How to Calculate Solar Irradiance
What is Solar Irradiance?
Solar irradiance is solar power density reaching Earth's surface. It varies by location, time, clouds, and atmospheric conditions.
Step-by-Step Guide
- 1Direct normal irradiance (DNI): beam radiation perpendicular to surface
- 2Diffuse horizontal irradiance (DHI): scattered radiation from entire sky
- 3Global horizontal irradiance (GHI): total arriving at horizontal surface
Worked Examples
Input
Clear day, sea level, solar noon
Result
GHI ≈ 1000 W/m² (AM 1.5 standard spectrum)
Peak theoretical
Common Mistakes to Avoid
- ✕Using peak 1000 W/m² without accounting for clouds and seasons
- ✕Neglecting angle-of-incidence effects
Frequently Asked Questions
How does altitude affect irradiance?
Higher elevation reduces atmospheric path, increasing irradiance. 1000 m altitude ~10% higher than sea level.
Why do solar panels need tilting?
Tilting captures more direct irradiance. Optimal angle ≈ latitude for fixed systems.
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