The collector consists of parabolic mirrors, a support structure, and two-axis tracking system. The mirrors focus direct normal solar radiation on the aperture of the receiver. The receiver aperture size is typically optimized to maximize the quantity of reflected solar radiation that enters the receiver and minimize convection and radiation losses out of the aperture.

The relevant sections of the thesis Stirling Dish System Performance Prediction Model (Fraser 2008) https://www.nrel.gov/analysis/sam/pdfs/thesis_fraser08.pdf (4.1 MB) are:

The parameters on the Collector page are used to calculate the power output of the collector. The parameters are for a single dish collector, and are assumed to apply to each dish in the solar field.

Mirror Parameters

Projected Mirror Area (m2)

Area of one concentrator's mirror projected on the aperture plane. Used to calculated the solar power intercepted by the receiver, and the shading factor.

Total Mirror Area (m2)

Area of mirrored parabolic surface. Used to calculate collector diameter, which is used in the rim angle calculation and in the shading factor calculation.

Mirror Reflectance

The mirror reflectance input is the solar weighted specular reflectance.  The solar-weighted  specular reflectance is the fraction of incident solar radiation  reflected into a given solid angle about the specular reflection direction. The appropriate choice for the solid angle is that subtended by the receiver as viewed from the point on the mirror surface from which the ray is being reflected. For parabolic troughs, typical values for solar mirrors are 0.923 (4-mm glass), 0.945 (1-mm or laminated glass), 0..906 (silvered polymer),  0.836 (enhanced anodized aluminum), and 0.957 (silvered front surface).

Performance

Insolation Cut In (W/m2)

Direct normal radiation value above which the cooling system fan operates. Used to calculated parasitic losses.

Table 24. Collector default parameter values.