For grading the product series, concentration factor C has been chosen as a step basis. Then every type will be fully defined by a pair of two parameters — acceptance angle ©A and number of mirrors n. If two different geometries of concentrator will have comparable concentration capabilities, the one with higher acceptance angle will be preferred.

Assumptions:

a) Number of mirrors on one side of symmetrical concentrator will not exceed 5

b) Acceptance angle will not exceed 20°

c) Minimal acceptable concentration factor is limited to 2

Ad a)

More mirrors lead to more complicated technology and production difficulties because height of concentrator rapidly increases and contribution of higher parts of mirrors to the overall concentration is not significant. Taking into account the linear dependance of incremental concentration factor by linear (flat) character of reflecting surface, we cannot expect positive utilisation of mirrors for concentrator with n > 5 even at truncation. Concentrator should have number of mirrors also not less than 3 because below this limit the concentration level cannot reach desired values.

Ad b)

The series will recognize types with different acceptance angles with step 5°. Concentrator with ©A = 5 will for example capture sunlight from 5° spatial cut-off around the optical axis and this type will be with lowest acceptance angle, highest concentration factor, for concentrating primarily the direct radiation. As such concentrator has a large height, possibly it need to be truncated. Acceptance angles higher than 20° on the other side will not significantly concentrate the sunlight, concentration factor will step under 2 what is not in accordance with point c).

Ad c)

Concentration below C = 2 will not advancing sufficiently the flat-plate collector systems.