Generating electric power from solar radiation

• US 5,125,983 A
• Filed: 04/22/1991
• Issued: 06/30/1992
• Est. Priority Date: 04/22/1991
• Status: Expired due to Term

• Current Assignee: Electric Power Research Institute Incorporated
• Original Assignee: Electric Power Research Institute Incorporated
• Inventors: Cummings, Richard D.
• Primary Examiner(s): Weisstuch, Aaron
• Application Number:
  US07/690,194
• Time in Patent Office: 435 Days
• Field of Search: 136/246, 136/251, 136/259, 437/2, 437/205, 437/209, 228/58, 228/179, 228/180.1, 228/180.2
• US Class Current: 136/246
• CPC Class Codes: F24S 23/30 with lenses
• CPC Class Codes: F24S 25/10 extending in directions away from a supporting surface
• CPC Class Codes: F24S 30/422 Vertical axis
• CPC Class Codes: F24S 30/425 Horizontal axis
• CPC Class Codes: H01L 31/048 Encapsulation of modules
• CPC Class Codes: H01L 31/0543 comprising light concentrating means of the refractive type, e.g. lenses
• CPC Class Codes: H01L 31/0547 comprising light concentrating means of the reflecting type, e.g. parabolic mirrors, concentrators using total internal reflection
• CPC Class Codes: H02S 20/30 Supporting structures being movable or adjustable, e.g. for angle adjustment
• CPC Class Codes: H02S 40/22 Light-reflecting or light-concentrating means directly associated with the PV cell or integrated with the PV cell H01L31/054
• CPC Class Codes: Y02E 10/47 Mountings or tracking
• CPC Class Codes: Y02E 10/52 PV systems with concentrators

Abstract

An extensive photovoltaic array for generating electric power from solar radiation as in a power plant includes an extensive unitary structural grid having substantial extent in both x and y directions and supported on a pedestal. The unitary structural grid is defined by a multiplicity of structural members connected to one another at angles and defining spaces therebetween. The structural grid has a depth sufficient to provide structural rigidity to the photovoltaic array. A large multiplicity of lens assemblies, each including at least one lens, is directly supported by and in spaces defined between structural members of the unitary structural grid. The lens assemblies close the upper side of the unitary structural grid. All other sides of the unitary structural grid are also closed. A plurality of solar cells are located within spaces defined between structural members of the structural grid and positioned to receive solar radiation that passes through respective lenses of the lens assemblies. The lens assemblies and the structural members of the structural grid have an integrated relationship.

Claims

1. An extensive photovoltaic array for generating electric power from solar radiation as in a power plant, comprising

an extensive unitary structural grid having substantial extent in both x and y directions and supported on a pedestal, said unitary structural grid being directly attached to said pedestal, said unitary structural grid being defined by a multiplicity of structural members connected to one another at angles and defining spaces therebetween, said structural grid having a depth sufficient to provide structural rigidity to said photovoltaic array,

a large multiplicity of lens assemblies, each comprised of at least one lens, directly supported by structural members of said unitary structural grid, said lens assemblies closing the upper side of said unitary structural grid,

all other sides of said unitary structural grid being closed by a plurality of enclosure plates directly supported by structural members of said unitary structural grid in a manner such that at least a portion of said unitary structural grid is enclosed within a space defined by said plates and said lens assemblies, and

a plurality of solar cells located within said space in which at least a portion of said unitary structural grid is enclosed and positioned to receive solar radiation that passes through respective lenses of said lens assemblies,

whereby said lens assemblies, said structural members of said structural grid, said solar cells, and said enclosure plates have an integrated relationship.

2. A photovoltaic array in accordance with claim 1, wherein the lower side of said unitary structural grid is closed by a large multiplicity of circuit board plates on which said plurality of solar cells are mounted and to which said plurality of solar cells are electrically connected, said circuit board plates being directly supported by and in spaces defined between structural members of said unitary structural grid.

3. A photovoltaic array in accordance with claim 2, wherein each of said circuit board plates comprises a planar electrically insulative layer, an upper electrically and thermally conductive layer supported by and in heat-transferring relationship to said electrically insulative layer, and a thermally conductive heat sink member extending under said electrically insulative member in heat transferring relationship therewith.

4. A photovoltaic array in accordance with claim 3, wherein said electrically insulative layer comprises a sheet-form member of fiberglass and epoxy.

5. A photovoltaic array in accordance with claim 4, wherein said electrically insulative layer has a thickness on the order of 3 thousandths of an inch, and a dielectric strength on the order of 4000 volts.

6. A photovoltaic array in accordance with claim 3, wherein a material comprising said heat sink member is anodized to form an anodized electrically insulative film forming said electrically insulative layer.

7. A photovoltaic array in accordance with claim 6, wherein said electrically insulative layer has a dielectric strength on the order of 800 volts.

8. A photovoltaic array in accordance with claim 3, wherein said upper electrically and thermally conductive layer of each of said circuit board plates has at least one interruption that electrically isolates a portion of said upper electrically and thermally conductive layer near edges of said circuit board plate from other portions of said upper electrically and thermally conductive layer.

9. A photovoltaic array in accordance with claim 3, wherein

said upper electrically conductive layer of each of said circuit board plates is interrupted so that adjacent portions thereof are electrically isolated and also serve as positive and negative conductors, and

at least one solar cell spans across a region of interruption in said upper electrically conductive layer and is secured in electrical and heat conductive relationship to positive and negative portions of said conductive layer.

10. A photovoltaic array in accordance with claim 3, wherein each of said circuit board plates has at least one of said plurality of solar cells electrically connected to said upper electrically and thermally conductive layer by means of at least one solder connection.

11. A photovoltaic array in accordance with claim 3, wherein

each of said circuit board plates has a plurality of said solar cells electrically connected to said upper electrically and thermally conductive layer, and

each of said solar cells is connected directly to a pair of circuit nodes between which at least one other of said solar cells is directly connected in parallel fashion,

said solar cells being arranged in a plurality of sets of parallelly connected solar cells, said sets of parallelly connected solar cells being connected in series,

whereby current passing through any solar cell in one of said plurality of sets can pass through any solar cell in an adjacent one of said plurality of sets.

12. A photovoltaic array in accordance with claim 2, wherein said multiplicity of circuit board plates are interconnected by electrical conductors located entirely within said closed photovoltaic array, said electrical conductors electrically interconnecting said plurality of solar cells that are electrically connected to said multiplicity of circuit board plates.

13. A photovoltaic array in accordance with claim 1, further comprising a plurality of removable shims positioned at locations on said structural grid to compensate for structural variations in said structural grid to enhance the degree of flatness of the upper side of said photovoltaic array comprising said lens assemblies and the degree of flatness of the lower side of said photovoltaic array.

14. A photovoltaic array in accordance with claim 1, wherein

said pedestal comprises a vertical post,

said lens assemblies are disposed uniformly across said upper side of said structural grid except at a position at which said vertical post is located, and

said solar cells are disposed uniformly throughout said photovoltaic array except at a location at which said vertical post is located.

15. A photovoltaic array in accordance with claim 1, further comprising a plurality of gutters at the upper side of said array located beneath gaps between said lens assemblies and arranged to capture water that passes into said gaps and to channel said water off of said photovoltaic array, thereby preventing captured water from entering said photovoltaic array.

16. A photovoltaic array in accordance with claim 1, further comprising a plurality of water shield plates at the upper side of said array, each of said water shield plates comprising a first section located beneath an edge margin of a first of said lens assemblies, a second section located above an edge margin of a second of said lens assemblies, and a vertical water-interception surface extending between said first and second sections, constructed to intercept water and to prevent such water from entering beneath said second of said lens assemblies.

17. A photovoltaic array in accordance with claim 1, wherein means closing at least one side of said unitary structural grid has at least one weep hole sized and located to permit water inside said photovoltaic array to escape from said photovoltaic array.

18. A photovoltaic array in accordance with claim 1, wherein said structural grid provides physical support for each of said lens assemblies at edge regions of said lens assemblies and said array includes means to support a center region of each of said lens assemblies.

19. A photovoltaic array in accordance with claim 1, wherein the distance between said lens assemblies and said solar cells is established by said depth of said structural grid.

20. A photovoltaic array in accordance with claim 19, wherein said distance between said lens assemblies and said solar cells is sized to cause each lens to focus said solar radiation so that all focal points are located at or below a plane, parallel to said lens, that passes through the respective solar cell.

21. A photovoltaic array in accordance with claim 20, wherein

all of said focal points are located below said plane, and

said solar radiation passing through said lens forms a pattern on said solar cell that has dimensions substantially equal to the dimensions of an active area of said solar cell.

22. A photovoltaic array in accordance with claim 20, wherein said solar cells and said lenses have relative dimensions such that a ratio of concentration of said solar radiation incident on said solar cells relative to concentration of said solar radiation before passing through said lenses is between approximately 150 and 250.

23. A device for generating electric power from solar radiation, comprising

a circuit board plate comprised of a planar electrically insulative layer, an upper electrically and thermally conductive layer supported by and in heat-transferring relationship to said electrically insulative layer, and a thermally conductive heat sink member extending under said electrically insulative member in heat transferring relationship therewith, said upper electrically conductive layer being interrupted so that adjacent portions thereof are electrically isolated and also serve as positive and negative conductors, and

a solar cell spanning across a region of interruption in said upper electrically conductive layer and secured in electrical and heat conductive relationship to positive and negative portions of said conductive layer,

said circuit board plate comprising a structural element of a housing that defines a space within which said solar cell is located, said upper electrically and thermally conductive layer forming an inner surface of said housing and being exposed to said space within said housing, said thermally conductive heat sink member forming an outer surface of said housing.

24. A device in accordance with claim 23, wherein said electrically insulative layer comprises a sheet-form member of fiberglass and epoxy.

25. A device in accordance with claim 24, wherein said electrically insulative layer has a thickness on the order of 3 thousandths of an inch, a dielectric strength on the order of 4000 volts.

26. A device in accordance with claim 23, wherein a material comprising said heat sink member is anodized to form an anodized electrically insulative film forming said electrically insulative layer.

27. A device in accordance with claim 26, wherein said electrically insulative layer has a dielectric strength on the order of 800 volts.

28. A device in accordance with claim 23, wherein said upper electrically and thermally conductive layer of said circuit board plate has at least one interruption that electrically isolates a portion of said upper electrically and thermally conductive layer near edges of said circuit board plate from other portions of said upper electrically and thermally conductive layer.

29. A device in accordance with claim 28, wherein said circuit board plate has at least one weep hole sized to permit water to pass therethrough, said weep hole being located in a portion of said circuit board plate that is near an edge of said circuit board plate and that is outside said interruption on said upper electrically and thermally conductive layer.

30. A device in accordance with claim 23, wherein said solar cell is electrically connected to said upper electrically and thermally conductive layer by means of at least one solder connection.

31. A device in accordance with claim 23, wherein

said device comprises a plurality of solar cells located on said circuit board plate and electrically connected to said upper electrically and thermally conductive layer, and

each of said solar cells is connected directly to a pair of circuit nodes between which at least one other of said solar cells is directly connected in parallel fashion,

said solar cells being arranged in a plurality of sets of parallelly connected solar cells, said sets of parallelly connected solar cells being connected in series,

whereby current passing through any solar cell in one of said plurality of sets can pass through any solar cell in an adjacent one of said plurality of sets.

32. An extensive photovoltaic array for generating electric power from solar radiation as in a power plant, comprising

a large multiplicity of co-planar lens assemblies, said lens assemblies closing an upper side of said photovoltaic array, each of said lens assemblies comprising at least one lens,

a plurality of solar cells located below said lens assemblies, each of said solar cells being positioned to receive solar radiation that passes through a lens in one of said plurality of lens assemblies,

a plurality of horizontally extending water shield plates associated with corresponding horizontal edges of said lens assemblies, each of said water shield plates comprising a first section located beneath an edge margin of a first of said lens assemblies, a second section located above an edge margin of a second of said lens assemblies, said first of said lens assemblies being positioned higher than said second of said lens assemblies, and an upright water-interception surface extending between said first and second sections in a direction substantially perpendicular to the plane defined by the upper side of the array, constructed to intercept water and to prevent such water from entering beneath said second of said lens assemblies,

a plurality of inclined gutters associated with corresponding inclined lens assembly edges located beneath gaps between adjacent co-planar lens assemblies and arranged to capture water intercepted and horizontally diverted by said upright water-interception surface of said water shield plates and to channel captured water off of said photovoltaic array, thereby preventing captured water from entering said photovoltaic array.

33. A photovoltaic array in accordance with claim 32, wherein said enclosure further comprises a plurality of trim battens located above said gaps between said co-planar lens assemblies and located above said water shield plates, and further comprises a plurality of gaskets located between said trim battens and portions of said lens assemblies and said water shield plates that are covered by said trim battens.

34. A method of manufacturing a device for generating electric power from solar radiation, comprising the steps of

applying a soldering flux to a circuit board plate,

positioning a cell placement fixture over said circuit board plate in a first position, said circuit board plate having structures that engage said cell placement fixture to provide precise positioning of said cell placement fixture on said circuit board plate,

placing a first soldering foil on a first region of said circuit board plate that is unobstructed by said cell placement fixture, said cell placement fixture having sides that engage said first soldering foil during placement of said first soldering foil on said first region of said circuit board plate,

melting said first soldering foil,

applying a soldering flux to a first solar cell,

placing said first solar cell over melted solder resulting from melting of said first soldering foil, said cell placement fixture having sides that engage said first solar cell during placement of said first solar cell on said first region of said circuit board plate,

permitting said melted solder to cool, to provide at least one solder connection between said first solar cell and said circuit board plate,

removing said cell placement fixture from said first position on said circuit board plate,

positioning a cell placement fixture over said circuit board plate in a second position, said circuit board plate having structures that engage said cell placement fixture to provide precise positioning of said cell placement fixture on said circuit board plate,

placing a second soldering foil on a second region of said circuit board plate that is unobstructed by said cell placement fixture, said cell placement fixture having sides that engage said second soldering foil during placement of said second soldering foil on said second region of said circuit board plate,

melting said second soldering foil,

applying a soldering flux to a second solar cell,

placing said second solar cell over melted solder resulting from melting of said second soldering foil, said cell placement fixture having sides that engage said second solar cell during placement of said second solar cell on said second region of said circuit board plate,

permitting said melted solder to cool, to provide at least one solder connection between said second solar cell and said circuit board plate, and

removing said cell placement fixture from said second position on said circuit board plate.

35. A method in accordance with claim 34, wherein said soldering foil provides a plurality of solder connections between said solar cell and said circuit board plate.

36. A method in accordance with claim 34, further comprising the steps of

placing soldering foils on a plurality of other regions of said circuit board plate that are unobstructed by said cell placement fixture,

melting said soldering foils,

placing a plurality of tabs over melted solder resulting from melting of said soldering foils on said plurality of other regions of said circuit board plate, said placement fixture providing a physical guide for placement of said soldering foils and said plurality of tabs onto said plurality of other regions of said circuit board plate, and

permitting said melted solder to cool, to provide solder connections between said plurality of tabs and said circuit board plate.

37. A method in accordance with claim 36, further comprising the steps of

placing a secondary optical element over said solar cell, and

folding said tabs over portions of said secondary optical element to secure said secondary optical element in position over said solar cell.

38. A method in accordance with claim 34, wherein

said circuit board plate comprises a plurality of depressions,

said cell placement fixture comprises a plurality of legs,

and said step of positioning said cell placement fixture over said circuit board plate comprises inserting said plurality of legs into said plurality of depressions.

39. A method in accordance with claim 34, further comprising the steps of

positioning a plurality of cell placement fixtures over said circuit board plate, said circuit board plate having structures that engage said plurality of cell placement fixtures to provide precise positioning of said plurality of cell placement fixtures on said circuit board plate,

placing a plurality of soldering foils on a plurality of regions of said circuit board plate that are unobstructed by a plurality of cell placement fixtures, said cell placement fixtures having sides that engage said soldering foil during placement of said soldering foil on said plurality of regions of said circuit board plate,

simultaneously melting said soldering foils,

applying soldering flux to a plurality of solar cells,

placing said plurality of solar cells over melted solder resulting from melting of said soldering foils, said cell placement fixtures having sides that engage said solar cells during placement of said solar cells on said plurality of regions of said circuit board plate,

simultaneously cooling said solder connections, to provide at least one solder connection between each of said solar cells and said circuit board plate, and

removing said plurality of cell placement fixtures from said circuit board plate.

40. A method of manufacturing a device for generating electric power from solar radiation, comprising the steps of

placing a soldering foil on a circuit board plate, said circuit board plate being comprised of a planar electrically insulative layer, an upper electrically and thermally conductive layer supported by and in heat-transferring relationship to said electrically insulative layer, and a thermally conductive heat sink member extending under said electrically insulative member in heat transferring relationship therewith, said upper electrically conductive layer being interrupted so that adjacent portions thereof are electrically isolated and also serve as positive and negative conductors, said soldering foil spanning across a region of interruption in said upper electrically conductive layer,

melting said soldering foil,

placing said solar cell over melted solder resulting from melting of said soldering foil,

permitting said melted solder to cool, to secure said solar cell in electrical and heat conductive relationship to positive and negative portions of said conductive layer, and

forming a housing that defines a space within which said solar cell is located, said circuit board plate comprising a structural element of said housing, said upper electrically and thermally conductive layer forming an inner surface of said housing and being exposed to said space within said housing, said thermally conductive heat sink member forming an outer surface of said housing.

41. A method in accordance with claim 40, further comprising the step of forming an interruption on said upper electrically and thermally conductive layer of said circuit board plate that isolates a portion of said upper electrically and thermally conductive layer near edges of said circuit board plate from other portions of said upper electrically and thermally conductive layer.

42. A method in accordance with claim 41, further comprising the step of forming at least one weep hole in said circuit board plate sized and located to permit which water to pass therethrough, said weep hole being located in a portion of said circuit board plate that is near an edge of said circuit board plate and that is outside said interruption on said upper electrically and thermally conductive layer.

43. A method in accordance with claim 40, further comprising the steps of

placing a plurality of soldering foils on said circuit board plate,

melting said plurality of soldering foils,

placing a plurality of solar cells over melted solder resulting from melting of said plurality of soldering foils, and

permitting said melted solder to cool, to connect each of said solar cells directly to a pair of circuit nodes on said circuit board plate between which at least one other of said solar cells is directly connected in parallel fashion,

said solar cells being arranged in a plurality of sets of parallelly connected solar cells, said sets of parallelly connected solar cells being connected in series,

whereby current passing through any solar cell in one of said plurality of sets can pass through any solar cell in an adjacent one of said plurality of sets.