Friday, January 30, 2015
ecoaldea espiral de luz
http://www.featherytravels.com/2015/01/26/falling-down-the-rabbit-hole-life-in-the-woods-at-espiral-de-luz-samaipata-bolivia/
Making a Parabolic Reflector Out of a Flat Sheet
Making a Parabolic Reflector Out of a Flat Sheet
Li-Yan
Zhu (April 2002)
Introduction
The unattended parabolic solar cooker [1] requires an
imprecise parabolic reflector. Such a reflector can be molded or stamped in
quantities, much like a salad bowl or a baby wading pool. However before it is
commercially available, you can make one at home. The easiest way is to cut
and fold a flat sheet into a parabolic dish. Then glue a layer of aluminum
foil on its inner surface, for reflectivity. The flat sheet can be as cheap as
cardboard. However water resistant material, such as plastic or metal, will
last longer.
The reader should practice with a scaled-down (for example
1:4 or 1:5) model, using a piece of paper. If you find a parabolic reflector
too difficult, a funnel shaped reflector will be a good alternative. Detailed
instructions are given in [2]. However you will need a bigger hole at the
bottom of the funnel [1].
Layout
As a concrete example, I shall describe the layout of a
reflector with 130 mm focal length (f), and 800 mm diameter (D).
All dimensions can be scaled to make reflectors of other sizes. A square sheet
approximately 1000×1000 mm is needed. It may consist of one, two, or four
pieces (fig. 1). There should be no overlap between adjacent pieces.
Fig. 1 The flat sheet can consists of either one,
two, or four pieces
Draw four concentric circles, with radii shown in Table
1. It is OK if the largest circle is not completely contained in the sheet. If
the sheet consists of multiple pieces, the center of circles must be located on
the border of all pieces.
Divide the circles by 8 uniformly spaced diameters (22.5°
apart). Each circle should consist of 16 identical sectors. If the sheet
consists of multiple pieces, each border between the pieces must coincide with
one of the divisions (fig. 2).
Fig. 2 Drawing four centric circles and dividing each
into 16 sectors
On each circle, and symmetric to each division, mark an arc
whose length is shown in table 1 below. The values tabulated are the total
arc lengths, including both sides of the division. Since each arc spans
over a very small angle (less than 5°), it is practically indistinguishable
from its corresponding cord.
Table 1 Dimensions of the layout features
Connect, approximately along the radial direction, end
points of arcs just marked. Cut off area outside of the largest circle. The
wedges outlined by the connections (fig. 3) will not collect sunlight. They
will be either removed, or used as margins to connect adjacent paddles. Do not
cut along the radial connections as yet, instruction will be given later.
Fig. 3 Area which will reflect sunlight in a finished parabolic reflector
The paddles will be bent over the circles drawn earlier, to
create facets. The circles are shown in dashed lines in fig. 3. Bending over
an arc is not easy, unless the sheet material is very thin and elastic. With a
cardboard the bends will be over the corresponding cord instead.
Assembly
If the sheet consists of multiple pieces, they should be
jointed now at the inner circle. The best way is to duplicate the inner circle
on a single piece. Then attach each piece of the reflector on top of this
duplicate.
After bending and folding, the paddles should overlap in
such a manner that a paddle is above (or below) both of its neighbors.
Therefore a paddle should have either no margin, or two margins (one on each
side). Paddles with and without margins alternate circumferentially (fig. 4).
Normally, paddles with margins will be below paddles without margins.
Fig. 4 Margins are provided on both side on alternating paddles
Since the paddles are planar at and near the inner circle,
there is a transition between planar and overlapping regions. To avoid
interference in the transition zone, some clearance should be provided between
adjacent paddles near the inner circle. Extra width can be shaved off paddles
with and/or without the margins near the inner circle (fig. 4).
A hole approximately 5 mm in diameter should be drilled at
the tip of each wedge. These holes are too small to be shown on fig. 4. They
will make cutting easier.
The paddles can be jointed together by staples, nails,
adhesive, sewing, or other means. The optimal solution depends on the sheet
material, and availability/cost of the fasteners.
In a rare case where the flat sheet is very thick, the
paddles should abut with each other. No margin should be provided in this
case. Some clearance should be provided for the adhesive. In addition to
adhesive applied in the gap, adhesive tapes can also be applied on the inner
and outer surfaces to hold the paddles together. Of course, tapes applied on
the inner surface should be very thin so as not distort the reflecting surface.
It is generally advisable to attach one paddle at a time,
either clockwise or counter-clockwise. Attach each paddle from the outer
section first. Then proceed inward. Attach all sections of a paddle before
working on another paddle.
Reflective Foil
Unless your sheet is already reflective, a reflective foil
should be applied after the parabolic reflector takes shape. Aluminum foil for
ordinary kitchen use is ideal. A thicker (heavier gage) foil will be more
durable. Aluminized plastic film such as shiny food and beverage bags, or
gift-wrap, is acceptable but slightly less efficient and noticeably less
durable than aluminum foil.
Usually the foil is glued to the reflector. Most
water-based glue will do. This includes glue made of flour, rice, or starch.
To avoid wrinkles on the foil, the glue must be thin enough that it flows
easily.
It is easier to glue the foil on a flat sheet than on a
parabolic dish. However unless the sheet is very thin, the process of bending
the sheet will create wrinkles on the foil. Therefore it is best to apply the
foil after the dish is formed. By the way, sheet material that expands and
contracts significantly with humidity and temperature also tends to create
wrinkles on the foil. This is why cardboard is not an ideal sheet material.
The wrinkles reduce the efficiency. They also shorten the life of the foil.
The foil should be cut into trapezoids first. Two identical
trapezoids can be cut from a rectangle with very little waste (fig. 5). Try
with used newspaper first to determine the optimal width, length, and slope, as
it depends on the shape and size of your foil supply. Short slots may be cut
along edges of the trapezoid, so that the foil can overlap instead of wrinkle.
The trapezoids should cover all facets completely, except that the inner circle
will be covered by a circular foil at the end.
Fig. 5 a) Cutting two trapezoidal pieces out of a rectangular foil
b)
Cutting short slots along edges of each wedge
Coat the inner surface of a paddle thoroughly with glue.
However do not overuse glue if the sheet material (such as cardboard) may swell
when wet. Apply the foil, with the shinny side facing up. To avoid bubbles,
it is best to engage a small portion of the foil on the paddle at first. Keep
most of the foil in the air, free of glue. Then slowly extending the engaged
area by pushing over the foil. It is best to attach foil near its center line
(along its length) first. So that it will be obvious how much the foil should
bend and overlap near its edges. It is OK if excess glue smears over the
reflecting surface. The glue can be wiped off later.
It is best to overlap the foil slightly, so that no direct
sunlight will strike the sheet material. For the same reason, it is best to
have a little extra length so that the foil can fold over the rim of the dish.
This prevents ultraviolet in the sunlight from damaging the reflector.
When the entire reflecting surface is covered by aluminum
foil, wipe the reflective surface gently with damp, clean cloth. Wash the
cloth frequently as needed. The wiping removes excess glue, flattens the foil,
and improves adhesion. Allow the glue to dry, which may take a few days if the
sheet material is permeable to water. Then wipe again with damp, clean cloth
to remove the remaining glue smear and smudge.
Caution:
Do
not work with reflective material in direct sunlight, as it may cause eye
injury. Keep your reflector indoors until it is completely assembled onto a
solar cooker.
References:
|
panelcookerreference :
http://solarcooking.wikia.com/wiki/CooKit
http://es.solarcooking.wikia.com/wiki/Fun-Panel
Thursday, January 08, 2015
gtteo con botellas
Un hecho inevitable es que el agua empieza a escasear y se está convirtiendo en uno de los recursos más preciados en algunas partes del mundo. Gran parte de todo ese agua que utilizamos, se emplea para el cultivo. Es por ello que hoy te mostramos una forma económica y sencilla a través del goteo solar. Se trata de un sistema de riego muy eficiente, sencillo y económico que puede ayudar a millones de agricultores en el mundo a lograr un aumento de la producción empleando, hasta 10 veces, menos agua.
Es cierto que existen sistemas de riego que son bastante eficientes, como el goteo convencional, pero no están al alcance de muchos agricultores en muchas partes del mundo, donde la pobreza se convierte en una supervivencia. Es por eso que te presentamos hoy el KondensKompressor, o goteo solar.
Con este sencillo invento serás capaz reducir el consumo de agua hasta diez veces
goteo_solar_1
Es una técnica de riego destinada a lograr el aprovechamiento máximo del agua, empleando a la energía solar como elemento motor del proceso del destilado y movimiento del agua. Además, con el sistema Kondenskompresor podrás utilizar agua salobre o de mar para el riego, ya que esta se transforma en agua dulce durante el proceso.
Veamos paso a paso cómo fabricar el sistema de goteo solar
goteo_solar_5
Necesitas una garrafa de agua de 5 litros y una botella de 1,5 litros, ambas de plástico, aunque también funcionan con el cristal si dispones del material adecuado para cortarlas. Tendrás que cortarle la base a la garrafa grande y la pequeña deberás cortarla por la mitad tal y como se ve en el dibujo.
Después pon la pequeña sobre la tierra, cerca de la planta, y después pon la otra sobre ella, más o menos centrada, de tal forma que puedas echar el agua sin tener que levantar la garrafa de 5 litros. Alrededor de la planta y del Kondenskompressor pondremos heno, hojas secas o paja, de tal forma que quede todo dispuesto como en la siguiente imagen:
goteo_solar_2
El funcionamiento es similar al de los destiladores solares
goteo_solar_6
Cuando los rayos del sol inciden sobre el Kondenskompressor, en su interior se desata un efecto invernadero, que al elevarse la temperatura del interior el agua del depósito se irá evaporando.
El agua se condensa en las paredes de la garrafa
goteo_solar_3
Cuando el Kondenskompresor permanece al sol, el agua está constantemente evaporándose, por lo que las gotas cada vez se hacen más grandes, hasta que empiezan a caer por las paredes de la garrafa hasta el suelo, humedeciéndolo por completo.
Si todos los agricultores instalaran este sencillo, práctico y económico sistema, no solo lo notarían sus bolsillos sino también el planeta entero, ya que conseguiríamos ahorrar cantidades incalculables de agua. Comparte este fabuloso sistema de riego con tus amigos, a fin de concienciar a la gente para ahorrar todo el agua que sea posible. Déjanos también un comentario en Facebook con tus impresiones sobre el Kondenskompressor.
Fuente: ecoinventos
Si te gustó compártelo:
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Enlace patrocinado
Artículos relacionados
Es cierto que existen sistemas de riego que son bastante eficientes, como el goteo convencional, pero no están al alcance de muchos agricultores en muchas partes del mundo, donde la pobreza se convierte en una supervivencia. Es por eso que te presentamos hoy el KondensKompressor, o goteo solar.
Con este sencillo invento serás capaz reducir el consumo de agua hasta diez veces
goteo_solar_1
Es una técnica de riego destinada a lograr el aprovechamiento máximo del agua, empleando a la energía solar como elemento motor del proceso del destilado y movimiento del agua. Además, con el sistema Kondenskompresor podrás utilizar agua salobre o de mar para el riego, ya que esta se transforma en agua dulce durante el proceso.
Veamos paso a paso cómo fabricar el sistema de goteo solar
goteo_solar_5
Necesitas una garrafa de agua de 5 litros y una botella de 1,5 litros, ambas de plástico, aunque también funcionan con el cristal si dispones del material adecuado para cortarlas. Tendrás que cortarle la base a la garrafa grande y la pequeña deberás cortarla por la mitad tal y como se ve en el dibujo.
Después pon la pequeña sobre la tierra, cerca de la planta, y después pon la otra sobre ella, más o menos centrada, de tal forma que puedas echar el agua sin tener que levantar la garrafa de 5 litros. Alrededor de la planta y del Kondenskompressor pondremos heno, hojas secas o paja, de tal forma que quede todo dispuesto como en la siguiente imagen:
goteo_solar_2
El funcionamiento es similar al de los destiladores solares
goteo_solar_6
Cuando los rayos del sol inciden sobre el Kondenskompressor, en su interior se desata un efecto invernadero, que al elevarse la temperatura del interior el agua del depósito se irá evaporando.
El agua se condensa en las paredes de la garrafa
goteo_solar_3
Cuando el Kondenskompresor permanece al sol, el agua está constantemente evaporándose, por lo que las gotas cada vez se hacen más grandes, hasta que empiezan a caer por las paredes de la garrafa hasta el suelo, humedeciéndolo por completo.
Si todos los agricultores instalaran este sencillo, práctico y económico sistema, no solo lo notarían sus bolsillos sino también el planeta entero, ya que conseguiríamos ahorrar cantidades incalculables de agua. Comparte este fabuloso sistema de riego con tus amigos, a fin de concienciar a la gente para ahorrar todo el agua que sea posible. Déjanos también un comentario en Facebook con tus impresiones sobre el Kondenskompressor.
Fuente: ecoinventos
Si te gustó compártelo:
Enlace patrocinado
Artículos relacionados
Sunday, January 04, 2015
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