WO2011114328A2

WO2011114328A2 - Passive electromagnetic radiation collector

Info

Publication number: WO2011114328A2
Application number: PCT/IL2011/000249
Authority: WO
Inventors: Yosef Levy
Original assignee: Power And Sun Technologies Ltd.
Priority date: 2010-03-15
Filing date: 2011-03-15
Publication date: 2011-09-22
Also published as: WO2011114328A3

Abstract

A passive electromagnetic radiation collector is presented for use with a radiation converter. The radiation collector comprises at least one basic block. The basic block of the collector is substantially transparent to the electromagnetic radiation and has spaced-apart first and second surfaces, by which the basic block when in operation is exposed to a source of the electromagnetic radiation and faces the radiation converter respectively. The first surface of the basic block has a dome-shaped configuration of a predetermined curvature. The second surface of the basic block is formed by refractive interfaces defining an apex structure aligned with an uppermost region of the dome, and sloping downward toward edges of the block, such that the refractive interface directs at least a part of radiation collected by the first surface onto a region outside the basic block on a plane spaced apart from the second surface, thereby enabling interaction of the at least part of the collected radiation with a corresponding region of a radiation sensitive surface of the radiation converter located in the plane.

Description

PASSIVE ELECTROMAGNETIC RADIATION COLLECTOR

FIELD OF THE INVENTION

This invention relates to passive electromagnetic radiation collectors, and particularly, but not exclusively, to passive solar collectors used for directing sunlight toward a solar energy converter. BACKGROUND OF THE INVENTION

In general, solar collectors direct solar light toward a target area. The target area may be, for example, a solar energy converter (such as a photovoltaic panel or a heat exchanger pipe), or a daylighting system (e.g. window) for illuminating the interior of a building.

The solar collectors are generally of two types: active and passive. An active solar collector uses a mechanism for moving either the target or light deflectors associated with the target to track the Sun's position (e.g. via a tracking mechanism), in order to provide the target with increased exposure to sunlight. A passive solar collector, in contrast, employs a fixed device exposed to sunlight for collecting sunlight and directing it toward a target.

US Patent 4,299,201 discloses hollow solar focusing means having a semi- cylindrical or arcuate shape, the surface of which has such fine menisci as to act like convex lenses to focus solar rays towards the center of the focusing body where a solar energy conversion device is located, irrespective of the position of the sun. The surface of the focusing means further acts to disperse light reflected thereonto from the solar energy conversion device.

US Patent 5,444,606 discloses a combination of a prismatic reflector and a prismatic lens for use with lighting fixtures. A reflector body has a substantially parabolic contour defining an interior cavity. The reflector body includes a plurality of prisms for receiving, transmitting and reflecting light. A lens body has a first mating surface engaging the reflector body, an opposed inverted conical surface, and a sloping sidewall extending between the mating surface and the opposed inverted conical surface. The mating surface of the lens body has a larger diameter than the opposed inverted conical surface. The opposed inverted conical surface includes a plurality of prisms for receiving and for redirecting light.

US Patent 5,648,873 discloses an apparatus designed to direct daylight through an aperture toward a target area in a building or other structure. A housing provides a base attachable to the building and a support structure for supporting a reflector above the aperture. Optionally, the reflector is in the shape of an inverted cone. A light diffusing lens structure is disposed in the optical path between the reflector and the target area. In use, light is transmitted through the support structure, reflected from the surface of the reflector, and dispersed about the target area by the light diffusing lens structure.

GENERAL DESCRIPTION

The present invention relates to a passive electromagnetic radiation collector designed for being located above a target (such as a single-cell or a multi-cell arrangement of solar energy convertors), at a certain distance therefrom, and for directing at least a part of the collected radiation toward the target.

The radiation collector of the invention is a passive one, and has a geometrical configuration and other structural characteristics (material composition, distance from the target plane, etc.) designed for maximizing the collectors' capability during the sun's movement along its day-night trajectory. It should be noted that although the collector of the invention may be advantageously used in a passive radiation collection system, it can be used also with an active system, e.g. where the radiation converter panel is movable along the sun's winter-summer trajectory.

The radiation collector is substantially transparent to the electromagnetic radiation of interest (such as sunlight), and has at least one basic block, the basic block defining outer and inner spaced-apart surfaces with a transparent medium therebetween. The outer surface of the block is that by which the radiation collector is exposed to electromagnetic radiation, and the inner surface is that by which the collector faces the target. The outer surface is dome-like shaped and is thus capable of collecting radiation beams coming from a variety of angles (i.e. defines a wide solid angle of collection of the radiation collector). The inner surface includes one or more refractive interfaces forming an apex structure having a cross-section shaped like an inverted V. A combination of the dome-like outer surface and the inverted V-shape cross section of the inner-surface structure provides that a significant amount of radiation collected by the outer surface, irrespective of the current position of major directions of propagation of the electromagnetic radiation (e.g. irrespective of the sun's current location along the day-night trajectory), is directed towards the target by refraction through at least one of the interfaces of the inner surface.

The inner surface may include a single pair of planar interfaces (thus defining a single V-shape section), or a plurality of pairs of planar interfaces (two or more pairs defining mutually perpendicular V-shape sections). In yet another embodiment, the inner surface is a conically-shaped interface (i.e. is curved to define a conical surface).

The dome-shaped outer (first) surface enables to increase the solid angle of collection. The dome-shaped surface and the inner surface, and also a distance between them are configured to appropriately apply refraction effects to incident radiation, thus enabling the collector to redirect radiation rays towards the target, while the original direction of propagation of the rays would not intersect the target or would not reach the target at proper angles for the target's use, e.g. would reach the solar converter at grazing angles, thereby causing more reflection from the converter than absorption. The provision of the inverted V-shaped refractor at the inner (second) surface allows for decreasing the angle of incidence between the radiation traveling within the medium of the collector and its output surface (the refractive interface). By decreasing such incidence angle, the effect of total internal reflection at the output surface could be avoided, and accordingly a higher amount of radiation is output from the collector towards the target via refraction at the inner surface of the collector.

As indicated above, the radiation collector of the invention can be designed to be used with any specific radiation receiver. More specifically, the invention is used with a radiation converter, such as a photovoltaic cell arrangement, and is therefore exemplified below with respect to this specific, but not limiting, embodiment. The basic block of the radiation collector of the invention may be designed for directing light onto a single-cell radiation converter or onto a multi-cell radiation converter.

Thus, the radiation collector of the present invention can advantageously be used with a radiation converter such as a solar energy converter, in a passive light collection and conversion system. The collector is passive, i.e. is placed in a fixed position with respect to the converter, and extends in a plane substantially parallel to the radiation sensitive surface of the converter. In this connection, it should be understood that in various applications there is a need for orienting a radiation converter such that its light sensitive surface is appropriately tilted with respect to the horizontal plane. For example, in the field of solar energy conversion, the orientation might be such that the light sensitive surface of a converter (solar panel) is tilted towards the south direction. Hence, the entire system, formed by a converter and its associated collector, might be appropriately tilted to ensure that the light sensitive surface, and accordingly the plane defined by the collector, is tilted with respect to the horizontal plane.

As indicated above, the basic block of the collector of the present invention has an inner surface defined by refractive interfaces formed by at least one pair of facets tilted with respect to one another and defining together an apex structure having a V- shaped cross section. In the simplest example of a dome-like outer surface in the form of a portion of a sphere or the like, each such interface may have a triangle-like geometry. Generally, the collector block of the invention is oriented with respect to the associated radiation sensitive surface (i.e. the surface covered by the collector block) such that the top portion of the block (defined by the highest point on the dome-like outer surface and aligned therewith apex at the inner surface) is vertically aligned with a central part of the radiation sensitive surface. Also, when the collector is put in operation, the configuration is such that the facets of the paired interfaces are facing two opposite sides of the trajectory of movement of the radiation source (e.g. the sun's day- night trajectory, i.e. east-west trajectory). The inner surface of the collector formed by said refractive interfaces is appropriately distanced from the light sensitive surface of the converter.

The collector of the present invention has a relatively simple design fashioned for improving the power output of an associated solar collector, without the need for intricate lens geometry. Furthermore, the collector of the present invention is mostly insensitive to optical aberrations, since it does not aim to precisely focus light into a predetermined spot. Therefore, the collector of the present invention is relatively easy and inexpensive to manufacture.

Thus, according to one broad aspect of the invention, there is provided a passive electromagnetic radiation collector for use with a radiation converter, the collector comprising at least one basic block, wherein the basic block of the collector is substantially transparent to the electromagnetic radiation and has spaced-apart first and second surfaces, by which the basic block when in operation is exposed to a source of the electromagnetic radiation and faces the radiation converter respectively;

the first surface of the basic block has a dome-shaped configuration of a predetermined curvature; the second surface of the basic block is formed by refractive interfaces defining an apex structure aligned with an uppermost region of the dome, and sloping downward toward edges of the block, such that the refractive interface directs at least a part of radiation collected by the first surface onto a region outside the basic block on a plane spaced apart from the second surface, thereby enabling interaction of at least part of the collected radiation with a corresponding region of a radiation sensitive surface of the radiation converter located in the plane.

The apex structure of the basic block is configured to define a certain predetermined angle selected in accordance with a trajectory of movement of the source of electromagnetic radiation. For example, in some applications, in particular for solar radiation collection, the apex structure defines an angle in a range between 120 degrees and 160 degrees.

In some embodiments, a dimension of a projection of the dome-like surface onto the plane is substantially equal to or larger than a corresponding dimension of a radiation converting surface of the radiation converter.

In some embodiments, the dome-like surface has a cross section being a segment of a circle of a predetermined radius.

For example, the dome-like surface is a part of a sphere. The second surface may include one or more pairs of the refractive interfaces, in which case the refractive interfaces may be substantially planar and the interfaces of each pair define an angular configuration (apex structure). Alternatively, the second surface is a conical surface.

In another example, the dome-like surface is a part of a cylinder. The second surface may include a single pair of the refractive interfaces which are substantially planar and define the apex structure.

The radiation collector may be configured for collecting solar radiation and directing it to a solar energy converter having a substantially planar radiation converting surface. As indicated above, the apex structure preferably defines an angle in a range between 120 degrees and 160 degrees. The dimension of the radiation converting surface may for example be about 5 inches, while a dimension of a projection of the dome-like surface onto a plane of the radiation converting surface is about 5.5 inches. The region upon which the collected radiation is directed may have a dimension of about 2-3 inches. The region upon which

5 the collected radiation is directed may be located substantially at a central part of a surface portion on the plane defined by the projection of the dome-like surface. The radiation collector may be capable of directing at least part of the collected radiation onto the region, while the radiation collector is located at a distance of about 4-5 inches from the region. The curvature of the dome-like surface may have a radius of about 8-

10 10 inches.

The radiation collector may comprise an array of the above-described basic blocks. Each of the basic blocks may be configured for directing the collected radiation onto a single or multiple radiation converters.

According to another broad aspect of the invention, there is provided a system

15 comprising an electromagnetic radiation converter having a substantially planar radiation sensitive surface; and an electromagnetic radiation collector stationary mounted above the radiation sensitive surface, the radiation collector being substantially transparent to the electromagnetic radiation and comprising at least one basic block which has spaced-apart first and second surfaces exposed respectively to an 0 electromagnetic radiation source and at least a portion of the radiation sensitive surface of the radiation converter, the first surface having a dome-shaped configuration of a predetermined curvature, the second surface being formed by refractive interfaces defining an apex structure aligned with an uppermost region of the dome and sloping downward toward edges of the collector, such that the refractive interface directs at least 5 a part of radiation collected by the first surface onto a region of the radiation sensitive surface.

According to yet a further aspect of the invention, there is provided a solar energy convention system comprising a panel carrying an array of solar energy converting cells arranged in a spaced-apart relationship along at least one axis, and a passive0 electromagnetic radiation collector stationary mounted with respect to the panel, the radiation collector comprising an array of connected to one another basic blocks, wherein the basic block is substantially transparent to the electromagnetic radiation and has spaced-apart first and second surfaces, by which the basic block when in operation is exposed to a source of the electromagnetic radiation and to the panel respectively, the first surface of the basic block having a dome-shaped configuration of a predetermined curvature, the second surface of the basic block being formed by one or more refractive interfaces defining an apex structure aligned with an uppermost region of the dome, and sloping downward toward edges of the block, such that the refractive interface directs at least a part of radiation collected by the first surface onto a region onto a plane spaced apart from the second surface, thereby enabling interaction of the at least part of the collected radiation with a corresponding region of the radiation converter located on the plane. BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention 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:

Figs. 1-3 are schematic drawings, illustrating the configuration of a basic block of a radiation collector of the invention, and also showing operation of the collector for collecting solar energy at different times of the day;

Fig. 4 is a schematic drawing illustrating the operation of the collector of the present invention throughout the daytime hours;

Figs. 5a-5d are bottom views of the inner surface of the collector's basic block in different embodiments of the present invention;

Fig. 6 is a perspective view of a collector according to the example of the invention, having a dome-like outer surface shaped like a portion of a sphere, being used with a multi-cell solar energy converter;

Fig. 7 is a perspective view of a basic block of a single- or multi-block collector according to the example of the invention, where the collector/block is elongated having a dome-like outer surface shaped like a portion of a cylinder;

Fig. 8 is a cross sectional view of a part of the collector according to an embodiment of the present invention, where multiple basic blocks are joined together side by side, for use with a solar panel (multi-cell solar energy converter), where each basic block may for example be associated with a single solar cell or a single column of cells; Figs. 9A and 9B illustrate a collector (basic block) prepared for use in an experimental setup;

Fig. 9C is a schematic illustration of an experimental setup designed for testing the effect of the collector of Figs. 9A-9B of the present invention on the current output generated by a solar energy converter cell and on the temperature of the cell;

Fig. 10 is a graph generated by measurements effected via the setup of Fig. 9C, the graph illustrating a comparison between the time profile of the electrical current produced by a solar cell associated with a collector of the present invention and the time profile of the electrical current produced by a solar cell having no such collector; and Fig. 11 is a graph generated by measurements effected via the setup of Fig. 9C, the graph illustrating the performance increase of a solar cell caused by the association of the solar cell with the collector of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Referring now to the figures, Figs. 1-3 are schematic drawings, which exemplify an electromagnetic radiation collector of the present invention, and which illustrate the operation of the collector at different time periods during the day.

The electromagnetic radiation collector of the invention is formed by one or more basic blocks, a single basic block 100 being shown in the present examples. The collector block is optically transparent for radiation range to be converted, and thus includes appropriate medium 101 enclosed between or defining opposite surfaces of the block 100: an outer (first) surface 102 intended for facing the radiation source (such as the sun, for example) and an inner (second) surface 104 intended for facing a target 106, such as a solar photovoltaic cell.

The outer surface 102 is substantially dome-like shaped thus defining a very wide solid angle of light collection, i.e. it collects, via refraction, the radiation beams coming from a variety of angles. As will be described more specifically further below, in some embodiments of the present invention, the dome-like surface has a circular- segment circumference having a predetermined radius of curvature; the dome-like surface may thus be a part of a sphere-like body or a cylinder-like body. However, the dome-like configuration may have other shapes, e.g. having a flatter profile or a more curved profile. The inner surface 104 is formed by one or more refractive interfaces forming generally an apex structure formed by two or more intersecting facets. Generally, the apex structure is such that it divides the inner surface of the converter block into two substantially symmetrically identical portions. By orienting the converter block such that the axis of symmetry of the inner surface passes substantially through a center of the trajectory of movement of the radiation source (the sun's day-night trajectory), the optimal solid angle of collection for radiation during such movement is provided. The cross section of a structure formed by the refractive interfaces is preferably shaped like an inverted V or wedge.

As shown in the figure, the inner surface 104 is shaped like an apex having a first facet 104a and a second facet 104b intersecting to define an angle 108, and sloping downward from the top of the angle. In some embodiments of the invention, the facets 104a and 104b are substantially planar; these may be two different planar interfaces tilted with respect to one another (e.g. symmetrically identical). In some other embodiments, such facets 104a and 104b (e.g. symmetrically identical) may be parts of a conical surface. These will be described more in detail further below with reference to Figs. 5a-5d, 6 and 7. The use of the inverted V-shaped refracting inner surface 104 allows for decreasing the angle of incidence between the collected radiation, propagating from the outer surface to the inner surface through the medium 101, and the inner surface 104, being the output surface of the collector block 100. By decreasing such incidence angle, the effect of total internal reflection at the output surface could be avoided for most of the collected radiation. As a result, the amount of radiation output from the collector towards the target via refraction at the inner surface of the collector is increased.

Transparency of the medium 101 to the electromagnetic radiation of interest is important for achieving improved radiation collection. If the collector block 100 is used for solar energy collection, the medium 101 is made of highly transparent material, such as amorphous plastic, Poly-Carbonate, Perspex, epoxy, glass and the like. Additionally, the medium 101 is preferably formed of a heat resistant material for durability. In a non- limiting example, the medium 101 is a heat resistant two-component epoxy (for example Crystal Epoxy, commercially available from Honig - Colors for Art Ltd., Moshav Ginaton, Israel). When a radiation source is not stationary (moves), such as the sun, the number of refractive interfaces of the inner surface 104 of the collector block is chosen in accordance with the diurnal movement of the radiation source. If the target is a solar energy converter, it might be associated with a stationary mounted target carrier or may be mounted on a movable object such as a vehicle. For example, the collector block 100 having two interfaces, each defining one of the facets 104a and 104b, is more suitable for use with a stationary solar power station or residential site having one or more fixed solar converters. Preferably, when the collector is put in operation it is oriented such that one facet 104a is positioned on the west side and the other facet 104b is positioned on the east side. Thus, the collector block 100 effectively collects and directs radiation to the target for the entire duration of the diurnal movement of the sun.

When dealing with a movable target (e.g. a solar energy converter mounted on a car), it might be preferable to use a collector block having multiple pairs of interfaces (generally at least two pairs), each defining a V-shaped cross section. This configuration is useful for directing solar radiation that may come from a variety of angles, for example for implementation with portable/mobile solar energy converters. Examples of such a mobile solar energy converter include a solar energy converter joined to a vehicle for powering an electric powered automobile, or a solar energy converter powering a portable charger for electronic devices (phones, laptop computers, etc).

The magnitude of angle 108 formed by the intersecting refractive interfaces

(facets) defines the capacity of the collector block 100 and is appropriately selected to increase the power output of the electromagnetic radiation converter as a function of the collected absorbed energy which in turn depends on the position of the sun in the sky. Accordingly, effective light collection early in the morning and near the end of the day may be provided with relatively smaller angle 108 in the collector block 100, for example about 120 degrees (or possibly lower), because with such relatively small angle at the inner surface light rays incident on the outer surface from a direction substantially parallel or at a very small angle to the ground, would most probably not totally be internally reflected by the angled interfaces of the inner surface 104. On the other hand, effective light collection around midday is provided when the angle 108 is relatively large (e.g. 160 degrees or even larger). Hence, for effective solar energy collection throughout a full day, an angle 108 within the range 120-160 degrees is preferable. As also shown in the figures, the angled structure 108 preferably extends until the edges of the block 100. A length 112 of a projection of the dome-like outer surface 102 onto a target plane (a plane of location of the radiation converting surface of the target 106) is equal to or larger than a corresponding dimension 114 of the radiation converting surface of the target. Generally, the larger the projection as compared to the associated radiation converting surface, the better the converter performance. However, practically, based on the existing arrangements of solar cell panels and existing manufacturing techniques, the projection can be slightly larger than the radiation converting surface aligned with (covered by) the collector block. With the collector block configuration of the invention, almost all the light rays emerging from the block 100 would be incident onto the target. The configuration can be such that the output radiation is concentrated substantially at the central region of the target. This configuration is advantageous for cases where the target 106 is a single solar cell, as explained above. Furthermore, a setup in which the length 112 is slightly larger than the dimension 114 is particularly useful when the collector is formed by an array of blocks 100 placed side by side. In this case, a connection region between the two adjacent blocks is located within a space between the adjacent cells (or cells' rows/columns). Such a setup provides that little or no light falls within a space/zone between the adjacent radiation converters. This will be exemplified further below with reference to Fig. 8.

As mentioned above, the inventor has found that when sunlight strikes a solar energy converter cell in a concentrated region near the center of the cell, the conversion efficiency is higher than it would be in cases where sunlight struck the cell in a periphery of the light sensitive surface as well as the case where the sunlight is substantially uniformly distributed in the entire light sensitive surface (diffused fashion). Therefore, the collector block of the present invention is preferably configured for concentrating sunlight (or, more generally, electromagnetic radiation) onto substantially a central region of the single solar cell. To this end, the collector block has appropriately selected parameters such as the shape and curvature of the dome-like outer surface 102, the magnitude of the angle 108 of the inner refractive interfaces, the thickness 109 of the block 100, as well as the optical properties of the medium 101. All these parameters affect a choice for a suitable distance 110 between the solar energy converter (target 106) and the collector 100. The inventor has constructed an experimental setup of the collector block designed for directing sunlight to a standard 5 inch x 5 inch solar cell. This experimental setup has the following characteristics: the projection of the collector block upon the solar cell plane is a 5.5 inch x 5.5 inch square (dimension 114 in Fig. 1); the dome-like shape is a part of a sphere having a radius of curvature of 8 inch; the thickness 109 of the block measured as a distance between the apex and the highest point on the dome is about 0.4 inch; the angle is about 150 degrees; a suitable distance between the collector block and the solar cell (distance 110 in Fig. 1) is about 4 inch; the region of the cell upon which the solar radiation is concentrated has a dimension of about 2-3 inches, and is substantially a square.

In some embodiments of the present invention, the collector block 100 is designed having at least two pairs of refractive interfaces, each pair defining a V-shaped cross section of a different angle (108). The different angles may be selected by taking into account the possible movement/direction of the solar energy converter (and therefore of the collector 100 associated therewith) relative to the sun. In this regard, angle 108 can vary widely. A preferable, but non-limiting, range is between 120 and 160 degrees.

Figs. 1-3 illustrate the collector block 100 placed at a distance 110 from a solar energy converting cell (target 106), and oriented such that the facet 104a is located at the west side and the facet 104b is located at the east side of the inner surface 104. In Fig. 1, early morning sunlight is shown coming from the east and forming a small angle 114 with the horizontal. A small part of the sunlight (for example ray 116e) strikes the solar energy converter (target 106) without passing through the collector block 100, however such light strikes the solar energy converter at the angle 118, which may or may not be an angle at which the solar energy converter is able to effectively convert the ray 116e into energy. The dome-shaped surface 102 of the collector block 100 is struck by light rays 116a-116d and refracts them into the collector block, where these rays are further refracted by interface 104b towards the target. These rays would otherwise (with no interaction with the collector block) propagate in their original direction and would not reach the solar energy converter (target 106), as shown by the dotted line 120. Light rays 116a-116c are thus refracted by the dome-shaped surface 102, traverse the medium 101, and converge, thereby illuminating a region located near the center of the solar energy converter (target 106). If the solar energy converter is a single solar cell, then this configuration is advantageous, since this energy conversion is more efficient when the solar light is concentrated in a region near the center of the solar cell. Light ray 116d strikes the outer surface 102 at a refractive angle higher than the critical angle and is therefore reflected away.

Fig. 2 illustrates a light propagation scheme for mid-morning sunlight (light rays

122a-d and 124a-b) coming from the east and forming an angle 126 with the horizontal. Light rays 122a-d striking the east side of the collector block 100 are concentrated onto a region near the center of the target 106. Without the collector block 100, the light rays 122a-d would strike the target 106 uniformly, as shown by the dotted line 128. Light rays 124a-b striking the west side of the collector block 100 might not effectively illuminate the target. Some of the light rays, such as the light ray 124b, are deflected onto the target 106 and will therefore be at least partially converted to energy. Others, such as the light ray 124a will not reach the target 106, notwithstanding the deflection caused by the collector 100.

In Fig. 3, midday sunlight (generally, light waves 130) is shown propagating downward and forming a substantially 90-degree angle with the horizontal. All the light waves 130 are deflected by the collector block 100 and concentrated onto one or more regions near the center of the target 106.

Figs. 1-3 show that at different times of the day, the presence of collector 100 has two important effects: (i) at least some light rays that would not otherwise reach the target are deflected onto the target for energy conversion; and (ii) light striking the collector is concentrated onto one or more regions near the center of the target 106. Both effects (i) and (ii) increase the energy output of the target 106, especially (but not only) if the target 106 is a single solar energy conversion cell.

The effects (i) and (ii) are summarized in Fig. 4, in which an early-morning light ray (200), a mid-morning light ray (202), a midday light ray (204), and a late-afternoon light ray (206) are deflected by the passive collector 100 (stationary mounted with respect to its associated converter) toward a region near the center of the target 106.

Reference is made to Figs. 5a-5d illustrating bottom views of a basic block of the collector in different embodiments of the present invention.

In Figs. 5a-5c, the collector block 100 has an outer dome-like surface that is a portion of a sphere, and the inner surface 104 includes a plurality of substantially planar interfaces (generally, 302) forming inverted V-shaped or wedge-shaped structures. In Fig. 5a, a single pair formed by the interfaces meets to create the wedge 304. In Fig. 5b, two wedges 304 and 306 are formed by intersection of two pairs of interfaces, thereby forming a surface of a square pyramid. In Fig. 5c, three intersecting wedges 304, 306, and 308 are formed by four pairs of interfaces, thereby giving rise to a surface of an octagonal pyramid. According to yet other embodiments, exemplified in Fig. 5d, the inner surface 104 is a single continuous interface having essentially a conical shape.

Referring to Fig. 6, a perspective view of a collector block according to the example of the invention is shown configured for use with a multi-cell solar energy converter (e.g. the cells are arranged in a two-dimensional array). Here, a dome-like shaped surface 102 is configured as a portion of a sphere. The collector block 100 shown in Fig. 6 is generally similar to that of Fig. 5b. Such a collector may be used for directing electromagnetic radiation to a radiation converting target 106 having a plurality of cells (106a, 106b, for example). The target 106 may be a mobile or fixed target.

Fig. 7 shows another example of the collector block 100 configured for use with a target formed by an array of radiation converter cells. In this example, the collector block 100 has a general elongated structure. This structure is suitable, for example, for larger-scale solar collectors, such as solar hot water collectors, or for elongated (optionally one-dimensional) arrays of radiation converters cells. Such an elongated collector block 100 may be designed for being placed above a one-dimensional array. The outer dome-like shaped surface 102 of the collector block 100 is part of a cylinder having a length 400, which is appropriately selected to correspond to the length of the associated cells' array (e.g. is substantially equal thereto).

Reference is made to Fig. 8 illustrating a cross sectional view of a portion of a collector of the present invention formed by an array of the above-described basic blocks joined together side by side, in order to improve the performance of a multi-cell electromagnetic radiation converter, such that each collector is associated with a single solar cell or a single column of cells.

In Fig. 8, a multi-cell electromagnetic radiation converter 500 includes a first cell (or first cell column) 501 and a second cell (or second cell column) 502 spaced apart from each other, and therefore forming a dead zone/space between them (i.e. radiation incident on the dead zone is not converted into energy). The first cell 501 is associated with a first collector block 504, and second cell 502 is associated with a second collector block 506. The collector blocks 504 and 506 may assume any embodiment of the collector 100 of Figs. 1-7. The collector blocks 504 and 506 are connected to each other and the entire structure (collector) is elevated at a suitable height with respect to the radiation converter 500 by support plates 508 and 510, respectively.

In a preferred embodiment, a length 512 of a projection of the collector block onto the target plane is slightly larger than the corresponding dimension 514 of the radiation converting surface of the cell 501. The same dimensional relationship exists between the cell 502 and the collector 506. This is particularly useful to, on the one hand, concentrated radiation collected by the block onto a region at or near the center of the respective cell, and on the other hand to align a region of connection between the adjacent blocks of the collector with the dead zone between the respective radiation converting cells 501 and 502.

Reference is now made to the following examples, which together with the above descriptions illustrate some embodiments of the invention in a non limiting fashion.

Figs. 9A and 9B exemplify an experimental basic block of the collector of the present invention. In this example, the collector block has one pair of V-shaped refractive interfaces and hemispherical outer surface. Generally, the collector block may be designed to be used with a single cell or an array of cells; a projection of the collector block onto the cell plane is substantially equal to or larger than the dimension of the light sensitive surface of the cell or cells associated with the collector block.

Fig. 9C is a schematic drawing illustrating an experimental setup designed for testing the effect of a collector of the present invention on the electric current output of a solar energy converter cell. In the experiment, two solar cells (702 and 704) were tested. The solar cells were Mono-Crystalline Silicon cells commercially available from "Sun-tech Power Co." and were cut to have 40x40mm dimensions. The first solar cell 702 was associated with a collector 706. The collector 706 was similar to that of Figs. 9A-9B with a hemispherical outer surface having a diameter of 120 mm, having a square perimeter, and sporting two substantially planar interfaces intersecting at an angle of 150 degrees. The thickness of the collector (measured as described above) was about 10 mm. The distance between the collector and the solar cell panel was about 30- 35 mm. A first amperemeter 708 measured the current output of the first solar cell 702, and a second amperemeter 710 measured the current output of the second solar cell 704. A first thermometer 712 measured the temperature of the first solar cell 702, and a second thermometer 714 measured the temperature of the second solar cell 704. The temperature measurements are used to additionally show the effect of amount of light incident onto the solar cell via the collector of the invention.

On the first day of testing, the time averaged current output of the first solar cell 702 was 0.57A, compared to the 0.34A of the second solar cell 704, showing an improvement of 67%. The average temperature of the first solar cell 702 was 46.4°C, compared to the 39.0°C of the second solar cell 704 indicating a temperature rise of 19% resulting from the interaction with incident light.

On the second day of testing, the time averaged current output of the first solar cell 702 was 0.56A, compared to the 0.35A of the second solar cell 704 - an improvement of 61%. The average temperature of the first solar cell 702 was 44.4°C, compared to the 39.4°C of the second solar cell 704 - a rise of 19%.

On the third day of testing, the collector 706 was removed, in order to compare the performance of the solar cells 702 and 704 without the collector. The time averaged current output of the first solar cell 702 was 0.39 A, and of the second solar cell 704 was 0.38A— , i.e. approximately equal. The average temperature of the first solar cell 702 and second solar cell 704 was 40.0°C.

It was proven that in the absence of the collector 706, the performance of both solar cells 702 and 704 is substantially equal. When the first solar cell 702 was equipped with the collector 706, the current output of the first solar cell 702 improved by more than 60%. Furthermore, the temperature of the first solar cell 702 rose by 19%, proving that the first solar cell 702 was illuminated by more sunlight than the second solar cell 704, because of the association between presence of the first solar cell 702 and the collector 706.

Fig. 10 is a graph generated by measurements effected via the setup of Fig. 9C. The graph illustrates a comparison between the time profiles of the electrical current produced by a solar cell equipped with a collector of the present invention and electrical current produced by a solar cell with no such collector. The graph shows the electric current output in Amperes generated by the first and second cells 702 and 704 during the first day of testing. The curve 800 corresponds to the current output of the first solar cell 702 associated with the collector 706. The curve 802 corresponds to the current output of the first solar cell 704. It is clear that the power output of the first solar cell 702 was far greater. It should be understood that curve 800 has less smoothness than curve 802 solely because the collector was manufactured for experimental purpose only, and its transparency (due to physical defects) was less than desired for practical use, but such desirable transparency can be easily achieved with existing materials and manufacturing techniques.

Fig. 11 is a graph generated by measurements effected via the setup of Fig. 9C. The graph illustrates the performance increase and the temperature increase of a solar cell caused by the association of the solar cell with the collector of the present invention.

During the first day of testing, the difference between the current output of the first solar cell 702 and the current output of the second solar cell 704 was between 45% and 110% of the current output of the second solar cell 704, as shown by curve 900. The difference between the temperature of the first solar cell 702 and the temperature of the second solar cell 704 was between 10% and 30% of the temperature of the second solar cell 704, as shown by curve 902.

During the second day of testing, the difference between the current output of the first solar cell 702 and the current output of the second solar cell 704 was between 40% and 90% of the current output of the second solar cell 704, as shown by curve 904. The difference between the temperature of the first solar cell 702 and the temperature of the second solar cell 704 was between 6% and 26% of the temperature of the second solar cell 704, as shown by curve 906.

Thus, the present invention provides a simple and effective solution for improving the performance of a radiation converter. The radiation collector of the present invention can be used with various types of radiation converters, and can advantageously be used with radiation converters intended for converting radiation from a moving radiation source, such as the sun. The invention provides a passive solution in that the collector can be stationary, mounted with respect to the associated radiation converter. The use of the appropriate design of the collector of the present invention eliminates the need for moving the radiation collector and/or converter for tracking the motion of the radiation source, and on the other hand allows for using the collector with a movable radiation converter.

Claims

CLAIMS:

1. A passive electromagnetic radiation collector for use with a radiation converter, the collector comprising at least one basic block, wherein:

said basic block of the collector is substantially transparent to said electromagnetic radiation and has spaced-apart first and second surfaces, by which said basic block when in operation is exposed to a source of the electromagnetic radiation and faces the radiation converter respectively;

said first surface of the basic block has a dome-shaped configuration of a predetenriined curvature;

said second surface of the basic block is formed by refractive interfaces defining an apex structure aligned with an uppermost region of said dome, and sloping downward toward edges of the block, such that the refractive interface directs at least a part of radiation collected by said first surface onto a region outside said basic block on a plane spaced apart from said second surface, thereby enabling interaction of said at least part of said collected radiation with a corresponding region of a radiation sensitive surface of the radiation converter located in said plane.

2. The radiation collector of Claim 1, wherein said apex structure of the basic block defines a predetermined angle selected in accordance with a trajectory of movement of said source of electromagnetic radiation.

3. The radiation collector of Claim 1 or 2, wherein said apex structure of the basic block defines an angle in a range between 120 degrees and 160 degrees.

4. The radiation collector of any one of Claims 1 to 3, wherein a dimension of a projection of said dome-like surface onto said plane is substantially equal to or larger than a corresponding dimension of a radiation converting surface of said radiation converter.

5. The radiation collector of any one of the preceding Claims, wherein said domelike surface has a cross section being a segment of a circle of a predetermined radius.

6. The radiation collector of Claim 5, wherein said dome-like surface is a part of a sphere.

7. The radiation collector of Claim 6, wherein said second surface comprises one or more pairs of the refractive interfaces, the refractive interfaces being substantially planar and the interfaces of each pair defining said angular configuration.

8. The radiation collector of Claim 6, wherein said second surface is a conical surface.

9. The radiation collector of Claim 5, wherein said dome-like surface is a part of a cylinder.

10. The radiation collector of Claim 9, wherein said second surface comprises a single pair of the refractive interfaces which are substantially planar and define said apex structure.

11. The radiation collector of any one of Claims 1 to 10, configured for collecting solar radiation and directing it to a solar energy converter having a substantially planar radiation converting surface.

12. The radiation collector of any one of Claims 1 to 11, wherein a dimension of the radiation converting surface is 5 inches, a dimension of a projection of the dome-like surface onto a plane of said radiation converting surface being about 5.5 inches.

13. The radiation collector of Claim 12, wherein said region upon which said collected radiation is directed has a dimension of about 2-3 inches.

14. The radiation collector of Claim 12 or 13, wherein said region upon which said collected radiation is directed is located substantially at a central part of a surface portion on said plane defined by the projection of said dome-like surface.

15. The radiation collector of any one of Claims 12 to 14, capable of directing said at least part of said collected radiation onto said region, when the radiation collector is located at a distance of about 4-5 inches from said region.

16. The radiation collector of any one of Claims 12 to 15, wherein said curvature of the dome-like surface has a radius of about 8-10 inches.

17. The radiation collector of any one of Claims 1 to 16, comprising an array of the basic blocks.

18. The radiation collector of Claim 17, wherein each of the basic blocks is configured for directing the collected radiation onto a single or multiple radiation converters.

19. A system comprising: an electromagnetic radiation converter having a substantially planar radiation sensitive surface; and an electromagnetic radiation collector stationary mounted above said radiation sensitive surface, the radiation collector being substantially transparent to said electromagnetic radiation and comprising at least one basic block which has spaced-apart first and second surfaces exposed respectively to an electromagnetic radiation source and at least a portion of said radiation sensitive surface of the radiation converter, said first surface having a dome- shaped configuration of a predetermined curvature, said second surface being formed by refractive interfaces defining an apex structure aligned with an uppermost region of said 5 dome and sloping downward toward edges of the collector, such that the refractive interface directs at least a part of radiation collected by said first surface onto a region of said radiation sensitive surface.

20. The system of Claim 19, wherein said basic block of the radiation collector has a top portion, defined by said uppermost region of the dome-like outer surface and a top

10 of the apex structure aligned therewith, said top portion being aligned with substantially a central part the radiation sensitive surface covered by said at least one basic block.

21. The system of Claim 19 or 20, wherein said basic block of the radiation collector is configured such that a projection thereof on a plane of said light sensitive surface is equal or larger than the light sensitive surface covered by said block.

15 22. The system of any one of Claims 19 to 21, wherein said radiation collector is spaced from said radiation sensitive surface a predetermined distance.

23. The system of any one of Claims 19 to 22, wherein the basic block is configured such that said apex structure is formed by at least one pair of substantially planar interfaces forming a certain angle between them being an angle of said apex structure.

20 24. A solar energy convention system comprising:

a panel carrying an array of solar energy converting cells arranged in a spaced- apart relationship along at least one axis, and

a passive electromagnetic radiation collector stationary mounted with respect to said panel, the radiation collector comprising an array of connected to one another basic

25 blocks, wherein said basic block is substantially transparent to said electromagnetic radiation and has spaced-apart first and second surfaces, by which said basic block when in operation is exposed to a source of the electromagnetic radiation and to said panel respectively, said first surface of the basic block having a dome-shaped configuration of a predetermined curvature, said second surface of the basic block being

30 formed by one or more refractive interfaces defining an apex structure aligned with an uppermost region of said dome, and sloping downward toward edges of the block, such that the refractive interface directs at least a part of radiation collected by said first surface onto a region onto a plane spaced apart from said second surface, thereby enabling interaction of said at least part of said collected radiation with a corresponding region of the radiation converter located on said plane.

25. The system of Claim 24, wherein said apex structure of the basic block defines an angle in a range between 120 degrees and 160 degrees.