Module B1 Study Book - the Graduate School of the Environment

Source: IEA report
• "The maximum hourly swing in output power from distributed wind
rarely, if ever, exceeds 20% of the installed capacity of the wind plant.
The standard deviation of the hourly swings is 3%. This information
is important in the context of assessing the needs for additional
reserves.
• The maximum measured change in output per minute from 2400 MW
of wind in western Denmark is about 6 MW."
Milborrow, D.J. (2001b),
A system operator might ask “What will be the output in one hour?” On the
basis of weather forecasts and modelling results, the likely output is calculated
and the operational reserve is planned accordingly. For wind penetrations of
below around 5%, wind forecasting is generally believed not to be necessary,
but as wind penetration rises, wind forecasting increasingly adds value to
wind power.
In Germany, the system reaches a prediction margin of error averaging 9% in
day-ahead forecasting, 8% for eight hours ahead, and only 2% for one hour
ahead.
One major danger cited by those doubtful about wind power is that of long
periods of still weather. Sinden (2002), shows that the longest continuous
time of calm weather in a 21-year hourly wind data set from 13 different
locations in England and Wales was 11 hours, incidentally over night at a
time of low demand.
Options for managing intermittency
Whatever is done to avoid or reduce the problem - by grid integration,
geographic and technical distribution of generators and improved weather
forecasting techniques - there will still be some residual unpredictability and
general variability, including periods where there is no wind available, which
have to be addressed.
We must not exaggerate the problem: a recent study in Germany confirmed
that the extension of wind power to some 36GW in 2015 would not require
Lecture: Britains Power System 95