EP2664007A1

EP2664007A1 - A window

Info

Publication number: EP2664007A1
Application number: EP12707660.2A
Authority: EP
Inventors: Barak Freedman; Itay Baruchi; Alon Naim
Original assignee: PYTHAGORAS SOLAR Inc
Current assignee: PYTHAGORAS SOLAR Inc
Priority date: 2011-01-10
Filing date: 2012-01-10
Publication date: 2013-11-20
Also published as: CA2823677A1; BR112013017614A2; WO2012095847A1

Abstract

A window is provided comprising a front pane (12) and a rear pane (14) defining a space therebetween, and at least partially transparent liquid (26) disposed within the space. The liquid has a refractive index so close to that of the front pane that a majority of light impinging the front pane will pass therethrough into the liquid. A window further comprises at least one PV cell (18) disposed in the space so that at least a first portion of light that passes through the front pane into the liquid is directed to the PV cell, optionally by a light-ray separator (22) disposed with the space, for conversion of the first portion of light into electrical energy.

Description

A WINDOW

FIELD OF THE DISCLOSED SUBJECT MATTER

The presently disclosed subject matter relates to solar windows configured to generate electricity, especially those using optical elements to concentrate impinging solar radiation.

BACKGROUND OF THE DISCLOSED SUBJECT MATTER

It is well known that solar radiation can be utilized by various methods to produce useable energy. One method involves the use of a photovoltaic (PV) cell, which is configured to convert solar radiation into electricity. Solar radiation collectors are typically used to gather sunlight or other radiation and direct it toward a photovoltaic cell. Often, concentrators are provided in order to focus solar radiation impinging on an aperture having a certain area onto a PV cell having a smaller area, thus increasing the efficiency of the PV cell and reducing the cost thereof.

Often, a plurality of photovoltaic cells is provided to form a single module. This module may be formed with characteristics providing other benefits which are not necessarily related to energy production. For example, the module may allow some light to pass therethrough without being used for energy production. Such a module may be installed in a building and used as a window or skylight.

On the other hand, many contemporary office and public buildings make use of large glass windows and walls. These large area windows provide natural illumination inside the building during day time, and provide inhabitants with view outside, which may improve the working environment. The windows are usually double glazed providing the required thermal and acoustic isolation. In an effort to reduce air conditioning costs and in order to increase comfort, the windows may be designed to reduce the amount of direct sun radiation entering the building and/or may be equipped with curtains or Venetian blinds that can be adjusted to block such radiation.

The development of cost effective photo-voltaic systems brought a new dimension into the design of energy conserving buildings, allowing self-production of some of the electricity power consumption. In most buildings the window and wall areas are much larger than the roof area, thus being good candidates for the integration of solar photo-voltaic systems. However, such integration of the PV systems should not adversely affect the original purpose of windows and window walls (curtain walls).

It will be appreciated that herein references to windows also refers to solar skylights, and any reference to solar windows/curtain walls/blinds is also applicable to skylights.

SUMMARY OF THE DISCLOSED SUBJECT MATTER

According to one aspect of the present invention, there is provided a window comprising a front pane and a rear pane defining a space therebetween. At least partially transparent liquid disposed within said space, the liquid having a refractive index so close to that of the front pane that a majority of light impinging the front pane will pass therethrough into said liquid. At least one PV cell disposed in said space so that at least a first portion of light that passes through the front pane into the liquid is directed to the PV cell, optionally by a light-ray separator disposed within said space, for conversion of said first portion of light into electrical energy.

The liquid can have a refractive index of between 1.4 and 1.6.

The separator can be configured to direct the first portion to the PV cell by total internal reflection. The light-ray separator can be disposed in a first angle with respect to the front pane, the first angle is determined in such a way so that the first portion will be directed to the PV cell by total internal reflection. The light-ray separator can further include an adjusting mechanism for adjusting said first angle. By which the angle can be adjusted so as to determine the amount of light-rays to be directed to the PV cell.

The PV cell can be adjustably disposed in a second angle with respect to the separator, wherein the second angle can be adjusted so as to determine the desired viewing cone through the window. The light-ray separator can be configured to direct a second portion of the light ray toward the rear pane, the second portion being separate from the first portion.

The separator can be a beam splitter such as a partial transparent mirror. Alternatively, the separator can comprise a first transparent plate and a second transparent plate disposed adjacent one another and defining a gap therebetween. The gap can comprise medium having a refractive index smaller than that of the first plate thereby causing total internal reflection. The medium can be gas or air and the first and second plates can be sealingly affixed to one another solely along the perimeter thereof. The separator can be covered by the liquid, or the liquid can fill up the space.

The window can include a plurality of PV cells arranged an array and disposed along at least one dimension of the window perpendicular to the thickness thereof.

The light-ray separator can include a plurality of light ray separating units arranged in a separators array. The PV cell array can includes a plurality of PV cell arrays and the separators array can include a plurality of separators arrays, wherein the PV cell arrays are disposed one adjacent the other, and wherein each array being provided with at least one of the separator arrays for directing said first portion of light rays thereto.

The window can be provided with folding means for folding the PV cells thereby substantially precluding the light-rays from impinging thereon. In addition, the separator array can be provided with folding means for folding thereof thereby allowing substantially all the light-rays impinging on the front pane to travel toward the rear pane.

The window can further comprise an insulation layer for insulating the interior of the window form the exterior thereof, the insulation layer is disposed between rear pane and front pane. The insulation layer can be defined between a divider disposed in the space and the front pane or the rear pane, forming therebetween a cavity.

According to a further aspect of the present invention, there is provided a kit for a PV assembly for a double glazed window having a front and rear pane with a space therebetween. The kit comprising an array of PV cells configured to convert light rays to electrical energy, at least one light-ray separator; and means for mounting the array and the at least one light ray separator within the space at such orientation relative to each other and to said front pane so that only when the space comprises at least partially transparent liquid having a refractive index so close to that of the front pane that a majority of light impinging the front pane will pass therethrough into the liquid, at least a first portion of light that passes through the front pane into the liquid is directed by the separator to the PV for conversion thereof into electrical energy.

The separator can be configured to direct the first portion to the array by total internal reflection.

The means for mounting can be configured to allow disposing the light-ray separator in a first angle with respect to the front pane, the first angle is determined in such a way so that the at least a first portion will be directed to the array by total internal reflection. The means for mounting can be provided with an adjusting mechanism for adjusting the first angle. And, can be configured to allow disposing the array in a second angle with respect to the rear pane, the second angle is determined in accordance with a desired direction of a viewing cone through the rear pane. The adjusting mechanism can be further configured for adjusting the position of the array with respect to the rear pane.

The light-ray separator is configured to direct a second portion of the light ray toward the rear pane, the second portion being separate from the first portion.

The kit can be provided with folding means for folding the PV cell array thereby substantially precluding the light-rays from impinging thereon. The folding means can be configured for folding the separators, thereby allowing substantially all the light- rays to travel through the rear pane.

According to a further aspect of the present invention, there is provided a window comprising: at least a front pane, at least one PV cell disposed adjacent the front pane, a separator mounted adjacent said PV cell for directing toward the PV cell at least a first portion of light rays impinging on and passing through the front pane; and, at least partially transparent liquid disposed between the separator and the front pane, the liquid having a refractive index so close to that of the front pane that a majority of light impinging the front pane will pass therethrough into the liquid.

The window can further comprise a rear pane disposed adjacent the separator, wherein the liquid is further disposed between the separator and said rear pane.

According to still a further aspect of the present invention, there is provided a method for mounting a PV assembly in a double glazed window having a front and rear pane with a space therebetween, the method comprising: introducing into the space at least partially transparent liquid having a refractive index so close to that of the front pane that a majority of light impinging the front pane will pass therethrough into the liquid; and

disposing at least one PV cell in the space so that at least a first portion of light that passes through the front pane into the liquid is directed thereto for conversion thereof into electrical energy.

The method can further comprise disposing a light-ray separator adjacent the PV cell, the light-ray separator being configure for directing at least a first portion of light rays impinging on and passing through the front pane.

The method can further comprise determining the angle of the light ray separator with respect to the front pane in such a way so that the at least a first portion will be directed to the PV cell by total internal reflection. And can yet further comprise providing adjusting means for adjusting the angle of the light ray separator with respect to the front pane. And can comprise providing adjusting means for adjusting the angle of the light ray separator with respect to the front pane.

Herein the specification and claims, the term "concentration" refers to any level of concentration, including xl concentration (no concentration at all) or concentration levels < xl.

Herein the specification and claims, the term "transparent" is intended to include a fully transparent material, partially transparent material, or translucent martial allowing at least some EM wave length in the visible spectrum to travel through the material.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the presently disclosed subject matter and to see how it may be carried out in practice, embodiments will now be described, by way of non- limiting example only, with reference to the accompanying drawings, in which:

Fig. 1 is a side cross-sectional view of a window according to an example of the presently disclosed subject matter;

Fig. 2 are graphs designed to assist in selecting parameters of the window of in

Fig. 1;

Fig. 3A is a side cross-sectional view of a light-ray separator according to an example of the presently disclosed subject matter; Fig. 3B is a side cross-sectional view of a light-ray separator according to another example of the presently disclosed subject matter;

Fig. 3C is a side cross-sectional view of the light-ray separator of Fig. 4B mounted inside a double glazed window;

Fig. 4A is a side cross-sectional view of the window of Fig. 1 configured for a forward viewing cone;

Fig. 4B is a side cross-sectional view of the window of Fig. 1 configured for a downward viewing cone;

Fig. 5 is a side cross-sectional view of a window having an insulating cavity according to an example of the presently disclosed subject matter;

Fig. 6A is a side cross-sectional view of a window having a dynamic PV assembly according to an example of the presently disclosed subject matter;

Fig. 6B is a side cross-sectional view of the window of Fig. 6A in position configured for a downward viewing cone; and,

Fig. 6C is a side cross-sectional view of the window of Fig. 6A in the folded position.

Fig. 6D is a side perspective view of the window of Fig. 6A in the deployed position.

DETAILED DESCRIPTION OF EMBODIMENTS

As illustrated in Fig. 1, there is provided a photovoltaic (PV) window, which is generally indicated at 10. The window 10 comprises a front pane 12 constituting an exterior surface of the window, a rear pane 14 constituting a second exterior layer of the window. Front pane 12 and rear pane 14 defining a space 15 therebetween for mounting a PV assembly 16 therein, and for filling thereof with liquid 26.. The front pane 12 and the rear pane 14 define an outer surface 12a and 14a facing the outside of the building and the inside of the building respectively. In addition, each of the front pane 12 and the rear pane 14 define an inner surface 12b and 14b, respectfully, facing the PV assembly 16. The window 10 may be designed for mounting vertically or horizontally, as illustrated, or in any other suitable disposition. It will be appreciated by one skilled in the art the necessary design parameters to apply to any given design based on the description presented hereinbelow.

The window 10, and specifically the PV assembly 16 thereof, is designed so as to utilize solar radiation impinging on the front pane 12a at an angle within an acceptance angle θ_α for generation of electricity, and to allow passage therethrough of solar radiation impinging on the front pane 12 at an angle outside the acceptance angle. As will be described, the acceptance angle θ_α is calculated as a function of material and constructional properties of the PV assembly 16.

The rear pane 14 may be configured to diffuse radiation passing therethrough, thereby providing more uniform illumination using light impinging on the window 10 at an angle outside the acceptance angle θ_α.

The PV assembly 16 comprises at least one PV cell 18, which is designed to convert impinging solar radiation into electricity. The PV assembly 16 can further include a transparent or translucent light-ray separator 22, one side thereof disposed adjacent to one side of the PV cell 18 forming an angle therebetween, while the other side thereof is disposed adjacent the inner surface 12b of the front pane 12 and forming an angle a therebetween. The PV cell 18 extends between the inner surfaces 12b and 14b, in such a way so as to allow at least some of the light impinging on the front pane 12 and traveling therethrough to incident onto the PV cell, either directly or after being reflected by the separator 22.

The liquid 26 inside the space 15 is a transparent liquid which has a refractive index similar to a solid material, preferably in the range of 1.4-1.6, such as water. In addition preferably the transparent liquid material is characterized by viscosity which ranges from less than lcP (such as water) up to 250,000cP (such as hard silicone gel) which can be measured at 25° C according to ASTM D4283. This way the PV cells which can be immersed in the liquid are protected from damages caused by window vibrations, such that often occur in buildings. In addition, according to an example, utilizing liquid having viscosity which allows displacing the PV assembly immersed therein, allows dynamically adjusting the disposition of the PV assembly relative to the front and rear pane. According to one example the optical liquid is silicone based optical oil which can endure the high energy irradiation along the required life time of the product. The light-ray separator 22 is an optical components configured to direct a first portion of the light impinging thereon toward the rear pane and to direct a second portion of the light impinging thereon toward the PV cells 18. In one example the light separator is a partial transparent mirror, such as 80% reflecting 20% transmitting mirror. In this case the mirror reflects most of the impinging ray towards the PV cell 18, however, transmitting part of the light rays through the rear pane 14 into the room. This way, a viewer located inside the room can see through the window.

According to an alternative example the light-ray separator comprises a martial having a refractive index which is smaller than the one of the liquid 26 thereby causing the light rays impinging thereon in an angel which is larger than the critical angle to be totally reflected and not directed towards the rear pane 14. Examples of such a separator are explained in detail hereinafter with regards to Figs 3A through 3C. In this case, the angle a between the light-ray separator 22 and inner face 12b of front pane 12 is determined such that light rays entering the front pane 12 within a decried acceptance angle θ_α will be reflected via total internal reflection off of the light-ray separator 22 and the exterior surface 12a of the front pane 12. For a desired acceptance angle, which may be determined based on the location in which the window 10 is to be installed relative to the sun, the angle a between the light-ray separator 22 and inner face 12b is given as: α = θ„- sin -1 "cosft, " ( 1 1

= sin ^{1 f} cos

0„ - sin

n)

where n is the refractive index of the liquid 26 inside space 15. According to this formula, the acceptance angle θα, is the range of spatial angles of light-rays impinging on the front pane 12, in which theoretically all the light rays will reach the separator 22 at an angle greater than the critical angle thus will be totally reflected. This way the separator can be positioned with respect to the PV cells 18 in such a way so as to direct all the reflected light rays thereto. The above formula assumes that the refractive index of the liquid 26 is substantially the same as that of the front pane 12. In practice, however, the refractive index of the liquid 26 can be so close to that of the front pane 12 that at least the majority of light impinging the front pane 12 will pass therethrough into liquid 26. It is appreciated that small differences between the refractive indices of the liquid 26 and the front pane 12 do not change the principle of operation, although it might have a slight effect on the value of the acceptance angle (for a given a). As mentioned above, according to the illustrated example, light rays which impinges on the window 10 within the acceptance angle 0_a, for example along the path designated by 32, is reflected by the light-ray separator 22 toward the PV cell 18. Light which impinges on the window 10 outside the acceptance angle θ_α, for example along the path designated by 34, travels through the separator 22 and exits the window through the rear pane 14.

By selecting the appropriate disposition of the separator 22 with respect to the the PV cell 18 and the front pane 12, the amount of heat entering a room can be controlled. As shown in Fig. 2, which is explained hereinafter in detail, the acceptance angle 0_a may be selected such that all sunlight during the summer, or at least during the hottest part of the day, is reflected by the separator 22 toward the PV cell 18, thus reducing the solar heat load within the room, and all sunlight during the winter exits via the rear pane 14, thus increasing the solar heat load within the room. This arrangement will reduce the amount of cooling required during the summer, and decrease the amount of heating required during the winter, saving energy all year.

It is appreciated that the window 10 can include an array of PV cells 18 each provided with a light ray separator 22 concentrating at least some of the light ray onto the PV cells 18, the array of PV cells can be disposed along the length of the window and can include a plurality of arrays disposed along the height of the window 10. The distance between each array of PV cells can be determined in accordance with the amount of light rays which can be reflected from the separator thereto.

According to an alternative Example, the window can be formed with a plurality of window units, each having a front pane and a back pane, a PV cell mounted therebetween, and a separator for directing at least one a portion of the light rays impinging on the front pane and traveling therethrough toward the PV cell. Each cell is filled with a transparent liquid for allowing at least the majority of the light rays impinging on the front pane to reach the separator. The window units are organized in two dimensional array one next to the other forming together a window.

Reference is now made to Fig. 3A, the light-ray separator 50 includes a first and second plates 52a and 52b affixed to one another at the perimeter thereof, thereby forming a gap 54 therebetween. The first and second plates 52a and 52b are made of a transparent material, such as glass or plastic, etc. The gap 54 can be filled with material having a lower refractive index with respect to that of the plates 52a and 52b, such as air, thus allowing total internal reflection of light rays striking the boundary between the two mediums in an angle which is larger than the critical angle. It is appreciated that the above formula assumes that the material having lower refractive index with respect to the front pane and the liquid is air. Affixing the first and second plates 52a and 52b at the perimeter thereof is carried out by gluing or welding them to one another, in any known fashion. It is appreciated that the bond between the first and second plates 52a and 52b seals the gap 54 thus precluding liquid from entering therein. In order to preclude substantial optical losses due to the material of the glue or the welding material, the welding or gluing line is kept to the minimum.

According to one example the first and second plates 52a and 52b are thin foils of transparent optical material which can be for example thinner than 1mm, or according to another example in the range of 0.2-0.5mm. The foil can be made out of glass, plastic material such as PMMA, Poly-Carbonate, or Mylar (BoPET). Obtaining a sealed welding line along the perimeter of the two coupled foils can be obtained by laser welding, ultrasonic, heat or chemical welding.

According to one example the seperator is formed with a pair of glass based plates such as Borosilicate glass. In this case the two glass plates can be welded to one another using frit based welding or laser welding.

It is further appreciated that in order to allow the separator 50 to form the triangular space when disposed inside the double glazed window, it is formed with a rigid structure. This can be carried out by utilizing rigid plates, such as glass or plastic.

Alternatively, the separator can include two thin flexible transparent films affixed to one another at the perimeter thereof, thereby forming together an inflatable structure. When the inflatable structure is filled with air or gas under pressure the separator becomes rigid, and can be positioned at a desired angle with respect to the PV cell and the front pane.

Fig. 3B illustrates a light-ray separator according to another example, separator 60 includes a first and second plates 62a and 62b, having an air gap 64 therebetween. According to this example, at least one of the first and second plates 62a and 62b includes a spacer 66 at the perimeter thereof sealingly affixed to the perimeter of the other plate. Due to the spacer 66, the air gap 64 formed between the plates 62a and 62b is relatively large thereby ensuring the total internal reflection. It will be understood that the example of Fig. 3 a is best applied when the plates are made of glass thus, the air gap therebetween is maintained. However when the plates are made out of plastic, for example, due to slight distortion of the material the air gap might be maintained and thus total internal reflection might not occur.

As shown in Fig. 3C, the separator 60 is disposed between a front pane 72a and a rear pane 72b of a window 70, in an angle a and is immersed with liquid 78.

When a light ray 86 impinges the front pane 72a in an angle which is inside the acceptance angle , the light ray 86 travels through the liquid 78 and the first plate 62a until reaching the boundary between the first plate and the air gap 64. Since the light ray 86 entered the front pane 72a inside the acceptance angle, it reaches the boundary in an angle larger than the critical angle, thus since the refraction index of the air inside the air gap 64 is smaller than the refraction index of the plate 62a, - total internal refraction occurs. As a result, the light ray 86 is reflected back through the first plate 62a back into the liquid 78 until reaching the PV cell 74 where the light is converted to electric energy. It is appreciated that some of the light rays reflected by the separator may not reach the PV cell 74 directly, rather due to the low angle of incidence, may be directed back to the front pane 72a, (here illustrated for example as light ray 86a). However, due to the difference between the refractive index of the front pane 72a and that of the air outside the window 10, the light ray 86a will be totally reflected back into the liquid 78, until eventually reaching the PV cell 74.

On the other hand, when a light ray 88 impinges the front pane 72a in an angle which is outside the acceptance angle, the light ray 88 travels through the liquid 78 and the first plate 62a until reaching the boundary between the first plate and the air gap 64. This time, since the impinging angle at the boundary between the first plate and the air gap 64 is smaller than the critical angle, a total internal reflection does not occur. Thus, the light ray 88 travels through the air gap 64 the second plate 62b out through the rear pane 72b.

It will be appreciated that differences between the refractive indices of the first plate 62a and the air gap 64 may cause the light ray 88 passing therethrough to slightly deviate, in accordance with Snell's law. As a result, the image formed when looking through the window 70 from the side of the rear pane 72b may be distorted. However, since the light ray 88 than travels through the second plate 62b having a refractive index larger than that of the air inside the gap 64, thereby the light ray is shifted back to substantially its original path thus, allowing the formation of a clear image on the other side of the window 70.

Reference is now made to Figs. 4A and 4B, a PV assembly 36 having a first PV cell 38a and a second PV cell 38b disposed adjacent one another and between a front and rear pane 35a and 35b, having being liquid 37 therebetween. Each PV cell 38a and 38b is provided with a separator 39a and 39b disposed in an angle a with respect to the front pane 35a, and in an angle β with respect to the associated PV cell 38a and 38b, respectively. The PV cells 38a and 38b limit the viewing angle, as some of the entering rays of light are blocked by the surface of the PV cells 38a and 38b. As clearly shown in Fig. 4A, for a viewer 33, located relatively far from the window, the viewing cone 32 through two adjacent PV cells 38a and 38b is determined approximately by the far edges thereof. The direction of the viewing cone 32 is determined by a central ray 34, which extends perpendicular from the viewer's eye. Thus, if the viewer looks through the window in a straight line, the central ray 34 is perpendicular to the rear pane 35b. The viewing cone 32 in that case is limited by the first PV cell 38a disposed above the central ray 34 and the second PV cell 38b disposed below the central ray 34. If for example, the viewer looks downwardly, the image which he will see may include rays blocked by the edge of the PV cells 38a and 38b, and at this angle the viewer will not be able to see clearly through the window.

However, as shown in Fig. 4B the direction of central ray 34 and consequently of the viewing cone 32 can be controlled. This is carried out by tilting the PV cells 38a and 38b together with the respective separators 39a and 39b, thereby allowing a downwardly tilted viewing cone (looking down for a viewer looking from the left side of the window). It should be noted that while tilting the PV cell does not reduce the optical efficiency of the optical liquid elements, it does however change the level of concentration. That is to say, for a horizontally disposed PV cell the level of concentration is calculated as— -— where a is the angle between the separators 39a,

tan(or)

39b and the inner layer of the front pane 35a. When the PV cell 38a is tilted cosi/T) downwardly in an angle of β the concentration level is calculated as sin( ?)+—— .

tan(a)

It is appreciated that the window can include a stationary PV assembly, wherein the PV cell is disposed in an angle selected in accordance with the desired direction of the viewing cone. For example, for a window which is disposed in a high place allowing the viewer to look downwardly therethrough, the PV cells can be disposed in a downward slope (with respect to the viewer and the rear pane of the window) thereby forming a downwardly viewing cone. This way, the viewer can look through the window without the interference of the PV cells. On the other hand, when the window is configured to allow a viewer to look forward, the PV cells can be horizontally disposed thereby forming a straight forward viewing cone allowing the user to clearly see through the window when looking forward.

According to another example, the PV assembly can be a dynamic system allowing the viewing cone to be adjusted as desired. An Example of such system is described here in after with regards to Figs. 6A through 6C.

It is noted that normally a double glazed window is provided with a space in between, which is filled with air or other gas, providing a layer of insulation. However according to the presently disclosed subject matter the space between the front and rear pane contains the PV assembly which includes mostly optical liquid, dividers and PV cells, resulting in a high thermal conductively, thus compromising insulation.

During use, some of the solar radiation which reaches the array of PV cells is converted into electrical energy. However, a non-significant amount is converted into heat, raising the temperature of the cells. Depending on the design thereof, dependent on, inter alia, its construction and the materials it comprises, the separator may begin to undergo deformation at elevated temperatures, for example at temperatures above 90°C- 150°C. In addition, the efficiency of the PV cells decreases with increasing temperature. Thus, the window may comprise one or more heat dissipation arrangements, as described in WO 2011/048595. However, it is appricatead that the liquid inside the window can be configured to dissipate heat to the glass.

Fig. 5 shows a double glazed window 90 having a front pane 92a and a rear pane 92b and a PV assembly 94 disposed therebetween. According to this example, the double glazed window further includes an insulation layer for insulating the interior of the window form the exterior thereof. The insulation layer can be in the form of a cavity 96 defined between front pane 92a and a rear pane 92b containing air, gas, or vacuum for providing thermal and/or acoustical insulation. The cavity 96 is defined by one of the window's panes, here illustrated as the rear pane 92b and an intermediate divider 98. The intermediate divider 98 includes first face 98a defining the space for the PV assembly 94, and a second face 98b defining the cavity 96. Accordingly, the first face 98a serves as the inner surface of the rear pane of the previous examples, and is configured to hold the liquid and the PV assembly 94, as explained hereinabove with regards to Fig. 4C. It is appreciated that the divider 98 need not necessarily be glass and in fact in order to reduce both width and weight of the window 90, it may be made of any other transparent material. In addition, the divider 98 can includes a low emissivity coating for example on the inner surfaces thereof.

According to one example, the rear pane 92b and/or the front pane 92a are sealingly coupled to the divider 98 by means of frames 100a and 100b. Thus, frame 100a holds rear pane 92b on one side thereof and the divider 98 on the other side thereof, thereby defining the cavity 96. Frame 100b on the other hand, holds front pane 92b on one side thereof and the divider 98 on the other side thereof, whereby defining the end surface of the PV assembly. It is appreciated that the cavity 96 can alternatively be defined between the front pane 92a and the divider 96, and according to this example, the PV assembly can be mounted in between the divider 96 and the rear pane 92b were the liquid is held.

Frames 100a and 100b which can be made of aluminum, and which is attached to the front and rear panes as well as to the divider 98 with an adhesive material 102, such as Butyl adhesive, and can be further strengthened by a strong and elastic adhesive, such as Silicone based adhesive. The frame 100a can be perforated from inside and filled with desiccant material 104, so as to reduce the amount of humidity entering in between the panes 92a and 92b of the window 90 thereby increasing the product lifetime and the PV system durability. It will be understood that the use of the desiccant material 104 is relevant to the frame 100a holding the divider 98 and the rear pane 92b and defining cavity 96. The frame 100b which holds the PV assembly 94 contains the liquid therein, thus no humidity can enter inside.

Fig. 6A through 6D illustrates a double glazed window 110 having a front pane 112 and a rear pane 114, and a PV assembly 116 mounted therebweteen. PV assembly 116 according to this example is a dynamic system and is provided with an adjusting mechanism allowing the user to adjust the angle of the PV cells and/or the separators thereby adjusting the viewing cone of the viewer and the amount of light which can travel through the window. Adjusting the angle of the PV cells and the separators can be carried out by a single adjusting maechism or by two separated mechanisms. According to an example, the PV assembly 116 includes a plurality longitudianl PV arrays 118 each disposed along one dimension of the window 110, for example, its width, and comprises a plurality of PV cells. The PV arrays 118 according to this example are arranged one beneath the other such as Venetian blinds. The PV assembly 116 further includes a plurality of corresponding longitudinal separators 120 each associated with one PV cell or with one array of PV cell and configured for directing some light rays thereto as explained hereinabove with respect to the previous examples. The separators are disposed in an angle a with respect to the front pane 112, and in an angle β with respect to the associated PV array 118. The PV arrays and the separators are coupled to one another by means of a suspension cord 122, extending through an apertures 124 and 126 formed in each PV array 118 and each separator 120, respectively. The suspension cord 122 allows pulling the PV arrays together with their respective separators upwardly by reducing the distance between each adjacent PV array 118, and reducing angles a and β as shown in Fig, 6c. The suspension cord 122 can be provided with in any actuating mechanism (not shown) for example, a cord provided outside the rear pane 114 which by pulling thereof the PV assembly is folded upwardly, such as used for the folding of Venetian blinds. It is appreciated however, that in order to allow folding the PV array 118 and each separator 120, the space between the front pane 12 and the rear pane 14 may be adapted accordingly, so as to accommodate the separators even when horizontally disposed.

According to an example, the suspension cord can be further configured to electrically couple the PV arrays to one another.

According to one example, the PV assembly 116 is further provided with an adjusting mechanism (not shown) allowing the adjustment of angles a and β without the suspension of the PV arrays 118 and the separators 120. Adjusting the angles a and β can be carried out by adjusting cords, as used for adjusting the angle of Venetian blinds, which can be pulled to rotate each PV array 118 and the separators 120. Alternatively, an adjusting gearing system (not shown) can be provided at the side frame of the window holding the front and rear pane 112, and 114, to which the PV arrays and the separators are coupled. The gearing system can be activated to rotate the PV arrays and the separators as desired.

It is appreciated that the adjusting mechanism can be configured to allow adjusting either the angle a or the angle β, or both. This way, when for example the angle a is reduced the acceptance angle 0_a is reduced as well (in accordance with the abovementioned formula), thus less light ray will be reflected toward the PV cells resulting in more light entering the building. This can be carried out for example in the winter when more light and heat from the sun is desired.

On the other hand, changing the angle β allows changing the direction of the viewing cone and the field of vision, as explained hereinabove with regards to Figs. 4A and 4B.

Fig. 2 provides an example of how an appropriate acceptance angle θ_α may be selected. Based on the latitude at which the window 10 will be installed, the maximum zenith angle (i.e., the largest angle from the vertical which the sun will make over the course of the year) is found. If "all year shading" is desired, i.e., if no direct sunlight should be admitted via the window, the acceptance angle θ_α should be chosen to be equal to the extreme zenith angle (bearing in mind that sunlight impinging within the acceptance angle is accepted by the PV cell 18, and does not pass through the window). If "adaptive shading" is desired, i.e., if direct sunlight should be admitted only when the sun is at lower elevations, for example during the winter or morning and afternoons/evening during the summer, the acceptance angle 0_a should be chosen to be somewhat lower than the extreme zenith angle. In such a case, the lower the acceptance angle, the more sunlight will be admitted via the window 10.

Those skilled in the art to which the presently disclosed subject matter pertains will readily appreciate that numerous changes, variations, and modifications can be made without departing from the scope of the invention, mutatis mutandis.

Claims

CLAIMS:

1) A window comprising:

a front pane and a rear pane defining a space therebetween;

at least partially transparent liquid disposed within said space, the liquid having a refractive index so close to that of the front pane that a majority of light impinging the front pane will pass therethrough into said liquid; and

at least one PV cell disposed in said space so that at least a first portion of light that passes through the front pane into the liquid is directed to said PV cell, optionally by a light-ray separator disposed with said space, for conversion of said first portion of light into electrical energy.

2) The window according to claim 1 wherein said liquid having a refractive index of between 1.4 and 1.6.

3) The window according to claim 1 wherein said separator is configured to direct said first portion to said PV cell by total internal reflection.

4) The window according to claim 3, wherein said light-ray separator is disposed at a first angle with respect to the front pane, said first angle being determined in such a way that at least said first portion of light will be directed to said PV cell by total internal reflection.

5) The window according to claim 4, further comprising a first adjusting mechanism for adjusting said first angle.

6) The window according to claim 5, wherein said adjusting mechanism is configured to adjust said first angle in accordance with the desired amount of light to be directed to said PV cell.

7) The window according to any one of claims 1 to 4, further comprising a second adjusting mechanism for adjusting a a second angle defined by the PV cell with respect to said separator.

8) The window according to claim 7, wherein said second adjusting mechanism is configured to adjust said second angle in accordance with a desired viewing cone through the window. 9) The window according to claim 1 wherein said light-ray separator is configured to pass therethrough a second portion of the light different from said first portion toward said rear pane.

10) The window according to claim 1 wherein said separator is a beam splitter, particularly, a partially transparent mirror.

11) The window according to claim 3 wherein said separator comprises a first transparent plate and a second transparent plate disposed adjacent one another and defining a gap therebetween.

12) The window of Claims 11 wherein said gap comprises a medium having a refractive index smaller than that of said first plate thereby causing said total internal reflection.

13) The window according to claim 11 wherein said medium is gas or air.

14) The window according to any one of claims 11 through 13 wherein said first and second plates are sealingly affixed to one another solely along the perimeter thereof.

15) The window of Claim 1 and 27 wherein at least the separator is covered by said liquid.

16) The window according to claim 15 wherein said PV cell is covered by said liquid.

17) The window according to claim 1 wherein the liquid fills up said space.

18) The window according to any one of the preceding claims, wherein said at least one PV cell includes a plurality of PV cells arranged in a PV cells array and disposed along at least one dimension of the window perpendicular to the thickness thereof.

19) The window according to claim 18 wherein said light-ray separator includes a plurality of light ray separating units arranged in a separators array.

20) The window according to claim 19 wherein said PV cell array includes a plurality of PV cell arrays and said separators array includes a plurality of separators arrays, wherein said PV cell arrays are disposed one adjacent the other, and wherein each array being provided with at least one of said separator arrays for directing said first portion of light rays thereto.

21) The window according to claim 20 wherein said PV cells array is provided with folding means for folding thereof along at least one direction, thereby substantially precluding the light-rays from impinging thereon, when desired. 22) The window according to claim 20 wherein said separator array is provided with folding means for folding thereof at least in one direction, thereby allowing substantially all the light impinging on said front pane to pass through said space toward said rear pane.

23) The window according to claim 21 wherein said folding means are further configured for folding said separator array, optionally simultaneously with the PV cells array.

24) The window according to any of the proceeding claims further comprising an insulation layer for insulating the interior of the window form the exterior thereof, said insulation layer is disposed between rear pane and front pane.

25) The window according to claim 24 wherein said insulation layer is defined between a divider disposed in said space and said front pane or said rear pane, forming therebetween a cavity.

26) The window according to claim 24 wherein said cavity contains gas.

27) A kit for a PV assembly for a double glazed window having a front and rear pane with a space therebetween, the kit comprising:

an array of PV cells configured to convert light to electrical energy;

at least one light-ray separator; and,

means for mounting said array and said at least one light separator within said space at such orientation relative to each other and to said front pane that, only when said space comprises at least partially transparent liquid at least a first portion of light that passes through the front pane into said space is directed by said separator to said PV cells for conversion thereof into electrical energy, said liquid having a refractive index so close to that of the front pane that a majority of light impinging the front pane will pass therethrough into said liquid.

28) The kit of Claim 27 wherein said separator is configured to direct, when in said liquid, said first portion of light to said array by total internal reflection.

29) The kit according to claim 28, wherein said means for mounting are configured to allow disposing said light-ray separator at a first angle with respect to the front pane, said first angle being determined in such a way so that said at least a first portion will be directed to said array by total internal reflection.

30) The kit according to claim 29, wherein said means for mounting are provided with a first adjusting mechanism for adjusting said first angle. 31) The kit according to claim 28, wherein said means for mounting are configured to allow disposing said array in a second angle with respect to the rear pane, said second angle is determined in accordance with a desired direction of a viewing cone through said rear pane.

32) The kit according to claim 30 or 31, wherein said adjusting mechanism is further configured for adjusting the position of said array with respect to the rear pane.

33) The kit according to any one of claims 31 or 32, wherein said means for mounting are provided with a second adjusting mechanism for adjusting said second angle.

34) The kit according to claims 27 wherein said light-ray separator is configured to pass therethrough a second portion of the light different from said first portion toward said rear pane.

35) The kit according to any one of the preceding claims, wherein said array is disposed along at least one dimension of the window perpendicular to the thickness thereof.

36) The kit according to claim 35 wherein said light-ray separator includes a plurality of light ray separating units arranged in a separators array.

37) The kit according to claim 36 wherein said array includes a plurality of PV cell arrays and said separators array includes a plurality of separators arrays, wherein said PV cell arrays are disposed one adjacent the other, and wherein each array being provided with at least one of said separator arrays for directing said first portion of light rays thereto.

38) The kit according to any one of claims 27 to 37 wherein said array is provided with folding means for folding thereof along at least one direction, thereby substantially precluding the light-rays from impinging thereon, when desired.

39) The kit according to claim 36 wherein said separator array is provided with folding means for folding thereof at least in one direction thereby allowing substantially all the light-rays to pass through said space toward said rear pane.

40) The kit according to claim 38 when depending from claims 38 or 39, wherein said folding means are configured to fold said separator array optionally simultaneously with said array.

41) A window comprising:

at least a front pane; at least one PV cell disposed adjacent said front pane;

a separator mounted adjacent said PV cell for directing toward said PV cell at least a first portion of light impinging on and passing through said front pane; and, at least partially transparent liquid disposed between said separator and said front pane, the liquid having a refractive index so close to that of said front pane that a majority of light impinging the front pane will pass therethrough into said liquid.

42) The window according to any one of claims 27 and 41 wherein said liquid having a refractive index of between 1.4 and 1.6.

43) The window according to any one of claims 27 and 41 wherein said separator is configured to direct said first portion to said PV cell by total internal reflection.

44) The window according to any one of claims 27, 34 and 43 wherein said separator is a beam splitter, particularly, a partially transparent mirror.

45) The window according to any one of claims 28, 34, 43 wherein said separator comprises a first transparent plate and a second transparent plate disposed adjacent one another and defining a gap therebetween.

46) The window of Claims 45 wherein said gap comprises a medium having a refractive index smaller than that of said first plate thereby causing said total internal reflection.

47) The window according to claims 45 wherein said medium is gas or air.

48) The window according to any one of claims 45 through 47 wherein said first and second plates are sealingly affixed to one another solely along the perimeter thereof.

49) The window according to claim 41 further comprising a rear pane disposed adjacent said separator, wherein said liquid is further disposed between said separator and said rear pane.

50) The window according to claims 41 wherein said light-ray separator is configured to allow a second portion of the light ray different from said first portion to pass theretrough.

51) The window according to any one of claims 41 to 43 wherein the liquid fills up the space between said separator and said front pane.

52) The window according to any one of the claims 41 to 44, wherein said at least one PV cells includes a plurality of PV cells arranged in a PV cells array and disposed along the width of the window. 53) The window according to claim 45 wherein said light-ray separator includes a plurality of light ray separating units arranged in a separators array.

54) The window according to Claim 46 wherein said PV cell array and said PV cells array and said separators array are two dimensional arrays.

55) A method for mounting a PV assembly in a double glazed window having a front and rear pane with a space therebetween, the method comprising:

introducing into said space at least partially transparent liquid having a refractive index so close to that of the front pane that a majority of light impinging the front pane will pass therethrough into said liquid; and

disposing at least one PV cell in said space so that at least a first portion of light that passes through the front pane into said liquid is directed to said PV cell for conversion thereof into electrical energy.

56) The method of claim 55 wherein said liquid having a refractive index of between 1.4 and 1.6.

57) The method of claim 55 further comprising disposing a light-ray separator adjacent said PV cell, said light-ray separator being configure for directing at least a first portion of light rays impinging on and passing through said front pane.

58) The method of claim 57 wherein said separator is configured to direct said first portion to said PV cell by total internal reflection.

59) The method of claim 57, further comprising determining the angle of said light ray separator with respect to the front pane in such a way so that at least said first portion of light will be directed to said PV cell by total internal reflection.

60) The method of claim 57, further comprising providing adjusting means for adjusting the angle of said light ray separator with respect to the front pane.

61) The method of claim 55, further comprising providing adjusting means for adjusting the angle of said light PV cell with respect to the front pane.

62) The method of any one of the preceding claims wherein said light-ray separator is configured to pass therethrough a second portion of the light ray different from said first portion , toward said rear pane.

63) The method of wherein said separator comprises a first transparent plate and a second transparent plate disposed adjacent one another and defining a gap theirbetween.