TÜV Rheinland compares BC and TOPCon
Dr. Christos Monokroussos, Global Segment Coordinator for Solar at TÜV Rheinland Group, presented a detailed analysis based on the institute’s lab and field-testing data. He centered his discussion on a specific comparative case study to illustrate how performance differences translate into economic value.
Presenting a comparative case study of two specific types of PV module—BC and TOPCon modules installed in the UK’s Southampton, Monokroussos said the evaluation covered key parameters of nameplate power (STC), temperature coefficient (PMAX, VOC, ISC), low-light performance (100 W/m² to 800 W/m²), incidence angle modifier (IAM), nominal module operating temperature (NMOT), and reverse current coefficient (Arev).
According to product datasheets of the 2 products combined with TÜV Rheinland's own measurements, the BC modules offered higher efficiency at STC, a slightly better temperature coefficient of PMAX, but a lower bifaciality coefficient.
At a 75° incidence angle, IAM of BC modules was about 5.12% higher, and NMOT was roughly 0.5°C lower compared to TOPCon.
The economic modeling for this specific scenario revealed a clear advantage for the BC module. The study found that, compared to TOPCon, the BC model's LCOE was 2.1% lower for the same DC capacity and 3.2% lower for the same installation area. Furthermore, its internal rate of return (IRR) was 2.6% higher for the same DC capacity and 4.7% higher for the same installation area. These outcomes reflect the Southampton case inputs, including system design, cost assumptions, and site conditions.
Overall, the results suggested a modest, but measurable energy yield advantage for BC modules in this study, according to Dr. Monokroussos. However, he stressed that accurate yield assessment should be done on a case-by-case basis for different module types.
Panel Discussion
Following individual presentations from the 2 speakers, they joined a panel discussion with TaiyangNews’ Shravan Chunduri on scaling up BC technology for large-scale deployments.
LONGi’s Alex Li explained that patented production tool advancements, ultra-fast high-precision manufacturing methods, and solar cell architectural innovations now allow LONGi to produce 250,000 back-contact solar cells per day from a single production line, which is 10 times more than 10 years ago, enabling its mass-production feasibility. BC modules also deliver around 30 Wp more power and bifaciality, which pitches them as the better option for utility solar projects worldwide.
Market adoption is rising quickly, according to Li, as he shared that LONGi is expanding its BC production capacity from 20 GW in early 2024 to 50 GW by the end of 2025.Developers and installers also report higher yield and improved long-term reliability performance with BC modules installed in the field, especially during high-temperature periods and low-light hours, which makes BC attractive for utility projects, he stressed.
TÜV Rheinland’s Dr. Christos Monokroussos added that, in certain project scenarios, higher efficiency combined with advanced trackers has been a key factor in making BC more economically viable for large-scale projects. Together, these changes have helped BC gain stronger market acceptance.
Looking ahead, Li expects BC to dominate utility markets by 2028, while Monokroussos sees the technology steadily improving in efficiency and reliability over the next decade, with strong potential to pair with tandem structures. Both speakers agreed that BC is no passing trend, but a lasting part of the solar industry’s future.
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