Wind turbine coating protects more than 2000 wind turbines in Australia
Australia has one of the best location for onshore wind farms in the world; the wind resources are just perfect in the Southeast, South and Southwest of the country. Currently there are more than 2000 wind turbines in Australia, generating almost 5% of the country’s total energy production with the largest wind farm being the Macarthur Wind Farm in Victoria; it has a capacity of 420 MW. The number of wind farms and turbines is ever growing; therefore, it is of vital importance that such valuable assets are protected appropriately. Wind turbine coating protects against the erosion and corrosion of the structure due to the harsh environmental conditions they face every day. It increases the wind turbine’s strength, lifespan, reliability, and durability as well as reducing the need for costly maintenance.
In this article we take a look at the coatings for wind turbines both onshore and offshore, and the companies and their products on the Australian market.
How wind turbine coatings protect the resource
Wind turbines harness the energy of the wind to create electricity. This means that they need to be built in places where wind is abundant, strong, and enduring. The windiest places on earth are also some of the most inhospitable and harshest environments. Wind turbine coatings need to work against the challenges wrought by the combination of environment and use. The right wind turbine coating provides protection from the three most threatening hazards faced by the windmills being:
Leading edge erosion
The front edge of a wind turbine blade is subject to constant impact from airborne projectiles such as rain, ice, salt, or sand. The blade tip on a large turbine can reach speeds of 80 m/s as it rotates, and pitting, delamination, and cosmetic failures form, compromising the blade’s integrity and developing into total blade failure. This ‘leading edge erosion’ is one of the biggest issues challenging wind turbine coatings.
High maintenance costs
Damage from rain and sand can reduce a turbine’s energy output by 20% a year. A turbine may be in continuous operation for 15 years and the coatings need to provide around the clock protection. The scale and location of these structures makes maintenance and accessibility a highly expensive task. The best wind power coatings aim to be maintenance free for their lifetime.
In the highly corrosive environments necessary for the most effective wind turbines, corrosion is a big problem. Sub-sea structures, splash zones, and the salt spray in the wind itself all present difficulties for the stability and strength of a wind turbine. The wind turbine coatings need to provide the highest degree of corrosion protection.
Wind turbine coating types and application for complete protection
Both onshore and offshore wind turbines need coatings to ensure their optimum performance for their service life with the minimum of maintenance. Wind turbine coatings are applied to components including blades, towers, nacelles, foundations, and equipment. Like any coating the environmental conditions, service life, required durability, use, and substrate all need to be carefully chosen for to ensure the best outcome and performance. To that end, there are a variety of coating technologies available for the protection of wind turbines:
1. Polymer coatings
Epoxy, acrylic, polyurethane and fluoropolymer high performance coatings
These coatings are applied either in a factory or in situ, depending on the relevant restrictions. Polymer coatings are chosen for their high performance properties: corrosion resistance, durability, chemical resistance, smooth finish, and toughness. Fluoropolymers have the added benefit of dirt resistance and to combat biofouling at the turbine base.
Polymer coatings are commonly applied as layered systems, rather than single coats. In this way the different properties of the coatings can protect other layers as well as the turbine, strengthening the protective system. Recent developments in the wind turbine coating industry include paint systems requiring fewer layers in order to reduce production time and cost. A common 3-coat system will use epoxy as the base coats and polyurethane as the top coat, using polyurethane’s UV resistance to protect the less-resistant epoxy.
2. Metal coatings
Zinc rich epoxy coating, zinc and aluminium through thermal spraying, galvanising, electroplating and diffusion
Metal coatings are a crucial part of coating wind turbines; it can be applied on any metal surface from large structural pieces to the tiniest components.
In particularly corrosive environments (C5-M zones), a duplex system is often used to protect turbines. A duplex system is the combination of a metal coating base layer and a polymer paint system, commonly used for offshore wind turbines. Even if the polymer coating fails or is damaged, the structure is still protected by the metal coating through both galvanic and barrier action. The duplex system is considered the toughest for offshore conditions.
3. Ceramic coatings
Inorganic coatings such as aluminium oxide, aluminium titania, chromium oxide, and more
Protection of the structure of the wind turbine is vitally important, but the mechanisms also need protection from corrosion and from the wear of constant use. Rotating machinery such as bearings needs coating to increase their lifetime while decreasing maintenance costs. These coatings are hard, low friction, abrasion and wear resistant, anti-galling, corrosion resistant, heat resistant, and durable.
Ceramic coatings are also finding applications with the blades of wind turbines. This is in part because ceramic coatings have a greater abrasion resistance than polymer coatings, an important factor in combating leading edge erosion and preventing the constant impact of projectiles from damaging the blade.
Coating rotor blades with wind power coatings
Wind turbine blades are made from aluminium, wood, or a fibreglass-resin composite (for those blades too large for wood or aluminium). Coatings can be applied with spray, roll or brush to rotor blades made from aluminium and wood, but there are two different methods for coating a fibreglass-resin composite blade: in-mould and post-mould application. A moulded rotor blade is formed as two separately moulded halves, which are then joined. In this process the wind turbine coatings can be applied in two phases:
- In mould coatings – when the mould is produced with a polyurethane gelcoat.
This type of coating contributes to the overall quality of the blade and makes the unfinished blades easier to handle than a fibreglass surface. The in-mould coatings are usually epoxy or polyurethane based and the application is time and cost efficient.
- Post-mould coatings – applying the coating after the blade has been formed.
These coatings focus on protecting the lead edge from erosion and they are often epoxy or polyurethane based and follow the order of a regular 3 coat system (polyurethane is the top coat).
Find wind turbine coatings in Australia
The growth of the wind energy sector has seen a corresponding rise in the number of coating companies catering to wind turbine coatings. The industry is currently dominated by a few big companies, with many smaller companies jockeying for position. The top players are AkzoNobel, Hempel, PPG, Jotun, Aeolus, Teknos, and Sherwin-Williams. Hempel coatings protect some 50% of the onshore and offshore towers around the globe. Here below you can find a selection of wind turbine coating products by the top manufacturers, also available in Australia.
If you would like advice about wind turbine coatings, or are looking for a coating for your project, get in touch! Our experts are here to help. In cooperation with our coating partners, we will connect you with the coating solution for your needs.
|Coating Company/Brand||Wind Turbine Coating Product||Product Description|
|AkzoNobel||Intershield 300||A two component, abrasion resistant aluminium-pigmented pure epoxy coating providing excellent long term anticorrosive protection for offshore structures.|
|Hempel||Hempadur Avantguard 750||A two-component, activated zinc epoxy primer for long-term protection of steel in severely corrosive environments.|
|Jotun||Jotamastic 87||A two component epoxy-mastic for repair and maintenance. Anticorrosive coating for a range of substrates.|
|PPG Industries||Selemix||A polyurethane topcoat for turbine blades to protect from erosion.|