Electroluminescence (EL) imaging is a PV module characterization technique, which provides high accuracy in detecting defects and faults such as cracks, broken cells interconnections, shunts, among many others; furthermore, the EL technique is used extensively due to a high level of detail and direct relationship to injected carrier density. However, this technique is commonly practiced only indoors-or outdoors from dusk to dawn-because the crystalline silicon luminescence signal is several orders of magnitude lower than sunlight. This limits the potential of such a powerful technique to be used in utility scale inspections, and therefore the interest in the development of electrical biasing tools to make outdoor EL imaging truly fast and efficient. With the focus of quickly acquiring EL images in daylight, we present in this article a drone-based system capable of acquiring EL images at a framerate of 120 frames per second. In a single second during high irradiance conditions, this system can capture enough EL and background image pairs to create an EL PV module image that has sufficient diagnostic information to identify faults associated with power loss. The final EL images shown in this work reached representative quality SNRAVG of 4.6, obtained with algorithms developed in previous works. These drone-based EL images were acquired with global horizontal solar irradiance close to one sun in the plane of the array.

In this work we investigate the characteristics of solar cells cracks in photovoltaic (PV) modules for understanding the extent to which the solar cell electrical parameters change due to cell crack degradation. The experimental investigation is performed on two custom nine-cell mini-modules of mono-and multi-crystalline silicon, respectively, where each solar cell in the module has a junction box, allowing individual and module level characterization. Results show that power loss caused by cell cracks is driven primarily by a reduction of the cell's maximum power point current, in particular B type cracks. C cracks also affect the short circuit current of the cells, whereas cells with combined B and C cracks show the most reduction of the short circuit current. Equivalent circuit diode model curve fitting and analysis of the light or dark I-V curves proved of limited used in analyzing degradation of cracked cells, as the model assumptions break down. However, a comparative analysis of dark and light I-V curves with a Suns-Voc curve was better suited for understanding the evolution of diode parameters on cracked cells for increasing levels of degradation.

Electroluminescence (EL) and photoluminescence (PL) imaging are powerful solar cell and panel characterization techniques that are capable of detecting early stage solar cell failures and degradation with high sensitivity and level of detail required for proper preventive maintenance. The electrical contacts needed during measurement pose a challenge for many inspection scenarios, both for EL and PL. Light or Laser induced luminescence (LIL) is a contactless way to generate spatially resolved images of PV panels that highlight poorly connected cell areas, such as finger failures, areas with high series resistance or disconnected cell cracks. In this study, we analyze the characteristics of the LIL scan imaging method in detecting cracks in mono-Si cells, comparing single frames with reconstructed contactless EL images built with a full LIL scan image stack. A comparison between contactless EL generated by LIL and conventional contact EL is made, and finally an estimation of the required laser intensity for outdoor LIL is provided, in correlation to known contact EL performance during nighttime and daylight conditions.

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.

One year of spectrally resolved direct normal irradiance (DNI), diffuse horizontal irradiance (DfHI) and global horizontal irradiance (GHI) data measured in Roskilde, Denmark are analyzed in terms of the average photon energy (APE). We show that the APE of the GHI component is characterized by spectral distributions with low standard deviations, which is consistent with the findings of previous authors. In contrast, the APE of the DfHI and DNI components show spectral distributions with higher standard deviations, which suggests that a given APE value for DNI or DfHI can represent a wider array of spectral distributions. Finally, it is shown that the DfHI APE is characterized by high energy spectral distributions, which has significance in the case of building integrated photovoltaic (BIPV) applications where the glass superstrate is colored or textured in a way that it reflects blue light.