Environmental Engineering Reference
In-Depth Information
|
E
R
,
S
|
I
|
E
WT
,
D
|
Z
I
=
(9-26a)
where
Z
I
= idealized signal scatter ratio
|E
R, S
|
I
= idealized amplitude of the scattered signal field at the receiver (mV/m)
Receiver Located in the Backward Scattering Zone
Z
I
=
S
B
E
A
P
h
lz
cos (f
RT
/2) , -08p £ f
RT
£ 0.8p
(9-26b)
æ
ê
í
0.80exp(-2.30Db)
f or metallic HAW T blades
0.33exp(-2.30Db)
f or non
-
metallic HAW T blades
S
=
h
(9-26c)
ê
0.80l/
L
f or metallic Darrieus blades
0.33l/
L
f or non
-
metallic Darrieus blades
è
2p
R
l
sin(2q) cos(f
RT
/2) £
B
E
,max
B
E
= 1 +
sinc
(9-26d)
l
R
/
A
P
f or HAWT rotors
B
E
,max
=
(9-26e)
2
f or Darrieus rotors
where the condition
B
E
£
B
E, max
ensures that the amplitude of the scattered signal is less than
that of the direct signal at distances greater than the rotor radius
R.
Receiver Located in the Forward Scattering Zone
B
E
A
P
lz
Z
l
=
h
cos(2f
RT
), 0.8p < f
RT
< 1.2p
(9-26f)
S
2p
R
l
sin(2q) cos(2f
RT
) £
B
E
, max
B
E
= 1 +
sinc
(9-26g)
Multiple Wind Turbines
Measurements in the vicinity of three Mod-2 wind turbines indicated that TVI effects
are enhanced when several turbines operate in
synchronism
(with blades always parallel).
The amplitude of the interference pulses produced by two synchronized turbines is about
twice that for a single wind turbine. Without synchronism, modulation pulses caused by
each machine can be identified individually and produce interference singly [Sengupta
et
al.
1983a]. For a large number of units, interferences may add randomly, but this is yet to
be verified. Assuming synchronism for our idealized cluster scatter model we obtain
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