Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F77/00—Constructional details of devices covered by this subclass
  • H10F77/20—Electrodes
  • H10F77/206—Electrodes for devices having potential barriers
  • H10F77/211—Electrodes for devices having potential barriers for photovoltaic cells
  • H10F77/215—Geometries of grid contacts
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/50—Photovoltaic [PV] energy

Definitions

• This disclosure relates generally to solar modules used to convert solar energy into electricity and, more specifically, to solar modules having improved bus bars.
• Solar modules conventionally include a photovoltaic cell to generate electricity from light.
• the photovoltaic cell is laminated between an upper layer (e.g., made of glass or similar transparent material) and a bottom layer that is generally water resistant. Two layers of encapsulant are positioned between these outer layers, and the cells are position within the encapsulant.
• a typical photovoltaic cell is shown in Figures 1 and 2 and indicated generally at 100.
• Electrically conducting fingers 102 (only one of which is numbered) are disposed on a surface 104 of the cell 100. These fmgers 102 are electrically connected to the surface 104 of the cell 100 and conduct electricity generated by the cell.
• Two bus bars 106 are disposed on the surface 104 of the cell 100 and are electrically connected to the fmgers 102.
• a conductor 108 e.g., a metallic ribbon
• Wires (not shown) are used to electrically connect the conductors 108 and a rear contact on the opposite side of the cell 100 to an electrical device (e.g., an inverter).
• a solar module comprises a photovoltaic cell having a front surface and a rear surface.
• the photovoltaic cell is configured for converting light into electricity.
• Fingers are disposed on the front surface of the cell and are electrically connected to the cell to conduct electricity generated by the cell.
• the fingers are spaced apart from each other.
• a bus bar is disposed on the front surface of the cell and connected to at least the fingers to conduct electricity from the fingers.
• the bus bar includes segments and at least one segment has a different shape than a shape of another segment of the bus bar. The different shapes of the segments of the bus bar facilitate the transfer of heat generated during soldering of a conductor to the bus bar away from locations of the soldering.
• a solar module comprises a photovoltaic cell configured for converting light into electricity. Fingers are disposed on the cell and are electrically connected to the cell to conduct electricity generated by the cell. A bus bar is disposed on the cell and electrically connected to the fingers to conduct electricity from the fingers. The bus bar includes segments separated from each other by a gap. The gap between the segments permits thermal expansion of the bus bar. A conductor is electrically connected to the segments of the bus bar.
• a solar module comprises a
• photovoltaic cell having a front surface and a rear surface.
• the photovoltaic cell is configured for converting light into electricity.
• Fingers are disposed on the front surface of the cell and are electrically connected to the cell to conduct electricity generated by the cell.
• Insulating members are disposed on the front surface of the cell between the fingers.
• a bus bar is disposed on the front surface of the cell and is electrically connected to. the fingers to conduct electricity from the fingers. The bus bar overlies the insulating members.
• Figure 1 is a perspective view of a prior art photovoltaic cell and bus bars
• Figure 2 is a top plan view of the photovoltaic cell of Figure i ;
• Figure 3 is a top plan view of an embodiment of a photovoltaic cell and bus bars
• Figure 4 is a top plan view of bus bar segments for use with the photovoltaic cell of Figure 3;
• Figure 5 is a top plan view of another embodiment of a photovoltaic cell and bus bars.
• Figure 6 is a top plan of an enlarged portion of Figure 5;
• Figure 7 is a cross-sectional view of the photovoltaic cell of Figure 6 taken along the 7-7 line;
• Figure 8 is a top plan view of an enlarged portion of Figure 5;
• Figure 9 is a cross-sectional view of the photovoltaic cell of Figure 8 taken along the 8-8 line;
• Figure 10 is a perspective view of another embodiment of a photovoltaic cell and a bus bar.
• FIG. 3 an exemplary solar module system is shown in Figure 3 and indicated generally at 200.
• the rapid heating and cooling during soldering of components in the system is shown in Figure 3 and indicated generally at 200.
• the systems 200 described herein are generally operable to reduce the effects of thermal stress generated during soldering of a conductor (e.g., a metallic ribbon) to a bus bar of the system.
• a conductor e.g., a metallic ribbon
• the solar module 200 includes a photovoltaic cell 201 (referred to interchangeably as “the cell”) having a front surface 202 and a rear surface.
• the photovoltaic cell 201 is operable to convert the energy of light (e.g., solar energy) into electricity via the photovoltaic effect.
• Fingers 204 are disposed on the front surface 202 of the cell
• a bus bar 210 is disposed on the front surface 202 of the cell 201 and is connected to the fingers 204 to conduct electricity from the fingers. Two bus bars 210 are depicted in the embodiment of Figure 3, although other embodiments may use different numbers of bus bars.
• the bus bars 210 include discrete first segments 212 and second segments 214. At least some of the segments 212, 214 have different shapes than other segments. These segments are connected by a conductor (e.g., a metallic ribbon), which is omitted for clarity in Figure 3.
• the conductor is connected to the bus bar 210 at multiple, discrete locations by soldering. In other embodiments, the conductor is connected to the bus bar 210 along at least a majority of its length by soldering.
• These shapes of the segments 212, 214 facilitate the transfer of heat generated during soldering of the conductor to the bus bar 210 away from the locations of soldering.
• a plurality of first segments 212 and second segments 214 are provided.
• the first segments 212 have a surface area that is greater than a surface of the second segments 214.
• the first segments 212 are also shaped differently than the second segments 214.
• the conductor is soldered to the bus bar 210 at locations along the bus bar that are coincident with at least a portion of the first segments 212. In other embodiments, only some of the locations are coincident with at least a portion of the first segments 212.
• the larger surface area of the first segments 212 facilitates the transfer of heat generated during soldering of the conductor to the bus bar 210 away from the coincident locations.
• the first segments 212 function equivalently to a heat sink, and draw away and dissipate heat generated during soldering.
• Figure 4 depicts a variety of different shaped bus bar segments 216, 218, 220, 222, 224, 226, 228 which may be substituted for the rectangular-shaped first segments 212 shown in Figure 3. These segments of Figure 4 may be further altered according to other embodiments. Moreover, each segment also includes a respective location 217, 219, 221, 223, 225, 227, 229 where the conductor is soldered thereto. [0028] In prior systems lacking such segments, the heat generated during the soldering process could cause thermal stresses to develop in the photovoltaic cell 201 and/or other components of the system 200.
• thermal stresses are due in part to the different coefficients of thermal expansion (CTE) of the bus bar 210, photovoltaic cell 201, fingers 204, conductor, and solder.
• CTE coefficients of thermal expansion
• these components may expand by differing amounts if their CTEs differ.
• This differential expansion can cause cracks in the photovoltaic cell 201 which decrease its electrical output.
• the differential thermal expansion may cause delamination between the bus bars 210 and the conductors. This delamination may be especially evident in instances where the adhesion between the bus bars 210 and the front surface 202 of the photovoltaic cell 201 and/or fingers 204 is weak.
• Figures 5-9 depict another embodiment of bus bars 310 (shown in Figures 6-9) disposed on a front surface 302 of a photovoltaic cell 301 in a solar module system 300.
• the photovoltaic cell 301, conductors 303, and associated fingers 304 are of the same or similar type as those described above in relation to Figure 3.
• the bus bars 310 of Figures 5-9 are electrically connected to the fingers 304 to conduct electricity from the fingers.
• each of the bus bars 310 includes segments 312, 314 that are separated from each other by a gap 306.
• the bus bars 310 can be formed using a mesh pattern during screen printing of the segments onto the surface 302 of the photovoltaic cell 301. In other embodiments, they may be formed by plating onto a seed layer deposited in this pattern using any suitable patterning method.
• the conductor 303 is omitted for clarity.
• the gaps 306 in this embodiment have a length that is less than their width. Their width is parallel to a lateral axis XA of the cell 301, i.e., the gaps are "horizontal". Accordingly, during soldering of the bus bars 310 to the conductor 303 the segments 312 are able to expand in a direction parallel to a longitudinal axis YA of the cell 301. They are thus able to expand in this direction unimpeded by contact with other adjacent segments 312.
• the left-most bus bar 310 is shown in greater detail in Figures 8 and 9, though in Figure 8 the conductor 303 is omitted for clarity.
• the gaps 306 in this embodiment have a length that is greater than their width. Their length is parallel to the longitudinal axis YA, i.e., the gaps 306 are "vertical". Accordingly, during soldering of the bus bars 310 to the conductor 303 the segments 314 are able to expand in a direction parallel to the lateral axis XA of the cell 301. They can expand in this direction unimpeded by contact with other adjacent segments 314.
• the gaps 306 permit unimpeded thermal expansion of the segments 312, 314 of the bus bars 310 during soldering and subsequent cooling of the bus bars.
• the amount of stress imparted by the expansion and subsequent contraction of the bus bars 310 to the surface of the photovoltaic cells 301 is significantly reduced or eliminated. This reduction or elimination of thermal stress on the cell 301 surface reduces or eliminates cracking of the surface and subsequent decrease in output of the cell.
• Figure 10 depicts another embodiment of bus bars 410 disposed on a front surface 402 of a photovoltaic cell 401 in a solar module system
• the photovoltaic cell 401 is formed from silicon hetero junction cells (SHJ) where their surface 401 is a transparent conducting oxide (TCO) capable of conducting charge carriers as well as heat.
• TCOs include indium tin oxide and aluminum zinc oxide.
• Insulating members 420 are disposed on the front surface 402 of the cell between the fingers 404. These insulating members 420 are disposed between gaps 406 which separate the fingers 404.
• the insulating members 420 have a width Wl that is greater than a width W2 of the bus bar 410 in the example embodiment. In other embodiments, the relative widths of the insulating members 420 may be different. For example, the width of the insulating members 420 may be equal to that of the bus bar 410.
• the insulating members 420 are dielectric material. Examples of such materials include silicon dioxide, silicon nitride, or other suitable transparent dielectric materials.
• the members 420 may be deposited on the surface 402 of the photovoltaic cell 401 by any suitable process, such as a physical vapor deposition or sputter deposition process.
• the insulating members 420 reduce the amount of heat that is transferred away from the locations where the bus bar 410 is soldered to the conductor.
• the members 420 thus reduce the thermal stresses imparted on the surface 402 of the cell 401, which in turn reduces the formation of cracks in the cell surface 402. As discussed above, such cracks cause a reduction in the output of the cell 401.
• the TCOs may peel off the surface 401 of the cell 402 after soldering because the thermal stresses of soldering can exceed the adhesion strength of the TCOs. As the system described herein reduces and/or eliminates thermal stresses during soldering, these effects are reduced and/or eliminated.
• containing and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
• the use of terms indicating a particular orientation e.g., “top”, “bottom”, “side”, etc.) is for convenience of description and does not require any particular orientation of the item described.

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• 2012
  • 2012-12-28 KR KR1020147021159A patent/KR20140113702A/ko not_active Ceased
  • 2012-12-28 WO PCT/SG2012/000489 patent/WO2013100856A2/fr not_active Ceased
  • 2012-12-28 CN CN201280065635.9A patent/CN104040727B/zh active Active

Non-Patent Citations (1)

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