E.ON Netz manages the transmission grid in Schleswig-Holstein and Lower Saxony, about a third of Germany, hosting 7,050 MW of Germany’s 16,394 MW installed wind-generating capacity at the end of 2004. The total production in their system was 11.3 TW-h in 2004, representing an average feed of 1,295 MW (18.3% of capacity).
“Wind energy is only able to replace traditional power stations to a limited extent. Their dependence on the prevailing wind conditions means that wind power has a limited load factor even when technically available. It is not possible to guarantee its use for the continual cover of electricity consumption. Consequently, traditional power stations with capacities equal to 90% of the installed wind power capacity [a little over the maximum historical wind power infeed] must be permanently online in order to guarantee power supply at all times.”
Graphs in this report (and the similar 2004 report) show that half of the time, wind power infeed is less than two-thirds of its annual average. It is greater than its annual average only a third of the time. A similar power vs. time curve applies to all wind power facilities, whether their annual average output in relation to rated capacity is higher or lower than those in Germany. The 11-turbine facility in Searsburg, Vermont, produces no power at all more than a third of the time.
“Both cold wintry periods and periods of summer heat are attributable to stable high-pressure weather systems. Low wind levels are meteorologically symptomatic of such high pressure weather systems. This means that in these periods, the contribution made by wind energy to meeting electricity consumption demand is correspondingly low. …
“The feed-in capacity can change frequently within a few hours. This is shown in the Christmas week from 20 to 26 December 2004. Whilst wind power feed-in at 9.15 am on Christmas Eve reached its maximum for the year at 6,024 MW, it fell to below 2,000 MW within only 10 hours, a difference of over 4,000 MW. This corresponds to the capacity of 8 3 500 MW coal fired power station blocks. On Boxing Day, wind power feed-in in the E.ON grid fell to below 40 MW. …
“In 2004 two major German studies investigated the size of contribution that wind farms make towards guaranteed capacity. Both studies separately came to virtually identical conclusions, that wind energy currently contributes to the secure production capacity of the system, by providing 8% of its installed capacity.
“As wind power capacity rises, the lower availability of the wind farms determines the reliability of the system as a whole to an ever increasing extent. Consequently the greater reliability of traditional power stations becomes increasingly eclipsed. As a result, the relative contribution of wind power to the guaranteed capacity of our supply system up to the year 2020 will fall continuously to around 4%. In concrete terms, this means that in 2020, with a forecast wind power capacity of over 48,000 MW, 2,000 MW of traditional power production can be replaced by these wind farms. …
“[[T]he increased use of wind power in Germany has resulted in uncontrollable fluctuations occurring on the generation side due to the random character of wind power feed-in. This significantly increases the demands placed on the control balancing process [and bringing about rising grid costs. The massive increase in the construction of new wind power plants in recent years has greatly increased the need for wind-related reserve capacity. – Wind Report 2004].”
That is, wind power construction must be accompanied by almost equal construction of new conventional power plants, which will be used very nearly as much as if the wind turbines were not there.
Also see “Wind Report 2004.”
This article is the work of the author(s) indicated. Any opinions expressed in it are not necessarily those of National Wind Watch.
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