The function of bypass diodes in solar modules is to minimize the negative effects of shading or to prevent partial cell failure, which reduces the overall performance of the module. Here’s how bypass diodes work and two of the top benefits they provide:
- Shading Compensation. When a solar module is exposed to shading from nearby objects, trees, or buildings, the shaded cells receive reduced sunlight. Shaded cells have a lower voltage and can act as resistors, limiting the current flow through the entire module. This situation can significantly reduce the module’s output power.
- Hotspot Prevention. Shaded or faulty cells within a module can create hotspots. A hotspot occurs when the shaded cells become reverse-biased and act as resistors, causing localized heating. This heating can damage the shaded cells or even the entire module. Hotspots can lead to reduced module efficiency, accelerated degradation, and potential safety hazards.
Do All Solar Modules Have Bypass Diodes?
No, not all solar modules have bypass diodes. The inclusion of bypass diodes in solar modules depends on various factors, including the design, intended application, and the specific requirements of the solar panel manufacturer.
Shaded Mitigation in String Configured Photovoltaic Systems
Bypass diodes are particularly beneficial in string-configured solar systems. They help mitigate the negative effects of shading on the overall string performance. In string configurations, multiple solar panels are connected in series. This means that the current generated by each panel passes through every other panel in the string. This series connection makes the entire string susceptible to power losses when even a single panel is shaded.
When shading occurs on one module within the string, it can significantly reduce the output power of that particular module. As a result, the current flowing through the shaded module is limited, affecting the entire string’s current flow and power output. This phenomenon is known as the “weakest link effect” or the “Christmas light effect.”
By diverting the current around the shaded panel, the bypass diode ensures that the unaffected panels in the string continue to operate optimally. Since the bypass diode provides a low-resistance path, the current can flow through the unaffected panels without hindrance from the shading or reduced output of the shaded panel. This maintains a consistent and higher current flow throughout the string, helping to minimize power losses and maximize the overall string’s power output.
Number of Bypass Diodes
The optimal number of bypass diodes for a solar module depends on several factors, including the module’s design, size, and the specific shading conditions it may encounter. In practice, the number of bypass diodes in a solar module can vary.
Other Methods of Shade Mitigation
SMA has developed built-in shade mitigation within their inverters. The shade mitigation feature in the SMA CORE1 inverter employs advanced algorithms and techniques to minimize the impact of shading on solar array performance. Here’s a high-level overview of how the shade mitigation works in the inverter.
- Independent MPPT Channels: The CORE1 inverter has multiple independent MPPT (Maximum Power Point Tracking) channels. Each channel is responsible for optimizing the power output of a specific group of panels, typically one channel per two panels. This configuration allows the inverter to operate each channel independently, optimizing power production from each group of panels.
- Shading Detection: The shade mitigation feature continuously monitors the solar array to detect shading conditions. It analyzes the incoming power signals from the panels to identify any deviations or anomalies caused by shading. The inverter’s algorithms can detect shading at different levels, from partial shading on a single panel to shading affecting larger sections of the array.
- Dynamic Power Optimization: Once the inverter detects shading, it dynamically adjusts its power optimization process to mitigate the impact of shading. It employs advanced algorithms to find the optimal operating point for each group of shaded panels. The inverter’s control software adapts the MPPT parameters, such as voltage and current limits, for each independent channel to maximize power production from the unshaded panels while minimizing the power losses from the shaded panels.
- Power Redistribution: In some cases, shading can cause significant power imbalances within the solar array. The shade mitigation feature in the CORE1 inverter addresses this issue by redistributing the power flow within the system. It can redirect power from shaded panels to unshaded panels, ensuring a more balanced energy production across the entire array. This redistribution helps optimize overall system performance and minimize power losses due to shading.
- Real-Time Monitoring and Adaptation: The shade mitigation feature continuously monitors the system’s performance in real-time. It analyzes the power output of each channel and adjusts the optimization parameters accordingly. This adaptive approach allows the inverter to respond dynamically to changing shading conditions. And it ensures optimal power production under varying levels of shading.
Big Shine Energy’s engineers will help you find the right solution for your photovoltaic system. Contact us today for more information.
