Wind turbines as we know it are becoming larger and the blades are growing to new lengths to harness the power.
Most of today’s modern onshore turbines have typically 60 meters long blades, providing a rotor of 120+ meters. With longer blades follow increased tip speed. Often more than 250-300 kilometers per hour (80-100 m/s). Such speeds increase leading edge erosion on the blades as rain, hail, and other airborne particles expose the surface to extreme wear and tear when the turbine is spinning day in and day out. This issue affects the blade's longevity and significantly impacts the turbine's annual energy production (AEP) resulting in increased maintenance cost. In the offshore wind industry leading edge erosion (LEE) is a widely recognized issue and leading edge protection (LEP) solutions are seen as industry standard.
As the search for optimal onshore wind sites pushes turbines into more remote locations, they often encounter challenging weather conditions. With increased rainfall, these sites naturally pose a greater risk of erosion to the turbine blades. In other words, the offshore problem is going onshore.
AEP Loss: The Greater Picture
When discussing the ramifications of leading edge erosion, it is vital to understand its effect on AEP. When pristine and straight from the factory, a blade's leading edge offers optimal aerodynamic performance, ensuring maximum energy capture. However, as erosion takes hold, the surface roughens, disrupting the airflow and decreasing efficiency.
LEP systems might introduce minor performance deviations compared to a brand-new blade. Yet, this slight reduction pales compared to the potential AEP loss over a turbine's lifetime if left unprotected. While an LEP might reduce AEP by a small fraction, untreated leading edge erosion can lead to significant reductions in AEP.
Comparing leading edge protection methods
Given the clear need to address this issue, the industry has explored several solutions:
- Paints: Protective LEP paints are a straightforward solution. Limitations are similar to coating, so with today’s tip speed, paint is no longer sufficient over the lifetime of a wind turbine.
- Coatings: Specialized coatings, often made from polyurethane or epoxy, provide a protective layer against the elements. While they offer protection, they might require re-application over time due to wear, especially on today’s wind turbines where tip speed is significantly higher than five to ten years ago.
- Tapes: Protective tapes, typically made of polyurethane or polymer, are applied to the blade's leading edge. They are replaceable, making maintenance easier, and often provide resistance to erosion. Some solutions require several replacements during the lifetime of the wind turbine.
- Shells: Some are hardcovers. is a softshell fitted over the blade's leading edge. While they offer robust protection, they can be more complex to install. Some solutions might impact the blade's aerodynamics more than others.
Erosion calculations comparing Polytech’s ELLE™ Onshore solution with standard coating and conventional LEP tape available on the market. The example represents an onshore site in US. Calculations show that conventional coating will start eroding instantly, leading to min. 3 meters of wear and tear, and should be repaired annually during the lifetime of the wind farm. Conventional tape LEP needs to be repaired 3 times during its lifetime, whereas Polytech’s ELLE™ Onshore will last +15 years.
Conclusion
Leading edge erosion is an undeniable challenge for the onshore and offshore wind energy sector. While protection methods might introduce minor efficiency reductions, they are a necessary trade-off when considering the AEP losses that unchecked erosion can introduce over a turbine's lifespan.
As the industry grows, continued research and innovation in protection methods will be pivotal in ensuring wind energy remains efficient, reliable, and cost-effective. With the right solution you as owners will have the most optimal AEP over the turbine lifetime.