WO2011127575A1

WO2011127575A1 - Systems and methods for thermal and electrical transfer from solar conversion cells

Info

Publication number: WO2011127575A1
Application number: PCT/CA2011/000410
Authority: WO
Inventors: John Robert Mumford
Original assignee: John Robert Mumford
Priority date: 2010-04-13
Filing date: 2011-04-12
Publication date: 2011-10-20

Abstract

The present invention relates to cooling elements for solar conversion cells. One embodiment of the cooling element comprises a heat pipe whose evaporation end includes a generally planar surface for receiving the underside of a solar conversion cell. Another embodiment of the cooling element comprises an elongate hollow member having a first end and a second end and defining a fluid passageway therethrough, with the first end of the hollow member supporting and in thermal communication with a generally planar surface for receiving the underside of a solar conversion cell. Preferably, in both embodiments at least a portion of the generally planar surface is electrically conductive and coupled to an electrical pathway defined along the heat pipe or hollow member, respectively, exteriorly of the interior volume thereof. The cooling elements may be arranged end to end to facilitate electrical and thermal transfer.

Description

SYSTEMS AND METHODS FOR THERMAL AND ELECTRICAL TRANSFER FROM

SOLAR CONVERSION CELLS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to United States Provisional Application No.

61/323838 filed on April 13, 2010, United States Provisional Application No. 61/348736 filed on May 26, 2010 and United States Provisional Application No. 61/427177 filed on December 25, 2010, the teachings of each of which are hereby incorporated by reference.

FIELD OF INVENTION

[0002] The present invention relates to the conversion of solar energy into electrical energy, and more particularly to the transfer of thermal and electrical energy from solar conversion cells.

BACKGROUND OF THE INVENTION

[0003] Manufacturers of solar harvesters use various combinations of mirrors and lenses to concentrate light from a large collecting area onto a second smaller area where a solar conversion cell, that is, a device which converts solar energy into electrical energy, is located. This increased concentration of sunlight beneficially results in more electricity being generated by the solar conversion cell, but also results in significantly more heat energy being localized within or near that cell. This heat energy must be efficiently removed to maintain the operating efficiency of, and to prevent damage to, the solar conversion cell. The substantial generation of heat also creates the potential for damage to the solar harvester because of the different coefficients of thermal expansion of the different materials used to construct solar energy collectors.

SUMMARY OF THE INVENTION

[0004] In one aspect, the present invention is directed to a cooling element for a solar conversion cell. The cooling element comprises a heat pipe having an evaporation end which receives heat and a condensation end which releases heat, and the evaporation end of the heat pipe includes a generally planar surface for receiving an underside of the solar conversion cell. [0005] In one embodiment, at least a portion of the generally planar surface is electrically conductive and a heat pipe electrical pathway is defined along the heat pipe, exteriorly of the interior volume of the heat pipe, with the electrically conductive portion of the generally planar surface in electrical communication with the heat pipe electrical pathway.

[0006] The cooling element may be incorporated as part of a cooling and electrical transfer assembly which also comprises an extension member supported by the heat pipe and having a first end adjacent the condensation end of the heat pipe and a second end remote from the condensation end of the heat pipe. Spaced apart electrical contacts extend from the second end of the extension member, and an extension member electrical pathway is defined along the extension member, in electrical communication with the heat pipe electrical pathway and with the electrical contacts.

[0007] A plurality of such cooling and electrical transfer assemblies may be further assembled into a cooling and electrical transfer system for a plurality of solar conversion cells by assembling the cooling and electrical transfer assemblies end to end. For at least one pair of cooling and electrical transfer assemblies, the generally planar surface at the evaporation end of the heat pipe of one of the cooling elements is disposed between the spaced apart electrical contacts of the other one of the cooling elements, and there exists a gap in electrical communication between the generally planar surface and the spaced apart electrical contacts.

[0008] The cooling and electrical transfer system may form part of a solar harvester assembly. Such a solar harvester assembly includes at least two solar conversion cells. For at least one of the solar conversion cells, the lower surface of the solar conversion cell is supported by the generally planar surface of the evaporation end of the heat pipe of one of the cooling and electrical transfer assemblies in electrical and thermal communication therewith, and the upper surface of the solar conversion cell is in electrical communication with the spaced apart electrical contacts of the other cooling and electrical transfer assembly. The gap in electrical communication between the generally planar surface and the spaced apart electrical contacts of the other one of the cooling and electrical transfer assemblies is bridged by the solar conversion cell, and is preferably further bridged by a bypass diode connected in parallel with the solar conversion cell.

[0009] In a preferred embodiment of the solar harvester assembly, each solar conversion cell is hermetically sealed inside an inert interior volume partially defined by a housing which forms a Cassegrain solar concentrator. More preferably, each housing which forms each respective Cassegrain solar concentrator is a unitary, monolithic housing. A plug is hermetically sealed to the housing so as to cooperate with the housing to define the interior volume. The generally planar surface of the evaporation end of the heat pipe of one cooling and electrical transfer assembly is disposed inside the plug, and the heat pipe extends outwardly from the generally planar surface of the evaporation end thereof through the plug and is hermetically sealed therewith. At least one of the extension member and the spaced apart electrical contacts of the other cooling and electrical transfer assembly extends into the plug and is hermetically sealed therewith.

[0010] The electrically conductive portion of the generally planar surface, the heat pipe electrical pathway and the extension member electrical pathway may be defined by electrically conductive surface coatings on the generally planar surface, the heat pipe and the extension member, respectively.

[0011] In another aspect, the present invention is directed to a cooling element for a solar conversion cell. The cooling element comprises an elongate hollow member having a first end and a second end and defining a fluid passageway therethrough. The first end of the hollow member supports and is in thermal communication with a generally planar surface for receiving the underside of the solar conversion cell.

[0012] In an embodiment, at least a portion of the generally planar surface is electrically conductive, and an electrical pathway is defined along the hollow member, exteriorly of the interior volume of the hollow member, with the electrically conductive portion of the generally planar surface in electrical communication with the electrical pathway. In a particular embodiment, spaced apart electrical contacts extend from the second end of the hollow member and are in electrical communication with the electrical pathway.

[0013] A plurality of such cooling elements may be assembled into a cooling and electrical transfer system for a plurality of solar conversion cells by assembling the cooling elements end to end. For at least one pair of cooling elements, the generally planar surface at the first end of the hollow member of one of the cooling elements is disposed between the spaced apart electrical contacts of the other cooling element. There is a gap in electrical

communication between the generally planar surface and the spaced apart electrical contacts.

[0014] The cooling and electrical transfer system may be incorporated into a solar harvester assembly comprising at least two solar conversion cells. For at least one of the solar conversion cells, the bottom surface of the solar conversion cell is supported by the generally planar surface at the first end of the hollow member of one of the cooling elements in thermal and electrical communication therewith, and the upper surface of the solar conversion cell is in electrical communication with the spaced apart electrical contacts of the other cooling element. The gap in electrical communication between the generally planar surface and the spaced apart electrical contacts is bridged by the solar conversion cell, and is preferably further bridged by a bypass diode connected in parallel with the solar conversion cell.

[0015] In a preferred embodiment of the solar harvester assembly, each solar conversion cell is hermetically sealed inside an inert interior volume partially defined by a housing which forms a Cassegrain solar concentrator. More preferably, each housing which forms each respective Cassegrain solar concentrator is a unitary, monolithic housing. A plug is hermetically sealed to the housing so as to cooperate with the housing to define the interior volume. The generally planar surface at the first end of the hollow member of one cooling element is disposed inside the plug, and the hollow member extends outwardly from the generally planar surface through the plug and is hermetically sealed therewith, and at least one of the hollow member and the spaced apart electrical contacts of the other cooling element extends into the plug and is hermetically sealed therewith. [0016] In one embodiment, a portion of the hollow member extending between adjacent plugs is encapsulated in a vacuum defined by an annular housing surrounding that portion of the hollow member.

[0017] The electrically conductive portion of the generally planar surface and the electrical pathway may be defined by electrically conductive surface coatings on the generally planar surface and the hollow member, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings wherein:

FIGURE 1 is a simplified schematic representation of a cooling and electrical transfer element for a solar conversion cell, according to an aspect of the present invention;

FIGURE 2 is a simplified schematic representation showing the cooling and electrical transfer element of Figure 1 in thermal communication with a thermal transfer assembly;

FIGURE 3a is an isometric view of an exemplary first embodiment of a cooling element according to an aspect of the present invention;

FIGURE 3b is an isometric cut-away view of the cooling element of Figure 3a;

FIGURE 4a is an isometric view of an exemplary cooling and electrical transfer assembly according to an aspect of the present invention, including the cooling element of Figure 3a;

FIGURE 4b is an isometric cut-away view of the cooling and electrical transfer assembly of Figure 4a;

FIGURE 5 is an isometric view showing portions of two of the cooling and electrical transfer assemblies of Figure 4a positioned end to end; FIGURE 6 is a close-up isometric cut-away view of the two cooling and electrical transfer assemblies of Figure 5, with a solar conversion cell and bypass diode mounted thereto and disposed inside a plug;

FIGURES 7a and 7b illustrate schematically a modified Cassegrain optical arrangement for a solar concentrator;

FIGURE 8 is an isometric view of an exemplary Cassegrain solar concentrator according to an aspect of the present invention;

FIGURE 9 is an isometric cut-away view of an exemplary solar harvester formed from a monolithic housing of unitary, single-piece construction hermetically sealed to the plug of Figure 6 with the cooling and electrical transfer assemblies of Figure 5 and the solar conversion cell and bypass diode of Figure 6 mounted inside the plug;

FIGURE 10 is an isometric cut-away view of the solar harvester of Figure 9 assembled in cooperation with a thermal transfer assembly;

FIGURE 11 is an isometric cut-away view of the solar harvester of Figure 9 and the thermal transfer assembly of Figure 10 modified to include vacuum isolation tubes;

FIGURE 12 is an isometric view of an array of the solar harvesters of Figure 9;

FIGURE 13a is an isometric view of an exemplary second embodiment of a cooling element according to an aspect of the present invention;

FIGURE 13b is an isometric cut-away view of the cooling element of Figure 13a;

FIGURE 14 is a close-up isometric view of a portion of a cooling system for a plurality of solar cells comprising a plurality of the cooling elements of Figure 13a, with a solar conversion cell and bypass diode mounted thereto;

FIGURE 15 is an isometric partial cut-away view of an array of solar harvesters coupled to the cooling system of Figure 14, modified to include vacuum isolation tubes; FIGURE 16 is an isometric view of a cooling and electrical transfer assembly according to an aspect of the present invention, configured for air cooling; and

FIGURE 17 shows a physical schematic representation of electrical pathways alongside a corresponding representative electrical schematic.

DETAILED DESCRIPTION

[0019] Referring first to Figure 1, a simplified schematic representation of a cooling element for a solar conversion cell is shown generally at 100. The cooling element 100 is a heat pipe assembly comprising an evaporator section 101, a heat pipe body 102, a heat pipe wick 103 and a condenser section 104. The evaporator section 101 of the heat pipe 100 also acts as the mounting element for a solar conversion cell 105, and includes a generally planar surface for this purpose. The evaporator section 101 is manufactured from material having a similar coefficient of thermal expansion as the heat pipe body 102, and which can form a hermetic seal therewith. For example, where the heat pipe body 102 is made of borosilicate glass then a suitable nickel-iron alloy such as Kovar® could be used to manufacture the evaporator section 101. As is known in the art, Kovar is a nickel-cobalt ferrous alloy having thermal expansion characteristics compatible with those of borosilicate glass, which enables direct physical connections with borosilicate glass. Where Kovar is referred to herein, other suitable alloys may be substituted for Kovar so long as they are dimensionally stable under thermal expansion and can form a hermetic seal with borosilicate glass.

[0020] The evaporator section 101 is sealed to heat pipe body 102, e.g. by flame sealing, and a woven glass wick 103 is inserted in the heat pipe body 102. Alternatively a sintered glass bead structure could form the wick, or the wick may be defined by or small grooves formed on the inside of the heat pipe body 102.

[0021] A small amount of evaporable and condensable fluid is inserted into the heat pipe assembly 100. The fluid is shown evaporating at 107a and condensing at 107b; the heat pipe 100 has an evaporation end 109 defined by the evaporation section 101 and a condensation end 1 10 defined by the condensation section 104. Selection of a suitable fluid is within the capability of one skilled in the art, now informed by the herein disclosure. In the illustrated embodiment, the fluid comprises water that has been de-ionized and de-gassed, which water is applied to saturate the wick 103. The evaporator section 101 is heated to bring the excess water to a boil, and the condensation section 104 is then hermetically sealed to the heat pipe body 102, for example by applying a low temperature glass weld just as the heat is removed from the evaporator section 101. When the evaporator section 101 cools the hermetic seal results in the remaining fluid in the heat pipe 100 being under partial vacuum. Other suitable methods of evacuating the heat pipe 100 and assembling the parts thereof may also be used without departing from the scope of the present invention.

[0022] An extension member 108 manufactured from the same material as the heat pipe body 102 is secured to the condensation end 1 10 of the heat pipe 100 by any suitable technique, such as welding with a low temperature glass.

[0023] An electrical pathway is defined along the heat pipe 100, and at least a portion of the generally planar surface that receives the solar conversion cell 105 is also electrically conductive and is in electrical communication with the electrical pathway. In the exemplary embodiment illustrated in Figure 1 , this is achieved by depositing a layer 106 of conductive material onto the generally planar surface of the evaporation section as well as the rest of the heat pipe 100 and extension member 108, for example by vapor deposition or wet processes. The layer 106 of conductive material may be, for example, copper, silver, gold or other conductive materials or combinations thereof. The solar conversion cell 105 may be mounted to the evaporation section 101 using any suitable mounting method, for example vacuum soldering or void-free gluing with a silver filled epoxy for both electrical and thermal transfer.

[0024] Referring now to Figure 2, the cooling element 100 illustrated in Figure 1 is shown connected in thermal communication with a thermal transfer assembly 200. The thermal transfer assembly 200 comprises a thermal transfer tube 204 formed from the same material as the heat pipe body 102 and the extension member 108. The thermal transfer assembly 200 is hermetically sealed to the heat pipe body 102 and the layer 106 of conductive material, for example with a low temperature glass weld at a first sealing point 202a and is hermetically sealed to the extension member 108 and the layer 106 of conductive material, for example with a low temperature glass weld, at a second sealing point 202b so that the thermal transfer tube 204 surrounds the condensation end 1 10 of the heat pipe 100. A suitable thermal transfer fluid 201 that is chosen for appropriate dielectric, thermal transfer and freezing point characteristics flows through the thermal transfer tube 204. In this exemplary embodiment a mixture of 50% de-ionized water and 50% ethylene glycol is used. In the illustrated embodiment, the layer 106 of conductive material is further coated with a suitable dielectric insulator 203, for example Si0₂, to inhibit contamination of the thermal transfer fluid 201 and to inhibit degradation of the layer 106 of conductive material by the thermal transfer fluid 201. The thermal transfer fluid 201 carries heat away from the condensation end 1 10 of the heat pipe for storage, processing or dissipation at a remote location.

[0025] Reference is now made to Figures 3a and 3b, which illustrate the physical construction of a first embodiment of a cooling element of the type illustrated schematically in Figure 1. The cooling element is denoted generally by reference 300, and comprises a heat pipe 302 having an evaporation end 304 which receives heat and a condensation end 306 which releases heat. The main body 308 of the heat pipe 302 is formed by a hollow borosilicate glass tube. The evaporation end 304 of the heat pipe 302 includes a generally planar surface 310 (Figure 3a) for receiving the underside of a solar conversion cell (not shown in Figures 3a and 3b). As was described above and shown schematically in Figures 1 and 2, and as illustrated in Figure 6, a layer 620 of conductive material will be applied to the cooling element 300 along the upper surface thereof so that at least a portion of the generally planar surface 310 is electrically conductive and a heat pipe electrical pathway is defined along the heat pipe 302, exteriorly of an interior volume 314 (Figure 3b) of the heat pipe 302, with the electrically conductive portion of the generally planar surface 310 in electrical communication with the heat pipe electrical pathway.

[0026] A block 316 (Figure 3a) of suitable metal or ceramic material capable of forming a seal with glass, for example ovar, is machined to the desired shape, and forms the evaporation end 304 of the heat pipe 302 and also defines the generally planar surface 310 that will receive the solar conversion cell (not shown in Figures 3a and 3b). A first bore 318 (Figure 3b) is defined in one end of the block 316, for example by drilling, and a first end 320 of the main body 308 of the heat pipe 302 is received in the first bore 318, the outer end of which is dimensioned to accommodate the first end 320 (Figure 3 b) of the main body 308 of the heat pipe 302. The first end 320 of the main body 308 of the heat pipe 302 is hermetically sealed to the block 316, for example by flame sealing. In an alternative embodiment, the block 316 may also be formed of borosilicate glass and may be of unitary, single-piece construction with the main body 308, with a layer of suitable metal, for example Kovar, sealed to at least a portion of the outer surface of the block 316 including the generally planar surface 310.

[0027] A suitable wick 322 (Figure 3b) is disposed on the interior wall of the main body 308 of the heat pipe 302. The wick 322 may be, for example, woven fiber glass or sintered particulate glass formed on the interior wall or inserted into the main body 308 of the heat pipe 302, or may be defined by grooves on the interior wall of the main body 308 of the heat pipe 302. De-ionized and de-gassed water, or some other appropriate evaporable and condensable fluid, is inserted into the main body 308 of the heat pipe 302 in just sufficient volume to saturate the wick 322 and to boil off to form the required vacuum.

[0028] The condensation end 306 of the heat pipe 302 is defined by a thermal transfer element 324 also made from a suitable metal or ceramic material, such as Kovar, which includes a second bore 326 which receives the second end 328 of the main body 308 of the heat pipe 302. The second end 328 of the main body 308 of the heat pipe 302 is hermetically sealed to the thermal transfer element 324, for example by flame sealing. In this exemplary embodiment the thermal transfer element includes cooling fins 330 (Figure 3b) to enhance thermal transfer.

[0029] Reference is now made to Figures 4a and 4b, in which an embodiment of a cooling and electrical transfer assembly according to an aspect of the present invention is shown generally at 400. The cooling and electrical transfer assembly 400 comprises a cooling element 300 as shown in Figures 3 a and 3 b, and further comprises an extension member 402 supported by the heat pipe 302 and having a first end 404 adjacent the condensation end 306 of the heat pipe 302 and a second end 406 remote from the condensation end 306 of the heat pipe 302. In the illustrated embodiment, the extension member 402 is a hollow tube 409 made of borosilicate glass and is secured to the condensation end 306 of the heat pipe 302 by welding the first end 404 of the extension member 402 to the thermal transfer element 324 with low temperature glass. In other embodiments, the extension member may comprise, for example, a solid rod.

[0030] A pair of spaced apart electrical contact members 408 extend from the second end 406 of the extension member; in the illustrated embodiment a crossbar 410 is secured to the extension member 402 adjacent and inwardly spaced from the second end 406 thereof, and the electrical contact members 408 are carried by the crossbar 410. The electrical contact members 408 and crossbar 410 may be formed from borosilicate glass and may be flame welded in place, or may be formed unitarily with the extension member 402. In the illustrated embodiment, the cooling and electrical transfer assembly 400 is assembled such that the upper surfaces of the electrical contact members 408 are generally co-planar with the generally planar surface 310.

[0031] As was shown schematically in Figures 1 and 2 and as will be illustrated in Figure 6, a layer 622 of conductive material is applied to the surface of the extension member 402 and to the surface of the electrical contact members 408 and the crossbar 410 so that the electrical contact members 408 become electrical contacts. As a result, an extension member electrical pathway is defined along the extension member 402, with the electrical contacts formed by the electrical contact members 408 being in electrical communication with the extension member electrical pathway. In the completed cooling and electrical transfer assembly 400, the extension member electrical pathway (defined by the layer 622 of conductive material shown in Figure 6) is in electrical communication with the heat pipe electrical pathway (defined by the layer 620 of conductive material), for example by overlapping the layers 620, 622 of conductive material on the thermal transfer element 324, or by the use of jumper wires, or the like.

[0032] Figure 5 shows the physical arrangement of two adjacent cooling and electrical transfer assemblies 400 to form a portion of a cooling and electrical transfer system for a plurality of solar conversion cells. The cooling and electrical transfer system comprises a plurality of cooling and electrical transfer assemblies 400 as shown in Figures 4a and 4b, assembled end to end. As can be seen in Figure 5, for at least one pair of cooling and electrical transfer assemblies 400, the generally planar surface 310 at the evaporation end 304 of the heat pipe 302 of one of the cooling and electrical transfer assemblies 400 is disposed between the spaced apart electrical contact members 408 of the other one of the cooling and electrical transfer assemblies 400. The two cooling and electrical transfer assemblies 400 are secured relative to one another so as to define a physical gap 502, and a corresponding gap in electrical communication when conductive coatings 620, 622 are applied, between the generally planar surface 310 and the spaced apart electrical contact members 408 and crossbar 410. Since the crossbar 410 is inwardly spaced from the second end 406 of the extension member 402, the correct distance between the cooling elements can be established by welding the second end 406 of the extension member 402 to the block 316 of the adjacent cooling and electrical transfer assembly 400. Preferably, the two cooling and electrical transfer assemblies 400 are oriented such that the upper surfaces of the electrical contact members 408 of each cooling and electrical transfer assembly 400 are co-planar with the generally planar surface 310 of the adjacent cooling and electrical transfer assembly 400, and with an equal gap between the edges of the block 316 and the crossbar 410 and electrical contact members 408. The above-described pattern can be repeated to interleave the desired number of cooling and electrical transfer assemblies 400 to form a cooling and electrical transfer system of desired size.

[0033] A cooling and electrical transfer system as shown in Figure 5 may form part of a solar harvester. With reference now to Figure 6, a portion of a solar harvester according to an aspect of the present invention is shown. Such a solar harvester will typically comprise a cooling and electrical transfer system as shown in Figure 5, together with at least two solar conversion cells 610 (only one of which is shown in Figure 6).

[0034] As illustrated in Figure 6, two cooling and electrical transfer assemblies 400 are connected end to end, as was illustrated in Figure 5. The bottom surface 612 of the solar conversion cell 610 is secured to the generally planar surface 310 of the evaporation end 304 of the heat pipe 302 of one of the cooling elements 300. The bottom surface 612 of the solar conversion cell 610 is secured so that it is in electrical communication with the generally planar surface 310, and in particular the layer 620 of conductive material. In the illustrated embodiment, the layer 620 of conductive material is a layer of vacuum vapor deposited silver with a flash of gold. For each cooling and electrical transfer assembly 400, the layer 620 of conductive material is plated to an adequate thickness along the generally planar surface 310, the main body 308 of the heat pipe 302 and the thermal transfer element 324, and the layer 622 of conductive material is plated to an adequate thickness along the extension member 402, the crossbar 410 and the electrical contact members 408, to accommodate the electrical current capacity of the solar conversion cells 610. The layer 622 of conductive material is not applied to the portion of the end 406 of the extension member 402 that extends beyond the crossbar 410, thereby defining the gap 502 between the generally planar surface 310 and the spaced apart electrical contact members 408 of the adjacent cooling and electrical transfer assembly 400, thus maintaining dielectric integrity. Those skilled in the art will understand that a variety of coating processes may be used to coat desired parts of the cooling and electrical transfer assemblies 400 while leaving other portions uncovered; for example suitable masking techniques may be used.

[0035] The upper surface 614 of the solar conversion cell 610 is in electrical communication with the spaced apart electrical contacts defined by the electrical contact members 408; more particularly, the upper surface 614 of the solar conversion cell 610 is in electrical

communication with the coating 622 of electrically conductive material disposed on the upper surface of the electrical contact members 408. Specifically, the solar conversion cell 610 includes a plurality of electrically conductive connectors 616 coupled to its upper surface 614 by way of bus bars 615. The connectors 616 are electrically connected, for example by gold wire bonding, soldering or conductive epoxy, to the coating 622 of electrically conductive material disposed on the upper surface of the of the electrical contact members 408. In the illustrated embodiment, the lower surface 612 of the solar conversion cell 610 is bonded to the conductive coating 620 on the generally planar surface 310 with an electrically conductive epoxy 608, specifically a silver filled epoxy 608 applied in a vacuum environment to provide a substantially void-free bond that is both electrically and thermally conductive. As a result, the gap in electrical communication between the electrically conductive coating 620 on the generally planar surface 310 and the spaced apart electrical contacts defined by the conductive coating 622 on the electrical contact members 408 is bridged by the solar conversion cell 610.

[0036] Thus, current can flow from the coating 622 on the extension member 402 of one of the cooling and electrical transfer assemblies 400 through the connectors 616 to the upper surface 614 of the solar conversion cell 610, through the solar conversion cell 610 to its bottom surface and then to the coating 620 on the generally planar surface 310 of the adjacent cooling and electrical transfer assembly 400.

[0037] The gap in electrical communication between the conductively coated generally planar portion 310 and the adjacent electrical contacts defined by the coated electrical contact members 408 is further bridged by a bypass diode 624 connected in parallel with the solar conversion cell 610. Specifically, the bypass diode 624 is bonded to the conductive coating 622 on the extension member 402 on the first cooling and electrical transfer assembly 400, in particular the conductive coating 622 on one of the electrical contact members 408, and to the conductive coating 620 on the heat pipe 302 of the adjacent cooling and electrical transfer assembly 400. As can be seen, one of the electrical contact members 408 is longer than the other to accommodate the bypass diode 624.

[0038] In a preferred embodiment, each solar conversion cell is hermetically sealed inside an inert interior volume partially defined by a housing which forms a Cassegrain solar concentrator, details of which will be described below. In this embodiment, for each pair of cooling and electrical transfer assemblies 400, the solar conversion cell 610, the bypass diode 624, the second end 406 of the extension member 402, including the crossbar 410 and electrical contact members 408, and the evaporation end 304 of the heat pipe 302, including the block 316, are hermetically encapsulated inside a hollow plug 626, which may be formed from borosilicate glass. The hollow glass plug may be formed, for example, by welding together two half cylinders 628 of borosilicate glass each having an open upper end, a bottom wall 630 and apertures 632, 634 in the side wall for the extension member 402 and heat pipe main body 308. Once the plug 626 is assembled, the apertures 632, 634 may be hermetically sealed using low temperature glass.

[0039] Reference is now made to Figures 7a and 7b, which illustrate schematically a modified Cassegrain optical arrangement for a solar concentrator with which cooling and electrical transfer assemblies according to aspects of the present invention may

advantageously be used.

[0040] Referring first to Figure 7a, the Cassegrain solar concentrator 700 comprises a concave primary reflector 702 and a convex secondary reflector 704 opposed to the primary reflector 702. Those skilled in the art will understand that the primary reflector 702 and secondary reflector 704 may comprise any suitable combination of spherical, parabolic and hyperbolic shapes. In the illustrated embodiment, the primary reflector 702 is parabolic and the secondary reflector 704 is hyperbolic. The secondary reflector 704 is disposed between the primary reflector 702 and the primary focus 702_PF of the primary reflector 702. The primary focus 704p_F of the secondary reflector 704 is coincident with the primary focus 702PF of the primary reflector 702, and the secondary focus 704SF is disposed between the secondary reflector 704 and the solar collection area 708. A central aperture 706 is defined in the primary reflector 702, in registration with the secondary reflector 704, to permit light reflected from the secondary reflector 704 to reach the solar collection area 708. A solar conversion cell, such as the solar conversion cell 610 illustrated above, may be disposed at the solar collection area 708.

[0041] As is known in the art, a tracking system (not shown) may be used to aim the solar concentrator 700 toward the sun. Incoming solar radiation is substantially collimated, and is represented schematically as substantially parallel light rays L. The incident light rays L are reflected from the primary reflector 702 towards the primary focus 702_PF of the primary reflector 702. The secondary reflector 704 intercepts and reflects the light rays L through the secondary focus 704_SF, and the light rays L then diverge to blanket the solar collection area 708. [0042] Recapturing reflectors 710 are aligned with the perimeter of the solar collection area 708. In the illustrated embodiment, the recapturing reflectors 710 comprise planar members that extend from the solar collection area 708 through the central aperture 706 substantially parallel to a notional line (shown as a dashed line) passing through the primary focus 702PF of the primary reflector 702 and the primary and secondary focus 704_PF, 704SF of the secondary reflector 704.

[0043] As shown in Figure 7b, when the solar concentrator 700 is not pointed directly at the sun, for example due to vibration from wind, tracking system errors and misalignments resulting from variances in manufacturing tolerances, it will be misaligned with the incoming solar radiation represented by substantially parallel light rays L. In Figure 7b, a misalignment of 0.5 degrees is shown. As can be seen, the light rays L are still reflected from the primary reflector 702 to the secondary reflector 704, but when reflected from the secondary reflector 704 do not pass through the secondary focus 704SF thereof, but instead through a shifted secondary focus 704SSF- At least some of the light rays L that would otherwise not reach the solar collection area 708 are reflected by the recapturing reflectors 710 back toward the solar collection area 708.

[0044] Determination of appropriate size, shape and materials for the primary reflector 702 and the central aperture 706 therein, the secondary reflector 704, and the recapturing reflectors 710 are within the capabilities of one skilled in the art, now informed by the herein disclosure.

[0045] Reference is now made to Figure 8 which shows an exemplary physical construction 830 of the Cassegrain solar concentrator 700 shown schematically in Figures 7a and 7b.

Specifically the exemplary solar concentrator 830 comprises a primary reflector 802, a secondary reflector 804, with a central aperture 806 defined in the primary reflector 802. An optically transparent, planar cover member 812 extends across the primary reflector 802 and carries the secondary reflector 804. The cover member 812 and the primary reflector 802 are hermetically sealed to one another to define a housing 832. Four planar recapturing reflectors 810 extend from the solar collection area (not shown in Figure 8) through the central aperture 806 into the interior volume defined and enclosed by the primary reflector 802 and the cover member 812. The recapturing reflectors 810 are supported by support members 814 extending from a cylindrical collar 816 that depends downwardly from the central aperture 806. In one embodiment, the cylindrical collar 816 will nest with and be hermetically sealed to the plug 626 described above in the context of Figure 6, with an inert environment, such as a vacuum or an inert gas, inside the interior volume enclosed by the plug 626 and housing 832.

[0046] In the illustrated embodiment, the primary reflector 802, secondary reflector 804, cover member 812 and recapturing reflectors 810, as well as the plug 626, are each made from borosilicate glass. The primary reflector 802 and secondary reflector 804 are coated with a reflective material, such as vacuum-deposited silver, which is protected by the inert environment. The recapturing reflectors 810 may also be coated with a reflective material, or may be transparent and provide reflection because their optical index of refraction is substantially higher than that of the vacuum or inert gas through which the light waves L are traveling.

[0047] In operation, the solar collector 830 will be aimed toward the sun by a suitable tracking system. Incoming substantially collimated solar radiation, represented by incident light rays L, are first reflected from the surface of the primary reflector 802 towards the secondary reflector 804. From the secondary reflector 804 the light rays are reflected into a collection aperture 818 defined by the upper edges of the four recapturing reflectors 810. From there, the light rays L continue either directly or by reflection to the solar collection area and are effectively contained between the recapturing reflectors 810.

[0048] While the solar collector 830 shown in Figure 830 comprises a plurality of

components secured to one another, in a preferred embodiment a Cassegrain solar collector according to an aspect of the present invention comprises a single-piece monolithic housing of unitary construction. Examples of Cassegrain solar collectors formed from single-piece monolithic housings of unitary construction, and methods for making them, are taught in United States Provisional Application No. 61/323838 filed on April 13, 2010 and United States Provisional Application No. 61/427177 filed on December 25, 2010 and in a Patent Cooperation Treaty application in the name of the inventor hereof and claiming priority to United States Provisional Applications No. 61/323838 and 61/427177, the teachings of which are hereby incorporated by reference.

[0049] Referring now to Figure 9, another embodiment of a solar harvester according to an aspect of the present invention is shown generally at 900. The solar harvester comprises a solar collector 930 comprising a single-piece monolithic borosilicate glass housing 932 of unitary construction. The housing 932 comprises a primary reflector 902 having a central aperture 906, a secondary reflector 904 in registration with the central aperture 906 and an optically transparent cover member 912, each of which is defined by the shape of the monolithic housing 932. The monolithic housing 932 also includes a cylindrical collar 916 that depends downwardly from the central aperture 906. A reflective coating of silver is deposited on the interior surface portions that define the primary and secondary reflectors 902, 904. Four recapturing reflectors 910 are supported by support members 914 extending from the collar 916, each recapturing reflector 910 disposed at a right angle to each adjacent recapturing reflector 910. The recapturing reflectors 910 are generally planar, and are oriented perpendicularly to the generally planar cover member 912.

[0050] The monolithic housing 932 is hermetically sealed to the cylindrical borosilicate glass plug 626 as described above so as to cooperate therewith to define a hermetically sealed interior volume. Specifically, the collar 916 on the housing 932 is received inside the cylindrical side wall 636 of the plug 626 and hermetically sealed therewith, for example by welding with low temperature glass.

[0051] As described above in the context of Figure 6, a number of components are assembled inside the plug 626, and will therefore be hermetically sealed within the internal volume defined by the plug 626 and the monolithic housing 932. For ease of reference, the components disposed inside the plug 626 are a solar conversion cell 610, a bypass diode 624, the second end 406 of an extension member 402 of a first cooling and electrical transfer assembly (including the crossbar 410 and electrical contact members 408), and the

evaporation end 304 of the heat pipe 302 (including the block 316) of an adjacent thermal and electrical transfer assembly. Thus, the generally planar portion 310 is disposed inside the plug 626 while the heat pipe 302 extends outwardly from the generally planar portion 310 through the cylindrical side wall 636 of the plug 626 and is hermetically sealed therewith. Similarly, the extension member 402 extends through the cylindrical side wall 636 into the plug 626 and is hermetically sealed therewith, with the electrical contact members 408 and crossbar 410 sealed inside the plug 626. The solar conversion cell 610 electrically connects the adjacent cooling and electrical transfer assemblies 400 as was described above in the context of Figure 6.

[0052] As can be seen, when the plug 626 and housing 932 are assembled, the solar conversion cell 626 is disposed precisely at the solar collection area of the solar collector 930, in registration with the central aperture 906 and with the collection aperture 918 defined by the upper edges of the four recapturing reflectors 910. The lower edges of the four recapturing reflectors 910 do not touch the solar conversion cell but are disposed immediately thereabove.

[0053] In operation, incoming solar radiation passes through the optically transparent cover member 912 to the primary reflector 902, which reflects them to the secondary reflector 904, which focuses the light rays to a point located inside the volume 936 defined by the four recapturing reflectors 910. When the solar harvester 900 is properly aimed at the sun so that the light rays L are orthogonal to the cover member 912, the incoming light rays L will be substantially uniformly distributed across the upper surface 614 of the solar conversion cell 610. In the event that the solar harvester 900 is misaligned, the reflected light rays will still enter the collection aperture 918 defined by the upper edges of the four recapturing reflectors 910 and thus at least a portion of the light that would have been lost is redirected by the recapturing reflectors 910 back onto the solar conversion cell 610 for harvesting.

[0054] Because the lower surface 612 (Figure 6) of the solar conversion cell 610 is electrically coupled to the conductive coating 620 on the outer surface of the heat pipe 302, current generated by the solar conversion cell 610 will travel along the electrical pathway defined by the conductive coating 620. Moreover, because the lower surface 612 (Figure 6) of the solar conversion cell 610 is bonded to and hence in thermal communication with the generally planar surface 310 of the block 316 at the evaporation end 304 of the heat pipe 302, the heat pipe 302 will carry heat away from the solar conversion cell 610.

[0055] Referring now to Figure 10, the solar harvester 900 is shown assembled in cooperation with a thermal transfer assembly 1000 which follows principles similar to those of the thermal transfer assembly 200 illustrated schematically in Figure 2. The condensing end 306 of the heat pipe 302 of a cooling and electrical transfer assembly 400, including the thermal transfer element 324, is hermetically sealed inside a thermal transfer tube 1002, which in the illustrated embodiment is a borosilicate glass pipe. Specifically, the thermal transfer tube 1002 is sealed around a portion of the main body 308 of the heat pipe 302 adjacent the condensing end 306 thereof and around the first end 404 of the extension member 402. For example, the thermal transfer tube 1002 may be formed by welding together two halves having cutouts for the heat pipe 302 and extension member 404. A thermal transfer fluid may flow through the thermal transfer tube 1002 to carry heat away from the thermal transfer element 324 for storage, processing or dissipation. In one embodiment, the thermal transfer fluid is nonconductive, in another embodiment a nonconductive coating is applied to the thermal transfer element 324 and to the encapsulated portions of the main body 308 of the heat pipe 302 and the extension member 402.

[0056] Figure 1 1 shows an optional configuration of the solar harvester 900 and thermal transfer assembly 1000 shown in Figure 10, in which the cooling and electrical transfer assemblies 400 and thermal transfer tubes 1002 are encapsulated within vacuum isolation tubes 1 102, 1 104, respectively. For example, tube halves may be assembled around the cooling and electrical transfer assemblies 400 and thermal transfer tubes 1002, flame welded together and evacuated. The respective evacuated volume 1106, 1 108 between the cooling and electrical transfer assemblies 400 and thermal transfer tubes 1002 and the respective vacuum isolation tubes 1 102, 1 104 forms a thermal insulation barrier.

[0057] As illustrated in Figure 12, solar harvesters 900 (Figures 9, 10 and 1 1), including associated plugs 626 (Figures 6, 9, 10 and 1 1) and cooling and electrical transfer elements 400 (Figures 4, 5, 6, 9, 10 and 1 1), and thermal transfer assemblies 1000 (Figures 10 and 1 1) may be assembled into arrays, such as the exemplary array 1200 which comprises a 2 x 4 array of eight solar harvesters 900. The solar conversion cells of each of the solar harvesters 900 in each row of four are connected in series, and the rows of four connected in series by an electrical connector 1202. The electrical input and output connections 1204a, 1204b of the array, which are electrically coupled to electrical pathways on the cooling and electrical transfer elements 400, are coupled to an electrical supply system shown schematically at 1206, and the fluid inlets and outlets 1208a, 1208b of the array 1200, which are in fluid

communication with the thermal transfer tubes 1002 of the thermal transfer assembly 1000 of the array 1200, are connected in fluid communication with a thermal processing system shown schematically at 1210. The direction of fluid flow is shown by the arrows 1214. In the exemplary array 1200, a transparent cover plate 1212 is disposed over the transparent cover members 912 of the solar harvesters 900; the cover plate 1212 may optionally be omitted. The array 1200 may be mounted on any suitable solar tracking system to maintain its orientation toward the sun.

[0058] As can be seen, in the array 1200 shown in Figure 12, the cooling and electrical transfer assemblies 400 for each row of four solar harvesters 900 are oriented in opposite directions; depending on the orientation of the array 1200 some of the heat pipes 302 will have gravity assistance in returning the evaporable and condensable fluid while other heat pipes 302 will rely on the capillary action of the wick 322.

[0059] In alternate embodiments, cooling and electrical transfer assemblies similar to the cooling and electrical transfer assemblies 400 may be used, but in which heat carried away from the solar conversion cells 610 is dissipated into the ambient environment rather than being collected by a thermal transfer fluid. Figure 16 shows an exemplary cooling and electrical transfer assembly 1600 comprising a cooling element 300A and an extension member 402A. The cooling elements 300A are identical to the cooling elements 300 illustrated above, except that the main body 308A of the heat pipe 302A includes an upward bend 1602 and instead of the smaller thermal transfer element 324, the condensation end

306A of the heat pipe 302A comprises a much larger air cooling element 324A formed from a suitable material, such as Kovar, and having large cooling fins 330A. The extension member 402A is identical to the extension member 402, except that it is attached at a downward angle to the condensation end 306 A of the heat pipe 302, and includes an upward bend immediately ahead of the crossbar 41 OA, so that the upper surfaces of the electrical contact members 408 A are coplanar with the generally planar surface 310A defined by the block 1316 at the evaporation end 304A of the heat pipe 302A. Similarly to the cooling and thermal transfer assembly 400, respective conductive coatings 620A, 622A are applied to the cooling element 300 A, including the generally planar surface 31 OA on the block 316 A, and to the extension member 402 A, including the crossbar 41 OA and the electrical contact members 408 A. Thus, two cooling and electrical transfer assemblies 1600 can be assembled end to end, with the block 316A, including the generally planar surface 31 OA, of a first cooling and electrical transfer assembly 1600 disposed between the electrical contacts defined by the electrical contact members 408 A of a second cooling and electrical transfer assembly 1600, with the resulting electrical gap bridged by a solar conversion cell 610 in the manner described above. All or a portion of the air cooling element 324A may be coated with conductive material as shown in Figure 16, or jumper wires or other techniques may be used to electrically connect the heat pipe electrical pathway and the extension member electrical pathway. The extension member 402A is shown as mounted to the air cooling element 324A; in other embodiments it may be mounted directly to the main body 308A of the heat pipe 302A.

[0060] Reference is now made to Figures 13a and 13b, which show a second embodiment of a cooling element according to an aspect of the present invention. The cooling element is denoted generally by reference 1300, and comprises an elongate hollow member 1302 having a first end 1304 and a second end 1306. The first end 1304 of the hollow member 1302 supports and is in thermal communication with a generally planar surface 1310 for receiving an underside of a solar conversion cell (not shown in Figures 13a and 13b). In the illustrated embodiment, the elongate hollow member 1302 comprises a hollow borosilicate glass tube, and the generally planar surface 1310 is defined by a block 1316.

[0061] The block 1316 is formed from metal or ceramic material capable of forming a seal with glass, for example Kovar, and is machined to the desired shape which defines the generally planar surface 1310 that will receive the solar conversion cell (not shown in Figures 13a and 13b). A bore 1318 passes entirely through the block 1316 and receives the first end 1304 of the hollow member 1302 in a proximal side 1340 thereof. As will be described below, the distal side 1342 of the bore will receive the second end 1306 of the hollow member 1302 of another cooling element 1300. As such, the ends of the bore 1318 are dimensioned to accommodate the ends 1304, 1306 of such elongate hollow members 1302. The first end 1304 of the hollow member 1302 is hermetically sealed to the block 1316, for example by flame sealing. In an alternative embodiment, the block 1316 may also be formed of borosilicate glass and may be of unitary, single-piece construction with the hollow member 1302 at the first end thereof, with a layer of suitable metal, for example Kovar, sealed to at least a portion of the outer surface of the block 1316 including the generally planar surface 1310.

[0062] As can be seen in Figures 13a and 13b, a suitable thermal transfer fluid (not shown) can flow into the distal side 1342 of the bore 1318 in the block 1316, through the bore 1318 and out the proximal side 1340 thereof into the first end 1304 of the hollow member 1302, and along the interior volume 1346 of the hollow member 1302 to the second end 1306 thereof. As will be explained in greater detail below, when the cooling elements 1300 are assembled into a cooling and electrical transfer system, the thermal transfer fluid can flow from the second end 1306 of the hollow member into the distal side 1342 of the bore 1318 of the block of an adjacent cooling element 1300.

[0063] A pair of spaced apart electrical contact members 1308 extend from the second end 1306 of the hollow member 1302. In the illustrated embodiment, the hollow member 1302 carries a crossbar 1314 adjacent and inwardly spaced from its second end 306, and the electrical contact members 1308 are carried by the crossbar 1314. The electrical contact members 1308 and crossbar 1314 may be formed from borosilicate glass and may be flame welded to the hollow member 1302, or may be of unitary construction with the hollow member 1302. The upper surfaces of the electrical contact members 1308 are generally co- planar with the generally planar surface 1310. [0064] The generally planar surface 1310, or at least a portion thereof, is electrically conductive, and an electrical pathway is defined along the hollow member 1302, exteriorly of the interior volume 1346 thereof, with the electrically conductive portion of the generally planar surface 1310 in electrical communication with the electrical pathway. Specifically, a layer 1322 of conductive material is applied to the generally planar surface 1310, to the surface of the hollow member 1302 and to the surface of the electrical contact members 1308 and the crossbar 1314 so that the electrical contact members 1308 become electrical contacts. As described above, the coating may advantageously comprise vacuum deposited silver with a flash of gold, plated to an adequate thickness to accommodate the electrical current generated by the solar conversion cells with which the cooling elements 1300 will be used. Thus, the conductive coating 1322 defines an electrical pathway along the hollow member 1302, with the electrical contacts formed by the electrical contact members 1308 being in electrical communication with electrical pathway. The portion of the second end 1306 of the hollow member 1302 extending beyond the crossbar 1314 is not coated with the layer 1322 of conductive material (e.g. it may be masked during the coating process), and will therefore form a dielectric barrier between adjacent cooling elements 1300 when the same are assembled end to end, so that there will be a gap in electrical communication between the generally planar surface 1310 at the first end of the hollow member 1302 of the first cooling element 1300 and the conductive coating 1322 on the spaced apart electrical contact members 1308 of the second cooling element 1302.

[0065] With reference now to Figure 14, a portion of a cooling system for a plurality of solar cells is shown generally at 1400, with a solar conversion cell 1410 mounted on the cooling system 1400. The cooling system 1400 comprises a plurality of cooling elements 1300 assembled end to end. For each pair of cooling elements 1300, the block 1316 (and hence the generally planar surface 1310) at the first end 1304 (Figure 13 a) of the hollow member 1302 of one of the cooling elements 1300 is disposed between the spaced apart electrical contact members 1308 at the second end 1306 (Figure 13a) of the adjacent cooling element 1300. A physical gap 1402 between the conductive coating 1322 on the generally planar surface 1310 of the first cooling element 1300 and the conductive coating 1322 on the crossbar 1314 and spaced apart electrical contact members 1308 of the adjacent cooling element 300 defines a gap in electrical communication between the electrical pathways on the adjacent cooling elements 1300. Preferably, there is an equal distance between the edges of the solar conversion cell 1410 and the crossbar 1314 and electrical contact members 1308. In the illustrated embodiment, the adjacent cooling members 1300 are secured together by inserting the second end 1306 of one of the hollow members 1302 into the distal side 1342 of the bore 1318 in the block 1316 of the adjacent cooling element 302 and welding it in place. The crossbar 1314 is inwardly spaced from the second end 306 sufficiently to create the physical gap 1402 and, because the portion of the hollow member 1302 extending beyond the crossbar 1314 is not coated with conductive material, this also creates the electrical gap. The two cooling elements 1300 are secured to one another so that the upper surfaces of the coated electrical contact members 1308 of one cooling element are generally coplanar with the coated generally planar surface 1310 of the adjacent cooling element.

[0066] Similarly to the first embodiment of a cooling element 300 described above, the gap in electrical communication between the conductively coated planar surface 1310 and the spaced apart electrical contacts defined by the conductive coating 1322 on the electrical contact members 1308 is bridged by a solar conversion cell 1410. The lower surface 1412 of the solar conversion cell 1410 is secured to the conductive coating 1322 on the generally planar surface 1310 by a conductive silver-filled epoxy 1408 as described above in respect of the first embodiment. A plurality of electrically conductive connectors 1416 are coupled to the upper surface 1414 of the solar conversion cell 1410 by way of bus bars 1415, and are electrically connected to the conductive coating 1322 on the upper surface of the of the electrical contact members 1308. This enables current to flow from the coating 1322 on the first cooling element 1300 through the connectors 1416 to the upper surface 1414 of the solar conversion cell 1410, through the solar conversion cell 1410 to its bottom surface 1412, through the conductive epoxy 1408 and then to the coating 1322 on the generally planar surface 1310 of the adjacent cooling element 1300. The gap in electrical communication is further bridged by a bypass diode 1424 connected in parallel with the solar conversion cell 1410. The bypass diode 1424 is bonded to the conductive coatings 1322 on the adjacent cooling elements 1300.

[0067] Now referring to Figure 15, a 1 x 3 array of solar harvesters 1500 is shown. The solar harvesters 1500 are similar in construction to the solar harvesters 900 shown in Figures 9, 10 and 11, and operate according to the same principles. Each solar harvester 1500 comprises a Cassegrain solar collector 1530 formed from a single-piece monolithic borosilicate glass housing 1532 of unitary construction, hermetically sealed to a cylindrical borosilicate glass plug 1526. The plug 1526 cooperates with the housing 1530 to define an interior volume which is either evacuated or filled with an inert gas and therefore provides an inert

environment.

[0068] The housing 1532 comprises a primary reflector 1502 having a central aperture 1506 defined therethrough, a secondary reflector 1504 in registration with the central aperture 1506, and an optically transparent cover member 1512, each of which is defined by the shape of the monolithic housing 1532, with the reflective surfaces of the primary and secondary reflectors 1502, 1504 formed by a coating of silver deposited on the appropriate interior surface portions of the housing 1532. Similarly to the solar concentrator 900 described above, the housing 1532 supports four recapturing reflectors 1510, which extend through the central aperture 1506.

[0069] A solar conversion cell 1410, a bypass diode 1424, the second end 1306 of the hollow member 1302 of a first cooling element 300 (including the crossbar 1314 and electrical contact members 1308), and the block 1316 (including the generally planar surface 1310) and the first end 1304 of the hollow member 1302 of a second cooling element 1300, are all encapsulated and hermetically sealed inside the plug 1526. The hollow member 302 of the first cooling element 1300 extends into the plug 1526 and is hermetically sealed therewith, and the hollow member 1302 of the second cooling element 1300 extends outwardly from the block 1316 and out of the plug 1526 and is hermetically sealed therewith. [0070] Analogously to the solar harvester 900, in each solar harvester 1500, incoming solar radiation is directed by the Cassegrain optics onto the solar conversion cell 1410, and the current generated by the solar conversion cell 1410 will travel along the electrical pathway defined by the conductive coatings 1322, and thermal transfer fluid flowing through the hollow members 302 will carry heat away from the solar conversion cell 1410.

[0071] The portion of the hollow member 1302 extending between adjacent plugs 1526 in the array is encapsulated in a vacuum defined by an annular housing surrounding that portion of the hollow member 1302. In the illustrated embodiment, vacuum isolation tubes 1540 are formed by assembling tube halves around the relevant portion of each hollow member 1302, flame welding the halves together and evacuating the isolation tubes 1540 so formed. The evacuated volume 1542 between the outer surface of the hollow member 302 and the inner surface of the vacuum isolation tube 1540 provides thermal insulation to facilitate processing or storage of the heat collected from the solar conversion cells 1410. Optionally, the vacuum isolation tubes may be omitted.

[0072] Figure 17 shows at 1702 a physical schematic representation of the electrical pathways 1704 defined by the conductive coatings described above when coupled to solar conversion cells 1706 and bypass diodes 1708, alongside a corresponding representative electrical schematic 1710.

[0073] In the illustrated embodiments, the housings 832, 932, 1532 for the solar collectors 830, 930, 1530, the plugs 626, 1526, the recapturing reflectors 810, 910, 1510 and support members therefor, the main bodies 308, 308A of the heat pipes 302, 302A, the extension members 402, 402A, the hollow member 1302, the crossbars 410, 41 OA, 1314 and electrical contact members 408, 408A, 1308, are all formed from the same material, namely borosilicate glass. Similarly, the blocks 316, 316 A, 1316 and the thermal transfer element 324 and air cooling element 324 A are made from a suitable metal such as Kovar, or also from borosilicate glass where the thermal and electrical transfer assemblies 400, 400A or cooling element are of unitary, single-piece borosilicate glass construction. As such, solar harvesters assembled from these components will have a dimensionally stable structure since the various components will have an identical or compatible coefficient of thermal expansion, and can be assembled using flame-welding techniques.

[0074] Several currently preferred embodiments have been described by way of example. It will be apparent to persons skilled in the art that a number of variations and modifications can be made without departing from the scope of the invention as defined in the claims.

[0075] The above description is intended in an illustrative rather than a restrictive sense. Variations to the exact embodiments described may be apparent to those skilled in the relevant art without departing from the spirit and scope of the claims set out below. It is intended that any such variations be deemed within the scope of this patent.

Claims

WHAT IS CLAIMED IS:

1. A cooling element for a solar conversion cell, comprising: a heat pipe having an evaporation end which receives heat and a condensation end which releases heat; wherein the evaporation end of the heat pipe includes a generally planar surface for receiving an underside of the solar conversion cell.

2. The cooling element of claim 1, wherein: at least a portion of the generally planar surface is electrically conductive; a heat pipe electrical pathway is defined along the heat pipe, exteriorly of an interior volume of the heat pipe; and the electrically conductive portion of the generally planar surface is in electrical

communication with the heat pipe electrical pathway.

3. A cooling and electrical transfer assembly, comprising: a cooling element according to claim 2; an extension member supported by the heat pipe and having a first end adjacent the condensation end of the heat pipe and a second end remote from the condensation end of the heat pipe; spaced apart electrical contacts extending from the second end of the extension member; wherein: an extension member electrical pathway is defined along the extension member; the extension member electrical pathway is in electrical communication with the heat pipe electrical pathway; and the electrical contacts are in electrical communication with the extension member electrical pathway.

4. A cooling and electrical transfer system for a plurality of solar conversion cells, comprising: a plurality of cooling and electrical transfer assemblies according to claim 3; the cooling and electrical transfer assemblies assembled end to end; wherein, for at least one pair of cooling and electrical transfer assemblies: the generally planar surface at the evaporation end of the heat pipe of one of the cooling elements is disposed between the spaced apart electrical contacts of the other one of the cooling elements; and there exists a gap in electrical communication between the generally planar surface at the evaporation end of the heat pipe of the one of the cooling elements and the spaced apart electrical contacts of the other one of the cooling elements.

5. A solar harvester assembly, comprising: a cooling and electrical transfer system according to claim 4; at least two solar conversion cells; wherein, for at least one of the solar conversion cells: a bottom surface of the solar conversion cell is supported by the generally planar surface of the evaporation end of the heat pipe of the one of the cooling and electrical transfer assemblies in electrical and thermal communication therewith; an upper surface of the solar conversion cell is in electrical communication with the spaced apart electrical contacts of the other one of the cooling and electrical transfer assemblies; and the gap in electrical communication between the generally planar surface at the evaporation end of the heat pipe of the one of the cooling and electrical transfer assemblies and the spaced apart electrical contacts of the other one of the cooling and electrical transfer assemblies is bridged by the solar conversion cell.

6. The solar harvester assembly of claim 5, wherein the gap in electrical communication between the generally planar surface of the evaporation end of the heat pipe of the one of the cooling and electrical transfer assemblies and the spaced apart electrical contacts of the other one of the cooling and electrical transfer assemblies is further bridged by a bypass diode connected in parallel with the solar conversion cell.

7. The solar harvester assembly of claim 5, wherein each solar conversion cell is hermetically sealed inside an inert interior volume partially defined by a housing which forms a Cassegrain solar concentrator.

8. The solar harvester assembly of claim 7, wherein each housing which forms each respective Cassegrain solar concentrator is a unitary, monolithic housing.

9. The solar harvester assembly of claim 8, wherein for each solar conversion cell: a plug is hermetically sealed to the housing so as to cooperate with the housing to define the interior volume; the generally planar surface of the evaporation end of the heat pipe of the one cooling and electrical transfer assembly is disposed inside the plug; the heat pipe extends outwardly from the generally planar surface of the evaporation end thereof through the plug and is hermetically sealed therewith; at least one of the extension member and the spaced apart electrical contacts of the other cooling and electrical transfer assemblies extends into the plug and is hermetically sealed therewith.

10. The cooling and electrical transfer system of claim 4, wherein the electrically conductive portion of the generally planar surface, the heat pipe electrical pathway and the extension member electrical pathway are defined by electrically conductive surface coatings on the generally planar surface, the heat pipe and the extension member, respectively.

1 1. A cooling element for a solar conversion cell, comprising: an elongate hollow member having a first end and a second end and defining a fluid passageway therethrough; wherein the first end of the hollow member supports and is in thermal communication with a generally planar surface for receiving an underside of the solar conversion cell.

12. The cooling element of claim 1 1, wherein: at least a portion of the generally planar surface is electrically conductive; an electrical pathway is defined along the hollow member, exteriorly of an interior volume of the hollow member; and the electrically conductive portion of the generally planar surface is in electrical

communication with the electrical pathway.

13. The cooling element of claim 12, further comprising: spaced apart electrical contacts extending from the second end of the hollow member; wherein: the electrical contacts are in electrical communication with the electrical pathway.

14. A cooling and electrical transfer system for a plurality of solar conversion cells, comprising: a plurality of cooling elements according to claim 13; the cooling elements assembled end to end; wherein, for at least one pair of cooling elements: the generally planar surface at the first end of the hollow member of one of the cooling elements is disposed between the spaced apart electrical contacts of the other one of the cooling elements; and there exists a gap in electrical communication between the generally planar surface at the first end of the hollow member of the one of the cooling elements and the spaced apart electrical contacts of the other one of the cooling elements.

15. A solar harvester assembly, comprising: a cooling and electrical transfer system according to claim 14; at least two solar conversion cells; wherein, for at least one of the solar conversion cells: a bottom surface of the solar conversion cell is supported by the generally planar surface at the first end of the hollow member of the one of the cooling elements in electrical and thermal communication therewith; an upper surface of the solar conversion cell is in electrical communication with the spaced apart electrical contacts of the other one of the cooling elements; and the gap in electrical communication between the generally planar surface at the first end of the hollow member of the one of the cooling elements and the spaced apart electrical contacts of the other one of the cooling elements is bridged by the solar conversion cell.

16. The solar harvester assembly of claim 15, wherein the gap in electrical communication between the generally planar surface at the first end of the hollow member of the one of the cooling elements and the spaced apart electrical contacts of the other one of the cooling elements is further bridged by a bypass diode connected in parallel with the solar conversion cell.

17. The solar harvester assembly of claim 15, wherein each solar conversion cell is hermetically sealed inside an inert interior volume partially defined by a housing which forms a Cassegrain solar concentrator.

18. The solar harvester assembly of claim 17, wherein each housing which forms each respective Cassegrain solar concentrator is a unitary, monolithic housing.

19. The solar harvester assembly of claim 8, wherein for each solar conversion cell: a plug is hermetically sealed to the housing so as to cooperate with the housing to define the interior volume; the generally planar surface at the first end of the hollow member of the one cooling element is disposed inside the plug; the hollow member extends outwardly from the generally planar surface at the first end thereof through the plug and is hermetically sealed therewith; at least one of the hollow member and the spaced apart electrical contacts of the other cooling element extends into the plug and is hermetically sealed therewith.

21. The solar harvester assembly of claim 19, wherein a portion of the hollow member extending between adjacent plugs is encapsulated in a vacuum defined by an annular housing surrounding the portion of the hollow member.

22. The cooling and electrical transfer system of claim 14, wherein the electrically conductive portion of the generally planar surface and the electrical pathway are defined by electrically conductive surface coatings on the generally planar surface and the hollow member, respectively.