1. Weather and Design

Obtaining irradiance and weather data is typically the first step in setting up and running a PV performance model.  Historical data is typically used to predict output of proposed systems, while real or near-real time data is used to model the output expected from an operating system to validate that it is functioning properly.

• Sun Position
  • Solar Position Algorithm (SPA)
  • Basic Solar Position Models
  • Sandia’s Ephemeris Model
• Irradiance & Insolation
  • Characterization of Irradiance Variability
    • Interannual variability
    • Short-term variability
    • Spatial variability
  • Extraterrestrial radiation
  • Air Mass
  • Direct Normal Irradiance
    • Piecewise Decomposition Models
    • DIRINT Model
  • Global Horizontal Irradiance
  • Diffuse Horizontal Irradiance
  • Spectral Content
    • AM 1.5 Standard Spectrum
  • Weather Data Sources for Performance Modeling
    • National Solar Radiation Database
    • Spectral irradiance dataset from Albuquerque
• Weather Observations
  • Air Temperature
  • Wind Speed and Direction
  • Precipitation
  • Air Pressure
• Array Orientation
  • Fixed tilt
  • Single Axis Tracking
  • Two-Axis Tracking
  • Array Orientation Errors
    • Effect of Array Tilt Errors
    • Effect of Array Azimuth Errors
• Plane of Array (POA) Irradiance
  • Calculating POA Irradiance
    • POA Beam
    • Angle of Incidence
    • POA Ground Reflected
      • Albedo
    • POA Sky Diffuse
      • Isotropic Sky Diffuse Model
      • Simple Sandia Sky Diffuse Model
      • Hay and Davies Sky Diffuse Model
      • Reindl Sky Diffuse Model
      • Perez Sky Diffuse Model
• Shading, Soiling, and Reflection Losses
  • Incident Angle Reflection Losses
    • Physical IAM Model
    • ASHRAE IAM Model
    • Martin and Ruiz IAM Model
      • Soiling effects on Incident Angle Losses
    • Sandia IAM Model
• Satellite Derived Data