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A Brief History
{{topic header| Allart-everest.jpg | Parabolic solar cookers }}
Parabolic designs have been used for centuries. The idea to concentrate light using curved mirrors was developed by the Greeks, Aztecs, Incas, Romans and Chinese. The Incas used bronze and gold for their mirrors and they built structures that were several stories high. This technology seems to have appeared around the same time for each of the civilizations.


There are many designs and models for parabolic solar cookers.   Some are made with locally gathered scrap materials while others are manufactured using highly machined, durable but more expensive materials. Here are links to a number of parabolic solar cooker designs.
A parabolic solar cooker is essentially a solar thermal collector used to cook food or pasteurize water.  Parabolic designs have been used for centuries. The idea to concentrate light using curved mirrors was developed by the Greeks, Aztecs, Incas, Romans and Chinese. The Incas used bronze and gold for their mirrors and they built structures that were several stories high. This technology seems to have appeared around the same time for each of the civilizations.


http://solarcooking.org/plans/
There are many designs and models for parabolic solar cookers.  Some are made with locally gathered scrap materials while others are manufactured using highly machined, durable but more expensive materials. Here are links to and photos of a number of parabolic solar cooker designs.


http://www.appropedia.org/Aleiha's_parabolic_solar_cooker
<gallery caption="Some Parabolic Solar Cookers" widths="200px" heights="200px">
Image:Grilling_meat_with_parabolic_solar_cooker.jpg|Fig1: Grilling meat with Parabolic Solar Cooker
Image:PICT0163.JPG|FIG 2:  Boiling water with an aluminum foil covered umbrella
Image:Allart-everest.jpg|Fig 3: Boiling water in the Himalayas
Image:Sun_cook.jpg| Fig 4: [[Sunbrella]]
Image:Stadium_Light_Reflector-Wash_Basin-Solar_Thermal_Water_Pasteurizer.jpg|Fig 5: [[Stadium Light Solar Cookers]]
Image:Setting_up_solar_heater_SCRAP.jpg|Fig 6: [[SCRAP Humboldt solar wax melter with 3D printed molds]]
Image:PCSC_-_low_setting_front.jpg|Fig 7: [[Papasan Chair Solar Cooker]]
Image:Finished_basket_solarcooker.jpg|Fig 8: [[Parabolic basket and tin can solar cooker]]
Image:Aleiha_dish.jpg|Fig 9: [[Aleiha's parabolic solar cooker]]
Image:305_class_democ.jpg| Fig 10: Some parabolic solar cookers from [[Engr305_Appropriate_Technology_Projects|Humboldt State University]]
</gallery>


http://www.appropedia.org/Parabolic_Basket_Solar_Cooker
== Danger from concentrated sunlight ==
A parabolic cooker concentrates sunlight. Ordinary sunlight is already dangerous (if the sun is viewed directly without protection) so concentrated sunlight can be much more so. (There is a story that someone in the USA damaged their eyes in this way.{{fact}})
 
The larger the parabola, the greater the danger.
 
Ways of reducing the danger include:
* Safety rules.<ref>E.g. [http://home.germany.net/100-441770/amsi-safety.html Safety Rules] (from the AMSI Solar Cooker Project)</ref>
* Design. Note that these mostly reduce the danger rather than eliminate it:
** Putting the focal point inside the parabola (deep dish focus), so someone would have to put their head inside to expose themselves to danger. (There is still a danger if someone unwisely checks a problem or tries to do maintenance while the parabola is pointed towards the sun, or if children are playing.)
** Using a physical barrier to prevent people going near the danger point.
** A table to protect the cook from burns and dazzles.<ref>http://solarcooking.org/images/gallery-para.htm Parabolic  Cookers] (The Solar Cooking Archive)</ref> (How does this work? It obviously can't block too much, or it will block the sun from the doing its work.)
** Keeping the parabola small.
** Designing the parabola to avoid a small sharp focal point. This requires that the cooking vessel have a relatively large surface area to catch the reflected rays. This would make it more likely for someone to be struck by the focused rays, but less damaging if it actually happened.<ref>This is just my ([[User:Chriswaterguy|Chriswaterguy]]'s) idea. When testing the parabola, it should not create an intense bright spot, but rather a slightly diffuse bright spot (but still significantly smaller than the smallest cooking vessel which will be used).</ref>
** Maximizing the efficiency of absorption by the cooking vessel (it would be expected that making it matt black is the most important thing)
** Four design methods to improve saftey are described at [[Wikia:Solarcooking:Satellite dish]].
 
The risk can be reduced but not eliminated. Other solar cooker designs have much less risk, and are probably a better option in situations where they can provide enough heat.{{fact}} Alternatively, [[integrated cooking]] and [[improved cookstoves]] with fuels from waste biomass may be safer options which use only modest amounts of resources.
 
Are there other solar cooker designs that can provide comparable high levels of heat but more safely, without being too expensive?{{sp}} I made a pseudo compound parabolic dish that concentrates the light down at the bottom of the dish and gives a bit longer cook time than a parabolic dish. It worked well.
I tested a winston w dish in software and that indicates MUCH longer cook time with good concentration amd a soft focus.
 
== Notes ==
<small><references/></small>
 
== See also ==
* [[Aleiha's parabolic solar cooker]]
* [[Parabolic Basket Solar Cooker - Engineering 305]]
* [[Compound parabolic concentrator]]
* [[Focus-balanced paraboloid]]
 
== External links ==
 
*[http://hubpages.com/hub/Concrete-Solar-concentrator Free and Easy DIY Parabolic Solar Concentrator Plan]
*[http://hubpages.com/hub/solar-reflector How to harness Sun's energy by making a solar concentrator]
* [http://solarcooking.org/plans/ Build a Solar Cooker] - plans at The Solar Cooking Archive (solarcooking.org).
* [http://solarcooking.org/unattendedparabolic.htm A Parabolic Solar Cooker for Unattended Cooking] at The Solar Cooking Archive.
* Paraboloid Solar Cooker: [http://pages.suddenlink.net/solarized Solar Cooker from recycled light fixture]
* [http://solarcooking.wikia.com/wiki/Parabolic_solar_reflectors Extensive descriptions of parabolic cookers] from Solarcooking.wikia.com.
 
 
{{Solar navbox}}
 
[[Category:Parabolic solar cookers| ]]
[[Category:Solar cooking]]

Revision as of 18:56, 3 April 2017

A parabolic solar cooker is essentially a solar thermal collector used to cook food or pasteurize water. Parabolic designs have been used for centuries. The idea to concentrate light using curved mirrors was developed by the Greeks, Aztecs, Incas, Romans and Chinese. The Incas used bronze and gold for their mirrors and they built structures that were several stories high. This technology seems to have appeared around the same time for each of the civilizations.

There are many designs and models for parabolic solar cookers. Some are made with locally gathered scrap materials while others are manufactured using highly machined, durable but more expensive materials. Here are links to and photos of a number of parabolic solar cooker designs.

Danger from concentrated sunlight

A parabolic cooker concentrates sunlight. Ordinary sunlight is already dangerous (if the sun is viewed directly without protection) so concentrated sunlight can be much more so. (There is a story that someone in the USA damaged their eyes in this way.[verification needed])

The larger the parabola, the greater the danger.

Ways of reducing the danger include:

  • Safety rules.[1]
  • Design. Note that these mostly reduce the danger rather than eliminate it:
    • Putting the focal point inside the parabola (deep dish focus), so someone would have to put their head inside to expose themselves to danger. (There is still a danger if someone unwisely checks a problem or tries to do maintenance while the parabola is pointed towards the sun, or if children are playing.)
    • Using a physical barrier to prevent people going near the danger point.
    • A table to protect the cook from burns and dazzles.[2] (How does this work? It obviously can't block too much, or it will block the sun from the doing its work.)
    • Keeping the parabola small.
    • Designing the parabola to avoid a small sharp focal point. This requires that the cooking vessel have a relatively large surface area to catch the reflected rays. This would make it more likely for someone to be struck by the focused rays, but less damaging if it actually happened.[3]
    • Maximizing the efficiency of absorption by the cooking vessel (it would be expected that making it matt black is the most important thing)
    • Four design methods to improve saftey are described at Wikia:Solarcooking:Satellite dish.

The risk can be reduced but not eliminated. Other solar cooker designs have much less risk, and are probably a better option in situations where they can provide enough heat.[verification needed] Alternatively, integrated cooking and improved cookstoves with fuels from waste biomass may be safer options which use only modest amounts of resources.

Are there other solar cooker designs that can provide comparable high levels of heat but more safely, without being too expensive?[expansion needed] I made a pseudo compound parabolic dish that concentrates the light down at the bottom of the dish and gives a bit longer cook time than a parabolic dish. It worked well. I tested a winston w dish in software and that indicates MUCH longer cook time with good concentration amd a soft focus.

Notes

  1. E.g. Safety Rules (from the AMSI Solar Cooker Project)
  2. http://solarcooking.org/images/gallery-para.htm Parabolic Cookers] (The Solar Cooking Archive)
  3. This is just my (Chriswaterguy's) idea. When testing the parabola, it should not create an intense bright spot, but rather a slightly diffuse bright spot (but still significantly smaller than the smallest cooking vessel which will be used).

See also

External links


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