Interlaboratory comparison of angular-dependent photovoltaic device measurements: Results and impact on energy rating

Nicholas Riedel*, Adrian Alejo Santamaria Lancia, Fabian Plag, Ingo Kröger, Malte R. Vogt, Carsten Schinke, Rasmus Schmidt Davidsen, Mekbib Wubishet Amdemeskel, Mark J. Jansen, Petra Manshanden, Lenneke H. Slooff, Anna J. Carr, Martin Bliss, Tom Betts, Mikel Ezquer Mayo, Iñigo Petrina Jauregui, José L. Balenzategui, Ruben Roldan, Giovanni Bellenda, Mauro CaccivioUlli Kräling, Frank Neuberger, Daniel Zirzow, Jim Crimmins, Charles Robinson, Bruce King, Wesley Teasdale, Cherif Kedir, John Watts, Ryan Desharnais, Peter Behrensdorff Poulsen, Michael Linde Jakobsen, Gisele Alves dos Reis Benatto

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review


This paper presents the results from an extensive interlaboratory comparison of angular-dependent measurements on encapsulated photovoltaic (PV) cells. Twelve international laboratories measure the incident angle modifier of two unique PV devices. The absolute measurement agreement is ±2.0% to the weighted mean for angles of incidence (AOI) ≤ 65°, but from 70°–85° the range of measurement deviations increases rapidly from 2.5%–23%. The proficiency of the measurements is analyzed using the expanded uncertainties published by seven of the laboratories, and it is found that most of the angular-dependent measurements are reproducible for AOI ≤ 80°. However, at 85° one laboratory’s measurement do not agree to the weighted mean within the stated uncertainty, and measurement uncertainty as high as 16% is needed for the laboratories without uncertainty to be comparable. The poor agreement obtained at 85° indicates that the PV community should place minimal reliance on angular-dependent measurements made at this extreme angle until improvements can be demonstrated. The cloud-based Daidalos ray tracing model is used to simulate the angular-dependent losses of the mono-Si device and it is found that the simulation agrees to the median measurement within 0.6% for AOI ≤ 70° and within 1.4% for AOI ≤ 80°. Finally, the impact that the angular-dependent measurement deviations have on climate specific energy rating (CSER) is evaluated for the six climates described in the IEC 61853-4 standard. When one outlier measurement is excluded, the angular-dependent measurements reported in this work cause a 1.0%–1.8% range in CSER and a 1.0%–1.5% range in annual energy yield, depending on the climate.
Original languageEnglish
JournalProgress in Photovoltaics
Publication statusAccepted/In press - 2021


  • Angle of incidence
  • Incidence Angle Modifier
  • Relative transmittance
  • Interlaboratory comparison
  • Optical losses
  • Angular-dependent losses
  • Energy Rating
  • Diffuse irradiance


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