Leading Edge Erosion (LEE) is a serious and very expensive issue in the wind industry, with all Wind Turbine Generator (WTG) blades suffering from LEE and its effects are exaggerated on offshore turbines.
LEE is caused by repeated bombardment, primarily by raindrops and particulate matter, hail, ice, salt and UV, which create erosion and cause surface roughness. Ever larger rotor blades have resulted in increasing rotation speeds of the blade tips. The tips of offshore wind turbine blades can exceed 330 km/h. At these speeds, raindrops and hailstones create multiple shock wave impacts on the blade surface, which damage the blade surface or any Leading Edge Protection (LEP), including the adhesive bond that secures the LEP to the blade surface. Ultimately, rain and particulate bombardment can erode the surface coating and LEP layers, and eventually expose the blade laminate. The tip sections and leading edges (LE) of the blades are worst affected. The surface roughness that results from this erosion process creates resistance and drag, which impairs the aerodynamic performance of a blade; the air flow, lift and drag, reducing WTG efficiency and therefore decreasing the generating capacity of a windfarm, which consequently reduces Annual Energy Production (AEP) and therefore Return on Investment (ROI).
In order to operate blades at acceptable performance levels the LE surface must be aerodynamically optimal, therefore any surface roughness caused by LEE must be repaired and cost effectively protected from further LEE damage. This creates significant operational and maintenance challenges for all wind farm operators but is exaggerated for offshore wind.
LEE also risks adversely impacting the structural integrity of operational blades as water ingress and UV light exposure can result in structural damage. If LEE is not rectified & LEP applied before damage increases it will require ever more invasive composite repairs. Ultimately this process will require blade replacement, which can be prohibitively cost effective to ROI.
LEE proves costly for offshore windfarm owner/operators through increased Operational Expenditure (OpEx), lost AEP and reduced revenue at a time when Europe has seen the first zero-subsidy offshore wind farm auction bids and the need for cost reductions has never been higher.
LEP solutions (paints, tapes, coatings, etc.) are intended to protect WTG blades from LEE, which typically occurs on new offshore blades within 1-2yrs, and onshore within 3-5yrs dependent on location, environmental factors, topography and turbulence, etc.
WTG asset life is typically 20-25yrs but most LEPs don’t last more than 3-5yrs before the LE must be repaired & LEP replaced; offshore, commonly used LEPs can last as little as 2yrs.