BC outperforms TOPCon - Part 3: Heat stress exposes weaknesses in TOPCon modules while back contact module remains stable

While solar panels are designed to harness the sun, too much uncontrolled heat can turn a power generator into a safety hazard. We have previously explored how shading can lead to rapid temperature spikes in our marshmallow and balloon experiments. Now we return to the test site with a common breakfast item to visually demonstrate the severity of the hot spot effect: an egg. This simple test reveals why the choice of module technology is critical for the long-term safety of residential and commercial rooftops.

Raw eggs reveal the intensity of TOPCon hotspot temperatures

In this latest trial, we placed a back contact module, specifically the Hi-MO X10, side by side with a standard TOPCon module. Both panels were subjected to simulated high temperature outdoor conditions typical of a hot summer day. To trigger the hot spot effect, we blocked a specific portion of each module for approximately eight minutes. Once the panels were sufficiently heated by this shading stress, we cracked a raw egg directly onto the surface of the shaded area of each module.

TOPCon cooks the egg while BC keeps temperatures under control

The visual results were immediate and startling. The egg placed on the TOPCon module began to fry almost instantly, turning white and solidifying just as it would in a frying pan. This reaction confirms that the surface temperature had reached dangerous levels capable of cooking food. In stark contrast, the egg on the BC module remained raw and liquid, showing no signs of cooking.

The thermal measurements taken during the test explain this dramatic difference. The hotspot on the TOPCon module soared to a scorching 176.5°C. Meanwhile, the BC module maintained a much lower hotspot temperature of 96.7°C. This difference of nearly 80 degrees Celsius highlights how differently these two technologies handle the stress of shading.

Weak conduction design prevents current blocking and overheating

The reason for this disparity lies in the internal architecture of the solar cells. When a standard TOPCon module is shaded, the blocked current forces the cell to heat up rapidly, creating the intense hot spots we witnessed. This phenomenon creates a fire risk and can damage the module over time.

The LONGi’s back contact module Hi-MO X10 utilizes a unique weak conduction design and a specialized bypass diode structure. This engineering allows the electrical current to bypass the shaded area rather than building up as heat. By effectively suppressing hotspot formation before it becomes hazardous, the back contact architecture acts as a safety guard for the entire roof.

Choosing back contact modules ensures safety and protects property value

These tests prove that safety features are just as important as power efficiency. A module that reaches 176.5°C under common shading conditions poses a genuine risk to the building it sits on. By maintaining significantly lower temperatures even when shaded, the Hi-MO X10 eliminates extreme hot spots. This reliability secures not just the energy yield of the power station but the safety of the property itself.

Learn more about the Hi-MO X10 here.

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