Solar collector with conical elements

Abstract

A device for collecting radiant energy is disclosed in which a conical surface is formed so as to convergently reflect rays toward an elongate energy absorbing structure which is disposed along a central focal axis. The conical surface has a relatively high reflectivity (.rho.) coefficient while the outer surface of the energy absorbing structure has a relatively high absorbtivity (.alpha.) coefficient and also is formed of a material having a relatively high thermal conductivity (k) for efficiently transferring thermal energy by convection to a heat exchange fluid. In one embodiment the energy absorbing structure comprises a hollow tube which is coiled in a helix about the focal axis, with a transparent cover enclosing the helix. In another embodiment the absorbing structure comprises an open ended hollow enclosure containing a porous filler having a relatively high thermal conductivity (k). Another embodiment provides an enclosure which contains a plurality of cells creating a relatively large surface area for more efficiently transferring thermal energy by convection to the fluid, and in a further embodiment such cells are filled with porous filler. In still another embodiment a plurality of the conical surfaces are mounted within a housing facing a transparent panel, with means being provided to direct a fluid such as a gas into the housing and in heat exchange relationship with the energy absorbing structure associated with each conical surface.