Environmental Engineering Reference
In-Depth Information
called upon to carry out measurements and calculations and submit a wind survey
report.
If usable information about the wind speed is available, computer models can be
used to convert the calculations for wind conditions at nearby sites or for other
heights. Data on shadowing caused by other wind turbines can also be incorporated
into these calculations. The calculations should include the frequency distribution
of the wind speed at the pitch level of a wind turbine.
Annual Energy Output of a Wind Turbine
The frequency distribution
f
(
v
) indicates how often a wind velocity
v
occurs during
the year. This usually involves compiling wind velocities at intervals of one metre
per second (m/s). The performance characteristic of a wind turbine indicates the
electric power
P
(
v
) a wind turbine produces at wind velocity
v
. The builder of the
installation usually provides the performance characteristics. The annual energy
output
E
of a wind turbine is calculated on the basis of both characteristics: the
corresponding value of the frequency distribution for each wind speed is multiplied
by the performance characteristic and then all the results added:
m
s
m
s
m
s
m
s
⎛
⎜
⎛
⎜
⎞
⎟
⋅
⎛
⎜
⎞
⎟
+
⎛
⎜
⎞
⎟
⋅
⎛
⎜
⎞
⎟
+
⎞
⎟
…
8760
∑
()
⋅
()
⋅
Ef v Pv
=
8760
h
=
f P f P
0
0
1
1
h
i
i
i
The annual energy output for the characteristics from Figure 8.16 is
(
E
=⋅
0 0
%
kW
+ ⋅
43 0
. %
kW
+⋅
8 75
% .
kW
+
108 625
. % .
⋅
kW
+
12 3
.%
⋅
205
kW
+
12 6
.%
⋅
435
kW
+
11 9
.%
⋅
803
kW
+
10 5
.%
⋅
1330
kW
+
)
⋅
8 6
.%
⋅
2038
kW
+
8760
h
…
=
1168
5 000 kWh
13
5500
12
5000
11
4500
10
4000
9
3500
8
3000
7
6
2500
5
2000
4
1500
3
1000
2
500
1
0
0
wind power
v
in m/s
wind speed
v
in m/s
Figure 8.16
Left: Frequency distribution of wind speed. Right: Performance curve of a wind turbine.
