CPV: Optical and Tracking Geometries
Concentrating photovoltaics (CPV)
use optics to concentrate sunlight onto small receivers,
and require the movement of the optics
to keep the sunlight focused.
Typically, CPV systems consist of sun-tracking modules,
each incorporating an optical system and corresponding receivers.
Most existing CPV systems can be classified according
to the type of optics they use -- reflective or refractive,
and line-focusing or point-focusing --
and the type of tracking they use -- one axis, and multi-axis.
As the following table illustrates,
the required type of tracking
and practical concentration ratios are determined
by the optics' focusing properties.
|
Type of concentration |
| Focal shape |
Line |
Point |
| Tracking motion |
One-axis |
Two- or multi-axis |
| optics |
Refractive
typically, thin rectangular Fresnel lenses
with optical planes (line-focusing),
or optical axes (point-focusing)
|
|
| Reflective
typically, mirrors shaped as parabolic
surfaces of translation (line-focusing),
or of revolution (point-focusing)
|
| Concentration ratio |
Moderate: 10-100 : 'MCPV' |
High: 100-10000 : 'HCPV' |
Source: Sun Synchrony
