Installation For Measurement Of Albedo; Installation For Measurement Of Horizontal Diffuse Irradiance - Kipp & Zonen SMP series Instruction Manual

2.7 Installation for measurement of albedo

An albedometer consists of two identical pyranometers that measure the
incoming global solar radiation and the radiation reflected from the surface
below. Albedo is the ratio of the two irradiances, and varies from 0 (dark)
to 1 (bright).
Two SMP3's can be mounted back to back with the standard fixing kit, and the
accessory mounting rod screwed into one of them, to make an albedometer.
For all other SMP's a mounting plate is required. The CMF1 mounting plate is
used for unventilated SMP's and the CMF4 for ventilated instruments. There
is no ventilation unit for the SMP3.
The requirements for installation of the upper pyranometer are the same as
for horizontal global irradiance. The requirements for installation of the
lower pyranometer and mast are the same as for reflected global irradiance.

2.8 Installation for measurement of horizontal diffuse irradiance

For measuring the di use radiation from the sky, the direct solar radiation
must be blocked from the pyranometer dome(s).
A static shadow ring can be used to intercept the direct solar radiation. This
requires frequent manual adjustment as the sun's arc in the sky changes. At
times the shadow ring also intercepts a significant proportion of the di use
sky radiation. Therefore, post-processing of the recorded data is necessary to
correct for this.
Kipp & Zonen produces a universal shadow ring, model CM121, which is
suitable for use at all latitudes.
The alternative to a shadow ring is to use a two-axis automatic sun tracker,
such as one of the models from Kipp & Zonen. The sun tracker uses location
and time information to calculate the position of the sun and point at it
accurately under all weather conditions.
The sun tracker can be fitted with a small disk or sphere mounted on an
articulated shading assembly. The shadow of the disk or sphere is adjusted to
cover the pyranometer dome(s) completely and it will then be shaded correct-
ly throughout the year without adjustment.
Albedo
mounting plate
H
17
R S
Upper screen (white)
Pyranometers
Lower screen (white)
Mast (black)
Equator
Sun
Shadow ring
Pyranometer
Mount
Equator
D