Offshore wind turbines are subjected to extreme conditions, which can lead to serious corrosion problems. Protection against corrosion is, therefore, critical.
Due to the aggressive nature of marine corrosion, the technical challenges are far greater than with similar onshore projects.
Being constantly exposed to all kinds of demanding climatic conditions, with greater risks of structural corrosion, means that offshore wind turbines have major technical requirements. Access during bad weather also creates its own set of problems. These challenges are reflected in the high cost of offshore maintenance and the expense of replacing larger main components. It is extremely important, therefore, to reduce maintenance and service requirements with increased corrosion protection, together with an improved supervision and control system.
Wind turbine blades are made of composite materials that are inherently resistant to corrosion from seawater. As we have seen from other industries, however, long-term exposure to water or humidity degrades the properties of glass fibre reinforced composite. It is well known that boron-free glass such as Advantex® and HiPer-tex™ perform much better in these extreme environments compared with traditional E-Glass. For wind turbine blades exposed to harsh conditions, Advantex® and HiPer-tex™ represent today’s best-in-class glass fibre reinforcements for composite materials.
Field data comparing the acid resistance of Advantex® glass to that of traditional E-Glass confirm that Advantex® provides substantially better resistance to the sustained corrosive effects of acidic environments. Advantex® glass fibre is also performance-proven through the long-term exposure to all aqueous environments, including water and seawater. This translates into many benefits for the customer over traditional E-Glass. These include, longer service life and larger safety coefficients for the same design, especially for challenging offshore environmental conditions.
|Environment||Glass Reinforcement||% of initial static strength* for 50 years lifetime||Max Stress (MPa) to reach 50 years lifetime|
|2007 studies||1997 studies||HiPer-tex™ vs Advantex®||Advantex® vs E-Glass||HiPer-tex™ vs Advantex®||Advantex® vs E-Glass||HiPer-tex™ vs E-Glass|
|5% Salt Water||HiPer-tex™||46.2%||669||24%||96%|
Initial Tensile strength of pultruded rod: 1100MPa, Avg glass weight fraction: 75%
The table above summarises the stress corrosion test of pultruded rods made with the same isophtalic polyester resin and three different glasses: E-Glass, Advantex® and HiPer-tex™.
Outstanding mechanical properties
With its ability to achieve longer blade lengths, HiPer-tex™ is the solution for multi megawatt designs required for offshore blades.
When compared to traditional E-Glass, the benefits of HiPer-tex™ fibre are clear:
• Up to 30% higher tensile strength
• Up to 17% higher tensile modulus
• Up to 40% increase in fatigue strength
• Blade weight savings of up to 10% versus conventional E-Glass blades of the same design
• 10 times longer lifetime in fatigue
As a result, these benefits allow turbine manufacturers to increase blade lengths, while keeping the same blade weight for higher turbine efficiency – leading to a lower cost per kWh