Environmental Engineering Reference
In-Depth Information
Wind
turbine
Figure 5.4
Idealized Change of Wind Speed at a Wind Turbine
(5.16)
The power
P
0
of the wind through the area
A
without the influence of the wind
turbine is:
(5.17)
The ratio of the power used by the turbine
P
T
to the power content
P
0
of the
wind is called the
power coefficient c
P
and is given by:
(5.18)
Betz has calculated the maximum power coefficient possible, which is called
the ideal or
Betz power coefficient c
P,Betz
(Betz, 1926).
With
and
,
the ideal wind speed ratio is
.
When substituting the speed ratio in the equation of the power coefficient, the
maximum power coefficient becomes:
(5.19)
If a wind turbine slows down air with an initial wind speed
v
1
to one third of
v
1
(
v
2
=1/3ยท
v
1
), the theoretical maximum power can be taken, and this
maximum is about 60 per cent of the power content of the wind.
