Environmental Engineering Reference
In-Depth Information
Figure 25. Different shadow areas in a plan view.
Figure 23 shows the shadow length due to adjacent absorber plate (s
1
) and adjacent glass
tube (s
2
). Figure 24 shows the shadow length due to collector header box (s
3
). The three
shadow areas are shown in a plan view in figure 25.
These shadow effects are particularly evident in early morning and late afternoon but
have a minimal effect throughout the rest of the time. Based on the solar angles (solar altitude
and solar azimuth), absorber plate dimensions and tilt angle, pitch of absorber plates, glass
tube diameter and collector header box height, a model was developed to estimate the hourly
value of the length of the shade cast by each of the above three effects. We present here the
results of this model.
'
'
l
×
[cos(
α
)
×
tan(
h
)
+
sin(
α
)]
−
L
×
tan(
h
)
s
=
c
N
c
N
Morning:
(30)
1
'
cos(
α
)
×
tan(
h
)
+
sin(
α
)
c
N
c
'
'
l
×
[cos(
α
)
×
tan(
h
)
−
sin(
α
)]
+
L
×
tan(
h
)
c
N
c
N
s
=
Afternoon:
(31)
1
'
cos(
α
)
×
tan(
h
)
−
sin(
α
)
c
N
c
l
γ
l
×
sin(
α
)
+
−
tan(
h
'
)
×
[
L
−
×
cos(
α
)]
c
N
c
'
2
cos(
h
)
2
s
=
N
Morning:
(32)
2
'
cos(
α
)
×
tan(
h
)
+
sin(
α
)
c
N
c
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