Definition
Diffuse irradiance is the portion of solar radiation that has been scattered by atmospheric particles, clouds, and aerosols, reaching the surface without a defined direction. Important in cloudy climates where diffuse can exceed 50% of GHI.
Key Takeaways
- Diffuse = scattered solar radiation reaching surface from all directions.
- Cloudy climates: 50–70% diffuse fraction.
- Trackers benefit less in high-diffuse climates.
- Bifacial gain higher in high-diffuse environments.
- Measured by separating GHI = DNI × cos(zenith) + DHI.
Frequently Asked Questions
2 commonly searched questions about Diffuse Irradiance.
What is diffuse irradiance?
Scattered solar radiation reaching a surface from all directions, not the direct beam. Includes sky diffuse and reflected ground irradiance.
Diffuse fraction by climate?
Tropical/cloudy: 50–70% of GHI. Temperate: 30–50%. Desert: 15–25%. Affects optimal solar design and tracker vs. fixed choice.
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