offshore grids for wind power integration - Greenpeace

discussion and conclusions
“ADDING UP THE POWER GENERATION FROM WIND FARMS OVER LARGER REGIONS CAN REDUCE THE PERIODS OF VERY LOW LOAD.”
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© GREENPEACE/GILLBERG
image AN OFFSHORE WIND FARM OUTSIDE COPENHAGEN, DENMARK.
6.1 availability and variability
characteristics of offshore wind power generation
The availability of power from offshore wind farms can be
characterized by the duration curve of wind power generation.The
shape of the load duration curve depends on the local wind climate.
On the one hand, for a single offshore wind farm there is typically a
significant period during which it is generating at its maximum
(rated) capacity (here set to 89% of installed capacity). In the
cases under examination this is approximately during 10% of the
time. On the other hand, a single wind farm will experience periods
of very low load, in the North Sea up to another 10% of the time.
Adding up the power generation from wind farms over larger
regions can reduce the periods of very low load. When the
geographical area of the North Sea is considered there is always
some power generated. Adding up the generation from offshore
wind farms over large regions also leads to a larger amount of
power generated at medium and low power levels in exchange for a
reduction of periods of full and very low load.
The variability of the offshore wind power generation can be
characterized by means of histograms or cumulative frequency
distributions of the power variation. Hourly power variations from a
single wind farm mostly do not exceed ±2% of installed capacity.
The occurrence of variations beyond 10% is negligible.
With regard to unit commitment and dispatch of the power system,
this means that the target should not be entirely smoothing out the
variability of offshore wind power in the North Sea alone. Wind
power should rather be seen as one source within a power generation
portfolio that, as a whole, has to be managed in order to supply the
variable demand.Today, wind power is well complemented by
generation from reservoir hydro power plants and CCGT. In the
future, other renewables and demand-side management may fulfil
part of this task as well. Day-ahead and intra-day forecasting of the
wind power generation is required for optimal dispatch decisions and
minimization of reserve requirements.
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