A significant number of wind turbines will reach the end of their planned service life in the near future. A decision on lifetime extension is complex and experiences to date are limited.
This review presents the current state-of-the-art for lifetime extension of onshore wind turbines in Germany, Spain, Denmark, and the UK. Information was gathered through a literature review and 24 guideline-based interviews with key market players.
Technical, economic and legal aspects are discussed. Results indicate that end-of-life solutions will develop a significant market over the next five years. The application of updated load simulation and inspections for technical lifetime extension assessment differs between countries. A major concern is the uncertainty about future electricity spot market prices, which determine if lifetime extension is economically feasible.
The executed study revealed a lack of certainty regarding lifetime extension decision making. German interviewees see a potential for lifetime extension until 2020. However, they are sceptical what happens to the market after subsidies vanish. Lifetime extension is primarily important for sites without the ability to repower since subsidies for new wind farms remain economically attractive today. The situation is the opposite in Spain, where lifetime extension is labelled as ‘the only option’ due to a lack of incentives for new wind farms. In the UK, repowering is not considered as a viable future option due to the termination of the RO scheme, and hence wind farms which are already subsidised under the RO scheme are attractive for lifetime extension.
This leads to the conclusion that countries with favourable legal and economic conditions for repowering (e.g. profitable subsidy schemes for new wind farms, scarcity of sites, etc.) and with market prices of electricity uneconomic for small wind turbines are likely to experience less interest in lifetime extension in the next years. On the other hand, interest in lifetime extension is expected to increase in countries where conditions for new wind parks are unfavourable. Technical assessments performed for lifetime extension vary across the countries investigated. The form of assessment used is either determined by legal requirements (Germany, Denmark) or by the internal motivations of market players regarding risk management and financial planning if legal requirements are absent (Spain, UK). It is expected that there will be further consolidation of the industry towards consistent assessment methods as more guidelines are emerging.