# Kyoto trough solar cooker mimics a parabolic dish without a thousand cuts!

## Step 1: Concentrating sunlight with 2 troughs (why it works)

You can concentrate sunlight to a point of light as shown by a Swedish guy over 30 years ago!
Here is one of his videos of how it works.
I want to solar cook so I do not want a point of light. Instead I want the light to focus on the place where my cooking pot will be for 2 hours. How can I do it? First thing is to make a compound trough. This is easy. You just make a parabolic trough and twist its sides inwards. If you twist both sides inwards by 15 degrees each, you have a 30 degree "acceptance angle" . If you allign it with the suns path, and let the sun shine over it, for 2 hours, all the light from both sides will fall at or below the focus of the dish.
So there is some concentration!
So put your pot here. But the trough is wider than your pot! so the next stage is to concentrate that light a bit more. This is where the wings come in. They are parabolas too and they have a focus on the front of the pot and a focus on the back of the pot.
As long of their angle of rotation is at right angles to the angle of rotation to the first trough, they will not affect that rule "at or below the focal line" when the light arrives under it but it will concentrate the light towards the center of the trough! (I give these parabolas a little twist inwards too to do the at or below thing and spread the light over the pot a bit more).
bovineboy2 years ago
Are you sure these aren't pictures of the UFO that crashed at Roswell? :)
macrumpton5 years ago
Here is a related idea that I came up with this last week when I was trying to come up with an easy way to make a parabolic collector. I think the folded up sections might perform similarly to the secondary reflector in this instructible. The best part of my design is that it is made of a single flat sheet with no cuts and you can change the focal length by changing how much you bend the end flaps towards the center. I have not tested it at all, as it has been cloudy all day, but it seems to work concentrating a light bulbs light pretty well (it also makes a pretty good cheap reflector for DIY floodlights). To make cardboard take the curve better you can paint one side of it with some latex paint. When the paint dries it will shrink and the cardboard will curve towards that side.
3 years ago
I think you are onto something with your design. I am also working on a CST that the average homeowner can afford. What is the material you are holding and where do I get it? scottscontracting@gmail.com.

I will be posting information on my design and resources at: http://stlouisrenewableenergy.blogspot.com

Keep up the Green and Sustainable Designs. The way the Politicians in office are going it will be up to Jane and Joe Citizens to make this a pollution free world. And once more people are creating True Green Energy that does not have harmful residues such as nuclear radio active waste and harmful exhausts from Oil, Coal, and Natural Gas.

We will remove the Grip that the Fossil Fuel Companies have on our Elected Leaders from their campaign donations- find out for yourself and http://opensecrets.org and you too will have an "a-hah" moment on why your elected leaders are voting the way they are.

My best to all, Green Me UP-Scotty
3 years ago
I just used some spray glue to laminate some aluminum foil onto some card stock, but for a larger one I would probably use some coroplast (fluted Polypropylene) which is like plastic corrugated cardboard.
gaiatechnician (author)  macrumpton5 years ago
You can do like I did with one of my simple experiments. Lay it on the ground with an orange or red table tennis ball on it in the middle. Then approach it looking down. Your eye is the sun, the reflection of the ball coresponds (more or less) with the area of the reflector that will usefully reflect light onto the cooking pot. If I learn art of illusion a bit better, I might be able to model it there too. (It has ways of virtually twisting flat sheets and it probably can fairly accurately mimic what you did). Brian Until then, the tennis ball will give you an indication of how good your idea is. Brian
Idonet5 years ago
And here - you don't anything to say?  ;-)
macrumpton5 years ago
I think this idea has a lot of potential, especially if it can be incorporated into an exterior wall or roof. It seems like having the secondary reflector movable could make up for the main reflector being stationary. Can I suggest that yyou check out the 3d modeling tool sketchup? It is very easy to learn and there is a free version that is quite capable and it has a huge helpful userbase as well as being able to export into many helpful formats.
gaiatechnician (author)  macrumpton5 years ago
Thanks for the sketchup advice. Do not be fooled by my crappy pics and video. Art of illusion can make great models and pics and videos. I tried everything else and it was the solution and the source of the kyoto trough idea. I use art of illusion because it is free, cross platform, (I use linux and probably some people in africa and india use linux too. And it can make videos from your model. Most important, the people on the art of illusion forums helped me big time. They did half the work on getting the file set up. (And it looked far better before I started messing with things). I do not think sketchup can do video. An important part of using art of illusion in design is placing a camera high in the sky where the sun should be and moving it. The size of pot reflection that the "sun" sees coresponds to how good your potential reflector will be. My aoi files are available for download on another instructable and they can be tweaked to look better and your solar cooker can be put right into the file (If you open it with art of illusion) to compare it to other solar cookers. Best of all the files are tiny! 17.8 kb contains all my art of illusion dishes, the kyoto trough, 2 cameras, (one that moves in an arc over 90 degrees) some cusp reflector shapes and a box cooker with light from below. I have not made any inspired discoverys but there is a way forward. I am not at all gifted at learning or using software. It would be awesome if others contributed to the art of illusion solar cooker test files. Some on the forums have suggested set up the camera as a pinhole camera and say it could even be set up to shine the seasons on a garden! See the shadows for march, or may, or october and plant accordingly! Landscape design could be altered forever! It still amazes me how much the suns light shines into different parts of my garden depending on the time of year. Some smart kid could program that into a 20 kb art of illusion file and change the world! Brian Brian
lemonie5 years ago
Good to see a build of this - have you had enough sun to collect some data w/ref temp / power etc?

L

(Need text under step 5 Why do 2 troughs work to concentrate light?)
gaiatechnician (author)  lemonie5 years ago
I did minimal tests. It was just proof of concept. It works. You start off with the light low down on the east side of the pot and high up on the west side of the pot. Over 2 hours, the light spot (or area) rises on the east to the top and lowers to the bottom on the west and that is what it is supposed to do. You can design it with hemisphere curves if you wish or winston w curve or a cusp curve to get different light concentration patterns on your cooking pot and different cook times. Now I am under big pressure to get back to work. People are going to have to wait (for months probably) or do tests themselves. 2 possibly 3 rock wall jobs require my attention and I do not want to lose them. So unfortunately you guys are on your own. Best of luck Sorry Brian
SolReka5 years ago
Compound parabolic cookers certainly are a lot easier to build than commercial accurate parabolic cookers. The advantage of CPCs - Compound Parabolic Cookers, is that you don't need to turn the cooker to point towards the sun as often as you would for a highly accurate parabola.

I love the simplicity of your design, it's a great way for people to learn about the wonderful world of solar cooking.

I offer similar cooker kits for under \$20. There are ebooks, parabolic templates, building materials, and solar cooker kits available.

http://www.solreka.com/solar-cookers.html

Regards
Sol