Mooring line fatigue damage evaluation for floating marine energy converters: Field measurements and prediction

publication-status: Publishedtypes: ArticleThe vision of large-scale commercial arrays of floating marine energy converters (MECs) necessitates the robust, yet cost-effective engineering of devices. Given the continuous environmental loading, fatigue has been iden- tified as one of the key engineering challenges. In particular the mooring sys- tem which warrants the station-keeping of such devices is subject to highly cyclic, non-linear load conditions, mainly induced by the incident waves. To ensure the integrity of the mooring system the lifecycle fatigue spec- trum must be predicted in order to compare the expected fatigue damage against the design limits. The fatigue design of components is commonly as- sessed through numerical modelling of representative load cases. However, for new applications such as floating marine energy converters numerical models are often scantily validated. This paper describes an approach where load measurements from large- scale field trials at the South West Mooring Testing Facility (SWMTF) are used to calculate and predict the fatigue damage. The described procedure employs a Rainflow cycle analysis in conjunction with the Palmgren-Miner rule to estimate the accumulated damage for the deployment periods and individual sea states. This approach allows an accurate fatigue assessment and prediction of mooring lines at a design stage, where field trial load measurements and wave climate information of potential installation sites are available. The mooring design can thus be optimised regarding its fatigue life and costly safety factors can be reduced. The proposed method also assists in monitoring and assessing the fatigue life during deployment periods

Comparing nuclear power trajectories in Germany and the UK: from ‘regimes' to ‘democracies’ in sociotechnical transitions and Discontinuities

This paper focuses on arguably the single most striking contrast in contemporary major energy politics in Europe (and even the developed world as a whole): the starkly differing civil nuclear policies of Germany and the UK. Germany is seeking entirely to phase out nuclear power by 2022. Yet the UK advocates a ‘nuclear renaissance’, promoting the most ambitious new nuclear construction programme in Western Europe.Here,this paper poses a simple yet quite fundamental question: what are the particular divergent conditions most strongly implicated in the contrasting developments in these two countries. With nuclear playing such an iconic role in historical discussions over technological continuity and transformation, answering this may assist in wider understandings of sociotechnical incumbency and discontinuity in the burgeoning field of‘sustainability transitions’. To this end, an ‘abductive’ approach is taken: deploying nine potentially relevant criteria for understanding the different directions pursued in Germany and the UK. Together constituted by 30 parameters spanning literatures related to socio-technical regimes in general as well as nuclear technology in particular, the criteria are divided into those that are ‘internal’ and ‘external’ to the ‘focal regime configuration’ of nuclear power and associated ‘challenger technologies’ like renewables. It is ‘internal’ criteria that are emphasised in conventional sociotechnical regime theory, with ‘external’ criteria relatively less well explored. Asking under each criterion whether attempted discontinuation of nuclear power would be more likely in Germany or the UK, a clear picture emerges. ‘Internal’ criteria suggest attempted nuclear discontinuation should be more likely in the UK than in Germany– the reverse of what is occurring. ‘External’ criteria are more aligned with observed dynamics –especially those relating to military nuclear commitments and broader ‘qualities of democracy’. Despite many differences of framing concerning exactly what constitutes ‘democracy’, a rich political science literature on this point is unanimous in characterising Germany more positively than the UK. Although based only on a single case,a potentially important question is nonetheless raised as to whether sociotechnical regime theory might usefully give greater attention to the general importance of various aspects of democracy in constituting conditions for significant technological discontinuities and transformations. If so, the policy implications are significant. A number of important areas are identified for future research, including the roles of diverse understandings and specific aspects of democracy and the particular relevance of military nuclear commitments– whose under-discussion in civil nuclear policy literatures raises its own questions of democratic accountability

Feasibility of investment in Blue Growth multiple-use of space and multi-use platform projects; results of a novel assessment approach and case studies

Highlights• A comprehensive history of multiple use of space blue growth.• New metrics for comparing salmon to megawatts are presented.• Method and criteria for ranking potential investments in blue growth business models.• Profitable case studies described involving electricity, water, mussels and fish.Blue Growth is the creation of economic activity and jobs at sea, while multiple use of space makes efficient use of the available sea area by combining industries. Clearly there are many combinations and many value propositions. However, most technologies to date are considered blue sky concepts, with little robust techno-economic analysis demonstrating profitability.AbstractThe paper begins by providing a comprehensive review of Blue Growth and multi-use in Blue Growth; both in policy as well as the wide range of current technologies, including ocean energy, offshore wind energy, offshore aquaculture and desalination.The Maribe H2020 project provides the vehicle for the research element of the paper. The major contribution is a new methodology for selecting, filtering, developing and ranking business propositions for multiple-use of space (MUS) and multi-use platforms (MUP). Application of the method for the first time identified three case studies where Blue Growth combination projects can be economically viable, with attractive internal rate of return (IRRs). Results presented for the case studies report standard investment metrics and show the relative contribution of each product (energy, food, water) to the system profitability, as well as socio-economic impact. Existing companies were fully engaged in the process. Co-creation between sector experts and industry led to both improved business value propositions and robust assessment of investment readiness. In contrast to the presumption that large scale platforms are commercially attractive, the highest ranking case study companies required smaller capital expenditure (CAPEX) and operated in niche subsectors.In conclusion, the positive economic performance of the case studies should provide confidence for the EC as well as investors that MUS and MUP have viable economic futures leading towards commercialisation. The macro and micro assessment methods will be particularly useful in other Blue Economy contexts and in other multiple product contexts

Operation and Maintenance Modelling

Operational expenditure (OPEX) is one of the major contributors to the levelized cost of energy (LCoE) for offshore wind farms. To assess different solutions and select the best ones, good models for maintenance and logistics decision support are required. This chapter provides an overview of, and a brief introduction to, operation and maintenance (O&M) modelling for offshore wind farms, including transport and logistics for O&M. It provides an overview of O&M modelling for offshore wind farms. The primary focus is on the application of offshore wind O&M models for decision support. An overview of the current status in O&M modelling for offshore wind farms is presented. The chapter focuses is first on strategic O&M simulation models, and discusses models for selected optimization problems. It outlines the general differences between optimization and simulation models. The decision support tools and concepts developed in NOWITECH and related projects include models on both the strategic, tactical and operational leve