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

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.
Remove these ads by Signing Up

## Step 1: How 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.

By the way...the shape of the entire cooker is a parabolic trough.

## Step 2: What you'll need

After rummaging around my house, this is what I used to build a cooker:

• Poster board
• Foam board
• Tin foil
• Plastic wrap (optional)
• two blocks (can be anything..shoes, wood..rolls of tape)
• Skewer
• Various cutting supplies
• Packing tape, and scotch tape.
• The attached stencil
• A nice sunny day.

 1-40 of 145 Next »
Blofish4 years ago
(removed by author or community request)
2 years ago
y r u jeulos srry me dont know how ton spell
2 years ago
No, you do not.
Blofish4 years ago
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 ?
2 years ago
@Blofish - Sides might not reflect much light BUT they will reflect heat. And keep a barrier from outside temps.

Awesome project. Thanks for sharing. :)
justin1h65 years ago
I am making it my project for the science fair
2 years ago
me 2 but got a da** F
mclovin8085 years ago
how long did it take you to cook the hotdog
2 years ago
u should ry or my guess 30 min
Brennn107 years ago
MMMMMMMMMMM
2 years ago
that does not look good

(>>>)
_Scratch_3 years ago
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
Earths_hope4 years ago
Exellent. Subscription time.
knektek5 years ago
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).
5 years ago
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
4 years ago
a solar panel acts as a power source. not as a battery charger
4 years ago
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.
4 years ago
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.
zoltzerino4 years ago
Can you provide an equation for the parabola. out of curiosity, would it come in the form Y = Xsqrd + a?
Blofish4 years ago
Thanks for your work and insight!
WerdnaN5 years ago
What would I need to do to make it on a larger scale?
4 years ago
MASS PRODUCTION >:( jk XD you would only need more of it, and proper calculation.
quantumkittty4 years ago
HELL YEAH FOR QUADRATICS AND CONICS!!
matt3924 years ago
Great Instructable - very innovative use of simple materials.
QwertyuioLP5 years ago
Could you modify this to follow the sun? It is possilble...
5 years ago
If you attached it to a clock's motor somehow :D
Weissensteinburg (author) 7 years ago
Thanks for pointing that out guys. I'll either amend this instructable to say so, or make it a real parabola. (or both). Of using other materials: As I said in the intro, a main goal of this was to only use stuff I had laying around. But I will add your ideas as suggestions for what you could use instead. Thanks again!
7 years ago
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.
5 years ago
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.
Weissensteinburg (author)  extrordinary15 years ago
Parabolas are concave.
5 years ago
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?
Weissensteinburg (author)  extrordinary15 years ago
I see, I thought you were implying that if it's concave, it's not a parabola.
5 years ago
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.
Weissensteinburg (author)  CameronSS7 years ago
I have made one..to make it easy, I'm attaching a parabola stencil to the ible, so you can just print it out, and cut.
7 years ago
Fancy!
Weissensteinburg (author)  CameronSS7 years ago
Ok, the instructable has been fixed. Let me know what you think.
7 years ago
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.
7 years ago
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!
Weissensteinburg (author)  gaiatechnician7 years ago
Who was afraid?
7 years ago
If parabola math was easy, lots of home made parabola solar cookers would be about. I do not see many. Thats why I use the mechanical alternative.
 1-40 of 145 Next »