Kiwa PVEL’s measured IAM results using our best-in-class test method show that the IAM values on commercial modules are highly homogenous. This is counter to what has been reported by some other test labs and module manufacturers. See the Measured IAM Fleet graph below for more.
Incidence Angle Modifier
Incidence Angle Modifier (IAM) coefficients evaluate the response of a PV module to light coming from various angles. IEC 61853-2:2016 defines an indoor test method for characterization of the IAM values of a PV device with respect to the angle of incidence (AOI) by measuring short-circuit current (Isc). Kiwa PVEL has improved upon this test method to capture IAM profiles for both glass//backsheet and glass//glass modules. This unique indoor IAM testing method has demonstrated world-leading results for precision and repeatability.
Key
Takeaways
World class measurement accuracy shows minimal variation in IAM performance.
The typical module outperforms the PVsyst default IAM values.
For a single-axis tracking system modeled in Las Vegas, NV using PVsyst, the typical module using its Kiwa PVEL measured IAM values has a higher energy yield than PVsyst’s Fresnel ARC default by a mean of 0.14% and a median of 0.17%. This supports using accurate measured IAM values rather than PVsyst defaults.
Measurable spread in the best and worst IAM performance.
Across almost 40 BOMs of IAM measurements (with three modules measured per BOM), the highest performing BOM had a modelled energy yield 0.52% higher than the lowest performing BOM. This can be a meaningful difference in financial models for utility-scale sites and supports the need for BOM-specific IAM measurements.
Measured data doesn’t align with aggressive IAM assumptions.
Developers and Independent Engineers often contact Kiwa PVEL after module manufacturers provide them with overly optimistic IAM values that are apparently sourced from third-party labs. Kiwa PVEL’s high precision IAM testing concludes that these high IAM values are unreasonable and not supported by our empirical data.
Test Result Spotlight
The consistency across Kiwa PVEL’s IAM measurements may surprise some in the industry who are used to seeing more aggressive IAM values. But despite the relative closeness in IAM measurements, the differences between BOMs can still be significant for project energy and financial models. The zoomed-in IAM graph below compares the lowest and highest performing BOMs that Kiwa PVEL has measured since launching our upgraded IAM test in 2023. Compared to energy models using the PVsyst Fresnel ARC default, the worst performer results in 0.24% lower energy yield and the best performer results in 0.28% higher energy yield when modeled using PVsyst on a single-axis tracking system in Las Vegas, NV.
Measured IAM Across Test Fleet
Kiwa PVEL’s IAM test results across 38 BOMs showing strong consistency. PVsyst’s Fresnel ARC default included for reference.
A case study on why PAN (and IAM) is important, what PV module materials are assessed, and the test procedure for PAN and IAM can be found here on kiwa.com/pvel.
Procure better modules. Get access to the Scorecard data every quarter.
Sign up as a Kiwa PVEL Premium Partner