1. With a parabolic mirror. (It requires particularly accurate pointing to the sun, which greatly complicates the design. Accordingly, it reduces reliability.)
2. With a cylindrical reflector (A little easier, but still difficult to position)
3. Ordinary, flat. (Simple. Reliable. But low efficiency)
And yet, as a "supporter of the advantages of cast-iron pans over Teflon and ceramic", I came to the conclusion that "the smaller the mechanism, the longer it will last." Therefore - flat, ordinary.
In his spare time, he was considering the option of increasing efficiency. A burnt quartz lamp caught my eye. (In shape - like an ordinary luminescent, only transparent, without a phosphor).
And if you cut the cap. (I think it’s not difficult to make an engraver with a diamond disk. At least all the “beer glasses” I have in the garage and in the basement are former wine bottles.)))))). So, verified. It works))))) Get a long glass tube. If you place inside the copper (normal, for heating) previously blackened, and seal the ends. We get a “greenhouse” that does not lose transparency over time. If there are a lot of such tubes in a row, with an interval of ... 1 cm (between the walls), parallelized, and put the entire structure in a box insulated with, say, glass wool under the foil, then such a battery can be aimed at an angle of 45 degrees to the south, and the efficiency will be the same throughout the daylight hours, because each tube will be illuminated in any position of the sun. And you can also place below this next, second, "in a checkerboard pattern." Increase the efficiency of a unit of area ....
The tube can be cut from fluorescent lamps, washing the kercher with a phosphor then. (I know, I know about the harmfulness)))))
Wat, what do you think? Are there any pitfalls in this design? And then I have not done this yet, we can not know what ....