Are half cell solar panels good?

There are a few main ways that half-cut cells can boost solar panel output and performance:

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1. Reduced resistive losses

One source of power loss when solar cells convert sunlight into electricity, is resistive losses, or power lost during electrical current transport. Solar cells transport current using the thin metal ribbons that cross their surface and connect them to neighboring wires and cells, and moving current through these ribbons leads to some energy loss. By cutting solar cells in half, the current generated from each cell is halved, and lower current flowing leads to lower resistive losses as electricity moves throughout cells and wires in a solar panel.

2. Higher shade tolerance

Half-cut cells are more resistant to the effects of shade than traditional solar cells. This is not due to the cells being cut in half but rather a result of the wiring methods used to connect half-cut cells in a panel. In traditional solar panels built with full cells, the cells are wired together in rows, known as series wiring. In series wiring schemes, if one cell in a row is shaded and not producing energy, the entire row of cells will stop producing power. Standard panels typically have three separate rows of cells wired together, so shade on one cell of one row would eliminate a third of that panel's power production.

Half-cut solar cell technology is a new and improved design applied to the traditional crystalline silicon solar cells. This promising technology reduces some of the most important power losses in standard PV modules, allowing the solar panels and a PV system, in general, to perform better.

The advantages of half-cut solar cells are great and there are no remarkable disadvantages to this technology when compared to traditional modules. In this article, we will provide a detailed explanation of half-cut solar cell technology, how it works, its advantages & disadvantages, and even compare it against traditional and PERC technology.

Novergy Solar, Half-cut solar panels, Cropping and Redesigning, CC BY-SA 4.0

What is a half-cut solar panel?

Half-cell modules or commonly known as half-cut solar panels are the new trend in manufacturing technology. If you are wondering what is a half-cut solar panel? Here we explain it in detail:

Components and materials of the half-cut solar cell

Half-cut solar cell modules are not a technology developed with new and innovative chemical components added to the cell. Actually, the half-cut solar cell technology is based on the traditional crystalline silicon (c-Si) solar cells. This means that the components and materials used to manufacture a half-cut solar cell are the same as the ones for c-Si solar cells, which are the following:

• Printed silver paste (front contact).
• Anti-reflective coating or anti-reflective glass.
• A doped semiconductor made with c-Si (P-N junction).
• Back Surface Field
• Print aluminum paste (rear contact).

While the half-cut solar cell itself shares the same technology as the traditional ones, the fact that sets them apart is a change in the design, which focuses on improving performance and reducing electrical losses from traditional panels.

Cutting in half of the solar cell

Half-cut solar cells start to differ from regular cells because they are cut in half with a process called cleaving, applied to monocrystalline and polycrystalline solar cells. The cleaving process uses high-tech laser technology to cut the cell in half, with the cell delivering the same voltage but half the current.

Since this technology is based on cutting a traditional crystalline silicon solar cell, this means that the conversion efficiency for the half-cut solar cell is theoretically the same as the traditional c-Si cell. Other types of solar cells like PERC and bifacial can be used to manufacture half-cut solar cells.

Structure of half-cut solar panel

A half-cut solar cell panel allocates twice the cells in the same area of a regular module. This means two times the arrays of solar cells within one module, with half-cut solar cells having half the width, keeping the area of the panel the same.

Whole-cell vs. Half-cell solar panel | Source: GSES Global Sustainable Energy Solutions

Generally, modules with 60 solar cells include three substrings of 20 cells in series. The equivalent half-cut solar cell modules have 120 solar cells, divided into six substrings of 20 cells. Each side of the half-cut solar panel has three substrings in parallel, with both sides also connected in parallel. Besides, there is one bypass diode per substring pair. The same case is analog for panels with 72 solar cells or more.

Working mechanism

A half-cut solar panel works the same way a whole-cell one, but it has a few more substrings. Arrays of half-cut solar panels can be connected as well in series or parallel, replacing traditional whole-cell modules, with the voltage being the same in both cases.

Major differences from halving solar cells and increasing the substrings are the production of less current per cell which translates in reduced losses, and the increased tolerance against partial shading.

Advantages of half-cut solar panels

Are you wondering what are the benefits of half-cut solar panels? Here we will list and explain the benefits achieved by implementing half-cut solar cell technology:

Reduced power losses

The main improvement of half-cut solar cell modules is the reduction of electrical losses caused by Joule's Law, which is based on the following equation:

Since half-cut solar cell produces half (1/2) the current per cell, and Joule&#;s Law considers the square current to calculate losses, these cells produce one-fourth (1/4) the power losses, or about 75% less electrical losses. On the other hand, when evaluated at the module level, there is an increased overall current output of 2-4%, which also increases the power output by that same percentage.

Increased partial shading tolerance

Standard vs. Half-cut solar cell module with shade covering 1/3 of the panel | Source: GSES Global Sustainable Energy Solutions

When a PV module is partially shaded, this causes major power losses for the module and the array. Half-cut solar cells include twice the substrings, meaning that shading a single area of a panel will cause reduced losses. Studies show that half-cut solar cell panels produce up to 50% fewer power losses in an array.

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Reduced hot spots and temperature in general

Hot spots are a consequence of partial shading in solar panels. When some cells are shaded, instead of producing power they act as resistances, consuming electricity and therefore increasing their temperature. Half-cut solar cells reduce the current per substring, which in turn reduces the temperature of hot spots, this technology can reduce the peak temperature of hot spots by up to 20ºC.

Higher Cell-to-Module power

While conversion efficiency for a single half-cut solar cell depends on the type of solar cell technology, half-cut solar cells have a higher Cell-to-Module power (CTM) which translates into higher power output. Traditional PV modules have a 94.8% CTM power while half-cut solar cells have a 99.4% CTM power before factoring laser-cut losses, or 98.4% after factoring them.

Integration with different solar cell technologies

Half-cut solar cell technology is a modification in the manufacturing process of PV modules that uses solar cells manufactured under the traditional c-Si technology. As a consequence, half-cut solar panels can be manufactured in combination with PERC and/or bifacial technologies, which can translate as PV modules with fewer power losses, a higher power output, and several other advantages.

How about their disadvantages?

Half-cut solar cell technology is quite beneficial; however, there are a couple of disadvantages to consider:

Manufacturing of Half-cut solar cells represents a large investment in manufacturing equipment

To manufacture the same number of half-cut solar cell modules compared to whole-cell modules, manufacturers need to invest in doubling their tabber & stringers and acquire a piece of equipment to cleave the solar cells. Studies show that half-cell modules cost 0.6-1.2% more than whole-cell modules, but thanks to the power increase, their cost per watt is reduced by 0.8-1%.

Increased probability of bad contacts or cell-inherent defects

Manufacturing half-cut solar cell modules means twice the soldered connections, which translates as twice the probability of bad contacts. Halving the solar cell also increases the probability of causing defective cells which is a downside to the technology for manufacturers. While this is a problem to consider, a manufacturer with proper quality control will not be greatly affected by this.

Half-cut vs. Standard solar panels (Comparison table)

To fully understand the scope of half-cut solar cell technology, it is important to compare it against the standard Al-BSF technology. In this section, we compare both technologies, considering aspects like the number of cells, voltage, current, and others.

Traditional c-Si solar panels use a simple technology that produces several losses and has poor CTM power. Since half-cut solar cell technology is an improvement of traditional crystalline silicon solar technology, reduces loses, increases CTM power, and it provides additional benefits.

Half-cut solar technology reduces electrical losses by 75%, increases CTM power by 3.6%, increases the resistance of the module against partial shading, reduces the operating temperature by handling less current per cell, and reduces hot spot by up to 20ºC. The main disadvantage of half-cut solar cell technology is the slightly higher cost and reduced aesthetics of the module (although for all-black solar panels is barely noticeable).

Half-cut vs. PERC solar panels

PERC solar technology improves the structural design of Al-BSF c-Si solar cells. This technology reduces losses due to the surface recombination process, increases the efficiency by implementing a reflecting metal at the rear surface of the cell, and reduces heat absorption. Comparing PERC against half-cut solar cell technology can provide an insight into which is the best one.

While half-cut solar panels produce 2-4% more power than standard modules, PERC solar cells increase this output by 6%. While this is an important advantage, it is its only point in favor of PERC against half-cut solar cell technology.

Even though PERC technology absorbs less heat from the sun, this technology shares the same shading intolerance and electrical losses as the standard solar panels. Half-cut solar panels might not have the same increased performance as PERC solar modules due to the surface recombination process, but they perform better when partially shaded and have an important reduction in ohmic losses. Moreover, the potential reduction in energy losses caused by shading is something that PERC technology cannot compete with, particularly for the residential sector applications where major obstructions and trees can cause high shading.

However, the good news is that there is no need to choose between PERC and half-cut cells because both technologies can be integrated. This means that a PERC mono half-cut solar panel can be manufactured, including reduction of electrical losses, a higher tolerance against partial shading, reduced heat absorption from the sun, improved efficiency due to reducing surface recombination, and an increased CTM power, all at the same time.

Are half-cut solar panels worth your investment?

Half-cut solar technology is one of the latest attempts of the solar industry to achieve higher efficiency for PV modules. The technology only costs 0.6-1.2% more than standard c-Si PV modules, but it represents a higher power output of 2-4%. This makes it better for limited spaces requiring fewer PV modules.

Implementing half-cut solar panels is not only better for locations with limited space, but also provides better performance in areas that are being frequently shaded. By including more substrings, the system can be partially shaded without causing the large losses that some regular systems have.

While you might worry that with smaller solar cells, the PV module will also be more delicate, this is not the case. Since modules are covered with protecting glass, mono half-cut solar panels will have the same durability as a regular solar panel, making it one of the best investments that can be made in the solar panel industry.

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