Optical efficiency in concentrator systems
Optical efficiency measures the fraction of incoming solar energy that reaches the receiver after passing through mirrors, lenses, and other optical elements. It accounts for reflection losses, shading, tracking errors, and absorption in optics.
Components affecting optical efficiency:
- Reflector reflectance: the proportion of light reflected by mirror surfaces.
- Geometric losses: shading and blocking between mirrors and receivers.
- Cosine losses: projection effects as incidence angle departs from normal.
- Tracking and alignment errors: mispointing reduces the fraction of light captured.
How it is measured:
- Field measurements: using pyrheliometers on a collector reference surface and at the receiver to compare direct beam power in and delivered power out.
- Modeling and ray tracing: optical models simulate expected losses from geometry and materials.
- In-situ flux mapping: cameras or flux sensors at the receiver measure actual flux distribution and total power.
Improving optical efficiency focuses on high-quality mirrors, accurate tracking, field layout optimization, and regular cleaning and maintenance. Accurate measurement supports performance guarantees and guides operational decisions.