A radiant energy collector for receiving rays of an incident flux from an external energy source throughout a range of acceptance angles extending to at least about twenty degrees away from opposite sides of a central axis of said collector and measured in a plane passing through said source and including said axis, said collector comprising:
- A. a concave reflector bowl having a reflective internal surface and a convex lens member secured to one another to provide an enclosed cavity between them, said reflector bowl and lens member each being arranged in a substantially symmetrical manner about said axis;
- B. an upright absorber mounted within said cavity, said absorber including a plurality of wing members extending laterally from said axis and toward the inner surfaces of the reflector bowl, said wing members having energy absorbing walls of substantial surface area defining opposite sides of the respective wing members, oriented substantially upright and defining confined fluid heating passages between them;
- C. said concave reflector bowl having a ratio of axial depth to width at its mouth of about 0.6 - about 0.7 to one, and being defined at least in part by a plurality of side wall segments arranged substantially symmetrically about said axis and forming generally polygonal figures with straight or gently curved sides as viewed in plan view or horizontal cross-sections, said side wall segments narrowing in width as they draw progressively nearer the bottom of the bowl, and, as viewed in vertical cross-section, extending downwardly from an upper portion of the bowl while curving inwardly towards said axis,
- D. said inwardly curving side wall segments, within a working portion of the reflector bowl viewed in vertical cross section, transitioning from upper side wall portions, which are substantially upright, to a more nearly horizontal orientation as said segments draw nearer to the bottom of the bowl and to said axis, the resultant transition including one or more arcuate intervals of such side wall segments which have been generated from at least one generating locus which is located above, and on the opposite side of said axis from, the position(s) of said interval or intervals;
- E. said lens member having an overall shape which is generally spherical and comprising a plurality of inwardly projecting prismatic elements which, as viewed in plan view, are distributed in one or more arrays in a working portion of the lens member extending about said axis;
- F. said prismatic elements, as viewed in vertical cross-section, having receiving and emitting surfaces which, within individual elements, diverge from one another, said emitting surfaces being generally planar, bi-directionally inclined surfaces, the angle of inclination of said emitting surfaces in at least one of said directions approaching within about twenty percent of, but being less than, the critical angle which will cause rays be to reflected by the emitting surfaces back through the lens when the radiation is incident upon the lens member at the maximum acceptance angle, said prismatic elements being oriented and positioned in said lens member for:
- (1) receiving on both sides of said axis the incident rays of said incoming flux which enter the lens member at varying angles of incidence within said predetermined range of acceptance angles;
- said acceptance angles being measured in, and said axis and rays being viewed along a line of sight perpendicular to, a plane including said axis and passing through said energy source;
- (2) emitting departing rays into said enclosed cavity and causing:
- (a) a first and portion of the flux, including a portion of the rays which enter the lens on the side of the axis farthest from the source to pass through the lens when viewed along a line of sight perpendicular to said plane, to pass through the lens member, to refract with both upward and sideward components of refraction toward adjacent side wall segments of the reflector and to impinge upon and reflect from said side wall segments at locations which are positioned laterally for impingement upon the absorber wing surfaces, and which are higher than would occur in the absence of the bi-directional inclination of said receiving and emitting surfaces of said prismatic elements and
- (b) a second portion of the flux, including a portion of the rays which entered the lens on the side of the axis nearest the source when viewed along a line of sight perpendicular to said plane, to pass directly from the lens to the absorber;
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- (3) for cooperating with said reflector and absorber for directing portions of said flux to opposite sides of the wing members;
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- G. said absorber wings extending sufficient distances outwardly from and both upwardly and downwardly in directions perpendicular and parallel to said axis, for intercepting substantially all or a major portion of the rays emitted by said prismatic element emitting surfaces as the angle of incidence of said flux varies throughout said range of acceptance angles, there being sufficient separation between the underside of the lens member and the top of the absorber for light emitted by the lens member on one side of the axis to pass over the top of the absorber to a surface of the reflector located on the other side of the axis when viewed from a position perpendicular to said plane;
- whereby said reflector bowl and lens member exert both horizontal and vertical control over the path of the rays emitted into said cavity toward said reflector and, with said absorber, promote retention of emitted and reflected rays within said cavity.