ILLUMINATION AGNOSTIC SOLAR PANEL

• US 20100282293A1
• Filed: 06/15/2010
• Published: 11/11/2010
• Est. Priority Date: 01/21/2009
• Status: Active Grant

• Current Assignee: Spectrum Solar, LLC
• Original Assignee: Tenksolar, Inc.
• Inventors: Knight, Raymond W., Berg, Lowell J., Novotny, John P., Meyer, Forrest C., Meyer, Dallas W., Wheeler, Steven E.
• Granted Patent: US 8,563,847 B2
• Time in Patent Office: Days
• US Class Current: 136/244
• CPC Class Codes: H01L 31/02008 for solar cells or solar cell modules
• CPC Class Codes: H01L 31/02021 for solar cells electrical connection means, e.g. junction boxes, specially adapted for structural association with photovoltaic modules H02S40/34
• CPC Class Codes: H01L 31/048 Encapsulation of modules
• CPC Class Codes: H01L 31/049 Protective back sheets
• CPC Class Codes: H01L 31/0504 specially adapted for series or parallel connection of solar cells in a module
• CPC Class Codes: H02J 2300/26 involving maximum power point tracking control for photovoltaic sources maximum power point systems in particular G05F1/67
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 3/46 Controlling of the sharing of output between the generators, converters, or transformers
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: H02M 7/003 Constructional details, e.g. physical layout, assembly, wiring or busbar connections
• CPC Class Codes: H02S 30/10 Frame structures
• CPC Class Codes: H02S 40/32 comprising DC/AC inverter means associated with the PV module itself, e.g. AC modules
• CPC Class Codes: H02S 40/34 comprising specially adapted electrical connection means to be structurally associated with the PV module, e.g. junction boxes
• CPC Class Codes: H02S 40/38 Energy storage means, e.g. batteries, structurally associated with PV modules
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y02E 70/30 Systems combining energy storage with energy generation of non-fossil origin

Abstract

In one example, a photovoltaic module includes a plurality of discrete photovoltaic cells arranged in a plurality of cell rows, and a substantially electrically conductive and continuous area backsheet. The photovoltaic cells in each cell row are electrically connected in parallel to each other. The cell rows are electrically connected in series to each other and include a first row and a last row. The backsheet forms a current return path between the first and last rows. The photovoltaic cells are configured such that, in operation, current flows substantially uni-directionally through the plurality of photovoltaic cells between the first row and the last row.

Claims

1. A photovoltaic module comprising:

a plurality of discrete photovoltaic cells arranged in a plurality of cell rows, wherein;

the plurality of photovoltaic cells in each cell row are electrically connected in parallel to each other;

the plurality of cell rows are electrically connected in series to each other; and

the plurality of cell rows include a first row and a last row; and

a substantially electrically conductive and continuous area backsheet forming a current return path between the first and last rows;

wherein the plurality of photovoltaic cells are configured such that, in operation, current flows substantially uni-directionally through the plurality of photovoltaic cells between the first row and the last row.

2. The photovoltaic module of claim 1, wherein a thickness of the backsheet is in a range of 0.02 to 0.2 millimeters and a tensile yield strength of the backsheet is greater than or equal to 30 mega-pascals.

3. The photovoltaic module of claim 2, wherein the backsheet comprises aluminum of grade 1145-H19 or 1235-H19 and the tensile yield strength of the backsheet is in a range of 120-200 mega-pascals.

4. The photovoltaic module of claim 1, further comprising a plurality of electrically conductive strips, including at least one strip per cell row, wherein each strip is connected to a back side of each photovoltaic cell in a corresponding cell row.

5. The photovoltaic module of claim 4, wherein a thickness of each strip is in a range of 0.02 to 0.2 millimeters, a width of each strip is in a range of 0.05 to 2 centimeters, and a length of each strip is approximately equal to a length of a corresponding cell row to which the strip is connected.

6. The photovoltaic module of claim 4, wherein the plurality of electrically conductive strips are disposed between the back sides of the plurality of photovoltaic cells and the backsheet.

7. The photovoltaic module of claim 1, wherein the backsheet includes an end near the last row of photovoltaic cells, the end of the backsheet including a hole pattern and fold formed along the width of the backsheet, the photovoltaic module further comprising:

an interconnecting member substantially extending the length of the last row and having a first side and a second side, the first side of the interconnecting member being electrically connected to each of the photovoltaic cells within the last row;

a solder strip disposed on a back side of the backsheet in a region of the backsheet including the hole pattern, the solder strip being soldered to the second side of the interconnecting member through the hole pattern such that each of the photovoltaic cells within the last row is electrically connected to the backsheet through the interconnecting member and the solder strip, the fold of the end of the backsheet covering the solder strip;

a sealant laminated between the solder strip and the fold; and

a protective film substantially covering the backsheet, the protective film having an emissivity greater than 0.6.

8. The photovoltaic module of claim 7, wherein the sealant comprises butyl rubber or solar edge tape.

9. The photovoltaic module of claim 7, wherein the protective film covering the backsheet comprises black polyethylene terephthalate (“

PET”

) or black poly methyl methacrylate (“

PMMA”

).

10. The photovoltaic module of claim 7, wherein the protective film is substantially electrically insulating.

11. The photovoltaic module of claim 1, further comprising an electronics assembly attached to the photovoltaic module and including a plurality of power conversion circuits.

12. The photovoltaic module of claim 11, wherein:

an end of the photovoltaic module near the first or last row of photovoltaic cells to which the electronics assembly is connected is a positive end of the photovoltaic module when the power conversion circuits comprise p-type field effect transistors;

or

an end of the photovoltaic module near the first or last row of photovoltaic cells to which the electronics assembly is connected is a negative end of the photovoltaic module when the power conversion circuits comprise n-type field effect transistors.

13. The photovoltaic module of claim 11, wherein:

the backsheet includes an end near the first row of photovoltaic cells, the end of the backsheet including a fold substantially extending the width of the backsheet, the fold being oriented substantially orthogonal to a major surface of the backsheet; and

the electronics assembly comprises;

a housing extending along at least a portion of the end of the backsheet, the housing having a first side disposed proximate and substantially parallel to the fold of the backsheet;

an electrical isolation layer disposed between the housing and the fold of the backsheet; and

a first interconnecting member extending along at least a portion of the end of the backsheet, wherein the electrical isolation layer and the fold of the backsheet are sandwiched between the first side of the housing and the first interconnecting member.

14. The photovoltaic module of claim 13, further comprising a strain relief fold formed in the backsheet between the fold of the backsheet and the major surface of the backsheet.

15. The photovoltaic module of claim 13, wherein the electrical isolation layer comprises thermally conductive tape.

16. The photovoltaic module of claim 13, wherein:

the electronics assembly further comprises a printed circuit board assembly including a printed circuit board having disposed thereon the plurality of power conversion circuits;

the printed circuit board assembly is mechanically and electrically connected to the first interconnecting member; and

the printed circuit board assembly is grounded to the backsheet through the first interconnecting member and the fold of the backsheet.

17. The photovoltaic module of claim 16, further comprising a second interconnecting member generally extending lengthwise along at least a portion of the end of the backsheet and having a first side and a second side, wherein:

the first side of the second interconnecting member is electrically connected to each of the photovoltaic cells within the first row;

the second side of the second interconnecting member includes a strain relief fold; and

the second side of the second interconnecting member is electrically and mechanically connected to the printed circuit board assembly of the electronics assembly.

18. The photovoltaic module of claim 16, wherein the electronics assembly is attached on a backside of the photovoltaic module, the photovoltaic module further comprising a light emitting diode connected to the printed circuit board and viewable from a front of the photovoltaic module.

19. The photovoltaic module of claim 18, wherein the printed circuit board assembly is configured to optically communicate data regarding the photovoltaic module via the light emitting diode, the data including at least one of out-of-range voltage, ground fault detection, module faults, insufficient illumination, power, system voltage, panel voltage, output current, or photovoltaic module temperature.

20. The photovoltaic module of claim 13, wherein the fold included in the end of the backsheet includes a purposely textured surface facing the heatsink.

21. The photovoltaic module of claim 13, wherein the fold included in the end of the backsheet comprises a first fold, the end of the backsheet further comprising a strain relief fold formed between the major surface of the backsheet and the first fold.

22. The photovoltaic module of claim 13, wherein the housing includes a second side attached to the first side of the housing, the second side being disposed proximate and substantially parallel to the major surface of the backsheet, the photovoltaic module further comprising acrylic foam tape connecting the second side of the housing to the major surface of the backsheet.

23. The photovoltaic module of claim 13, further comprising a transparent front plate disposed in front of the plurality of photovoltaic cells, wherein the housing includes a removable cover and two vented end caps disposed on opposite ends of the housing and wherein a portion of the front plate, the first side of the housing, the end caps and the removable cover cooperatively form an enclosure within which the power conversion circuits are disposed.

24. The photovoltaic module of claim 13, wherein the first interconnecting member extends to near contact with heat-generating elements of the electronics assembly and is configured to transfer thermal energy away from the heat-generating elements.

25. The photovoltaic module of claim 13, further comprising:

a protective film covering a portion of the backsheet not including a perimeter portion of the backsheet along at least one side of the backsheet; and

a frame extending along at least one side of the photovoltaic module, wherein;

a cross-section of the frame includes a channel sufficiently wide to accommodate a material stack including at least the front plate, the backsheet along the perimeter portion, and a substantially electrically isolating strip disposed between a backside of the perimeter portion of the backsheet and a corresponding face of the channel; and

the cutout includes a recessed slot providing substantially electrically insulating space between an edge of the perimeter portion of the backsheet and the frame.

26. A photovoltaic module comprising:

a plurality of photovoltaic cells arranged in a plurality of cell rows, the plurality of photovoltaic cells in each cell row being connected in parallel to each other and the plurality of cell rows being connected in series to each other such that, in operation, current flows substantially uni-directionally through the plurality of photovoltaic cells, the plurality of cell rows including a first row and a last row;

a substantially electrically conductive backsheet forming a current return path between the first and last rows, the backsheet including a first end electrically connected to the first row of photovoltaic cells through an electronics assembly and a second end electrically connected to the last row of photovoltaic cells;

the electronics assembly attached to the first end of the backsheet, the electronics assembly including a plurality of power conversion circuits and a housing extending substantially parallel to the first end of the backsheet; and

two terminals, each extending in a direction substantially orthogonal to a major surface of the backsheet, each of the two connectors having a contact area of at least six square millimeters.

27. The photovoltaic module of claim 26, further comprising first, second, third and fourth edges forming a perimeter of the photovoltaic module, each edge being substantially normal to an adjoining edge, the first edge being adjoined between the second and third edges, wherein one of the connectors is located near the first edge approximately one-third of the distance from the second edge to the third edge and the other of the connectors is located near the first edge approximately two-thirds of the distance from the second edge to the third edge.

28. The photovoltaic module of claim 26, wherein each of the two terminals includes:

a bolt having a first end connected to the electronics assembly and a second end that is threaded and split in two such that the second end defines a u-shaped channel, wherein a diameter of the bolt is at least 10 millimeters;

a T-shaped washer configured to be placed updside down within the u-shaped channel; and

a nut, wherein the bolt, washer and nut cooperate to engage a portion of a wire within the u-shaped channel of the bolt and thereby electrically connect the wire to the electronics assembly via the terminal.

29. The photovoltaic module of claim 26, further comprising:

two terminal housings, each terminal housing enclosing at least the first end of a corresponding one of the terminals; and

two terminal covers configured to couple to a corresponding one of the terminal housings;

wherein each terminal is substantially covered and protected from moisture by a paired terminal housing and terminal cover.

30. The photovoltaic module of claim 29, wherein each of the two terminal covers includes one or more tabs for use with a cable tie to secure the terminal cover to a corresponding terminal housing.

31. The photovoltaic module of claim 26, further comprising a plurality of power relays coupled between negative and positive lines of the photovoltaic module and corresponding negative and positive lines of an external circuit and configured to electrically isolate the photovoltaic module from the external circuit when the photovoltaic module is not operating.

32. The photovoltaic module of claim 31, further comprising an optical relay coupled in parallel with one of the power relays between the positive line of the photovoltaic module and the positive line of the external circuit, the optical relay being configured to supply small current flow to the external circuit prior to commencing operation of the photovoltaic module to equalize line potential of the external circuit with an internal voltage of the photovoltaic module before closing the plurality of power relays.

33. The photovoltaic module of claim 26, further comprising an optical relay and a voltmeter coupled in series to each other across the negative and positive lines of the external circuit.

34. A method of commencing operation in a photovoltaic module, the method comprising:

electrically isolating a plurality of photovoltaic cells and power conversion circuits of a photovoltaic module from an external circuit including an external negative line and an external positive line respectively connected to an internal negative line and internal positive line of the photovoltaic module;

prior to commencing operation of the photovoltaic module, determining a line potential across the external negative and positive lines;

determining whether the external circuit includes a battery based on the determined line potential; and

if it is determined that the external circuit includes a battery, initializing operation of the photovoltaic module consistent with the external circuit including a battery;

or

if it is determined that the external circuit lacks a battery;

determining that the external circuit includes an inverter; and

initializing operation of the photovoltaic module consistent with the external circuit including an inverter.

35. The method of claim 34, wherein the external circuit includes a battery and an inverter or the external circuit lacks a battery and includes an inverter.

36. The method of claim 35, further comprising setting a target voltage of the photovoltaic module above a target voltage of the inverter.

37. The method of claim 34, wherein determining that the external circuit includes an inverter includes measuring a resistor-capacitor (“

RC”

) response of the external circuit.

38. The method of claim 34, wherein:

determining whether the external circuit includes a battery based on the determined line potential includes comparing the determined line potential to a minimum and maximum voltage;

it is determined that the external circuit includes a battery when the determined line potential is between the minimum and maximum voltage; and

it is determined that the external circuit lacks a battery when the determined line potential is below the minimum voltage.

39. The method of claim 34, wherein initializing operation of the photovoltaic module consistent with the external circuit including a battery includes:

charging an internal capacitance of the photovoltaic module to match the determined line potential;

closing two power relays respectively coupled between the internal and external negative lines and between the internal and external positive lines; and

outputting power to the external circuit via the external negative and positive lines.

40. The method of claim 34, wherein initializing operation of the photovoltaic module consistent with the external circuit including an inverter includes:

continuously trickling current onto the external positive line via an optical relay coupled between the internal and external positive lines;

monitoring the line potential across the external negative and positive lines while the current is continuously trickled onto the external positive line;

after the monitored line potential matches an internal voltage of the photovoltaic module, closing two power relays respectively coupled between the internal and external negative lines and between the internal and external positive lines;

discontinuing the trickle of current by closing the optical relay; and

outputting power to the external circuit via the external negative and positive lines.

41. A method of controlling power output generated by a photovoltaic module, the method comprising:

measuring module output power collectively generated by a plurality of power conversion circuits of a photovoltaic module characterized by a module power output curve having a peak;

comparing a current measured output power to a preceding measured output power; and

based on a preceding direction variable indicating a side of the peak on which the photovoltaic module was previously operating and the comparison of the current measured output power to the preceding measured output power;

determining a current direction variable indicating a side of the peak on which the photovoltaic module is currently operating; and

adjusting a switching period of the plurality of power conversion circuits.

42. The method of claim 41, further comprising operating the plurality of power conversion circuits in pairs, each power conversion circuit in a pair being operated 180 degrees out of phase with the other power conversion circuit in the pair.

43. The method of claim 41, further comprising, in response to detecting the failure of at least one of the power conversion circuits, applying full current of the photovoltaic module through the failed power conversion circuit to cause a corresponding fuse to fail.

44. The method of claim 41, wherein determining the current direction variable and adjusting the switching period based on the preceding direction variable and the comparison of the current measured output power to the preceding measured output comprises:

if the preceding direction variable is greater than zero and the current measured output power is greater than the preceding measured output power, maintaining the preceding direction variable as the current direction variable and increasing the switching period;

if the preceding direction variable is greater than zero and the current measured output power is less than the preceding measured output power, setting the current direction variable to a negative number and decreasing the switching period;

if the preceding direction variable is less than zero and the current measured output power is greater than the preceding measured output power, maintaining the preceding direction variable as the current direction variable and decreasing the switching period;

or

if the preceding direction variable is less than zero and the current measured output power is less than the preceding measured output power, setting the current direction variable to a positive number and increasing the switching period.

45. The method of claim 44, wherein each power conversion circuit includes at least one capacitor, the method further comprising:

allowing the at least one capacitor to change charge in response to the adjustment to the switching period, wherein the current measured output power becomes a new preceding measured output power and the current direction variable becomes a new preceding direction variable after allowing the at least one capacitor to change charge;

measuring the module output power collectively generated by the plurality of power conversion circuits after allowing the at least one capacitor to change charge to obtain a new current measured output power;

comparing the new current measured output power to the new preceding measured output power; and

determining a new direction variable and adjusting the switching period based on the new preceding direction variable and the comparison of the new current measured output power to the new preceding measured output power.