Environmental Engineering Reference
In-Depth Information
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0
1 May 2004
2 May 2004
3 May 2004
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7 May 2004
Figure 3.16
Wind farm forecast ( +1 hour) versus actual output, Ireland, 2004. (Reproduced with
permission of Garrad Hassan and Partners Ltd)
3.5.5 Impact on Reliability
[6]
In addition to the operating reserve, some system margin in excess of the system peak demand
is required and this will be affected by the level of wind penetration. The example of a power
system with a peak demand of 70 GW will be given, [6]. To guarantee long term security to
an accepted level of reliability utilities in general would require that about 20% (14 GW) of
that peak must be additionally available on the network as the system margin. The system in
question has a yearly energy demand of 350 TW h. If 10% of the system energy were to be
generated by wind power it is possible to assess what the new plant margin should be. To
generate 10% of the energy, i.e. 35 TW h, a wind power capacity of 35 000/(8736
0.3) =
13 GW, where 8736 is the number of hours in the year and 0.3 is the average wind farm
capacity factor. The 35 TW h would be generated by 35 000/(8736
×
0.75) = 5.3 GW of con-
ventional generation with a yearly load factor of 0.75. Ideally the wind plant would directly
substitute for this conventional plant, but the variability of wind power means that not all of
this conventional plant can be removed from the network. Statistical calculations by utilities
indicate that 81 GW of conventional plant would be required to meet the same level of reli-
ability. Therefore only 3 GW (84
×
−
81 GW) can be removed from the network; i.e. 2.3 GW
(5.3
3 GW) is retained because of wind power variability, which is 17% of the wind power
installed capacity.
In the UK context of a planned 20% penetration from wind and to maintain system reli-
ability the associated cost lies within 0.03 and 0.05 p/kW h.
−
3.5.6 Discarded/Curtailed Energy
As the capacity of the variable sources injected into a system increases, there might be occa-
sions when the available power from such sources cannot be used. If the penetration is sub-
