Kippzonen BSRN Scientific Solar Monitoring System Manual de usuario descargar pdf (Pagina 144)

132

Pyrheliometer and Diffuse Geometry Configurations

ACR or Kipp &

Zonen CH1

Kipp & Zonen 2AP

Tracker with CM

series pyranometer

Eppley

SDK

BSRN with Eppley 8-

48 B/W with similiarity

to ACR

BSRN with Kipp & Zonen

CM Series pyarnometer

with 2000 design

Instrument Characterisitics

R (mm) 8 25.4 30 28 28

r (mm) 4.8 10.4 15.8 15.8 10.4

L (mm) 183 577 600 641 750

z (°) 4 3.5 4.4 3.9 2.9

z (°) 2.5 2.5 2.9 2.5 2.1

z (°) 1 1.5 1.4 1.1 1.3

Sky irradiances expected from 0º to zl from the centre of the sun under various solar zenith

angles (W m )

-2

0° 2.9 12.8 14.4 12.9 11.2

30° 11.1 11.1 12.4 11.1 9.7

60 ° 6.3 6.3 7 6 .3 5.6

Table C 4.1. Sky irradiances expected from 0º to zl from the centre of the sun under various solar zenith

angles (W m ).

-2

C 4.5 Analytical solutions

Since there is not much a problem to assume a mean radiance for the range of 1º to 4º for z', the above

consideration can be solved analytically. The both ends on the angle range correspond sloping and

limiting angles, respectively. An advantage of an analytical consideration is a possibility to be able

to follow the entire process in one equation. Exercises of this kind often provide us an insight into a

new idea. The mean value for I(z') is designated as

For the sun at the zenith or for pyrheliometers,

where

Since z can not exceed the limiting angle and therefore, is very small, approximating the cosine function

with the polynomial development, it suffices to take the first two terms, and then

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Kippzonen BSRN Scientific Solar Monitoring System Manual de usuario Pagina 144