Feed Laws

Large Wind Turbines

June 20, 2003
Paul Gipe

Windenergie Report Deutschland 2002


The following article appeared in an edited form in Renewable Energy World's July—August 2003 (Vol. 6 No.4) issue.

Windenergie Report Deutschland 2002 by Institut für Solare Energieversorgungstechnik (ISET) in Kassel is the continuation of a series of practical reports on the operation and performance of wind turbines in Germany. The annual reports for the Scientific Measurement and Evaluation Program, or WMEP for its German acronym, will continue at least into 2004.

In 2001, German wind turbines generated 10.3 TWh, providing 2.3% of the country's electricity, says ISET. That's not the whole story. In windy Schleswig-Holstein wind turbines generated 2.4 TWh, contributing 19% of electricity supply in the state. In the former east German state of Mecklingburg-Vorpommern, wind turbines produced nearly 800 million kWh for 13% of the states consumption. And turbines in the German state of Niedersachsen delivered 3.4 TWh to the grid--as much wind-generated electricity as produced in the entire state of California. Wind supplied 7.5 of the electricity in Niedersachsen in 2001.

Reflecting the relatively modest wind resource in Germany as well as the number of older turbines in the existing fleet, average specific yields are less than those seen in more recent projects at energetic sites. In the windiest state, Schleswig-Holstein, turbines delivered little more than 600 kWh/m2 in 2001, less than the annual average since reporting began in 1992 of more than 750 kWh/m2. Some turbines produced nearly 900 kWh/m2 in 2001, but some fell well below 500 kWh/m2 as well.

Readers may be surprised to find that Germany has a large database of experience with icing. As ISET explains, increasing numbers of turbines are being installed in the interior highlands of the country where icing is common during the winter months. Not only do wind turbines in the interior experience more icing events than turbines along the North Sea, the duration of each event is four times as long.

As one would expect, wind turbines at windier sites along the coast of Schleswig-Holstein deliver more full load hours, than those operating in Bavaria in the Alpine foothills: 1,800 hours, compared to 900 hours. Full-load hours are the German measure for performance and relate to capacity or plant factor.

Of importance, despite utility fears of dangerous fluctuations in power from wind turbines as weather systems moved across a region ISET could find no more than a 20% fluctuation of installed rated power and that had an probability of occurrence of only 0.01%.

Average availability continues at 98% and above for turbines in the WMEP program where the average age is eight years. Accordingly, ISET reports that the average downtime for the year was only six days.

As in previous reports, ISET has not yet detected any age related fatigue failures among the older turbines in the WMEP program.

ISET estimates that the average cost of operation and maintenance of among the turbines it monitors varies from 10 Euros/kW to 35 Euros/kWh of installed capacity. Interesting, ISET found that the maintenance costs of turbines up to 250 kW were higher than those of turbines greater than 500 kW.

Like their Danish colleagues at BTM-Consult, ISET concludes that the success of the German market has been due to fixed-price tariffs. This is most notable, says ISET, when German wind development, and its manufacturing sector, are compared to Great Britain and Ireland. While the wind resources in Great Britain and Ireland are significantly greater than those in Germany, the support mechanism has been far less successful at stimulating wind development.

Wind turbines in Germany are connected to the grids of more than 150 electric utilities.

Germany operates more megawatt scale wind turbines than any other country. There are now more than 3,500 wind turbines operating in Germany greater than 1 MW. Another 5,400 turbines in the 500-kW to 1-MW class were operating in 2001.

The percentage of the market for stall-controlled turbines is falling dramatically. In 1994, stall-controlled turbines accounted for more than half the German market, but by 2001, only 30%. Wind turbines using variable pitch and operating at variable speed represented almost two-thirds of all German turbines.

As in past years, Enercon dominates the German market with 28% of total capacity installed in 2001. Enercon is followed by Vestas with 20% of the market and then NEG-Micon with 12% and Enron Wind (now GE Wind) with 11%.

ISET's WMEP report offers a simple summary of Germany's new electricity feed law, the Erneuerbare-Energien-Gesetz (EEG). Turbines installed before the end of 2001 will earn 9.1 Euro cents per kilowatt-hour for five years. After that period, payment is reduced using what Germans call the "reference yield model." This method of determining payment is also called "advanced renewable energy feed-in tariffs" and a similar program has been adopted in France. Turbines that produce the "reference yield" spelled out in the new law will receive 6.2 Euro cents/kWh for the remaining 15 years. Turbines at less windy sites will receive slightly more per kWh.

The EEG also stipulates that each succeeding year, newly installed turbines will receive 1.5% less than those installed the year before. Turbines installed in 2002 will receive 9.0 Euro cents/kWh for the first five years. Those installed in 2003 will receive 8.79 Euro cents/kWh, and so on.

Now, if the wind industry could just convince the Spanish, the Americans, and the Indians to collect as detailed and thorough records as found in the WMEP, wind energy advocates would have access to all the data they would ever need to justify further expansion of the technology.

English language charts and data from the WMEP program is available on the web at The full report can also be ordered directly from the web site.

ISET's WMEP 2002 report offers 298 pages of valuable data from the world's most comprehensive wind turbine monitoring program. Copies can be purchased for 15 Euros plus postage from ISET, Königstor 59, D34119 Kassel, Germany; +49 561 72940; fax: +49 561 7294 100; mboxspam @ spamiset.uni-kasselspam . spamde;

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