O&M cost modelling of large component major replacement in next-generation offshore wind turbines with uncertain failure rates

Rights statement
Awarding institution
  • University of Strathclyde
Date of award
  • 2022
Thesis identifier
  • T16500
Person Identifier (Local)
  • 201867545
Qualification Level
Qualification Name
Department, School or Faculty
  • The costs associated with the maintenance of next-generation offshore wind turbines are a source of uncertainty to developers, in particular due to the unknown replacement rate of large components. This is particularly true for floating turbines, with accessibility impacted by wave-induced turbine and vessel motion. This thesis addresses the impact that the currently unknown major replacement rate of turbine components may have on the maintenance cost of large, offshore wind farms and how this varies between fixed and floating wind farms when using 15MW direct-drive or medium-speed wind turbines. Application of the Classical Model of structured expert elicitation with six wind energy experts found that the expected overall rate of major replacement tasks for 15MW next generation offshore turbines is lower than those reported for first-generation turbines. Medium-speed turbines are expected to have higher overall major replacement rates than direct-drive turbines. Floating configurations are expected to have higher overall major replacement rates than fixed-foundation turbines, ranging from 7.9% to 112.5% higher depending on the scenario and weighting method applied. Cost modelling of 18 fixed and 18 floating wind farm scenarios using the StrathclydeOW O&M model amended for floating wind scenarios found a wide range of lifetime costs associated with major replacement tasks over the estimated uncertainty ranges of major replacement rates. Fixed-foundation medium-speed turbines achieved lower lifetime major replacement costs than direct-drive turbines. Combined mean repair and vessel costs ranged from £5.6k-£33.4k/MW.yr compared to £6.5k-£34.5k/MW.yr. The cost of major component replacement for floating turbines increased due to higher replacement rates and additional wave limits. Combined mean repair and vessel costs ranged from £14.0k £69.6k/MW.yr for medium-speed turbines and £17.6k-£88.0k/MW.yr for direct-drive turbines. These findings can inform future wind farm costing and suggest that floating wind farms are likely to have higher and more variable maintenance costs than fixed wind farms.
Advisor / supervisor
  • Carroll, James
  • McMillan, David
Resource Type