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  Nov 10, 2021   

Half-cut solar module: An overview

Half cut solar module

The government aims to switch to the renewable sector, and solar energy proves to be the most efficient and reliable energy source.  

With the increasing solar energy adoption, researchers are striving hard to develop a technology that offers enhanced efficiency at a moderate cost. The half-cut solar cell is an enhanced and efficient version of the traditional silicon-based full solar cell, which results in more power and energy generation from the same roof area.

In this article, we’ve defined the half-cut solar cell in detail. By the end of this article, we hope to give you a detailed understanding of the half-cut solar cell, its benefits and challenges.

According to the International Technology Roadmap for Photovoltaic (ITRPV) forecast, the market for half-cut solar technology will rapidly grow from 2% in 2016 to 40% by 2028.

What is a half-cut solar cell?

Half cut solar cell or twin solar cell is a conventional solar cell divided into two halves using laser technology to increase durability and efficiency compared to the traditional full-solar cell. For example, a conventional solar panel with 60/72 solar cells will come with 120/144 half-cut solar cells, thus improving the power output capacity and durability.

Half-cut solar cells are available as monocrystalline and polycrystalline solar cells. 

Monocrystalline half-cut panels are preferred since the efficiency improvement due to monocrystalline technology and half-cut technology stacks up.

Benefits of switching to a half-cut solar cell:

  1. Reduced Losses– The resistive losses in a half-cut solar cell is reduced compared to the traditional solar cells(Resistive losses are generated during conversion of solar energy into electrical energy by solar cells).

In the half-cut solar technology, the cell is divided into halves which reduces the current generating capacity by each cell by half, thus reducing the power loss.

                                      PLoss= I2R

 Where,  P- Power

                 I – Current(Amp)

                 R – Resistance(Ohm)

The decrease in the current-carrying capacity results in the reduction of power losses.

The reduction in power loss increases the fill factor(The ratio of maximum obtainable power output to the product of open-circuit voltage and short circuit current), thus improving the output efficiency of the solar panel.

2. More tolerance for shading: The half-cut solar cells are more resistant to the effect of shade on the panels than the conventional full solar cell. In conventional full cell solar technology, solar cells are wired together in a series combination. In this scheme, even if one cell gets shaded or damaged, the entire row within that particular series wiring stops operating. 

For example, 

In full cell technology, to achieve 30V, 60 solar cells each operating at 0.5V are connected in series.

In the case of half-cut solar technology, the number of solar cells is doubled i.e. instead of 60, 120 solar cells are required.

If 120 solar cells with each operating at 0.5V are connected in series, then the solar panel will operate at 120* 0.5V= 60V, which is double the required voltage. To make half-cut solar cells operate as the standard solar cell they are wired differently

In this technology, two sets of 60 series-connected solar cells each operating at 30V are connected in parallel(As in parallel the voltage remains constant). This scheme results in improved shading tolerance, as even if one cell gets shaded or damaged the other part will still operate at its optimum.

Half cut solar cell 

3. Space requirement: The power generation capacity is increased in half cut solar cells as compared to conventional solar cells. This enhanced power output results in a reduced number of solar cells, thus saving the space required for installation.

Half-cut solar cell technology proves to be a good alternative for residential, commercial and industrial locations with limited space. 

How do half-cut solar cells prove to be more efficient?

The half-cut solar cell is a modified version of the conventional full solar cell; it comes with cutting edge technology to boost the efficiency and robustness of the solar panel.

The following technique is used to enhance the efficiency and durability of the half-cut solar cell:

  • Increased number of busbars
  • Split junction box design
  • Cell passivation technology
  1. Increased number of busbars:

    The solar cells are metallized with thin strips on the back and front of the solar panel called busbars. The main purpose of the busbar is to connect the solar cell and to facilitate the flow of DC current.

Traditionally, solar panel systems consisted of 2 busbars, but with the growing technology, the count is increased to 5 or 9 busbars to achieve higher energy efficiency.

The increase in the number of busbars offers advantages such as:

  1. The distance required by the electrons to reach the ribbons is reduced, thus facilitating the improved flow of current.
  2. The reduced distance offers reduced internal resistance, thus improving cell efficiency and durability.

2. Split junction box:

The other innovative factor in half-cut solar cells is the split/dual junction box. A junction box is a single unit consisting of a bypass diode for connecting the solar panel to the rest of the system.

The split cell technology is an innovative technology designed to enhance the voltage by reducing the size of the solar cell. 

As the name suggests in the split cell technology, the junction box is divided into three different boxes, with each box consisting of a bypass diode and an internal string. 

Split cell technology offers the following advantages compared to traditional technology:

  1. Less metallization(metal coating): This helps in reducing internal resistance, thus facilitating the flow of current and ultimately saving space. (The amount of module required to generate the energy is reduced, thus resulting in space-saving)
  2. Increased efficiency: The space saved while installing solar cells is utilised to increase the spatial distance between the cells. This design results in an increased internal reflection of light from the back sheet into the cell surface, thus facilitating more power generation.
  3. Reduced operating temperature: The cooler temperature results in increased cell efficiency and reliability.

   3. Cell passivation technology:

The other factor aiding the improvement of efficiency of half-cut solar cells is the “passivation technology”. Passivation is the term used for coating a unique dielectric layer on the backside above the aluminium metallization layer of the cell. 

A cell cannot capture and absorb all the solar radiation, the PERC(Passivated Emitter Rear Cell) layer helps in capturing the reflected solar radiation and producing the energy even under low light conditions

It also helps in keeping the cell temperature low by minimizing the recombination of atoms.

Challenges:

The main two challenges faced while moving from full cell to half-cell manufacturing are:

1. Laser Cutting: Half cut solar cells are mostly PERC (passivated emitter and rear cell), these cells are fragile and hence laser cutting these cells into two halves is a quite delicate process, it requires more well-versed precise equipment.    

2. Stringing Process: Stringing is the process of placing the busbars on each half-cut cell. During the manufacturing of half-cut solar cells, the stringing process adds costs to the panel production process.

Conclusion: 

Half cut solar cell is undoubtedly an advanced version over the conventional solar cell concerning the shading tolerance and enhanced efficiency. 

Monocrystalline half-cut solar panels are preferred at a location with the following condition due to the following advantages:

  1. Roofs with space constraints: The monocrystalline half-cut solar technology offers improved efficiency and panel capacity with a marginal increase in the number of solar panels.
    For example, If 330Wp capacity solar panel (9 modules) were able to generate 3kWp power, then the monocrystalline PERC half-cut solar panel, with 445Wp (9 modules) can generate a 4kWp within the same space(i.e. Up to 30% extra generation capacity).
  2. Shadow risk: Rooftop surrounded by trees or tanks causing partial shadow for a few hours in the day.

SunEdison offers monocrystalline half-cut PERC solar panels in its PRO variant of rooftop solar systems.

If you are still not sure which solar technology suits your location and requirement, don’t worry contact us. We at SunEdison, will guide you through all your queries and provide you with the best possible design solution to maximize energy generation from your roof. 

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