alternately they can write directly to Author, at :- firstname.lastname@example.org)
- See Recommendations
Solar cookers are here to stay, or to put it in the other way, if we have to preserve our planet then each and every one of us has to use one or the other type of solar gadget, be it a cooker, a solar water heater, or solar photovoltaic panel.
- See References
- See Other links