Researchers at the Lublin University of Technology in Poland and University of Jaén in Spain have compared the performance of crystalline silicon (c-Si) solar panels with that of thin-film modules based on cadmium telluride (CdTe), amorphous silicon (a-Si), and copper, indium, gallium and selenide (CIGS) at a testing field in eastern Poland over four years and have found that the c-Si technologies outperform the thin-film counterparts in terms of both power yield and reliability.
“All systems were evaluated according to the IEC 61724-1:2021 standard, with detailed monitoring of energy yields, losses, efficiencies and performance decline over time,” the research's lead author, Slawomir Gulkowski, told pv magazine. “Our study offers one of the first long-term assessments of photovoltaic system performance under the cold-temperate climate of Eastern Europe.”
The analysis covered a 3.42 kW a-Si system, a 21.25 kW c-Si array, a 3.3 kW CdTe system, and a 3.2 kW CIGS installation. All systems, located in Bordziłówka, eastern Poland, were monitored from 2018 to 2021. “Neither the experimental campaign nor the subsequent data processing incorporated special methodological innovations,” the researchers noted. “The study’s novelty lies in its context-specific contributions.”
The tests revealed pronounced seasonal variability across all technologies, with thin-film modules showing markedly lower capacity factors than c-Si, particularly in winter.
Results indicated that c-Si achieved the best overall performance, producing approximately 1,050–1,150 kWh per kW annually, closely followed by CIGS, while a-Si and especially CdTe performed “considerably worse.” The annual performance loss rate was minimal for c-Si, at around –0.7% per year, but reached extremely high levels for CdTe at –15% per year, a behavior linked to early-generation design issues rather than climate conditions.
Seasonal analysis showed substantial winter losses due to snow coverage and low irradiance; however, regular rainfall effectively mitigated soiling. Furthermore, the researchers observed that CdTe modules exhibited “severe underperformance, superimposed by a pronounced performance decline over time, suggesting significant material-related instability.”
The study highlighted three key lessons: crystalline silicon modules remain the most reliable choice for high-latitude regions; thin-film modules require improved stability for long-term durability; and continuous on-site monitoring is essential for realistic performance-loss estimates and informed investment decisions.
The results of the four-year testing were presented in the paper “A study on long-term operation and performance loss rates of various PV
technologies in eastern Poland,” which was recently published in Renewable Energy.
“Although based on a small sample, this pioneering research provides unique empirical evidence for Poland and comparable cold-temperate regions, supporting the sustainable development of PV systems across Eastern Europe, Central Asia and northern North America,” Gulkowski concluded.
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