Multi Busbar Technology in Solar Panels

Innovation and technology go hand-in-hand in creating a better product. Similarly, manufacturers have improved solar cells with busbars.

5 mins read
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Increasing demand for efficient solar panels led to the development of solar cells with new technologies. This technology increases the efficiency of solar cells, and you get an enhanced version of solar modules for your house and commercial purposes. By the way, have you heard about Busbar and multi-Busbar solar cells? If not, then today you will get to know this along with multi Busbar technology. Also, what are dash line pattern busbars and their influence on solar cells?

What are Busbars in Solar Panel? What is Multi Busbar Solar Cell?

The thin rectangular strip printed on both sides of solar cells is the Busbar. This strip conducts electricity throughout the solar cell. The purpose of this strip is to separate the cells to conduct direct current from the photons and transfer it to the solar inverter that converts it into an alternative current (AV). The common material for making busbars is silver-plated copper to enhance the conductivity on the front and to reduce oxidation at the back. Busbar is denoted by BB in solar cells.

Since busbars influence the efficiency of solar cells, the number of busbars used in a solar cell varies depending on its efficiency. A multi busbar solar cell contains multiple busbars that decrease the total series resistance of the interconnected solar cells. Particularly 5 busbar cells are one of the majorly demanded multi busbar solar cells lately.

2 Standard Multi Busbar Technology

JAN23multi busbar technology
Image by Getty Images on Unsplash+

A solar cell with enhanced efficiency leads to the generation of a highly efficient solar panel or a solar array. Therefore, instead of assessing separately optimizing single solar cell interconnection of solar cell structure must be followed. This can be done by different technological methods.

1. Smart Wire Connection Technology (SWCT)

Meyer Burger company is a company that combines innovation and technology to create unique photovoltaic cells. This company uses Smart Wire Connection Technology as its approach. It is not like the traditional screen-printing method of busbars. In this technique, thin wires are coated in low-melting point alloys and then embedded into a polymer field. This foil is laminated onto the solar cells such that the rounded thin wires are in contact with all the fingers of the solar cell. A traditional approach is followed in the lamination process. Currently, a standard version of 18 wire configuration is followed.

a) Advantages

  1. Low-temperature processing: The technology does not require high-temperature processing because contact between the wires and fingers is made during the lamination process.
  2. 80% less silver usage: There is no need for silver busbars, which means lower consumption of silver.
  3. Suitable: Advanced Bi-facial architectures require silver printed on both sides, but with smart wire connection technology silver is substituted. Thus, this technology is suitable for such advanced architectures.

b) Applications

Smart wire connection technology is applicable for glass-glass, half-cell, and bifacial to make solar panels with higher efficiency.

2. Soldering Method

This traditional method includes interconnection by soldering thin-rounded wires across the solar cells and not flat ribbons. Wires require soldering pads to attach them to the cells so that routing of electrons from the front to the back of the next cell can be done. This is another multi busbar technology.

a) Advantages

  1. In comparison to other welding methods, soldering is done at comparatively low temperatures.
  2. The base material is not melted; thus, it does not influence the interconnection process.
  3. It can be done with various metals and non-metals.

b) Applications

Delicate electronic wires are fused together, and components are fused with the circuit board. Soldering is applicable to galvanized steel, copper pipes, glass, wire, metal sheets, and other such metals.

How Do Multi Busbars Work?

These steps will explain how do multi busbars work-

Step 1: Generated current is collected by fingers (they are perpendicular super-thin metallic grids connected to busbars) and delivered to busbars.

Step 2: Tab wires connect a string of cells; thus, it also collects the current of one cell string. Tab wires are usually soldered to busbars.

Step 3: Bus wires deliver all the collected power from all cells to the junction box. A cluster of tabs wired cells is connected to bus wires in parallel.

In this way, busbars work to collect the current from each cell string and send the collective current to the inverter.

Also See: Do Solar Lights Stay On All Night?

What is Multi Busbar Solar Panel Approach?

Normally busbars are printed flat with soldered flat ribbons. The function of ribbons is to carry current away from the cell while the busbars carry generated current to the cells. However, Multi busbars or MBBs carry current from the fingers through interconnecting ribbons towards the outside in the front of the solar cell. Multi-busbar has the potential to increase the bifacial feature (the ratio of front power to rear power) of the PERC cells. By using multi busbar technique, the solar cell has the following features:

  • Decreased shading towards the rear side of the cell
  • Small rear aluminum fingers print
  • Improved bifacial light-harvesting function

Also See: 100 Watt Solar Panel Output on Cloudy Day

What is 2bb Solar Panel?

Another aspect of multi busbar technology is the number of busbars in solar cells. The oldest types of solar cells have 2 busbars only. They were known as 2BB solar panels. With evolved technology and most solar cells were printed with 3 busbars and then 4 busbars. With increasing busbars, there was a huge reduction in the internal resistance losses and lesser distance between busbars. However, a 2BB busbars is not as efficient as its later versions.

Also See: Do Solar Lights Charge When Turned Off?

What is 4bb Solar Panel? What is 5bb Solar Panel?

To overcome the shortcomings of the 2BB solar panels a new and advanced series of busbar solar cells were made. A 4BB solar panel has solar cells with 4 busbars, and it is more efficient than the previous ones. A series of solar cells printed with 5 busbars makes a 5BB solar panel. It is the most efficient and demanded category nowadays.

What is 9 Busbar Solar Panel?

Solar cells with 9 busbars make up a 9BB solar panel. The module has several cells each with 9 busbars, and they have less internal resistance loss as compared to a 4BB or 5BB solar panel. This is due to the reduced bus spacing which also extends the lifetime of the cell. A 9BB solar cell is least influenced by micro-cracks. It is a type of solar cell deterioration that results from several micro fractures. A 9BB solar cell is thinner thus its coverage is smaller thus allowing more sunlight to reach the cell.

What is 12 Busbar Solar Panel?

A solar panel with 12 busbar solar cells is termed a 12BB solar panel. These panels are more efficient than previously mentioned types of BB solar panels. With a 12-busbar technology the cell will have the least shaded area and its ribbon reduces reflected light. Thus, increasing the current is collected and flowing through the cell string. A 12BB solar cell has less mechanical stress, resulting in the longer durability of the solar module.

What is Dash Line Pattern Busbars?

To further increase the efficiency of multi busbar technology dash line pattern is used. Instead of the standard full-line busbars, industries have come up with a more cost-effective and alternative method of busbar pattern, the dash line pattern busbar. This reduces the use of expensive silver metal paste. Dash line busbars are available in 3-dash, 5-dash, and 6-dash busbars.

These busbars are more sensitive to power degradation and potential cracking. The risks of such problems increase with the number of dash lines. Cracks develop at the corners of the solar cell with increased dash lines and thermal stress.

So, multi busbar technology is definitively influencing and increasing the efficiency of solar cells and collectively solar modules. But still, there is constant debate about how do multi busbars work and whether they are necessary for solar cell efficiency or not. However, how many BB is your solar cell?

Recommended: How Many Volts Does a Solar Panel Produce?

Olivia is committed to green energy and works to help ensure our planet's long-term habitability. She takes part in environmental conservation by recycling and avoiding single-use plastic.

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