I lived in AZ north of tucson for awhile in the mountains, with this eccentric ex science teacher as a landlord.
Anyway he had this "wok" welded to a small pole with sand under it. he broke up a mirror and glued it to rocks, then with the sand you can direct the sunlight onto the bottom of the wok, and cook!!!
i did this in northern new mexico in the dead of winter on a sunny day. you need more heat, simply keep adding mirrors!!! it took me probably 4 times the mirrors in winter here as the fall in AZ, but it did work, and well.....
showed a friend this sight, so today he tells me he put aluminum foil on a small satiallight dish to see , put a thernomator at focal point and was supprised at getting 275 in just a few minutes . yes some one burned them selfives. tell a friend.
I dont have any... When I did it, it wasnt ideal. I straddled a grill over two stacks of cinder blocks, which didnt give me a perfect surface to direct the light at. It was still enough though. the mirrors were just pieces I broke up and glued to rocks, and then could then position in such a way the mirror reflected the sun to the pot. One of those tripods for camping would be really good for this I bet. Youd have more room for mirrors to.
the guy who showed me, had a pole, with a wok like is used for stir fries welded to the top.
The more mirrors the more heat. Im going to order a box of 100 mirrors from that link, and test it out more but i thought Id share.... perhaps with some work I can set it up to help distill water is what I was thinking, and to cook with in general. I like being frugal even when Im not going to save a ton of energy or money doing it. Im going to play around with baking bread with solar ovens this summer to.... but th mirror thing worked for me while it was cold, so its got a lot of promise for those willing to bother with a bunch of tiny mirrors.
on myth busters R they used a 5' dish lined with 1 inch mirrors it caught wood on fire almost instantly . they also polished brass shields and tried to lite a boat ablaze based on Archimedes of Syracuse