Research

The doctorate is carried out in cooperation with the University of Bremen, Department of Biology/Chemistry, Prof. Dr. Thomas Brey.

Title: „Multicriteria decision support and ecological assessment for sustainable decommisssioning of offshore windfarms“

Abstract: In 2020 a total of 1501 offshore wind turbines with an installed capacity of 7.7 GW operated in the German North and Baltic Sea (WindEurope 2020). In order to reach the aim of the Renewable Energy Sources Act to increase offshore wind energy production up to 20 GW until 2030 and up to 40 GM to 2040, further offshore wind farms will be built. However, at the end of their operational phase all these wind farms need to be decommissioned. Up to today only very few offshore wind farms were realising the decommissioning as well as for estimating impacts involved. Therefore, decisions on how to decommission offshore wind farms, including dismantling, offshore, harbour and onshore logistics as well as recycling, are involved with uncertainties.

This thesis aims to support relevant stakeholders (e. g. operators or the Federal Maritime and Hydrographic Agency) to develop and assess sustainable decommissioning strategies. Multi criteria decision analysis will enable developing decommissioning strategies that satisfy economic (e. g. low decommissioning costs), social (e. g. high safety at work) and ecological (e. g. maintain current biodiversity) needs. A special focus will the laid upon potential impacts on marine environment. Ecological modelling and outcomes of simulations will help to predict ecological impacts of different decommissioning strategies.

Contact: vanessa.spielmann@hs-bremen.de; silke.eckardt@hs-bremen.de

Steel pipe driven pile foundations for objects in offshore wind farms in the German Bight
Comparison of the results of dynamic pile test loads with the computational pile resistance determination

Driven Steel Tube Pile Foundations of Objects in Windfarms in the German Bight
Comparision of Results of Dynamic Load Tests with Calculated Pile Resistance

Offshore object foundations are conventionally constructed with large-diameter driven steel piles; a short-term replacement of this construction method on a relevant scale is currently not foreseeable. The setting depth of these piles is initially determined during project planning by transferring experience gained elsewhere. For this transfer, different models and calculation methods are available, which were essentially formulated on the basis of experience with smaller diameter piles. In accordance with the requirements of the approval authority, the load-bearing capacity of these deep foundations must be verified with dynamic pile test loads, which in offshore practice are mainly carried out on structural piles as end-of-driving tests accompanying the pile driving. Current project experience shows that the pile resistances determined with the existing models are partly exceeded and partly undercut by the pile test load results. Both are unfavourable with regard to an ecological and economic foundation of the object. The aim of the R&D project is to calibrate one of the existing prediction methods for axial pile resistance on the basis of a broad base of pile test load results in order to achieve a sufficiently reliable prediction of pile resistance according to geotechnical criteria.

Supervisor
Prof. Dr.-Ing. Martin Achmus
Gottfried Wilhelm Leibniz University of Hanover
Leibniz University Faculty of Civil Engineering and Geodesy
Institute for Geotechnics