Testing the robustness of optimal access vessel fleet selection for operation and maintenance of offshore wind farms

Abstract

Optimising the operation and maintenance (O&M) and logistics strategy of offshore wind farms implies the decision problem of selecting the vessel fleet for O&M. Different strategic decision support tools can be applied to this problem, but much uncertainty remains regarding both input data and modelling assumptions. This paper aims to investigate and ultimately reduce this uncertainty by comparing four simulation tools, one mathematical optimisation tool and one analytic spreadsheet-based tool applied to select the O&M access vessel fleet that minimizes the total O&M cost of a reference wind farm. The comparison shows that the tools generally agree on the optimal vessel fleet, but only partially agree on the relative ranking of the different vessel fleets in terms of total O&M cost. The robustness of the vessel fleet selection to various input data assumptions was tested, and the ranking was found to be particularly sensitive to the vessels’ limiting significant wave height for turbine access. This is also the parameter with the greatest discrepancy between the tools, implying that accurate quantification and modelling of this parameter is crucial. The ranking is moderately sensitive to turbine failure rates and vessel day rates but less sensitive to electricity price and vessel transit speed

Maintenance optimization and inspection planning of wind energy assets: Models, methods and strategies

“…Then, the full text of each work was carefully reviewed to eliminate those that were not related to the field of -optimization‖ or -scheduling‖. Finally, two hundred and forty-six publications including one hundred and seventy-nine journal articles , thirty-seven master and doctoral dissertations , twelve textbooks [224][225][226][227][228][229][230][231][232][233][234][235], and eighteen industrial reports [236][237][238][239][240][241][242][243][244][245][246][247][248][249][250][251][252][253] were selected for their relevance to the topic. Figure 3 represents a bar chart of number of publications concerning maintenance policy optimization and inspection planning of wind turbine systems in five-year periods, from 1997 to 2001, 2002 to 2006, 2007 to 2011, and 2012 As can be seen, over 72% of the publications have appeared during last five years which indicates the increasing importance of the maintenance optimization in wind energy industry.…”

A review of asset management literature on multi-asset systems

“…Moreover, existing studies deal with only one objective and readily assume asset independence in their models. Azam et al [155] formulated a helicopter fleet selection model with a single objective to maximise the mission reliability, while Sperstad [156] developed a decision support tool that optimises operation and maintenance costs using a case study of vessel fleet selection in offshore wind farms. In single-category portfolios, an organisation can consider only common criteria that can be applied to any asset in the system.…”

Operation and Maintenance Modelling

“…In this way, the collaboration has aided model development and verification and has contributed to increased understanding and confidence in the modelling of offshore wind O&M. The reference data set has also been used as a starting point for a more detailed data set and LCoE calculation involving multiple OPEX and CAPEX models (Smart et al, 2016). Building on the work and the reference data set, the offshore wind O&M modelling group has also carried out a comparison and benchmarking of O&M models as applied as decision support tools for O&M vessel fleet selection (Sperstad et al, 2016b). The main contribution of this work is to show that the uncertainties associated with such decision support are still considerable, implying that decision makers should use such tools with caution and not rely upon solutions from a single decision support tool.…”

“…The case study is based on Sperstad et al (2016b), which, in turn, is based on the offshore wind reference data set published in Dinwoodie et al (2015). Here, a reference wind farm is defined to consist of 80 3-MW wind turbines at an offshore location with given metocean conditions and a distance of 50 km from an onshore maintenance base.…”