Charles Vaughan

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Maintenance Considerations for Improved Financial
Results
Charles Vaughan Clipper Windpower, Inc.
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Financial Sensitivity

• Maintenance costs versus Return
• Unscheduled maintenance
• Major factor in financial result degradation
• Early MW size turbines actual unscheduled
  maintenance costs are greater than expected
• Newer turbine models incorporate design
  improvements to address shortcomings and reduce
  maintenance costs

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Financial Sensitivity

• Impacts on Return Internal Rate of Return IRR
  from greater than expected unscheduled
  maintenance costs
• Large cost items Generator rebuild, Gearbox
  rebuild
• Costs for replacement component
• Large crane costs crane costs plus in / out
  costs
• Lost production cost- lead time to get crane
  mobilized to site and set up crane availability
  constraints

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Financial Sensitivity
Sensitivity Example 100 MW project

• Expected Return 9 after tax IRR
• Two cases for sensitivity analysis
• Impact on return
• Case 1- 2 generator 1 gearbox rebuilds on half
  the turbines spread over 20 years
• Case 2 - 2 generator 1 gearbox rebuilds on each
  of the turbines spread over 20 years

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Financial Sensitivity

• Assumptions k
• Crane in / out and use 225
• Generator rebuild 25
• Gearbox rebuild 100
• Crane lead time 3 months
• loose 25 year revenue for each event

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Financial Sensitivity

• Return Impacts from expected 9 AT IRR
• Case 1 2 generators 1 gearbox half the
  turbines
• IRR from 9 to 7.6, reduction of 16 on IRR,
• 62 mm nominal loss of value
• Case 2 2 generators 1 gearbox all turbines
• IRR from 9 to 6, reduction of 33 on IRR
• 124 mm nominal loss of value

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Financial Sensitivity

• Return impacts are substantial, and unforeseen
• Unexpected bad news - best to avoid
• Design Improvements can mitigate unscheduled
  maintenance costs

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Design Improvements - Key Areas
Electrical ArchitectureGearbox
ArchitectureDesign for ServicePredictive
MaintenanceHuman Factors
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Electrical Architecture

• Variable Speed Constant Frequency operation
• Required for MW size turbines
• Electronically control torque loads
• Allow larger rotor for given drive train and its
  cost

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Electrical Architecture

• Double Fed Generator Configuration
• Variable frequency current fed into rotor of
  generator
• Produce 60 Hz output with variable input speed
• 1990s technology
• Limited by solid state switches at the time
• Unintended Consequence - result
• Stray current in generator rotor occurs
• Stray current goes to ground
• Arc across generator bearings
• Generator will fail
• Requires generator removal and rebuild
• Lost revenue and repair costs impact return

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Electrical Architecture

• New turbine models design out the problem
• Permanent Magnet Generator
• No slip rings, couplings or brushes
• Air cooled operates more than 40 C below
  insulation specification
• Very compact 3.5' x 3.0'
• Does not require coupling between the gearbox
  and the generators because of low short-circuit
  current
• Higher efficiencies in all operational loads
  than commercial doubly fed or wound field
  synchronous
• Totally enclosed TEWAC, for contamination
  applications
• An IP54 air-cooled option for less demanding
  application
• Low weight lt 4000 Lbs. each. Can be handled by
  on-board gantry crane

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Electrical Architecture

• Permanent magnet generator
• No current in the rotor, no slip rings, no arcing
  damage
• Simple design, more reliable

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Electrical Architecture

• New turbine models design out the problem
• Full conversion configuration
• Simpler controller / converter design
• Todays solid state components versus mid 1990s
• Faster, better, more reliable
• Fewer parts to maintain and or fail
• Slip rings
• Couplings

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Gearbox Architecture

• Purpose designed for wind turbine configuration
• Versus modifications of speed reduction gearboxes
• Distributed load path gearbox design
• Split load path to reduce strain on gears
• Multiple load paths multiple out put paths
• Simpler design
• Input is a single gear, not need planetary gear
  configuration

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Gearbox Architecture

• Input is a single gear

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Gearbox Architecture

• Distributed load path configuration
• Multiple output paths
• Allows multiple smaller generators
• Potential generator replacement without the lead
  time delay and cost of the external crane
• Reduced maintenance costs
• Improved Return and certainty

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Gearbox Architecture

• Distributed Load Path
• Distributed Generators

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Design For Service

• Generator, rotor, bearings, high speed gears easy
  to remove

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Design For Service

• On Board Service Crane
• Replace components
• No external crane
• Less downtime
• Save Time Cost

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Design For Service

• On Board Service Crane
• Component replacement without in/out cost of
  external crane
• Generators- added benefit of multiple smaller
  generators
• Pitch gears and motors
• Gearbox high speed gears sets
• Yaw gears and motors
• Hydraulic, electrical, cooling components
• No added costs of external crane, no lost revenue
  due to crane lead time

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Design For Service

• Rotor hub access
• Technicians climb inside versus outside the hub
• Inside access likely results in more and better
  attention to hub
• Pitch bearings
• Pitch gears and motor actuators
• Electrical controls and energy storage systems
• Better maintenance likely results in less cost
  and more Return

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Predictive Maintenance

• Predict when maintenance or repairs are needed
• Detect and make repairs before more costly or
  catastrophic failure
• Repair cost much less
• Save cost of non required maintenance procedures
• Oil change if and when needed
• Not later, not sooner
• Schedule repair down time for greater efficiency
  and reduced costs
• Stage equipment and supplies, use low wind
  periods
• Less maintenance cost more and predictable
  Return

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Predictive Maintenance

• Sensors and data recording required
• Vibration
• Oil particle count
• Accelerometer
• Temperature
• Electrical parameters
• Data recording
• Analysis for prediction of maintenance
  requirements
• Basic trend monitoring and alarm functions
• More to learn, upside potential
• Visual inspection ports for gears picture worth
  thousand words

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Human Factors

• Tower climbing versus service lift
• Tower climb like a 20 story building, up a ladder
  
• Turbine technician career time limited physical
  strain
• Results in a young male work force

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Human Factors

• Service lift configuration
• Physical climbing not required
• Technicians can have a long career
• Benefit of experienced technicians
• See and hear problem earlier
• Perhaps more or better attention to turbine
• Reduced injury costs long term

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Human Factors

• Design for better, easier service
• Room around components
• Work space
• Likely more and better service attention
• Less costs, less downtime

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Financial Performance as a Function of
Maintenance

• Reducing costs improves Return
• Reducing uncertainty of costs reduces Risk
• Improves the Risk / Return balance
• New turbine designs will improve Return
• Historic unscheduled maintenance cost factors
  designed out
• Generator circulating current failures designed
  out
• Gearbox loads reduced- lower loads- greater
  reliability
• Predictive maintenance will reduce uncertainty
• Less uncertainty- less Risk
• Better Return

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Financial Performance as a Function of
Maintenance

• Newer turbines will provide improved Risk /
  Return results
• By experienced based Design advances
• By maintenance practices with more electronic
  intelligence
• By improved Human Factors

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Maintenance Considerations for Improved Financial
Results
Charles Vaughan Clipper Windpower, Inc.