Wind Energy

46 E. Bibor and C. Masson
% error (Psect - Pgen) / Pgen
15
10
5
0
−5
−10
−15
4
5 6 7 8 9 10
V ∞ - bins of 0.5(m/s)
11 12
Fig. 8.2. Comparison between correlations by sectors and general correlation for
all valid sectors on power curves
(a) (b)
V ∞ (m/s)
20
18
16
14
12
10
8
6
4
2
0
0
+
+
+
+
2 4 6
+
+
+
+
+
+
+
+
+
+
+
+
8 10 12 14 16 18 20 22
V nac (m/s)
+
+
+
+
+
+
+
Experimental: general
correlation
Numerical - without U
Numerical - with U1
Numerical - with U2
Fig. 8.3. (a) Attachment unit on the nacelle (b) Influence of the attachment unit
positions, U1 and U2, distant of 50 cm, have been analysed (Fig. 8.3b). The
influence of the U-beam is significant, and can explain in part the differences
observed between the numerical and experimental correlations.
8.6 Conclusion
Three main conclusions were drawn from experimental and numerical analysis.
First, using the correlation provided by the manufacturer for any type of
terrain can lead to important error. The second conclusion is that the use of
a general correlation for all the valid sectors is not a bad practice. Finally,
it has been numerically proven that for this WT, the attachment unit of the
nacelle anemometer is an important cause of the flow perturbation.