Decision Models for Operation and Maintenance of Offshore Wind Farms Considering Uncertainties

  • Author / Creator
  • Wind energy is an important renewable resource to meet the continually increasing global energy demand. The high wind power potential in the sea has led to the development of wind farms in the sea, referred to as offshore wind farms (OWFs). OWFs are an array of wind turbines built in the sea to generate electricity from the abundant wind energy in the sea. In addition to high productivity, OWFs do not produce any noise pollution to human life and do not affect wildlife (especially birds). These advantages have made OWFs, a reliable renewable option to meet future energy demand through green energy.

    On the downside, the cost of energy produced by OWFs is high when compared to the cost of energy from wind farms in the land. Almost one-third of the cost of energy produced by OWFs is due to operation and maintenance (O&M) activities and is twice expensive as the wind farms in the land. The high O&M cost of OWFs is mainly due to its operating environment. The marine environment affects the reliability of offshore wind turbines (OWTs), creates uncertainty in turbine component lifetimes, and thereby increases the number of maintenance activities, effort, and costs. Also, the uncertain weather conditions and sea-state conditions limit accessibility to OWF for maintenance activities and increase downtime and production losses.

    The high O&M cost at OWFs creates a necessity to better analyze the situation in OWF maintenance and the associated uncertainties, identify maintenance problems, and come up with cost-effective solutions. This thesis aims to model the uncertainties in OWF maintenance and their effects on O&M costs, and identify critical maintenance decision problems and propose solutions for the identified problems through decision models considering uncertainties.

    Firstly, an O&M model for the next future trip to the OWF is proposed to study the seasonal effects of the uncertainties on the O&M costs of OWFs. The proposed O&M model is a function of stochastic time elements of maintenance. Using the proposed model, the seasonal variations of offshore O&M costs, considering uncertainties are obtained. The results show that the O&M costs are lower in summer and higher in winter. Secondly, a resource decision problem for corrective maintenance of OWT, considering uncertainty in turbine failure information is studied. The problem situation is described, and a decision model is proposed to find a cost-effective resource option to address the described problem. Also, the use of the proposed model is demonstrated through a case study. The results of the case study show that the proposed model is mainly dependent on the probability of occurrence of different failure classifications of OWT. Finally, a decision problem related to maintenance technicians for corrective maintenance of OWT is studied. The uncertainty in maintenance technicians for OWF maintenance is modeled, and a mathematical model is proposed to find the appropriate/optimal number of technicians to send for corrective maintenance of OWT. A simple case study demonstrates the use of the mathematical model and figures out the appropriate number of technicians to send for two corrective maintenance categories.

    This thesis study would promote the state of the art of research on OWF maintenance. The knowledge generated from this thesis will help the offshore O&M team better plan maintenance activities and make cost-effective resource decisions to reduce the overall O&M costs and the cost of energy of OWFs.

  • Subjects / Keywords
  • Graduation date
    Fall 2020
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
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