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PAN Performance

Why PAN Testing Matters

In their role as technical advisors, PI Berlin, a member of the Kiwa Group, often works with project stakeholders to review the module manufacturer’s PAN files. PI Berlin’s analysis has revealed that, while conservative values are occasionally used, more frequently, manufacturer-provided PAN files contain aspirational assumptions for low light performance, temperature coefficients and/or IAM (Incidence Angle Modifier) curves.

Four recent examples of this specifically related to low light performance are detailed here, taken from different modules being considered for four different projects. In these cases, PI Berlin was also shipped samples of the same modules to perform PAN measurements. The resultant measurement-based PAN files were compared to the manufacturer-supplied PAN files. To isolate the low light performance effects, all other PAN parameters were held constant between the two differently-sourced PAN files, which were then used in two PVsyst simulated sites. The site in Dublin, Ireland, has a higher frequency of low light conditions than the second site in Murcia, Spain, leading to more pronounced impacts of low light performance differences.

The results reveal that in all cases, the manufacturers’ low light performance assumptions were more aggressive than PI Berlin’s measurements on the same modules, with deviations in specific energy yield ranging from 1.1% to 2.9%. While these differences might initially seem negligible, using these manufacturer-provided PAN files for utility-scale sites would lead to significant overvaluation in financial models, likely leading to underperforming assets that do not achieve their expected energy yield.

As part of Kiwa’s Module Procurement Best Practices, third-party PAN testing is strongly recommended,  both during module qualification, which is achieved via PVEL’s PQP PAN testing, as well as during batch testing of modules being shipped to the project site, which is offered at all Kiwa Group labs.

Differences in Specific Energy Yield (kWh/kWp) between PI Berlin measured-PAN files and manufacturer-provided PAN files for four different modules at two simulated sites.

Front Encapsulant
Back Encapsulant
Backsheet Color

Materials Assessed

The cell has the greatest impact on PV module performance in the field, and certain cell technologies and designs (e.g., halfcut cell, heterojunction, thin film) can produce more or less energy in high temperature and/or lowlight conditions. However, changes in the following components will impact PAN performance:

  • Cells
  • Encapsulant
  • Backsheet Color
  • Number of Cells
  • Module Size
Explore PVEL’s Test Methodology
Key Takeaways
Scroll through the key takeaways.

This year the PAN Top Performer threshold for specific energy yield increased by 0.8%.

With the higher energy yields of TOPCon and HJT, the top quartile threshold was raised by a relative 0.8% over the 2022 PAN Top Performer threshold. Only two of the sixteen 2022 Scorecard PAN Top Performers would meet this year’s PAN Top Performer requirement.

All PAN-tested bifacial TOPCon and bifacial HJT modules are Top Performers.

Although some bifacial PERC modules are included as Top Performers, every bifacial TOPCon and bifacial HJT module completing PAN testing in time for 2023 Scorecard inclusion was a PAN Top Performer due to higher bifaciality and better temperature coefficients.

HJT dominates, while TOPCon beats out PERC.

Across the 2023 Scorecard test population, the median Pmax temperature coefficient was −0.26 %/°C for HJT, −0.30 %/°C for TOPCon, and −0.33 %/°C for PERC. Due to this HJT and TOPCon will have better power output than PERC at high temperatures.

No clear advantages for low light efficiency across HJT, PERC and TOPCon.

The median low light performance was higher for the PAN Top Performers than for the non-Top Performers. But thus far there is no correlation to any crystalline cell technology having substantially better low light performance than others.

Test Procedure

Three modules for each BOM are tested across a matrix of operating conditions per IEC 61853-1, ranging in irradiance from 100 W/m2 to 1,100 W/m2 and in temperature from 15°C to 75°C. PVEL uses this flash data to modify PAN file parameters, resulting in a custom PAN file that has been optimized to reflect PVEL’s measurements across all tested conditions. The accompanying report for each PVEL PAN file includes all measured data and optimization outputs, as well as the module’s temperature coefficients as calculated from PVEL’s flash test data.

For bifacial modules, the PVEL PAN reports include a “Bifaciality Factor,” or the ratio of the rear-side efficiency to the front-side efficiency, as well as other bifacial performance data.

To illustrate the impact of PVEL’s PAN files, each PVEL PAN report includes simulations based on the PVEL-generated PAN file for two sites: a 1 MW site in a temperate climate at a 0° tilt in Boston, USA, and a 1 MW site in a desert climate at 20° tilt in Las Vegas, USA. The PAN reports also include single-axis tracker simulations for the same locations. The result of each of these simulations is a specific energy yield (kWh/kWp) value which can be used for benchmarking purposes.

Performance of Each Model Type

2023 PAN
Historical PAN

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Click below to see the 11 model types listed as PAN Top Performers.

PAN Test Result Spotlight

Comparing PAN results on TOPCon and PERC BOMs from the same manufacturer demonstrates the TOPCon performance benefits. The PERC BOM was factory witnessed in early 2021, and the TOPCon BOM was produced 18 months later, with otherwise similar materials. All performance aspects of the TOPCon modules improved compared to the PERC modules, including the temperature coefficients, low light performance and bifaciality. This led to the TOPCon module’s specific energy yield being an impressive 2.3% higher than PERC for the Las Vegas simulation, and 1.1% higher for the Boston simulation.

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Continue Exploring the 2023 Scorecard