VGB POWERTECH 11 (2019)

A journey through 100 years VGB | VGB POWERTECH 4 (2006)
Pumped Storage Power Plants
drops are caused by the unexpected feed in
from wind power (Figure 6, III).
Figure 6. Changes in daily load curve.
Relation wind power feed in/grid peak load in %
40
35
30
25
20
15
10
5
0
Jan Feb Mar May Apr Jun Jul Aug Sep Oct Nov Dec
Figure 7. Wind power production within the E.ON grid zone.
Figure 8. Major changes in feed in.
Example: Wind power feed in during Christmas 2004.
The Renewable Energy Act rewards the feedin
of electricity from renewable energy irrespective
of the demand and of the technical
features with special preference given to
wind power. In 2004, German consumers
spent € 2.4 billion on renewable electricity,
with this sum set to rise to € 4.3 billion in
2009 according to the DENA study. What is
inconvenient about wind is that it blows
wherever and whenever it wishes and that it
varies its strength haphazardly as well. This
means that load jumps and valleys are a matter
of course. Their stochastic nature makes it
extremely difficult to maintain a constant
grid frequency, placing extraordinarily high
demands on the quality of grid control. F i g -
ure 7 presents an overview of the variation
in wind power production in E.ON's grid
zone last year. This feed-in, which fluctuates
haphazardly to account for between 0.2% and
38% of grid peak load, poses a challenge at
least for grid operators. It would be beneficial
if electricity demand is low during wind
lulls. But the truth could not be more remote.
It is above all during extreme cold spells in
the winter and heat waves in the summer,
caused by wind lulls and stable highs that
electricity demand is especially high as the
need for electric heating and refrigeration rises.
Figure 8 shows the amount of wind power
feed-in into the grid during the Christmas
holiday last year. Wind power production
fails just when the roast goose is pushed into
millions of electric ovens, at a rate of 16 MW
per minute. Only thanks to the incredible efforts
put in by the staff in charge are millions
of households throughout Germany saved
from chaos. And this is exactly when
pumped storage plants come into play, rightfully
deemed a blessing during Christmas.
Deregulation of the
Electricity Market
Further changes were ushered in with the
electricity market's deregulation in 1998. An
interesting phenomenon witnessed in this
context is the fact that trades concluded on
exchanges and over the counter (OTC) have
an impact on the grid's physical properties
(Figure 9). They manifest themselves in
frequency jumps of 50 mHz and more, which
occur exactly once an hour. This is due to the
fact that sellers' power plants and buyers'
production facilities are not started and shut
down at the same time, resulting in a slight
timing difference leading to the observed frequency
spikes. This effect occurs especially
when power contracts expire or start and the
grid's load is relatively low (e.g. in the
evening).
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