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# Can combined troughs replace parabolic dishes for amateur solar cooking? Answered

I have being doing limited testing of the combined trough shown below and it seems to work as expected. I used a 4ft by 8 ft piece of corrugated plastic for the big trough (too wide but I was reluctant to cut it). Compared to dishes, this was incredibly easy to make and actually gives more reliable concentration over a longer time period.

Would anyone like to try it on tiny demo scale? (I mean something tiny made with 1ft by 2 ft paper perhaps) see if you can make a panel cooker with the design as a template?

I think it will work with hemisphere curve, or parabolic curve, any curve or panel cooker shape that shines the light on a cooking vessel.
Key points. 1 The troughs must be curved in directions that are at right angles to each other.
2 the long primary collector trough must be in line with the path of the sun.
And thats basically it! The primary trough concentrates light in one plane and the secondary trough (the little wings round the red pot) concentrate it in the other plane.

I then tried to get software to show if it was any good and It seems to show that it would cook for significantly longer than a parabolic dish. But the software showed that it was not as good as I had hoped. From running the software (art of illusion) I came up with the kyoto trough as a possible solution.
The kyoto trough is a trough made by taking 2 halves of a parabolic trough and twisting them a little inwards roung the focus. This can focus all the light between the focal line and the bottom of the trough for a time period coresponding to the angle of twist. 15 degrees of twist coresponds to one hour. http://www.youtube.com/watch?v=uX9Z-nsUHiA. That is a really useful property because it confers reliability. The next part of the kyoto trough can just be an ordinary parabolic trough to do a final concentrationof the light onto the cooking pot. Well 2 small troughs to deal with 2 streams of light going towards the cooking pot from either side of the trough.
Are any mathematicians interested in resolving the troughs into a Kyoto Dish? which would give much longer cook times than a parabolic dish.

Brian

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## Discussions

I saw your idea, and liked it a lot. It looks effective and simple to build, and I really like your work with Art of Illusion.

I'm no mathemetician, though, and would also love to see a lot more ideas compared. To further this effort, I created a group called Solar Cooking and put a lot of solar cooker instructables into it.

Groups features are still be developed, but perhaps some good discussions can occur there.

I finally made a prototype. I got it finished at about 5pm and there were a bunch of high clouds but I thought what the heck, might as well do a quick test.
It has a 30 degree acceptance angle so good for 2 hours of cooking.
The thing I like about it is that it is big!
Probably easier to make than dishes too.

I had a bit of time today and I started on the initial work. I think I will go for the panel design from page 3 of my trough instructable first. (I can add the second big wing later). To bring the cooking pot forward a little bit (and give a longer focus, I will start out the dish with a cusp and have the cusp merge into the early part of the parabola. The easiest way to make the curve for a cusp is by unwinding string from a cylinder and keeping it taut. The curve that it traces is a cusp. I just have to use my material effectively so that the full width of the mylar is used. Brian

I could discuss parabolic reflectors with you, yet cookers are not an area I have delt with. The part I am missing as may be others, is what's the benefit of the kyoto design? Is it a predetermined cook time? I am a little confused. I would think the idea of a solar cooker was to get, as much energy transferred into the item for cooking purposes as possible. Is that not the goal?

. I think the idea is to give you more cooking time without physically having to re-aim the mirror. Ie, do away with the need for complicated tracking.

That's it. I tried to achieve it with my compound parabolic dish last year but I didn't get the 2 hours of full power. (As shown by art of illusion). I think that the trough will get the 2 hours of full power. I might do baked potatoes tomorrow in it. Brian

A parabolic dish concentrates the energy to a point but only fo a moment. It is great to be able to melt holes in the cooking pot but is it really that useful? As soon as the sun moves away from the perfect postition, its focus scatters up away above the focus and down under the focus. The idea of the trough is to bring that aspect under control. Lets enlarge the focus to be the same size as the cooking pot and try to contain the light on that area for the longest time possible. The trough has several objectives. It should be easier to make, it should have a longer cook time and it should be easier to use than a dish. I have made dishes. From flat sheet material, it is hard to do and no matter what, you will get wrinkles and folds in your reflective material. But if you make a trough from sheet material, there should be almost no folds. As a home made option, it should be better than a dish for most people. Brian

You need to build one of these. Theory may be interesting to some people, but finished projects that work (e.g.) tend to attract more interest.

L

My intention is to spread the idea. I made pulser pumps 20 years ago and they work still. It has not spread. I believe that putting a teaser on the web and getting other people to make them might have a better outcome. Someone could be the first in the world to make one! Nobody wants to make history? I AM surprised.

Why don't you want to be the first? Doesn't look hard, and you've got all the knowledge. To reiterate: theory may be interesting, but something done is usually more exciting. Look at this as an example, it doesn't really work as an idea only as a finished item?

L

I am not good at building things (appart from stone walls) and I also have to take time off work to test it. A 2 hour boiling test in the middle of the day costs me the whole day! Victoria is not such a good location for solar cooking. People in desert areas of the US are going to look at my results and give them the thumbs down even if the solar cooker is really good. Anyway, I have started one. Brian

When you get some results, the people in e.g. Texas will be able to look and say "imagine what I could get out of that here?" - best wishes! L