Half-Cut Solar Cell Panels - All You Need to Know

Half-Cut Solar Cell Panels - Everything You Need to Know

In the solar equipment industry, REC introduced a novel concept in solar technology - the half-cut solar cell panel. Traditionally, solar panels consisted of 60 or 72 full cells, with no apparent reason to modify them by cutting them in half.

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Many might not have predicted that half-cut cells would become known as a significant innovation in less than a decade. However, understanding the technology's rationale reveals its multiple advantages over conventional panels. In this article, we will delve deeper into half-cut panels, starting with a brief overview of what they entail.

Understanding Half-Cut Solar Panels

To better understand half-cut panels, let’s revisit conventional solar panels. A solar panel is essentially an assembly of solar cells sandwiched between components like glass and a backing sheet. These cells are made from ultra-thin wafers sliced from silicon rods, organized in rows and columns, allowing for the flow of electricity. Here's how they are typically structured:

Image - Typical solar panel with full cells (source - Canadian Solar)

Half-cut panels, on the other hand, consist of two smaller panels combined, where each has the solar cells sliced in half. This design allows the upper half to operate independently from the lower half. You might wonder why anyone would complicate a functioning model by introducing the delicate process of cutting and soldering cells.

The primary advantage of half-cut panels compared to traditional solar panels is their heightened efficiency. To appreciate how this efficiency is achieved, we must first address the main shortcomings of full cell panels.

Drawbacks of Full Cell Panels

In a typical full cell solar panel, all individual cells are connected in series, linking the positive terminal of one cell to the negative terminal of the next. This configuration causes the voltages of each cell to accumulate. For example, in a panel with 60 cells, where each cell generates approximately 0.5 V, the total voltage is 60 x 0.5 V = 30 V.

However, this series design poses a significant vulnerability: partial shading. If a portion of the panel is shaded, the entire panel suffers a drastic reduction in output. This scenario can be likened to a group project where one team member drops out, causing the entire effort to stagnate.

While it is possible to interconnect cells in parallel, this arrangement results in very low voltage output. Additionally, it necessitates the use of heavy cables for power transmission, as parallel connections lead to cumulative current outputs, increasing losses. This brings us to another critical drawback of full cell panels: resistive losses.

In an ideal situation, the aim is to maintain the highest voltage possible while minimizing current flow, as even minor increases can escalate power loss. Therefore, all solar panels feature series-connected cells. Even the modest 30 milliamperes produced per square centimeter can result in significant losses.

Innovative minds within the industry sought a solution by simply cutting the cells in half, leading to the emergence of half-cut panels!

Benefits of Half-Cut Panels

1. Reduced Resistive Losses

Resistance is the tendency of materials to hinder current flow, with metals being better conductors than plastic or rubber. Even ideal conductors exhibit some level of resistance. You may wonder what this has to do with half-cut panels. The answer is in a fundamental formula:

Ploss = R x I²

Where Ploss denotes power loss, R represents resistance, and I signifies current flow. Higher current flows lead to greater losses, which is further amplified due to the squared relationship in the formula.

By splitting solar cells in half, the voltage remains constant while current is halved, resulting in power loss diminishing by a factor of four. Ultimately, this advancement contributes to the efficiency that the solar industry constantly strives to achieve!

2. Enhanced Shading Tolerance

As previously mentioned, partial shading can compromise the entire panel's performance. However, half-cut panels consist of 120 or 144 smaller cells instead of the traditional 60 or 72. These smaller cells are arranged into two series groups of 60 or 72 each, connected in parallel. This configuration ensures that if one group experiences shading, the other continues to generate power, mitigating losses considerably.

3. Fewer Hot Spots and Reduced Thermal Damage

In a full cell panel, shading on one cell can lead neighboring unshaded cells to dissipate their energy as heat into the shaded cell, which creates a hot spot. Over time, this can severely compromise the solar panel's structural integrity.

In contrast, because half-cell panels have double the cell strings, thermal energy is more evenly distributed, significantly diminishing the potential for hot spots.

Image - Hotspot on a solar panel due to shading (source - syswe.de)

4. Utilizing PERC Technology

The solar cells in half cell panels often employ advanced technology known as Passivated Emitter and Rear Contact (PERC). This method introduces an additional layer on the back of conventional solar cells, optimizing sunlight capture and conversion into electricity.

PERC modules typically exhibit an average of 5% higher efficiency compared to traditional models.

Challenges of Half-Cut Panels

No new technology is without limitations. Although half-cut panels offer numerous benefits, some disadvantages merit attention.

1. Increased Costs

While the concept of cutting cells seemed like a straightforward solution to traditional panel issues, the execution is complex. The processes involved in cutting and soldering cells demand more labor, energy, and machinery, resulting in higher production costs.

However, if you rarely encounter shading issues or can overlook slight efficiency differences, traditional panels may be a more economical option.

2. Higher Risk of Soldering Defects

Soldering connects solar cells via metallic ribbons running throughout the panel. This adhesive bond involves locally melting metal to join the ribbons to the cells. While effective, this method is not foolproof, and the increased number of soldering joints in half-cell panels raises the likelihood of defects.

The Future of Half-Cut Panels

Despite some drawbacks, half-cut panels are rapidly rising in popularity. The ninth edition of the International Technology Roadmap for Photovoltaics (ITRPV) predicts that the market share of half-cut panels will expand from 5% to nearly 40% in the coming years.

As production techniques and machinery continue to improve, the extra time and costs associated with half-cut panel manufacturing are expected to decline. Therefore, it is likely that half-cut panels will dominate the market.

Availability of Half-Cut Panels in New Zealand

In a brief timeframe, nearly all leading solar panel manufacturers have launched half-cut models following the pioneering efforts of REC. New Zealand currently offers a selection of various brands, with the number anticipated to grow:

• LONGi 315W PERC Half-Cut Cell Solar Panel
• REC N-PEAK Black REC315NP Black
• REC N-PEAK REC325NP Black
• Trina Solar 375W Honey M Monocrystalline
• JA Solar 340W 60-Cell Half-Cell Mono PercModule
• Jinko Tiger Mono 355W N Type Half Cell 30mm All Black

In conclusion, half-cut solar panels represent a substantial upgrade from conventional full cell panels due to their capacity to efficiently diminish shading and current losses, making their growing popularity understandable. They may well mark the next significant leap in solar technology!

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