As solar technology continues to advance at a rapid pace, photovoltaic (PV) systems have found widespread applications worldwide.
These systems come in various forms and serve diverse environments, including large ground-mounted solar farms, residential and commercial rooftops, integrated solar building designs, and solar-powered streetlights.
In these settings, it’s inevitable that structures, trees, chimneys, dust, clouds, and other elements obstruct sunlight from reaching solar panels.
This raises the question of how much these obstructions affect the efficiency of solar power generation and what solutions can mitigate these effects.
The Solar Cell Configuration
Solar panels are typically composed of multiple solar cells connected in series or parallel to achieve the desired voltage and current outputs.
To maximize the photovoltaic conversion efficiency, each solar cell within a module should exhibit similar characteristics.
However, during usage, issues such as cracks, internal connection failures, or shading can lead to a mismatch in cell performance.
Under suitable lighting conditions, a series of cells shaded in a photovoltaic module can reverse their role, transforming from electricity generators into consumers.
These shaded cells not only contribute nothing to the module’s overall output but also consume power generated by other unshaded cells, leading to a phenomenon known as the “hotspot effect.”
Understanding the Hotspot Effect
The hotspot effect is a concern particularly for crystalline silicon solar panels.
These panels can be susceptible to issues such as cracks or micro-cracks, which may cause internal shading and eventually lead to the destruction of the module.
Even a small amount of shading can result in significant power losses, causing the temperature of the affected cells to rise.
In severe cases, this can result in the melting of solder points and damage to the grid lines, rendering the entire solar panel module useless.
According to reputable international statistics, the hotspot effect can reduce the actual lifespan of solar panels by at least 10%.
Addressing the Hotspot Effect
While the hotspot effect is an inevitable issue, solar panel installations consider shading effects and incorporate protective measures to mitigate its impact.
To demonstrate the long-term viability of solar panels under specified conditions, it is necessary to conduct tests to determine their resistance to the hotspot effect.
This testing is known as the “hotspot durability test.”
The Hotspot Durability Test
The hotspot durability test must strictly follow international standards such as IEC 61215-2005. The test involves several key components and procedures:
Test Setup:
- Stable solar simulator or natural light source with an irradiance of at least 700 W/m² and low irradiance non-uniformity.
- Class C (or better) solar simulator or natural light source with an irradiance of 1000 W/m² ±10%.
- I-V curve tester for solar panels.
- Opaque cover plates with shading increments of 5% for test solar panels.
- Appropriate temperature sensors.
Test Procedure:
- Prior to the test, install the manufacturer-recommended hotspot protection devices on the solar panels.
- Illuminate the unshaded solar panels using the light source from irradiance source 1, measuring their I-V characteristics and maximum power point.
- Short-circuit the panels and use temperature sensors to measure the hottest cell during steady irradiation from source 1.
- Completely shade the selected cell with irradiance source 2 while keeping the panel temperature at 50°C ±10°C.
- Maintain this condition for 5 hours of exposure.
- Re-measure the I-V characteristics and maximum power point of the panels.
Test Requirements:
- Solar panels should not exhibit any severe external defects.
- Maximum power output degradation should not exceed 5% of the pre-test value.
Conclusion
The hotspot effect is a critical concern in the field of solar power generation, particularly for crystalline silicon panels.
It can lead to substantial power losses, damage to solar cells, and, in extreme cases, complete module failure.
Mitigating this effect is essential for maintaining the efficiency and reliability of solar panel systems.
Through stringent testing and adherence to international standards, the solar industry can ensure that solar panels are built to withstand the challenges posed by the hotspot effect, ultimately extending the lifespan of these environmentally friendly power generation systems.
