Offshore Wind Farms failures, maintenance plan and constraints

Offshore Wind Farms failures, maintenance plan and constraints

Offshore Wind farms (OWF) The OWF is expected to be the major source of energy [Reh 2014] European countries are leader (117GW) OWF negative and positive aspects are presented in [Synder 2009] higher wind speeds; smoother, less turbulent airflows; larger amounts of open space; and the ability to build larger, more cost-effective turbines (6MW) Cost of installation of offshore turbines is more important than onshore Cost of maintenance is very important in OWF Middelgrunden wind farm outside of Copenhagen, Denmark. Image obtained with thanks from Kim Hansen on Wikipedia 3

Offshore Wind farms (OWF) Example DOWEC wind farm 80 turbines, 6MW each => 480MW North sea at the location NL7, 50 Km offshore [Lindenburg 2003] Equipped with 50MT mobile crane In each nacelle there is 1MT crane A supplier with an Offshore Access System is used to transport personal and small components [Radermarkrs] [DOWEC 2003] 4

Energy (GW) Development of OWF [Reh 2014] 5

Development of OWF Annual onshore and offshore installation [EWEA 2014] EUROPEAN WIND ENERGY ASSOCIATION 6

Development of OWF Onshore historical growth 1994 2004 compared to EWEA'S offshore projection 2010 2020 [Reh 2014] 7

Failure of OWF 60% of the failures are contained in the following ones: [chun 2012] Electrical equipment Yaw system Gearbox Rotor Hydraulic system Primary Components and Dimensions of One of the 2-MW Turbines in Denmark s Horns Rev Offshore Wind Park [USA 20006] 8

Failure of OWF Failure rate l is the frequency with which an engineered system or component fails It is dynamic (not determinative) because it depending of the maintenance actions Different consequences of the failures The failure mode determine what type of actions is required and thus define the cost. Failure rate of Danish wind turbine components [chun 2012] [Hyers 2006] 9

Failure of OWF country Sweden Finland Germany Average number of failures per turbine Average downtime per failure Longest downtime per failure Variation of failure nature by country ( position, policy; ) Each wind farm has its own failure behavior 0.402 times/year 1,38 times/year 2,38 times/year 170 h/year 172 H/year 62,2 h/year drive train Gears Generators [Kawady 2008] 10

Failure mode and failure cause Resonances within resistor-capacitor (RC) circuits Poor electrical installation Technical defects Lightning Poor component quality and system abuse Poor system design Production defects Turbulent wind Out-of-control rotation Icing problem in extreme weather High vibration level during overload Frequent stoppage and starting Particle contaminations High loaded operation conditions Improper installation (60%) High/Low temperature Corrosion Vibration Electrical Control Blade Failures Yaw System Gearbox Hydraulic Generator windings, Short-circuit Over voltage of electronics components Transformers Wiring damages Damages Cracks Breakups Bends Cracking of yaw drive shafts, Fracture of gear teeth, Pitting of the yaw bearing race Failure of the bearing mounting bolts Wearing, Backlash, Tooth breakage Leakages Weather Human Technical 11

Maintenance cost and availability Cost of maintenance Generator gearbox Blade Electrical system Control Shaft & bearing Yaw system pitch mechanism invertor parking brake brake Downtime Generator gearbox Blade Electrical system Control Shaft & bearing Yaw system pitch mechanism invertor parking brake brake Relative contribution of the components to the costs and downtime (Netherlands)[Radermarks ] Cost of maintenance sensors gear mechanical breakes hydrolics yew system structure Entire unit Hub Blades/pitch generator electric system Control system Drive train Downtime sensors gear mechanical breakes hydrolics yew system structure Entire unit Hub Blades/pitch generator electric system Control system Drive train Distribution of failures in the Swedish wind power plants (1997-2005) [Kawady 2008] 12

Maintenance cost Preventive Maintenance (PM) 0.003 to 0.006( /kwh) Corrective Maintenance (CM) 0.005 to 0.01 ( /kwh) The contribution of maintenance cost in the price is 25 to 30% [Europ 2001]. Size and reliability of the turbine Maintenance concept OWF position Weather Conditions Maintenance plan/ cost [Radermakrs] 13

Maintenance cost Size and reliability of the turbine Large turbines optimized for offshore applications Adapted storage equipment Size and reliability of the turbine Maintenan ce concept Maintenance cost OWF position Weather conditions Maintenance concept Maintenance strategy Maintenance actions management Types of maintenance OWF position Water depth Size of wind farm The travel duration 14

Maintenance cost [Radermkers] The weather Conditions Size and reliability of the turbine Each repair equipment has its own maximum condition of use : Example : The OAS (Offshore Access System) is assumed to operate up to waves_high_max (Hs_Max)=2m and wind_speed_max(vs_max)= 12 m/s for transporting personals and 1.5 m and 8m/s for spare parts. The time series of wave and wind data to define : The waiting time as a function of the duration of the repair, Hs_max and Vs_max; The damages caused by lightning Visibility Maintenan ce concept Maintenance cost OWF position Weather conditions 15

Required data (input) Location and characteristics of wind farms Failure rates Expected time-to-failures Preventive maintenance (historical data or model) Repair strategies Wind and wave statistics Costs Lead time of vessels and spare parts 16

Actions for optimization Improvement of maintenance strategy Reduction of failure rate including redundancy Fault tolerance operation Improvement of collaboration mode (ICT, MAS, ) Improvement of accessibility Improve the design of turbine to be more robust with less maintenance requirement and actions 17

References [BOEM2013] http://www.boem.gov/renewable-energy-program/renewable-energy-guide/offshore-wind-energy.aspx [Pieterman 2011] Braam, H. & Obdam, T.S., 2011. Optimisation of maintenance strategies for offshore wind farms., (December), pp.1 12. [Radermakrs] Braam, H., Zaaijer, M.B. & Energy, S.W., ASSESSMENT AND OPTIMISATION OF OPERATION AND MAINTENANCE OF OFFSHORE WIND TURBINES. [Lindenburg 2003] Lindenburg, C., Winkelaar, D. & Hooft, E.L. Van Der, 2003. Dowec 6 mw pre-design., (September), pp.1 46. [Péres 2010] Morant, F., Correcher, A. & Quiles, E., 2010. Optimal maintenance system for offshore wind turbines -., (Table I). [Chun 2012] Pecht, M., 2012. Review of offshore wind turbine failures and fault prognostic methods. Proceedings of the IEEE 2012 Prognostics and System Health Management Conference (PHM-2012 Beijing), pp.1 5. Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6228954. [Reh 2014] Perveen, R., Kishor, N. & Mohanty, S.R., 2014. Off-shore wind farm development: Present status and challenges. Renewable and Sustainable Energy Reviews, 29, pp.780 792. Available at: http://linkinghub.elsevier.com/retrieve/pii/s1364032113006849 [Accessed February 20, 2014]. [Europ 2001] G.Hassan, 2001. Concerted Action on Offshore Wind Energy in Europe [Snyder 2009] Snyder, B. & Kaiser, M.J., 2009. Ecological and economic cost-benefit analysis of offshore wind energy. Renewable Energy, 34(6), pp.1567 1578. Available at: http://linkinghub.elsevier.com/retrieve/pii/s0960148108004217 [Accessed February 19, 2014] [EWEA 2014]Anon, 2014. Wind in power 2013., (February), pp.1 12. [Kawady 2008] Kawady, T.A. et al., 2008. Wind Farm Protection Systems: State of the Art and Challenges., 2008. [USA 2006] Anon, 2006. Wind Energy Potential on the U.S. Outer Continental Shelf., (May). 18

Questions 19