Cheap solar cookers

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Comment by Brian White on April 29, 2009 at 6:49am

http://www.instructables.com/id/Compound-solar-cooker/ I thought of it a few days ago and I haave not made one yet.
Perhaps it could be made as a panel cooker too? In theory, it should cook for longer than a normal panel cooker but as I said, I have not made one.
Anyone want to try? I think the big curve could be a 30 degree compound parabolic curve. (a parabola twisted 30 degrees INWARDS round its focus. and the wings of the long curve should lie paralell with the path of the sun to give 2 hours of cooking at a time. With full use of the sunlight that hits the long curve for that 2 hours!
Brian

Comment by Magnar on April 27, 2009 at 10:16pm

http://solarcookers.ning.com/photo/mini-solar-cooker-2?context=album&albumId=2312757%3AAlbum%3A1679.

Comment by Magnar on April 27, 2009 at 10:13pm

The smallest cooker can also be effective with good isolation. Check out this one:

I use it inside a bigger cooker, but it get a nice temperature all of its own as well.

Comment by Magnar on April 27, 2009 at 1:42pm

I came across a very informative article today as I was browsing my delicious book marks. Here it is: http://www.thefarm.org/charities/i4at/surv/solarbox.htm
To sum it up it says that the limiting factor in cheap solar cookers is the size of the cooker compared to the ammount of food you want to heat. May be it is evident, but if not it is really worth considering.
Other ideas are
- a foiled airspace is all that is necessary.
- The airspace between the walls can be very small.
- Shallower ovens cook better since they have less wall area through which to lose heat.

Magnar

Comment by Brian White on November 14, 2008 at 6:44am

Hi, I uploaded photos and I will organize them later.
What I made was nothing special to look at. The important thing is that it worked!
I have just won a prize for it on instructables.com in the hungry scientist competition.

Comment by Magnar on November 13, 2008 at 1:56pm

http://solarcookers.ning.com/photo/ground-cookers-9?context=album&albumId=2312757%3AAlbum%3A1040

Comment by Magnar on November 13, 2008 at 1:51pm

That explains very well what you mean with compound parabolic. I think that also is my favorite.
I have been using the name "deep conical parabolic" for the same model, and here is one example of that type as well:

Comment by Magnar on November 13, 2008 at 12:11am

Would be very interesting to see some photos of these cookers Brian.
Do you have a photo of your compound parabolic?

Comment by Brian White on November 12, 2008 at 3:06am

Really good idea to have this group, I think! I have made several cheap solar cookers.
One was a parabolic solar cooker, cob (clay sand and straw mixed together) provided the backing for the dish and I stuck kitchen foil onto the wet clay. I used my "mechanical mathematician" to get the parabolic shape. I was pretty happy with this solar cooker but it was too heavy to move so it only cooked for about an hour a day!
I also made a "compound parabolic" solar cooker on a clay mold. This was back in September and it was by far the best solar cooker that I made so far. In Canada in September it brought a 7 liter pot of water to the boil. Compound parabolic concentrates light to an area at and behind the focal point. The advantages over parabolic are that they do not have to be moved often (every couple of hours for mine!) , they do not have to be so accurately made and they do not need to be so accurately pointed. They could be made from "petals" cut to a template just like parabolic solar cookers. The difference between compound parabolic and parabolic?
Parabolic is like a flower fully open and compound parabolic is like the flower not quite fully open.
I think compound parabolic solar cookers similar to my first attempt will be very common in the near future. Brian