Chinese module maker Longi has released the results of a six-month test of its back-contact solar modules deployed in an offshore deep-sea experimental installation.
The company stated that the results, covering the January–June 2025 period, were validated by the China National Photovoltaic Product Quality Inspection Center (CPVT).
The experimental site, located off the coast of Yantai, a major Chinese port city on the Yellow Sea, hosts 10 Longi Hi-MO 9 modules featuring hybrid passivated back-contact (HPBC2.0) technology with a 635 W output, alongside 10 TOPCon modules rated at 615 W from undisclosed manufacturers.
The bifaciality factor was reported at 75% for the Hi-MO 9 panels and 80% for the TOPCon modules, with theoretical back-side power of 476.25 W and 492 W, respectively. Empirical data from the testing indicated that the Hi-MO 9 modules delivered a 1.94% higher overall power yield compared to the TOPCon counterparts.
“Hi-MO 9 also performed exceptionally well under low-light conditions,” Longi stated. “Test data from an overcast and rainy day on February 4, 2025, showed a 0.98% per-watt power generation gain, demonstrating excellent performance even under insufficient irradiance.”
The company reported that its back-contact modules achieved an actual back-side power of 32.05 W and a bifacial power of 667.05 W, compared with 33.11 W and 648.11 W for the TOPCon modules, noting that the Hi-MO 9 panels outperformed TOPCon modules across all time periods and irradiance levels.
Longi highlighted that the key factor behind the superior offshore performance of its back-contact technology was lower operating temperature, which was 1.3 C lower than that of the TOPCon modules.
“The empirical results indicate that Longi’s HPBC 2.0 technology provides significant power generation advantages in offshore scenarios. Its strong performance in temperature control, low-light conditions, and operational reliability meets the stringent requirements of offshore PV for high reliability, high efficiency, and low maintenance costs,” the company added.
Further technical details of the testing were not disclosed.
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