Radiant energy concentration by optical total internal reflection

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reflection doubles the sensitivity to manufacturing error

RADIANT ENERGY CONCENTRATION BY over that of the present invention.

OPTICAL TOTAL INTERNAL REFLECTION

SUMMARY OF THE INVENTION

This is continuation, of application Ser. No. 83,467 5 It is a major object of the present invention to over filed Oct. 10, 1979, now abandoned. come the above described problems of and difficulties BACKGROUND OF THE INVENTION with the prior art, and to provide a means to collect and employ radiant energy in a very cost-effective and effi

This invention relates generally to radiant, particu cient manner, using a new basic tool whose uses include larly electromagnetic, energy concentration, redirec O the collection, concentration, redirection, and wave tion, and manipulation, and more particularly concerns length separation of radiant energy. apparatus and method for employing a transparent The present invention is basically characterized by means with elements thereof using Total Internal Re the use of a transparent means employing elements to flection (T.I.R.), alone or in conjunction with refrac redirect radiant energy by means of Total Internal Re tion; such elements acting in concert with purely refrac 15 flection alone, or in conjunction with refraction, such tive elements (as those in a Fresnel lens) and/or metal means positioned between the radiant energy source mirrors to redirect radiant energy to or from a predeter and a receiver. Each element redirects radiant energy mined zone or zones; such redirection having a prede upon a common target zone or zones, during the ener termined degree of concentration and/or chromatic gy's internal passage through the element. A properly dispersion. The zones have sources of light, as in pho 20 oriented ray enters through the entry face and strikes toillumination, or radiant energy receiving means for the reflective face, which redirects it toward the exit conversion of the energy to thermal, electric, chemical, face, the three faces comprising the active faces for that or mechanical forms. Alternatively, a further transpar ray. Accordingly, the present invention is characterized ent means is employed, with elements thereof having by the passage of redirected radiant energy entirely the same design principle (T.I.R.) as above; said further 25 through the transmitting body means and out the oppo transparent means acting as a secondary radiation redi site side from which it entered, an entirely new concept rector for the purpose of magnifying the degree of con constituting a third class of radiant energy concentra centration and/or chromatic dispersion of the radiant tors, while also having applications to other forms of energy redirected by the primary transparent means. radiant energy redirection than concentration, such as The prior art of radiant energy concentration ingen 30 wavelength separation or collimation. Other surfaces of eral consists of two major types, as exemplified by re the element may be inactive for the ray of interest (e.g., fractive and reflective astronomical telescopes: a refrac as in solar energy concentration of relatively parallel tive lens positioned in front of a receiver, or a retrore rays) but may impinge upon improperly oriented rays flective mirror positioned behind a receiver. The corre (e.g. diffuse skylight of off-angle sunlight). sponding devices in the prior art of solar energy con 35 The T.I.R. elements may be contiguous forming a centration are the Fresnel lens and the parabolic reflec transparent cover means, or separated to allow unde tor, which focus solar energy on a target. Furthermore, flected light to pass between them, for example to be there are non-focussing reflecting concentrators which focused by a mirror upon the back of the target, which have the advantage of fixed daily (non-tracking) posi is thereby illuminated from all directions. tion with only seasonal adjustments, but the disadvan Each element may redirect all of the parallel rays tage of requiring relatively large reflector areas and entering it into a single new direction, or split them into delivering only relatively low energy concentrations. several directions, with or without wavelength separa Fresnel lenses are devices using purely refractive tion, which can be controllably achieved by the inde elements. However, Fresnel lenses have physically in pendent non-normal angling of the entry face and/or herent limitations of redirecting radiant energy, due to 45 the exit face to the parallel rays being redirected, or the low refractive indices of economically available achieved by diffraction gratings upon the exit face. materials, which give high f/ratios and bulky concen While Total Internal Reflection alone is limited to inci trator structure. Moreover, linear Fresnel lenses have, dent angles greater than Brewster's angle and therefore for off-angles in the direction of the grooves, focussing to redirective bend angles less than 180-2X Brew errors, which are also inherent in the laws of refraction, 50 ster's angle (about 96 for acrylic), additional redirec and which limit one-axis tracking configurations to tion is possible with or without wavelength separation relatively low concentration. by the above-mentioned non-normal angling of the Parabolic reflector concentrators have been used, but entry and exit faces. Such large bend angles enable a are subject to losses of received radiant energy because given diameter transparent means to be much closer to the receiver is situated between the source and the re 55 the target than a means limited to refraction alone, flector, which is thereby shaded, preventing in particu thereby greatly reducing the necessary support struc lar the utilization of large heat engines at the focus. ture. Furthermore, a transparent means employing up Furthermore, the receiver is exposed to environmental to 90' bend angles can utilize a flat mirror extending degredation and thermal losses, and the inclusion of a from the target to the rim of the means. protective transparent cover means about the receiver Since a given acceptance angle (of deviation from will merely reduce the system's efficiency. parallelism) produces a proportional requirement for Another reflecting system has appeared in the litera target size, the target can be bisected by the plane of ture, as reported by Rabi in Solar Energy Vol. 19, No. said mirror, and result in an actual target of half the 5. It employs a retro-reflecting means whose elements original size, with no decrease in acceptance angle, by have two Totally Internally Reflecting faces, to redirect 65 insulating the half of the target facing away from the radiant energy out the same side as it came in. Its only redirected body means. Conversely, the target can be improvement over a metal mirror of the same shape is a doubled in size to give a doubled acceptance angle, and potentially higher reflectivity, but the double internal then halved by the mirror back to its original area. This

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surprising potential for halving thermal losses is unique FIG. 5 is a view like FIG. 1 showing a portion of a to the present invention, being unavailable for the para polymorphic optical concentrator of somewhat differ bolic reflector of 90 rim angle because the plane mirror ent, and employed configuration; would shade the aperture, and also unavailable for the FIG. 6 is a schematic showing two devices, operating Fresnel lens because of its far lower rim angle. Unlike in conjunction, one of which is like that of FIG. 1 or 5, the Fresnel lens, chromatic aberration is completely and the other being a collimator; independent of bend angle, and can have any positive, FIG. 7 is an enlarged section through a collimator as zero, or negative values desired for such wavelength used in FIG. 6;

separation applications as solar illumination or bandgap FIG. 8–11, 13, 14 and 15 are schematics showing tailored photovoltaic cells. Unlike the parabolic reflec 10 different applications of the radiant energy concentrat tor, the redirective bend angle of an element is indepen ing means; and dent of its location, greatly adding to design flexibility. FIG, 12a and 12b are fragmentary sections showing (Since the parabolic reflector is a smooth continuum, modified concentrators.

there can be no arbitrary variations in redirective bend DETAILED DESCRIPTION angle from one spot to a neighboring one.) 15

The superiority of the present invention can be seen Referring first to FIG. 1, radiant energy transmitting in the application of direct heating of a fluid storage body means 10 in the shape of a cover or dome has reservoir, as for domestic solar hot water, where the multiple facets or elements as at 11, each facet having an Fresnel lens fails due to an impractically large and ex entry face to receive impingement of such radiation, an pensive structure, and the present invention makes pos 20 exit face to pass energy to the exterior of the body, and sible and slender and economical apparatus that is far an internal reflection face angled relative to the entry more cost-effective than presently installed solar water heating systems based on flat-plate collectors, with their and exit faces to reflect radiant energy incident on the reflection face toward the exit face. For example, in elaborate and intricate systems of controls, pumps pip FIGS. 1 and 4d, a selected facet 11 has, in vertical cross ing and collectors, so prone to high thermal losses and 25 section, an entry face 12 made up of stair-stepped faces low efficiencies. 12a and 12b, an exit face 13 facing the zone of target 15, The advantages of the present invention imply and an internal reflection face 14. Radiant energy such greatly more cost effective solar energy devices than as light is represented by rays 16a and 16b entering the those of the prior art and combinations of the above body means 10 at flat face 12a and normal thereto, and advantages produce highly favorable results. For exam 30 passing internally of the facet for reflection by face 14. ple, the abovementioned domestic solar water heating For this purpose, the face may be silvered at 17. The application will expectable cost much less than a flat reflected rays 16c then pass toward and through exit plate system, it can be installed quickly and easily any face 13, normal thereto, and directly toward the target where in the world, and be capable of long life. This alone will greatly expand the capacity to switch to solar 35 Zone,The body means 10 may consist of solid transparent energy; but the present invention is just as applicable to much higher temperatures, to direct generation of elec material such as glass or plastic, for example. tricity, and to practical solar illumination, bringing fur annularly about,facets

The multiple 11 shown in FIG. 1 may extend and define a common axis 18, or they ther advances over the prior art.

Different forms of this invention may be used in con may FIG.

extend in parallel relation (normal to the plane of 1) at opposite sides of a plane as alternatively figurations that are fixed and non-tracking, or tracking represented by 18, and which is normal to the plane of in one or two axes, and with single or multiple redirec FIG. 1. In either event, corresponding points on the tive stages, and in conjunction with other devices such facets define a concave surface, as for example at 21 as thin films, or lasers. Applications include solar en (defined by the tips 22 of the facets closest the target), ergy systems for photovoltaic, thermophotovoltaic, 45 thermionic, thermoelectric, photothermal, photochemi and characterized in that radiant energy passing cal, photoelectrochemical, photobiological, and pho through the exit faces is directed generally toward the toillumination uses. This invention may also be used as the target zone. Tips 22 are formed at the intersections of a superior collimator for better singly or multiply faces 13 and 14. Surface 21 is parabolic. beamed light sources capable of removing the beams 50 byThe series of facets in FIG. 1 is further characterized the existence of tapered gaps 23 between adjacent invisible heat rays or of polarizing the beam. Finally, the unique configuration of the invention's multiple faces 24 and 14 of the projecting portions of the facets. elements gives it an application in photography and in Faces 24 are inactive surfaces, i.e. do not pass the radia coherent optical information processing, by virtue of tion. See for example representative rays 25 and 26 in the 720-annular paraxial point spread function of its 55 FIG. 1. Ray 25 is re-directed by its associated facet two-dimensional axially-oriented embodiment, almost 90° toward the target, near the outer edge 27 of whereby multiple phase-encoded laser beams could all the "polymorphic lens' 10. Study of FIGS. 1 and 4 will be simultaneously correlated in the area around the show that angle a (the bend angle of the ray) increases focal point. for facets increasing in distance from axis or plane 18; and that angle (3 (the angularity of face 14 relative to a

DRAWING DESCRIPTION line or plane parallel to line or plane 18) increases for FIG. 1 is a vertical section in elevation showing one facets increasing in distance from 18. Also, the entry form of apparatus embodying the invention; faces 12 form stair-step patterns. FIG. 2 is a vertical section in elevation showing an FIG. 1 further shows a Fresnel lens 29 associated other form of apparatus embodying the invention; 65 with polymorphic lens or body 10, and located at a FIG. 3 is an enlarged section on lines 3-3 of FIG. 2; mid-portion of the latter; thus Fresnel lens 29, which FIGS. 4a through 4e are enlarged sections through refracts incident radiant energy toward target 15, is elements of various configurations; located in the path of rays 30 which are re-directed the

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least, i.e. at the smallest angles, toward the target. Lens purpose of secondary concentration. Stray radiation 29 may be integral with lens 10, for example. from diffuse sources, such as skylight, is absorbed by Further, a reflector or mirror surface is shown at 30 blackening the surface 153a of shroud 153 and of lens spaced from and facing the facets at the target side support fin at 130.

thereof. Surface 30 is arranged to reflect stray or diver Various geometric configurations of elements and gent radiation from the extreme outward facets toward arrays of elements are possible, wherein various element the target. See ray 31 in this regard, and reflection point configuration have the same relative angles of the three 31a. This allows target 15 to halve the area exposed to active faces, but differing deployments within the trans heat loss that it would have without surface 30, since parent means; e.g., the T.I.R. face can be in faceted slots the bottom non-illuminated half could be well insulated. 10 on either side of the body means or on the walls of Also shown in FIG. 1 is one form of means to con tunnels within the latter, while the entry faces can be on trollably tilt the assembly of lenses 10 and 29 and reflec faceted steps or even on a completely smooth cover tor 30 to cause axis 18 to remain directed toward a surface. In FIG. 4a, tunnel 40 forms T.I.R. face 41, relatively moving source of radiation, as for example while exit face 42 has stairsteps 42a and 42b. In FIG, 4b, the sun. In that example, a base plate 32 supports reflec 15 slot 50 is on the entry side of the body means, having tor 30 as well as the dome-shaped lenses 10 and 29, via T.I.R. face 51 and entry face 54. Exit face 52 has stair extreme outer edge portion 10a of the body means 10. A steps 52a and 52b. In FIG, 4c, tunnel 60 forms T.I.R. ring gear 33 supports plate 32, and meshes with spur face 61, and entry face 62 and exit face 64 are on smooth gear 34. Drive motor 35 rotates gear 34 to controllably continuous surfaces. However, T.I.R. face 61 must be rotate ring gear 33, and a control unit 36 controls motor 20 longer than T.I.R. faces 41 of FIG, 4a or 51 of FIG. 4b, 35. Unit 36 is responsive to photocells 37 and 38 in such because of the refractive bending of ray 63 by entry face manner that the photocells remain directed toward the 62. In general, the length of a T.I.R. face relative to light source. The photocells are suitably carried at 99 by facet width 65 is:

the plate 32, as for example near its periphery.

Target 15 may for example comprise a fluid recepta 25 T.I.R. LENGTH =cos 8/(cost cosm) cle which is heat conductive to transmit heat to fluid in the receptacle, as for example water in a pipe. where m is the incident angle of ray 63a with surface In FIGS. 2 and 3 the numerals 100 and 129 designate normal 66, 8 is the angle of the refracted ray 63b with lenses corresponding to lenses 10 and 29 described 66, k the incident angle of reflected ray 63c with exit above. They are elongated in the direction of arrow 149 30 surface normal 67, and A the angle of refracted ray 63d and are carried by supports indicated at 150 and 151. with 67. The relationships of these angles are given by V-shaped shroud 152 has edge portions 152a connected Snell's law:

to the opposite edges of lens body 100, so that the shroud and lenses define an enclosure. A second and sin = n sin 6, and sin A = n sink insulative tubular shroud 153 extends within that enclo 35 sure, about a tank 154 which has fixed (non rotatable) where n is the index of refraction of the body means position. A support for the tank may take the form of material. For contiguous elements to redirect to a target legs indicated at 155 and 156, bearings being provided at all the parallel rays incident upon them, neighboring 157 and 158 to allow tank and shroud rotation about elements must be relatively positioned everywhere on central axis 159, along with the lens assembly. The or above a parabola with the target as its focus and a rim shroud 153 is cut-away at locations 160 and 161 to allow slope equal to half the rim angle (i.e. the redirective entry of radiant energy from the lens assembly, to be bend angle of the outermost elements). In FIG. 4d, absorbed by the tank, while heated air is prevented from "extreme' ray 16c must clear tip 22 of the inward adja escaping gap 162 by wipers 163; the enclosure has a cent facet, while the other extreme ray, 16b, must clear reflecting interior surface 152b. 45 top 27 of slot 23. These clearance conditions require Cool liquid such as water enters the tank via pipe 164, that the lens slope angle m be greater than or equal to is heated therein, and discharges into the tank lower end the T.I.R. tilt angle, which is geometrically equivalent at 164a. Warmed liquid slowly flows at 200 backup the to tangent line 22 being on or above said parabola. Note tank, being further heated by contact with the exterior that all of the configurations of FIG. 4 have the same of pipe 164, the liquid leaving the tank at outlet 165. A 50 bend angle a, and except for FIG. 4c, the same normal sacrificial anode 166 in the water 200 is adapted to cor entry and exit faces. See for example the elements 311 of rode, electrolytically suppressing any corrosion of the the “cover' 310 in FIG. 5, above the parabola 321 tan tank itself. Also, a back-up heater 167 in water 200 is gent to the tips 322. See also line 324. Those tips below supplied with electrical current to heat water in the tank the parabola, such as for a quarter-circle 325 with the as when solar radiation is blocked or non-existent, as at 55 same slope at the rim, would in this stairstep configura night. An air-gap may be provided at 162 between tion suffer some interelement impingement, about 10% shroud 153 and the tank itself. Sun tracking mechanism for both cylinders and spheres, but the use of a thin is indicated at 170, to rotate the assembly to maintain flexible inflateable dome for a transparent cover means the sun's rays incident normally toward the lenses 100 might be worth such a loss, especially since the untar and 129, i.e., in direction 171 in FIG. 3. geted rays would still be redirected to a locus within the In operation, all radiation directed parallel to arrow cover means, to assist the pressurization by heating the 171 and striking the lenses 100 and 129 is redirected enclosed air. See FIG. 11 for a non-impinging circular toward the tank, as facilitated by gaps 160 and 161, to configuration. An alternative facet style seeks to mini heat the liquid in the tank. Also note windows 162 and mize such impingement losses by concentrating the rays 163. Wide angle, i.e., almost 180, collection of the solar 65 before they strike the T.I.R. face, which can thereby be rays is employed, as described above in FIG, 1. The gap smaller to reduce said impingement. Convex and con walls 153a are reflective, and may have other, curved, cave entry and exit faces will do this, though with some shapes besides the straight lines shown here, for the decrement of the cover's concentration ratio or accep

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tance angle, which for some applications is far out beyond and further from the target than a parabola (see weighed by bringing the transparent redirecting means 21 and 321). The cover may be constructed of transpar even closer to the target. ent material, as for example plastic. For the smaller bend angles, the present invention FIG. 8 schematically shows a means 410 correspond begins to have difficulties, in the narrowness required of 5 ing to the means 10 of FIG. 1 or 310 of FIG. 5, or the tunnels or slots 23 in FIG. 4d forming the T.I.R. equivalent. A target zone is shown at 415. A retroreflec faces of the low bend-angle elements. This can be some tor means 412 is spaced behind and facing the target what alleviated by raising the profile of the transparent zone so as to redirect radiant energy upon the target means 310 above the parabola 321 to widen the slots and zone. See ray 413.

tunnels beyond their minimum widths. Another form of 10 FIG. 9 schematically shows a radiant energy source such an alleviation is a backbending exit face, 311 of means (as for example a light source) at 430, at the FIG. 5, so angled that its refractive redirection opposes target zone. Radiant energy emitted by the source the redirection of the T.I.R. face, which can thereby means 430 is redirected by the body means 435 (like 10 have a greater redirective bend angle with a less steep or 310) in reverse relation. See ray 436. slope, giving wider tunnels or slots. In FIG. 5, note that 5 FIGS. 10a and 10b show two variations of a "uni ray 330 strikes the exit face 311 non-normally, so that bend' lens with uniform facets extending annularly ray 330a is bent back toward the target. This enables a about a cylindrical target. In FIG. 10a, all the facets 444 wider slot 323 than if the exit face was normal and the of conical body means 440 bend rays 443 through 90 T.I.R. face was at a steeper angle. The above mentioned degrees onto cylindrical target 441. In FIG. 10b, flat convex entry face will also widen the slots or tunnels, body means 445 has identical facets 448 bending rays Another method of widening the slots is the faceted exit 447 through 45 degrees upon cylindrical target 446. face, shown in FIG. 4e. Here slot 70 has been opened FIG. 11 shows a structural means 460 enclosing the until it nearly impinges upon extreme ray 73b. Exit face space 461 behind the exit face of the cover means 459 74 has miniature stairsteps 74a and 74b, respectively (like 10 or 310), so that pressurization of the atmosphere normal to and parallel to reflected ray 73b. Alterna 25 of space 461 will hold the flexible cover means in its tively, a thin microstructured series of elements of high distended or circular shape, with center of curvature at refractive index (say n = 4) can be embedded in the body point 426. See target zone 462, pressurization means means to form more favorably shaped elements. The such as a pump 463, and ray 464. A thin film 465 adheres particular manufacturing method and design applica to the inside of cover means 459, having miniature saw tion will determine the place of transition to a Fresnel 30 tooth facets 467 as shown in the insert. lens, or alternatively to a window that passes rays to a FIG. 12a shows a plurality (two for example) of tar small parabolic reflector behind the target, which is get zones 470 and 471 to receive radiant energy from thereby illuminated from a full circle of directions. the transmitting body means 472 (like 10 or 310). Each Another possible configuration would have the outer element 473 redirects energy in a plurality of directions, parts of the redirecting means sending radiant energy to 35 toward the target zones. Thus, each element 473 may be a central target while the inner parts redirected energy like element 10 or 310 described above, but have a to outer targets, using only large bend angles through T.I.R. face divided into two sub-faces 474 and 475 at out. All these configurations are derivatives of the basic slightly different angles to accomplish the reflection of method of this invention: upon multiple Totally Inter the two rays 476 and 477 respectively directed by the nally Reflecting transmitting elements, properly placed faces 474 and 475 toward the two target zones. In FIG. entry, exit, and T.I.R. faces redirect radiant energy to a 12b, T.I.R. face 453 is the exit face for ray 451, while predetermined target zone. T.I.R. face 454 is the exit face for ray 452. This symmet It should also be said that the present invention em rical case of twin 60 degree bends may be varied to give ploys a cover means (as at 10 or 110) whose focal length two different right and left hand bends, with differing can be shorter than any parabolic mirror with concen 45 division of the incoming radiant energy. In FIG. 13 the trations twice as high, but which is free from shading cover means 480 (like 10 or 310) has different groups of and presents a convex surface with lower aerodynamic elements redirecting radiant energy toward different drag than the concave parabolic mirror. Its target is target zones. Thus, the elements at locus 481 direct nearer the center of gravity and closer to the ground radiant energy toward target 482, and the elements at than that of the parabolic reflector, making fixed re 50 locus 483 direct energy toward target 484. See rays 485 ceiver means easier to design and maintain. Finally, the and 486.

nearly 100% reflective efficiency of the Total Internally In FIG. 6, cover or body means 510 corresponds to Reflecting faces of the present invention give much 10 or 310 described above. A secondary radiant energy greater potential for high efficiencies than does the redirecting means is provided at 520 to intercept the parabolic mirror. 55 radiant energy from body 510, and to redirect it. See In FIGS. 1 and 5, it will be understood that the ele rays 521 with segments 521a falling on body 510; redi ments 11 and 311 join together, integrally and continu rected segments 521b falling on body 520; and second ously, to form a radiant energy transmitting means in arily redirected segments 521c transmitted by body 520. the general form of a cover. The latter has an energy FIG. 7 shows body 520 in detail, with entry faces 530, entry surface (top surface in FIG. 1, for example) and an 60 exit faces 531, and T.I.R. faces 532. The rays 521c are exit surface (bottom surface in FIG. 1) lying on opposite parallel, in this instance, i.e. collimated, so that means sides of the cover. The cover causes radiant energy 520 may be regarded as a collimator.

leaving the exit surface to have a generally different The means 550 shown in FIG. 14 is like 10 and 300, direction than the direction of energy incidence on the except that the exit faces 551 are individually angled entry surface. Also, multiple T.I.R. faces are situated on 65 relative to radiant energy passing through them, so as to the exit surface adjacent slots proximate the exit surface, cause refractive redirection of the radiant energy. See as referred to above. The entry surface has a faceted beam 552 refracted at face 551. Also in FIG. 14, the exit stairstep configuration. The exit surface of the cover lies faces 551 may be considered to refractively redirect

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radiant energy in partial opposition to the redirection by reflection of all radiant energy whose incident angle the T.I.R. faces 553, the latter extending at less steep with the normal of said boundary at the point of inci angles (than in FIGS. 1 and 5) so as to widen the slots dence exceeds Brewster's angle, which equals the in 554, Note also in FIG. 14 that the entry face is smooth verse sine of the reciprocal of "n". and unfaceted, at 556, and that exit face 551 is parallel to 3. The system of claim 1 wherein said perimeters of refracted ray 552b, giving the maximum backbend and said elements project from said cross-section to extend the lowest possible slope of entry surface 556, which in linearly, in parallel relation, said entry faces facing said fact is lower than the parabola 321 or the quarter-circle incident radiant energy, said exit faces facing said target

ZOc,

In FIG. 15 the body means 560 is like that at 10 or 10 310, except that it utilizes the variation index of refrac said4. elements

The system of claim 1 wherein said perimeters of project from said cross-section to extend tion that varies with the wavelength of the radiant en ergy, so as to constitute a wavelength separating, radi annularly about, and define, a common axis, said entry ant energy redirecting, transmitting body means. Two faces facing said incident radiant energy, said exit faces target zones 561 and 562 are shown, and are spaced 15 facing said target zone.

5. The system of claim 1 including a Fresnel lens apart to receive different wavelengths of the wave length separated, redirected, radiant energy. See inci associated with said body means located in a midportion dent ray 563 which separates into ray 563a of one wave of said body means so as to redirect radiant energy length directed toward target 561, and ray 563b of an through relatively small angles toward the target zone. other wavelength directed toward target 562. 20 6. The system of claim 1 including a retroreflecting In FIG. 15, either target may be considered as a means spaced behind and facing said target zone so as to means to convert radiant energy to electricity. One redirect radiant energy upon said target zone. such means is a photovoltaic cell. Such a device may be 7. The system of claim 1 including a radiant energy located at the target zones in FIGS. 1 and 5. In FIG. 15, source means situated in said target zone, and radiant one target may comprise a photoillumination means 25 energy emitted by said source means being redirected receiving visible wavelengths; and the other target may by said body means in reverse relation to the transmis comprise a thermal receiver receiving invisible wave sion by the body means in claim 1. lengths, at zone 561. 8. The system of claim 1 including a radiant energy When a source of radiant energy is placed in zone redirecting means situated at said target zone. 562, the visible wavelength rays will follow the reverse 30 9. The system of claim 1 including a radiant energy path of rays 563 i.e., be collimated, while the invisible. absorbing fluid receptacle at said target zone. longer-wavelength heat rays will be diverged more 10. The system of claim 9 including means to convey outwards from the visible beam, so that spotlights on relatively cool fluid into said receptacle and relatively actors will not subject them to a heat load several times hot fluid out of said receptacle.

greater than that of the visible radiation. 35 11. The system of claim 9 including thermally insulat We claim:

1. A radiant energy redirecting system comprising ing means about said receptacle, said means having a (a) a radiant energy transmitting body means, radiation entrance situated about said target zone so that (b) said means comprising multiple elements, each of cle. redirected radiant energy is absorbed by said recepta which acts as a radiant energy redirecting module, 40 12. The system of claim 1 wherein said elements join having on its cross-sectional perimeter an entry contiguously to form a radiant energy transmitting face to receive incidence of said energy into the cover means with interior of said perimeter, an exit face to pass said lying on opposed ansides entry surface and an exit surface of said cover means, which energy to the exterior of said perimeter in a direc cover means causes radiant energy leaving the exit tion towards the reverse side of the body from the 45 surface to have a generally different direction than it side of said incidence, and a Totally Internally did at incidence upon said entry surface.

Reflecting face angled relative to said entry and 13. The system of claim 12 wherein multiple Totally exit faces to redirect towards said exit face the radiant energy incident from said entry face, Internally Reflecting faces are situated on facets defined (c) said body means generally redirecting incident SO by said entry surface.

radiant energy for travel towards a predetermined 14. The system of claim 12 wherein the Totally Inter target zone situated apart from and on the reverse nally Reflecting faces are situated on walls adjacent side of said body relative to the side of said inci voids extending within the interior of said radiant en dence, said entry faces defining a first set and said ergy transmitting body means, exit faces defining a second set, the faces of one of 55 15. The system of claim 12 wherein the entry surface the sets being variably angled relative to one an has a faceted stairstep configuration.

other, and with angularity that progressively in 16. The system of claim 12 wherein said exit surface creases for successive elements, relative to the tar of said cover means lies beyond and further from the get zone, target than said parabola, (d) the elements forming tapered gaps therebetween, 60 17. The system of claim 12 wherein said gaps having apices, the body being continuous (a) said cover means forms a circular shape, and uninterrupted everywhere along straightlines (b) and including structural means enclosing the joining successive of said apices, in planes normal space behind the exit surface, so that pressurization to said faces. of the atmosphere of said enclosed space will help 2. The system of claim 1 wherein the Totally Inter hold said cover means in said circular shape. nally Reflecting face is a body boundary, so that the 18. The system of claim 1 wherein there is a plurality index of refraction "n" of the substance of said transpar of target zones to receive redirected radiant energy ent body means at said boundary gives total internal from said transmitting body means.

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19. The system of claim 18 wherein each element the sets being variably angled relative to one an redirects radiant energy in a plurality of directions, other, towards said target zones. (d) said elements joining contiguously to form a radi 20. The system of claim 18 wherein different groups ant energy transmitting cover means with an entry of elements redirect radiant energy towards different 5 surface and an exit surface lying on opposed sides target Zones. of said cover means, which cover means causes 21. The system of claim 18 wherein secondary radiant radiant energy leaving the exit surface to have a energy redirecting means are provided to intercept said generally different direction than it did at incidence upon said entry surface, redirected radiant energy from said transmitting body O (e) said entry surface being smooth and unfaceted, S. containing thereupon said individually angled 22. The system of claim wherein the entry and/or entry faces, so relatively positioned as to smoothly exit faces are individually angled relative to the radiant be a part of said entry surface. energy passing through them so as to cause refractive 26. The system of claim 25 wherein multiple Totally redirection of said radiant energy. 15 Internally Reflecting faces are situated adjacent slots 23. The system of claim 1 including means to control proximate said exit surface.

lably tilt said body to cause said entry faces to remain 27. The system of combination of claim 26 wherein properly inclined relative to an angularly moving said exit faces refractively redirect radiant energy in source of radiant energy, such as the sun. partial opposition to the redirection by the Total Inter 24. The system of claim 1 wherein said entry faces angle nally Reflecting faces which lie at a less steep relative together form a smooth dome. so as to widen said slots in said faceted exit sur face, 25. A radiant energy redirecting system comprising 28. The system of claim 25 wherein the outer edges of (a) a radiant energy transmitting body means, said exit surface lie on a parabola whose geometric (b) said means comprising multiple elements, each of 25 focus is in the target zone.

which acts as a radiant energy redirecting module, 29. The system of claim 25 wherein the radiant en having on its cross-sectional perimeter an entry ergy transmitting body means has an index of refraction face to receive incidence of said energy into the varying with the wavelength of said radiant energy, so interior of said perimeter, an exit face to pass said as to constitute a wavelength separating radiant energy energy to the exterior of said perimeter in a direc redirecting transmitting body means.

tion towards the reverse side of the body from the 30. The system of claim 29 wherein the target zones side of said incidence, and a Totally Internally are spaced apart to receive different wavelengths of the wavelength-separated redirected radiant energy.

Reflecting face angled relative to said entry and 31. The system of claim 30, wherein means for con exit faces to redirect towards said exit face the 35 radiant energy incident from said entry face, verting radiant energy directly to electricity are situ (c) said body means generally redirecting incident ated in the target zone.

32. The system of claim 30 wherein visible wave radiant energy for travel towards a predetermined lengths are redirected toward a radiant-energy receiv target zone situated apart from and on the reverse ing photoillumination means at one target zone and the side of said body relative to the side of said inci 40 invisible wavelengths are redirected toward a thermal dence, said entry faces defining a first set and said receiver at another target zone.

exit faces defining a second set, the faces of one of