TÜV Rheinland, an internationally renowned authoritative testing institution, released a new test report. The report conducted a systematic comparative test on the power output and local temperature changes of LONGi's HPBC2.0 (Hi-MO X10 module) and TOPCon modules from leading manufacturers under various shading conditions. The results show that the HPBC2.0 module significantly outperforms TOPCon modules in two key indicators: power attenuation amplitude and local temperature rise. Its core technical advantages in coping with shading have been authoritatively verified, providing a more reliable solution for PV power plants to address outdoor operation challenges.
Shading: A Potential Threat to PV Power Plant Operation
Shading is a common challenge in the actual outdoor operation of PV power plants. Although static shading from buildings and terrain can be avoided through pre-planning and design, but random shading such as bird droppings, fallen leaves, snow, and dust remains difficult to be completely eliminated. Despite their seeming insignificance, these random shading issues have a significant impact on system performance and safety.
For PV modules, shading is an unavoidable challenge with severe hazards:
In terms of power generation performance, shaded solar cells transform from power-generating units into energy-consuming resistors, reducing the current output of the entire string of cells. This is what the industry refers to as the "barrel effect"—the final power generation of a string is determined by the weakest power-generating unit. Outdoor field tests show that only 5% shading area can lead to more than 30% power loss.
In terms of reliability, shaded cells consume electrical energy and generate heat, with local temperatures exceeding 100°C. In the short term, this accelerates the aging of packaging materials and cells; in the long term, it will lead to the formation of hot spots. Additionally, shading exacerbates the risk of Potential Induced Degradation (PID), causing irreversible permanent attenuation of module power.
More notably, PV modules are connected via DC cables. Under the long-term effect of high temperatures, the connection points between modules may also undergo accelerated aging, leading to poor contact points under high DC voltage. These points are highly likely to trigger DC arcing—characterized by extremely high temperatures and difficulty in extinguishing—which poses an extremely dangerous fire hazard.
From an economic perspective, the dual pressures of reduced power generation and module replacement costs will extend the investment payback period of power plants and reduce the overall rate of return. Fire accidents may even lead to severe losses for projects.
Technological Innovation: HPBC2.0's "Weak Conduction" Design Breaks Through Industry Bottlenecks
Facing the common industry challenge posed by shading, LONGi's HPBC2.0 module has achieved a technological breakthrough with its innovative "weak conduction" design.
This design enables each cell to independently control its current path. When a single cell is shaded, the blocked current can automatically bypass the shaded area. Through a current shunting design, current reorganization is achieved without activating the module's bypass diodes—effectively locking power loss within the shaded region and ensuring the overall power generation capacity of the system is not significantly affected.
Recent measured data from TÜV Rheinland fully confirms this technical advantage:
In practical tests simulating various shading scenarios on real distributed rooftops, the power loss of the HPBC2.0 module is far lower than that of TOPCon modules.
(Note: AL, Additional Loss. AL = Actual power loss ratio caused by shading-Theoretical loss from shading. Simply put, the higher the AL value, the greater the power loss.)
Under the same shading conditions, the local temperature of TOPCon modules exceeds 160°C, while the local temperature of HPBC2.0 modules rises to over 100°C. Compared with TOPCon modules, the maximum hot-spot temperature is reduced by 77°C, demonstrating excellent capabilities of hot-spot risk control.
In June 2025, LONGi's Hi-MO X10 series products achieved TÜV Rheinland's A+ rating for anti-shading performance under point-like shading conditions. In shading scenarios such as dust, bird droppings, and fallen leaves, the anti-shading effect of Back Contact (BC) technology is significantly superior to that of TOPCon.
In September 2025, National Center of Supervision and Inspection on Solar Photovoltaic Product Quality (CPVT) awarded LONGi's Hi-MO X10 the "Three-Proof" Certificate—the industry's first certification for fireproof, anti-shading, and anti-dust accumulation. CPVT test data shows that in the shading resistance test, when a single cell is 50% shaded, the average power loss of the Hi-MO X10 module is only 10.15%, while that of TOPCon modules is as high as 36.48% — nearly four times higher than the former.
Value Conversion: Driving High-Quality Development of the PV Industry
The technical advantages of the HPBC2.0 module have been converted into tangible power plant value: higher power generation efficiency and longer service life effectively reduce the Levelized Cost of Electricity (LCOE), improve the investment return rate throughout the project's entire life cycle, and provide a solid guarantee for the stable profitability of power plants.
Meanwhile, its excellent shading resistance, safety, and reliability enable the module to be widely applied in diverse scenarios such as wind-solar co-location and complex distributed rooftops, further expanding the application boundaries of PV technology.
Shanghai AB Food & Beverages Limited, the production base of the century-old brand "Ovaltine", has a large number of obstacles such as lightning rods and ventilation ducts on its roof, resulting in severe local shading problems. Recommended by EPC (Engineering, Procurement, and Construction) contractor Shanghai Mi'ang PV, the enterprise selected Hi-MO X10 modules to build a 0.67MW PV power plant, which significantly reduced the impact of shading on power generation efficiency and saves over 870,000 yuan in electricity fees annually.
In Thailand, LONGi, in collaboration with local EPC team PPE Solar, helped Chumponwarin Part., Ltd. Thailand—located 25 kilometers away from Bangkok—installed a 974.08kW PV power plant. During on-site surveys, the EPC team identified shading issues from power grid wires on the factory building and thus resolutely recommended Hi-MO X10 modules. After the project was put into operation, even under low-light conditions during the rainy season, it saves 400,000 Thai baht in electricity fees monthly, equivalent to one-fifth of its electricity expenditure.
TÜV Rheinland's test results are not only full recognition of LONGi's product performance but also another authoritative confirmation of the value of BC technology. With the large-scale promotion and application of high-performance BC modules, the PV industry will achieve new breakthroughs in adapting to complex environments, providing stronger technical support for the global energy transition.
About LONGi
Founded in 2000, LONGi (Stock code: 601012. SH) is committed to being the world's leading solar technology company, focusing on customer-driven value creation for full scenario energy transformation.
Under its mission of 'making the best of solar energy to build a green world', LONGi has dedicated itself to technology innovation and established several business sectors, covering mono silicon wafers, cells and modules, commercial & industrial distributed solar solutions, green energy solutions, building integrated photovoltaic and hydrogen equipment. As an international company, LONGi's business covers more than 160 countries and regions. Actively practicing its "Solar for Solar" concept, LONGi is accelerating the global transition to sustainable energy and promoting energy equity, enabling more people around the world to access affordable clean energy.
