Methods for decommission of offshore wind parks on the basis of the knowledge from the oil- and gas industry

Abstract

The decommission of offshore wind farms is a relatively new field in the renewable energy area and has yet to be fully industrialized. Through the EU-project Interreg VB North Sea Region programme and DecomTools, this thesis has had a goal of looking into the bigger picture of the decommission process of offshore wind turbines and addressing alternative approaches to methods of dismantling today. The thesis has been conducted as both literature studies of how operators and owners of today are planning to do the future decommission on existing farms, though also discussing and participating at a workshop with local offshore, subsea and decommission companies. The reverse installation has been the base case of how the operators of today´s wind farms are planning to do it, though this will (even according to them) most likely change as we are able to produce more economical and sustainable methods of removal. Alternative approaches found to the reverse installation, might be to cut of the blades by the root, plug and make the tower watertight to be able to float it thus making a towing possible. This can ease the decommission operation of several vessel days as the big heavy-lift vessels will be relieved of travelling to and from the shore dismantling-facilities several times throughout the entire operation. Additionally, findings show that we do not have any sufficient methods of recycling the composite wind turbine blades used, and that this is one of the biggest issues on how to ensure the wind turbines stay green and sustainable. Consequently, at the end of the thesis there is a selection of subjects for future research.