Direct radiation refers to light coming directly from the Sun, traveling in a specific direction, reaching the Earth's surface or solar panels unhindered. This is the most important light source for solar systems, as this radiation provides the greatest energy production for the solar panel.
Why is direct radiation important for solar systems?
Maximize energy production: Direct radiation is the most intense light source that directly hits the solar panels, ensuring maximum power production and the highest performance.
Optimal operation: Direct radiation provides more energy than diffuse or reflected radiation, so solar panels must be oriented and positioned to make the most of direct radiation.
Tilt and Orientation: The orientation and tilt of solar panels should be designed so that the panels receive as much direct sunlight as possible, especially at the highest point of the sun.
What factors affect direct radiation?
- Time of day : The intensity of direct radiation depends on the position of the Sun. Direct radiation is strongest at noon, when the Sun is at its highest.
- Season: In winter, the sun is at a lower angle, so the intensity of direct radiation decreases. In summer, the radiation is stronger due to the higher sun angle.
- Geographic location: Direct radiation is stronger in areas closer to the equator, while it is weaker near the polar circles.
- Weather conditions: In cloudy weather or foggy conditions, the intensity of direct radiation is significantly reduced and diffuse radiation dominates.
- Shading : Shading from buildings, trees or other obstacles reduces the amount of direct radiation, which negatively affects the performance of solar panels.
Optimizing direct radiation in solar systems
Orientation: The optimal orientation is tailored to the specific geographical location: in the Northern Hemisphere, solar panels are usually oriented south to receive the most direct radiation.
Tilt angle: The tilt angle of the solar panels must be adjusted according to the season and latitude so that direct radiation hits the panel with the greatest possible efficiency.
Solar tracking systems: Solar tracking systems automatically follow the movement of the Sun, thus maximizing the effect of direct radiation.
Minimize Shading: When choosing a location for solar panels, it is essential to ensure a shadow-free environment, especially during midday hours.
Comparison of direct and diffuse radiation
| Property | Direct radiation | Diffuse radiation |
|---|---|---|
| Source | Directly from the Sun | Scattered light from the atmosphere |
| Direction | Coming from a specific direction | Coming from multiple directions |
| Intensity | Larger | Less |
| Significance for solar panels | Dominant light source | Additional light source |
| Dependence on sunlight | It depends heavily. | Depends less |
Example calculation due to direct radiation
Given situation:
- Nominal power of a solar panel: 300 Wp
- Direct radiation intensity: 1000 W/m²
If the solar panel is optimally oriented and its tilt angle is ideal:
Power = Direct radiation intensity × Panel efficiency
If the panel efficiency is 20%:
Performance = 1000 W/m² × 0 , 20 = 200 W
Summary
Direct radiation is the most important light source for solar systems, as it provides the highest energy production. Optimizing the orientation, tilt, and location of solar panels is essential to maximize the use of direct radiation. Although weather and environmental factors can affect its intensity, increasing the efficiency of direct radiation significantly contributes to the performance and long-term economics of the system.