Roberto de Luca and Aniello Fedullo from the University Salerno of Italy invented a new solar concentrating device they say is inspired by the Ear of Dionysus. According to the legends, Doinysus’s ear had an elliptical cave so he could hear even the weakest whispers of a prisoner in one of the cave’s foci.
The Sunlight Trap, as they have called it, faces two parabolic mirrors. The light coming from the Sun falls on the larger parabolic mirror and reflects to the smaller mirror (a “zozzaroid”). From there, it is reflected back onto the larger mirror, but focused in the middle of it, trapped inside a small dark space – the black body, or the accumulator. “Through a sunlight trap system, solar radiation is first concentrated in a small region of space and then sent into a blackbody, where it can be stored (not for an arbitrary long time, though) for a variety of uses,” De Luca told physorg.com.
Several applications can derive from this invention. The simplest to imagine is that the small black space accumulating heat could be used to boil water, create steam, and spin a turbine to produce electricity. Other uses could be water desalination, water heating or anything you could imagine that you could use that heat for.
Focused sunlight is already being seen as one of the solutions to the energy crisis, and solar concentrators are beginning to speed up their development because they’re low tech, simple to build and cheaper to use than the momentarily underdeveloped photovoltaics.
Technically an elliptical secondary mirror (or a hyperbolic one before the primary focus) will make a better final focus than a parabolic secondary mirror. Whether the improvement is worth dealing with the extra eccentricity variable or not depends on tolerances throughout the system.