First Results from a High Precision Indoor & Outdoor PV Module Monitoring Campaign

To aid the design and parameterization of risk models used in insurance solutions for the PV industry, we introduced an innovative combination of repeated laboratory measurements and ongoing test field monitoring. This approach aims at the relationship between the real life experience and the STC based performance warranties. Each four samples of ten different module brands and types have been exposed for five years now. In this contribution, we compare the results of indoor module characterization to module parameters derived from outdoor operation, where IV curves are acquired in regular intervals. Dependent on the time scale, this comparison needs different approaches. When looking at the major influences on a PV module\u92s long term yield, a clear ranking is visible after 5 years of exposition. Deviations from rated values as given in the data sheet have the biggest influence on long-term yield, followed by initial degradation. Differences in cell and module technology are next in the ranking: low light behaviour, angular response and spectral response may help some products to perform better than others. Finally, long term degradation may cause different life time yields, as this (typically small) effect will increase differences in module characteristics with time. In this experiment, degradation rates between 0% and 1% per year have been deduced

Improvements in world-wide intercomparison of PV module calibration

The calibration of the electrical performance of seven photovoltaic (PV) modules was compared between four reference laboratories on three continents. The devices included two samples in standard and two in high-efficiency crystalline silicon technology, two CI(G)S and one CdTe module. The reference value for each PV module parameter was calculated from the average of the results of all four laboratories, weighted by the respective measurement uncertainties. All single results were then analysed with respect to this reference value using the En number approach. For the four modules in crystalline silicon technology, the results agreed in general within ±0.5%, with all values within ±1% and all En numbers well within [−1, 1], indicating further scope for reducing quoted measurement uncertainty. Regarding the three thin-film modules, deviations were on average roughly twice as large, i.e. in general from ±1% to ±2%. A number of inconsistent results were observable, although within the 5% that can be statistically expected on the basis of the En number approach. Most inconsistencies can be traced to the preconditioning procedure of one participant, although contribution of other factors cannot be ruled out. After removing these obvious inconsistent results, only two real outliers remained, representing less than 2% of the total number of measurands. The results presented show improved agreement for the calibration of PV modules with respect to previous international exercises. For thin-film PV modules, the preconditioning of the devices prior to calibration measurements is the most critical factor for obtaining consistent results, while the measurement processes seem consistent and repeatable

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

© 2020 John Wiley & Sons, Ltd. 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