Wind O&M - Topical Outline 
     •  Utility-scale (1-3 MW)
         – O&M R & D
         – O&M Cost Trends
     •  Distributed-scale (1-1500 kW)
         – O&M Cost Trends
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      Utility-scale  -  O&M - Type of Costs 
      •  Annual Fixed Costs
           – Scheduled maintenance  
               • Oil & lubricants 
               • Sensor evaluation
           – Condition Monitoring
           – Leasing
           – Taxes
           – Insurance
      •  Annual Variable Costs
           – Unscheduled maintenance
               • Worn out parts
               • Catastrophic failures
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      Utility-scale  -  O&M Costs
      Generally, the annual costs increase over the life of the turbine – 
         especially in later years of 20-25 year useful life
      There are industry recommended practices for all aspects of 
         wind turbine maintenance:
      Towers; rotors/blades/hubs; gearboxes; generators; balance of 
         plant; data collection/reporting; end of warranty
      O & M Costs expressed as:
          $/kW/yr (capacity-based)
            
          $/MWh/yr or $/kWh/yr (energy-based) 
            
          $/yr (simple)
            
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      Major Components at Risk
     Equipment breaks – usually after the warranty expires               Structural
                                               Gearbox Rebuild
                                                                      Blade Replacement
    t
    s      y
    o      t
    C      n
           a
    r      r
    i      r
    a      a
    p
    e      W
    R                                              Yaw Drive, Pitch Drive
                                                  Generator Bearings
                                Motors and Switchgear
                Control & Sensors
                    5                                               10                                           20 
       years
          Reference: Chris Walford: GEC (now DNV GL)
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     NREL Wind O&M Research & Development
      Source:  Report on Wind Turbine Subsystem Reliability – A Survey of Various Databases, Sheng, S. 2013:  
      NREL Publication Database: NREL/PR-5000-59111
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