Environmental Engineering Reference
In-Depth Information
Then capacity factor C F is:
G
C
=
(24 )
F
G
R
Captureability C PT is defi ned as:
G
C
=
(25 )
PT
E
F
Captureability is an absolute indicator of the wind turbine plant performance
refl ecting both WT performance and wind characteristics at the site. But capacity
factor is not absolute indicator because rated power can be changed on purpose. For
example, if a WT of very low rated wind speed is built at an excellent wind site, its
capacity factor could be very high although captureability would be quite poor.
When the wind speed probability function is expressed by Weibull function and
the system effi ciency at rated condition is given, the following equation is obtained:
EV
() ()
f V
3
C
1
V
Γ+
(1
3 /
k
)
F
V
ave
(26 )
=
=
3
C
P
h
V
Γ+
(1 1 /
k
)
PT
rated
rated
rated
where V ave is the annual mean wind speed, V rated is the rated wind speed, h rated is the
system effi ciency at rated condition and
is the Gamma function.
Figure 16 shows general relations between C F / C PT and V ave / V rated for h rated = 0.4
and for different Weibull parameter k .
Γ
8
7
CF/CPT(k=2)
CF/CPT(k=1.8)
CF/CPT(k=1.6)
CF/CPT(k=1.4)
6
5
4
3
2
1
0
0.8
1
1.2
1.4
1.6
1.8
2
2.2
V rated /V ave
Figure 16 : General relations between C F / C PT and V ave / V rated ( h rated = 0.4, Weibull
shape parameter k = 1.4-2.0).
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