Fisheye sky imaging is a well established and accu-rate method for estimating shading in photovoltaic (PV) applications, however, it requires physical presence and measurements at the studied location. On the other hand, Digital Surface Models (DSM) can be used to estimate horizon shading remotely, and presents a more scalable method for evaluating potential PV installation site efficiently. Nowadays, high resolution DSM data is readily available in many countries, especially for urban environments. This has opened up new potential applications for more efficient shading estimation for aiding the deployment of PV in urban environments where horizon and nearby shading is significant. In this work, the accuracy of DSM-based methods to characterize horizon shading is assessed and compared to that obtained with fisheye imaging based methods. DSMs with different resolutions are studied and results show that high resolution DSMs are comparable. However, the accuracy of lower resolution DSMs will be highly influenced by the characteristics of the studied location.

Background: Soiling can be a major challenge for photovoltaic (PV) installations, depending on their location, as it reduces transmission and can lead to significant losses. Anti-soiling coatings have been demonstrated to reduce soiling losses and thereby increase PV power production. Objective: This article investigates the applicability of a titanium-dioxide-based anti-soiling coating developed by Photocat under the name “ShineOn” for use with PV installations. The main parameter examined is the optical transmission losses, as this directly translates to performance losses during non-soiled operations. Methods: Measurements of transmittance are carried out using both indoor laboratory setups as well as outdoor PV installations, including measurements of the short-circuit current (Isc), incidence angle modifier (IAM) and spectral transmittance. Investigated samples include both full-sized modules and custom-made mini-modules containing a single solar cell. Results: Both indoor and outdoor measurements show minor transmission losses in the range of 0.3 to 0.6 % and negligible effects on the IAM. Additionally, observations indicate that samples should be coated after lamination, as losses for samples coated before lamination are slightly higher. Conclusion: As the transmission losses due to the ShineOn coating are small and no additional angular- dependent losses were observed, the coating is deemed not to be detrimental for PV applications. Proper assessment of the usefulness requires investigations of the anti-soiling properties, for example, through test installations in regions with high soiling rates.

Measuring horizon shading and modeling available irradiance at a prospective site is necessary for accurate estimation of the energy yield of photovoltaic (PV) systems, as well as the expected operation and availability of PV powered products. Fisheye sky imaging is a relatively simple approach to characterize the surrounding horizon, however it's accuracy in estimating the shading loss on short timescales is not well quantified in the literature. In this work we evaluate the shade irradiance loss estimation accuracy of a horizon shading model based on fisheye sky images compared to actual local irradiance measurements from the site of interest. The results show that small errors in he horizon line estimation can lead to high irradiance estimation errors, for short timescales. However, these are mostly averaged out if the sampling period is 15 minutes or higher. The horizon shading maps obtained both with a commercial shading analysis tool, as well as self-calculated from raw fisheye images, tend to overestimating the direct beam shading and small relative errors are observed. Furthermore, ground reflected irradiance has a great influence on vertical surfaces, which was not accounted for in this work.

Background: Soiling can be a major challenge for photovoltaic (PV) installations, depending on their location, as it reduces transmission and can lead to significant losses. Anti-soiling coatings have been demonstrated to reduce soiling losses and thereby increase PV power production. Objective: This article investigates the applicability of a titanium-dioxide-based anti-soiling coating developed by Photocat under the name “ShineOn” for use with PV installations. The main parameter examined is the optical transmission losses, as this directly translates to performance losses during non-soiled operations. Methods: Measurements of transmittance are carried out using both indoor laboratory setups as well as outdoor PV installations, including measurements of the short-circuit current (Isc), incidence angle modifier (IAM) and spectral transmittance. Investigated samples include both full-sized modules and custom-made mini-modules containing a single solar cell. Results: Both indoor and outdoor measurements show minor transmission losses in the range of 0.3 to 0.6 % and negligible effects on the IAM. Additionally, observations indicate that samples should be coated after lamination, as losses for samples coated before lamination are slightly higher. Conclusion: As the transmission losses due to the ShineOn coating are small and no additional angular-dependent losses were observed, the coating is deemed not to be detrimental for PV applications. Proper assessment of the usefulness requires investigations of the anti-soiling properties, for example, through test installations in regions with high soiling rates. A R T I C L E H I S T O R Y Received: April 13, 2021 Revised: September 27, 2021 Accepted: September 28, 2021 DOI: 10.2174/2665976X02666211022150845

The size and number of utility-scale bifacial photovoltaic (PV) installations has proliferated in recent years but concerns over modeling accuracy remain. The aim of this work is to provide the PV community with a validation study of eight tools used to simulate bifacial PV performance. We simulate real 26 kilowatt-peak (kWp) bifacial arrays within a 420-kWp site located in northern Europe (55.6° N, 12.1° E). The substructures investigated include horizontal single-axis trackers (HSATs) and fixed tilt racks that have dimensions analogous to those found in utility-scale PV installations. Each bifacial system has a monofacial reference system with similar front side power. We use on-site solar radiation (global, diffuse, and beam) and albedo measurements from spectrally flat class A sensors as inputs to the simulation tools, and compare the modeled values to field measurements of string level power, rear and front plane of array irradiance, and module temperature. Our results show that state-of-the-art bifacial performance models add ~0.5% uncertainty to the PV modeling chain. For the site investigated, 2-D view factor fixed tilt simulations are within ±1% of the measured monthly bifacial gain. However, simulations of single-axis tracker systems are less accurate, wherein 2-D view factor and 3-D ray tracing are within approximately 2% and 1% of the measured bifacial gain, respectively.