MSc forsvar Kathrin Anne Merten

Supervisor: Niels-Erik Clausen, DTU Wind Energy

Co-supervisor: Ole West, Ørsted

Examiner: Peter Vangsø Jeberg, Energinet

Title: Decision criteria for late-life strategies of offshore wind farms – lifetime extension evaluation
An increasing number of countries have been and are focusing on renewable energy technologies and especially offshore wind gains importance since its role in Europe’s electricity mix is constantly rising [1]. Already today, there are 18.3 GW (end of 2018 [1]) of offshore wind installed in Europe alone and with the European Commission’s goal to install between 290 and 450 GW of offshore wind in Europe by 2050, offshore wind capacity is expected to increase heavily. The first installed commercial-scale offshore wind farms will reach the end of their design lifetime within the next decade.

Consequently, it is important for companies to analyse the late-life period of their assets and assess if it is worthwhile to maintain the wind turbines and implement a lifetime extension strategy or proceed otherwise (decommissioning, repowering).

A generic decision tree has been developed in order to perform a high-level analysis aiming towards a strategic end of life decision. Furthermore, an economic assessment model has been developed to analyse whether a lifetime extension project is feasible and worthwhile to undertake. For such a decision, different factors have to be taken into account. Firstly, regulatory requirements need to be considered to determine if further site and project operation is allowed or not. Additional factors to be considered are failure rate developments and major components as well as structural integrity. Remaining lifetime, cost for major component exchanges, performance and power price developments have to be taken into account to assess if a major component exchange is necessary and possible. In parallel to component modelling is the economic assessment of lifetime extension. Such a project can be considered as feasible as long as revenues are higher than cost. This assessment is done by using a model, taking different input parameters such as different OPEX scenarios, power price scenarios as well as initial lifetime extension investment scenarios into account and discussing their connection.

To validate the model, two case studies have been performed. One for Nysted, a Danish offshore wind farm and one for Barrow, a British offshore wind farm. Two wind farms located in different countries have been selected in order to compare different market conditions, power price developments, OPEX developments and regulatory requirements and assess the validity of different assumptions. Based on these case studies, it can be concluded that lifetime extension is feasible for the majority of the tested cases for the two case studies and is thus a promising source of additional income for wind farm owners. It offers opportunities to increase revenues while also making sense from a sustainability perspective. Additionally, decommissioning cost are pushed further to the future, having a positive impact on the NPV and the levelised cost of electricity (LCOE) decreases as well when the lifetime is extended.


man 03 feb 20
10:00 - 12:00



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