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Busbar (BB) technology in photovoltaic (PV) cells refers to the conductive metal strips or wires that are printed or placed on the surface of solar cells. The primary function of busbars is to collect and transfer the electrical current generated by the solar cell to the external circuitry or other cells within a module. The design and configuration of busbars have a significant impact on the efficiency, cost, and overall performance of the solar module.
Bus bars are commonly used in electrical panels, switchboards, and other power distribution systems to connect electrical loads to the main power source. They are also used to distribute power to multiple circuits or devices, providing a central point of connection for the electrical system.
Bus bars can come in various shapes and sizes, depending on the specific application and the amount of electrical current they need to handle. They can be flat or cylindrical and can be made with different thicknesses and widths to handle different levels of current.
In the context of photovoltaic (PV) technology, bus bars are used to connect the solar cells within a module, and then connect the modules to form a solar panel. The use of bus bars in PV modules has evolved over time, from a single bus bar to multiple bus bars (such as in MBB technology) to improve the module efficiency and performance.
Function of Busbars
Zero Busbar (0BB) technology is an advanced design in solar photovoltaic (PV) cells where the traditional metal busbars are completely removed from the surface of the cell. In standard solar cells, busbars are metal strips printed on the cell surface to collect and transfer electrical current. However, in 0BB technology, alternative methods like conductive adhesives, smart wire technology (SWCT), or ultra-thin wires are used to replace the busbars.
No Visible Busbars: Unlike traditional solar cells that have visible metal lines (busbars) across the surface, 0BB cells do not have these lines, which maximizes the active area for sunlight absorption.
Increased Efficiency: By eliminating shading caused by busbars, 0BB technology allows more sunlight to reach the active cell surface, improving the cell’s power output and overall efficiency.
Reduced Resistive Losses: The absence of busbars reduces the electrical resistance encountered when the current travels across the cell, leading to better performance and lower losses.
Cost Benefits: Traditional busbars require significant amounts of expensive silver paste. 0BB reduces or eliminates the need for this silver, potentially lowering material costs and production expenses.
In summary, Zero Busbar (0BB) technology is an approach in solar PV cells to enhance efficiency and reduce costs by eliminating traditional busbars and using alternative current collection methods that increase the active surface area for light absorption.
Smart Wire Technology (SWCT) is an advanced interconnection technology used in solar photovoltaic (PV) cells to replace traditional busbars with a network of ultra-thin wires. This technology aims to enhance the electrical performance of solar modules by improving current collection, reducing shading losses, and minimizing material costs.
SWCT is often used in high-efficiency solar cells, like HJT (Heterojunction) or PERC (Passivated Emitter Rear Cell), where optimizing efficiency and minimizing losses are key. It is especially popular in combination with zero busbar (0BB) designs, where traditional busbars are eliminated in favor of smart wire grids.
In summary, SWCT (Smart Wire Technology) is an interconnection method that improves solar cell efficiency and durability by using a grid of thin wires to replace traditional busbars, reducing shading, enhancing electrical performance, and reducing material costs.
This is a new design for solar cell power conducting design. Instead of stripes as in MBB or SMBB technology, ZBB has very tiny wires for transferring energy into cells and between cells. The simple way explanation for ZBB is the smallest interconnection at the solar cell that is better for the performance and strength of cell.
The key element of SmartWire is the copper wire composite film, which mainly consists of an electrically insulating optically transparent film, an adhesive layer on the film surface, and multiple parallel coppers wires (tabbing ribbons) coated and embedded within the adhesive layer. The copper wires are bonded to the surface of the film using the adhesive layer, and their surface protruded with a low-melting-point alloy coating from the adhesive layer.
The alloying of the film and grid is achieved through lamination. The copper wire composite film is connected to the solar cell, serially connecting the solar cells. It is then overlapped with the encapsulation film, backsheet, or glass, and a stable electrical connection is formed between the tabbing ribbons and the grid during the heating lamination process.
The copper wire composite film is laminated on the surfaces of adjacent solar cells to form a series connection. Compared to conventional solar cell packaging processes, the interconnection of the main grid solar cells is achieved by using a new type of stringer machine to lay the copper wire composite film on the front and back surfaces of two cells, enabling the series connection of adjacent cells. After the cells are interconnected, they are arranged and stacked, and under certain lamination temperatures and pressure, the copper wires and the solar cell grids are pressed together to form an ohmic contact.
The surface where busbar ribbons are located isn’t used for generating electricity. Removing the ribbons creates more space on each cell and increases panel efficiency.
The current half-cell module cells need to be spaced apart, which also takes up valuable space on the panel.
Busbar ribbons can also shade PV cells. In multi-busbar modules, round wires instead of flat, rectangular ribbons already reduce a substantial amount of shading. But with zero busbar technology, the shading is cut to zero.
Busbar ribbons are usually flat strips or round wires made of silver- or tin-plated copper, although other, less common compositions exist.
Silver plating enhances conductivity on the front and reduces oxidation on the rear side. Zero busbar panels don’t require those metals, which can reduce the overall cost.
For residential and even for C&I the aesthetic of a solar panel is probably an important deciding factor for you.
0BB PV panels offer a new generation of stylish, all-black aesthetics. They look modern and more sophisticated than earlier models with busbars.
The manifestation of micro-cracks in solar panels can occur at various stages of their transport or installation and throughout their entire life cycle. Thermal cycling, which involves changes in temperature during the day and night, is one of the main causes of micro-cracks after installation.
As the materials in the panel expand due to heat during warmer hours and contract during colder hours, the discrepancy in the rates at which different materials expand can lead to thermo-mechanical cracks under the busbars. The copper in busbars, for example, shrinks faster than the silicon, making it more susceptible to micro cracks. While these micro cracks may not always affect the efficiency of the modules, they can result in power output losses of up to 2.5%.
Shading causes a significant problem for PV module efficiency. When an area on a solar panel is partly in shade, it affects the electrical conduction. So, not only is the shaded area unable to produce energy, but the conductivity of busbars is also reduced.
Busbar-less panels have reduced the distances current needs to travel, significantly improving efficiency in the shade.
In the context of solar PV technology, particularly heterojunction (HJT) cells, “0BB” or “Zero Busbar” technology refers to an advanced design approach aimed at improving the efficiency and aesthetics of solar cells. Here’s a detailed overview:
Highest Efficiency and power of solar panels
30 years with only 0,25% annual degradation
N-type HJT Bifacial Cells cover in Glass glass frame
In summary, 0BB technology in solar PV, especially in HJT cells, represents a cutting-edge approach to increasing efficiency, reducing material costs, and improving aesthetics. While there are challenges in terms of manufacturing complexity and reliability, the potential benefits in terms of power output and cost-effectiveness make it a promising development in the PV industry.
In summary, 0BB technology in HJT solar cells offers superior resistance to PID and LID, enhances efficiency by reducing shading and resistive losses, significantly lowers costs through reduced silver paste usage, and maintains better performance across varying temperatures due to an improved temperature coefficient.
Long warranty for power production >30 Years
Highest Efficiency >24%
Low Yearly degradation, only >0,25%
Best Bifiaciality efficiency >95%
Lowest Temperature Coefficient 0,24%-026%/°C
Very low modules failure risk factor
HJT solar panels have the best efficiency in serial production. Scope of it is between 21%-22,53% with R&D plan even to 26%. N-type module has the best performance and most reliable characteristic resistance for most common fail from all over solar technology.
HJT with N-type technology solar Panels with 120 cells have a scope of power between 370W-390W and for 144 cells 425W – 470W. Newest standard 132 cells has standard 700W from Mysolar manufacturer. At the end of 2022 Power of HJT modules will achieve >500W, >600W and now >700W.
N-type technology ensures a long safe warranty for 30 years of production and 12 -30 years for a panel, depends on the producers. It’s more approx. 5 years than common PERC panels.
HJT solar panels with N-type cells are value for money solutions. Compare with standard backsheet modules, the price for Heterojunction is a little bit more. But compared with Bifacial, glass-glass solar panels, HJT is the best solution and has more advantages worth a few % higher price.
Higher power, bifaciality, efficient production under extreme conditions, combined with the world’s lowest degradation, no LID and PID effects and a double glass structure (GLASS-GLASS), allows you to generate significant savings over 30 years of use compared to PERC panels.
Glass is the best protection for the silicon cells that are the heart of the photovoltaic module. A cell is a unit that generates electricity, but it is made of a delicate material that needs to be reinforced and secured externally. For this purpose, we have a good ally in the form of solar glass, which, in addition to being transparent, is an electrical insulator.
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