Half-cut solar cell technology has gained widespread adoption in the solar industry due to its improved efficiency and durability. By splitting traditional solar cells in half, manufacturers reduce electrical resistance, improve shading tolerance, and enhance overall module performance. These advantages have made half-cut modules a preferred choice for utility-scale and commercial solar projects.
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The half-cell module has a four times lower power loss due to power loss being directly proportional to the current squared. The module’s overall efficiency is also increased by the smaller size of the cell as internal resistance is reduced.
However, despite their benefits, a concerning issue has been observed in many new installations, regardless of module manufacturer—unexplained hot spots forming within half-cut solar cells. These thermal anomalies can reduce system efficiency, accelerate module degradation, and, in severe cases, pose safety risks. While hot spots are known to occur in all solar modules, the frequency and patterns seen in half-cut modules raise questions about potential underlying causes.
We will explore the possible reasons behind these hot spot formations, examining whether they stem from inherent design characteristics of half-cut cells, manufacturing inconsistencies, or external environmental factors.
How Half-Cut Solar Cells Differ from Traditional Cells
Half-cut solar cells are a technological evolution of standard photovoltaic (PV) cells, designed to enhance performance and efficiency. Unlike traditional full-sized cells, half-cut cells are created by slicing conventional silicon solar cells in half, effectively doubling the number of cells within a module. This structural change brings several electrical and mechanical benefits but also introduces new considerations for long-term reliability.
Electrical Advantages
The main benefit of half-cut cells is lower electrical resistance, as each cell carries only half the current of a full-sized cell. This reduces resistive power losses, improving overall efficiency, particularly in large solar arrays. Additionally, half-cut cells are more resilient to partial shading.
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Shading of a photovoltaic device stops its power generation, and even partial shading can amount to significant losses in the expected energy harvest.
Unlike traditional modules, which lose significant power when shaded, half-cut modules use a split wiring configuration that allows one half of the panel to keep generating power even if the other is obstructed. This makes them especially useful in areas with intermittent shading from trees, buildings, or debris.
Mechanical Considerations
While half-cut cells offer electrical benefits, their construction introduces new mechanical stress points. Doubling the number of cells increases the number of soldered connections, which can lead to higher failure rates over time, especially in harsh environments with frequent temperature changes. Additionally, cutting cells in half makes them more vulnerable to micro-cracks, which can form during manufacturing, transportation, or installation. These micro-cracks can reduce power output and, in some cases, contribute to the formation of hotspots—an issue increasingly observed in half-cut solar panels.
Mysterious Hot Spot Phenomenon in Half-Cut Solar Cells
Some recent reports have identified recurring hot spots in half-cut solar panels, raising concerns about potential performance and reliability issues. While hot spots are a known challenge in all PV systems, the frequency and distribution seen in half-cut modules have led to questions about whether the problem is inherent to the technology or influenced by external factors. Some solar sites using half-cut modules experience no issues, while others report persistent thermal anomalies, making it difficult to pinpoint a definitive cause.
Some experts have referred to these unusual hot spots as the “butterfly” or “mirroring effect.” This phenomenon occurs when thermal anomalies appear symmetrically across the two halves of the split-cell module, resembling butterfly wings. The underlying cause is still debated, but some theories suggest it may be related to uneven current distribution, bypass diode behavior, or thermal stress variations unique to the half-cut cell design. As these patterns continue to emerge across various installations and manufacturers, further investigation is needed to determine whether the effect is a manufacturing byproduct or a broader systemic issue.
Several potential factors may contribute to these unexplained hot spots:
- Cell-Level Issues: Half-cut cells are thinner and may be more prone to micro-cracks, which can develop during manufacturing, transportation, or installation.
- Manufacturing Defects: The increased number of solder points in half-cut modules creates more potential failure points, increasing the likelihood of hot spots forming.
- Electrical Imbalances: The split-cell configuration can lead to uneven current flow, potentially causing localized heating in certain conditions.
- Bypass Diode and Connection Failures: Half-cut modules rely on more interconnections and diodes, which, if misconfigured or strained, may contribute to hot spot formation.
- Environmental and Installation Factors: Mounting stress, partial shading, debris accumulation, or unexpected thermal effects may interact differently with half-cut modules compared to traditional full-cell designs.
- Combination of Half-Cut and Bifacial Cells: Recent research presented at the EU PVSEC conference suggests that under certain conditions, the combination of half-cut and bifacial designs may increase the risk of hot spots and performance issues. The study also warns that current testing standards may not be equipped to detect modules vulnerable to this type of degradation, highlighting a gap in industry assessment methods.
As more half-cut modules are deployed globally, continued monitoring and research are necessary to fully understand and mitigate these emerging performance risks. Some studies suggest that half-cut panels may be more susceptible to localized heating under specific conditions compared to traditional full-cell modules, while others indicate no significant difference. With no clear industry consensus, further investigation is needed to determine whether half-cut technology itself is a contributing factor or if other variables are at play.
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Challenges in Diagnosing and Addressing the Problem
Identifying the root cause of hot spots in half-cut solar cells remains a challenge due to the lack of definitive studies. While factors like micro-cracks, solder failures, and electrical imbalances are suspected, no conclusive research has confirmed whether the issue is inherent to half-cut technology or influenced by environmental and installation variables. The variability in site conditions—such as climate, shading, and mounting techniques—makes it difficult to establish consistent patterns across installations.
Compounding the issue is the difficulty of detecting these anomalies through standard ground-based inspections. Many hot spots remain invisible to the naked eye and only become apparent through thermal imaging, meaning problems may go unnoticed until they impact performance. Regular drone-based thermographic inspections can help monitor module behavior and catch early signs of degradation.
To address this issue, site owners and operators should take proactive steps:
- Conduct routine thermal inspections to track hot spot development and assess potential risks.
- Collaborate with manufacturers to report recurring cases and identify possible design or manufacturing flaws.
- Consider alternative module configurations if hot spots persist in certain installations, evaluating whether different equipment designs offer better reliability.
Until more industry-wide research provides clear answers, ongoing monitoring and data collection will be essential in mitigating the risks associated with half-cut module hot spots.
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Getting Started with Drone Solar Inspections
The rise of hotspot issues in half-cut solar cells presents a challenge for solar asset owners, but proactive monitoring and analysis can help mitigate long-term risks. While the exact causes of these anomalies remain uncertain, regular thermal inspections provide valuable insights into module performance, allowing early detection of potential failures before they escalate.
Drone-based thermography is one of the most effective tools for identifying hot spots and diagnosing potential failures across large-scale solar farms. Unlike traditional ground inspections, aerial thermal imaging can quickly and accurately detect anomalies, ensuring that maintenance teams can take targeted action. With industry-wide questions still surrounding half-cut cell reliability, frequent monitoring is key to staying ahead of potential performance issues.
At The Drone Life, our FAA-licensed and thermography-certified pilots specialize in drone inspections, providing the high-resolution data needed to assess and address hotspot concerns. If your site is experiencing unexpected thermal anomalies, don’t wait for performance losses to escalate. Schedule a free consultation today to learn how our drone thermography services can help you maintain peak solar farm efficiency.
What's included in YOUR GUIDE...
Techniques for Exposing Warrantiable Items on Your PV Sites.
A Proven Roadmap for Successfully Implementing Drones in Solar.
Strategies for Identifying DC Losses and Avoiding Downtime.
