Effect of torque-tube parameters on rear-irradiance and rear-shading loss for bifacial PV performance on single-axis tracking systems

Pelaez, Silvana Ayala; Deline, Chris; Stein, Joshua S.; Marion, Bill; Anderson, Kevin; Muller, Matthew

doi:10.1109/pvsc40753.2019.9198975

Cited by 12 publications

(12 citation statements)

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“…MCRT can provide valuable information for the accurate modeling of rear illumination in bifacial photovoltaic systems. Previous work already showed the impact of system components ( Pelaez et al., 2019c ; McIntosh et al., 2019 ), this work emphasizes the importance of accurate input assumptions such as the ground optical behavior.…”

Section: Resultsmentioning

confidence: 74%

“…Several studies have investigated a variety of optical effects in bifacial systems through modeling ( Yusufoglu et al., 2014 ; Reise and Schmid, 2015 ; Pelaez et al., 2019a , Pelaez et al., 2019b , 2019c ; Egido and Lorenzo, 1986 ; Pérez Oria and Sala, 1988 ; Lo et al., 2015 ; Lindsay et al., 2015 ; Shoukry et al., 2016 ; Chiodetti et al., 2016 ; Hansen et al., 2017 ; Janssen et al., 2017 ; Vogt et al., 2018 ; McIntosh et al., 2019 ; Horvath et al., 2019 ; Jäger et al., 2020 ). The two common methods for modeling the rear illumination of PV modules are view-factor ( Yusufoglu et al., 2014 ; Egido and Lorenzo, 1986 ; Pérez Oria and Sala, 1988 ; Lindsay et al., 2015 ; Shoukry et al., 2016 ; Chiodetti et al., 2016 ; Hansen et al., 2017 ; Janssen et al., 2017 ; Jäger et al., 2020 ) and ray tracing ( Reise and Schmid, 2015 ; Pelaez et al., 2019a , 2019b , 2019c ; Lo et al., 2015 ; Vogt et al., 2018 ; McIntosh et al., 2019 ; Horvath et al., 2019 ). View-factor methods are used in established solar energy yield modeling software such as PVSyst ( PVSyst, 2021 ); however, they tend to underestimate rear irradiance ( Kang et al., 2019 ; Deline et al., 2019 ).…”

Section: Introductionmentioning

confidence: 99%

“…Edge effects and non-isotropic optical reflections are also usually not taken into account. Monte Carlo Ray Tracing (MCRT) on the other hand provides significant advantages for the modeling of complex optical properties or geometries, for example including system mounting components ( Pelaez et al., 2019c ; McIntosh et al., 2019 ) and are commonly used in the field of concentrated solar technologies for that reason ( Wang et al., 2020 ). A few recent studies have presented ray-tracing results of PV modules.…”

Section: Introductionmentioning

confidence: 99%

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Accelerating the simulation of annual bifacial illumination of real photovoltaic systems with ray tracing

Conechado

Asselineau

2022

iScience

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Summary Accurate modeling of bifacial illumination is critical to improve the prediction of the energy yield of bifacial solar systems. Monte Carlo ray tracing is the most powerful tool to accomplish this task. In this work, we accelerate Monte Carlo ray tracing of large solar systems by nearly 90%. Our model achieves root-mean-square error values of 7.9% and 37.2% for the front and rear irradiance compared against single-axis tracking field reference data, respectively. The rear irradiance modeling error decreases to 18.9% if suspected snow periods are excluded. Crucially, our full system simulations show that surrounding ground surfaces affect the rear irradiance deep into the system. Therefore, unit system simulations cannot necessarily ignore the influence of the perimeter of large installations to accurately estimate annual yield. Large-scale simulations involving high-performance supercomputing were necessary to investigate these effects accurately, calibrate our simplified models, and validate our results against experimental measurements.

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Section: Resultsmentioning

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Accelerating the simulation of annual bifacial illumination of real photovoltaic systems with ray tracing

Conechado

Asselineau

2022

iScience

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“…However, it is more common for simplified bifacial PV performance models to represent racking shading by a constant rear shading factor applied to reduce the total energy yield at the end of the calculation [6]. Torque tube shading can cause reduced and non-uniform irradiance leading to increased electrical mismatch and reduced total energy yield output [7]- [9]. In addition, constant shading factors applied to bifacial PV performance models do not typically account for light that is reflected from the torque tube.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, constant shading factors applied to bifacial PV performance models do not typically account for light that is reflected from the torque tube. Torque-tube-reflected light can increase rear-side irradiance, and consequently energy yield, with approximately 1% electrical mismatch loss [9]. The isolated impact of torque tube reflection on rear irradiance mismatch is not widely reported in the literature.…”

Section: Introductionmentioning

confidence: 99%

Impact of reflective torque tube on rear side irradiance in bifacial photovoltaic modules

Coathup

Lewis

Russell

et al. 2022

Physics, Simulation, and Photonic Engineering of Photovoltaic Devices XI

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Non-uniform irradiance on the rear side of bifacial photovoltaic (PV) modules causes electrical mismatch between cells and energy loss across the module. Racking structures increase this non-uniformity through shadows and reflections that vary throughout the day. However, commercial software typically use constant values to estimate mismatch losses in annual simulations.We investigate the impact of torque tube shading and reflection on rear side irradiance mismatch in bifacial PV modules in one-in-portrait (1P) and two-in-portrait (2P) horizontal single-axis trackers with a range of ground albedos over a typical meteorological year in Livermore, California, USA. Irradiance simulations use a version of bifacial_radiance, the National Renewable Energy Laboratory's python wrapper for the RADIANCE ray tracing software, which we modified for arbitrary 2D irradiance sampling of the module(s) under investigation.For a torque tube reflectivity of 0.745, torque tube reflection accounts for 3.0% and 5.5% of the annual rear insolation in 1P and 2P configurations, respectively, for a 0.2 albedo; or 2.9% and 3.1% for a 0.6 albedo. Torque tube reflection decreases annual rear insolation mismatch from 11.8% to 10.7% in 1P configurations, and from 11.5% to 9.8% in 2P configurations with 0.2 albedo. Similarly, with 0.6 albedo, annual rear insolation mismatch decreases from 12.6% to 11.6% in 1P configurations, and from 11.9% to 10.4% in 2P configurations. However, we demonstrate that annual figures are insufficient for capturing the impact of torque tube reflection; seasonal and diurnal variations must also be considered.

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Estimating and parameterizing mismatch power loss in bifacial photovoltaic systems

Deline

Pelaez

MacAlpine³

et al. 2020

Progress in Photovoltaics

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Nonuniform irradiance on the rear side of bifacial photovoltaic (PV) systems can cause additional mismatch loss, which may not be appropriately captured in PV energy production estimates and software. We evaluated several scenarios including horizontal single‐axis tracking (HSAT) over natural ground‐cover and rooftop‐mounted systems over high albedo reflective roofs. We found mismatch losses of up to 1.5% annual loss for very close‐mounted (0.15 m) rooftop systems, but losses for HSAT systems and high‐ground‐clearance rooftop systems were lower (<0.5%). A simplified empirical relationship was found that links the spatial variation of irradiance (specifically, the mean absolute difference of irradiance) to the resulting mismatch loss factor, with an R2 better than .99. This approximate relationship was experimentally validated on mismatched PV modules, and it provides a basis for rapidly estimating bifacial mismatch loss factors for use in hourly PV performance simulations such as PVSyst or SAM. Additional parameters investigated include (a) climate dependence and module orientation, which were not found to have a strong impact on bifacial mismatch losses and (b) PV module fill factor and bifaciality ratio, which did have a strong linear impact on mismatch losses.

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Effect of torque-tube parameters on rear-irradiance and rear-shading loss for bifacial PV performance on single-axis tracking systems

Cited by 12 publications

References 6 publications

Accelerating the simulation of annual bifacial illumination of real photovoltaic systems with ray tracing

Accelerating the simulation of annual bifacial illumination of real photovoltaic systems with ray tracing

Impact of reflective torque tube on rear side irradiance in bifacial photovoltaic modules

Estimating and parameterizing mismatch power loss in bifacial photovoltaic systems

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