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Let's go green! Build a Solar Powered Parabolic Cooker!

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Let's face it, energy is expensive. Gas, electricity, whatever. So why pay to cook your food? The challenge I gave myself, was to cook a hot dog, without spending any money at all. No electricity, no new materials, nothing. And, there are no negative side effects on the environment, resulting from my hot dog.

What I came up with was...the parabola. So by using the properties of parabolas, we're going to cook a hot dog. Essentially, we're using math to cook hot dogs :D

I believe I've just proven that I'm a nerd? Oh well, I'm in good company here.
 
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Step 1How it works

"A parabola can also be defined as locus of points in a plane which are equidistant from a given point (the focus) and a given line (the directrix)."

The way it applies to us, is that the light that hits the parabola, will reflect back to one intersection point. That intersection point is called the point of focus. By placing the hot dog in the point of focus, all of the sun's rays that hit anywhere in the cooker, will reflect onto the hot dog...thus cooking it.

Click here to see how the light reflects

By the way...the shape of the entire cooker is a parabolic trough.
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143 comments
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Sep 13, 2010. 4:56 AMBlofish says:
(removed by author or community request)
Apr 25, 2012. 8:02 PMjblover says:
y r u jeulos srry me dont know how ton spell
Jan 16, 2009. 6:08 AMjustin1h6 says:
I am making it my project for the science fair
Apr 25, 2012. 7:58 PMjblover says:
me 2 but got a da** F
Dec 1, 2009. 9:24 AMmclovin808 says:
how long did it take you to cook the hotdog
Apr 23, 2012. 5:52 PMjblover says:
u should ry or my guess 30 min
Jul 30, 2007. 4:37 PMBrennn10 says:
MMMMMMMMMMM
Apr 20, 2012. 12:38 PMjblover says:
that does not look good

(>>>)
Jan 8, 2011. 7:56 PM_Scratch_ says:
subscribed.
I made this, and cooked a wiener, i also took a old meat thermometer and put it at the focus point of the oven, which i accidentally made sideways, so its like a big, curvy rectangle, and i got to 175 degrees Fahrenheit, when i cooked the wiener, it only got to 135 about unfortunately
Dec 2, 2010. 3:19 AMEarths_hope says:
Exellent. Subscription time.
Jun 14, 2009. 1:14 PMknektek says:
this idea is stupid but if you had dismantled a calculator and took the solar panel out of it and used that to make a circuit of the solar panel and something that provides heat, and then attatched that to the cooker, will it cook faster? (i think that the solar panel won't give out enough electricity to power the heat source).
Oct 26, 2009. 6:19 PMdasgemuse says:
the solar panels in a calculator dont put out anywhere near enought voltage to cook with or let alone put out any noticable heat. besides, the panel would have to be connected to a battery, then to the heat source. solar panels slowlycharge batteries, they dont usually directly power things
Sep 30, 2010. 11:49 PMmerseyless says:
a solar panel acts as a power source. not as a battery charger
Nov 1, 2010. 12:50 AMbeehard44 says:
yeah, but they use solar panels to power a battery charger to charge a battery and the end user (the machine or electronic gadget) gets the power from the batteries, not the solar panels.
Nov 2, 2010. 3:12 AMnutsandbolts_64 says:
I wonder what would happen if a battery powered a solar panel in the dark (with no diodes or anything to keep the flow in one direction). That would be the dumbest thing ever.
Sep 14, 2010. 9:18 AMzoltzerino says:
Can you provide an equation for the parabola. out of curiosity, would it come in the form Y = Xsqrd + a?
Sep 13, 2010. 4:53 AMBlofish says:
This may sound silly, bit I have to ask. If the sides dont provide any reflection, what is the main purpose to covering them in reflective material ?
Sep 13, 2010. 4:47 AMBlofish says:
Thanks for your work and insight!
Nov 6, 2009. 8:50 AMWerdnaN says:
 What would I need to do to make it on a larger scale?
Sep 2, 2010. 7:23 PMquantumkittty says:
MASS PRODUCTION >:( jk XD you would only need more of it, and proper calculation.
Sep 2, 2010. 7:22 PMquantumkittty says:
HELL YEAH FOR QUADRATICS AND CONICS!!
Mar 8, 2010. 9:00 PMmatt392 says:
Great Instructable - very innovative use of simple materials.
Jul 27, 2009. 4:25 AMQwertyuioLP says:
Could you modify this to follow the sun? It is possilble...
Sep 30, 2009. 2:40 PMcowscankill says:
If you attached it to a clock's motor somehow :D
Jul 18, 2007. 8:34 PMCameronSS says:
Have you already made a parabolic one? if not, two simple options: 1) use a yardstick to draw a graph on the sides and graph a parabola, or 2) shine a flashlight sideways and trace the beam. I love the power of the sun. We once had (possibly still do) two reflectors from searchlights. It you aimed it at the sun, a piece of paper instantly burst into flame at the focus. I also singed clean through an oven mitt with it.
Jun 3, 2009. 11:05 AMextrordinary1 says:
What size were your reflectors and were they parabola's or concave? I had an 8 ft. carbon arc search light I built with an 8 ft. satelite dish I covered with mylar. It was 9 sections bolted together, which made it easy to disassemble it and cover it with spray on glue and add the mylar reflector to it, then reassemble it. It was pretty intense light. I first used a 5 kW generator to power it up. Later I found a bigger generator at 50 kW. Sold it to some advertisement agency later on.
Jun 3, 2009. 1:22 PMextrordinary1 says:
There are two types of parabola's I am aware of, concave, and compound which is deeper, and tracks the sun up to 3-4 hours without movement. Compound's are typically used in flashlights. Some modern searchlights now use compound parabola's where the older ones used concave dishes with long focal lengths. That is why I was asking about the parablola or concave shape.
Parabola's are usually deeper than plain concave reflectors, like satelite dishes are just concave parabola's, with longer focal lengths. There is a difference. I call satelite dishes, old search lights, concave shapes, and parabola's have two different shapes, deeper than concave dish reflectors with very long focal lengths, where the parablola has a short focal length.

I'm not disputing it is concave or not, I hope you can see the point I am trying to convey in my question. My satelite dish search light and older search lights that used dish reflectors, were concaves with very long focal lengths compared to true parabola's that have very short focal lengths like flashlights, headlights, modern search lights... I'm writing you right now using a parabola dish with a short focal length concentrating my wifi signal to my antenna just an inch from the center of the reflector, I made from a link on here at Instructables. Thus keeping my focal point very short. See what I am trying to say? Pretty soon I will add a satelite dish reflecting my signal to the parabola to gain even more signal strength to continue running the wifi at full potential at 48 Mbps speeds. Right now I am only getting enough signal to hit 18 Mbps speeds. I don't dispute parabola's are concave, simply asking what kind of parabola are you using in your search light?
Jun 3, 2009. 1:37 PMextrordinary1 says:
BTW, I am 2 blocks from my wifi free source. Before I got the larger antenna and made the parabolic dish, I was only getting about an average of 43% signal strength, when weather conditions allowed it. Now I am getting 79% signal strength, and it is always on now, not tempermental to weather. A storm came through last night and I never lost signal. My cable modem has been taken out by lightning before, so I disconnect it and run wifi, especially when I want to use higher download and upload speeds compared to my cable at only 1.5 Mbps speed. At minimum, my speed tests have doubled compared to my cable. They have gone much faster too.
Jul 19, 2007. 3:44 PMCameronSS says:
Fancy!
Jul 19, 2007. 6:28 PMCameronSS says:
Nice stencils! Does it cook better with a parabola?

Also, in Step 1, you link to this image. I attached a modified version that better illustrates the reflection. If you want to use it, feel free.
Dec 13, 2007. 11:36 AMnagutron says:
Nice. I just added a similar image to the Wikipedia entry on Parabolas. It actually looks like we worked off the same base SVG!

Here's my caption on that image: "Parabolic curve showing arbitrary line (L), focus (F), and vertex (V). L is an arbitrary line perpendicular to the axis of symmetry and opposite the focus of the parabola from the vertex (i.e. farther from V than from F.) The length of any line F - Pn - Qn is the same. This is similar to saying that a parabola is an ellipse, but with one focal point at infinity."
Apr 2, 2008. 4:27 PMRiddleOfSphinx says:
I can just see "roughrider" 's head exploding now...lmao.
Aug 26, 2007. 6:36 PMgaiatechnician says:
You do not need any math to construct a parabola! If you have a vertical post going through point f and a horisontal swing arm attached on top of the post reaching out to point P3 and a slidable vertical arm coming down from Q3, all you do is attach a piece of string from f to p3! (through a hole3 in the bottom of vertical slider q3) . Keep the string taut and your slider pottom will touch every point on the parabola as you pull it in from Q3 towards the pole at the centre! Thats how I made my parabolic solar cooker. (Currently on utube). The problem with math is it is scary stuff. You can make a parabolic cooker (a big one) with no math at all! Do not be afraid!
Jun 5, 2008. 7:59 PMdawnmathmom says:
actually gaia, what you just described is a semicircle, not a parabolic section by definition a parabola is the collection of points which are equidistant from the focus AND the directrix
Jun 6, 2008. 12:14 PMgaiatechnician says:
Nope, you are not correct. I made 2 and they were definitely not semicircles. they were parabolic dishes. I have videos about the "mechanical mathematian" on utube. I redesigned a known method for making parabolas on paper (with string and a setsquare) so that it could be used in 3 dimensions.
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Author:Weissensteinburg
I enjoy photography, horticulture and carpentry, and am almost always doing something relating to of those things. Feel free to send me a PM for whatever reason.