Top-Class Yield Assessments Reduce Risks for Investors

UL-DEWI-Group presents new services at WindEnergy Hamburg

The new 120 meter measuring mast on the test field in Wilhelmshaven was set up for research purposes and for verifying long-range sensor systems. Photo: UL DEWI

Wilhelmshaven, 27 September 2016 – Starting in 2017, tendering procedures will replace the fixed feed-in tariffs previously used for wind power installations in Germany. Since the tender will in future go to the lowest bidder, investors will have to be able to assess their location as accurately as possible before bidding. By providing top-class power yield assessments and wind measurements, UL-DEWI (UL International GmbH) minimizes the risks for investors. The company will be presenting the extension of the service life of wind turbines as a new service to an international audience at the WindEnergy Hamburg from 27 to 30 September (Hall 1, Booth 131).

While the tendering procedure will offer investors in Germany new opportunities, it will also bring financial risks with it. With over 25 years' experience as a service provider and research institution, UL-DEWI will support investors with its expertise during this complex system changeover. In order to encourage competition, politicians are relying on an auction model in which the lowest bidder wins. Payment will be made over a twenty-year period using a single-stage model.

Site quality will determine the payment

An important factor from 2017 will be verification of the site quality. This will be determined in accordance with the technical guidelines of the Fördergesellschaft Wind, and only accredited institutions such as UL-DEWI will be permitted to perform the corresponding calculations. Verification of the quality of a site is based on the assessment of the wind potential and power yield over a period of 20 years. This assessment must be submitted to the grid operator before commissioning and also represents an important basis for the preparation of a bid. The previously assessed site quality will be compared to the actual amount of energy fed into the grid after 5, 10 and 15 years. Deviations of more than two percent will be adjusted either up or down. For investors, this will either mean back payments or even decreasing remunerations and reimbursements to the grid operator, which would also have to bear interest.

In determining the quality of the location, the usual uncertainties in wind measurements and power yield assessments are not taken into account. "These changes inevitably increase the pressure on wind measurements and power yield assessments to minimize the uncertainties beforehand and to make it possible to determine the site quality as realistically as possible. This is of decisive importance not only for preparing the bid but for the profitability and financing of a site", said Till Schorer, Manager at UL-DEWI. The company is a leading wind surveyor accredited in accordance with international and national standards with over 400 wind measurements and 4,000 yield assessments under its belt. Its range of services includes top-class power yield assessments, wind measurements and verifications of quality for new sites.

From 2017, this verification will be the admission ticket to the wind power market. Based on the yield assessments, all players will have to bid on a fictitious 100 percent reference location, to ensure their bids are comparable. The actual quality factors for the real projects lie within a range of 70 to 150 percent of the reference yield. Using the site quality verification and predetermined correction factors, grid operators then calculate the remuneration. After five years, specialists then compare the actual feed-in with the site quality for the first time. Schorer expects that it will be necessary to adjust the feed-in remuneration multiple times. Statistics over many years show variations in the incidence of wind of between 2.3% and 5% and the uncertainties of power yield assessments lie somewhere between 10% and 18%. In addition, the down-times of the installations are included in the calculations after five, ten and fifteen years. A technical availability of 98 % per turbine is the accepted limit. Inferior values will have to be shouldered by the operator in the future because they are correspondingly offset against the amount of power actually fed into the grid. "With our specialist experience, we undertake the assessment of high-resolution operating data and the prescribed testing. Nevertheless, operators and investors should have the actual results within the first five years so that they can avoid any nasty surprises", Schorer said.

New measuring mast on the test field

UL-DEWI has its own equipment ready to use for any wind measurements which may be necessary. These include LiDAR (light detection and ranging) units, which are approved as long-distance sensing systems for supplementary or complete measurements in accordance with international standards. The advantage of mobile LiDAR units is that no building permit is required and the wind profile is recorded at great heights. That is an important factor. In the EEG 2017, policymakers are giving installations with a nacelle height of at least 135 meters preferential treatment over smaller turbines. At the same time however, there is scarcely any reliable data on wind profiles at these heights.

For verification of the remote sensing systems, UL-DEWI has set up a new 120-metre measuring mast on the test field at Wilhelmshaven with calibrated sensors. In campaigns lasting several weeks, wind speeds will be measured at different heights on the mast and by LiDAR, and the results will then be correlated. Verification of the LiDAR units is required by the current guidelines in order to be able to determine any deviations from the sensors on the measuring mast precisely and to deliver LiDAR measurement results that are reproducible and usable. This verification is also offered by UL-DEWI as an external service.

Inspection station for longer service life

Profitability is something that also concerns investors in wind farms already in operation. In Spain, for example, market participants are faced with the problem that the feed-in remunerations have been cut retrospectively. In other countries, such as France, feed-in payments are only guaranteed for a maximum of 15 years. This is why operators are turning to life time extension (LTE) to increase the service life beyond the usual technical service life of 20 years. UL-DEWI has positioned itself to work in this sector with an inspection facility in Spain that is accredited in accordance with DIN EN ISO/IEC 17020. This enables the specialists to work in interesting markets throughout Europe. The experts assess the potential remaining service life by inspecting the installations, evaluating the operating data and using a model. With this practical and analytical method, the company determines the loads that a turbine could theoretically withstand at a specific location based on its design and the loads to which it has actually been exposed. The load reserves of the material in months and years for continued safe operation are calculated using the difference between these two values.

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