Innovative decommissioning and upgrading concepts for offshore wind farms

The purpose of this thesis is to evaluate the end-of-life alternatives for offshore wind farms through a comprehensive analysis of costs. Important costs such as capital and operational expenditure will be considered. The thesis will evaluate the end-of-life scenarios; decommissioning, lifetime extension and repowering of offshore wind farms for both fixed bottom and floating structures. The offshore wind industry is relatively new and the market for end-of-life alternatives is still under development. However, the installation of offshore wind farms is increasing, thus decommissioning, lifetime extension and repowering will become important topics for the industry. I

The demand for more renewable and sustainable energy is rapidly growing. The enormous energy potential related to offshore wind, could potentially meet the increased global demand. In the period from year 2030 to 2040, roughly 20,000 wind turbines in Europe will reach the end of their service life. It is therefore urgent to assess the end-of-life alternatives for both fixed and floating offshore wind farms.

This thesis presents a comparison of the levelised cost of energy (LCOE) for different end-of life alternatives for offshore wind farms. Two case-studies with two offshore wind farms; one with bottom-fixed foundations and one with floating foundations, have been examined for the following alternatives: decommissioning after 20 years, lifetime extension from 20 to 25 years, and innovative integration of early decommissioning and repowering.

The commercial offshore wind farms have been assessed by means of life-cycle cost analyses.It was revealed that both lifetime extension and repowering of a floating offshore wind farmwould require a large capital expenditure.

Overall, cost reductions will be possible for the following generations of offshore windturbines, due to advancements in technology, manufacturing processes and a further developed market.

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Innovative decommissioning and upgrading concepts for offshore wind farms