CA1192791A

CA1192791A - Light wall panel with reflector profile strips

Info

Publication number: CA1192791A
Application number: CA000362989A
Authority: CA
Inventors: Helmut W.O. Koster
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-07-25
Filing date: 1980-10-20
Publication date: 1985-09-03
Also published as: DE2930103A1

Abstract

ABSTRACT OF THE DISCLOSURE

The invention provides light and heat controlling panels which may be used for example as facings for walls or as roof elements. The panels can also be used as energy concentrators for concentrating light energy onto energy collectors associated with the panels or with the walls, etc. on which they are located. Thus, the panels can be used as an equipment for the automatic control of the incidence of solar radiation. Each panel consists of two spaced light-transmitting wall elements between which are disposed a plurality of light-impervious elements horizontally-oriented and parallel to each other, the upper and lower-sides of two immediately adjacent elements being of different profile and forming an incidence and a concentration space for the radiation. An energy collector may be disposed in this concentration space. Depending on the angle of incidence of the solar radiation a certain amount is reflected back through the incoming side into the outer space, the amount of reflected and transmitted energy varying with the change of seasons. Energy transmission through the panel will be increased in the cooler seasons characterised by lower angles of incidence, while the energy reflection is increased in the hotter seasons characterised by higher angles of incidence. The relative energy transmission and reflection is controlled by means of choice of the shape and disposition of the element profiles. Heat control of a building is achieved by using the panels as a curtain wall therefor.

Description

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LIGHT ~ALL PANELS FOR CONTROL OF THE TRANSMISSIO~
THERETHROUGH OF INCIDENT LIGHT ENERGY

The invention pertains to improvements in wall panels able to control the transmission therethrough of incident light energy in accordance with its angle of incidence thereon, particularly solar radiation. The panels of the invention provide control of their heat-flow-through resistance while also providing a visual barrier.
lt is known how to design light wall panels with high heat-flow-through resistance and opaqueness. For example, opacity to vision can be produced by tinting, but this results in an opaqueness in regard to all forms of solar energy, which is not always desired. An increase in the heat-flow-through resistance can be achieved by a multi-layer panel construction and/or through reinforcement by use of specific insulating material, i.e. air layers. Increase of the thickness of the air~layer is effective as an insulating measure only up to a cer~ain limiting value. Multi-layer panels can produce the required opacity but an increased energy absorption or reflection takes place because of the multiple layers, so that the amount of solar energy transmitted is reduced.
In accordance with the present invention there is provided a panel providing for the control of the transmission therethrough of incident light energy in accordance with the angle of incidence of the light energy thereon comprising two spaced light transmitting sheets constituting respectively a ray penetrating panel outer side and a ray emerging panel inner side and between which sheets are disposed a plurality of pairs of light impervious elements arranged parallel and spaced from one ~J ~

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another, wherein adjacent elements of successive pairs of light impervious elements form between themselves an ingoinq irradiation cross~section which is a section in which the light enters a hollow section between the two spaced sheets and an outgoing emission cross-section which is a section in which liqht exits from this hollow section.
characterised in that the upper side of a first li~ht impervious element of a pair thereof is reflective and forms with the underside of a second liqht impervious element of the pair, which underside is also reflective, a liqht enerqy concentration cross-section space which is a section in which the light energy rays are concentrated disposed between the said ingoing irradiation and outgoinq emission cross-section, and that the contour of the said upper side of the said first element of a pair differs in curvature from that of the said underside of the said second element of a pair so that an energy irradiation density substantially independent of the light incident angle is obtained.
Panels of the invention are able to provide integrated sun protection and increased heat-flow-through resistance while providing a visual barrier in such a manner, that, by arangement of the panels in coordination with the heating demands of a building, solar heatina of the building takes place in the winter by solar energy transmitted through the light wall panels, while shading and conse~uent cooling of the building occurs in the summer by the same panels.
In the panels of the invention the said liqht impervious elements may constitute reflector systems of reflecting-profile-strip-type installed within the space between the spaced liqht transmitting sheets.
rrhese reflector systems accomplish the followinq;
l. Due to design of the reflecting surfaces, the amount of penetrating rays of solar energy can be controlled, based on the elevation angle of the sun.

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2. The reflecting surfaces represent a visual protection towards the inner space of the panel.

3. Due to the reflecting surfaces, a concentration effect can be achieved at particular locations within the panel through which it is possible to provide the light wall panel with a heat insulation factor in predetermined relation to its concentration factor.
In acldition the light wall panels represent the following advantages when functioning as reflector systems:
lo The reflectors may be disposed in an insulated air space. Therefore, firstly contamination and secondly static load of the reflectors by wind forces are both prevented. This allows a very simple design of reflectors.
2. The wall or flange surfaces of the panels represent a simple possibility for fastening the reflectors over their entire length. This permits a very precise and inexpensive positioning of the reflectors as e.g. through laying-on or gluing.
3. The reflector profile strips are themselves a very rigid construction element, through which, by statically effective gluing to the wall surfaces, less material is used and a high degree of rigidity of the panels can be achieved.

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The integration of reflectors into the light wall panel cal~ses a very small scale development of the reflecting surfaces. Ihis requires a multitude of reflecting strips which must be properly hung and adjusted. The inven-tion thereore provides for the development of several reflecting surfaces in -the form of a profile strip~ This design is of special importance with respect to the manwfacturing process. The reflector profile strips are manufactured from reflecting thin strip, in a forming machine with a high production speed, and installed in the light wall panel, so that on location only a horizontal adjustment is required. Individual positioning of the reflecting surfaces can be omitted. A significant advantage of the invention idea follows from this designing- and manufacturing process, that is in installing reflector systems in a light wall panel for the recovery of solar energy. Until today, to my knowledge concentration systems on front walls have not been utilized, because no industrialized process had been found for the development and hanging of the reflectors. A
further advantage of the design for concentration systems according to the invention lies in the adjusting capabilities, whereby the light panels are especially suitable as sidingS and whereby the wall cross section can temporarily serve as a heat accumulator and heat-supplier for the inner space.
As is especially apparent in the example of a "Trombe-wall", the ligh~ wall panel in accordance with the ~, 5 j 7'g~
invention, can serve as an insulating system for an inner space ~in this case the space between the panel and a heat-storing wall) with controlled opaqueness toward solar energy. The solar energy is transmitted behind the panel via the reElectin~
surfaces, so that it receives heat from outer space, however, no heat is given off to the same. The light wall panels can thus represent a type of energy trap.
Especially in the case of the Trombe-wall, the ability of the panels to function as a visual barrier must be emphasised. To achieve good energy absorption on the wall behind the panel, which is designed as a collector, the same must be painted black. However, it is desirable for esthetic reasons regarding a building front to achieve a bright and friendly front and to hide the black wall surface. This occurs with a panel of the invention via the reflector system. The reflector also allows a colouring of the wall, which is achieved by means of a transparent color lining.
The improved heat protection by ~he light wall panels is effected through the reflector profile strips, by which either several insulated hollow spaces are formed, or a heat-insulation is placed in the panel-cross section by means of foamed insertions.
Specific embodiments of the invention are explained in connection with the accompanying diagramma-tic drawings, wherein:
FIG. 1 is a longitudinal cross-section through a plate ~,,,,',, ' which is a first embodiment showing a lay-out of reElector profile strips in the hollow chambers formed therein;
FIG. 2 is a similar section through a second embodiment including a concentration systern on the ray-penetrating side of the plate as well as a dif~user system on the inner side of the plate space and central hanging of the profile strips, allowing penetration o rays through the plate.
FIG. 3 is a similar section through a third embodiment having reflector profile strips with integrated collector part and showing hanging of the reflectors on the panel wall surface via adhesive;
FIG. 4 shows a light wall panel which is a fourth embodimerlt with integrated collector parts on the inner side of the panel space, in front of a collector/accumulator on the outer wall;
FIG. 5 illustrates a light wall panel as a flat collector cover wi~h a design of reflector proEile strips providing ~ concentration systemO
FIG. 5.1 is a section similar to Fig. 5 but with insulation provided between the shading-zone of the collector cover and the absorbing plate;
FIG. 6 illustrates the use o~ light wall panels as roofing over a collector/accu~ulator cover with parabola-like re~lecting surfaces over the ray-penetrating cross-section and several layers on the inner side of the space, which allows rays to penetrate through the panel;

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FIG. 7 is a functional diagram of the dependence of the concentration factor of the plates upon the angle of incidence of the pentrating rays;
FIG~ 8 illustrates a concentration system with a reflecting surface, consisting of several parabola-like portions with offset focal points as well as variously tilted parabola axes, so as to achieve several staqgered peak values for the density of penetrating rays within the cross-sectional concentration;
FIG. 9 is a functional diagram similar to Fig. 7 of the concentration device according to Fig. 8; and FIG. 10 is a functional diagram as in Fig. 9, showinq the seasonal dependence of the density for pentrating rays.
Fiqure 1 shows the cross section through a first embodiment which is a double-flange plate 10 with spaced light-transmitting wall surfaces 11 and 12 and flanqe surfaces 13. In the resulting hollow ch3mbers 14 rel~ctor profile strips 15 are positioned, each providing at its underside and uppersides respective liqht impervious reflecting elements 19 and 19', the underside element 19 of the strip facing the upperside element lg' of the immediately adjacent strip, so that each pair of elements form a light ener~y concentration cross-section space in which the li~ht energy rays are concentrated bounded by respective in~oing and outgoing cross-sections in which the light rays enter the hollow chamber and exists from the chamber at the respective light transmitting walls 12 and are directed by means of reflection from the reflector profile 1 ~ 9 ~ ~ 9 . ~
strips or directly through the flange plate 13, and the rear wall surface 11 (located towards the inner space) onto an absorbing outer wall 16, changed to heat by the absorption and stored in the material of the outer wall. The rear of inner space wall 11 is lined with a heat reflecting foil 17 in the areas thereof covered by the reflector profile strips 15, so that the energy incident thereon is also reflected back towards the wall 16.

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The following functional advantages of the light wall panels, according to the invention are explained, in connection with th;s embodirnent as follows:
Based on the concentration factor of the reflector sys~em constituted by the strips 15 only approximately 1/3 of ~he inner space wall ll allows light to penetrate, and approximately 2/3 is designed as a heat reflector, while the wall 12, located towards the outer space, absorbs the radiated energy over its entire area. The panel thus serves primarily as an insulation for the radiant heat radiated from the outer wall accumulator 16, but also exhibits a specific opaqueness for light rays incident thereon, so that the solar energy obtained from the outside is transmitted behind the panel and can be stored there. The insulating capability of the panel-cross sec~ion is significantly improved by the reflector profile s~rip and flange structures, whereby additional hollow spaces are producedO It is especially advantageous to design the reflector profile strips so that they reflect on bo~h sides in order to increase the heat-flow-through resistance. More specifically each strip comprises a parabolic arched, diagonally arranged reflec~ing surface 19, by which a solid mechanical reinforcement of the double-flange-plate 10 occurs. The strips also include ~e additional reflecting surface 19'. Additional rigidity can be provided by means of s~ructure foam in the profile chamber 13 be~ween the surfaces 15 and 19'.

( The absorbing surface 16 is not visible from the outer space because of the visual barrier of the reflector profile strips 15. The entire front of the panel appears to be reflecting, but without a glaring e~fect.
It will be seen that each strip lS comprises a reflecting upper side provided by the surface 19' and a reflecting lower sids provided by the surface 19, with each upper side of an element facing the lower side of the first neighbouring element and the lower side of the same element facing the upper side of the second neighbouring elemsnt, except of course at the two ends of the panel. A specific shape for the reflecting sides is illustrated consisting of the parabolic surface 19 and a sloping flat surface portion followed by a concave curved surface portion for ~he surface 19'.
In ~igure 2 a triple layer light wall panel 20 is shown, whereby re1ector/diffuser profile strips 27 are hung on a central panel member 23, which allows rays to penetrate between inner and outer layers 23 and 24. This type of lay-out and hanging method has the advantage that in this manner no thermal bridge exists between the outer and inner layers 24 and 25. The inner g ~, 79 ~
layer 23 is provided with hangers 26 on which the reflector strips 27 are hung.
The reflector profile strips are designed with two protrusions on either side of the central member 23 to form a concentration system 21 and a diffuser system 22. ~ach diffuser strip 27 is designed in such way, that the rays falling on to the diffuser system are diffused in -to the inner space. When utilizing the light wall panel as a window, this enables a uniform and glare free light-penetration. When using it as a collector cover, for example for a Trombé-Wall, a uniform energy distribution onto the collec-tor surface of the Trombé Wall is achieved throughout the diffuser system, so that a heat accumula~ion in the area of concentrated energy irradiation is avoided. The radiation is incident on the reflecting surface 28, which is concave with a center 29, passes through the cross sectional concentration area 30 and is reflected onto the diffuser 27. At the same time, the diffuser 27 represents a heat reflec~or for the layer 25, which allows rays to penetrate and be converted to thermal energy by the collector surface behind. A further advantage of the diffuser system lies in the conditions for penetrating rays. At the layer 25 a certain reflecting loss occurs by rays which are reflected back onto the diffuser 27. Due to ~he conical shape of the space between layer 25 and diffuser 27 the reflecting portion is subject to multiple reflection as illustrated at 31, so that reflecting ,~

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loss is minimised. This also makes it possible to design the absorbing surface as a light collector when using the panels, which also means designing the panels as non-absorbent, due to the fact that the reflected rays are returned back to the collector via the diffuser. Because the emission coefficient is equal to the absorption coefficient, with the help of a diffuser which is designed accordingly, the emission of a collector surface can be reduced through decreasing of the absorption capability at equal or higher tota] absorption coefficients.
According to the invention, this ~akes the light wall panel also suitable as a collec-tor cover for flat collectors which tend to be reflective.
The development of ~he diffuser system also allows a multiple glass enclosure of the inner-space-side, without the occurrence of a loss by absorption of energy following reflection. Furthermore, it is possible to install a heat reflector 32 on the inner-space-side of the layer 2S. Such heat reflectors are produced for example by metallic vaporization on to a suppor~ing substrate and generally possess a reflecting capability for visible rays. As to mul-tiple reflection by the diffuser 27, the reflected portion of the rays is led back, so that in spite of the reflecting effect a loss by absorption is avoided. The diffuser system therefor permits a high level of effectiveness regarding energy recovery and thermal energy storage, the embodiment of ~igure 2, as mentioned above~

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being especially suitable as a front element for a Trombé-wall.
In the embodiment of Figure 3 an energy receiver 34 is integrated into the reflecting system on the ray-penetrating side, which receives a constant density of energy absorption, essentially independent from the seasonal variation in the angle of eievation of the sun.
The receiver 34 is penetrated by rays on one side received from a reflector surface consisting of two surface portions 36 and 37. The surface portion 36 extends from an end point 38 to an end point 39 and is calcula~ed from the maximum irradiation angle B max., this angle being that of the radiation which is just tangential to the outer cross section of the pipe constituting the receiver 340 The end poin~ 39 results from the incidence on the surface 36 of a shading line 40 which is tangential to the absorbing pipe 34 at the maximum irradiation angle B max. The reflecting surface 37 extends from the end point 39 to the absorbing pipe 34 as an involute of the absorbing pipe~
The absorber pipe 34 is installed in such a manner3 that the reflection 41 of a beam 42 forms a tangent on the absorber pipe at a minimum irradiation angle B min. taken rom ''~

the end point 43 on the reverse side 44 of the deflecting surface 45. The tangent ray 41 is calculated from the angle ~1 ~ a2 of the radiation to the radius 46 o~ the deflection surface 45. In case of ano~her receiver-form for the surface 45, e.g. a level surface, a corresponding construction is utilized, whereby the reflections hit the outer end point of the receiving surface at a maximum and respectively a minimum irradiation angle~
The receiver in this embodiment is an absorber pipe through which a heat ~ransfer medium may flow; that is used for example to heat utility wa~er. AlternatiYely the receiver may consist of photo cells 52, which, as shown in the upper representation 47, are placed in a glass tube through which the fluid may flow.
In this embodiment an additional alternatiYe for the mounting of the reflector profile strips 33 is shown. They are adhesively secured ~o the outer and inner wall panels 50 and 51 with insulating strips 48 and 49 respectively which have adhesive on both sides~ The insulating strips are produced of foamed material, so that firstly they have the capability to prevent a thermal flow from the inner to the ou~er spaee, and secondly they possess a sufficient inner expension capability to absorb different temperature expansions of the materials of the panels.
Fig. 4 shows a further embodiment of the inven~ion utilizing two differently working collector types~ In ,, !

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this embodiment the radiation is incident or is reElected from a single parabolic arched concentration reflector 55 into the cross-sectional space 56, is reflected ~rorn a radial deflecting surface 57 on to the inner-space side, and either guided directly or via reflection at a diEfuser 61 through an opening 59 onto the collector s-torage surface 62, or through an opening 60 into a collector 63.
In the winter the energy distribution that occurs over the openings 59 ano 6C, at the corresponding lo~ irradiation angle ~ means that the outer wall collector 62 is in use, as well as the collector 63, while toward the summer7 with increased irradiation angle the portion incident on the outer ~all collector 62 decreases, and the larger portion of the energy is guided onto the collector 63. This difference in radiation distribution in accordance with the irradiation angle ~ is represented in the example by means of the rays 64, 65.
With this collector design also, an automatic effect is achieved, which allows an almost constant energy-density in collector 63 throughout the year, and a continuously decreasing energy density in the case of increasing irradiation angle on the outer wall. The collector 63 is designed as a concentrating collector with a round absorbing pipe 65.
This type of embo~iment having two collector types functioning in dependency to each other brings special thermo-dynamic ~dvantages as ~ell as production-technical advantages.

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Thus, the penetrating collector system 63 is installed on the warm inner-space side of the panel. The irradiation of energy into the collector 63 occurs from below so that the heat losses of the absorber are accumulated in the collector and cannot escape. This leads to a stabilization of the surrounding temperature for the absorber 65, whereby the heat loss can be reduced.
A concentration reflector 66 at the rear side of the collector 65 at the same time serves as a heat reflector for the outer wall absorbing surface 62. ~urthermore, due to the concentration reflector 66, convective flow in the inner space 67 between panel and outer wall absorbing surface 62 is prevented.
The location of the penetrating collector 63 on the inner space side, among other things, represents a significant simplification in regard to manufac-turing specifications. The light wall panel along with the reflector profile strips 68 and the sheets 69 and 70 can be manufactured with a lock on the reverse side of the insulating glass enclosing elements. Now on the reverse side, the absorbers 65 are positioned and reflector strips 66 are glued on, whereby the gluing locations 71 and 72 of the reflector profile strips coincide. Due to the foamed adhesive strips 73 and 74, the thermal energy, which is absorbed by ~he sheet 70 in the ray-penetrating area 59, 60 is insulated from the stripsO

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The location of the collectors 63 on the reverse side of the panel, has a special advantage even with respect to front wall moun~ing. Thus, the panel can be installed by a supporting cross bar system without it being penetrated by the absorbing pipe. The absorbers 6S can be connected to vertical forward and return pipes in a grate shape, without causing contact with a supporting carrying crossbar system. This also is a simplification of an insulation thermal problern~
The term "light wall panel" does not necessarily refer to a vertical layout. The panels can, for example, be installed sloped as a roofing for a greenhouse or as coverage for flat collectors, as mentioned before.
Fig. 5 shows an embodiment of the light wall panels according to the inven~ion operable as a collector cover. The reflector profile strips 80 are again designed as a concentration system aS a supplement to the inYention there is now described ~ new design of the reflector system behind cross sectional concentration area 81. The reflector element 82 is elongated beyond the end point 83 by an integral portion 84. This section 84 extends to the end point 85 which is located on a curve 86 around the ocal point 87 of the element 82. However the section 84 at i~s maximum extends to an end point 88, which is positioned at the intersection of two curves 86~ 89 around the side wall end point 83, 87 in the said ~ 7~ ~
cross sectional concentration area 81. The end point 85 forms the outer extremity for a curved deflecting surface 90, through which the radiation is directed onto the absorbing surface 91.
The elongation portion 8~ enables the positioning of the openings cross section 93 through the rear panel at a speciflc distance from cross sectional concentration 81, so that firstly a heat heat reflection is avoided in the irradiation funnel and secondly, due to the curved deflecting surface 90, a cage is formed over the irradiation opening 93, whereby ~7arm air can accumulate without 10wing directly into the irradiation funnel 94 and becoming cool on the outer sheet 95.
The inner sheet 92 is provided with a heat reflecting lining 96 in the shaded zone. From the relationship of the irradiation opening to the shade-zone, which results from the concentration factor, it can be observed that the panel allows a very good effectiveness level for energy recovery since the larger portion of the absorbing surface is covered by a heat reflector. In the structure of Fig. 5.1 the absorbing surface is designed to be as big as the cross sectional concentration.
This corresponds with the design of conventional concentration collectors. However, it appears to be more advantageous to design the absorber surface to be as big as the panel itself, and to position the same at a distance from the absorber surface. Due to this the non-absorbed portion of radiation is reflected onto the heat reflector 96 and again directed back ~ 17 -,. .

onto the absorber surface. Furthermore, due to the energy distribution a localized overheating of the absorber below the panel is prevented in the irradiation area and thus also the heat radiation of the absorber, this energy diffusion being improved by a diffuser as mentioned previously. I the collector is being operated with extremely high temperature, it is economical to direct the radiation energy via additional deflecting surfaces below ~he shade zone 92 onto an absorber;
the deflecting suraces are either part of the reflector profile strips 80 or are fastened on the inner space side~
Fig. 6 shows another embodiment o the light wall panels o~ the invention as a collector cover installed in a sloped fashion. Here again a concentration syste~
i5 utilized. With the structure of Figure 5 a diffuser 101 is used behind cross sectional concentration area 100, which is designed in such a way, tha~ each ray 102 reflected from the surface 101, is reflected back ~o i~ at least onceO This requirement is fulfilled when the difuser 101 forms a parabola with ~he focal point F in the end point o the oppositely located side wall surface 103. Between collector cover and absorber surface 104 several oils lOS and 106 are placed as a heat protection measureO The radiation portion indicated by rays 107 and 108 reflected by ~hese foils is re1ec~ed back either on ~he diffuser or on the reflec~ing under-side 10~ of the collector 9~
/
cover to the diffuser. Here the absorber is a collector-storage of a ceiling construction 110, above which the light wall panel is positioned as roofing, and can be compared in function with the siding panels of Pigs. 1-4, in reference to its capability of guiding the solar energy which falls at a low irradiation angle to the absorber surface in the winter, and in the summer at a larger angle, and to shade the absorber surface~ and thus keep it cool. This capability is shown in the dia8ram of Fig~ 7.
The irradiation data shown corresponds to the solar azimuth angle at the 50~h degree of latitude at 12:00 o'clock mid~day. The curve 111 represents the ma~hematical concentration factor in coordina~ion with the irradiation angle. The deviation of the curve in the area 112 is caused by a continuously increasing radiation portion which is reflected from the side wall sectio~ 113 between the end poin~s 114 and llS out of the irradiation opening. Due to the elongated side wall part 113 an especially high concentration factor is reached during the coldest time of the year at a low irradiation angle.
The radia~ion reflected out of the irradiation opening falls in a very low angle onto the outer sheet 116. Wikh this low radiation angle the reflection portion is very high, so that a reflection back to the concentration funnel occurs and concentration factor according to curve portions 117 and 118 of the diagram in Fig~ 7 develops.
Fig. 8 shows a further development of a concentration s.Ystem Z7~
whereby a special low radiation angle of the outer cover sheet is to be reached during the Eading out of the individual surface sections, to achieve a high reflecting effect if possible, following a reflection on the cover sheet. The design of the reflector profile strips, according to this invention, follo~s from the Eact that the outer cover sheet of the light wall panel is utilized as a reflector in order to achieve an increase of the total receiving angle of the light wall panel, which is larger than the receiving angle of the reflector system itself.
This problem is solved hy the fact that -the elongated side wall section 120 is designed to be arched parabolic, and that the focus point F2 is located behind the opposite side wall surface 121. The focal point is positioned in an optimu~
fashion on a circular section around the focal point F3 of the first side wall section 122. The radius r of the circular arc 123 corresponds to the width of cross sectional concentration area 124, so that via the oppositely located side wall panel 121 a shifting of the actual focal point F2 to the end point of the parabolic side wall surface 122 occurs. The arching of the side wall surface develops fro~ center points of circular paths via F2 and F2l.
This -type of design has two advantages. Firstly the oppositely located side wall section 121 is shortened, whereby the direct irradiation portion in the cross sectional concentration area 124 is increased in irradi tion angles which ,~,.. .

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are larger than the receiving angles of the concentration system. Thus an energy absorption still takes place when the reflected rays are already completely attenuated. Secondly as a result Or the focal point construction, a conlcal concurrence of the reflected rays takes place, whereby in exceed.ing the receiving angle, the attenuated rays form a pointed angle toward an outer cover sheet, which would run parallel to the reflected ray 125. With -the pointed angle a high reflection portion of the attenuated rays is achieved as desired.
In order to achieve an even more pointed angle to an outer cover disc, and also to obtain a very flat design of the side wall 127, the side wall 127 is extended with another section 126~ which again is designed as a parabola with a focal point Fl in the end point of the opposite side wall. Because of the shifting of the focal point, a decrease in the size of tlle parabola is achieved, whereby the parabola section 126 becomes increasingly flat as a result of the decrease in size.
Due to the flattened condition of the parabola an increase is achieved in the opening width 128 of the cross section or the penetrating light.
An additional development of the invention provides for a type of lay-out, whereby the x-axes of the above-mentioned parabolas are positioned in such a way, that depending on -the irradiation angle ~, several peak values of the density of incoming energy are reached. This is shown in the diagram of Fig. 9. Thus, the irradiation angle B = 0 is fixed parallel to the collector axis 129 which runs vertically perpendicular to the concentration cross section area 124. The diagram represents the individual por-tions of the parabola sections Pl, P2 and P3. One can see that due to the parabola sections Pl and P2 a shading of the receiver cross section occurs at a 10W irradiation angle. Otherwise a steep curve increase and a very high concentration fac~or is already achieved at low irradiation angle.
The curve sections 130 and 131 are shown in broken lines, and indicates an additional energy recovery, which is achieved after non-utilisation of the reflector surfaces due to reflection on the outer irradiation opening cover. The diagram clearly indicates that the total energy recovery possible can be increased by using the reflection on the cover sheet.
While there is a continuous increase of the concentration Eactor up to a maximum value comparable with curve 132 as a result of parabola section P3 at a side wall design with one or more focal points but at equal sloping of the X-axis, whereas a progression of the peak value is achieved due to the different sloping of the X-axis. This can for example be utilized for heating purposes, in connection with a flat roof collector of the type shown in Fig. 7, to obtain the highest concsntra~ion factor at the lowest sun-position during the winter9 which factor then decreases in the summer at the higher , ~,.~,., '7~
~, ~3 ~
irradiation angles, ;ncrease in amount of sunshine and less need of heat.
The curve of Fig. 10 permits a recommendation to be made, regarding the layout of the reflector system shown in Fig.
8 and 9, as flat roof collector covers for heating purposes.
The curve 133 represents the cosine at Q diversified irradiation angle onto a horizontal surface. The curve 134 relates to the recovery of incoming rays inside the collector. The collector axis is sloped against the horizontal line in such a manner that at the lowest irradiation angle the incoming energy radiation in the collector is greater than the incoming energy radiation onto the horizontal surface. The incoming energy radiation then decreases ~ith increasing sun irradiation angle. The high concentration factor makes a small light penetration surface and a larger insulation surface of the panel feasible in the winter, according to the requirements of the high temperature difference, whereas as the reflectors are used for energy radiation and thus the cooling of the building to which they are applied during the SUDImer.
The wall panels which allow light to penetrate do not necessarily have to be designed level, and especially the outer panel wall can for example be designed arched or folded.
Preferred materials are glass or synthetics. The reflector 7~l profile strips can also be manufac-tured of glass or synthetics and can be metal coated by vaporization or galvanizing. Both processes for the production of a reflecting surface presen~ the possibility of providing the reflector protile strips with a certain amount of transparency.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A panel providing for the control of the transmission therethrough of incident light energy in accordance with the angle of incidence of the light energy thereon comprising two spaced light transmitting sheets constituting respectively a ray penetrating panel outer side and a ray emerging panel inner side and between which sheets are disposed a plurality of pairs of light impervious elements arranged parallel to and spaced from one another, wherein adjacent elements of successive pairs of light impervious elements form between themselves an ingoing irradiation cross-section and an outgoing emission cross-section.
characterised in that an upper side of a first light impervious element of a pair thereof is reflective and forms with an underside of a second light impervious element of a second pair, which underside is also reflective, a light energy concentration cross-section space disposed between the said ingoing irradiation and outgoing emission cross-sections, and that the contour of the said upper side of the said first element of a pair differs in curvature from that of the said underside of the said second element of a pair so that an energy irradiation density substantially independent of the light incidence angle is obtained.

2. A panel according to claim 1, characterised in that the panel constitutes an energy collector having energy receiver means disposed in the said concentration cross-section space.

3. A panel according to claim 1, characterised in that the underside of a first light impervious element and the upperside of a second light impervious element form with the panel edges a hollow space filled with a foamed material.

4. A panel according to any one of claims 1 to 3, characterised in that each light impervious element is located in the space between two spaced flange plates extending between the said two light transmitting sheets.

5. A panel according to any one of claims 1 to 3, characterised in that an energy receiver is integrated within the panel at the light energy concentration cross-section and that this energy receiver has a flow through passage for a heat exchange fluid.

6. A panel according to any one of claims 1 to 3, characterised in that an energy receiver comprising one or more photocells is integrated within the panel at the light energy concentration cross-section.

7. A panel according to any one of claims 1 to 3, characterised in that it includes an energy receiver that has energy incident thereon at the light energy concentration cross-section, on one side from the reflecting reverse side of an impervious element and on one side from a reflecting surface lateral to the receiver and that the location of the receiver and the design of the reflecting surfaces is such that the reflection at respectively the maximum and minimum angles of incoming rays meet the outer end points of the receiving surfaces and form tangents on the receiving surfaces.

8. A panel according to any one of claims 1 to 3, characterised in that a reflecting system constituted by the light impervious elements comprises a parabola and that the focal point F of the parabola is located in the area of the respective panel wall on the ray-penetrating side, and that another curved deflecting surface extends from the focal point F
of the parabola toward the inner space of the panel, whereby its center is located in the endpoint of the parabola-like reflecting surface, and that a further reflecting surface located towards the inner surface extends upwards from the endpoint of the parabola-like reflecting surface, and that the endpoint of the said further reflecting surface on the inner side of the panel space and the endpoint of the said another curved reflecting surface form a ray-penetrating cross-section to the inner panel space, and that an energy receiver is located in the upper area of the said ray-penetrating cross-section, and that the elements providing the surfaces as well as the receiver are disposed on the inner side of the panel space and are fastened to the respective wall panel on the inner side of the space.

9. A panel according to any one of claims 1 to 3, characterised in that the light wall panel comprises a glass-enclosed insolating element.

10. A panel according to any one of claims 1 to 3, characterised by two element surfaces located opposite each other, as a ray concentrating device, whereby one element is elongated in such a way that the rays incident on the lengthened part at a specific penetration angle .beta. are reflected to the opposite element surface and from there are reflected into the concentration cross-section.

11. A panel according to any one of claims 1 to 3, characterised by two element surfaces located opposite each other, as a ray concentrating device, whereby one element surface is elongated in such a way that the rays incident on the lengthened part at a specific penetration angle .beta. are reflected to the opposite element surface and from there are reflected into the concentration cross-section, and characterised in that the elongated element surface is lengthened by a part extending behind the concentration cross-section and that the end point of this part is located on a circular path around the end point in the concentration cross-section of an adjacent element, and that the intersection of two curves which both have a radius equal to the width of the concentration cross-section, and whose centers are located in the end points of the said element surfaces occurs at the last-mentioned end point, and that in the end point of such elongated element surface portion is located the center for a curve-like deflecting surface, which deflecting surface connects the end point of the opposite element surface with an inner wall panel.

12. A panel according to any one of claims 1 to 3, characterised in that a diffuser is positioned behind the concentration cross-section in extension of an element surface, and that this diffuser connects the concentration cross-section with the inner wall sheet, the diffuser being parabola-like, with the focal point F of the parabola positioned in the end point of the element surface that is located opposite to the diffuser, and that the axis as defined herein extends vertically to the inner wall sheet.

13. A panel according to any one of claims 1 to 3, characterised in that one side of one element is elongated in such a way that the rays incident on the elongated part at a specific penetration angle B are reflected to the opposite element and from there are reflected into the concentration cross-section, and also characterised in that the elongated side portion is of arched parabola shape, and that the focal point F2 thereof is located behind the opposite element.

14. A panel according to any one of claims 1 to 3, characterised in that one side of one element is elongated in such a way that the rays incident on the elongated part at a specific penetration angle B are reflected to the opposite element surface and from there are reflected into the concentration cross-section, and also characterised in that the elongated side part is of arched parabolic shape, and that the focal point F2 thereof is located behind the opposite element, and further characterised in that the said focal point F2 is located on a circular path around a focal point F3 of a first side curved element portion and that the radius of the curved element portion corresponds to the width of the concentration cross-section respectively, and that the opposite element is so formed that the focal point F2 is located at the end point of the first side curved element portion.

15. A panel according to any one of claims 1 to 3, characterised in that one side of one element is elongated in such a way that the rays incident on the elongated part at a specific penetration angle B are reflected to the opposite element surface and from there are reflected into the concentration cross-section, also characterised in that a primary or secondary part-elongation of said elongated part is of arched parabolic shape, and that the focal point F thereof is located in the end point of the opposite element, and is positioned in the ray-penetrating cross-section.