Today's variety of photovoltaic (PV) technologies imposes new challenges to laboratories and industries to precisely measure the performance of devices and, consequently, to accurately estimate the energy yield once installed in a specific location. Spectroradiometry has become a key discipline for metrology applied to PV: Spectral irradiance is one of the three parameters according to which solar simulators are classified according to IEC 60904-9; precise spectrum measurements are a key factor in the spectral mismatch calculation. Finally, energy rating calculations according to IEC 61853 involve spectral irradiance conditions different than the AM1.5G standard spectrum. To tackle these issues, since 2011, the International Spectroradiometer Interlaboratory Comparison (ISRC) takes place annually in different locations of Europe with the participation of laboratories, research institutes, and industry partners to assess spectral measurement capabilities and share good measurement practices and protocols. In this paper, several results of the 9th ISRC 2019 are presented, looking in particular at the impact on characterization of new technologies like organic devices (OPV), dye-sensitized (DSSC), and perovskites.

Within the EURAMET ENG55 "PhotoClass" project, several characteristics of photovoltaic (PV) devices beyond their performance at Standard Test Conditions were investigated, including measurements at varying irradiance and temperature. Four groups of PV devices of different size and technology were prepared and corresponding round-robins were run between partner laboratories with substantially different facilities and methods - namely based on spectral or integral measurements. This paper presents the outcome of the four inter-laboratory comparisons dealing with temperature coefficient measurements of the short-circuit current of PV devices, from reference-cell size to full-size commercial modules of mainly several c-Si technologies, but also with some examples of CIGS and GaAs devices. The measurement results are compared via E-n number assessment, hence including measurement uncertainties. The main outcome of this measurement exercise is a very good agreement of all the laboratories although completely different approaches were applied. In some cases, laboratory measurement uncertainties are even considered rather conservative and could therefore be revised. Furthermore, a comparison between bare cells and commercial modules of the same technology is made, which may represent useful information for PV manufacturers.

The performance of PV devices at different operating temperatures is important for determining the energy they produce once deployed. Therefore current-voltage characteristics are measured over a range of typical operating temperatures and the temperature coefficients of the main electrical performance parameters are extracted. They are the temperature coefficient a of short-circuit current, beta of open-circuit voltage and delta of maximum power. The European Solar Test Installation has recently upgraded its capability to determine these temperature coefficients. The existing two setups were improved to be able to cover extended temperature ranges and two further setups and respective measurement procedures were made operational. For all setups revised uncertainty estimates were calculated. Here the setups and procedures are presented, together with the measurement uncertainty for the three temperature coefficients. Measurements were made on seven PV devices and their consistency compared based on uncertainties. It was found that all setups are fully consistent. The advantages of the different setups are also discussed.

At the European Solar Test Installation (ESTI) photovoltaic (PV) reference cells are calibrated traceably to SI units via the World Radiometric Reference (WRR) using natural sunlight. The Direct Sunlight Method (DSM) is described in detail and the latest measurement results and an updated uncertainty budget are reported. These PV reference cells then provide a practical means for measuring the irradiance of natural or simulated sunlight during the calibration of other PV devices.

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 E-n 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 E-n 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. (C) 2017 The Authors and National Renewable Energy Laboratory. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.orgilicensesiby/4.0/).

This paper describes the preliminary results of an intercomparison of spectroradiometers for direct (DNI) and global normal incidence (GNI) irradiance in the visible (VIS) and near infrared (NIR) region. Seven institutions and six spectroradiometers, representing different technologies and manufacturers were involved. All instruments were able to measure GNI; a restricted sub-group of four instruments had the possibility to also measure DNI when equipped with proper collimators. Prior to the intercomparison, all participating institutions calibrated their own instrument(s) according to their usual procedures in order to verify the entire calibration and traceability chain.

At the begin of 2009 the Swiss PV module Test Centre at SUPSI-ISAAC started a new measurement campaign investigating thirteen different modules commercially available on the market. Two modules of each type have been exposed outdoors for energy yield monitoring and a third module, stabilised in advance, has been stored indoors as a reference. The modules covered a large range of different technologies ranging from multi-crystalline silicon (mc-Si) of which two with back-contact cells, 3 single-crystalline silicon (sc-Si), 1 hybrid mono-crystalline technology with amorphous silicon layer (HIT), 1 double junction amorphous silicon (a-Si/a-Si), 1 micromorph (a-Si/μc-Si), 1 Cupper-Indium-Sulfide (CIS) and 1 Cupper-Indium-Gallium-Diselenide (CIGS). The aim of the measurement campaign was to assess the quality of current technologies and the understanding of observed differences between technologies. Outdoor and indoor performance of the modules were analyzed over 15 months performing measurements under real operating conditions. The modules were therefore installed on a ventilated rack where each single module was connected to a maximum power point tracker delivering Im, Vm values in minutes intervals. The indoor measurements consisted in regular measurements under standard test conditions (STC) and 200W/m2, to determine the stability of the devices over time, and some initial temperature coefficient measurements and measurements at different irradiance levels. The annual energy output in kWh/Wp was calculated and simulations were performed based on the indoor measurements. The scope of the simulations was to explain the differences in energy output, by quantifying the losses generated by the two primary mechanisms: the temperature effect given by the temperature coefficient and the efficiency loss at low irradiances. Requirements for future energy rating of PV modules are given together with a discussion about the involved measurement uncertainties.