EP1984681A1

EP1984681A1 - Electromagnetic radiation collection device

Info

Publication number: EP1984681A1
Application number: EP06744827A
Authority: EP
Inventors: Alastair Mcindoe Hodges; Garry Chambers
Original assignee: Universal Biosensors Pty Ltd
Current assignee: Sunday Solar Technologies Pty Ltd
Priority date: 2006-02-07
Filing date: 2006-06-02
Publication date: 2008-10-29
Also published as: AU2006337888A1; EP1984681A4; TW200730902A; WO2007091119A1; BRPI0621309A2; AU2006337888B2; IL193228A0; CA2642645A1; US20090165782A1; KR20090021256A; JP2009526391A

Abstract

An electromagnetic radiation collector includes a channeling area having an entry end for receiving the electromagnetic radiation, an exit end, and at least one reflective wall between the entry end and the exit end; and a radiation collection element near the exit end of the channeling area, the radiation collection element being adapted to collect the electromagnetic radiation.

Description

ELECTROMAGNETIC RADIATION COLLECTION DEVICE

BACKGROUND OF THE INVENTION

Field of the Invention

[0001] The present invention relates generally to electromagnetic radiation collection.

Related Ait

[0002] The collection and concentration of electromagnetic (EM)

radiation is well known. Radio waves are typically collected and concentrated using parabolic dishes. Solar radiation is collected and concentrated using parabolic mirrors or lenses. The former devices suffer from requiring a relatively

high height-to-collection area ratio and the latter being expensive, heavy and

fragile. Both these types of device also suffer from the requirement to track the

source in order to function properly.

BRIEF SUMMARY OF THE INVENTION

[0003] The invention seeks to overcome at least some of the

deficiencies in the prior art by providing an EM radiation collection device which can cover a large area, have a low profile, have no requirement to track the source

and be constructed so as to be relatively light and inexpensive.

[0004] There is a pressing need to be able to generate energy from

renewable energy sources. Solar enei'gy is one such resource which has potential

to be exploited. Conventional devices for collecting radiant energy to generate

energy in a useful form suffer from a high capital cost and/or the inability to

generate high enough temperatures to be useful for many applications. The invention seeks to overcome these deficiencies in the prior art by providing a

radiant energy concentration device that can gather energy from a relatively large area and concentrate it onto a small target area. The device is relatively

inexpensive to produce, can be light in construction and has the potential to

generate high target temperatures or, in the case of conversion to electricity by

photovoltaic cells, require only a small area of cells, thus saving cost.

[0005] The invention is directed to a device that can cover relatively large collections areas at relatively low cost, does not necessarily require materials of particular refractive index and can be made of light construction.

[0006] The invention is capable of being less massive and having a

lower profile than prior art concentration devices. It is also capable of having high

concentration factors. It is suitable in any application where it is desired to collect

and concentrate EM radiation, with particular utility in the collection and

concentration of solar radiation. In the case of solar radiation, a device in

accordance with the invention can be used in conjunction with photovoltaic cells

or to heat a fluid to harness the solar energy for a desired purpose. In the case of

radio frequency radiation, the subject device could be used to collect, focus and

tune the radiation.

[0007] An example of a device in accordance with the invention is an

electromagnetic radiation collector that includes a channeling area having an entry

end for receiving the electromagnetic radiation, an exit end, and at least one

reflective wall between the entry end and the exit end; and a radiation collection

element near the exit end of the channeling area, the radiation collection element

being adapted to collect the electromagnetic radiation. [0008] Another example of a device in accordance with the invention

is a control mechanism for a radiation collector where the radiation collector is adjustable to track a moving radiation source and where the control mechanism

comprises a first sensor to monitor the ambient radiation conditions and a second

sensor to monitor the output of the radiation collector.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The foregoing and other features and advantages of the

invention will be apparent from the following, more particular description of preferred embodiments of the invention, as illustrated in the accompanying

drawings wherein like reference numbers generally indicate identical, functionally

similar, and/or structurally similar elements.

[00010] Figure 1 shows an example of a channeling area;

[00011] Figure 2 shows an example of a device having multiple

channeling areas;

[00012] Figure 3 shows a cross-sectional view of an array of channeling

areas;

[00013] Figure 4 shows a cross-sectional view of a different array of

channeling areas;

[00014] Figure 5 shows a first embodiment of the invention;

[00015] Figure 6 is a cut-away view of the embodiment shown in Figure

5;

[00016] Figure 7 shows a second embodiment of the invention; [00017] Figure 8 shows a side view of the embodiment shown in Figure

7;

[00018] Figure 9 shows an alternate embodiment related to the

embodiment shown in Figures 7 and 8;

[00019] Figure 10 shows a third embodiment of the invention;

[00020] Figure 11 shows an alternate embodiment related to the

embodiment shown in Figure 10; and

[00021] Figure 12 shows a fourth embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[00022] An exemplary embodiment of the invention is shown in the

drawings and described herein.

[00023] An example of a device in accordance with the invention has an

assembly of channeling areas wherein the EM radiation can be internally reflected within the channeling areas. In one embodiment, the channeling areas are

constructed such that at least some of the EM radiation that enters abroad end of the channeling areas will be steered within the channeling areas to exit a narrow

end of the channeling areas. The broad ends of the channeling areas are

assembled to form a surface that is herein termed the collection surface. EM

radiation falls on the collection surface and enters the broad ends of the channeling

areas. The EM radiation is reflected from the walls of the channeling areas so as

to be directed to exit from the narrow end of the channeling areas. This is

achieved by ensuring that at each reflection point the angle of incidence of the EM radiation to the reflecting surface is less than 90°. A method for ensuring that this is the case for a wide arc of angles of the EM radiation incident on the collection

surface is to shape the channeling areas such that they are much longer than they

are broad at their broad end. This provides, in some embodiments, a small angle

of taper of the walls of the channeling area thus fulfilling the reflection angle

requirements for a broader range of incident EM radiation angles. The ratio of

length of the channeling area to the breadth of its broad end should desirably be

between 2 and 1000, more preferably between 5 and 100, and most preferably between 10 and 50. Figure 1 shows an example of a single channeling area and a

typical path 20 that EM radiation might take within the area.

[00024] The channeling areas can be made of solid material that is

capable of transmitting the EM radiation that is to be collected and concentrated

and with walls that reflect the EM radiation back into the channeling area. In

another embodiment of the invention, the channeling areas are formed as cavities,

where the walls of the cavities are capable of reflecting the EM radiation back into

the cavity.

[00025] hi one embodiment of the invention, the narrow ends of an

assembly of channeling areas are gathered together into an area that is smaller than

the area of the broad ends of assembled channeling areas. In such an example, the

EM radiation collected over the broad ends area is concentrated into the narrow

ends area. An example of this embodiment is shown in Figure 2.

[00026] hi some embodiments of the invention, the channeling areas are

tapered in only one dimension, that is they take the form of tapered slots, hi other

embodiments, the channeling areas are tapered in two dimensions so that they take the form of tapered rods, where the rods can be of any cross-sectional shape that is suitable for packing together at high density. Examples of such shapes are circles,

squares, rectangles, triangles and other multi-sided polygons.

[00027] When the channeling areas take the form of tapered rods, to aid

in accommodating the curvature or the rods, maintain a high packing density for

the broad ends of the channeling areas and enhance the strength of an assembly of

the channeling areas, the channeling areas can be assembled such that each

channeling area is staggered relative to its neighbors. In a particular embodiment of this aspect of the invention, rows of channeling areas are assembled such that

the channeling areas in each row are offset from the row in front such that the

narrow end of each channeling area is between the narrow ends of the neighboring

channeling areas in the rows immediately in front of and behind the subject row.

By assembling the channeling areas in this way it is possible for the narrow end of

each channeling area to curve into the space between the neighboring channeling

areas in the row in front of it. This allows the channeling areas to be curved while

maintaining high packing density of the broad ends of the channeling areas.

[00028] It is desirable to maintain a high packing density of the broad

ends of the channeling areas at the collecting surface so that the highest fraction of

the EM radiation incident on the collecting surface enters a channeling area and is

not reflected back.

[00029] hi one embodiment of the invention, the channeling areas are

circular in cross-section and the broad ends are assembled in a packing

arrangement as is shown in Figure 3, where a top view of the assembled rows of

the broad ends of the circular channeling areas are shown offset from one another. Triangles are superimposed on the view to show the relationship of the centers of the circular ends. This arrangement increases packing density and allows space

for the channeling areas to be curved as disclosed above. With this arrangement, a

maximum fraction of π/2^3 (approx. 90%) of the incident radiation is collected.

In a particular embodiment of this aspect of the invention, channeling areas with a

square or rectangular cross-section are used. A top view of this arrangement is

shown in Figure 4. With this shape of channeling area, the broad ends of the

channeling areas can be packed such that close to 100% of the incident radiation enters the channeling areas and is thus collected. Note that in the embodiment

shown in Figure 4 it is possible, but not necessary, for the channeling areas to be of rectangular cross-section down their full length. For example, the channeling

areas may be square or rectangular at the collecting surface but then transition to a

circular area as we move down the channeling area toward its tip.

[00030] Devices in accordance with the invention are useful in

applications where EM radiation concentration devices have been used in the prior

art, in particular solar radiation and radio frequency radiation. Examples of such

uses particularly relevant to the collection and concentration of solar radiation are to heat fluid circulating through a tube or pipe, to generate electricity directly

using photovoltaic cells or to produce hydrogen from water. Note that the

invention has particular utility in the application of producing electricity using

photovoltaic cells as it allows the light to be collected from an extended area using

the relatively inexpensive device of the invention and concentrate it on to a

relatively small area of the relatively expensive photovoltaic cells. This

potentially allows electricity to be generated at lower capital cost. Also, this device addresses deficiencies in the conventional art when attempting to use a concentrator with photovoltaic cells. Apart from expense and weight, the

conventional devices suffer from relatively low concentration factors of typically

less than 10 and the problem of the photovoltaic cells overheating and becoming

less efficient.

[00031] A low profile collector and concentrator is desirable in

applications for radio frequency (RP) radiation. In these applications, the device

could be used to focus the Rp radiation onto an RF receiver. Also, by careful choice of the dimensions of the channeling areas, the subject device could be used

to tune the collected RP radiation to a frequency that can be received more easily

by a receiver. For example, the device can be used to tune the RF radiation to a

higher frequency, which requires a smaller and more easily implemented receiver.

[00032] The subject devices can be made by any suitable method. The

channeling areas can be solid elements transmissive of light and made from

materials such as polymers or glass. For these solid elements, the walls of the

elements can be coated with a reflective material or the refractive index of the

material can be such that in most cases the incident angle of the EM to be reflected

to the wall of the element exceeds the critical angle so that total internal reflection

occurs. This embodiment has potential advantages in ease of fabrication but can

also tend to be heavy. This embodiment could be constructed by manufacturing

many elements and assembling them into arrays as disclosed above.

[00033] A particular embodiment is one where the channeling areas are

cavities formed in a monolithic block made of metal or polymer material. This

may be somewhat harder to fabricate but will be lighter. A method of manufacturing this embodiment is to form an assembly of curved elements, for example tapered elements, from a malleable material such as copper or nickel.

The assembly can be one of individual elements or of rows of elements formed

into combs where each tapered element is a "tooth" of the comb. Each comb

forms a row or portion of a row of the elements and the "teeth" of the combs of

successive rows in the assembly are staggered to give the arrangements shown in

Figures 3 or 4. Before being assembled into an array, the elements can be straight or already curved. If the elements are straight, a bar can be passed over the

assembly of the narrow ends of the elements as a convenient method of introducing the desired curvature. The assembled elements can be held in their

assembly by being clamped into a frame or other similar device. The curved

assembled elements, in conjunction with side walls and, if applicable, a top and/or

base, can then be used as a mold for the final monolithic shape. The shape with

the desired assembly of cavities can be molded by any applicable method. It may

be cast by pouring polymer into the mold and letting it set of by injection molding

techniques. In this process it is desirable to first coat the mold with a suitable

release agent to facilitate removal of the mold elements from the cast shape. After

the cast shape is set the mold elements can be removed. This can most easily be

achieved by first removing the cast shape from the mold side walls, top and/or

base then unclamping the assembly of elements and removing them separately or

in groups as is most convenient and practical. Note that in most cases the

elements will need to be straightened somewhat to be withdrawn from the cavities

so it is desirable that the material from which the tapered elements are made be

malleable so that in can undergo the straightening process without breaking or distorting the shape of the cavity from which it is being withdrawn. This process

results in a cast shape that contains an assembly of densely packed curved, light guiding cavities, wherein the broad ends of the cavities all open onto one face of

the shape and the narrow ends of the cavities all open on to a different face of the

shape.

[00034] If the shape is not cast from an intrinsically reflective material

such as metal or metal filled polymer, then the external faces of the shape and/or

the walls of the cavities can to be coated with a reflective layer. For polymer

material this is most easily achieved with an electroless metal deposition process such as electroless chrome or nickel deposition. A further transparent coating

could be applied over the reflective coating if desired to protect the reflective

coating.

[00035] An alternative embodiment for creating an assembly of

channeling areas for collecting the EM radiation is to use a series of mirrors that

focus the light into a series of spots or strips. In the case of a strip, the optimal

mirror shape is parabolic in the plane of the strip and normal to it. In the case of

spots, the mirror is optimally a parabolic dish. According to this embodiment, the

channeling areas are formed by the space between the adjacent mirrors where,

rather than the adjacent mirrors forming a tapering space, the tapering space is

defined by the tapering shape of the radiation beam reflected from the rear wall of

the channel. Also, the exit to the channel according to this embodiment is the strip

or spot which is the focal point of the rear mirror. Therefore, in this embodiment

it is not necessary for the walls of the channel to taper in order for the radiation

beam to be tapered. This has advantages in flexibility of design and in minimizing the number of reflections that the radiation undergoes before exiting the channel. The strips or spots that form the exit to the channel are arranged to be at the focal

line or point of the mirror such that EM radiation reflected off the mirror is

substantially concentrated onto them. To allow for different angles of EM

radiation incident on the mirrors, the mirrors can be rotated about their focal line

or point such that the focus of the light remains co-incident with the strips or

spots. A control mechanism can perform the rotation whereby a signal, which

could be the output from an EM radiation target or from a separate sensor, is monitored and the rotation of the mirrors performed so as to maximize the amount

of EM radiation impacting the target. A particularly preferred embodiment of

sensor configuration is where the output of a separate sensor can be used in

combination with the output of the radiation target, or a sensor that correlates to

the output of the radiation target, to achieve the control. According to this

embodiment a separate sensor is configured to respond to the ambient conditions

with the target sensor output responding to the focusing configuration of the

mirrors. In the example of when PV cells form the target to generate electricity from solar radiation, a separate light sensitive sensor would be mounted away

from the mirrors such that it monitored the ambient incident radiation on to the panel. This sensor would for example detect a change in the radiation level due to

a cloud or other object passing between the sun and the panel. The target sensor

on the other hand would monitor the output of the light impinging on to the target

PV cells. So, the control mechanism would monitor both the ambient and the

target sensor and if the output of the two sensors varied in a similar way over time,

then the control system would take no action as it would assume that the change in output of the target was due to a change in the ambient conditions. If, on the other hand, the target sensor output changed in a different way to the ambient sensor

output then the control system would move appropriately to maximize the output

of the target sensor.

[00036] The mirrors may have a rear reflecting surface that reflects EM

radiation onto one of the focusing mirrors.

[00037] An assembly of parabolic louvers that can be made to rotate

about their focal line have been described above. The focal line of each louver

impinges upon a receiving area in which one or more receiving elements are placed. The receiving elements can be in the form of openings into a

concentration chamber, as disclosed in co-pending application

PCT/TB2005/003838, herein incorporated in its entirety by reference.

Alternatively, the receiving elements may be adapted to directly convert the

incident radiation. The receiving elements may be adapted to convert the radiation

into electrical energy, for example photovoltaic cells could be placed in the

receiving areas. Alternatively the receiving elements maybe adapted to collect the

thermal energy, thus transferring heat to a fluid medium whereby the energy can be utilized elsewhere, hi the embodiment where PV cells are used as the receiving

elements it is desirable to be able to cool the PV cells for their efficient operation.

According to the current invention, cooling can be provided by having heat

dissipation areas between the areas of PV cells. Since these in-between areas are

shaded from the incident EM radiation by the parabolic louvers they can readily be

adapted to radiate heat efficiently, for example by coating them with a radiating

coating such as a black coating. In an alternative embodiment, a fluid layer can be placed in a space below the plate containing the PV cells and in thermal contact with the back of the PV cells. The fluid can be permanently contained within the space and allowed to circulate within the space, such that the fluid aids in the

transfer of heat from the PV cells to the heat dissipation areas. In a further

embodiment the fluid can be allowed to, or made to, flow though the space

beneath the PV cells wherein the heat is dissipated external to the plate containing

the PV cells. Preferably, the PV cells could be connected in series to a sufficient extent to obtain the output voltage that is desired.

[00038] An advantage of particular embodiments of the present

invention is that there is space between the lines of PV cells. This allows room for

the rows of cells to be connected in the desired fashion. For example each row of

cells, or a portion of each row of cells under a particular focal line can form a

series element. An electrically conductive connection band can be placed in the

spaces between each row of PV cells wherein the connection band extended beneath one row of PV cells to effect electrical connection to the underside of that

row of cells and a series of thin connection bands extended across the upper surface of the second row of PV cells and out to make connection with the

connection band between the two rows of PV cells. Alternative methods for

forming an electrical connection to the upper surface of the PV cells are discussed

later in this disclosure. Preferably at least the lower connection bands would be

made of material of high electrical and thermal conductivity, for example copper

or aluminum. The bands can be a single band made of one material or can be a

composite band made of one or more materials. For example, the portion of the

band that extends under the row of PV cells can be made of aluminum and the portion of the band between the rows of PV cells can be made of copper or another suitable material. Preferably the bands of material can be deposited. The width of the band that is allowed by the space between the rows of PV cells allows

a relatively thin film of connection band to have a relatively large surface area and

cross-sectional area. The latter allows for low electrical resistive losses and the

former allows for efficient heat dissipation of the heat generated by the EM

radiation impinging upon the PV cells. The bands that extend across the top of the cells can be of any suitable material and in general would be of thin width so as to

cover a minimum area of the PV cells. .

[00039] In the case of the collection of thermal energy, a conduit containing a fluid to be heated could be placed at the focal line of each parabolic

louver. Preferably this conduit is adapted such that it receives energy on one

surface from absorption of the concentrated EM radiation and its other surfaces

are insulated to minimize heat loss. There could be multiple conduits or could be

one or more conduits that extend to pass under two or more parabolic louver focal

lines. The conduits would be made of thermally conductive material such as

copper. Since it is desired to have thermally insulating areas between the

conduits, unlike the prior art, there is no need to have a plate such as a copper

plate extend between the conduits. This reduces the cost and weight of the device.

The thermally insulating areas can be filled with air or with insulating materials

such as, for example, foams.

[00040] The profile of the reflective surface of the louvers is preferably

parabolic in shape. The profile of the parabola can be defined by the equations

below, in these equations the focal point of EM radiation reflected from the parabolic profile is defined to be at the x, y point (0, 0). Also where x₀ and y₀ are defined to be the x and y coordinates respectively of the upper tip of the parabolic

profile when the profile is rotated such that EM radiation normal to the x-

coordinate is focused on the focal point (0, 0). The profile is then defined by the

equation:

[00041] y = *² - ^X°

2x₀ 2 tan α₀

[00042] Where a₀ =

[00043] It is to be understood that due to manufacturing imperfection

and changes over time and temperature, the louver profile will only ever

approximately conform to the profile give by the equations above. The degree of

conformance of the profile to the equation above will determine the width of the

focal line that results in practice in the device. The louvers can be manufactured

by any method that results in a reflective surface with a profile along its length that

reflects an acceptable portion of the incident radiation on to a focal line of the

desired width. An acceptable portion of the radiation is determined by considerations of the overall cost of producing electrical or thermal energy from a

specified area. This includes considerations of cost of manufacture of the device,

its useful life, the efficiency of the energy conversion process and the capabilities

of competitive technologies. The desired width of the focal line is decided upon

by a combination of factors balancing cost, practicality of manufacture, device

longevity and ability to dissipate heat. These factors taken together will determine

the optimum width of the focal line for a particular manufacturing method and cost structure. For example, to reduce the cost of the PV cells, an expensive component of the system, it is desirable to reduce their area, however, past a

certain point the cost of producing a reflector capable of the fineness of focus

required and the ability to dissipate heat from the PV cells for their efficient

operation becomes compromised, thus creating an optimum width.

[00044] The louvers can be constructed of metal plates which are bent

to conform to the desired profile. The plates can be intrinsically reflective or

polished or coated and polished to form a suitably reflective surface. These metal

plates could be mounted in suitable mounts to hold the plate at the right location and to allow them to rotate about their focal lines. Alternatively, the louvers can

be cast from metal, preferably with the mounting means integral, with the

reflective surface being polished or coated and polished after the casting. In yet

another alternative, the louver, preferably with integral mounting means, could be

cast or molded from plastic and subsequently metal plated to yield at least the

front parabolic surface reflective. Optionally, the part could then be post coated

with a clear layer to protect the reflective surface from environmental degradation.

[00045] Figure 5 depicts one embodiment of the current invention.

Figure 5 depicts a partially assembled device 100 to illustrate the various

components. Reference number 110 denotes the front parabolic reflective surface

of an exemplary louver 105. Pins 150 locate the louver in side block 120 (only

one side shown) such that the focal line of the louver is coincident with the target

area 140. Pins 160 locate in tie rods 130 to link the louvers together. Pins 150

and 160 are free to rotate in the location holes in side blocks 120 and tie rods 130,

such that when tie rods 130 are moved upward and forward in unison the louvers are rotated about the centre of the pins 150. Note that the centre of the pins 150

are coincident with the focal line of the corresponding louver such that the louver rotates about its focal line. This insures that for any angle of incident light in the

desired range the louvers can be rotated such that the focal line remains coincident

with the target area 140.

[00046] Figure 6 depicts a further cut-away illustration of the current

invention showing how incident radiation is reflected towards the target area. The

aiτows in Figure 6 show exemplary radiation paths. Note that the louvers are spaced such that radiation that is not captured by one louver is captured by the

louver in front of or behind it, thereby maximizing the collection efficiency.

[00047] Example 1 : Louvers were designed with a parabolic reflector

shape according to equation (1) where x₀ and y₀ were -37 mm and 40 mm

respectively, with a louver pivot point separation of 22 mm. End mounting clamps

were constructed with the computed shape by wire cutting the shapes out of

aluminum. The mount clamps were made in two pieces with the concave parabolic

shape cut into the front of the rear half of the clamp and the corresponding convex

parabolic shape formed as the rear surface of the front portion of the clamp. 0.2 mm thick brass sheet was nickel plated and polished to give a highly reflective

surface and the plate cut into widths corresponding to that needed for a louver.

The plated brass sheet was clamped at either end between the two halves of the

mounting clamps. Steel pins were used to mount the mounting clamps to side

plates, where the pins were located in holes coincident with the focal line of the

louver. Pins in the upper end of the mounting clamps were mounted in holes in a tie rod, as shown in Figure 5. Ten louvers with a length of 200 mm were assembled in this way.

[00048] Example 2: Louvers manufactured by injection molding were

fabricated. The parabolic shape was computed according to equation 1 with x₀ and

y₀ as -35 mm and 60 mm respectively, with a louver separation of 20 mm and the

base of the louver being 7.15 mm above the focal plane of the louvers. The

dimensions were chosen such that the louvers could be rotated to be able to accommodate incident radiation angles from 20 degrees to 115 degrees, measured

from the x-coordinate, without the base of the louvers having to impact the focal plane. End mounts with integral pins were designed to be molded with the louver

shape in one piece. The mold was constructed to give a mirror smooth finish on

the front parabolic surface. The louver was injection molded from an

ABS/polycarbonate blend Bayblend® T 45 PG (Bayer Materials cience) and then

metallized to form the reflective coating.

[00049] hi one embodiment of the invention, narrow strips of P V cells

are placed at the focal lines to receive the concentrated radiation to convert it to

electricity. To gather the current generated from the PV cells, it is necessary to

make electronic connection to the upper and lower surface of the PV cells. It is

also often desirable to connect a number of the strips of PV cells in series to

generate a higher voltage and decrease the current that needs to be carried for a

particular power output.

[00050] According to the present invention, the lower connection to a

strip of PV cells is made by a conductive plate on which the PV cell sits. The

plate can be made from any material with sufficiently low electrical resistance. Non-exclusive examples of suitable materials are aluminum, copper, tin and

copper covered with a layer of tin.

[00051] If it is desired that two or more PV cell strips are to be

connected in parallel then the lower connection plate is common to those strips of

cells or individual plates are brought into electrical connection by other means such as by separate wires.

[00052] If it is desired that the strips of PV cells be connected in series then there is a separate lower connection plate for each strip of PV cells. The

connection plate would extend beyond the edge of the strip of PV cells to allow other electrical connections and to act as a heat dissipation device to cool the PV

cells when in operation.

[00053] According to the present invention, the electrical connection to

the upper surface of the PV cell strip is made by an electrically conductive layer placed in contact with the upper surface of the PV cell, hi a preferred

embodiment, the upper surface connector is a continuous strip that runs the length

of the PV cell strip, overlapping and in electrical contact with the upper surface of

the PV cell strip along one lengthwise edge of the connector strip, in the area of

the PV cell strip that is in shadow in operation. For the embodiment where the PV

cells are to be connected in series the other lengthwise edge of the connector strip

overlaps and is in electrical contact with the extension of the lower connection

plate of the next strip of PV cells. The connector strip in this embodiment thus

makes a bridging electrical connection between the top surface of one strip of PV

cells and the lower surface of the next strip of PV cells. [00054] Suitable materials for the upper connector strip are any

materials that can form a layer and have sufficiently low electrical resistance. Non-exclusive examples of such materials are metals, metals coated with

electrically conductive adhesive, metals coated with a non-conductive adhesive

but where the metal is textured such that areas of the metal penetrate through the

non-conductive adhesive, conductive inks, unsupported conductive adhesives and

solder. Non-exclusive examples of suitable metals are aluminum, copper, tin, tin coated copper or silver. Non-exclusive examples of suitable conductive adhesives

are pressure sensitive adhesives filled with silver or carbon such as ARclad@90038 (Adhesives Research Inc, Glenn Rock, USA) and silver doped

epoxy. An example of a suitable conductive tape with a conductive adhesive is

1181 Tape Copper Foil with Conductive Adhesive (3 M Corporation). An

example of a suitable conductive tape coated with a non-conductive adhesive is

1245 Tape Embossed Copper Foil (3M Corporation) where the embossed features

on the foil penetrate through the non-conductive adhesive layer. Examples of

suitable conductive inks are carbon or silver filled inks. Note that the upper

surface connector must only be capable of forming a continuous electron

conduction path from the PV cell to the next lower connector plate with

acceptably low electrical resistance. It need not be a continuous connection path

along the length of the PV cell strip, as long as the overall resistance of the

connection of the upper surface of the PV cell with the lower connection plate of

the next strip of PV cell is desirably low. For example, the connection could be a

series of wires or dots bridging the gap to achieve the electrical connection.

However, a continuous connection layer down the length of the PV cell strip is usually preferred as in general it will lower the electrical resistance of the connection and will aid in heat transfer away from the PV cell to cool it for more

efficient operation.

[00055] An additional advantage of the present invention is that there is

a small distance between any area of the upper surface of the PV cell exposed to

the concentrated sunlight and the current collector. The width of the PV cell strip

exposed to the concentrated sunlight is small, at best equivalent to the width of the

focal line from the parabolic louver mirror. A typical width is less than 5 mm and more preferably less than or equal to 2 mm. So the current collected by the upper

surface connector only has to travel a short distance through the PV cell before

entering the low resistance connector. This reduces resistive losses in the device

without the need to have any of the sunlight blocked from the PV cell by the upper surface connector.

[00056] Optionally, after the array of connections has been constructed

as illustrated above, part or all of the array could be overlaid with a layer of transparent material (as is known in the art) to protect the device from water

ingress, corrosion and mechanical damage. As a further option, the transparent

protective layer need not cover all of the array, but only cover the PV cells. The

upper surface connector and the lower surface connector could be covered with a

layer to protect against corrosion and to aid the radiation of heat, for example a

black paint or other thin polymer layer. Preferably there would be a good seal

between the transparent coating and the heat radiating coating to prevent the

ingress of moisture into the device. [00057] Figures 7 and 8 give a top view and cross-sectional view respectively showing three strips of PV cells connected in series in one

embodiment of the present invention.

[00058] If it is desired to connect the strips of PV cells in parallel then

the upper surface connector layer from one strip of PV cells is connected to the upper surface connector layer of the next strip of PV cells. One embodiment of the

connection method for parallel connection is shown in Figure 9.

[00059] In figures 7, 8 and 9, 210 denotes the lower surface connectors,

220 denotes the PV cell strips and 230 denotes the upper surface connectors. In operation, light is concentrated onto the areas pointed out by 220. In Figure 8, 240

denotes a support base which is electrically non-conductive or at least electrically

insulated from 210 and 230. In Figure 9, 250 denotes side connection bars. These

bars 250 serve to connect the strips of upper surface connector together in parallel

fashion. In this configuration the lower surface connector is a continuous plate,

connecting the lower surfaces of the strips of PV cells in parallel fashion.

[00060] To connect an external circuit to the array of PV cells shown in

Figures 7 and 8, one connection would be made to the lower surface connector

210 at one end of the array and the other connection to 260, the plate connected to

the upper surface of the last strip of PV cell. Optionally, the second connection

could be made directly to the last upper surface connector in the array, in which

case 260 is not necessary. To connect an external circuit to the parallel array

shown in Figure 9, one connection would be made at any suitable location or

locations on 210 and the other connection at any suitable location or locations on

one or both bars 250. The bars 250 are made of a material with low electrical resistivity. They could be made from the same material as the upper surface

connectors 230 or they could be made for example from copper wire or tinned copper wire that is soldered to each upper surface connector strip 230.

[00061] According to another embodiment, a solid electrically

conductive wire or ribbon is laid abutting one edge of the strip of PV cell(s). The

wire or ribbon is of suitable cross-section such that it overlaps at least a portion of

the adjacent conductive pad to which it is desired to connect the top surface of the

PV cell(s). A bead of solder or conductive ink can then be applied to form an electrically conductive bridge between the top surface of the PV cell(s) and the

conductive wire or ribbon. Optionally, an additional bead of solder or conductive ink can be applied to form a conductive bridge between the conductive wire or

ribbon and the conductive pad. In the absence of this second bead, the fact that

the conductive wire or ribbon overlaps and rests against the conductive pad can be

used to provide sufficient electrical connection. A cross-sectional schematic

illustrating this aspect of the invention using a wire of substantially circular cross-

section is given in Figure 10 and the situation when using a ribbon of substantially trapezoidal cross-section is given in Figure 11.

[00062] hi Figures 10 and 11 , the lower surface of the PV cell 320 is

placed in contact with a conductive pad 310, which is formed on an electrically

insulating substrate 340. A wire 330 (of circular cross-section in Figure 1 and of

trapezoidal cross-section in Figure 2) is placed so as to abut one side of 320 and to

also overlap a portion of a second conductive pad 315. A bead of conductive

bridging material 350 increases the area of electrical connection between wire 330

and the top surface of the PV cell 320. A second, optional bead of conductive material 360 can be formed between 330 and 315 to increase the robustness of the

connection if necessary.

[00063] It is to be understood that this aspect is not restricted to any

particular cross-section of wire or ribbon but that any cross-section that allows

bridging between the top surface of the PV cell(s) and the adjacent conductive pad

is within the scope of this invention. Examples of other suitable cross-sectional

shapes are, oval, triangular, square, rectangular, rhomboid, among others.

[00064] Suitable materials from which the wire or ribbon can be

constructed are any materials with suitably low electrical resistance through the cross-section of the wire or ribbon. Examples of suitable materials are copper,

aluminum, steel, stainless steel, brass and bronze.

[00065] The bead forming the bridge between the conductive wire or

ribbon and the top surface of the PV cells(s) can be made of any material and

applied by any method that is capable of laying down the bead within a pre-

defined area of the top surface of the PV cell(s) and bridging any gap between the

edge of that surface and the adjacent edge of the wire or ribbon. For example, a

bead of liquid solder can be applied. Alternatively, a length of solid solder can be

laid against the wire and ribbon, such that it overlaps a pre-defined portion of the top surface of the PV cell(s) and the solder subsequently melted using heating

methods. In another example, a bead or layer of conductive ink can be applied

from a dispensing device such as a nozzle or a printing screen, whereupon the ink

is dried or cured to form the finished bridge.

[00066] Another aspect disclosed here is to include reflective side walls

as part of the solar concentration module to improve light capture when the incident radiation is not normal to the focal lines of the louvers. When radiation hits the parabolic mirror at an angle other than normal to its length, the radiation will be reflected at the same angle to the other side of the normal angle. In other

words the reflected radiation will travel sideways as well as forward, when

looking from the front of the louver. Therefore, if nothing is done, a portion of the

reflected light will not hit the receiving section on the focal line of the mirror, but

rather travel past the end of the receiving section. There would also be a

commensurate portion of the receiving section at the other end of the louver that

would receive no concentrated radiation. Therefore, in this situation, a portion of the radiation falling on the louver will not be focused on to a receiving area.

[00067] According to this aspect of the current invention, this situation

can be avoided by installing additional reflective walls normal to the focal plane of

the parabolic mirrors and normal to the axis running along the length of the parabolic mirrors. If this is done, the radiation that would otherwise be lost is

reflected back and focused on to a portion of the receiving section for the

parabolic mirror.

[00068] This aspect of the invention is illustrated in Figure 12. Figure

12 depicts a cross-section view of the solar panel 400 when viewed from the front. The reflective side walls 410 and 420 and the focal plane 430 of the parabolic

mirrors (not shown) containing the receiving sections, are shown. The radiation

440, is the reflected radiation from radiation incident on the leftmost portion of the

parabolic louver. Radiation incident to the left of this radiation will be blocked by

the side wall 410, creating a shadowed area 460. The radiation 450, is the

reflected radiation from radiation incident on the rightmost portion of the parabolic louver. The dotted lines depict the path of this radiation if the sidewall 420 was not present. As is illustrated, the radiation 450 will be reflected back on

to a portion of the radiation receiving area 470. Thus, this radiation will be captured by the radiation receiver. Further, if the side wall 420 is normal to the

focal plane 430 and normal to the axis running along the length of the parabolic

mirror, then the length of the ray reflected off 420 to reach the focal plane and the

absolute angle of the light ray to 420 is the same as if the radiation were to cany on and be focused on the focal plane past the end of the receiving area (depicted

by the dotted lines). Therefore, the radiation 450 reflected from the side wall 420 will be focused onto a portion of the receiving section, and thus be correctly

captured. So, according to this aspect of the invention, although a shadowed area

460 is created when radiation incident on the parabolic louver is not normal to the

axis running long the length of the louver, a commensurate amount of extra

radiation is reflected by side wall 420 on to receiving area 470, resulting in no net loss of radiation. This allows the panel to efficiently concentrate radiation from a

wide range of angles without the need to rotate the panel to face the source of

radiation, for example the sun.

[00069] The side walls can be made of any suitable material with an

internal face that is reflective for the radiation that is bein'g concentrated.

Examples are polished aluminum sheet, polished aluminum sheet covered with a

transparent coating, nickel coated steel, bright chrome coated steel, nickel coated

brass or bronze, bright chrome coated brass or bronze, transparent plastic or glass

coated on the back surface with a reflective coating and a back side protective

layer applied, plastic with a front surface reflective coating with an optional transparent over-coat to afford protection for the reflective coating or other

methods for creating a planar reflective surface.

[00070] It is to be appreciated that Figure 12 is merely illustrative and

that this aspect of the invention works equally well for radiation traveling in from

the right side of 400, where 470 would become the shadowed area and 460 the

area receiving the extra radiation reflected off 410.

[00071] The invention is not limited to the above-described exemplary embodiments. It will be apparent, based on this disclosure, to one of ordinary skill

in the art that many changes and modifications can be made to the invention

without departing from the spirit and scope thereof.

Claims

WHAT IS CLAIMED IS:

1. An electromagnetic radiation collector, comprising:

a channeling area having an entry end for receiving the electromagnetic radiation, an exit end, and

at least one reflective wall between the entry end and the

exit end; and a radiation collection element near the exit end of the channeling

area, the radiation collection element being adapted to collect the electromagnetic

radiation.

2. The collector of claim 1, comprising a plurality of the channeling

areas and a plurality of the radiation collection elements.

3. The collector of claim 2, wherein the entry ends of the plurality of

channeling areas are adjacent to each other.

4. The collector of claim 2, wherein each of the channeling areas is

formed by a first surface for reflecting the electromagnetic radiation, and a second

surface opposite the first surface.

5. The collector of claim 4, wherein the first surface of each of the

channeling areas is parabolic and the focal area of each parabolic first surface is

one of the plurality of radiation collection elements.

6. The collector of claim 5, wherein the radiation collection elements

are photovoltaic cells.

7. The collector of claim 5, wherein the radiation collection elements

are pipes for containing a fluid that is for absorbing the radiation.

8. The collector of claim 5, wherein the first surfaces are movable

relative to the radiation collection elements.

9. The collector of claim 8, wherein the first surfaces can rotate about

their corresponding radiation collection element.

10. The collector of claim 5, wherein the radiation collection elements are sized to be only slightly larger in the surface area they cover than the surface

area covered by the radiation reflected onto the radiation collection elements by

the first surfaces.

11. The collector of claim 6, wherein the plurality of photovoltaic cells

are electrically connected to each other.

12. The collector of claim 11 , wherein an upper surface of a first

photovoltaic cell of the plurality of photovoltaic cells is electrically connected to a

lower surface of a second photovoltaic cell of the plurality of photovoltaic cells.

13. The collector of claim 12, further comprising a lower surface connector electrically connected to the lower surface of the second photovoltaic cell;

an upper surface connector electrically connected to the upper

surface of the first photovoltaic cell and electrically connected to the lower surface

connector.

14. The collector of claim 13, wherein the upper sui'face connector comprises a wire.

15. The collector of claim 14, further comprising a first bead that

electrically connects the upper surface connector to the upper surface of the first

photovoltaic cell.

16. The collector of claim 15, further comprising a second bead that

electrically connects the upper surface connector to the lower surface connector.

17. The collector of claim 14, wherein the wire is round in cross

section.

18. The collector of claim 14, wherein the wire is trapezoidal in cross

section.

19. The collector of claim 1 , wherein the channeling area is in the form of a slot and further comprising a reflective wall at each end of the slot.

20. The collector of claim 19, wherein the plane of each of the

reflective walls is normal to a lengthwise axis of the slot.

21. The collector of claim 20, wherein each of the reflective walls is planar and the plane of each of the reflective walls is normal to a plane of the

radiation collection element.

22. A control mechanism for a radiation collector where the radiation

collector is adjustable to track a moving radiation source and where the control

mechanism comprises a first sensor to monitor the ambient radiation conditions

and a second sensor to monitor the output of the radiation collector.