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

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° to 85°, the range of measurement deviations increases rapidly from 2.5% to 23%. The proficiency of the measurements is analysed 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. This paper presents the results from an interlaboratory comparison of incident angle modifier measurements performed on encapsulated PV devices by 12 international laboratories. It is found that most of the angular‐dependent measurements are reproducible for angles of incidence ≤80°, but measurement agreement suffers at 85° with deviations as high as 23%. The uncertainty that the angular‐dependent measurement deviations contribute to the IEC 61853 climate‐specific energy rating (CSER) is calculated as 1.0%‐1.8%, depending on the climate.