Environmental Engineering Reference
In-Depth Information
DE
DK
ES
F
GR
IR
IT
NL
P
UK
Capacity credit/rated power
0.4
0.3
0.2
0.1
0
2
4
6
8
10
12
14
16
Energy penetration, %
Figure 7.11 Comparison of results from ten utility studies of capacity credit, though assumptions
differ. (Courtesy of David Milborrow)
Capacity credit/annual capacity factor
1.6
1.4
NGC
1.2
SCAR
1
CEGB
0.8
0.6
0.4
0
5
10
15
20
25
Wind energy contribution, %
Figure 7.12 Normalized values of capacity credit from three studies of the NGC system. (Courtesy
of David Milborrow)
wind energy the capacity credits are about 40% greater than the annual capacity factor and
therefore, if the average capacity factor across the country was 35%, then 1000 MW of wind
would displace 490 MW of thermal plant. At higher wind energy penetrations the capacity
credit declines due to the requirement for more part-loaded generation plant to cover for
uncertainties in wind power generation.
No evidence appears to exist to demonstrate that the conclusions set out above are inac-
curate. Although there are periods of calm during the summer, the loss of load probability at
such times is low. The nonavailability of wind during such periods therefore makes little
difference to the year-round probability. It may be noted that the capacity credit of solar plant
 
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