Hello Luis,
Unlike the "Physical Trough" model that calculates optical performance based on a combination of specified de-rate parameters and knowledge of the physical collector geometry (focal length, collector length, etc.), the Linear Fresnel model does not require knowledge of collector geometry aside from the total reflective aperture area and the length of a collector module which are used in determining incident power and heat losses, respectively. Therefore, all collector losses that are dependent on the position of the sun must be included in the Solar Position/Collector Incidence Angle Tables or Incidence Angle Modifier polynomial equations on the Collector and Receiver page. End losses would fall under this category, as would spillage, incidence angle effects, and cosine effects.
Best,
Mike Wagner
NREL