Installation, Operation, and Maintenance Strategies to Reduce the Cost of Offshore Wind Energy

Abstract

Executive SummaryThis report is intended to provide offshore wind industry stakeholders a basis for evaluating potential cost saving installation, operation, and maintenance (IO&M) strategies and technologies. Some of the IO&M strategies in this report were analyzed without projecting the capital expenditures associated with an enabling technology or method. Thus, the results show the upside or added value to a strategy (e.g. increased energy production), and not the potential downside (e.g. added capital cost of new hardware). The results of the analysis can therefore be used by industry stakeholders to take the cost savings presented in this report and add their revised technologies costs to arrive at a net decrease or increase in cost of energy resulting from a proposed IO&M strategy. This allows many technologies that target the same improvement area to be evaluated subsequent to this study. To clarify this concept, an example is presented below.Company X is interested in bringing an innovative vessel capable of operating at higher wind and wave conditions to market. If a strategy using an innovative vessel capable of operating in higher wind and wave conditions (similar to Company X's design) is shown to reduce costs by $100/kW with respect to the baseline, Company X can see that in order to be viable in the market, they must be able to deliver their innovative vessel at a rate no more than $100/kW greater than the vessel rate used in the baseline. If Company X can deliver their innovative vessel at $25/kW more than the baseline, they will have demonstrated that their new vessel technology is capable of saving $75/kW with respect to the baseline. IntroductionIO&M is expected to account for nearly one-third of offshore wind levelized cost of energy (LCOE) in the United States (U.S. Department of Energy, 2011). Consequently, there is a large potential for reducing LCOE through advanced IO&M strategies. NREL and ECN, along with a panel of subject matter experts who provided input, have used their offshore wind cost modeling capabilities to fulfill the project's two primary objectives:• Conduct analysis and modeling to identify the most practical means of reducing offshore wind LCOE through advanced IO&M techniques, integrated service providers, and preferred supporting infrastructure.• Identify preferred IO&M strategies in a case study of a hypothetical U.S. offshore wind project. viThis report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.To accomplish the objectives related to installation costs, NREL has developed a new offshore wind turbine installation cost module which, coupled with the NREL offshore wind plant balance of station (BOS) model, is capable of analyzing many scenarios including the six (6) turbine assembly strategies and three (3) additional project installation strategies that this study analyzes.To accomplish the objectives related to O&M costs, ECN has established an O&M tool for the U.S. offshore market based on their industry-l...

Sensitivity of Risk-Based Maintenance Planning of Offshore Wind Turbine Farms

“…Recent studies show annual failure rates of offshore wind turbines in the range between 6 and 9.5 failures per year: [3]: 9.5 failures/year/turbine; [31]: 8 failures/year/turbine (without major repairs) and [37]: 6 failures/year/turbine. In this study for calibrating the damage model and the software/electrical failure rates an overall annual failure rate of 9 incidents per year is considered.…”

“…Maintenance expenses for offshore wind turbine farms contribute with 15%-30% [1][2][3] to the levelized cost of electricity. This is a large contribution and many efforts are ongoing in order to reduce these maintenance costs.…”

Strategic Maintenance Scheduling of an Offshore Wind Farm in a Deregulated Power System

“…The estimates for offshore wind show large and rapid growth where offshore is expected to produce about 10% of the global installed capacity by 2020 [1] from the first offshore wind farm (OWF) at Vindeby, Denmark in 1991. Operation and maintenance (O&M) costs of an OWF are high, and O&M costs can reach up to 30% of the total cost [2,3], where they have reached up to 23% in some European offshore farms [4]. Moreover, if the farm is located at remote offshore areas, its availability can reduce down to 70%, as the vessel accessibility decreases [5].…”

Dynamic response mitigation of floating wind turbine platforms using tuned liquid column dampers

“…However, a TLP is not constrained dynamically in the horizontal direction and the drift motions (surge, sway and yaw motion) of the platform due to the action of coupled wind-wave forces can be significant during extreme weather conditions [3][4][5]. These motions can influence the performance of a wind turbine, the accessibility during its operation and maintenance (O&M) and ultimately the levelized cost of energy (LCOE) [6,7]. Incorporation of damping devices to the structure has been suggested to reduce these types of responses [2,[8][9][10].…”