The present paper describes the work carried out in the project ’Mooring Solutions for Large Wave Energy Converters’, which is a Danish research project carried out in a period of three years from September 2014, with the aim of reducing cost of the moorings for four wave energy converters and improving the applied design procedure. The paper presents the initial layouts and costs and illustrates which solutions could potentially reduce cost. Different methods for analysis of the systems were applied, ranging from simple quasi-static analysis to full dynamic analysis and experimental work. The numerical methods were compared to the experimental data, and results showed significant underestimation of tensions in the quasi-static model while reasonable overestimation was found in the dynamic analysis even without major tuning of the model. The dynamic analysis has then been implemented in a meta-model based optimization process with the aim of optimizing the mooring layout for each WEC according to cost of the systems.
Any ecosystem based fisheries management system is necessarily faced with the problem of multiple objectives that trade-off against one another. Typically, objectives such as the maximization of yield, employment or profit or minimizing environmental impacts will be optimized in different parts of the decision space, which is formed of the fishing mortality rates that can be applied to the various species, given the constraints imposed by the mixed species nature of many fishing fleets. Since objectives cannot be simultaneously achieved, managers need to consider how such objectives trade-off against one another in order to choose a balanced strategy. Normally, they also have to consider the views of different groupings of stakeholders, who often favour widely different and conflicting objectives. This is particularly difficult if stakeholders are reluctant to expose their negotiating positions. This article explores two possible approaches to developing a Decision Support Framework for the North Sea. The first is a classic Multi- Criteria Analysis (MCA) approach that was developed in cooperation with North Sea stakeholders. The implementation went smoothly for the definition of suitable scenarios, decision trees and criteria, but failed in facilitating consensus on how to set priorities at the stakeholder level. However, it remains a possible approach for higher level management to adopt. Consequently, to aid effective decision-making a simpler approach was designed to visualise stakeholders concerns both to themselves and to the managers in charge of actual decision-making. Rather than trying to achieve some joint optima of the objectives that stakeholders wish to achieve this approach seeks to avoid the solutions various stakeholder groups resent the most. This ‘N dimensional potato approach’ proposed here treats the decision space as analogous to a partially rotten potato that has to be prepared for the table: each group of stakeholders cut away those parts of the decision space that they consider unacceptable. Ideally, this would leave a decision space where somewhat acceptable compromise solutions exist. But, if no decision space is left after all have made their cuts, this approach will still inform managers about the consequences of different solutions in terms of which group will be disappointed and by how much. Making this approach operational requires both uncovering various stakeholders’ views of the unacceptable areas, and also displaying these areas in a convenient fashion together with areas of stakeholder consent. The article describes the steps taken to address these two tasks by the North Sea case study of the MareFrame research project.