Dr. Magdalena Kurkowska

Wind turbines are typically designed for a 20 years services life. In fact, many of them remain operational beyond this age. Industry experts believe, if carefully planned, the life of a wind farm can be extended even up to 40 years. Such an extension can increase assets value, maximize the revenue and reduce the Levelized cost of energy. In practice, the lifetime of the wind power project is most often determined by the length of the subsidy scheme which usually lasts 15 years.

Life extension may generate much less regulatory and permitting hurdles than repowering, which in many markets involves reapplying for a permit to operate.

Beyond that point, the decision what to do with the end-of-life assets must be carefully weighted. Dismantling and disposing of functional turbines does not sound like a good business practice, but on the other hand turbine components, as their age, are becoming increasingly failure-prone, resulting in high O&M costs, greater risks of structural failures, and associated health & safety hazards. How to minimize these risks and keep the project going? Lifeextension can be the answer. wind-farm-lifecycle.iqpc.de With the ageing fleet, an increasing number of wind farm operators face a dilemma which end-of-life strategy to pursuit. Can life-extension be the optimal option? What are the pros and cons? What is the market opportunity for life extension programs? What approaches can be taken to assess the suitability of wind farm for life extension?

In prequalification tests, commonly used standards are generally based on laboratory testing procedures, and it is important to know that these test procedures cannot often determine the true corrosion prevention potential of a coating system. No overall laboratory test exists which considers all the different stresses and includes the appropriate acceleration factor in order to relate an accurate number of hours in an accelerated test to lifetime in years in real file. Within a structure erected in a maritime environment (sheet pile walls, oil platforms or wind energy structures), there are generally different zones with different intensities of corrosive attack: bottom or sea floor, immersion and low water zone, tidal and splash zone and last but not least, the atmospheric zone. Therefore, it is necessary to consider different intensities of corrosion in any test procedure to be developed or applied.

Furthermore, a continuous mechanical stress from waves, floating matter and ice movement in winter that can attack coatings, and coatings also commonly suffer from mechanical impact during transport and erection, which can lead to localized damage and coating detachment.

Life extension exposes operators to lower risks than repowering, but there are also drawbacks. Replacing single components rather than full repowering seems to deliver less added value.

The study, conducted by National Renewable Energy Laboratory, Denver, Colorado, compared two scenarios: the full repowering versus replacement of the turbine drivetrain and rotor only using an existing tower and foundation.

Until recently, due to generous subsidies, market seemed to favor repowering over life extension. This trend, however, may change in the near future. As the governments gradually lessen or completely withdraws support for wind power projects, the life-extension option becomes increasingly attractive. A shift from repowering toward life extension was observed in Spain in 2013, when the government removed the feed-in-tariffs (FiT) support for wind energy developments.

Under a new scheme, the generators are offered 7.5% rate of return calculated over the plant lifetime. Many older wind farms have already received such amount through FiT and were not eligible for any further subsidies.

This change has left operators relying entirely on the sales of produced energy for their income, typically insufficient to allow investing in full repowering. Life extension can be achieved at a fraction of the cost the full repowering demands. Replacing a rotor hub or blades will obviously cost less than replacing the entire turbine structure. At present, the cost of extending the life of an operating turbine in Europe is about 100,000/MW comparing to one million for a new turbine required for repowering.

Moreover, life extension may generate much less regulatory and permitting hurdles than repowering, which in many markets involves reapplying for a permit to operate.

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A business case for wind farm lifetime extension - Windpower Engineering (press release)