Financing for wind farms: making consistent use of empirical values
Words: Thomas Arnold and Thomas Zirngibl, TÜV SÜD Industrie Service GmbH
The recently revised TR6 Technical Guideline of the German Public Association of the Renewable Energy Sector (Fördergesellschaft Windenergie (FGW)) is designed to ensure the provision of reliable yield forecasts. Wind reports based on the Guideline play a critical role for producing reliable estimates of the profitability of a wind-farm project. In the past, turbines have often been shown to deliver lower energy levels than their reported estimates. The ninth revision of TR 6 now specifies methods that will help to produce realistic forecasts of actual on-site wind conditions.
Wind speed and direction at the proposed site of a wind farm are critical factors in determining whether wind farm operation will be cost-effective over the long term. Previous practice has shown that measurements and evaluations of wind and weather data may be over-optimistic, favouring the stakeholders’ own interests. At least two wind reports issued by third-party organisations are therefore necessary to convince banks and investors of the profitability of a wind-farm project in order to secure financing.
Independent accredited assessors are therefore commissioned to verify the yield forecast of a planned project. As these forecasts are always based on varying project-specific facts, figures and data, their evaluation involves some key questions: What is the quality of the available input data? What measurements were performed at the site, and over what period? Is that period representative, allowing conclusions to be drawn regarding annual yields and forecasts to be prepared for twenty years of operation? Are wind energy turbines already in operation there, and can they be used to validate the model? What methods of analysis were used in evaluation? All in all, assessors must establish whether the information about the project, the future site and its environs is sufficient to allow a realistic yield forecast to be drawn up.