Fresnel solar reflectors

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#Redirect[[Fresnel solar cooker designs]]

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[[Category:Fresnel solar cooker designs]]

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{{Previous-Next|Parabolic reflectors|Cylindro-parabolic cookers}}

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Though the parabolic reflector was a perfect design, even good technicians, more so the villagers, found it difficult to construct parabolic reflectors even with the help of templates. This was how the Fresnel reflectors gained importance. The very first design in this category came from [[Volunteers in Technical Assistance]] (VITA) in 1961 . Three to four rings of masonite (hardboard like material) were cut from a 4’ x 4’ sheet. Aluminized polyester was stuck to this. After which the rings were nailed to specially notched wooden reapers to form a Fresnel concentrator. VITA provided a template of these materials as it was a do-it-yourself project (VITA 1971). The cooking pot was supported on a rod projecting from the center. Adjustments, once in 30 minutes were considered sufficient. Ease of construction and focusing characteristics made this design better than the regular parabolic reflector (VITA 1961). Professor Garg, an Indian designer (Garg et al 1978), suggests further improvements by making the reflector with five to six rings.

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Recently Mr. Ed Norman of Peru has taken keen interest in the VITA design and has revived it. I am yet to get the latest details from him as to the performance.

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[[Image:Solar-cooker-design-photo-_Vita_resnel1.jpg]]

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Mr [[Juan Urrutia Sanz]] of [[Spain]] has revived VITA cooker, and the photo shows his cooker in front of an imposing building of Madrid, Spain

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[[Image:IM000342.JPG|right|thumb|266px]]

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In a comparative study the VITA design emerged as a top model (Garg 1978). Attracted by the simplicity of the Fresnel geometry, Steenbleek developed an ingenious way of making Fresnel concentrator (strips of reflector materials, with the width determined by using a computer) were wound in concentric circles on a suitable support. Solar stalwarts like Edmondson (1981) claim that this design was a boon to solar designers. Reflectors of any size could be easily fabricated. The reviewer tried out this technique but encountered considerable difficulty in cutting and fixing strips.

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[[Image:Solar-cooker-design-steenbleek_type-Fig23.gif]]

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[[Image:Solar-cooker-design-Mullersfresnel01.jpg|thumb|200px|right]]Dr. [[Bernie Mueller]] of Germany who visited my site in March 2003, has directed me to his web site http://www.mueller-solartechnik.com. Some more interesting variation of Fresnel design. The photograph taken from his site gives good details. The linearly arranged Fresnel lens focuses light on to a pot kept at the focal point, about 50 cm away from the mirrors. The design is said to deliver ~300W power. The one which could deliver ~600 W is in the form of Cross says Mr. Muller. He recommends unit with glass mirrors. The standard cooker comes with an aluminium foil reflector.

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Fatangre's (1992) design is actually a box type design, wherein he incorporates a transparent Fresnel lens in the lid of the Gosh type box ( described later).

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Another interesting Fresnel arrangement has been described by Bob Culbertson,of US, in which an array of flat mirrors are lined up which focus the sun rays at the bottom. The configuration could be described with the help of forward and backward slashes.

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[[Image:Fresnel-box.jpg|200px|thumb|none|Bob Culbertson's Fresnel box design]]

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This configuration would work, but it may not be possible to divert the focused rays to the base of a pot, for this will be a line focus.

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Another new design of Fresnel lens was displayed at the recent Granada exhibition, a photo of which has been kindly sent by [[Tom Sponheim]]. Unfortunately, we don't have any further details on this cooker.

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[[Image:Fresnel_ring_concentrator_Granada_2006.jpg|center|400px]]

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~~{{Main|Compendium of~~ solar cooker designs}}

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{{Previous-Next|Parabolic reflectors|Cylindro-parabolic cookers}}

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[[Category:~~Compendium of~~ solar cooker designs]]

Changes: Fresnel solar reflectors

Revision as of 17:00, 24 April 2016

@@ Line 1: / Line 1: @@
+#Redirect[[Fresnel solar cooker designs]]
-{{Compendium header}}
+[[Category:Fresnel solar cooker designs]]
-{{Previous-Next|Parabolic reflectors|Cylindro-parabolic cookers}}
-{{Compendium TOC}}
-Though the parabolic reflector was a perfect design, even good technicians, more so the villagers, found it difficult to construct parabolic reflectors even with the help of templates. This was how the Fresnel reflectors gained importance. The very first design in this category came from [[Volunteers in Technical Assistance]] (VITA) in 1961 . Three to four rings of masonite (hardboard like material) were cut from a 4’ x 4’ sheet. Aluminized polyester was stuck to this. After which the rings were nailed to specially notched wooden reapers to form a Fresnel concentrator. VITA provided a template of these materials as it was a do-it-yourself project (VITA 1971). The cooking pot was supported on a rod projecting from the center. Adjustments, once in 30 minutes were considered sufficient. Ease of construction and focusing characteristics made this design better than the regular parabolic reflector (VITA 1961). Professor Garg, an Indian designer (Garg et al 1978), suggests further improvements by making the reflector with five to six rings.
-Recently Mr. Ed Norman of Peru has taken keen interest in the VITA design and has revived it. I am yet to get the latest details from him as to the performance.
-[[Image:Solar-cooker-design-photo-_Vita_resnel1.jpg]]
-Mr [[Juan Urrutia Sanz]] of [[Spain]] has revived VITA cooker, and the photo shows his cooker in front of an imposing building of Madrid, Spain
-[[Image:IM000342.JPG|right|thumb|266px]]
-In a comparative study the VITA design emerged as a top model (Garg 1978). Attracted by the simplicity of the Fresnel geometry, Steenbleek developed an ingenious way of making Fresnel concentrator (strips of reflector materials, with the width determined by using a computer) were wound in concentric circles on a suitable support. Solar stalwarts like Edmondson (1981) claim that this design was a boon to solar designers. Reflectors of any size could be easily fabricated. The reviewer tried out this technique but encountered considerable difficulty in cutting and fixing strips.
-[[Image:Solar-cooker-design-steenbleek_type-Fig23.gif]]
-[[Image:Solar-cooker-design-Mullersfresnel01.jpg|thumb|200px|right]]Dr. [[Bernie Mueller]] of Germany who visited my site in March 2003, has directed me to his web site http://www.mueller-solartechnik.com. Some more interesting variation of Fresnel design. The photograph taken from his site gives good details. The linearly arranged Fresnel lens focuses light on to a pot kept at the focal point, about 50 cm away from the mirrors. The design is said to deliver ~300W power. The one which could deliver ~600 W is in the form of Cross says Mr. Muller. He recommends unit with glass mirrors. The standard cooker comes with an aluminium foil reflector.
-Fatangre's (1992) design is actually a box type design, wherein he incorporates a transparent Fresnel lens in the lid of the Gosh type box ( described later).
-Another interesting Fresnel arrangement has been described by Bob Culbertson,of US, in which an array of flat mirrors are lined up which focus the sun rays at the bottom. The configuration could be described with the help of forward and backward slashes.
-[[Image:Fresnel-box.jpg|200px|thumb|none|Bob Culbertson's Fresnel box design]]
-This configuration would work, but it may not be possible to divert the focused rays to the base of a pot, for this will be a line focus.
-Another new design of Fresnel lens was displayed at the recent Granada exhibition, a photo of which has been kindly sent by [[Tom Sponheim]]. Unfortunately, we don't have any further details on this cooker.
-[[Image:Fresnel_ring_concentrator_Granada_2006.jpg|center|400px]]
-{{Main|Compendium of solar cooker designs}}
-{{Previous-Next|Parabolic reflectors|Cylindro-parabolic cookers}}
-[[Category:Compendium of solar cooker designs]]