Irradiance_Modeling.md

graph LR
    GHI_Decomposition_Models["GHI Decomposition Models"]
    Monofacial_POA_Irradiance_Orchestrator["Monofacial POA Irradiance Orchestrator"]
    Bifacial_POA_Irradiance_Orchestrator["Bifacial POA Irradiance Orchestrator"]
    Sky_Diffuse_Irradiance_Model["Sky Diffuse Irradiance Model"]
    Geometric_Transformation_Utilities["Geometric Transformation Utilities"]
    Extraterrestrial_Radiation_Provider["Extraterrestrial Radiation Provider"]
    Atmospheric_Clearness_Index_Calculator["Atmospheric Clearness Index Calculator"]
    Beam_Irradiance_Component["Beam Irradiance Component"]
    Monofacial_POA_Irradiance_Orchestrator -- "Calls" --> Sky_Diffuse_Irradiance_Model
    Monofacial_POA_Irradiance_Orchestrator -- "Integrates output from" --> Beam_Irradiance_Component
    Monofacial_POA_Irradiance_Orchestrator -- "Calls" --> Geometric_Transformation_Utilities
    GHI_Decomposition_Models -- "Calls" --> Extraterrestrial_Radiation_Provider
    GHI_Decomposition_Models -- "Calls" --> Atmospheric_Clearness_Index_Calculator
    Sky_Diffuse_Irradiance_Model -- "Relies on" --> Geometric_Transformation_Utilities
    Beam_Irradiance_Component -- "Utilizes" --> Geometric_Transformation_Utilities

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Details

The Irradiance Modeling subsystem is a core part of pvlib-python, responsible for transforming global horizontal irradiance (GHI) into its direct, diffuse, and ground-reflected components on a tilted plane (Plane of Array - POA), including specialized models for bifacial PV systems.

GHI Decomposition Models

This component encapsulates various algorithms (e.g., DISC, DIRINT, Erbs-Driesse) for decomposing Global Horizontal Irradiance (GHI) into its direct normal (DNI) and diffuse horizontal (DHI) components. These models are crucial initial data transformations in the irradiance modeling pipeline.

Related Classes/Methods:

• pvlib.irradiance.disc:1778-1879
• pvlib.irradiance.dirint:1928-2020
• pvlib.irradiance.erbs_driesse:2721-2851

Monofacial POA Irradiance Orchestrator

Serves as the primary facade and orchestration point for calculating the total irradiance on a tilted plane (POA) for monofacial PV systems. It integrates outputs from various sub-components (direct, sky diffuse, ground diffuse).

Related Classes/Methods:

• pvlib.irradiance.get_total_irradiance:270-351

Bifacial POA Irradiance Orchestrator

The main entry point for calculating total irradiance on bifacial PV systems, specifically handling the complexities of both front and backside irradiance contributions. It acts as a specialized facade for bifacial-specific calculations.

Related Classes/Methods:

• pvlib.bifacial.infinite_sheds.get_irradiance:376-578
• pvlib.bifacial.infinite_sheds.get_irradiance_poa:184-373

Sky Diffuse Irradiance Model

Calculates the sky diffuse irradiance component on a tilted plane using various underlying models (e.g., isotropic, Perez, Hay-Davies). This is a critical sub-calculation for total POA irradiance.

Related Classes/Methods:

• pvlib.irradiance.get_sky_diffuse:354-458

Geometric Transformation Utilities

Provides fundamental geometric calculations, including angle of incidence (AOI) and projection transformations, which are prerequisites for accurately determining direct and diffuse irradiance components on tilted surfaces.

Related Classes/Methods:

• pvlib.irradiance.aoi
• pvlib.irradiance.aoi_projection:161-201

Extraterrestrial Radiation Provider

Supplies extraterrestrial radiation data, which is a fundamental astronomical input for various irradiance models, especially those involving atmospheric decomposition and clear-sky calculations.

Related Classes/Methods:

• pvlib.irradiance.get_extra_radiation:33-122

Atmospheric Clearness Index Calculator

Computes the atmospheric clearness index, a dimensionless quantity used in various GHI decomposition models to characterize atmospheric conditions and their impact on solar radiation.

Related Classes/Methods:

• pvlib.irradiance.clearness_index

Beam Irradiance Component

Calculates the direct (beam) irradiance component on a tilted surface, considering the angle of incidence and the direct normal irradiance. This is a primary input to the total POA irradiance.

Related Classes/Methods:

• pvlib.irradiance.beam_component:240-267

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