New Generation of Solar Devices with Trapped Sunlight
What a wonderful age we are living in! We hear about so many possibilities in the field of alternative energy. Scientists all over the world are thinking about alternatives to fossil fuel. On every scale be it large or small progress is being made. Here the researchers are inspired by the Greek legend Dionysius’ ear. Dionysius erected a cave. It was shaped like an ellipse. Dionysius’ purpose was to hear the words whispered by a prisoner in one of the foci of the cave. Some of the present day science day museums are following the same features where two people standing the extreme ends of a room can hear each other’s whisper. This feature motivated physicists Roberto De Luca and Aniello Fedullo, both of the University of Salerno in Italy, to design sunlight traps. They are using two elliptical mirrors, with one collecting sunlight and another (they named it zozzaroid) focusing sunlight back to the vertex of previous one and into the blackbody. Here they are using mirror for steam generation.
Their study was published in the European Journal of Physics. They have duplicated acoustical Dionysius’ ear for their sunlight trapping system. They have arranged two parabolic mirrors face-to-face. Sunlight first falls on the larger mirror and reflects to the smaller mirror placed a short distance away. Then the light from the smaller mirror reflects back. This reflected light is focused into the vertex of the larger mirror. This way they have locked up the sunlight into this small region. Now this light can be used for various purposes. The sunlight is stored in a blackbody, which consists of a cavity with perfectly reflecting inner walls.
De Luca shares his views, “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. For example, after having trapped sunlight in a cavity with perfectly reflecting inner walls, what we call a blackbody, one can think of heating water enclosed in a container placed inside the cavity itself. Other uses of this concept are also conceivable.”
This idea was first conceived by Paolantonio Zozzaro, a high school physics professor from the Province of Salerno. Zozzaro often wondered about the shape of the smaller mirror that can reflect all incident light rays to the vertex of the larger mirror. De Luca and Fedullo carried forward from this point. They investigated the feasibility of such a perfect sunlight trapping system, which was first envisioned by Zozzaro. With help of their computations, De Luca and Fedullo reached to the conclusion that the smaller mirror should have a specific elliptic or hyperbolic profile akin to Dionysius’ ear. Out of respect for Zozzaro they call this secondary mirror a “zozzaroid.” Their design focuses sunlight very effectively, so that it can be transferred to a blackbody with a rather small hole.
The scientists anticipate that the new sunlight collector could be useful for a variety of alternative energy applications. De Luca has scrutinized the likelihood of using the device to produce steam. The advantage of producing such steam is that it will be prepared without the need for a convection fluid. In the hollow cavity of the blackbody, he added a metal container into which water is pumped. In the course of conduction, heat is transported from the metal container to the water, which is transformed into superheated steam. Now this steam can be utilized for various purposes such as power generation. One of the valuable applications of this steam generation is that such a system might be able to transform sea water into drinking water using only solar energy.